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21 Nov 2018 at 01:41
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Bibliography on: Energetics and Mitochondrial Evolution


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RJR: Recommended Bibliography 21 Nov 2018 at 01:41 Created: 

Energetics and Mitochondrial Evolution

Mitochondria are the energy-producing "engines" that provide the power to drive eukaryotic cells. The energy output of hundreds, or thousands, of mitochondria allowed eukaryotic cells to increase in size 1000-fold, or more, over the size of prokaryotics cells. This increase in size allowed an escape from the constraints of low Reynolds numbers and, for the first time, life could function in a way where mechanism, and thus morphology, mattered. Evolution began to shape morphology, allowing the emergence of the multicellular eukaryotic biosphere — the visible living world.

Created with PubMed® Query: mitochondria AND evolution AND (energetics OR "energy metabolism") NOT pmcbook NOT ispreviousversion

Citations The Papers (from PubMed®)

RevDate: 2018-10-30
CmpDate: 2018-10-30

Liu W, Hu C, Xie W, et al (2018)

The mitochondrial genome of red-necked phalarope Phalaropus lobatus (Charadriiformes: Scolopacidae) and phylogeny analysis among Scolopacidae.

Genes & genomics, 40(5):455-463.

The red-necked phalarope is a wonderful species with specific morphological characters and lifestyles. Mitochondrial genomes, encoding necessary proteins involved in the system of energy metabolism, are important for the evolution and adaption of species. In this study, we determined the complete mitogenome sequence of Phalaropus lobatus (Charadriiformes: Scolopacidae). The circular genome is 16714 bp in size, containing 13 PCGs, two ribosomal RNAs and 22 tRNAs and a high AT-rich control region. The AT skew and GC skew of major strand is positive and negative respectively. Most of PCGs are biased towards A-rich except ND1. A codon usage analysis shows that 3 start codons (ATG, GTG and ATA), 4 stop codons (TAA, TAG, AGG, AGA) and two incomplete terminate codons (T-). Twenty two transfer RNAs have the typical cloverleaf structure, and a total of ten base pairs are mismatched throughout the nine tRNA genes. The phylogenetic tree based on 13 PCGs and 2 rRNA genes indicates that monophyly of the family and genus Phalaropus is close to genus Xenus plus Tringa. The analysis of selective pressure shows 13 protein-coding genes are evolving under the purifying selection and P. lobatus is different from other Scolopacidae species on the selective pressure of gene ND4. This study helps us know the inherent mechanism of mitochondrial structure and natural selection.

RevDate: 2018-10-12

Pustylnikov S, Costabile F, Beghi S, et al (2018)

Targeting mitochondria in cancer: current concepts and immunotherapy approaches.

Translational research : the journal of laboratory and clinical medicine pii:S1931-5244(18)30114-2 [Epub ahead of print].

An essential advantage during eukaryotic cell evolution was the acquisition of a network of mitochondria as a source of energy for cell metabolism and contrary to conventional wisdom, functional mitochondria are essential for the cancer cell. Multiple aspects of mitochondrial biology beyond bioenergetics support transformation including mitochondrial biogenesis, fission and fusion dynamics, cell death susceptibility, oxidative stress regulation, metabolism, and signaling. In cancer, the metabolism of cells is reprogrammed for energy generation from oxidative phosphorylation to aerobic glycolysis and impacts cancer mitochondrial function. Furthermore cancer cells can also modulate energy metabolism within the cancer microenvironment including immune cells and induce "metabolic anergy" of antitumor immune response. Classical approaches targeting the mitochondria of cancer cells usually aim at inducing changing energy metabolism or directly affecting functions of mitochondrial antiapoptotic proteins but most of such approaches miss the required specificity of action and carry important side effects. Several types of cancers harbor somatic mitochondrial DNA mutations and specific immune response to mutated mitochondrial proteins has been observed. An attractive alternative way to target the mitochondria in cancer cells is the induction of an adaptive immune response against mutated mitochondrial proteins. Here, we review the cancer cell-intrinsic and cell-extrinsic mechanisms through which mitochondria influence all steps of oncogenesis, with a focus on the therapeutic potential of targeting mitochondrial DNA mutations or Tumor Associated Mitochondria Antigens using the immune system.

RevDate: 2018-08-26
CmpDate: 2018-08-24

Bilz NC, Jahn K, Lorenz M, et al (2018)

Rubella Viruses Shift Cellular Bioenergetics to a More Oxidative and Glycolytic Phenotype with a Strain-Specific Requirement for Glutamine.

Journal of virology, 92(17): pii:JVI.00934-18.

The flexible regulation of cellular metabolic pathways enables cellular adaptation to changes in energy demand under conditions of stress such as posed by a virus infection. To analyze such an impact on cellular metabolism, rubella virus (RV) was used in this study. RV replication under selected substrate supplementation with glucose, pyruvate, and glutamine as essential nutrients for mammalian cells revealed its requirement for glutamine. The assessment of the mitochondrial respiratory (based on the oxygen consumption rate) and glycolytic (based on the extracellular acidification rate) rate and capacity by respective stress tests through Seahorse technology enabled determination of the bioenergetic phenotype of RV-infected cells. Irrespective of the cellular metabolic background, RV infection induced a shift of the bioenergetic state of epithelial cells (Vero and A549) and human umbilical vein endothelial cells to a higher oxidative and glycolytic level. Interestingly there was a RV strain-specific, but genotype-independent demand for glutamine to induce a significant increase in metabolic activity. While glutaminolysis appeared to be rather negligible for RV replication, glutamine could serve as donor of its amide nitrogen in biosynthesis pathways for important metabolites. This study suggests that the capacity of RVs to induce metabolic alterations could evolve differently during natural infection. Thus, changes in cellular bioenergetics represent an important component of virus-host interactions and could complement our understanding of the viral preference for a distinct host cell population.IMPORTANCE RV pathologies, especially during embryonal development, could be connected with its impact on mitochondrial metabolism. With bioenergetic phenotyping we pursued a rather novel approach in virology. For the first time it was shown that a virus infection could shift the bioenergetics of its infected host cell to a higher energetic state. Notably, the capacity to induce such alterations varied among different RV isolates. Thus, our data add viral adaptation of cellular metabolic activity to its specific needs as a novel aspect to virus-host evolution. In addition, this study emphasizes the implementation of different viral strains in the study of virus-host interactions and the use of bioenergetic phenotyping of infected cells as a biomarker for virus-induced pathological alterations.

RevDate: 2018-09-21

Scott GR, Guo KH, NJ Dawson (2018)

The Mitochondrial Basis for Adaptive Variation in Aerobic Performance in High-Altitude Deer Mice.

Integrative and comparative biology, 58(3):506-518.

Mitochondria play a central role in aerobic performance. Studies aimed at elucidating how evolved variation in mitochondrial physiology contributes to adaptive variation in aerobic performance can therefore provide a unique and powerful lens to understanding the evolution of complex physiological traits. Here, we review our ongoing work on the importance of changes in mitochondrial quantity and quality to adaptive variation in aerobic performance in high-altitude deer mice. Whole-organism aerobic capacity in hypoxia (VO2max) increases in response to hypoxia acclimation in this species, but high-altitude populations have evolved consistently greater VO2max than populations from low altitude. The evolved increase in VO2max in highlanders is associated with an evolved increase in the respiratory capacity of the gastrocnemius muscle. This appears to result from highlanders having more mitochondria in this tissue, attributed to a higher proportional abundance of oxidative fiber-types and a greater mitochondrial volume density within oxidative fibers. The latter is primarily caused by an over-abundance of subsarcolemmal mitochondria in high-altitude mice, which is likely advantageous for mitochondrial O2 supply because more mitochondria are situated adjacent to the cell membrane and close to capillaries. Evolved changes in gastrocnemius phenotype appear to be underpinned by population differences in the expression of genes involved in energy metabolism, muscle development, and vascular development. Hypoxia acclimation has relatively little effect on respiratory capacity of the gastrocnemius, but it increases respiratory capacity of the diaphragm. However, the mechanisms responsible for this increase differ between populations: lowlanders appear to adjust mitochondrial quantity and quality (i.e., increases in citrate synthase [CS] activity, and mitochondrial respiration relative to CS activity) and they exhibit higher rates of mitochondrial release of reactive oxygen species, whereas highlanders only increase mitochondrial quantity in response to hypoxia acclimation. In contrast to the variation in skeletal muscles, the respiratory capacity of cardiac muscle does not appear to be affected by hypoxia acclimation and varies little between populations. Therefore, evolved changes in mitochondrial quantity and quality make important tissue-specific contributions to adaptive variation in aerobic performance in high-altitude deer mice.

RevDate: 2018-10-04

van der Hoek MD, Madsen O, Keijer J, et al (2018)

Evolutionary analysis of the carnitine- and choline acyltransferases suggests distinct evolution of CPT2 versus CPT1 and related variants.

Biochimica et biophysica acta. Molecular and cell biology of lipids, 1863(8):909-918.

Carnitine/choline acyltransferases play diverse roles in energy metabolism and neuronal signalling. Our knowledge of their evolutionary relationships, important for functional understanding, is incomplete. Therefore, we aimed to determine the evolutionary relationships of these eukaryotic transferases. We performed extensive phylogenetic and intron position analyses. We found that mammalian intramitochondrial CPT2 is most closely related to cytosolic yeast carnitine transferases (Sc-YAT1 and 2), whereas the other members of the family are related to intraorganellar yeast Sc-CAT2. Therefore, the cytosolically active CPT1 more closely resembles intramitochondrial ancestors than CPT2. The choline acetyltransferase is closely related to carnitine acetyltransferase and shows lower evolutionary rates than long chain acyltransferases. In the CPT1 family several duplications occurred during animal radiation, leading to the isoforms CPT1A, CPT1B and CPT1C. In addition, we found five CPT1-like genes in Caenorhabditis elegans that strongly group to the CPT1 family. The long branch leading to mammalian brain isoform CPT1C suggests that either strong positive or relaxed evolution has taken place on this node. The presented evolutionary delineation of carnitine/choline acyltransferases adds to current knowledge on their functions and provides tangible leads for further experimental research.

RevDate: 2018-08-27
CmpDate: 2018-08-27

Mansilla N, Racca S, Gras DE, et al (2018)

The Complexity of Mitochondrial Complex IV: An Update of Cytochrome c Oxidase Biogenesis in Plants.

International journal of molecular sciences, 19(3): pii:ijms19030662.

Mitochondrial respiration is an energy producing process that involves the coordinated action of several protein complexes embedded in the inner membrane to finally produce ATP. Complex IV or Cytochrome c Oxidase (COX) is the last electron acceptor of the respiratory chain, involved in the reduction of O₂ to H₂O. COX is a multimeric complex formed by multiple structural subunits encoded in two different genomes, prosthetic groups (heme a and heme a₃), and metallic centers (CuA and CuB). Tens of accessory proteins are required for mitochondrial RNA processing, synthesis and delivery of prosthetic groups and metallic centers, and for the final assembly of subunits to build a functional complex. In this review, we perform a comparative analysis of COX composition and biogenesis factors in yeast, mammals and plants. We also describe possible external and internal factors controlling the expression of structural proteins and assembly factors at the transcriptional and post-translational levels, and the effect of deficiencies in different steps of COX biogenesis to infer the role of COX in different aspects of plant development. We conclude that COX assembly in plants has conserved and specific features, probably due to the incorporation of a different set of subunits during evolution.

RevDate: 2018-04-04

Yu H, Wang D, Zou L, et al (2018)

Proteomic alterations of brain subcellular organelles caused by low-dose copper exposure: implication for Alzheimer's disease.

Archives of toxicology, 92(4):1363-1382.

Excessive copper intake can lead to neurotoxicity, but there is a lack of comprehensive understanding on the potential impact of copper exposure especially at a low-dose on brain. We used 3xTg-AD mice to explore the potential neurotoxicity of chronic, low-dose copper treatment (0.13 ppm copper chloride in drinking water) on behavior and the brain hippocampal mitochondrial and nuclear proteome. Low-dose copper increased the spatial memory impairment of these animals, increased accumulation of intracellular amyloid 1-42 (Aβ1-42), decreased ATP content, increased the positive staining of 8-hydroxyguanosine (8-OHdG), a marker of DNA oxidative damage, and caused apoptosis and a decrease in synaptic proteins. Mitochondrial proteomic analysis by two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) revealed modulation of 24 hippocampal mitochondrial proteins (14 increased and 10 decreased) in copper-treated vs. untreated 3xTg-AD mice. Nuclear proteomic analysis revealed 43 modulated hippocampal nuclear proteins (25 increased and 18 decreased) in copper-treated 3xTg-AD vs. untreated mice. Classification of modulated mitochondrial and nuclear proteins included functional categories such as energy metabolism, synaptic-related proteins, DNA damage and apoptosis-related proteins, and oxidative stress-related proteins. Among these differentially expressed mitochondrial and nuclear proteins, nine proteins were abnormally expressed in both hippocampus mitochondria and nuclei, including electron transport chain-related proteins NADH dehydrogenase 1 alpha subcomplex subunit 10 (NDUAA), cytochrome b-c1 complex subunit Rieske (UCRI), cytochrome c oxidase subunit 5B (COX5B), and ATP synthase subunit d (ATP5H), glycolytic-related pyruvate kinase PKM (KPYM) and pyruvate dehydrogenase E1 component subunit alpha (ODPA). Furthermore, we found coenzyme Q10 (CoQ10), an endogenous mitochondrial protective factor/antioxidant, modulated the expression of 12 differentially expressed hippocampal proteins (4 increased and 8 decreased), which could be classified in functional categories such as glycolysis and synaptic-related proteins, oxidative stress-related proteins, implying that CoQ10 improved synaptic function, suppress oxidative stress, and regulate glycolysis. For the proteomics study, we validated the expression of several proteins related to synapses, DNA and apoptosis. The data confirmed that synapsin-2, a synaptic-related protein, was significantly decreased in both mitochondria and nuclei of copper-exposed 3xTg-AD mice. In mitochondria, dynamin-1 (DYN1), an apoptosis-related proteins, was significantly decreased. In the cellular nuclei, paraspeckle protein 1 (PSPC1) and purin-rich element-binding protein alpha (Purα), two DNA damage-related proteins, were significantly decreased and increased, respectively. We conclude that low-dose copper exposure exacerbates the spatial memory impairment of 3xTg-AD mice and perturbs multiple biological/pathogenic processes by dysregulating the mitochondrial and nuclear proteome. Exposure to copper might therefore contribute to the evolution of AD.

RevDate: 2018-03-08
CmpDate: 2017-12-25

Dickerson T, Jauregui CE, Y Teng (2017)

Friend or foe? Mitochondria as a pharmacological target in cancer treatment.

Future medicinal chemistry, 9(18):2197-2210.

Mitochondria have acquired numerous functions over the course of evolution, such as those involved in controlling energy production, cellular metabolism, cell survival, apoptosis and autophagy within host cells. Tumor cells can develop defects in mitochondrial function, presenting a potential strategy for designing selective anticancer therapies. Therefore, cancer has been the main focus of recent research to uncover possible mitochondrial targets for therapeutic benefit. This comprehensive review covers not only the recent discoveries of the roles of mitochondria in cancer development, progression and therapeutic implications but also the findings regarding emerging mitochondrial therapeutic targets and mitochondria-targeted agents. Current challenges and future directions for developments and applications of mitochondrial-targeted therapeutics are also discussed.

RevDate: 2018-08-15
CmpDate: 2018-08-15

McDonald AE, Pichaud N, CA Darveau (2018)

"Alternative" fuels contributing to mitochondrial electron transport: Importance of non-classical pathways in the diversity of animal metabolism.

Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology, 224:185-194.

The study of glycolysis, the TCA cycle, and oxidative phosphorylation in animals has yielded a wealth of information about bioenergetics. Less is known about how animals use fuels other than glucose and less characterized enzymes that are also used to provide electrons to the electron transport system. It has become clear that bioenergetic flexibility is employed by a wide variety of animals in order to successfully grow, maintain cells, and reproduce, and has contributed to the exploitation of new environments and ecological niches through evolution. In most cases, the discovery of these "alternative" fuels and non-classical pathways is relatively recent, but is starting to call into question long believed paradigms about the diversity of animal bioenergetics. We present several specific examples of these "alternatives" and the animals that use them and present some implications for animal mitochondrial physiology research.

RevDate: 2018-02-15

Sun S, Hui M, Wang M, et al (2018)

The complete mitochondrial genome of the alvinocaridid shrimp Shinkaicaris leurokolos (Decapoda, Caridea): Insight into the mitochondrial genetic basis of deep-sea hydrothermal vent adaptation in the shrimp.

Comparative biochemistry and physiology. Part D, Genomics & proteomics, 25:42-52.

Deep-sea hydrothermal vent is one of the most extreme environments on Earth with low oxygen and high levels of toxins. Decapod species from the family Alvinocarididae have colonized and successfully adapted to this extremely harsh environment. Mitochondria plays a vital role in oxygen usage and energy metabolism, thus it may be under selection in the adaptive evolution of the hydrothermal vent shrimps. In this study, the mitochondrial genome (mitogenome) of alvinocaridid shrimp Shinkaicaris leurokolos (Kikuchi & Hashimoto, 2000) was determined through Illumina sequencing. The mitogenome of S. leurokolos was 15,903bp in length, containing 13 protein-coding genes, 2 rRNAs, and 22 tRNAs. The gene order and orientation were identical to those of sequenced alvinocaridids. It has the longest concatenated sequences of protein-coding genes, tRNAs and shortest pooled rRNAs among the alvinocaridids. The control regions (CRs) of alvinocaridid were significantly longer (p<0.01) than those of the other caridaen. The alignment of the alvinocaridid CRs revealed two conserved sequence blocks (CSBs), and each of the CSBs included a noncanonical open reading frame (ORF), which may be involved in adjusting mitochondrial energy metabolism to adapt to the hydrothermal environment. Phylogenetic analysis supported that the deep-sea hydrothermal vent shrimps may have originated from those living in shallow area. Positive selection analysis reveals the evidence of adaptive change in the mitogenome of Alvinocarididae. Thirty potentially important adaptive residues were identified, which were located in atp6, cox1, cox3, cytb and nad1-5. This study explores the mitochondrial genetic basis of hydrothermal vent adaptation in alvinocaridid for the first time, and provides valuable clues regarding the adaptation.

