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Oxidative Phosphorylation (oxidative + phosphorylation)
Kinds of Oxidative Phosphorylation Selected AbstractsThe Effects of Steroid Hormones on the Transcription of Genes Encoding Enzymes of Oxidative PhosphorylationEXPERIMENTAL PHYSIOLOGY, Issue 1 2003Klaus Scheller Regulation of energy metabolism is one of the major functions of steroid hormones. In this process, mitochondria, by way of oxidative phosphorylation, play a central role. Depending on the energy needs of the cell, on the tissue, on the developmental stage and on the intensity of the hormonal stimulus, the response can be an activation of pre-existing respiratory chain components, an increased transcription of nuclear-encoded and/or mitochondrial-encoded respiratory chain enzyme (OXPHOS) genes and of biosynthesis of the respective enzyme subunits or, in extreme cases of high energy needs, an increase in the number of mitochondria and mitochondrial DNA content per cell. Some of the hormonally regulated systems involving effects on nuclear and mitochondrial OXPHOS genes are reviewed in this paper. The possible molecular mechanisms of steroid hormone action on nuclear and mitochondrial gene transcription and possible ways of coordination of transcription in these two separate cell compartments involving direct interaction of steroid receptors with hormone response elements in nuclear OXPHOS genes and in mitochondria and induction/activation of nuclear-encoded regulatory factors affecting mitochondrial gene transcription are presented. [source] Oxidative phosphorylation in health and disease.CELL BIOCHEMISTRY AND FUNCTION, Issue 2 2006No abstract is available for this article. [source] Bioenergetics and the epigenome: Interface between the environment and genes in common diseasesDEVELOPMENTAL DISABILITIES RESEARCH REVIEW, Issue 2 2010Douglas C. Wallace Abstract Extensive efforts have been directed at using genome-wide association studies (GWAS) to identify the genes responsible for common metabolic and degenerative diseases, cancer, and aging, but with limited success. While environmental factors have been evoked to explain this conundrum, the nature of these environmental factors remains unexplained. The availability of and demands for energy constitute one of the most important aspects of the environment. The flow of energy through the cell is primarily mediated by the mitochondrion, which oxidizes reducing equivalents from hydrocarbons via acetyl-CoA, NADH + H+, and FADH2 to generate ATP through oxidative phosphorylation (OXPHOS). The mitochondrial genome encompasses hundreds of nuclear DNA (nDNA)-encoded genes plus 37 mitochondrial DNA (mtDNA)-encoded genes. Although the mtDNA has a high mutation rate, only milder, potentially adaptive mutations are introduced into the population through female oocytes. In contrast, nDNA-encoded bioenergetic genes have a low mutation rate. However, their expression is modulated by histone phosphorylation and acetylation using mitochondrially-generated ATP and acetyl-CoA, which permits increased gene expression, growth, and reproduction when calories are abundant. Phosphorylation, acetylaton, and cellular redox state also regulate most signal transduction pathways and activities of multiple transcription factors. Thus, mtDNA mutations provide heritable and stable adaptation to regional differences while mitochondrially-mediated changes in the epigenome permit reversible modulation of gene expression in response to fluctuations in the energy environment. The most common genomic changes that interface with the environment and cause complex disease must, therefore, be mitochondrial and epigenomic in origin. © 2010 Wiley-Liss, Inc. Dev Disabil Res Rev 2010;16:114,119. [source] The neurologic manifestations of mitochondrial diseaseDEVELOPMENTAL DISABILITIES RESEARCH REVIEW, Issue 2 2010Sumit Parikh Abstract The nervous system contains some of the body's most metabolically demanding cells that are highly dependent on ATP produced via mitochondrial oxidative phosphorylation. Thus, the neurological system is consistently involved in patients with mitochondrial disease. Symptoms differ depending on the part of the nervous system affected. Although almost any neurological symptom can be due to mitochondrial disease, there are select symptoms that are more suggestive of a mitochondrial problem. Certain symptoms that have become sine qua non with underlying mitochondrial cytopathies can serve as diagnostic "red-flags." Here, the typical and atypical presentations of mitochondrial disease in the nervous system are reviewed, focusing on "red flag" neurological symptoms as well as associated symptoms that can occur in, but are not specific to, mitochondrial disease. The multitudes of mitochondrial syndromes are not reviewed in-depth, though a select few are discussed in some detail. © 2010 Wiley-Liss, Inc. Dev Disabil Res Rev 2010;16:120,128. [source] Coordination of development and metabolism in the pre-midblastula transition zebrafish embryoDEVELOPMENTAL DYNAMICS, Issue 7 2008Bryce A. Mendelsohn Abstract To define the mechanisms that coordinate early embryonic development and metabolism, we have examined the response of zebrafish embryos to anoxia before the midblastula transition. Our findings reveal that anoxic pre-midblastula transition embryos slow the cell cycle, arrest before the midblastula transition and can recover normally if restored to a normoxic environment. Analyses of respiratory rates reveal that pre-midblastula transition embryos are less reliant on oxidative phosphorylation than older embryos. Interestingly, arrest in anoxia occurs despite inhibition of zygotic transcription, revealing a central role for maternal factors in the response to energy limitation. Consistent with this concept, we demonstrate that the posttranslational energy-sensing AMP-activated protein kinase pathway is activated in anoxia in pre-midblastula transition embryos. Taken together, these