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Mitochondria-related neurodegenerative diseases have been implicated in the disruption of primary cilia function. Mutation in an intrinsic mitochondrial complex I component NDUFAF2 has been identified in Leigh syndrome, a severe inherited mitochondriopathy. Mutations in ARMC9, which encodes a basal body protein, cause Joubert syndrome, a ciliopathy with defects in the brain, kidney, and eye. Here, we report a mechanistic link between mitochondria metabolism and primary cilia signaling. We discovered that loss of NDUFAF2 caused both mitochondrial and ciliary defects in vitro and in vivo and identified NDUFAF2 as a binding partner for ARMC9. We also found that NDUFAF2 was both necessary and sufficient for cilia formation and that exogenous expression of NDUFAF2 rescued the ciliary and mitochondrial defects observed in cells from patients with known ARMC9 deficiency. [NAD.sup.+] supplementation restored mitochondrial and ciliary dysfunction in ARMC9-deficient cells and zebrafish and ameliorated the ocular motility and motor deficits of a patient with ARMC9 deficiency. The present results provide a compelling mechanistic link, supported by evidence from human studies, between primary cilia and mitochondrial signaling. Importantly, our findings have significant implications for the development of therapeutic approaches targeting ciliopathies., Introduction The primary cilium is a solitary, immobile microtubule-based structure present on the apical surface of many cell types, especially in sensory organs such as the eye and nose. The [...]

Sodium deoxycholate (NaDOC) inhibits the intestinal [Ca.sup.2+] absorption and ursodeoxycholic acid (UDCA) stimulates it. The aim of this study was to determine whether NaDOC and UDCA produce differential effects on the redox state of duodenal mitochondria altering the Krebs cycle and the electron transport chain (ETC) functioning, which could lead to perturbations in the mitochondrial dynamics and biogenesis. Rat intestinal mitochondria were isolated from untreated and treated animals with either NaDOC, UDCA, or both. Krebs cycle enzymes, ETC components, ATP synthase, and mitochondrial dynamics and biogenesis markers were determined. NaDOC decreased isocitrate dehydrogenase (ICDH) and malate dehydrogenase activities affecting the ETC and ATP synthesis. NaDOC also induced oxidative stress and increased the superoxide dismutase activity and impaired the mitochondrial biogenesis and functionality. UDCA increased the activities of ICDH and complex II of ETC. The combination of both bile acids conserved the functional activities of Krebs cycle enzymes, ETC components, oxidative phosphorylation, and mitochondrial biogenesis. In conclusion, the inhibitory effect of NaDOC on intestinal [Ca.sup.2+] absorption is mediated by mitochondrial dysfunction, which is avoided by UDCA. The stimulatory effect of UDCA alone is associated with amelioration of mitochondrial functioning. This knowledge could improve treatment of diseases that affect the intestinal [Ca.sup.2+] absorption. Key words: NaDOC, UDCA, Krebs cycle, ETC, ATP synthase activity, duodenum, mitochondrial biogenesis, oxidative stress. Le desoxycholate de sodium (NaDOC) entraine une inhibition de l'absorption intestinale du [Ca.sup.2+], alors que l'acide ursodesoxycholique (UDCA) entraine sa stimulation. Le but de cette etude etait d'etablir si le NaDOC et le UDCA produisent des effets differentiels sur l'etat d'oxydoreduction de mitochondries duodenales, modifiant le cycle de Krebs et le fonctionnement de la chaine de transport des electrons (CTE), ce qui pourrait mener a des perturbations dans les proprietes dynamiques et la biogenese des mitochondries. Nous avons isole des mitochondries de l'intestin de rats auxquels etait administre ou non du NaDOC, du UDCA ou les deux. Nous avons etabli les concentrations des enzymes du cycle de Krebs, des composantes de la CTE et de l'ATP synthase, ainsi que les proprietes dynamiques des mitochondries et les marqueurs de leur biogenese. Le NaDOC entrainait un abaissement de l'activite de l'isocitrate deshydrogenase (ICDH) et de la malate deshydrogenase affectant la CTE et la synthese d'ATP. Le NaDOC entrainait aussi un stress oxydatif et une augmentation de l'activite de la superoxyde dismutase, avec des effets deleteres sur la biogenese et le fonctionnement des mitochondries. Le UDCA entrainait une augmentation de l'activite de l'ICDH et du complexe II de la CTE. L'association des deux acides biliaires permettait de preserver l'activite fonctionnelle des enzymes du cycle de Krebs, des composantes de la CTE, de la phosphorylation oxydative et la biogenese des mitochondries. En conclusion, l'effet inhibiteur du NaDOC sur l'absorption intestinale du [Ca.sup.2+] est medie par un dysfonctionnement des mitochondries qui peut etre evite avec le UDCA. L'effet stimulateur du UDCA seul est associe avec une amelioration du fonctionnement des mitochondries. Ces connaissances pourraient permettre d'ameliorer le traitement de maladies qui affectent l'absorption intestinale du [Ca.sup.2+]. Mots-cles : NaDOC, UDCA, cycle de Krebs, chaine de transport des electrons, activite de l'ATP synthase, duodenum, biogenese des mitochondries, stress oxydatif., Introduction We have previously demonstrated that the inhibition of intestinal [Ca.sup.2+] absorption caused by oxidants that mainly cause GSH depletion could be either prevented or restored by antioxidants such as [...]