RevDate: 2017-12-19

Dobson GP, Arsyad A, HL Letson (2017)

The Adenosine Hypothesis Revisited: Modulation of Coupling between Myocardial Perfusion and Arterial Compliance.

Frontiers in physiology, 8:824.

For over four decades the thoracic aortic ring model has become one of the most widely used methods to study vascular reactivity and electromechanical coupling. A question that is rarely asked, however, is what function does a drug-mediated relaxation (or contraction) in this model serve in the intact system? The physiological significance of adenosine relaxation in rings isolated from large elastic conduit arteries from a wide range of species remains largely unknown. We propose that adenosine relaxation increases aortic compliance in acute stress states and facilitates ventricular-arterial (VA) coupling, and thereby links compliance and coronary artery perfusion to myocardial energy metabolism. In 1963 Berne argued that adenosine acts as a local negative feedback regulator between oxygen supply and demand in the heart during hypoxic/ischemic stress. The adenosine VA coupling hypothesis extends and enhances Berne's "adenosine hypothesis" from a local regulatory scheme in the heart to include conduit arterial function. In multicellular organisms, evolution may have selected adenosine, nitric oxide, and other vascular mediators, to modulate VA coupling for optimal transfer of oxygen (and nutrients) from the lung, heart, large conduit arteries, arterioles and capillaries to respiring mitochondria. Finally, a discussion of the potential clinical significance of adenosine modulation of VA coupling is extended to vascular aging and disease, including hypertension, diabetes, obesity, coronary artery disease and heart failure.

RevDate: 2018-10-10
CmpDate: 2018-07-05

Bombaça ACS, Dias FA, Ennes-Vidal V, et al (2017)

Hydrogen peroxide resistance in Strigomonas culicis: Effects on mitochondrial functionality and Aedes aegypti interaction.

Free radical biology & medicine, 113:255-266.

Reactive oxygen species (ROS) are toxic molecules involved in several biological processes such as cellular signaling, proliferation, differentiation and cell death. Adaptations to oxidative environments are crucial for the success of the colonization of insects by protozoa. Strigomonas culicis is a monoxenic trypanosomatid found in the midgut of mosquitoes and presenting a life cycle restricted to the epimastigote form. Among S. culicis peculiarities, there is an endosymbiotic bacterium in the cytoplasm, which completes essential biosynthetic routes of the host cell and may represent an intermediary evolutive step in organelle origin, thus constituting an interesting model for evolutive researches. In this work, we induced ROS resistance in wild type S. culicis epimastigotes by the incubation with increasing concentrations of hydrogen peroxide (H2O2), and compared the oxidative and energetic metabolisms among wild type, wild type-H2O2 resistant and aposymbiotic strains. Resistant protozoa were less sensitive to the oxidative challenge and more dependent on oxidative phosphorylation, which was demonstrated by higher oxygen consumption and mitochondrial membrane potential, increased activity of complexes II-III and IV, increased complex II gene expression and higher ATP production. Furthermore, the wild type-H2O2 resistant strain produced reduced ROS levels and showed lower lipid peroxidation, as well as an increase in gene expression of antioxidant enzymes and thiol-dependent peroxidase activity. On the other hand, the aposymbiotic strain showed impaired mitochondrial function, higher H2O2 production and deficient antioxidant response. The induction of H2O2 resistance also led to a remarkable increase in Aedes aegypti midgut binding in vitro and colonization in vivo, indicating that both the pro-oxidant environment in the mosquito gut and the oxidative stress susceptibility regulate S. culicis population in invertebrates.

RevDate: 2017-10-05

Wiens L, Banh S, Sotiri E, et al (2017)

Comparison of Mitochondrial Reactive Oxygen Species Production of Ectothermic and Endothermic Fish Muscle.

Frontiers in physiology, 8:704.

Recently we demonstrated that the capacity of isolated muscle mitochondria to produce reactive oxygen species, measured as H2O2 efflux, is temperature-sensitive in isolated muscle mitochondria of ectothermic fish and the rat, a representative endothermic mammal. However, at physiological temperatures (15° and 37°C for the fish and rat, respectively), the fraction of total mitochondrial electron flux that generated H2O2, the fractional electron leak (FEL), was far lower in the rat than in fish. Those results suggested that the elevated body temperatures associated with endothermy may lead to a compensatory decrease in mitochondrial ROS production relative to respiratory capacity. To test this hypothesis we compare slow twitch (red) muscle mitochondria from the endothermic Pacific bluefin tuna (Thunnus orientalis) with mitochondria from three ectothermic fishes [rainbow trout (Oncorhynchus mykiss), common carp (Cyprinus carpio), and the lake sturgeon (Acipenser fulvescens)] and the rat. At a common assay temperature (25°C) rates of mitochondrial respiration and H2O2 efflux were similar in tuna and the other fishes. The thermal sensitivity of fish mitochondria was similar irrespective of ectothermy or endothermy. Comparing tuna to the rat at a common temperature, respiration rates were similar, or lower depending on mitochondrial substrates. FEL was not different across fish species at a common assay temperature (25°C) but was markedly higher in fishes than in rat. Overall, endothermy and warming of Pacific Bluefin tuna red muscle may increase the potential for ROS production by muscle mitochondria but the evolution of endothermy in this species is not necessarily associated with a compensatory reduction of ROS production relative to the respiratory capacity of mitochondria.

RevDate: 2018-09-17
CmpDate: 2018-02-08

Chaturvedi D, R Mahalakshmi (2017)

Transmembrane β-barrels: Evolution, folding and energetics.

Biochimica et biophysica acta. Biomembranes, 1859(12):2467-2482.

The biogenesis of transmembrane β-barrels (outer membrane proteins, or OMPs) is an elaborate multistep orchestration of the nascent polypeptide with translocases, barrel assembly machinery, and helper chaperone proteins. Several theories exist that describe the mechanism of chaperone-assisted OMP assembly in vivo and unassisted (spontaneous) folding in vitro. Structurally, OMPs of bacterial origin possess even-numbered strands, while mitochondrial β-barrels are even- and odd-stranded. Several underlying similarities between prokaryotic and eukaryotic β-barrels and their folding machinery are known; yet, the link in their evolutionary origin is unclear. While OMPs exhibit diversity in sequence and function, they share similar biophysical attributes and structure. Similarly, it is important to understand the intricate OMP assembly mechanism, particularly in eukaryotic β-barrels that have evolved to perform more complex functions. Here, we deliberate known facets of β-barrel evolution, folding, and stability, and attempt to highlight outstanding questions in β-barrel biogenesis and proteostasis.

RevDate: 2017-12-22
CmpDate: 2017-12-22

Dunn CD (2017)

Some Liked It Hot: A Hypothesis Regarding Establishment of the Proto-Mitochondrial Endosymbiont During Eukaryogenesis.

Journal of molecular evolution, 85(3-4):99-106.

Eukaryotic cells are characterized by a considerable increase in subcellular compartmentalization when compared to prokaryotes. Most evidence suggests that the earliest eukaryotes consisted of mitochondria derived from an α-proteobacterial ancestor enclosed within an archaeal host cell. However, what benefits the archaeal host and the proto-mitochondrial endosymbiont might have obtained at the beginning of this endosymbiotic relationship remains unclear. In this work, I argue that heat generated by the proto-mitochondrion initially permitted an archaeon living at high temperatures to colonize a cooler environment, thereby removing apparent limitations on cellular complexity. Furthermore, heat generation by the endosymbiont would have provided phenotypic flexibility not available through fixed alleles selected for fitness at specific temperatures. Finally, a role for heat production by the proto-mitochondrion bridges a conceptual gap between initial endosymbiont entry to the archaeal host and a later role for mitochondrial ATP production in permitting increased cellular complexity.

RevDate: 2018-06-04
CmpDate: 2017-12-21

Rauch C, Christa G, de Vries J, et al (2017)

Mitochondrial Genome Assemblies of Elysia timida and Elysia cornigera and the Response of Mitochondrion-Associated Metabolism during Starvation.

Genome biology and evolution, 9(7):1873-1879.

Some sacoglossan sea slugs sequester functional plastids (kleptoplasts) from their food, which continue to fix CO2 in a light dependent manner inside the animals. In plants and algae, plastid and mitochondrial metabolism are linked in ways that reach beyond the provision of energy-rich carbon compounds through photosynthesis, but how slug mitochondria respond to starvation or alterations in plastid biochemistry has not been explored. We assembled the mitochondrial genomes of the plastid-sequestering sea slugs Elysia timida and Elysia cornigera from RNA-Seq data that was complemented with standard sequencing of mitochondrial DNA through primer walking. Our data confirm the sister species relationship of the two Sacoglossa and from the analysis of changes in mitochondrial-associated metabolism during starvation we speculate that kleptoplasts might aid in the rerouting or recycling of reducing power independent of, yet maybe improved by, photosynthesis.

RevDate: 2018-05-03
CmpDate: 2018-05-03

Hikmat O, Eichele T, Tzoulis C, et al (2017)

Understanding the Epilepsy in POLG Related Disease.

International journal of molecular sciences, 18(9): pii:ijms18091845.

Epilepsy is common in polymerase gamma (POLG) related disease and is associated with high morbidity and mortality. Epileptiform discharges typically affect the occipital regions initially and focal seizures, commonly evolving to bilateral convulsive seizures which are the most common seizure types in both adults and children. Our work has shown that mtDNA depletion-i.e., the quantitative loss of mtDNA-in neurones is the earliest and most important factor of the subsequent development of cellular dysfunction. Loss of mtDNA leads to loss of mitochondrial respiratory chain (MRC) components that, in turn, progressively disables energy metabolism. This critically balanced neuronal energy metabolism leads to both a chronic and continuous attrition (i.e., neurodegeneration) and it leaves the neurone unable to cope with increased demand that can trigger a potentially catastrophic cycle that results in acute focal necrosis. We believe that it is the onset of epilepsy that triggers the cascade of damage. These events can be identified in the stepwise evolution that characterizes the clinical, Electroencephalography (EEG), neuro-imaging, and neuropathology findings. Early recognition with prompt and aggressive seizure management is vital and may play a role in modifying the epileptogenic process and improving survival.

RevDate: 2018-03-26
CmpDate: 2018-01-31

Zachar I, E Szathmáry (2017)

Breath-giving cooperation: critical review of origin of mitochondria hypotheses : Major unanswered questions point to the importance of early ecology.

Biology direct, 12(1):19 pii:10.1186/s13062-017-0190-5.

The origin of mitochondria is a unique and hard evolutionary problem, embedded within the origin of eukaryotes. The puzzle is challenging due to the egalitarian nature of the transition where lower-level units took over energy metabolism. Contending theories widely disagree on ancestral partners, initial conditions and unfolding of events. There are many open questions but there is no comparative examination of hypotheses. We have specified twelve questions about the observable facts and hidden processes leading to the establishment of the endosymbiont that a valid hypothesis must address. We have objectively compared contending hypotheses under these questions to find the most plausible course of events and to draw insight on missing pieces of the puzzle. Since endosymbiosis borders evolution and ecology, and since a realistic theory has to comply with both domains' constraints, the conclusion is that the most important aspect to clarify is the initial ecological relationship of partners. Metabolic benefits are largely irrelevant at this initial phase, where ecological costs could be more disruptive. There is no single theory capable of answering all questions indicating a severe lack of ecological considerations. A new theory, compliant with recent phylogenomic results, should adhere to these criteria.

REVIEWERS: This article was reviewed by Michael W. Gray, William F. Martin and Purificación López-García.

RevDate: 2018-04-17
CmpDate: 2018-04-17

Lai YC, Baker JS, Donti T, et al (2017)

Mitochondrial Dysfunction Mediated by Poly(ADP-Ribose) Polymerase-1 Activation Contributes to Hippocampal Neuronal Damage Following Status Epilepticus.

International journal of molecular sciences, 18(7): pii:ijms18071502.

Mitochondrial dysfunction plays a central role in the neuropathology associated with status epilepticus (SE) and is implicated in the development of epilepsy. While excitotoxic mechanisms are well-known mediators affecting mitochondrial health following SE, whether hyperactivation of poly(ADP-ribose) polymerase-1 (PARP-1) also contributes to SE-induced mitochondrial dysfunction remains to be examined. Here we first evaluated the temporal evolution of poly-ADP-ribosylated protein levels in hippocampus following kainic acid-induced SE as a marker for PARP-1 activity, and found that PARP-1 was hyperactive at 24 h following SE. We evaluated oxidative metabolism and found decreased NAD⁺ levels by enzymatic cycling, and impaired NAD⁺-dependent mitochondrial respiration as measured by polarography at 24 h following SE. Stereological estimation showed significant cell loss in the hippocampal CA₁ and CA₃ subregions 72 h following SE. PARP-1 inhibition using N-(6-Oxo-5,6-dihydro-phenanthridin-2-yl)- N,N-dimethylacetamide (PJ-34) in vivo administration was associated with preserved NAD⁺ levels and NAD⁺-dependent mitochondrial respiration, and improved CA₁ neuronal survival. These findings suggest that PARP-1 hyperactivation contributes to SE-associated mitochondrial dysfunction and CA₁ hippocampal damage. The deleterious effects of PARP-1 hyperactivation on mitochondrial respiration are in part mediated through intracellular NAD⁺ depletion. Therefore, modulating PARP-1 activity may represent a potential therapeutic target to preserve intracellular energetics and mitochondrial function following SE.

RevDate: 2018-05-10
CmpDate: 2018-05-07

Brandt T, Mourier A, Tain LS, et al (2017)

Changes of mitochondrial ultrastructure and function during ageing in mice and Drosophila.

eLife, 6:.

Ageing is a progressive decline of intrinsic physiological functions. We examined the impact of ageing on the ultrastructure and function of mitochondria in mouse and fruit flies (Drosophila melanogaster) by electron cryo-tomography and respirometry. We discovered distinct age-related changes in both model organisms. Mitochondrial function and ultrastructure are maintained in mouse heart, whereas subpopulations of mitochondria from mouse liver show age-related changes in membrane morphology. Subpopulations of mitochondria from young and old mouse kidney resemble those described for apoptosis. In aged flies, respiratory activity is compromised and the production of peroxide radicals is increased. In about 50% of mitochondria from old flies, the inner membrane organization breaks down. This establishes a clear link between inner membrane architecture and functional decline. Mitochondria were affected by ageing to very different extents, depending on the organism and possibly on the degree to which tissues within the same organism are protected against mitochondrial damage.

RevDate: 2018-07-24

Zhang B, Zhang YH, Wang X, et al (2017)

The mitochondrial genome of a sea anemone Bolocera sp. exhibits novel genetic structures potentially involved in adaptation to the deep-sea environment.

Ecology and evolution, 7(13):4951-4962 pii:ECE33067.

The deep sea is one of the most extensive ecosystems on earth. Organisms living there survive in an extremely harsh environment, and their mitochondrial energy metabolism might be a result of evolution. As one of the most important organelles, mitochondria generate energy through energy metabolism and play an important role in almost all biological activities. In this study, the mitogenome of a deep-sea sea anemone (Bolocera sp.) was sequenced and characterized. Like other metazoans, it contained 13 energy pathway protein-coding genes and two ribosomal RNAs. However, it also exhibited some unique features: just two transfer RNA genes, two group I introns, two transposon-like noncanonical open reading frames (ORFs), and a control region-like (CR-like) element. All of the mitochondrial genes were coded by the same strand (the H-strand). The genetic order and orientation were identical to those of most sequenced actiniarians. Phylogenetic analyses showed that this species was closely related to Bolocera tuediae. Positive selection analysis showed that three residues (31 L and 42 N in ATP6, 570 S in ND5) of Bolocera sp. were positively selected sites. By comparing these features with those of shallow sea anemone species, we deduced that these novel gene features may influence the activity of mitochondrial genes. This study may provide some clues regarding the adaptation of Bolocera sp. to the deep-sea environment.

RevDate: 2018-06-15
CmpDate: 2018-04-05

Martin WF, Tielens AGM, Mentel M, et al (2017)

The Physiology of Phagocytosis in the Context of Mitochondrial Origin.

Microbiology and molecular biology reviews : MMBR, 81(3): pii:81/3/e00008-17.

How mitochondria came to reside within the cytosol of their host has been debated for 50 years. Though current data indicate that the last eukaryote common ancestor possessed mitochondria and was a complex cell, whether mitochondria or complexity came first in eukaryotic evolution is still discussed. In autogenous models (complexity first), the origin of phagocytosis poses the limiting step at eukaryote origin, with mitochondria coming late as an undigested growth substrate. In symbiosis-based models (mitochondria first), the host was an archaeon, and the origin of mitochondria was the limiting step at eukaryote origin, with mitochondria providing bacterial genes, ATP synthesis on internalized bioenergetic membranes, and mitochondrion-derived vesicles as the seed of the eukaryote endomembrane system. Metagenomic studies are uncovering new host-related archaeal lineages that are reported as complex or phagocytosing, although images of such cells are lacking. Here we review the physiology and components of phagocytosis in eukaryotes, critically inspecting the concept of a phagotrophic host. From ATP supply and demand, a mitochondrion-lacking phagotrophic archaeal fermenter would have to ingest about 34 times its body weight in prokaryotic prey to obtain enough ATP to support one cell division. It would lack chemiosmotic ATP synthesis at the plasma membrane, because phagocytosis and chemiosmosis in the same membrane are incompatible. It would have lived from amino acid fermentations, because prokaryotes are mainly protein. Its ATP yield would have been impaired relative to typical archaeal amino acid fermentations, which involve chemiosmosis. In contrast, phagocytosis would have had great physiological benefit for a mitochondrion-bearing cell.