findings demonstrate a maternal program capable of coordinating developmental rate and metabolism in the absence of transcription-based pathways or cell cycle checkpoints. Developmental Dynamics 237:1789,1798, 2008. © 2008 Wiley-Liss, Inc. [source] The Effects of Ecstasy (MDMA) on Rat Liver BioenergeticsACADEMIC EMERGENCY MEDICINE, Issue 7 2004Daniel E. Rusyniak MD Abstract Objectives: Use of the drug ecstasy (3,4-methylenedioxymethamphetamine [MDMA]) can result in life-threatening hyperthermia. Agents that uncouple mitochondrial oxidative phosphorylation are known to cause severe hyperthermia. In the present study, the authors tested the hypothesis that MDMA directly uncouples oxidative phosphorylation in rat liver mitochondria. Methods: Effects on mitochondrial bioenergetics were assessed both in vitro and ex vivo. In vitro studies consisted of measuring the effects of MDMA (0.1,5.0 mmol/L) on states of respiration in isolated rat liver mitochondria and on mitochondrial membrane potential in a rat liver cell line. In ex vivo studies, mitochondrial rates of respiration were measured in the livers of rats one hour after treatment with MDMA (40 mg/kg subcutaneously). Results: With the in vitro mitochondrial preparations, only concentrations of 5 mmol/L MDMA showed evidence of uncoupling with a slight increase in state 4 respiration and a corresponding decrease in the respiratory control index. MDMA (0.1,5.0 mmol/L) failed to decrease the mitochondrial membrane potential in 3,3-dihexyloxacarbocyanide iodide,stained WB-344 cells after either one or 24 hours of incubation. Ex vivo rates of respiration obtained from the livers of rats one hour after treatment with MDMA (40 mg/kg subcutaneously) showed no evidence of mitochondrial uncoupling. Conclusions: These data suggest that while high concentrations of MDMA have some mild uncoupling effects in isolated mitochondria, these effects do not translate to cell culture or ex vivo studies in treated animals. These data do not support the view that the hyperthermia induced by MDMA is from a direct effect on mitochondrial oxidative phosphorylation. [source] Focused proteomics: Monoclonal antibody-based isolation of the oxidative phosphorylation machinery and detection of phosphoproteins using a fluorescent phosphoprotein gel stainELECTROPHORESIS, Issue 15 2004James Murray Abstract We have raised monoclonal antibodies capable of immunocapturing all five complexes involved in oxidative phosphorylation for evaluating their post-translational modifications. Complex I (NADH dehydrogenase), complex II (succinate dehydrogenase), complex III (cytochrome c reductase), complex IV (cytochrome c oxidase), and complex V (F1F0 ATP synthase) from bovine heart mitochondria were obtained in good yield from small amounts of tissue in more than 90% purity in one step. The composition and purity of the complexes was evaluated by Western blotting using monoclonal antibodies against individual subunits of the five complexes. In this first study, the phosphorylation state of the proteins without inducing phosphorylation or dephosphorylation was identified by using the novel Pro-Q Diamond phosphoprotein gel stain. The major phosphorylated components were the same as described before in sucrose gradient enriched complexes. In addition a few additional potential phosphoproteins were observed. Since the described monoclonal antibodies show cross reactivity to human proteins, this procedure will be a fast and efficient way of studying post-translational modifications in control and patient samples using only small amounts of tissue. [source] The mitochondrial proteome: A dynamic functional program in tissues and disease states,ENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 5 2010Robert S. Balaban Abstract The nuclear DNA transcriptional programming of the mitochondria proteome varies dramatically between tissues depending on its functional requirements. This programming generally regulates all of the proteins associated with a metabolic or biosynthetic pathway associated with a given function, essentially regulating the maximum rate of the pathway while keeping the enzymes at the same molar ratio. This may permit the same regulatory mechanisms to function at low- and high-flux capacity situations. This alteration in total protein content results in rather dramatic changes in the mitochondria proteome between tissues. A tissues mitochondria proteome also changes with disease state, in Type 1 diabetes the liver mitochondrial proteome shifts to support ATP production, urea synthesis, and fatty acid oxidation. Acute flux regulation is modulated by numerous posttranslational events that also are highly variable between tissues. The most studied posttranslational modification is protein phosphorylation, which is found all of the complexes of oxidative phosphorylation and most of the major metabolic pathways. The functional significance of these modifications is currently a major area of research along with the kinase and phosphatase regulatory network. This near ubiquitous presence of protein phosphorylations, and other posttranslational events, in the matrix suggest that not all posttranslational events have functional significance. Screening methods are being introduced to detect the active or dynamic posttranslational sites to focus attention on sites that might provide insight into regulatory mechanisms. Environ. Mol. Mutagen., 2010. Published 2010 Wiley-Liss, Inc. [source] A compendium of human mitochondrial gene expression machinery with links to diseaseENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 5 2010Timothy E. Shutt Abstract Mammalian mitochondrial DNA encodes 37 essential genes required for ATP production via oxidative phosphorylation, instability or misregulation of which is associated with human diseases and aging. Other than the mtDNA-encoded RNA species (13 mRNAs, 12S and 16S rRNAs, and 22 tRNAs), the remaining factors needed for mitochondrial gene expression (i.e., transcription, RNA processing/modification, and translation), including a dedicated set of mitochondrial ribosomal proteins, are products of nuclear genes that are imported into the mitochondrial matrix. Herein, we inventory the human mitochondrial gene expression machinery, and, while doing so, we highlight specific associations of these regulatory factors with human disease. Major new breakthroughs have been made recently in this burgeoning area that set the stage for exciting future studies on the key outstanding issue of how mitochondrial gene expression is regulated differentially in vivo. This should promote a greater understanding of why mtDNA mutations and dysfunction cause the complex and tissue-specific pathology characteristic of mitochondrial disease states and how mitochondrial dysfunction contributes to more common human pathology and aging. Environ. Mol. Mutagen., 2010. © 2010 Wiley-Liss, Inc. [source] Pseudomonas fluorescens orchestrates a fine metabolic-balancing act to counter aluminium toxicityENVIRONMENTAL MICROBIOLOGY, Issue 6 2010Joseph Lemire Summary Aluminium (Al), an environmental toxin, is known to disrupt cellular functions by perturbing iron (Fe) homeostasis. However, Fe is essential for such metabolic processes as the tricarboxylic acid (TCA) cycle and oxidative phosphorylation, the two pivotal networks that mediate ATP production during aerobiosis. To counter the Fe conundrum induced by Al toxicity, Pseudomonas fluorescens utilizes isocitrate lyase and isocitrate dehydrogenase-NADP dependent to metabolize citrate when confronted with an ineffective aconitase provoked by Al stress. By invoking fumarase C, a hydratase devoid of Fe, this microbe is able to generate essential metabolites. To compensate for the severely diminished enzymes like Complex I, Complex II and Complex IV, the upregulation of a H2O-generating NADH oxidase enables the metabolism of citrate, the sole carbon source via a modified TCA cycle. The overexpression of succinyl-CoA synthetase affords an effective route to ATP production by substrate-level phosphorylation in the absence of O2. This fine metabolic balance enables P. fluorescens to survive the dearth of bioavailable Fe triggered by an Al environment, a feature that may have potential applications in bioremediation technologies. [source] Mitochondrial function and endocrine diseasesEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 4 2007R. Stark Abstract Mitochondria are fundamental for oxidative energy production and impairment of their functionality can lead to reduced ATP synthesis and contribute to initiation of apoptosis. Endocrine tissues critically rely on oxidative phosphorylation so that mitochondrial abnormalities may either be causes or consequences of diminished hormone production or action. Abnormalities typical for diseases caused by mitochondrial DNA mutations such as Kearns,Sayre syndrome or mitochondrial encephalomyopathy, lactic acidosis, and stroke,like episodes syndrome are also seen in certain endocrine diseases. Lack or excess of thyroid hormones, major ubiquitous regulators of mitochondrial content and activity, cause muscular abnormalities and multisystem disorders. Mitochondria are a further prerequisite for steroidogenesis as well as insulin secretion and action. Recent studies showed that reduced mitochondrial ATP synthesis in skeletal muscle is a feature of certain hereditary and acquired forms of insulin resistance and diabetes mellitus. Finally, ageing is not only accompanied by various degrees of hormonal deficiency and insulin resistance but is also associated with a progressive decline of mitochondrial number and function. Future research is needed to examine whether mitochondrial abnormalities are the cause or consequence of ageing and frequent metabolic diseases such as obesity and type 2 diabetes mellitus, and to address mitochondria as a target for novel therapeutic regimes. [source] Analysis of mitochondria by capillary electrophoresis: cardiolipin levels decrease in response to carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazoneEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 9 2010Wenfeng Zhao Abstract Cardiolipin is an important phospholipid present in the inner membrane of mitochondria. It plays a critical role in adenosine triphosphate (ATP) synthesis mediated by oxidative phosphorylation. Exposure of HepG2 cells to carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP) caused the inhibition of ATP synthesis and the depolarization of mitochondria. Capillary electrophoresis with laser-induced fluorescence (CE-LIF) analysis of fluorescent mitochondrion-selective probe 10-N-nonyl acridine orange (NAO) labeled mitochondria was employed to in situ estimate the cardiolipin levels under FCCP-induced de-energization of mitochondria. NAO, stoichiometriclly bound to cardiolipin at a 1:1 or 2:1 molar ratio (NAO/cardiolipin), emitted green and red fluorescence, respectively. Green fluorescence was chosen for cardiolipin content analysis because it was more intense than red fluorescence. A significant decrease in the cardiolipin content, up to 11% of the control, was evident when the ATP content and mitochondrial membrane potential (MMP) correspondingly decreased. These related findings suggested that CE-LIF may provide a sensitive strategy to determine cardiolipin content in response to exposure to chemical uncouplers. This reinforces the hypothesis that alterations in ATP synthesis and MMP have a close association with cardiolipin content, which correlated tightly with mitochondrial membrane assembly and activity. [source] Creatine has no beneficial effect on skeletal muscle energy metabolism in patients with single mitochondrial DNA deletions: a placebo-controlled, double-blind 31P-MRS crossover studyEUROPEAN JOURNAL OF NEUROLOGY, Issue 4 2005C. Kornblum The purpose of our randomized, double-blind, placebo-controlled crossover study in 15 patients with chronic progressive external ophthalmoplegia (CPEO) or Kearns,Sayre syndrome (KSS) because of single large-scale mitochondrial (mt) DNA deletions was to determine whether oral creatine (Cr) monohydrate can improve skeletal muscle energy metabolism in vivo. Each treatment phase with Cr in a dosage of 150 mg/kg body weight/day or placebo lasted 6 weeks. The effect of Cr was estimated by phosphorus-31 magnetic resonance spectroscopy (31P-MRS), clinical and laboratory tests. 