ABSTRACT Heteroplasmy is the presence of multiple genotypes in an individual and is commonly associated with mitochondria where thousands of copies of the genome can be present in a single [...]

Li-Fraumeni syndrome (LFS) is a cancer predisposition disorder caused by germline mutations in TP53 that can lead to increased mitochondrial metabolism in patients. However, the implications of altered mitochondrial function for tumorigenesis in LFS are unclear. Here, we have reported that genetic or pharmacologic disruption of mitochondrial respiration improves cancer-free survival in a mouse model of LFS that expresses mutant p53. Mechanistically, inhibition of mitochondrial function increased autophagy and decreased the aberrant proliferation signaling caused by mutant p53. In a pilot study, LFS patients treated with metformin exhibited decreases in mitochondrial activity concomitant with activation of antiproliferation signaling, thus reproducing the effects of disrupting mitochondrial function observed in LFS mice. These observations indicate that a commonly prescribed diabetic medicine can restrain mitochondrial metabolism and tumorigenesis in an LFS model, supporting its further consideration for cancer prevention in LFS patients., Introduction Growing evidence suggests that the mitochondrion plays a critical role in cancer development through various processes including metabolism, ROS generation, and cell signaling (1, 2). Increased oxidative phosphorylation and [...]

The outer membranes of Gram-negative bacteria, mitochondria, and chloroplasts harbor [beta]-barrel proteins. The signals that allow precursors of such proteins to be targeted to mitochondria were not characterized so far. To better understand the mechanism by which [beta]-barrel precursor proteins are recognized and sorted within eukaryotic cells, we expressed the bacterial [beta]-barrel proteins PhoE, OmpA, Omp85, and OmpC in Saccharomyces cerevisiae and demonstrated that they were imported into mitochondria. A detailed investigation of the import pathway of PhoE revealed that it is shared with mitochondrial [beta]-barrel proteins. PhoE interacts initially with surface import receptors, and its further sorting depends on components of the TOB/SAM complex. The bacterial Omp85 and PhoE integrated into the mitochondrial outer membrane as native-like oligomers. For the latter protein this assembly depended on the C-terminal Phe residue, which is important also for the correct assembly of PhoE into the bacterial outer membrane. Collectively, it appears that mitochondrial [beta]-barrel proteins have not evolved eukaryotic-specific signals to ensure their import into mitochondria. Furthermore, the signal for assembly of [beta]-barrel proteins into the bacterial outer membrane is functional in mitochondria. outer membrane | PhoE | protein import | TOB complex | TOM complex

The sirtuins are a group of proteins linked to aging, metabolism and stress tolerance in several organisms. Among the many genes that have been shown to affect aging in model organisms, sirtuin genes are unique in that their activity level is positively correlated with lifespan (i.e. they are anti-aging genes). Sirtuins are a druggable class of enzymes (i.e. amenable to intervention by small molecules) that could have beneficial effects on a variety of human diseases. In view of the many functions of Sirtuin 1 (SIRT1) in cells, this review focuses on its role in regulating important aspects of mitochondrial biology. Mitochondria have been linked to aging, and also to diseases of aging. Thus, sirtuins might provide a key link between mitochondrial dysfunction, aging and metabolic disease.

Abstract Objective: Accumulating evidence indicates that mitochondrial function is impaired in vital organs during sepsis. In addition to oxidative phosphorylation, mitochondria participate in diverse cellular functions ranging from protein and [...]