RevDate: 2017-09-12
CmpDate: 2017-09-12

Sharma K (2017)

Mitochondrial Dysfunction in the Diabetic Kidney.

Advances in experimental medicine and biology, 982:553-562.

The role of mitochondria in diabetic complications has been viewed as a source of excess superoxide production leading to cell dysfunction. However, with the lack of benefit of non-specific anti-oxidant approaches this view needs to be re-evaluated. With recent studies using real-time imaging of superoxide, metabolomics, flux studies, transcriptomics and proteomics a new appreciation for the role of mitochondria in the evolution of diabetic kidney disease has emerged. Ongoing studies to further unravel the time course and mechanisms that reduce mitochondrial function will be relevant to novel therapies that could have a major impact on diabetic kidney disease and other diabetic complications.

RevDate: 2018-05-14
CmpDate: 2018-05-14

Horscroft JA, Kotwica AO, Laner V, et al (2017)

Metabolic basis to Sherpa altitude adaptation.

Proceedings of the National Academy of Sciences of the United States of America, 114(24):6382-6387.

The Himalayan Sherpas, a human population of Tibetan descent, are highly adapted to life in the hypobaric hypoxia of high altitude. Mechanisms involving enhanced tissue oxygen delivery in comparison to Lowlander populations have been postulated to play a role in such adaptation. Whether differences in tissue oxygen utilization (i.e., metabolic adaptation) underpin this adaptation is not known, however. We sought to address this issue, applying parallel molecular, biochemical, physiological, and genetic approaches to the study of Sherpas and native Lowlanders, studied before and during exposure to hypobaric hypoxia on a gradual ascent to Mount Everest Base Camp (5,300 m). Compared with Lowlanders, Sherpas demonstrated a lower capacity for fatty acid oxidation in skeletal muscle biopsies, along with enhanced efficiency of oxygen utilization, improved muscle energetics, and protection against oxidative stress. This adaptation appeared to be related, in part, to a putatively advantageous allele for the peroxisome proliferator-activated receptor A (PPARA) gene, which was enriched in the Sherpas compared with the Lowlanders. Our findings suggest that metabolic adaptations underpin human evolution to life at high altitude, and could have an impact upon our understanding of human diseases in which hypoxia is a feature.

RevDate: 2018-06-13
CmpDate: 2018-06-13

Lane N (2017)

Serial endosymbiosis or singular event at the origin of eukaryotes?.

Journal of theoretical biology, 434:58-67.

'On the Origin of Mitosing Cells' heralded a new way of seeing cellular evolution, with symbiosis at its heart. Lynn Margulis (then Sagan) marshalled an impressive array of evidence for endosymbiosis, from cell biology to atmospheric chemistry and Earth history. Despite her emphasis on symbiosis, she saw plenty of evidence for gradualism in eukaryotic evolution, with multiple origins of mitosis and sex, repeated acquisitions of plastids, and putative evolutionary intermediates throughout the microbial world. Later on, Margulis maintained her view of multiple endosymbioses giving rise to other organelles such as hydrogenosomes, in keeping with the polyphyletic assumptions of the serial endosymbiosis theory. She stood at the threshold of the phylogenetic era, and anticipated its potential. Yet while predicting that the nucleotide sequences of genes would enable a detailed reconstruction of eukaryotic evolution, Margulis did not, and could not, imagine the radically different story that would eventually emerge from comparative genomics. The last eukaryotic common ancestor now seems to have been essentially a modern eukaryotic cell that had already evolved mitosis, meiotic sex, organelles and endomembrane systems. The long search for missing evolutionary intermediates has failed to turn up a single example, and those discussed by Margulis turn out to have evolved reductively from more complex ancestors. Strikingly, Margulis argued that all eukaryotes had mitochondria in her 1967 paper (a conclusion that she later disavowed). But she developed her ideas in the context of atmospheric oxygen and aerobic respiration, neither of which is consistent with more recent geological and phylogenetic findings. Instead, a modern synthesis of genomics and bioenergetics points to the endosymbiotic restructuring of eukaryotic genomes in relation to bioenergetic membranes as the singular event that permitted the evolution of morphological complexity.

RevDate: 2018-09-17
CmpDate: 2017-09-26

Yin Q, Zhang Y, Dong D, et al (2017)

Maintenance of neural activities in torpid Rhinolophus ferrumequinum bats revealed by 2D gel-based proteome analysis.

Biochimica et biophysica acta. Proteins and proteomics, 1865(8):1004-1019.

Bats are the only mammals capable of self-powered flying. Many bat species hibernate in winter. A reversible control of cerebral activities is critical for bats to accommodate a repeated torpor-arousal cycle during hibernation. Little is known about the molecular mechanisms that regulate neuronal activities in torpid bats. In this study, Rhinolophus ferrumequinum bat brain proteins were fractionated, and their abundance in active and torpid states was compared. Results of 2D gel-based proteomics showed that 38% of identified proteins with a significant change in abundance are involved in synaptic vesicle recycling and cytoskeletal integrity. Changes in the abundance of proteins related to RNA splicing, proteostasis, redox homeostasis, mitochondrial function, and energy metabolism were also detected. In addition, the levels of GNAO1 (guanine nucleotide-binding protein Gαo subunit), an important modulator of neuronal transmembrane signaling, were significantly increased in the insoluble protein fraction of torpid bats; this may be due to GNAO1 palmitoylation making it insoluble. Our data provide molecular evidence for the maintenance of neuronal activities in torpid bats and suggest that a reversible palmitoylation of the G protein plays a role in the regulation of neuronal activities during bat hibernation.

RevDate: 2018-08-08
CmpDate: 2017-12-29

Du SNN, Khajali F, Dawson NJ, et al (2017)

Hybridization increases mitochondrial production of reactive oxygen species in sunfish.

Evolution; international journal of organic evolution, 71(6):1643-1652.

Mitochondrial dysfunction and oxidative stress have been suggested to be possible mechanisms underlying hybrid breakdown, as a result of mito-nuclear incompatibilities in respiratory complexes of the electron transport system. However, it remains unclear whether hybridization increases the production of reactive oxygen species (ROS) by mitochondria. We used high-resolution respirometry and fluorometry on isolated liver mitochondria to examine mitochondrial physiology and ROS emission in naturally occurring hybrids of pumpkinseed (Lepomis gibbosus) and bluegill (L. macrochirus). ROS emission was greater in hybrids than in both parent species when respiration was supported by complex I (but not complex II) substrates, and was associated with increases in lipid peroxidation. However, respiratory capacities for oxidative phosphorylation, phosphorylation efficiency, and O2 kinetics in hybrids were intermediate between those in parental species. Flux control ratios of capacities for electron transport (measured in uncoupled mitochondria) relative to oxidative phosphorylation suggested that the limiting influence of the phosphorylation system is reduced in hybrids. This likely helped offset impairments in electron transport capacity and complex III activity, but contributed to augmenting ROS production. Therefore, hybridization can increase mitochondrial ROS production, in support of previous suggestions that mitochondrial dysfunction can induce oxidative stress and thus contribute to hybrid breakdown.

RevDate: 2017-10-24
CmpDate: 2017-10-24

Zimorski V, Rauch C, van Hellemond JJ, et al (2017)

The Mitochondrion of Euglena gracilis.

Advances in experimental medicine and biology, 979:19-37.

In the presence of oxygen, Euglena gracilis mitochondria function much like mammalian mitochondria. Under anaerobiosis, E. gracilis mitochondria perform a malonyl-CoA independent synthesis of fatty acids leading to accumulation of wax esters, which serve as the sink for electrons stemming from glycolytic ATP synthesis and pyruvate oxidation. Some components (enzymes and cofactors) of Euglena's anaerobic energy metabolism are found among the anaerobic mitochondria of invertebrates, others are found among hydrogenosomes, the H2-producing anaerobic mitochondria of protists.

RevDate: 2017-06-29
CmpDate: 2017-06-29

Devarshi PP, McNabney SM, TM Henagan (2017)

Skeletal Muscle Nucleo-Mitochondrial Crosstalk in Obesity and Type 2 Diabetes.

International journal of molecular sciences, 18(4): pii:ijms18040831.

Skeletal muscle mitochondrial dysfunction, evidenced by incomplete beta oxidation and accumulation of fatty acid intermediates in the form of long and medium chain acylcarnitines, may contribute to ectopic lipid deposition and insulin resistance during high fat diet (HFD)-induced obesity. The present review discusses the roles of anterograde and retrograde communication in nucleo-mitochondrial crosstalk that determines skeletal muscle mitochondrial adaptations, specifically alterations in mitochondrial number and function in relation to obesity and insulin resistance. Special emphasis is placed on the effects of high fat diet (HFD) feeding on expression of nuclear-encoded mitochondrial genes (NEMGs) nuclear receptor factor 1 (NRF-1) and 2 (NRF-2) and peroxisome proliferator receptor gamma coactivator 1 alpha (PGC-1α) in the onset and progression of insulin resistance during obesity and how HFD-induced alterations in NEMG expression affect skeletal muscle mitochondrial adaptations in relation to beta oxidation of fatty acids. Finally, the potential ability of acylcarnitines or fatty acid intermediates resulting from mitochondrial beta oxidation to act as retrograde signals in nucleo-mitochondrial crosstalk is reviewed and discussed.

RevDate: 2018-06-13
CmpDate: 2018-06-13

Schönfeld P, G Reiser (2017)

Brain energy metabolism spurns fatty acids as fuel due to their inherent mitotoxicity and potential capacity to unleash neurodegeneration.

Neurochemistry international, 109:68-77.

The brain uses long-chain fatty acids (LCFAs) to a negligible extent as fuel for the mitochondrial energy generation, in contrast to other tissues that also demand high energy. Besides this generally accepted view, some studies using cultured neural cells or whole brain indicate a moderately active mitochondrial β-oxidation. Here, we corroborate the conclusion that brain mitochondria are unable to oxidize fatty acids. In contrast, the combustion of liver-derived ketone bodies by neural cells is long-known. Furthermore, new insights indicate the use of odd-numbered medium-chain fatty acids as valuable source for maintaining the level of intermediates of the citric acid cycle in brain mitochondria. Non-esterified LCFAs or their activated forms exert a large variety of harmful side-effects on mitochondria, such as enhancing the mitochondrial ROS generation in distinct steps of the β-oxidation and therefore potentially increasing oxidative stress. Hence, the question arises: Why do in brain energy metabolism mitochondria selectively spurn LCFAs as energy source? The most likely answer are the relatively higher content of peroxidation-sensitive polyunsaturated fatty acids and the low antioxidative defense in brain tissue. There are two remarkable peroxisomal defects, one relating to α-oxidation of phytanic acid and the other to uptake of very long-chain fatty acids (VLCFAs) which lead to pathologically high tissue levels of such fatty acids. Both, the accumulation of phytanic acid and that of VLCFAs give an enlightening insight into harmful activities of fatty acids on neural cells, which possibly explain why evolution has prevented brain mitochondria from the equipment with significant β-oxidation enzymatic capacity.

RevDate: 2018-09-21
CmpDate: 2018-09-21

Roberts RG (2017)

Mitochondria-A billion years of cohabitation.

PLoS biology, 15(3):e2002338 pii:pbio.2002338.

RevDate: 2017-08-16

Karnkowska A, V Hampl (2016)

The curious case of vanishing mitochondria.

Microbial cell (Graz, Austria), 3(10):491-494 pii:MIC0176E178.

Due to their involvement in the energy metabolism, mitochondria are essential for most eukaryotic cells. Microbial eukaryotes living in low oxygen environments possess reduced forms of mitochondria, namely mitochondrion-related organelles (MROs). These do not produce ATP by oxidative phosphorylation on their membranes and some do not produce ATP at all. Still, they are indispensable because of other essential functions such as iron-sulphur (Fe-S) cluster assembly. Recently, the first microbial eukaryote with neither mitochondrion nor MRO was characterized - Monocercomonoides sp. Genome and transcriptome sequencing of Monocercomonoides revealed that it lacks all hallmark mitochondrial proteins. Crucially, the essential mitochondrial pathway for the Fe-S cluster assembly (ISC) was replaced by a bacterial sulphur mobilization (SUF) system. The discovery of such bona fide amitochondriate eukaryote broadens our knowledge about the diversity and plasticity of eukaryotic cells and provides a substantial contribution to our understanding of eukaryotic cell evolution.

RevDate: 2018-07-05
CmpDate: 2018-01-08

Lynch M, GK Marinov (2017)

Membranes, energetics, and evolution across the prokaryote-eukaryote divide.

eLife, 6: pii:20437.

The evolution of the eukaryotic cell marked a profound moment in Earth's history, with most of the visible biota coming to rely on intracellular membrane-bound organelles. It has been suggested that this evolutionary transition was critically dependent on the movement of ATP synthesis from the cell surface to mitochondrial membranes and the resultant boost to the energetic capacity of eukaryotic cells. However, contrary to this hypothesis, numerous lines of evidence suggest that eukaryotes are no more bioenergetically efficient than prokaryotes. Thus, although the origin of the mitochondrion was a key event in evolutionary history, there is no reason to think membrane bioenergetics played a direct, causal role in the transition from prokaryotes to eukaryotes and the subsequent explosive diversification of cellular and organismal complexity.

RevDate: 2018-09-26
CmpDate: 2017-08-11

Krishnan A, Abdullah TS, Mounajjed T, et al (2017)

A longitudinal study of whole body, tissue, and cellular physiology in a mouse model of fibrosing NASH with high fidelity to the human condition.

American journal of physiology. Gastrointestinal and liver physiology, 312(6):G666-G680.

The sequence of events that lead to inflammation and fibrosing nonalcoholic steatohepatitis (NASH) is incompletely understood. Hence, we investigated the chronology of whole body, tissue, and cellular events that occur during the evolution of diet-induced NASH. Male C57Bl/6 mice were assigned to a fast-food (FF; high calorie, high cholesterol, high fructose) or standard-chow (SC) diet over a period of 36 wk. Liver histology, body composition, mitochondrial respiration, metabolic rate, gene expression, and hepatic lipid content were analyzed. Insulin resistance [homeostasis model assessment-insulin resistance (HOMA-IR)] increased 10-fold after 4 wk. Fibrosing NASH was fully established by 16 wk. Total hepatic lipids increased by 4 wk and remained two- to threefold increased throughout. Hepatic triglycerides declined from sixfold increase at 8 wk to threefold increase by 36 wk. In contrast, hepatic cholesterol levels steadily increased from baseline at 8 wk to twofold by 36 wk. The hepatic immune cell population altered over time with macrophages persisting beyond 16 wk. Mitochondrial oxygen flux rates of FF mice diet were uniformly lower with all the tested substrates (13-276 pmol·s-1·ml-1 per unit citrate synthase) than SC mice (17-394 pmol·s-1·ml-1 per unit citrate synthase) and was accompanied by decreased mitochondrial:nuclear gene copy number ratios after 4 wk. Metabolic rate was lower in FF mice. Mitochondrial glutathione was significantly decreased at 24 wk in FF mice. Expression of dismutases and catalase was also decreased in FF mice. The evolution of NASH in the FF diet-induced model is multiphasic, particularly in terms of hepatic lipid composition. Insulin resistance precedes hepatic inflammation and fibrosis. Mitochondrial dysfunction and depletion occur after the histological features of NASH are apparent. Collectively, these observations provide a unique overview of the sequence of changes that coevolve with the histological evolution of NASH.NEW & NOTEWORTHY This study demonstrates in a first of kind longitudinal analysis, the evolution of nonalcoholic steatohepatitis (NASH) on a fast-food diet-induced model. Key findings include 1) hepatic lipid composition changes in a multiphasic fashion as NASH evolves; 2) insulin resistance precedes hepatic inflammation and fibrosis, answering a longstanding chicken-and-egg question regarding the relationship of insulin resistance to liver histology in NASH; and 3) mitochondrial dysfunction and depletion occur after the histological features of NASH are apparent.

RevDate: 2017-03-16
CmpDate: 2017-03-16

Ling SS, Zhu Y, Lan D, et al (2017)

Analysis of the cytochrome c oxidase subunit II (COX2) gene in giant panda, Ailuropoda melanoleuca.

Genetics and molecular research : GMR, 16(1): pii:gmr-16-01-gmr.16019158.

The giant panda, Ailuropoda melanoleuca (Ursidae), has a unique bamboo-based diet; however, this low-energy intake has been sufficient to maintain the metabolic processes of this species since the fourth ice age. As mitochondria are the main sites for energy metabolism in animals, the protein-coding genes involved in mitochondrial respiratory chains, particularly cytochrome c oxidase subunit II (COX2), which is the rate-limiting enzyme in electron transfer, could play an important role in giant panda metabolism. Therefore, the present study aimed to isolate, sequence, and analyze the COX2 DNA from individuals kept at the Giant Panda Protection and Research Center, China, and compare these sequences with those of the other Ursidae family members. Multiple sequence alignment showed that the COX2 gene had three point mutations that defined three haplotypes, with 60% of the sequences corresponding to haplotype I. The neutrality tests revealed that the COX2 gene was conserved throughout evolution, and the maximum likelihood phylogenetic analysis, using homologous sequences from other Ursidae species, showed clustering of the COX2 sequences of giant pandas, suggesting that this gene evolved differently in them.

RevDate: 2018-09-17
CmpDate: 2017-10-24

Baffy G (2017)

Mitochondrial uncoupling in cancer cells: Liabilities and opportunities.

Biochimica et biophysica acta. Bioenergetics, 1858(8):655-664.

Acquisition of the endosymbiotic ancestor of mitochondria was a critical event in eukaryote evolution. Mitochondria offered an unparalleled source of metabolic energy through oxidative phosphorylation and allowed the development of multicellular life. However, as molecular oxygen had become the terminal electron acceptor in most eukaryotic cells, the electron transport chain proved to be the largest intracellular source of superoxide, contributing to macromolecular injury, aging, and cancer. Hence, the 'contract of endosymbiosis' represents a compromise between the possibilities and perils of multicellular life. Uncoupling proteins (UCPs), a group of the solute carrier family of transporters, may remove some of the physiologic constraints that link mitochondrial respiration and ATP synthesis by mediating inducible proton leak and limiting oxidative cell injury. This important property makes UCPs an ancient partner in the metabolic adaptation of cancer cells. Efforts are underway to explore the therapeutic opportunities stemming from the intriguing relationship of UCPs and cancer. This article is part of a Special Issue entitled Mitochondria in Cancer, edited by Giuseppe Gasparre, Rodrigue Rossignol and Pierre Sonveaux.