31P-MRS analysis prior to treatment showed clear evidence of severe mitochondrial dysfunction. However, there were no relevant changes in 31P-MRS parameters under Cr. In particular, phosphocreatine (PCr)/ATP at rest did not increase, and there was no facilitation of post-exercise PCr recovery. Clinical scores and laboratory tests did not alter significantly under Cr, which was tolerated without major side-effects in all patients. Cr supplementation did not improve skeletal muscle oxidative phosphorylation in our series of patients. However, one explanation for our negative findings may be the short study duration or the limited number of patients included. [source] The Effects of Steroid Hormones on the Transcription of Genes Encoding Enzymes of Oxidative PhosphorylationEXPERIMENTAL PHYSIOLOGY, Issue 1 2003Klaus Scheller Regulation of energy metabolism is one of the major functions of steroid hormones. In this process, mitochondria, by way of oxidative phosphorylation, play a central role. Depending on the energy needs of the cell, on the tissue, on the developmental stage and on the intensity of the hormonal stimulus, the response can be an activation of pre-existing respiratory chain components, an increased transcription of nuclear-encoded and/or mitochondrial-encoded respiratory chain enzyme (OXPHOS) genes and of biosynthesis of the respective enzyme subunits or, in extreme cases of high energy needs, an increase in the number of mitochondria and mitochondrial DNA content per cell. Some of the hormonally regulated systems involving effects on nuclear and mitochondrial OXPHOS genes are reviewed in this paper. The possible molecular mechanisms of steroid hormone action on nuclear and mitochondrial gene transcription and possible ways of coordination of transcription in these two separate cell compartments involving direct interaction of steroid receptors with hormone response elements in nuclear OXPHOS genes and in mitochondria and induction/activation of nuclear-encoded regulatory factors affecting mitochondrial gene transcription are presented. [source] Cold-Induced Recruitment of Brown Adipose Tissue ThermogenesisEXPERIMENTAL PHYSIOLOGY, Issue 1 2003Martin Klingenspor Non-shivering thermogenesis in brown adipose tissue is the main mechanism for thermoregulatory heat production in small mammals and newborns. During cold acclimation the sympathetic innervation triggers the recruitment of brown adipose tissue by hyperplasia, which involves the proliferation and differentiation of precursor cells, and by hypertrophy of mature brown adipocytes. Mitochondrial biogenesis and increased synthesis of the uncoupling protein 1 (UCP-1) are hallmarks of the thermogenic recruitment process. The severalfold increase of mitochondrial protein content during cold acclimation recruits a large capacity for oxidative phosphorylation. However, UCP-1 increases proton leakage across the inner membrane of brown adipocyte mitochondria and thereby dissipates proton motive force as heat instead of ATP synthesis. During recent years considerable progress has been achieved in the analysis of transcriptional mechanisms controlling Ucp1 gene expression. However, so far only little is known about the molecular basis of cold-induced mitochondrial biogenesis in brown adipose tissue. [source] Control of p70 ribosomal protein S6 kinase and acetyl-CoA carboxylase by AMP-activated protein kinase and protein phosphatases in isolated hepatocytesFEBS JOURNAL, Issue 15 2002Ulrike Krause Certain amino acids, like glutamine and leucine, induce an anabolic response in liver. They activate p70 ribosomal protein S6 kinase (p70S6K) and acetyl-CoA carboxylase (ACC) involved in protein and fatty acids synthesis, respectively. In contrast, the AMP-activated protein kinase (AMPK), which senses the energy state of the cell and becomes activated under metabolic stress, inactivates by phosphorylation key enzymes in biosynthetic pathways thereby conserving ATP. In this paper, we studied the effect of AMPK activation and of protein phosphatase inhibitors, on the amino-acid-induced activation of p70S6K and ACC in hepatocytes in suspension. AMPK was activated under anoxic conditions or by incubation with 5-aminoimidazole-4-carboxyamide ribonucleoside (AICAr) or oligomycin, an inhibitor of mitochondrial oxidative phosphorylation. Incubation of hepatocytes with amino acids activated p70S6K via multiple phosphorylation. It also activated ACC by a phosphatase-dependent mechanism but did not modify AMPK activation. Conversely, the amino-acid-induced activation of both ACC and p70S6K was blocked or reversed when AMPK was activated. This AMPK activation increased Ser79 phosphorylation in ACC but decreased Thr389 phosphorylation in p70S6K. Protein phosphatase inhibitors prevented p70S6K activation when added prior to the incubation with amino acids, whereas they enhanced p70S6K activation when added after the preincubation with amino acids. It is concluded that (a) AMPK blocks amino-acid-induced activation of ACC and p70S6K, directly by phosphorylating Ser79 in ACC, and indirectly by inhibiting p70S6K phosphorylation, and (b) both activation and inhibition of protein phosphatases are involved in the activation of p70S6K by amino acids. p70S6K adds to an increasing list of targets of AMPK in agreement with the inhibition of energy-consuming biosynthetic pathways. [source] Role of reserve carbohydrates in the growth dynamics of Saccharomyces cerevisiae,FEMS YEAST RESEARCH, Issue 8 2004Vincent Guillou Abstract The purpose of this study was to explore the role of glycogen and trehalose in the ability of Saccharomyces cerevisiae to respond to a sudden rise of the carbon flux. To this end, aerobic glucose-limited continuous cultures were challenged with a sudden increase of the dilution rate from 0.05 to 0.15 h,1. Under this condition, a rapid mobilization of glycogen and trehalose was observed which coincided with a transient burst of budding and a decrease of cell biomass. Experiments carried out with mutants defective in storage carbohydrates indicated a predominant role of glycogen in the adaptation to this perturbation. However, the real importance of trehalose in this response was veiled by the unexpected phenotypes harboured by the tps1 mutant, chosen for its inability to synthesize trehalose. First, the biomass yield of this mutant was 25% lower than that of the isogenic wild-type strain at dilution rate of 0.05 h,1, and this difference was annulled when cultures were run at a higher dilution rate of 0.15 h,1. Second, the tps1 mutant was more effective to sustain the dilution rate shift-up, apparently because it had a faster glycolytic rate and an apparent higher capacity to consume glucose with oxidative phosphorylation than the wild type. Consequently, a tps1gsy1gsy2 mutant was able to adapt to the dilution rate shift-up after a long delay, likely because the detrimental effects from the absence of glycogen was compensated for by the tps1 mutation. Third, a glg1,glg2, strain, defective in glycogen synthesis because of the lack of the glycogen initiation protein, recovered glycogen accumulation upon further deletion of TPS1. This recovery, however, required glycogen synthase. Finally, we demonstrated that the rapid breakdown of reserve carbohydrates triggered by the shift-up is merely due to changes in the concentrations of hexose-6-phosphate and UDPglucose, which are the main metabolic effectors of the rate-limiting enzymes of glycogen and trehalose pathways. [source] ,-Glutamyltranspeptidase,deficient knockout mice as a model to study the relationship between glutathione status, mitochondrial function, and cellular functionHEPATOLOGY, Issue 4 2000Yvonne Will ,-Glutamyltranspeptidase (GGT)-deficient mice (GGT,/,) display chronic glutathione (GSH) deficiency, growth retardation, and die at a young age (<20 weeks). Using livers from these mice, we investigated the relationship between GSH content, especially mitochondrial, and mitochondrial and cellular function. We found that the GSH content of isolated liver mitochondria was diminished by ,50% in GGT,/, mice when compared with wild-type mice. Respiratory control ratios (RCRs) of GGT,/, mice liver mitochondria were ,60% those of wild-type mice primarily as a result of impaired state 3 respiration. Mitochondrial adenine nucleotide content was decreased by ,40% in mitochondria obtained from GGT,/, mice. We observed a strong correlation between mitochondrial GSH content and RCRs. Even moderate decreases (<50%) correlated with adverse effects with respect to respiration. Electron microscopy revealed that livers from GGT,/, knockout mice were deprived of fat and glycogen, and swollen mitochondria were observed in animals that were severely deprived of GSH. Thus, GGT,/, mice exhibit a loss of GSH homeostasis and impaired oxidative phosphorylation, which may be related to the rate of adenosine triphosphate (ATP) formation and subsequently leads to progressive liver injury, which characterizes the diseased state. We also found that supplementation of GGT,/, mice with N -acetylcysteine (NAC) partially restored liver GSH, but fully restored mitochondrial GSH and respiratory function. Electron microscopy revealed that the livers of NAC-supplemented GGT,/, mice contained fat and glycogen; however, slightly enlarged mitochondria were found in some livers. NAC supplementation did not have any beneficial effect on the parameters examined in wild-type mice. [source] Validation of microarray-based resequencing of 93 worldwide mitochondrial genomes,HUMAN MUTATION, Issue 1 2009Anne Hartmann Abstract The human mitochondrial genome consists of a multicopy, circular dsDNA molecule of 16,569 base pairs. It encodes for 13 proteins, two ribosomal genes, and 22 tRNAs that are essential in the generation of cellular ATP by oxidative phosphorylation in eukaryotic cells. Germline mutations in mitochondrial DNA (mtDNA) are an important cause of maternally inherited diseases, while somatic mtDNA mutations may play important roles in aging and cancer. mtDNA polymorphisms are also widely used in population and forensic genetics. Therefore, methods that allow the rapid, inexpensive and accurate sequencing of mtDNA are of great interest. One such method is the Affymetrix GeneChip® Human Mitochondrial Resequencing Array 2.0 (MitoChip v.2.0) (Santa Clara, CA). A direct comparison of 93 worldwide mitochondrial genomes sequenced by both the MitoChip and dideoxy terminator sequencing revealed an average call rate of 99.48% and an accuracy of ,99.98% for the MitoChip. The good performance was achieved by using in-house software for the automated analysis of additional probes on the array that cover the most common haplotypes in the hypervariable regions (HVR). Failure to call a base was associated mostly with the presence of either a run of ,4,C bases or a sequence variant within 12 bases up- or downstream of that base. A major drawback of the MitoChip is its inability to detect insertions/deletions and its low sensitivity and specificity in the detection of heteroplasmy. However, the vast majority of haplogroup defining polymorphism in the mtDNA phylogeny could be called unambiguously and more rapidly than with conventional sequencing. Hum Mutat 0,1,8, 2008. © 2008 Wiley-Liss, Inc. [source] Improving cellular function through modulation of energy metabolismINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 5 2004D. Maes The ambivalent consequences of mitochondrial stimulation on cellular activity have been well established. Mitochondria supply