RevDate: 2018-03-09
CmpDate: 2017-11-22

Speijer D (2017)

Alternating terminal electron-acceptors at the basis of symbiogenesis: How oxygen ignited eukaryotic evolution.

BioEssays : news and reviews in molecular, cellular and developmental biology, 39(2):.

What kind of symbiosis between archaeon and bacterium gave rise to their eventual merger at the origin of the eukaryotes? I hypothesize that conditions favouring bacterial uptake were based on exchange of intermediate carbohydrate metabolites required by recurring changes in availability and use of the two different terminal electron chain acceptors, the bacterial one being oxygen. Oxygen won, and definitive loss of the archaeal membrane potential allowed permanent establishment of the bacterial partner as the proto-mitochondrion, further metabolic integration and highly efficient ATP production. This represents initial symbiogenesis, when crucial eukaryotic traits arose in response to the archaeon-bacterium merger. The attendant generation of internal reactive oxygen species (ROS) gave rise to a myriad of further eukaryotic adaptations, such as extreme mitochondrial genome reduction, nuclei, peroxisomes and meiotic sex. Eukaryotic origins could have started with shuffling intermediate metabolites as is still essential today.

RevDate: 2017-08-16

Faktorová D, Dobáková E, Peña-Diaz P, et al (2016)

From simple to supercomplex: mitochondrial genomes of euglenozoan protists.

F1000Research, 5:.

Mitochondria are double membrane organelles of endosymbiotic origin, best known for constituting the centre of energetics of a eukaryotic cell. They contain their own mitochondrial genome, which as a consequence of gradual reduction during evolution typically contains less than two dozens of genes. In this review, we highlight the extremely diverse architecture of mitochondrial genomes and mechanisms of gene expression between the three sister groups constituting the phylum Euglenozoa - Euglenida, Diplonemea and Kinetoplastea. The earliest diverging euglenids possess a simplified mitochondrial genome and a conventional gene expression, whereas both are highly complex in the two other groups. The expression of their mitochondrial-encoded proteins requires extensive post-transcriptional modifications guided by complex protein machineries and multiple small RNA molecules. Moreover, the least studied diplonemids, which have been recently discovered as a highly abundant component of the world ocean plankton, possess one of the most complicated mitochondrial genome organisations known to date.

RevDate: 2017-11-19
CmpDate: 2017-06-14

Liu S, Roellig DM, Guo Y, et al (2016)

Evolution of mitosome metabolism and invasion-related proteins in Cryptosporidium.

BMC genomics, 17(1):1006 pii:10.1186/s12864-016-3343-5.

BACKGROUND: The switch from photosynthetic or predatory to parasitic life strategies by apicomplexans is accompanied with a reductive evolution of genomes and losses of metabolic capabilities. Cryptosporidium is an extreme example of reductive evolution among apicomplexans, with losses of both the mitosome genome and many metabolic pathways. Previous observations on reductive evolution were largely based on comparative studies of various groups of apicomplexans. In this study, we sequenced two divergent Cryptosporidium species and conducted a comparative genomic analysis to infer the reductive evolution of metabolic pathways and differential evolution of invasion-related proteins within the Cryptosporidium lineage.

RESULTS: In energy metabolism, Cryptosporidium species differ from each other mostly in mitosome metabolic pathways. Compared with C. parvum and C. hominis, C. andersoni possesses more aerobic metabolism and a conventional electron transport chain, whereas C. ubiquitum has further reductions in ubiquinone and polyisprenoid biosynthesis and has lost both the conventional and alternative electron transport systems. For invasion-associated proteins, similar to C. hominis, a reduction in the number of genes encoding secreted MEDLE and insulinase-like proteins in the subtelomeric regions of chromosomes 5 and 6 was also observed in C. ubiquitum and C. andersoni, whereas mucin-type glycoproteins are highly divergent between the gastric C. andersoni and intestinal Cryptosporidium species.

CONCLUSIONS: Results of the study suggest that rapidly evolving mitosome metabolism and secreted invasion-related proteins could be involved in tissue tropism and host specificity in Cryptosporidium spp. The finding of progressive reduction in mitosome metabolism among Cryptosporidium species improves our knowledge of organelle evolution within apicomplexans.

RevDate: 2018-04-29

Malecki M, J Bähler (2016)

Identifying genes required for respiratory growth of fission yeast.

Wellcome open research, 1:12.

We have used both auxotroph and prototroph versions of the latest deletion-mutant library to identify genes required for respiratory growth on solid glycerol medium in fission yeast. This data set complements and enhances our recent study on functional and regulatory aspects of energy metabolism by providing additional proteins that are involved in respiration. Most proteins identified in this mutant screen have not been implicated in respiration in budding yeast. We also provide a protocol to generate a prototrophic mutant library, and data on technical and biological reproducibility of colony-based high-throughput screens.

RevDate: 2018-04-25
CmpDate: 2017-12-13

Raefsky SM, MP Mattson (2017)

Adaptive responses of neuronal mitochondria to bioenergetic challenges: Roles in neuroplasticity and disease resistance.

Free radical biology & medicine, 102:203-216.

An important concept in neurobiology is "neurons that fire together, wire together" which means that the formation and maintenance of synapses is promoted by activation of those synapses. Very similar to the effects of the stress of exercise on muscle cells, emerging findings suggest that neurons respond to activity by activating signaling pathways (e.g., Ca2+, CREB, PGC-1α, NF-κB) that stimulate mitochondrial biogenesis and cellular stress resistance. These pathways are also activated by aerobic exercise and food deprivation, two bioenergetic challenges of fundamental importance in the evolution of the brains of all mammals, including humans. The metabolic 'switch' in fuel source from liver glycogen store-derived glucose to adipose cell-derived fatty acids and their ketone metabolites during fasting and sustained exercise, appears to be a pivotal trigger of both brain-intrinsic and peripheral organ-derived signals that enhance learning and memory and underlying synaptic plasticity and neurogenesis. Brain-intrinsic extracellular signals include the excitatory neurotransmitter glutamate and the neurotrophic factor BDNF, and peripheral signals may include the liver-derived ketone 3-hydroxybutyrate and the muscle cell-derived protein irisin. Emerging findings suggest that fasting, exercise and an intellectually challenging lifestyle can protect neurons against the dysfunction and degeneration that they would otherwise suffer in acute brain injuries (stroke and head trauma) and neurodegenerative disorders including Alzheimer's, Parkinson's and Huntington's disease. Among the prominent intracellular responses of neurons to these bioenergetic challenges are up-regulation of antioxidant defenses, autophagy/mitophagy and DNA repair. A better understanding of such fundamental hormesis-based adaptive neuronal response mechanisms is expected to result in the development and implementation of novel interventions to promote optimal brain function and healthy brain aging.

RevDate: 2018-02-16
CmpDate: 2018-02-16

Sanchez-Puerta MV, García LE, Wohlfeiler J, et al (2017)

Unparalleled replacement of native mitochondrial genes by foreign homologs in a holoparasitic plant.

The New phytologist, 214(1):376-387.

Horizontal gene transfer (HGT) among flowering plant mitochondria occurs frequently and, in most cases, leads to nonfunctional transgenes in the recipient genome. Parasitic plants are particularly prone to this phenomenon, but their mitochondrial genomes (mtDNA) have been largely unexplored. We undertook a large-scale mitochondrial genomic study of the holoparasitic plant Lophophytum mirabile (Balanophoraceae). Comprehensive phylogenetic analyses were performed to address the frequency, origin, and impact of HGT. The sequencing of the complete mtDNA of L. mirabile revealed the unprecedented acquisition of host-derived mitochondrial genes, representing 80% of the protein-coding gene content. All but two of these foreign genes replaced the native homologs and are probably functional in energy metabolism. The genome consists of 54 circular-mapping chromosomes, 25 of which carry no intact genes. The likely functional replacement of up to 26 genes in L. mirabile represents a stunning example of the potential effect of rampant HGT on plant mitochondria. The use of host-derived genes may have a positive effect on the host-parasite relationship, but could also be the result of nonadaptive forces.

RevDate: 2018-02-07
CmpDate: 2017-07-10

Malecki M, Bitton DA, Rodríguez-López M, et al (2016)

Functional and regulatory profiling of energy metabolism in fission yeast.

Genome biology, 17(1):240 pii:10.1186/s13059-016-1101-2.

BACKGROUND: The control of energy metabolism is fundamental for cell growth and function and anomalies in it are implicated in complex diseases and ageing. Metabolism in yeast cells can be manipulated by supplying different carbon sources: yeast grown on glucose rapidly proliferates by fermentation, analogous to tumour cells growing by aerobic glycolysis, whereas on non-fermentable carbon sources metabolism shifts towards respiration.

RESULTS: We screened deletion libraries of fission yeast to identify over 200 genes required for respiratory growth. Growth media and auxotrophic mutants strongly influenced respiratory metabolism. Most genes uncovered in the mutant screens have not been implicated in respiration in budding yeast. We applied gene-expression profiling approaches to compare steady-state fermentative and respiratory growth and to analyse the dynamic adaptation to respiratory growth. The transcript levels of most genes functioning in energy metabolism pathways are coherently tuned, reflecting anticipated differences in metabolic flows between fermenting and respiring cells. We show that acetyl-CoA synthase, rather than citrate lyase, is essential for acetyl-CoA synthesis in fission yeast. We also investigated the transcriptional response to mitochondrial damage by genetic or chemical perturbations, defining a retrograde response that involves the concerted regulation of distinct groups of nuclear genes that may avert harm from mitochondrial malfunction.

CONCLUSIONS: This study provides a rich framework of the genetic and regulatory basis of energy metabolism in fission yeast and beyond, and it pinpoints weaknesses of commonly used auxotroph mutants for investigating metabolism. As a model for cellular energy regulation, fission yeast provides an attractive and complementary system to budding yeast.

RevDate: 2018-04-09
CmpDate: 2017-09-22

Đorđević M, Stojković B, Savković U, et al (2017)

Sex-specific mitonuclear epistasis and the evolution of mitochondrial bioenergetics, ageing, and life history in seed beetles.

Evolution; international journal of organic evolution, 71(2):274-288.

The role of mitochondrial DNA for the evolution of life-history traits remains debated. We examined mitonuclear effects on the activity of the multisubunit complex of the electron transport chain (ETC) involved in oxidative phosphorylation (OXPHOS) across lines of the seed beetle Acanthoscelides obtectus selected for a short (E) or a long (L) life for more than >160 generations. We constructed and phenotyped mitonuclear introgression lines, which allowed us to assess the independent effects of the evolutionary history of the nuclear and the mitochondrial genome. The nuclear genome was responsible for the largest share of divergence seen in ageing. However, the mitochondrial genome also had sizeable effects, which were sex-specific and expressed primarily as epistatic interactions with the nuclear genome. The effects of mitonuclear disruption were largely consistent with mitonuclear coadaptation. Variation in ETC activity explained a large proportion of variance in ageing and life-history traits and this multivariate relationship differed somewhat between the sexes. In conclusion, mitonuclear epistasis has played an important role in the laboratory evolution of ETC complex activity, ageing, and life histories and these are closely associated. The mitonuclear architecture of evolved differences in life-history traits and mitochondrial bioenergetics was sex-specific.

RevDate: 2018-09-17
CmpDate: 2017-11-03

Kadam AA, Jubin T, Mir HA, et al (2017)

Potential role of Apoptosis Inducing Factor in evolutionarily significant eukaryote, Dictyostelium discoideum survival.

Biochimica et biophysica acta. General subjects, 1861(1 Pt A):2942-2955.

Apoptosis Inducing Factor (AIF), a phylogenetically conserved mitochondrial inter-membrane space flavoprotein has an important role in caspase independent cell death. Nevertheless, AIF is also essential for cell survival. It is required for mitochondrial organization and energy metabolism. Upon apoptotic stimulation, AIF induces DNA fragmentation after its mitochondrio-nuclear translocation. Although it executes critical cellular functions in a coordinated manner, the exact mechanism still remains obscure. The present study aims to understand AIF's role in cell survival, growth and development by its down-regulation in an interesting unicellular eukaryote, D. discoideum which exhibits multicellularity upon starvation. Constitutive AIF down-regulated (dR) cells exhibited slower growth and delayed developmental morphogenesis. Also, constitutive AIF dR cells manifested high intracellular ROS, oxidative DNA damage and calcium levels with lower ATP content. Interestingly, constitutive AIF dR cells showed amelioration in cell growth upon antioxidant treatment, strengthening its role as ROS regulator. Under oxidative stress, AIF dR cells showed early mitochondrial membrane depolarization followed by AIF translocation from mitochondria to nucleus and exhibited necrotic cell death as compared to paraptoptic cell death of control cells. Thus, the results of this study provide an exemplar where AIF is involved in growth and development by regulating ROS levels and maintaining mitochondrial function in D. discoideum, an evolutionarily significant model organism exhibiting caspase independent apoptosis.

RevDate: 2017-11-30
CmpDate: 2017-05-09

Sookoian S, Flichman D, Scian R, et al (2016)

Mitochondrial genome architecture in non-alcoholic fatty liver disease.

The Journal of pathology, 240(4):437-449.

Non-alcoholic fatty liver disease (NAFLD) is associated with mitochondrial dysfunction, a decreased liver mitochondrial DNA (mtDNA) content, and impaired energy metabolism. To understand the clinical implications of mtDNA diversity in the biology of NAFLD, we applied deep-coverage whole sequencing of the liver mitochondrial genomes. We used a multistage study design, including a discovery phase, a phenotype-oriented study to assess the mutational burden in patients with steatohepatitis at different stages of liver fibrosis, and a replication study to validate findings in loci of interest. We also assessed the potential protein-level impact of the observed mutations. To determine whether the observed changes are tissue-specific, we compared the liver and the corresponding peripheral blood entire mitochondrial genomes. The nuclear genes POLG and POLG2 (mitochondrial DNA polymerase-γ) were also sequenced. We observed that the liver mtDNA of patients with NAFLD harbours complex genomes with a significantly higher mutational (1.28-fold) rate and degree of heteroplasmy than in controls. The analysis of liver mitochondrial genomes of patients with different degrees of fibrosis revealed that the disease severity is associated with an overall 1.4-fold increase in mutation rate, including mutations in genes of the oxidative phosphorylation (OXPHOS) chain. Significant differences in gene and protein expression patterns were observed in association with the cumulative number of OXPHOS polymorphic sites. We observed a high degree of homology (∼98%) between the blood and liver mitochondrial genomes. A missense POLG p.Gln1236His variant was associated with liver mtDNA copy number. In conclusion, we have demonstrated that OXPHOS genes contain the highest number of hotspot positions associated with a more severe phenotype. The variability of the mitochondrial genomes probably originates from a common germline source; hence, it may explain a fraction of the 'missing heritability' of NAFLD. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

RevDate: 2017-12-19
CmpDate: 2017-07-14

Nunn AV, Guy GW, JD Bell (2016)

The quantum mitochondrion and optimal health.

Biochemical Society transactions, 44(4):1101-1110.

A sufficiently complex set of molecules, if subject to perturbation, will self-organize and show emergent behaviour. If such a system can take on information it will become subject to natural selection. This could explain how self-replicating molecules evolved into life and how intelligence arose. A pivotal step in this evolutionary process was of course the emergence of the eukaryote and the advent of the mitochondrion, which both enhanced energy production per cell and increased the ability to process, store and utilize information. Recent research suggest that from its inception life embraced quantum effects such as 'tunnelling' and 'coherence' while competition and stressful conditions provided a constant driver for natural selection. We believe that the biphasic adaptive response to stress described by hormesis-a process that captures information to enable adaptability, is central to this whole process. Critically, hormesis could improve mitochondrial quantum efficiency, improving the ATP/ROS ratio, whereas inflammation, which is tightly associated with the aging process, might do the opposite. This all suggests that to achieve optimal health and healthy aging, one has to sufficiently stress the system to ensure peak mitochondrial function, which itself could reflect selection of optimum efficiency at the quantum level.

RevDate: 2016-07-28
CmpDate: 2016-08-11

Pennisi E (2016)

EVOLUTIONARY BIOLOGY. Do genomic conflicts drive evolution?.

Science (New York, N.Y.), 353(6297):334-335.

RevDate: 2018-03-08
CmpDate: 2017-10-26

Martin WF, Neukirchen S, Zimorski V, et al (2016)

Energy for two: New archaeal lineages and the origin of mitochondria.

BioEssays : news and reviews in molecular, cellular and developmental biology, 38(9):850-856.

Metagenomics bears upon all aspects of microbiology, including our understanding of mitochondrial and eukaryote origin. Recently, ribosomal protein phylogenies show the eukaryote host lineage - the archaeal lineage that acquired the mitochondrion - to branch within the archaea. Metagenomic studies are now uncovering new archaeal lineages that branch more closely to the host than any cultivated archaea do. But how do they grow? Carbon and energy metabolism as pieced together from metagenome assemblies of these new archaeal lineages, such as the Deep Sea Archaeal Group (including Lokiarchaeota) and Bathyarchaeota, do not match the physiology of any cultivated microbes. Understanding how these new lineages live in their environment is important, and might hold clues about how mitochondria arose and how the eukaryotic lineage got started. Here we look at these exciting new metagenomic studies, what they say about archaeal physiology in modern environments, how they impact views on host-mitochondrion physiological interactions at eukaryote origin.

RevDate: 2018-03-16
CmpDate: 2018-01-17

Cardoso S, Carvalho C, Correia SC, et al (2016)

Alzheimer's Disease: From Mitochondrial Perturbations to Mitochondrial Medicine.

Brain pathology (Zurich, Switzerland), 26(5):632-647.

Age-related neurodegenerative diseases such as Alzheimer's disease (AD) are distressing conditions causing countless levels of suffering for which treatment is often insufficient or inexistent. Considered to be the most common cause of dementia and an incurable, progressive neurodegenerative disorder, the intricate pathogenic mechanisms of AD continue to be revealed and, consequently, an effective treatment needs to be developed. Among the diverse hypothesis that have been proposed to explain AD pathogenesis, the one concerning mitochondrial dysfunction has raised as one of the most discussed with an actual acceptance in the field. It posits that manipulating mitochondrial function and understanding the deficits that result in mitochondrial injury may help to control and/or limit the development of AD. To achieve such goal, the concept of mitochondrial medicine places itself as a promising gathering of strategies to directly manage the major insidious disturbances of mitochondrial homeostasis as well as attempts to directly or indirectly manage its consequences in the context of AD. The aim of this review is to summarize the evolution that occurred from the establishment of mitochondrial homeostasis perturbation as masterpieces in AD pathogenesis up until the development of mitochondrial medicine. Following a brief glimpse in the past and current hypothesis regarding the triad of aging, mitochondria and AD, this manuscript will address the major mechanisms currently believed to participate in above mentioned events. Both pharmacological and lifestyle interventions will also be reviewed as AD-related mitochondrial therapeutics.

RevDate: 2017-10-04
CmpDate: 2017-10-04

Mesa-Torres N, Calvo AC, Oppici E, et al (2016)

Caenorhabditis elegans AGXT-1 is a mitochondrial and temperature-adapted ortholog of peroxisomal human AGT1: New insights into between-species divergence in glyoxylate metabolism.

Biochimica et biophysica acta, 1864(9):1195-1205.

In humans, glyoxylate is an intermediary product of metabolism, whose concentration is finely balanced. Mutations in peroxisomal alanine:glyoxylate aminotransferase (hAGT1) cause primary hyperoxaluria type 1 (PH1), which results in glyoxylate accumulation that is converted to toxic oxalate. In contrast, glyoxylate is used by the nematode Caenorhabditis elegans through a glyoxylate cycle to by-pass the decarboxylation steps of the tricarboxylic acid cycle and thus contributing to energy production and gluconeogenesis from stored lipids. To investigate the differences in glyoxylate metabolism between humans and C. elegans and to determine whether the nematode might be a suitable model for PH1, we have characterized here the predicted nematode ortholog of hAGT1 (AGXT-1) and compared its molecular properties with those of the human enzyme. Both enzymes form active PLP-dependent dimers with high specificity towards alanine and glyoxylate, and display similar three-dimensional structures. Interestingly, AGXT-1 shows 5-fold higher activity towards the alanine/glyoxylate pair than hAGT1. Thermal and chemical stability of AGXT-1 is lower than that of hAGT1, suggesting temperature-adaptation of the nematode enzyme linked to the lower optimal growth temperature of C. elegans. Remarkably, in vivo experiments demonstrate the mitochondrial localization of AGXT-1 in contrast to the peroxisomal compartmentalization of hAGT1. Our results support the view that the different glyoxylate metabolism in the nematode is associated with the divergent molecular properties and subcellular localization of the alanine:glyoxylate aminotransferase activity.

RevDate: 2016-02-26
CmpDate: 2016-03-14

Hamers L (2016)

EVOLUTION. Why do cells' power plants hang on to their own genomes?.

Science (New York, N.Y.), 351(6276):903.

RevDate: 2016-05-27
CmpDate: 2016-03-03

Ball SG, Bhattacharya D, AP Weber (2016)

EVOLUTION. Pathogen to powerhouse.

Science (New York, N.Y.), 351(6274):659-660.

RevDate: 2017-11-22
CmpDate: 2017-07-12

Kelley JL, Arias-Rodriguez L, Patacsil Martin D, et al (2016)

Mechanisms Underlying Adaptation to Life in Hydrogen Sulfide-Rich Environments.

Molecular biology and evolution, 33(6):1419-1434.

Hydrogen sulfide (H2S) is a potent toxicant interfering with oxidative phosphorylation in mitochondria and creating extreme environmental conditions in aquatic ecosystems. The mechanistic basis of adaptation to perpetual exposure to H2S remains poorly understood. We investigated evolutionarily independent lineages of livebearing fishes that have colonized and adapted to springs rich in H2S and compared their genome-wide gene expression patterns with closely related lineages from adjacent, nonsulfidic streams. Significant differences in gene expression were uncovered between all sulfidic and nonsulfidic population pairs. Variation in the number of differentially expressed genes among population pairs corresponded to differences in divergence times and rates of gene flow, which is consistent with neutral drift driving a substantial portion of gene expression variation among populations. Accordingly, there was little evidence for convergent evolution shaping large-scale gene expression patterns among independent sulfide spring populations. Nonetheless, we identified a small number of genes that was consistently differentially expressed in the same direction in all sulfidic and nonsulfidic population pairs. Functional annotation of shared differentially expressed genes indicated upregulation of genes associated with enzymatic H2S detoxification and transport of oxidized sulfur species, oxidative phosphorylation, energy metabolism, and pathways involved in responses to oxidative stress. Overall, our results suggest that modification of processes associated with H2S detoxification and toxicity likely complement each other to mediate elevated H2S tolerance in sulfide spring fishes. Our analyses allow for the development of novel hypotheses about biochemical and physiological mechanisms of adaptation to extreme environments.

RevDate: 2016-08-09
CmpDate: 2016-06-16

Lane N, WF Martin (2016)

Mitochondria, complexity, and evolutionary deficit spending.

Proceedings of the National Academy of Sciences of the United States of America, 113(6):E666.

RevDate: 2017-08-30
CmpDate: 2016-06-06

Ray S, Kassan A, Busija AR, et al (2016)

The plasma membrane as a capacitor for energy and metabolism.

American journal of physiology. Cell physiology, 310(3):C181-92.

When considering which components of the cell are the most critical to function and physiology, we naturally focus on the nucleus, the mitochondria that regulate energy and apoptotic signaling, or other organelles such as the endoplasmic reticulum, Golgi, ribosomes, etc. Few people will suggest that the membrane is the most critical element of a cell in terms of function and physiology. Those that consider the membrane critical will point to its obvious barrier function regulated by the lipid bilayer and numerous ion channels that regulate homeostatic gradients. What becomes evident upon closer inspection is that not all membranes are created equal and that there are lipid-rich microdomains that serve as platforms of signaling and a means of communication with the intracellular environment. In this review, we explore the evolution of membranes, focus on lipid-rich microdomains, and advance the novel concept that membranes serve as "capacitors for energy and metabolism." Within this framework, the membrane then is the primary and critical regulator of stress and disease adaptation of the cell.

RevDate: 2017-02-17
CmpDate: 2017-02-17

Jaromin E, Wyszkowska J, Labecka AM, et al (2016)

Hindlimb muscle fibre size and glycogen stores in bank voles with increased aerobic exercise metabolism.

The Journal of experimental biology, 219(Pt 4):470-473.

To test hypotheses concerning physiological factors limiting the rate of aerobic exercise metabolism, we used a unique experimental evolution model: lines of bank voles selected for high swim-induced aerobic metabolism (A) and unselected, control lines (C). We investigated putative adaptations that result in the increased performance of the hindlimb muscle (gastrocnemius joined with plantaris). The body mass-adjusted muscle mass was higher in A-lines (0.093 g) than in C-lines (0.083 g; P=0.01). However, selection did not affect mean muscle fibre cross-sectional area (P=0.34) or glycogen content assessed with a histochemical periodic acid-Schiff reaction (PAS; P=0.82). The results suggest that the increased aerobic performance is achieved by an increase of total muscle mass, without major qualitative changes in the muscle fibre architecture. However, such a conclusion should be treated with caution, because other modifications, such as increased density of capillaries or mitochondria, could occur.

RevDate: 2017-02-20
CmpDate: 2016-08-30

Roussel E, Drolet MC, Walsh-Wilkinson E, et al (2015)

Transcriptional Changes Associated with Long-Term Left Ventricle Volume Overload in Rats: Impact on Enzymes Related to Myocardial Energy Metabolism.

BioMed research international, 2015:949624.

Patients with left ventricle (LV) volume overload (VO) remain in a compensated state for many years although severe dilation is present. The myocardial capacity to fulfill its energetic demand may delay decompensation. We performed a gene expression profile, a model of chronic VO in rat LV with severe aortic valve regurgitation (AR) for 9 months, and focused on the study of genes associated with myocardial energetics. Methods. LV gene expression profile was performed in rats after 9 months of AR and compared to sham-operated controls. LV glucose and fatty acid (FA) uptake was also evaluated in vivo by positron emission tomography in 8-week AR rats treated or not with fenofibrate, an activator of FA oxidation (FAO). Results. Many LV genes associated with mitochondrial function and metabolism were downregulated in AR rats. FA β-oxidation capacity was significantly impaired as early as two weeks after AR. Treatment with fenofibrate, a PPARα agonist, normalized both FA and glucose uptake while reducing LV dilation caused by AR. Conclusion. Myocardial energy substrate preference is affected early in the evolution of LV-VO cardiomyopathy. Maintaining a relatively normal FA utilization in the myocardium could translate into less glucose uptake and possibly lesser LV remodeling.

RevDate: 2018-03-13
CmpDate: 2018-01-23

He S, Lu J, Jiang W, et al (2016)

The complete mitochondrial genome sequence of a cavefish Sinocyclocheilus anshuiensis (Cypriniformes: Cyprinidae).

Mitochondrial DNA. Part A, DNA mapping, sequencing, and analysis, 27(6):4256-4258.

Sinocyclocheilus anshuiensis is a special cavefish that lives in the Southwestern China with many specific regressive features, such as rudimentary eyes and scales, and loss of pigmentation. In this study, we performed sequencing and assembly of its complete mitochondrial genome. We confirmed that total length of the mitochondrion is 16 618 bp with an AT ratio of 55.4%. The complete mitochondrial genome contains 13 protein-coding genes, 22 transfer RNAs, 2 ribosomal RNAs and a 963 bp control region. Our current data provide important resources for the research of cavefish mitochondrial evolution and energy metabolism.

RevDate: 2018-01-24
CmpDate: 2017-09-12

Long Z, Zhang X, Sun Q, et al (2017)

Evolution of metabolic disorder in rats fed high sucrose or high fat diet: Focus on redox state and mitochondrial function.

General and comparative endocrinology, 242:92-100.

Glucotoxicity and lipotoxicity are major hallmarks of metabolic disorder. High consumption of fat or carbohydrate rich food is a major risk of metabolic disorder. However, the evolution of high fat or high carbohydrate diet-induced metabolic disorder is not clear. In the study, we tried to find distinguished and common ways involved in the pathogenesis of insulin resistance induced by high fat (HF) and high sucrose (HS) diet. We found that HS diet induced mild glucose intolerance (2month), followed by a "temporary non-symptom phase" (3month), and then induced significant metabolic abnormality (4month). HF diet induced an early "responsive enhancement phase" (2month), and then gradually caused severe metabolic dysfunction (3-4month). After a mild induction of mitochondrial ROS generation (2month), HS diet resulted in a "temporary non-symptom phase" (3month), and then induced a more significant mitochondrial ROS production (4month). The impairment of mitochondrial function induced by HS diet was progressive (2-4month). HF diet induced gradual mitochondrial ROS generation and hyperpolarization. HF diet induced an early "responsive enhancement" of mitochondrial function (2month), and then gradually resulted in severe decrease of mitochondrial function (3-4month). Despite the patterns of HS and HF diet-induced insulin resistance were differential, final mitochondrial ROS generation combined with mitochondrial dysfunction may be the common pathway. These findings demonstrate a novel understanding of the mechanism of insulin resistance and highlight the pivotal role of mitochondrial ROS generation and mitochondrial dysfunction in the pathogenesis of metabolic disorder.

RevDate: 2017-02-20
CmpDate: 2016-09-26

Garcia-Heredia JM, A Carnero (2015)

Decoding Warburg's hypothesis: tumor-related mutations in the mitochondrial respiratory chain.

Oncotarget, 6(39):41582-41599.

Otto Warburg observed that cancer cells derived their energy from aerobic glycolysis by converting glucose to lactate. This mechanism is in opposition to the higher energy requirements of cancer cells because oxidative phosphorylation (OxPhos) produces more ATP from glucose. Warburg hypothesized that this phenomenon occurs due to the malfunction of mitochondria in cancer cells. The rediscovery of Warburg's hypothesis coincided with the discovery of mitochondrial tumor suppressor genes that may conform to Warburg's hypothesis along with the demonstrated negative impact of HIF-1 on PDH activity and the activation of HIF-1 by oncogenic signals such as activated AKT. This work summarizes the alterations in mitochondrial respiratory chain proteins that have been identified and their involvement in cancer. Also discussed is the fact that most of the mitochondrial mutations have been found in homoplasmy, indicating a positive selection during tumor evolution, thereby supporting their causal role.

RevDate: 2017-02-20
CmpDate: 2016-05-27

Lopes-Marques M, Delgado IL, Ruivo R, et al (2015)

The Origin and Diversity of Cpt1 Genes in Vertebrate Species.

PloS one, 10(9):e0138447 pii:PONE-D-15-11874.

The Carnitine palmitoyltransferase I (Cpt1) gene family plays a crucial role in energy homeostasis since it is required for the occurrence of fatty acid β-oxidation in the mitochondria. The exact gene repertoire in different vertebrate lineages is variable. Presently, four genes are documented: Cpt1a, also known as Cpt1a1, Cpt1a2; Cpt1b and Cpt1c. The later is considered a mammalian innovation resulting from a gene duplication event in the ancestor of mammals, after the divergence of sauropsids. In contrast, Cpt1a2 has been found exclusively in teleosts. Here, we reassess the overall evolutionary relationships of Cpt1 genes using a combination of approaches, including the survey of the gene repertoire in basal gnathostome lineages. Through molecular phylogenetics and synteny studies, we find that Cpt1c is most likely a rapidly evolving orthologue of Cpt1a2. Thus, Cpt1c is present in other lineages such as cartilaginous fish, reptiles, amphibians and the coelacanth. We show that genome duplications (2R) and variable rates of sequence evolution contribute to the history of Cpt1 genes in vertebrates. Finally, we propose that loss of Cpt1b is the likely cause for the unusual energy metabolism of elasmobranch.

RevDate: 2016-12-02
CmpDate: 2016-03-07

Kassa T, Jana S, Strader MB, et al (2015)

Sickle Cell Hemoglobin in the Ferryl State Promotes βCys-93 Oxidation and Mitochondrial Dysfunction in Epithelial Lung Cells (E10).

The Journal of biological chemistry, 290(46):27939-27958.

Polymerization of intraerythrocytic deoxyhemoglobin S (HbS) is the primary molecular event that leads to hemolytic anemia in sickle cell disease (SCD). We reasoned that HbS may contribute to the complex pathophysiology of SCD in part due to its pseudoperoxidase activity. We compared oxidation reactions and the turnover of oxidation intermediates of purified human HbS and HbA. Hydrogen peroxide (H2O2) drives a catalytic cycle that includes the following three distinct steps: 1) initial oxidation of ferrous (oxy) to ferryl Hb; 2) autoreduction of the ferryl intermediate to ferric (metHb); and 3) reaction of metHb with an additional H2O2 molecule to regenerate the ferryl intermediate. Ferrous and ferric forms of both proteins underwent initial oxidation to the ferryl heme in the presence of H2O2 at equal rates. However, the rate of autoreduction of ferryl to the ferric form was slower in the HbS solutions. Using quantitative mass spectrometry and the spin trap, 5,5-dimethyl-1-pyrroline-N-oxide, we found more irreversibly oxidized βCys-93in HbS than in HbA. Incubation of the ferric or ferryl HbS with cultured lung epithelial cells (E10) induced a drop in mitochondrial oxygen consumption rate and impairment of cellular bioenergetics that was related to the redox state of the iron. Ferryl HbS induced a substantial drop in the mitochondrial transmembrane potential and increases in cytosolic heme oxygenase (HO-1) expression and mitochondrial colocalization in E10 cells. Thus, highly oxidizing ferryl Hb and heme, the product of oxidation, may be central to the evolution of vasculopathy in SCD and may suggest therapeutic modalities that interrupt heme-mediated inflammation.

RevDate: 2017-11-16
CmpDate: 2017-02-01

Bremer K, Kocha KM, Snider T, et al (2016)

Sensing and responding to energetic stress: The role of the AMPK-PGC1α-NRF1 axis in control of mitochondrial biogenesis in fish.

Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology, 199:4-12.

Remodeling the muscle metabolic machinery in mammals in response to energetic challenges depends on the energy sensor AMP-activated protein kinase (AMPK) and its ability to phosphorylate PPAR γ coactivator 1 α (PGC1α), which in turn coactivates metabolic genes through direct and indirect association with DNA-binding proteins such as the nuclear respiratory factor 1 (NRF1) (Wu et al., 1999). The integrity of this axis in fish is uncertain because PGC1α i) lacks the critical Thr177 targeted by AMPK and ii) has mutations that may preclude binding NRF1. In this study we found no evidence that AMPK regulates mitochondrial gene expression through PGC1α in zebrafish and goldfish. AICAR treatment of zebrafish blastula cells increased phosphorylation of AMPK and led to changes in transcript levels of the AMPK targets mTOR and hexokinase 2. However, we saw no increases in mRNA levels for genes associated with mitochondrial biogenesis, including PGC1α, NRF1, and COX7C, a cytochrome c oxidase subunit. Further, AMPK phosphorylated mammalian peptides of PGC1α but not the corresponding region of zebrafish or goldfish in vitro. In vivo cold acclimation of goldfish caused an increase in mitochondrial enzymes, AMP and ADP levels, however AMPK phosphorylation decreased. In fish, the NRF1-PGC1α axis may be disrupted due to insertions in fish PGC1α orthologs within the region that serves as NRF1 binding domain in mammals. Immunocopurification showed that recombinant NRF1 protein binds mammalian but not fish PGC1α. Collectively, our studies suggest that fish have a disruption in the AMPK-PGC1α-NRF1 pathway due to structural differences between fish and mammalian PGC1α.