the cell with energy through a process of oxidative phosphorylation but thereby generate free radicals, resulting in the accumulation of hydrogen peroxide in the cytoplasm. We have investigated the impact of cellular senescence as well as UV irradiation, on the balance between these two activities. The adenosine triphosphate (ATP) level, DNA and protein synthesis in fibroblasts obtained from donors between 30 and 90 years of age appeared to be significantly influenced by the aging process. Both DNA and protein synthesis could be stimulated by increasing intracellular ATP levels. In-vitro senescent fibroblasts showed a reduction in the level of ATP as well as a shift in mitochondrial membrane potential. At the same time, there was an increase in intracellular hydrogen peroxide with increasing population doubling, indicating a clear dysfunction of the metabolic machinery in the mitochondria of senescent cells. To counteract this degradation of the energy pool, we treated cells with creatine, which is known to restore the pool of phosphocreatine in the mitochondria. Creatine treatment significantly increased cell survival after UV exposure, stimulated the repair of UVB-induced DNA damage in keratinocytes and caused a significant reduction in the number of sunburn cells in a UVB-exposed reconstituted skin model. These results clearly indicate that restoration of the energy pool in mitochondria increased cellular self-defense mechanism. These data show the important role played by the mitochondrial energy metabolism on the aging process, and indicate a possible therapy that can be used to counteract this negative effect. Treatment with creatine seems to provide the necessary boost to the cellular metabolism, which leads to an induction of a significant amount of protection and repair to human skin cells. [source] Mitochondrial copper metabolism and delivery to cytochrome c oxidaseIUBMB LIFE, Issue 7 2008Darryl Horn Abstract Metals are essential elements of all living organisms. Among them, copper is required for a multiplicity of functions including mitochondrial oxidative phosphorylation and protection against oxidative stress. Here we will focus on describing the pathways involved in the delivery of copper to cytochrome c oxidase (COX), a mitochondrial metalloenzyme acting as the terminal enzyme of the mitochondrial respiratory chain. The catalytic core of COX is formed by three mitochondrially-encoded subunits and contains three copper atoms. Two copper atoms bound to subunit 2 constitute the CuA site, the primary acceptor of electrons from ferrocytochrome c. The third copper, CuB, is associated with the high-spin heme a3 group of subunit 1. Recent studies, mostly performed in the yeast Saccharomyces cerevisiae, have provided new clues about 1) the source of the copper used for COX metallation; 2) the roles of Sco1p and Cox11p, the proteins involved in the direct delivery of copper to the CuA and CuB sites, respectively; 3) the action mechanism of Cox17p, a copper chaperone that provides copper to Sco1p and Cox11p; 4) the existence of at least four Cox17p homologues carrying a similar twin CX9C domain suggestive of metal binding, Cox19p, Cox23p, Pet191p and Cmc1p, that could be part of the same pathway; and 5) the presence of a disulfide relay system in the intermembrane space of mitochondria that mediates import of proteins with conserved cysteines motifs such as the CX9C characteristic of Cox17p and its homologues. The different pathways are reviewed and discussed in the context of both mitochondrial COX assembly and copper homeostasis. © 2008 IUBMB IUBMB Life, 60(7): 421,429, 2008 [source] Novel neuroprotective, neuritogenic and anti-amyloidogenic properties of 2,4-dinitrophenol: The gentle face of JanusIUBMB LIFE, Issue 4 2006Fernanda G. De Felice Abstract In Roman mythology, Janus was the god of gates, doors, beginnings and endings. He was usually depicted with two faces looking in opposite directions. Janus was frequently used to symbolize change and transitions, such as the progression from past to future or from one viewpoint to another. 2,4-dinitrophenol (DNP) and other nitrophenols have long been known to be toxic at high concentrations (the 'bad' face of DNP), an effect that appears essentially related to interference with cellular energy metabolism due to uncoupling of mitochondrial oxidative phosphorylation. Five years ago, however, we published the first report showing that low concentrations of DNP protect neurons against the toxicity of the amyloid-, peptide (De Felice et al. (2001) FASEB J. 15:1297 - 1299]. Since then, other studies have provided evidence of beneficial actions of DNP (at low concentrations), including neuroprotection against different types of insult, blockade of amyloid aggregation, stimulation of neurite outgrowth and neuronal differentiation, and even extension of lifespan in certain organisms. Some of these effects appear to be due to mild mitochondrial uncoupling and prevention of cellular oxidative stress, whereas other actions are related to activation of additional intracellular signaling pathways. Thus, a novel and 'gentle' face of DNP is emerging from such studies. In this review, we discuss both toxic and beneficial actions of DNP. The evidence available so far suggests that DNP and other compounds with similar biological activities may be of significant interest to the development of novel therapeutic approaches for neurodegenerative diseases and other neurological disorders. iubmb Life, 58: 185-191, 2006 [source] The adenine nucleotide translocase type 1 (ANT1): A new factor in mitochondrial diseaseIUBMB LIFE, Issue 9 2005J. Daniel Sharer Abstract Mitochondrial disorders of oxidative phosphorylation (OXPHOS) comprise a growing list of potentially lethal diseases caused by mutations in either mitochondrial (mtDNA) or nuclear DNA (nDNA). Two such conditions, autosomal dominant progressive external ophthalmoplegia (adPEO) and Senger's Syndrome, are associated with