RevDate: 2017-10-21
CmpDate: 2016-08-01

Stefano GB, Mantione KJ, Capellan L, et al (2015)

Morphine stimulates nitric oxide release in human mitochondria.

Journal of bioenergetics and biomembranes, 47(5):409-417.

The expression of morphine by plants, invertebrate, and vertebrate cells and organ systems, strongly indicates a high level of evolutionary conservation of morphine and related morphinan alkaloids as required for life. The prototype catecholamine, dopamine, serves as an essential chemical intermediate in morphine biosynthesis, both in plants and animals. We surmise that, before the emergence of specialized plant and animal cells/organ systems, primordial multi-potential cell types required selective mechanisms to limit their responsiveness to environmental cues. Accordingly, cellular systems that emerged with the potential for recruitment of the free radical gas nitric oxide (NO) as a multi-faceted autocrine/paracrine signaling molecule, were provided with extremely positive evolutionary advantages. Endogenous morphinergic signaling, in concert with NO-coupled signaling systems, has evolved as an autocrine/paracrine regulator of metabolic homeostasis, energy metabolism, mitochondrial respiration and energy production. Basic physiological processes involving morphinergic/NO-coupled regulation of mitochondrial function, with special emphasis on the cardiovascular system, are critical to all organismic survival. Key to this concept may be the phenomenon of mitochondrial enslavement in eukaryotic evolution via endogenous morphine.

RevDate: 2017-01-13
CmpDate: 2017-01-12

Roussel D, Salin K, Dumet A, et al (2015)

Oxidative phosphorylation efficiency, proton conductance and reactive oxygen species production of liver mitochondria correlates with body mass in frogs.

The Journal of experimental biology, 218(Pt 20):3222-3228.

Body size is a central biological parameter affecting most biological processes (especially energetics) and the mitochondrion is a key organelle controlling metabolism and is also the cell's main source of chemical energy. However, the link between body size and mitochondrial function is still unclear, especially in ectotherms. In this study, we investigated several parameters of mitochondrial bioenergetics in the liver of three closely related species of frog (the common frog Rana temporaria, the marsh frog Pelophylax ridibundus and the bull frog Lithobates catesbeiana). These particular species were chosen because of their differences in adult body mass. We found that mitochondrial coupling efficiency was markedly increased with animal size, which led to a higher ATP production (+70%) in the larger frogs (L. catesbeiana) compared with the smaller frogs (R. temporaria). This was essentially driven by a strong negative dependence of mitochondrial proton conductance on body mass. Liver mitochondria from the larger frogs (L. catesbeiana) displayed 50% of the proton conductance of mitochondria from the smaller frogs (R. temporaria). Contrary to our prediction, the low mitochondrial proton conductance measured in L. catesbeiana was not associated with higher reactive oxygen species production. Instead, liver mitochondria from the larger individuals produced significantly lower levels of radical oxygen species than those from the smaller frogs. Collectively, the data show that key bioenergetics parameters of mitochondria (proton leak, ATP production efficiency and radical oxygen species production) are correlated with body mass in frogs. This research expands our understanding of the relationship between mitochondrial function and the evolution of allometric scaling in ectotherms.

RevDate: 2016-03-01
CmpDate: 2015-12-15

Lane N, K Powell (2015)

Nick Lane: Unearthing the first cellular innovations.

The Journal of cell biology, 210(5):684-685.

RevDate: 2018-05-10
CmpDate: 2018-02-02

Chen L, Song X, Chen X, et al (2016)

The complete mitochondrial genome of the Pundamilia nyererei (Perciformes, Cichlidae).

Mitochondrial DNA. Part A, DNA mapping, sequencing, and analysis, 27(5):3567-3568.

Pundamilia nyererei (Perciformes, Cichlidae) is a member of Cichlid fishes that lives in the Great Lakes of East Africa. Fishes of the Cichlidae family can adapt spectacular trophic radiations and provide good potential examples of vertebrate adaptive radiations. Here, we firstly assembled the complete mitochondrial genome (mitogenome) of Pundamilia nyererei. The mitgenome was 16 761 bp in length, including 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes and 1 putative control region. Most of these protein-coding genes started with a traditional ATG codon except for COX1, which initiated with an infrequent start codon GTG instead, and terminated with the mitochondrial stop codon (TAA/AGG/AGA) or a single T base. The mitogenome structural organization is identical to other Cichlid fish. The overall GC content is 45.25%, which is lower than the AT content. According to these new determined mitogenome sequences and 10 other species under the same family or order, we have constructed the species phylogenetic tree to verify the accuracy of newly assembled mitogenome sequences. We accept that by taking the advantage of full mitogenome, we can address taxonomic issue and study the related evolutionary events. Our current data are going to provide important resources for the research of Cichlid fishes mitochondrial evolution and energy metabolism.

RevDate: 2015-09-01
CmpDate: 2015-11-20

Matta CF, L Massa (2015)

Energy Equivalence of Information in the Mitochondrion and the Thermodynamic Efficiency of ATP Synthase.

Biochemistry, 54(34):5376-5378.

Half a century ago, Johnson and Knudsen resolved the puzzle of the apparent low efficiency of the kidney (∼ 0.5%) compared to most other bodily organs (∼ 40%) by taking into account the entropic cost of ion sorting, the principal function of this organ. Similarly, it is shown that the efficiency of energy transduction of the chemiosmotic proton-motive force by ATP synthase is closer to 90% instead of the oft-quoted textbook value of only 60% when information theoretic considerations are applied to the mitochondrion. This high efficiency is consistent with the mechanical energy transduction of ATP synthase known to be close to the 100% thermodynamic limit. It would have been wasteful for evolution to maximize the mechanical energy transduction to 100% while wasting 40% of the chemiosmotic free energy in the conversion of the proton-motive force into mechanical work before being captured as chemical energy in adenosine 5'-triphosphate.

RevDate: 2017-02-20
CmpDate: 2016-04-28

Salin K, Auer SK, Rey B, et al (2015)

Variation in the link between oxygen consumption and ATP production, and its relevance for animal performance.

Proceedings. Biological sciences, 282(1812):20151028.

It is often assumed that an animal's metabolic rate can be estimated through measuring the whole-organism oxygen consumption rate. However, oxygen consumption alone is unlikely to be a sufficient marker of energy metabolism in many situations. This is due to the inherent variability in the link between oxidation and phosphorylation; that is, the amount of adenosine triphosphate (ATP) generated per molecule of oxygen consumed by mitochondria (P/O ratio). In this article, we describe how the P/O ratio can vary within and among individuals, and in response to a number of environmental parameters, including diet and temperature. As the P/O ratio affects the efficiency of cellular energy production, its variability may have significant consequences for animal performance, such as growth rate and reproductive output. We explore the adaptive significance of such variability and hypothesize that while a reduction in the P/O ratio is energetically costly, it may be associated with advantages in terms of somatic maintenance through reduced production of reactive oxygen species. Finally, we discuss how considering variation in mitochondrial efficiency, together with whole-organism oxygen consumption, can permit a better understanding of the relationship between energy metabolism and life history for studies in evolutionary ecology.

RevDate: 2015-08-06
CmpDate: 2016-05-06

Chandel NS (2015)

Evolution of Mitochondria as Signaling Organelles.

Cell metabolism, 22(2):204-206.

Mitochondria have primarily been viewed as bioenergetic and biosynthetic organelles that autonomously co-exist within the cell. However, the past two decades have provided evidence that mitochondria function as signaling organelles, constantly communicating with the cytosol to initiate biological events under homeostatic and stress conditions. Thus, the signaling function of the mitochondria may have been selected by nature from the inception of the early eukaryote, as discussed in this essay.

RevDate: 2015-06-13
CmpDate: 2016-03-10

Hubbard WJ, Bland KI, IH Chaudry (2015)

The ERRor of Our Ways: Estrogen-Related Receptors are About Energy, Not Hormones, and are Potential New Targets for Trauma and Shock.

Shock (Augusta, Ga.), 44(1):3-15.

As with sharks and horseshoe crabs, some designs of nature need only minor evolutionary adjustments during the millennia to remain superbly adapted. Such is the case at the molecular level for the nuclear receptors (NRs), which seem to have originated concomitantly with the earliest metazoan lineage of animals. A wide array of NRs persists today throughout all animal phyla with many different functions, yet they share a highly conserved protein structure, a testament to their having evolved through numerous gene duplications. Of particular interest for this readership are the estrogen-related receptors (ERRs), which have significant supportive roles in energy creation and regulation, mitochondrial function and biogenesis, development, tissue repair, hypoxia, and cancer. Thus, placed at the nexus of energetics and homeostasis, ERR (in association with the coregulatory molecules peroxisome proliferator-activated receptor-γ coactivator-1α and -β) can facilitate repair from injury and adaptations to stressful environments. Whereas it is curious that ERRs and some other NRs exist as "orphans" by virtue of having no known cognate ligand, increasing interest in the estrogen receptor has led to the development of synthetic ligands and screening for naturally occurring molecules, either capable of modulating ERR activity. Thus, what is needed now is a nomenclature update for the ERR to focus the mind on energetics and metabolism, the most compromised and crucial systems after trauma and shock.

RevDate: 2017-11-16
CmpDate: 2016-06-21

Virmani A, Pinto L, Bauermann O, et al (2015)

The Carnitine Palmitoyl Transferase (CPT) System and Possible Relevance for Neuropsychiatric and Neurological Conditions.

Molecular neurobiology, 52(2):826-836.

The carnitine palmitoyl transferase (CPT) system is a multiprotein complex with catalytic activity localized within a core represented by CPT1 and CPT2 in the outer and inner membrane of the mitochondria, respectively. Two proteins, the acyl-CoA synthase and a translocase also form part of this system. This system is crucial for the mitochondrial beta-oxidation of long-chain fatty acids. CPT1 has two well-known isoforms, CPT1a and CPT1b. CPT1a is the hepatic isoform and CPT1b is typically muscular; both are normally utilized by the organism for metabolic processes throughout the body. There is a strong evidence for their involvement in various disease states, e.g., metabolic syndrome, cardiovascular diseases, and in diabetes mellitus type 2. Recently, a new, third isoform of CPT was described, CPT1c. This is a neuronal isoform and is prevalently localized in brain regions such as hypothalamus, amygdala, and hippocampus. These brain regions play an important role in control of food intake and neuropsychiatric and neurological diseases. CPT activity has been implicated in several neurological and social diseases mainly related to the alteration of insulin equilibrium in the brain. These pathologies include Parkinson's disease, Alzheimer's disease, and schizophrenia. Evolution of both Parkinson's disease and Alzheimer's disease is in some way linked to brain insulin and related metabolic dysfunctions with putative links also with the diabetes type 2. Studies show that in the CNS, CPT1c affects ceramide levels, endocannabionoids, and oxidative processes and may play an important role in various brain functions such as learning.

RevDate: 2017-11-16
CmpDate: 2016-05-17

Ilkun O, Wilde N, Tuinei J, et al (2015)

Antioxidant treatment normalizes mitochondrial energetics and myocardial insulin sensitivity independently of changes in systemic metabolic homeostasis in a mouse model of the metabolic syndrome.

Journal of molecular and cellular cardiology, 85:104-116.

Cardiac dysfunction in obesity is associated with mitochondrial dysfunction, oxidative stress and altered insulin sensitivity. Whether oxidative stress directly contributes to myocardial insulin resistance remains to be determined. This study tested the hypothesis that ROS scavenging will improve mitochondrial function and insulin sensitivity in the hearts of rodent models with varying degrees of insulin resistance and hyperglycemia. The catalytic antioxidant MnTBAP was administered to the uncoupling protein-diphtheria toxin A (UCP-DTA) mouse model of insulin resistance (IR) and obesity, at early and late time points in the evolution of IR, and to db/db mice with severe obesity and type-two diabetes. Mitochondrial function was measured in saponin-permeabilized cardiac fibers. Aconitase activity and hydrogen peroxide emission were measured in isolated mitochondria. Insulin-stimulated glucose oxidation, glycolysis and fatty acid oxidation rates were measured in isolated working hearts, and 2-deoxyglucose uptake was measured in isolated cardiomyocytes. Four weeks of MnTBAP attenuated glucose intolerance in 13-week-old UCP-DTA mice but was without effect in 24-week-old UCP-DTA mice and in db/db mice. Despite the absence of improvement in the systemic metabolic milieu, MnTBAP reversed cardiac mitochondrial oxidative stress and improved mitochondrial bioenergetics by increasing ATP generation and reducing mitochondrial uncoupling in all models. MnTBAP also improved myocardial insulin mediated glucose metabolism in 13 and 24-week-old UCP-DTA mice. Pharmacological ROS scavenging improves myocardial energy metabolism and insulin responsiveness in obesity and type 2 diabetes via direct effects that might be independent of changes in systemic metabolism.

RevDate: 2017-11-16
CmpDate: 2015-12-28

Stefano GB, RM Kream (2015)

Hypoxia defined as a common culprit/initiation factor in mitochondrial-mediated proinflammatory processes.

Medical science monitor : international medical journal of experimental and clinical research, 21:1478-1484 pii:894437.

In mammals and invertebrates, the activities of neuro- and immuno-competent cells, e.g., glia, which are present in nervous tissues, are deemed of critical importance to normative neuronal function. The responsiveness of invertebrate and vertebrate immuno-competent glia to a common set of signal molecules, such as nitric oxide and endogenous morphine, is functionally linked to physiologically driven innate immunological and neuronal activities. Importantly, the presence of a common, evolutionarily conserved, set of signal molecules in comparative animal groups strongly suggests an expansive intermediate metabolic profile dependent on high output mitochondrial ATP production and utilization. Normative bidirectional neural-immune communication across invertebrate and vertebrate species requires common anatomical and biochemical substrates and pathways involved in energy production and mitochondrial integrity. Within this closed-loop system, abnormal perturbation of the respective tissue functions will have profound ramifications in functionally altering associated nervous and vascular systems and it is highly likely that the initial trigger to the induction of a physiologically debilitating pro-inflammatory state is a micro-environmental hypoxic event. This is surmised by the need for an unwavering constant oxygen supply. In this case, temporal perturbations of normative oxygen tension may be tolerated for short, but not extended, periods and ischemic/hypoxic perturbations in oxygen delivery represent significant physiological challenges to overall cellular and multiple organ system viability. Hence, hypoxic triggering of multiple pro-inflammatory events, if not corrected, will promote pathophysiological amplification leading to a deleterious cascade of bio-senescent cellular and molecular signaling pathways, which converge to markedly impair mitochondrial energy utilization and ATP production.

RevDate: 2017-10-14
CmpDate: 2016-04-20

Oelkrug R, Polymeropoulos ET, M Jastroch (2015)

Brown adipose tissue: physiological function and evolutionary significance.

Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology, 185(6):587-606.

In modern eutherian (placental) mammals, brown adipose tissue (BAT) evolved as a specialized thermogenic organ that is responsible for adaptive non-shivering thermogenesis (NST). For NST, energy metabolism of BAT mitochondria is increased by activation of uncoupling protein 1 (UCP1), which dissipates the proton motive force as heat. Despite the presence of UCP1 orthologues prior to the divergence of teleost fish and mammalian lineages, UCP1's significance for thermogenic adipose tissue emerged at later evolutionary stages. Recent studies on the presence of BAT in metatherians (marsupials) and eutherians of the afrotherian clade provide novel insights into the evolution of adaptive NST in mammals. In particular studies on the 'protoendothermic' lesser hedgehog tenrec (Afrotheria) suggest an evolutionary scenario linking BAT to the onset of eutherian endothermy. Here, we review the physiological function and distribution of BAT in an evolutionary context by focusing on the latest research on phylogenetically distinct species.

RevDate: 2017-12-20
CmpDate: 2017-06-06

Xavier JM, Rodrigues CM, S Solá (2016)

Mitochondria: Major Regulators of Neural Development.

The Neuroscientist : a review journal bringing neurobiology, neurology and psychiatry, 22(4):346-358.

Mitochondria are organelles derived from primitive symbiosis between archeon ancestors and prokaryotic α-proteobacteria species, which lost the capacity of synthetizing most proteins encoded the bacterial DNA, along the evolutionary process of eukaryotes. Nowadays, mitochondria are constituted by small circular mitochondrial DNA of 16 kb, responsible for the control of several proteins, including polypeptides of the electron transport chain. Throughout evolution, these organelles acquired the capacity of regulating energy production and metabolism, thus becoming central modulators of cell fate. In fact, mitochondria are crucial for a variety of cellular processes, including adenosine triphosphate production by oxidative phosphorylation, intracellular Ca(2+) homeostasis, generation of reactive oxygen species, and also cellular specialization in a variety of tissues that ultimately relies on specific mitochondrial specialization and maturation. In this review, we discuss recent evidence extending the importance of mitochondrial function and energy metabolism to the context of neuronal development and adult neurogenesis.

RevDate: 2016-11-09
CmpDate: 2015-08-27

Levin L, D Mishmar (2015)

A genetic view of the mitochondrial role in ageing: killing us softly.

Advances in experimental medicine and biology, 847:89-106.

In contrast to the nuclear genome, the mitochondrial DNA (mtDNA) is maternally inherited and resides in multiple cellular copies that may vary in sequence (heteroplasmy). Although the interaction between mtDNA and nuclear DNA-encoded factors (mito-nuclear interaction) is vital, the mtDNA accumulates mutations an order of magnitude faster than the nuclear genome both during evolution and during the lifetime of the individual, thus requiring tight mito-nuclear co-evolution. These unique features drew the attention of many to suggest a role for the mitochondria in ageing. Although an excess of mtDNA mutations has been found in aged humans and animal models, most of these mutations had minor functional potential. Moreover, there are mtDNA mutations that recur in aged humans, but do not have any clear functionality. Nevertheless, accumulation of recurrent private mutations with minor functionality in the fast-ageing, mtDNA polymerase mutated mice (Pol-gamma), suggested that these very mtDNA alterations participate in ageing. This introduces a paradox: how would either single or recurrent mutations with negligible functionality play a role in a major chronic phenotype such as ageing?Here, we propose a hypothesis to partially resolve this paradox: accumulation of mitochondrial mutations with subtle functionality, which was overlooked by the mechanisms of selection, supplemented by slightly affected fusion-fission cycles, will hamper mitochondrial functional complementation within cells, disrupt mito-nuclear interactions and lead to ageing. Since certain mito-nuclear genotypes are less functionally compatible than others, and since the mtDNA and the nuclear genome segregate independently among generations, mild functionality of mutations will have differential effect on individuals in the population thus explaining the large variability in the ageing phenotype even within ethnic groups. We emphasize the role of recurrent mtDNA mutations with functional potential during evolution and during the lifetime of the individual.

RevDate: 2017-02-20
CmpDate: 2016-04-29

Booth A, WF Doolittle (2015)

Eukaryogenesis, how special really?.

Proceedings of the National Academy of Sciences of the United States of America, 112(33):10278-10285.

Eukaryogenesis is widely viewed as an improbable evolutionary transition uniquely affecting the evolution of life on this planet. However, scientific and popular rhetoric extolling this event as a singularity lacks rigorous evidential and statistical support. Here, we question several of the usual claims about the specialness of eukaryogenesis, focusing on both eukaryogenesis as a process and its outcome, the eukaryotic cell. We argue in favor of four ideas. First, the criteria by which we judge eukaryogenesis to have required a genuinely unlikely series of events 2 billion years in the making are being eroded by discoveries that fill in the gaps of the prokaryote:eukaryote "discontinuity." Second, eukaryogenesis confronts evolutionary theory in ways not different from other evolutionary transitions in individuality; parallel systems can be found at several hierarchical levels. Third, identifying which of several complex cellular features confer on eukaryotes a putative richer evolutionary potential remains an area of speculation: various keys to success have been proposed and rejected over the five-decade history of research in this area. Fourth, and perhaps most importantly, it is difficult and may be impossible to eliminate eukaryocentric bias from the measures by which eukaryotes as a whole are judged to have achieved greater success than prokaryotes as a whole. Overall, we question whether premises of existing theories about the uniqueness of eukaryogenesis and the greater evolutionary potential of eukaryotes have been objectively formulated and whether, despite widespread acceptance that eukaryogenesis was "special," any such notion has more than rhetorical value.

RevDate: 2015-05-27
CmpDate: 2016-01-27

Kake-Guena SA, Touisse K, Vergilino R, et al (2015)

Assessment of mitochondrial functions in Daphnia pulex clones using high-resolution respirometry.

Journal of experimental zoology. Part A, Ecological genetics and physiology, 323(5):292-300.

The objectives of our study were to adapt a method to measure mitochondrial function in intact mitochondria from the small crustacean Daphnia pulex and to validate if this method was sensitive enough to characterize mitochondrial metabolism in clones of the pulex complex differing in ploidy levels, mitochondrial DNA haplotypes, and geographic origins. Daphnia clones belonging to the Daphnia pulex complex represent a powerful model to delineate the link between mitochondrial DNA evolution and mitochondrial phenotypes, as single genotypes with divergent mtDNA can be grown under various experimental conditions. Our study included two diploid clones from temperate environments and two triploid clones from subarctic environments. The whole animal permeabilization and measurement of respiration with high-resolution respirometry enabled the measurement of the functional capacity of specific mitochondrial complexes in four clones. When expressing the activity as ratios, our method detected significant interclonal variations. In the triploid subarctic clone from Kuujjurapik, a higher proportion of the maximal physiological oxidative phosphorylation (OXPHOS) capacity of mitochondria was supported by complex II, and a lower proportion by complex I. The triploid subarctic clone from Churchill (Manitoba) showed the lowest proportion of the maximal OXPHOS supported by complex II. Additional studies are required to determine if these differences in mitochondrial functions are related to differences in mitochondrial haplotypes or ploidy level and if they might be associated with fitness divergences and therefore selective value.

RevDate: 2017-02-20
CmpDate: 2015-11-16

Kotakis C (2015)

Non-coding RNAs' partitioning in the evolution of photosynthetic organisms via energy transduction and redox signaling.

RNA biology, 12(1):101-104.

Ars longa, vita brevis -Hippocrates Chloroplasts and mitochondria are genetically semi-autonomous organelles inside the plant cell. These constructions formed after endosymbiosis and keep evolving throughout the history of life. Experimental evidence is provided for active non-coding RNAs (ncRNAs) in these prokaryote-like structures, and a possible functional imprinting on cellular electrophysiology by those RNA entities is described. Furthermore, updated knowledge on RNA metabolism of organellar genomes uncovers novel inter-communication bridges with the nucleus. This class of RNA molecules is considered as a unique ontogeny which transforms their biological role as a genetic rheostat into a synchronous biochemical one that can affect the energetic charge and redox homeostasis inside cells. A hypothesis is proposed where such modulation by non-coding RNAs is integrated with genetic signals regulating gene transfer. The implications of this working hypothesis are discussed, with particular reference to ncRNAs involvement in the organellar and nuclear genomes evolution since their integrity is functionally coupled with redox signals in photosynthetic organisms.

RevDate: 2017-02-20
CmpDate: 2015-08-21

Bai X, Kim TI, Lee JY, et al (2015)

Identification and molecular characterization of Parkin in Clonorchis sinensis.

The Korean journal of parasitology, 53(1):65-75.

Clonorchis sinensis habitating in the bile duct of mammals causes clonorchiasis endemic in East Asian countries. Parkin is a RING-between-RING protein and has E3-ubiquitin ligase activity catalyzing ubiquitination and degradation of substrate proteins. A cDNA clone of C. sinensis was predicted to encode a polypeptide homologous to parkin (CsParkin) including 5 domains (Ubl, RING0, RING1, IBR, and RING2). The cysteine and histidine residues binding to Zn(2+) were all conserved and participated in formation of tertiary structural RINGs. Conserved residues were also an E2-binding site in RING1 domain and a catalytic cysteine residue in the RING2 domain. Native CsParkin was determined to have an estimated molecular weight of 45.7 kDa from C. sinensis adults by immunoblotting. CsParkin revealed E3-ubiquitin ligase activity and higher expression in metacercariae than in adults. CsParkin was localized in the locomotive and male reproductive organs of C. sinensis adults, and extensively in metacercariae. Parkin has been found to participate in regulating mitochondrial function and energy metabolism in mammalian cells. From these results, it is suggested that CsParkin play roles in energy metabolism of the locomotive organs, and possibly in protein metabolism of the reproductive organs of C. sinensis.

RevDate: 2017-09-22
CmpDate: 2015-05-19

Diaz-Muñoz MD, Bell SE, Fairfax K, et al (2015)

The RNA-binding protein HuR is essential for the B cell antibody response.

Nature immunology, 16(4):415-425.

Post-transcriptional regulation of mRNA by the RNA-binding protein HuR (encoded by Elavl1) is required in B cells for the germinal center reaction and for the production of class-switched antibodies in response to thymus-independent antigens. Transcriptome-wide examination of RNA isoforms and their abundance and translation in HuR-deficient B cells, together with direct measurements of HuR-RNA interactions, revealed that HuR-dependent splicing of mRNA affected hundreds of transcripts, including that encoding dihydrolipoamide S-succinyltransferase (Dlst), a subunit of the 2-oxoglutarate dehydrogenase (α-KGDH) complex. In the absence of HuR, defective mitochondrial metabolism resulted in large amounts of reactive oxygen species and B cell death. Our study shows how post-transcriptional processes control the balance of energy metabolism required for the proliferation and differentiation of B cells.

RevDate: 2015-03-16
CmpDate: 2015-06-15

Wilson DF (2015)

Programming and regulation of metabolic homeostasis.

American journal of physiology. Endocrinology and metabolism, 308(6):E506-17.

Evidence is presented that the rate and equilibrium constants in mitochondrial oxidative phosphorylation set and maintain metabolic homeostasis in eukaryotic cells. These internal constants determine the energy state ([ATP]/[ADP][Pi]), and the energy state maintains homeostasis through a bidirectional sensory/signaling control network that reaches every aspect of cellular metabolism. The energy state is maintained with high precision (to ∼1 part in 10(10)), and the control system can respond to transient changes in energy demand (ATP utilization) of more than 100 times the resting rate. Epigenetic and environmental factors are able to "fine-tune" the programmed set point over a narrow range to meet the special needs associated with cell differentiation and chronic changes in metabolic requirements. The result is robust across-platform control of metabolism, which is essential to cellular differentiation and the evolution of complex organisms. A model of oxidative phosphorylation is presented, for which the steady-state rate expression has been derived and computer programmed. The behavior of oxidative phosphorylation predicted by the model is shown to fit the experimental data available for isolated mitochondria as well as for cells and tissues. This includes measurements from several different mammalian tissues as well as from insect flight muscle and plants. The respiratory chain and oxidative phosphorylation is remarkably similar for all higher plants and animals. This is consistent with the efficient synthesis of ATP and precise control of metabolic homeostasis provided by oxidative phosphorylation being a key to cellular differentiation and the evolution of structures with specialized function.

RevDate: 2017-02-20
CmpDate: 2016-05-13

Nývltová E, Stairs CW, Hrdý I, et al (2015)

Lateral gene transfer and gene duplication played a key role in the evolution of Mastigamoeba balamuthi hydrogenosomes.

Molecular biology and evolution, 32(4):1039-1055.

Lateral gene transfer (LGT) is an important mechanism of evolution for protists adapting to oxygen-poor environments. Specifically, modifications of energy metabolism in anaerobic forms of mitochondria (e.g., hydrogenosomes) are likely to have been associated with gene transfer from prokaryotes. An interesting question is whether the products of transferred genes were directly targeted into the ancestral organelle or initially operated in the cytosol and subsequently acquired organelle-targeting sequences. Here, we identified key enzymes of hydrogenosomal metabolism in the free-living anaerobic amoebozoan Mastigamoeba balamuthi and analyzed their cellular localizations, enzymatic activities, and evolutionary histories. Additionally, we characterized 1) several canonical mitochondrial components including respiratory complex II and the glycine cleavage system, 2) enzymes associated with anaerobic energy metabolism, including an unusual D-lactate dehydrogenase and acetyl CoA synthase, and 3) a sulfate activation pathway. Intriguingly, components of anaerobic energy metabolism are present in at least two gene copies. For each component, one copy possesses an mitochondrial targeting sequence (MTS), whereas the other lacks an MTS, yielding parallel cytosolic and hydrogenosomal extended glycolysis pathways. Experimentally, we confirmed that the organelle targeting of several proteins is fully dependent on the MTS. Phylogenetic analysis of all extended glycolysis components suggested that these components were acquired by LGT. We propose that the transformation from an ancestral organelle to a hydrogenosome in the M. balamuthi lineage involved the lateral acquisition of genes encoding extended glycolysis enzymes that initially operated in the cytosol and that established a parallel hydrogenosomal pathway after gene duplication and MTS acquisition.

RevDate: 2014-12-16
CmpDate: 2015-09-09

Wang SP, Yang H, Wu JW, et al (2014)

Metabolism as a tool for understanding human brain evolution: lipid energy metabolism as an example.

Journal of human evolution, 77:41-49.

Genes and the environment both influence the metabolic processes that determine fitness. To illustrate the importance of metabolism for human brain evolution and health, we use the example of lipid energy metabolism, i.e. the use of fat (lipid) to produce energy and the advantages that this metabolic pathway provides for the brain during environmental energy shortage. We briefly describe some features of metabolism in ancestral organisms, which provided a molecular toolkit for later development. In modern humans, lipid energy metabolism is a regulated multi-organ pathway that links triglycerides in fat tissue to the mitochondria of many tissues including the brain. Three important control points are each suppressed by insulin. (1) Lipid reserves in adipose tissue are released by lipolysis during fasting and stress, producing fatty acids (FAs) which circulate in the blood and are taken up by cells. (2) FA oxidation. Mitochondrial entry is controlled by carnitine palmitoyl transferase 1 (CPT1). Inside the mitochondria, FAs undergo beta oxidation and energy production in the Krebs cycle and respiratory chain. (3) In liver mitochondria, the 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) pathway produces ketone bodies for the brain and other organs. Unlike most tissues, the brain does not capture and metabolize circulating FAs for energy production. However, the brain can use ketone bodies for energy. We discuss two examples of genetic metabolic traits that may be advantageous under most conditions but deleterious in others. (1) A CPT1A variant prevalent in Inuit people may allow increased FA oxidation under nonfasting conditions but also predispose to hypoglycemic episodes. (2) The thrifty genotype theory, which holds that energy expenditure is efficient so as to maximize energy stores, predicts that these adaptations may enhance survival in periods of famine but predispose to obesity in modern dietary environments.

RevDate: 2016-02-18
CmpDate: 2015-08-20

Wang M, Ma X, Shen J, et al (2014)

The ongoing story: the mitochondria pyruvate carrier 1 in plant stress response in Arabidopsis.

Plant signaling & behavior, 9(10):e973810.

Abscisic acid (ABA) is an important regulator of guard cell ion channels and stomatal movements in response to drought stress. Pyruvate is the final product of glycolysis in the cytosol, and could be transported by mitochondrial pyruvate carriers (MPCs) into mitochondrion for consequent cellular substance and energy metabolism. We recently characterized the first putative mitochondrial pyruvate carrier, NRGA1, in planta, and found that this small protein is involved in the negative regulation of drought and ABA induced guard cell signaling in Arabidopsis thaliana. The findings revealed a probable link between mitochondrial pyruvate transport and guard cell signaling. It has also been shown that NRGA1 protein product was directed to the mitochondria, and co-expression of MPC1 and NRGA1 functionally complement the absence of a native pyruvate transport protein in yeast. Here, we further demonstrated that MPC1 showed similar sub-cellular localization pattern to NRGA1. Quantitative RT-PCR analysis showed that the transcription of both NRGA1 and MPC1 were induced by pyruvate or ABA, and pyruvate strengthened the ABA induced transcription of these 2 genes. The similarity in subcellular localization and gene expression to ABA strongly suggests that MPC1 may associate with NRGA1 for mitochondrial pyruvate transport and is involved in ABA mediated stomatal movements in Arabidopsis.

RevDate: 2017-02-20
CmpDate: 2015-08-05

Degli Esposti M (2014)

Bioenergetic evolution in proteobacteria and mitochondria.

Genome biology and evolution, 6(12):3238-3251 pii:evu257.

Mitochondria are the energy-producing organelles of our cells and derive from bacterial ancestors that became endosymbionts of microorganisms from a different lineage, together with which they formed eukaryotic cells. For a long time it has remained unclear from which bacteria mitochondria actually evolved, even if these organisms in all likelihood originated from the α lineage of proteobacteria. A recent article (Degli Esposti M, et al. 2014. Evolution of mitochondria reconstructed from the energy metabolism of living bacteria. PLoS One 9:e96566) has presented novel evidence indicating that methylotrophic bacteria could be among the closest living relatives of mitochondrial ancestors. Methylotrophs are ubiquitous bacteria that live on single carbon sources such as methanol and methane; in the latter case they are called methanotrophs. In this review, I examine their possible ancestry to mitochondria within a survey of the common features that can be found in the central and terminal bioenergetic systems of proteobacteria and mitochondria. I also discuss previously overlooked information on methanotrophic bacteria, in particular their intracytoplasmic membranes resembling mitochondrial cristae and their capacity of establishing endosymbiotic relationships with invertebrate animals and archaic plants. This information appears to sustain the new idea that mitochondrial ancestors could be related to extant methanotrophic proteobacteria, a possibility that the genomes of methanotrophic endosymbionts will hopefully clarify.

RevDate: 2017-02-20
CmpDate: 2015-12-17

Wang Z, M Wu (2014)

Phylogenomic reconstruction indicates mitochondrial ancestor was an energy parasite.

PloS one, 9(10):e110685 pii:PONE-D-14-31548.

Reconstruction of mitochondrial ancestor has great impact on our understanding of the origin of mitochondria. Previous studies have largely focused on reconstructing the last common ancestor of all contemporary mitochondria (proto-mitochondria), but not on the more informative pre-mitochondria (the last common ancestor of mitochondria and their alphaproteobacterial sister clade). Using a phylogenomic approach and leveraging on the increased taxonomic sampling of alphaproteobacterial and eukaryotic genomes, we reconstructed the metabolisms of both proto-mitochondria and pre-mitochondria. Our reconstruction depicts a more streamlined proto-mitochondrion than these predicted by previous studies, and revealed several novel insights into the mitochondria-derived eukaryotic metabolisms including the lipid metabolism. Most strikingly, pre-mitochondrion was predicted to possess a plastid/parasite type of ATP/ADP translocase that imports ATP from the host, which posits pre-mitochondrion as an energy parasite that directly contrasts with the current role of mitochondria as the cell's energy producer. In addition, pre-mitochondrion was predicted to encode a large number of flagellar genes and several cytochrome oxidases functioning under low oxygen level, strongly supporting the previous finding that the mitochondrial ancestor was likely motile and capable of oxidative phosphorylation under microoxic condition.

RevDate: 2017-02-20
CmpDate: 2015-04-17

Haag KL, James TY, Pombert JF, et al (2014)

Evolution of a morphological novelty occurred before genome compaction in a lineage of extreme parasites.

Proceedings of the National Academy of Sciences of the United States of America, 111(43):15480-15485.