dysfunction of the heart and muscle-specific isoform of the adenine nucleotide translocase (ANT1), a nDNA gene product that facilitates transport of ATP and ADP across the inner mitochondrial membrane. AdPEO is a mtDNA deletion disorder broadly characterized by pathology involving the eyes, skeletal muscle, and central nervous system. In addition to ANT1, mutations in at least two other nuclear genes, twinkle and POLG, have been shown to cause mtDNA destabilization associated with adPEO. Senger's syndrome is an autosomal recessive condition characterized by congenital heart defects, abnormalities of skeletal muscle mitochondria, cataracts, and elevated circulatory levels of lactic acid. This syndrome is associated with severe depletion of ANT1, which may be the result of an as yet unidentified ANT1-specific transcriptional or translational processing error. ANT1 has also been associated with a third condition, autosomal dominant facioscapulohumeral muscular dystrophy (FSHD), an adult onset disorder characterized by variable muscle weakness in the face, feet, shoulders, and hips. FSHD patients possess specific DNA deletions on chromosome 4, which appear to cause derepression of several nearby genes, including ANT1. Early development of FSHD may involve mitochondrial dysfunction and increased oxidative stress, possibly associated with overexpression of ANT1. IUBMB Life, 57: 607-614, 2005 [source] Eight-Step Synthesis of RoutiennocinADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2008Kenji Matsumoto Abstract Routiennocin is a member of a family of polycyclic pyrrole ether antibiotics that simultaneously uncouple oxidative phosphorylation and inhibit ATPase as a result of selective complexation of divalent metal ions. We describe a concise synthesis of routiennocin with the longest linear sequence of 8 steps. Our synthesis features a unique bi-directional strategy, which entails a sequential ring-opening/cross metathesis of a highly strained cyclopropenone acetal. This approach enables rapid and highly convergent assembly of the fully extended polyketide subunit of this natural product from readily available homoallylic alcohol precursors. [source] Metabolic effects of carbenoxolone in rat liverJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 5 2006Leandro Silva Pivato The action of carbenoxolone on hepatic energy metabolism was investigated in the perfused rat liver and isolated mitochondria. In perfused livers, carbenoxolone (200,300 ,M) increased oxygen consumption, glucose production and glycolysis from endogenous glycogen. Gluconeogenesis from lactate or fructose, an energy-dependent process, was inhibited. This effect was already evident at a concentration of 25 ,M. The cellular ATP levels and the adenine nucleotide content were decreased by carbenoxolone, whereas the AMP levels were increased. In isolated mitochondria, carbenoxolone stimulated state IV respiration and decreased the respiratory coefficient with the substrates ,-hydroxybutyrate and succinate. The ATPase of intact mitochondria was stimulated, the ATPase of uncoupled mitochondria was inhibited, and the ATPase of disrupted mitochondria was not altered by carbenoxolone. These results indicate that carbenoxolone acts as an uncoupler of oxidative phosphorylation and, possibly, as an inhibitor of the ATP/ADP exchange system. The inhibitory action of carbenoxolone on mitochondrial energy metabolism could be contributing to induce the mitochondrial permeability transition (MPT), a key phenomenon in apoptosis. The results of the present study can explain, partly at least, the in vivo hepatotoxic actions of carbenoxolone that were found in a previous clinical evaluation. © 2006 Wiley Periodicals, Inc. J Biochem Mol Toxicol 20:230,240, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20139 [source] Respiration of steelhead trout sperm: sensitivity to pH and carbon dioxideJOURNAL OF FISH BIOLOGY, Issue 1 2003R. L. Ingermann Steelhead trout Oncorhynchus mykiss sperm held in seminal plasma or sperm-immobilizing buffer (pH 8·6) at 10° C consumed O2 at the rate of c. 2 nmol O2 min,1 10,9 sperm; the rate of O2 consumption was not different in sperm held for 4 or 24 h. Decreasing the extracellular pH from 8·5 to 7·5 either by diluting semen with buffer titrated with HCl or by increasing the partial pressure of CO2 in the incubation atmosphere resulted in c. a 40% decrease in the rate of sperm respiration. The data did not, however, support the hypothesis that the precipitous reduction in the capacity for sperm motility that occurs as external pH is reduced is a result of a decrease in cellular metabolism. The rate of O2 consumption of freshly collected semen from different males was not correlated to cellular ATP content or to the proportion of sperm that were motile upon activation; the initial ATP content and sperm motility were positively correlated. The rate of O2 consumption was not significantly increased following sperm activation or by the addition of an uncoupler of oxidative phosphorylation, carbonyl cyanide p -trifluoromethoxyphenylhydrazone, suggesting that these sperm have little, if any, capacity for increased oxidative metabolism. [source] Chloramphenicol decreases brain glucose utilization and modifies the sleep,wake cycle architecture in ratsJOURNAL OF NEUROCHEMISTRY, Issue 6 2005Marcelle Moulin-Sallanon Abstract We studied the effects of chloramphenicol on brain glucose utilization and sleep,wake cycles in rat. After slightly anaesthetized animals were injected with [18F]fluoro-2-deoxy- d -glucose, we acquired time,concentration curves from three radiosensitive , microprobes inserted into the right and left frontal cortices and the cerebellum, and applied a three-compartment model to calculate the cerebral metabolic rates for glucose. The sleep,wake cycle architecture was analysed in anaesthetic-free rats by recording electroencephalographic and electromyographic signals. Although chloramphenicol is a well-established inhibitor of oxidative phosphorylation, no compensatory increase in glucose utilization was detected in frontal cortex. Instead, chloramphenicol induced a significant 23% decrease in the regional cerebral metabolic rate for glucose. Such a metabolic response indicates a potential mismatch between energy supply and neuronal activity induced by chloramphenicol administration. Regarding sleep,wake states, chloramphenicol treatment was followed by a 64% increase in waking, a 20% decrease in slow-wave sleep, and a marked 59% loss in paradoxical sleep. Spectral analysis of the electroencephalogram indicates that chloramphenicol induces long-lasting modifications of delta-band power during slow-wave sleep. [source] Oxidative modification of mitochondrial proteins and cell death in Parkinson's diseaseJOURNAL OF NEUROCHEMISTRY, Issue 2002W. Maruyama Oxidative stress is one of the cell death mechanisms in neurodegenerative disorders, such as Parkinson's disease (PD) and Alzheimer's disease. Most of reactive oxygen species (ROS) generate in mitochondria through oxidative phosphorylation, and a part of them are not scavenged by antioxidative system and react with bioactive molecules. Recently, alpha-synuclein containing nitrotyrosine, a marker for oxidative modification by peroxynitrite, was identified in Lewy body. In addition, inhibitors of mitochondrial respiratory chain were reported to induce formation of Lewy body-like inclusion in vivo and in vitro. In this paper it was examined whether ROS and reactive nitrogen species (RNS) generated in mitochondria oxidize mitochondrial respiratory enzymes and induce the formation of inclusion body and cell death in PD. Human neuroblastoma SH-SY5Y cells were treated with a peroxynitrite donor, SIN-1, or an inhibitor of complex I, rotenone. After the treatment, proteins modified with toxic aldehydes, 4-hydroxynonenal and acrolein, and containing nitrotyrosine were analyzed by immunoblotting. Particularly in mitochondrial fraction, the oxidized protein was characterized by two-dimensional immunoblotting. Most of the oxidized proteins were detected in subunits proteins of complex I. These results indicate that mitochondrial complex I is a main target of oxidative stress in dopamine neurons and its dysfunction may be involved in the death mechanism in neurodegenerative disorders. [source] Mitochondrial dysfunction in a neural cell model of spinal muscular atrophyJOURNAL OF NEUROSCIENCE RESEARCH, Issue 12 2009Gyula Acsadi Abstract Mutations of the survival motor neuron (SMN) gene in spinal muscular atrophy (SMA) lead to anterior horn cell death. The cause is unknown, but motor neurons depend substantially on mitochondrial oxidative phosphorylation (OxPhos) for normal function. Therefore, mitochondrial parameters were analyzed in an SMA cell culture model using small interfering RNA (siRNA) transfection that decreased Smn expression in NSC-34 cells to disease levels. Smn siRNA knock-down resulted in 35% and 66% reduced Smn protein levels 48 and 72 hr posttransfection, respectively. ATP levels were reduced by 14% and 26% at 48 and 72 hr posttransfection, respectively, suggesting decreased ATP production or increased energy demand in neural cells. Smn knock-down resulted in increased mitochondrial membrane potential and increased free radical production. Changes in activity of cytochrome c oxidase (CcO), a key OxPhos component, were observed at 72 hr with a 26% increase in oxygen consumption. This suggests a compensatory activation of the aerobic pathway, resulting in increased mitochondrial membrane potentials, a condition known to lead to the observed increase in free radical production. Further testing suggested that changes in ATP at 24 hr precede observable indices of cell injury at 48 hr. We propose that energy paucity and increased mitochondrial free radical production lead to accumulated cell damage and eventual cell death in Smn-depleted neural cells. Mitochondrial dysfunction may therefore be important in SMA pathology and may represent a new therapeutic target. © 2009 Wiley-Liss, Inc. [source] Fasting is neuroprotective following traumatic brain injury,JOURNAL OF NEUROSCIENCE RESEARCH, Issue 8 2008Laurie M. Davis Abstract To determine the neuroprotective effect of fasting after traumatic brain injury (TBI) and to elucidate the potential underlying mechanisms, we used a controlled cortical impact (CCI) injury model to induce either a moderate or a severe injury to adult male Sprague Dawley rats. Tissue-sparing assessments were used to determine the level of neuroprotection of fasting, hypoglycemia (insulin 10 U), or ketone (1.66 mmoles/kg/day or 0.83 mmoles/kg/day; D-beta-hydroxtbutyrate) administration. Mitochondrial isolation and respiratory studies were utilized to determine the functionality of mitochondria at the site of injury. We also investigated biomarkers of oxidative stress, such as lipid/protein oxidation, reactive oxygen species (ROS) production, and intramitochondrial calcium load, as a secondary measure of mitochondrial homeostasis. We found that fasting animals for 24 hr, but not 48 hr, after a moderate (1.5 mm), but not severe (2.0 mm), CCI resulted in a significant increase in tissue sparing. This 24-hr fast also decreased biomarkers of oxidative stress and calcium loading and increased mitochondrial oxidative phosphorylation in mitochondria isolated from the site of injury. Insulin administration, designed to mimic the hypoglycemic effect seen during fasting did not result in significant tissue sparing after moderate CCI injury and in fact induced increased mortality at some injection time points. However, the administration of ketones resulted in increased tissue sparing after moderate injury. Fasting for 24 hr confers neuroprotection, maintains cognitive function, and improves mitochondrial function after moderate (1.5 mm) TBI. The underlying mechanism appears to involve ketosis rather than hypoglycemia. © 2008 Wiley-Liss, Inc. [source] | ||||||||||||||||||||||||||||||||||