Intracellular parasitism results in extreme adaptations, whose evolutionary history is difficult to understand, because the parasites and their known free-living relatives are so divergent from one another. Microsporidia are intracellular parasites of humans and other animals, which evolved highly specialized morphological structures, but also extreme physiologic and genomic simplification. They are suggested to be an early-diverging branch on the fungal tree, but comparisons to other species are difficult because their rates of molecular evolution are exceptionally high. Mitochondria in microsporidia have degenerated into organelles called mitosomes, which have lost a genome and the ability to produce ATP. Here we describe a gut parasite of the crustacean Daphnia that despite having remarkable morphological similarity to the microsporidia, has retained genomic features of its fungal ancestors. This parasite, which we name Mitosporidium daphniae gen. et sp. nov., possesses a mitochondrial genome including genes for oxidative phosphorylation, yet a spore stage with a highly specialized infection apparatus--the polar tube--uniquely known only from microsporidia. Phylogenomics places M. daphniae at the root of the microsporidia. A comparative genomic analysis suggests that the reduction in energy metabolism, a prominent feature of microsporidian evolution, was preceded by a reduction in the machinery controlling cell cycle, DNA recombination, repair, and gene expression. These data show that the morphological features unique to M. daphniae and other microsporidia were already present before the lineage evolved the extreme host metabolic dependence and loss of mitochondrial respiration for which microsporidia are well known.

RevDate: 2017-10-10
CmpDate: 2015-03-05

Gonçalves VF, Andreazza AC, JL Kennedy (2015)

Mitochondrial dysfunction in schizophrenia: an evolutionary perspective.

Human genetics, 134(1):13-21.

Schizophrenia (SCZ) is a severe psychiatric illness with a lifetime prevalence of 0.4 %. A disturbance of energy metabolism has been suggested as part of the etiopathogenesis of the disorder. Several lines of evidence have proposed a connection between etiopathogenesis of SCZ and human brain evolution, which was characterized by an increase in the energy requirement, demanding a co-evolution of the mitochondrial system. Mitochondria are key players in brain energy homeostasis and multiple lines of evidence suggest that the system is disrupted in SCZ. In this review, we will describe the current knowledge on pathways/system involved in the human brain evolution as well as the main theories regarding the evolutionary origin of SCZ. We will furthermore discuss the role of mitochondria in the context of brain energy metabolism and its role in the etiopathogenesis of SCZ. Understanding SCZ in the context of human brain evolution opens a new perspective to elucidate pathophysiological mechanisms involved in the origin and/or portions of the complex symptomatology of this severe mental disorder.

RevDate: 2018-04-29
CmpDate: 2015-06-23

Ju YS, Alexandrov LB, Gerstung M, et al (2014)

Origins and functional consequences of somatic mitochondrial DNA mutations in human cancer.

eLife, 3:.

Recent sequencing studies have extensively explored the somatic alterations present in the nuclear genomes of cancers. Although mitochondria control energy metabolism and apoptosis, the origins and impact of cancer-associated mutations in mtDNA are unclear. In this study, we analyzed somatic alterations in mtDNA from 1675 tumors. We identified 1907 somatic substitutions, which exhibited dramatic replicative strand bias, predominantly C > T and A > G on the mitochondrial heavy strand. This strand-asymmetric signature differs from those found in nuclear cancer genomes but matches the inferred germline process shaping primate mtDNA sequence content. A number of mtDNA mutations showed considerable heterogeneity across tumor types. Missense mutations were selectively neutral and often gradually drifted towards homoplasmy over time. In contrast, mutations resulting in protein truncation undergo negative selection and were almost exclusively heteroplasmic. Our findings indicate that the endogenous mutational mechanism has far greater impact than any other external mutagens in mitochondria and is fundamentally linked to mtDNA replication.

RevDate: 2017-02-20
CmpDate: 2015-11-30

Koumandou VL, S Kossida (2014)

Evolution of the F0F1 ATP synthase complex in light of the patchy distribution of different bioenergetic pathways across prokaryotes.

PLoS computational biology, 10(9):e1003821 pii:PCOMPBIOL-D-14-00177.

Bacteria and archaea are characterized by an amazing metabolic diversity, which allows them to persist in diverse and often extreme habitats. Apart from oxygenic photosynthesis and oxidative phosphorylation, well-studied processes from chloroplasts and mitochondria of plants and animals, prokaryotes utilize various chemo- or lithotrophic modes, such as anoxygenic photosynthesis, iron oxidation and reduction, sulfate reduction, and methanogenesis. Most bioenergetic pathways have a similar general structure, with an electron transport chain composed of protein complexes acting as electron donors and acceptors, as well as a central cytochrome complex, mobile electron carriers, and an ATP synthase. While each pathway has been studied in considerable detail in isolation, not much is known about their relative evolutionary relationships. Wanting to address how this metabolic diversity evolved, we mapped the distribution of nine bioenergetic modes on a phylogenetic tree based on 16S rRNA sequences from 272 species representing the full diversity of prokaryotic lineages. This highlights the patchy distribution of many pathways across different lineages, and suggests either up to 26 independent origins or 17 horizontal gene transfer events. Next, we used comparative genomics and phylogenetic analysis of all subunits of the F0F1 ATP synthase, common to most bacterial lineages regardless of their bioenergetic mode. Our results indicate an ancient origin of this protein complex, and no clustering based on bioenergetic mode, which suggests that no special modifications are needed for the ATP synthase to work with different electron transport chains. Moreover, examination of the ATP synthase genetic locus indicates various gene rearrangements in the different bacterial lineages, ancient duplications of atpI and of the beta subunit of the F0 subcomplex, as well as more recent stochastic lineage-specific and species-specific duplications of all subunits. We discuss the implications of the overall pattern of conservation and flexibility of the F0F1 ATP synthase genetic locus.

RevDate: 2014-09-10
CmpDate: 2015-04-08

Mentel M, Röttger M, Leys S, et al (2014)

Of early animals, anaerobic mitochondria, and a modern sponge.

BioEssays : news and reviews in molecular, cellular and developmental biology, 36(10):924-932.

The origin and early evolution of animals marks an important event in life's history. This event is historically associated with an important variable in Earth history - oxygen. One view has it that an increase in oceanic oxygen levels at the end of the Neoproterozoic Era (roughly 600 million years ago) allowed animals to become large and leave fossils. How important was oxygen for the process of early animal evolution? New data show that some modern sponges can survive for several weeks at low oxygen levels. Many groups of animals have mechanisms to cope with low oxygen or anoxia, and very often, mitochondria - organelles usually associated with oxygen - are involved in anaerobic energy metabolism in animals. It is a good time to refresh our memory about the anaerobic capacities of mitochondria in modern animals and how that might relate to the ecology of early metazoans.

RevDate: 2018-10-17
CmpDate: 2015-01-02

Hess KC, Liu J, Manfredi G, et al (2014)

A mitochondrial CO2-adenylyl cyclase-cAMP signalosome controls yeast normoxic cytochrome c oxidase activity.

FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 28(10):4369-4380.

Mitochondria, the major source of cellular energy in the form of ATP, respond to changes in substrate availability and bioenergetic demands by employing rapid, short-term, metabolic adaptation mechanisms, such as phosphorylation-dependent protein regulation. In mammalian cells, an intramitochondrial CO2-adenylyl cyclase (AC)-cyclic AMP (cAMP)-protein kinase A (PKA) pathway regulates aerobic energy production. One target of this pathway involves phosphorylation of cytochrome c oxidase (COX) subunit 4-isoform 1 (COX4i1), which modulates COX allosteric regulation by ATP. However, the role of the CO2-sAC-cAMP-PKA signalosome in regulating COX activity and mitochondrial metabolism and its evolutionary conservation remain to be fully established. We show that in Saccharomyces cerevisiae, normoxic COX activity measured in the presence of ATP is 55% lower than in the presence of ADP. Moreover, the adenylyl cyclase Cyr1 activity is present in mitochondria, and it contributes to the ATP-mediated regulation of COX through the normoxic subunit Cox5a, homologue of human COX4i1, in a bicarbonate-sensitive manner. Furthermore, we have identified 2 phosphorylation targets in Cox5a (T65 and S43) that modulate its allosteric regulation by ATP. These residues are not conserved in the Cox5b-containing hypoxic enzyme, which is not regulated by ATP. We conclude that across evolution, a CO2-sAC-cAMP-PKA axis regulates normoxic COX activity.

RevDate: 2017-11-16
CmpDate: 2015-02-02

Yang Y, Xu S, Xu J, et al (2014)

Adaptive evolution of mitochondrial energy metabolism genes associated with increased energy demand in flying insects.

PloS one, 9(6):e99120 pii:PONE-D-14-09644.

Insects are unique among invertebrates for their ability to fly, which raises intriguing questions about how energy metabolism in insects evolved and changed along with flight. Although physiological studies indicated that energy consumption differs between flying and non-flying insects, the evolution of molecular energy metabolism mechanisms in insects remains largely unexplored. Considering that about 95% of adenosine triphosphate (ATP) is supplied by mitochondria via oxidative phosphorylation, we examined 13 mitochondrial protein-encoding genes to test whether adaptive evolution of energy metabolism-related genes occurred in insects. The analyses demonstrated that mitochondrial DNA protein-encoding genes are subject to positive selection from the last common ancestor of Pterygota, which evolved primitive flight ability. Positive selection was also found in insects with flight ability, whereas no significant sign of selection was found in flightless insects where the wings had degenerated. In addition, significant positive selection was also identified in the last common ancestor of Neoptera, which changed its flight mode from direct to indirect. Interestingly, detection of more positively selected genes in indirect flight rather than direct flight insects suggested a stronger selective pressure in insects having higher energy consumption. In conclusion, mitochondrial protein-encoding genes involved in energy metabolism were targets of adaptive evolution in response to increased energy demands that arose during the evolution of flight ability in insects.

RevDate: 2015-08-05
CmpDate: 2015-06-15

Kitazoe Y, M Tanaka (2014)

Evolution of mitochondrial power in vertebrate metazoans.

PloS one, 9(6):e98188 pii:PONE-D-14-11106.

BACKGROUND: Basal metabolic rate (BMR) has a very strong body-mass (M) dependence in an individual animal group, and BMR per unit mass (msBMR) converges on a markedly narrow range even across major taxonomic groups. However, it is here a basic question in metazoan biology how much BMR per unit mitochondrion (mtBMR) changes, and then whether mtBMR can be related to the original molecular mechanism of action of mt-encoded membrane proteins (MMPs) playing a central role in cellular energy production.

Analyzing variations of amino-acid compositions of MMPs across 13 metazoan animal groups, incorporating 2022 sequences, we found a strong inverse correlation between Ser/Thr composition (STC) and hydrophobicity (HYD). A majority of animal groups showed an evolutionary pathway of a gradual increase in HYD and decrease in STC, whereas only the deuterostome lineage revealed a rapid decrease in HYD and increase in STC. The strongest correlations appeared in 5 large subunits (ND4, ND5, ND2, CO1, and CO3) undergoing dynamic conformational changes for the proton-pumping function. The pathway of the majority groups is well understood as reflecting natural selection to reduce mtBMR, since simply raising HYD in MMPs (surrounded by the lipid bilayer) weakens their mobility and strengthens their stability. On the other hand, the marked decrease in HYD of the deuterostome elevates mtBMR, but is accompanied with their instability heightening a turnover rate of mitochondria and then cells. Interestingly, cooperative networks of interhelical hydrogen-bonds between motifs involving Ser and Thr residues can enhance MMP stability.

CONCLUSION/SIGNIFICANCE: This stability enhancement lowers turnover rates of mitochondria/cells and may prolong even longevity, and was indeed founded by strong positive correlations of STC with both mtBMR and longevity. The lowest HYD and highest STC in Aves and Mammals are congruent with their very high mtBMR and long longevity.

RevDate: 2017-02-20
CmpDate: 2015-10-07

Degli Esposti M, Chouaia B, Comandatore F, et al (2014)

Evolution of mitochondria reconstructed from the energy metabolism of living bacteria.

PloS one, 9(5):e96566 pii:PONE-D-14-01346.

The ancestors of mitochondria, or proto-mitochondria, played a crucial role in the evolution of eukaryotic cells and derived from symbiotic α-proteobacteria which merged with other microorganisms - the basis of the widely accepted endosymbiotic theory. However, the identity and relatives of proto-mitochondria remain elusive. Here we show that methylotrophic α-proteobacteria could be the closest living models for mitochondrial ancestors. We reached this conclusion after reconstructing the possible evolutionary pathways of the bioenergy systems of proto-mitochondria with a genomic survey of extant α-proteobacteria. Results obtained with complementary molecular and genetic analyses of diverse bioenergetic proteins converge in indicating the pathway stemming from methylotrophic bacteria as the most probable route of mitochondrial evolution. Contrary to other α-proteobacteria, methylotrophs show transition forms for the bioenergetic systems analysed. Our approach of focusing on these bioenergetic systems overcomes the phylogenetic impasse that has previously complicated the search for mitochondrial ancestors. Moreover, our results provide a new perspective for experimentally re-evolving mitochondria from extant bacteria and in the future produce synthetic mitochondria.

RevDate: 2017-02-20
CmpDate: 2015-01-27

Lane N (2014)

Bioenergetic constraints on the evolution of complex life.

Cold Spring Harbor perspectives in biology, 6(5):a015982 pii:6/5/a015982.

All morphologically complex life on Earth, beyond the level of cyanobacteria, is eukaryotic. All eukaryotes share a common ancestor that was already a complex cell. Despite their biochemical virtuosity, prokaryotes show little tendency to evolve eukaryotic traits or large genomes. Here I argue that prokaryotes are constrained by their membrane bioenergetics, for fundamental reasons relating to the origin of life. Eukaryotes arose in a rare endosymbiosis between two prokaryotes, which broke the energetic constraints on prokaryotes and gave rise to mitochondria. Loss of almost all mitochondrial genes produced an extreme genomic asymmetry, in which tiny mitochondrial genomes support, energetically, a massive nuclear genome, giving eukaryotes three to five orders of magnitude more energy per gene than prokaryotes. The requirement for endosymbiosis radically altered selection on eukaryotes, potentially explaining the evolution of unique traits, including the nucleus, sex, two sexes, speciation, and aging.

RevDate: 2017-02-20
CmpDate: 2014-06-24

Rigas S, Daras G, Tsitsekian D, et al (2014)

Evolution and significance of the Lon gene family in Arabidopsis organelle biogenesis and energy metabolism.

Frontiers in plant science, 5:145.

Lon is the first identified ATP-dependent protease highly conserved across all kingdoms. Model plant species Arabidopsis thaliana has a small Lon gene family of four members. Although these genes share common structural features, they have distinct properties in terms of gene expression profile, subcellular targeting and substrate recognition motifs. This supports the notion that their functions under different environmental conditions are not necessarily redundant. This article intends to unravel the biological role of Lon proteases in energy metabolism and plant growth through an evolutionary perspective. Given that plants are sessile organisms exposed to diverse environmental conditions and plant organelles are semi-autonomous, it is tempting to suggest that Lon genes in Arabidopsis are paralogs. Adaptive evolution through repetitive gene duplication events of a single archaic gene led to Lon genes with complementing sets of subfunctions providing to the organism rapid adaptability for canonical development under different environmental conditions. Lon1 function is adequately characterized being involved in mitochondrial biogenesis, modulating carbon metabolism, oxidative phosphorylation and energy supply, all prerequisites for seed germination and seedling establishment. Lon is not a stand-alone proteolytic machine in plant organelles. Lon in association with other nuclear-encoded ATP-dependent proteases builds up an elegant nevertheless, tight interconnected circuit. This circuitry channels properly and accurately, proteostasis and protein quality control among the distinct subcellular compartments namely mitochondria, chloroplasts, and peroxisomes.


RJR Experience and Expertise


Robbins holds BS, MS, and PhD degrees in the life sciences. He served as a tenured faculty member in the Zoology and Biological Science departments at Michigan State University. He is currently exploring the intersection between genomics, microbial ecology, and biodiversity — an area that promises to transform our understanding of the biosphere.


Robbins has extensive experience in college-level education: At MSU he taught introductory biology, genetics, and population genetics. At JHU, he was an instructor for a special course on biological database design. At FHCRC, he team-taught a graduate-level course on the history of genetics. At Bellevue College he taught medical informatics.


Robbins has been involved in science administration at both the federal and the institutional levels. At NSF he was a program officer for database activities in the life sciences, at DOE he was a program officer for information infrastructure in the human genome project. At the Fred Hutchinson Cancer Research Center, he served as a vice president for fifteen years.


Robbins has been involved with information technology since writing his first Fortran program as a college student. At NSF he was the first program officer for database activities in the life sciences. At JHU he held an appointment in the CS department and served as director of the informatics core for the Genome Data Base. At the FHCRC he was VP for Information Technology.


While still at Michigan State, Robbins started his first publishing venture, founding a small company that addressed the short-run publishing needs of instructors in very large undergraduate classes. For more than 20 years, Robbins has been operating The Electronic Scholarly Publishing Project, a web site dedicated to the digital publishing of critical works in science, especially classical genetics.


Robbins is well-known for his speaking abilities and is often called upon to provide keynote or plenary addresses at international meetings. For example, in July, 2012, he gave a well-received keynote address at the Global Biodiversity Informatics Congress, sponsored by GBIF and held in Copenhagen. The slides from that talk can be seen HERE.


Robbins is a skilled meeting facilitator. He prefers a participatory approach, with part of the meeting involving dynamic breakout groups, created by the participants in real time: (1) individuals propose breakout groups; (2) everyone signs up for one (or more) groups; (3) the groups with the most interested parties then meet, with reports from each group presented and discussed in a subsequent plenary session.


Robbins has been engaged with photography and design since the 1960s, when he worked for a professional photography laboratory. He now prefers digital photography and tools for their precision and reproducibility. He designed his first web site more than 20 years ago and he personally designed and implemented this web site. He engages in graphic design as a hobby.

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E-mail: RJR8222@gmail.com

Collection of publications by R J Robbins

Reprints and preprints of publications, slide presentations, instructional materials, and data compilations written or prepared by Robert Robbins. Most papers deal with computational biology, genome informatics, using information technology to support biomedical research, and related matters.

Research Gate page for R J Robbins

ResearchGate is a social networking site for scientists and researchers to share papers, ask and answer questions, and find collaborators. According to a study by Nature and an article in Times Higher Education , it is the largest academic social network in terms of active users.

Curriculum Vitae for R J Robbins

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Curriculum Vitae for R J Robbins

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