During apoptosis, proapoptotic factors are released from mitochondria by as yet undefined mechanisms. Patch-clamping of mitochondria and proteoliposomes formed from mitochondrial outer membranes of mammalian (FL5.12) cells has uncovered a novel ion channel whose activity correlates with onset of apoptosis. The pore diameter inferred from the largest conductance state of this channel is ~4 nm, sufficient to allow diffusion of cytochrome c and even larger proteins. The activity of the channel is affected by Bcl-2 family proteins in a manner consistent with their pro- or antiapoptotic properties. Thus, the channel activity correlates with presence of proapoptotic Bax in the mitochondrial outer membrane and is absent in mitochondria from cells overexpressing antiapoptotic Bcl-2. Also, a similar channel activity is found in mitochondrial outer membranes of yeast expressing human Bax. These findings implicate this channel, named mitochondrial apoptosis--induced channel, as a candidate for the outer-membrane pore through which cytochrome c and possibly other factors exit mitochondria during apoptosis.

Research has been conducted on the mitochondrial protein horse heart cytochrome c. Chromatographic separation and identification of site-specifically labeled species via peptide sequencing of tryptic digests is described.

Research has been conducted on the cyanyl radical. The investigation of the cyanyl radical inhibition mechanism has been carried out.

A study of mitochondria from Caenorhabditis elegans which not only has the G:U pair preserved but also proximal nucleotides that inhibits charging by a nonmitochondrial enzyme is presented. Mitochondrial alanyl-tRNA synthetase from C. elegans has been cloned and its microhelix oligonucleotides have been assessed as substrates for aminoacylation. Results show that G:U recognition continues even with an acceptor helix that does not recognize nonmitochondrial systems. The mitochondrial enzyme is similar to other alanine enzymes including the well-studied Escherichia coli protein.

Research was conducted to study the role of a conspicuous histidine pair H145 and H147 which is conserved among uncoupling protein from the brown adipose tissue of hamster. Mitochondria were isolated from yeast by differential centrifugation while a fluorescence spectrophotometer was utilized to determine H+ uptake activity. Results showed that each histidine partially overcame the H+ conducting barrier and indicated that their combined elimination completely ended H+ transport.

A study was conducted on the purification and characterization of the cytosolic and mitochondrial superoxide dismutase (SOD) from the blue crab, Callinectes sapidus. The findings indicate that the paradigm that all oxygen-respiring eukaryotes have a cystosolic CuZn-SOD and that MnSOD occurs only in the mitochondria is not applicable to a large group of marine arthropods.

Ubiquinol-cytochrome c oxidoreductase ([bc.sub.1] complex) is a component of the eukaryotic, or bacterial respiratory chain and of the photosynthetic apparatus in purple bacteria. In mitochondria, this enzyme catalyzes electron transfer […]

Mitochondrial Ca2+ cycle effect on regulation of Ca2+ uniporter was determined through analysis of the cation release studies of this transporter. Results have shown that ATP acts at a site located on the outer surface of the inner membrane through a mechanism which does not necessitate ATP hydrolysis. Furthermore, phosphate also inhibits reverse uniport under certain conditions.

Mitochondrial anaerobiosis, distribution and ultrastructure were analyzed in Tubificoides benedii (TB) after oxic, hypoxic and hypoxic-sulfidic incubations. Incubation of Tubificoides benedii under normoxic, hypoxic and hypoxic-sulfidic conditions did not alter the ultrastructure and distribution of the mitochondria. Furthermore, mitochodrial anaerobiosis in the oligochaete was not related to mitochondrial morphology.

The effects of the A23187 divalent cation ionophore and Mg2+ ions on mitochondrial respiration were analyzed in rat liver mitochondria. The activity of mitchondrial dehydrogenase was regulated by endogenous mitochondrial Mg2+ ions. Furthermore, mitochondrial respiration was also directly and indirectly affected by the endogenous levels of Mg2+ ions due to changes in the activity of isolated dehydrogenases.

In the structure of bovine mitochondrial [F.sub.1]-ATPase that was previously determined with crystals grown in the presence of adenylyl-imidodiphosphate (AMP-PNP) and ADP, the three catalytic [Beta]-subunits have different conformations and nucleotide occupancies. Adenylyl-imidodiphosphate is bound to one [Beta]-subunit ([[Beta].sub.TP]), ADP is bound to the second ([[Beta].sub.DP]), and no nucleotide is bound to the third ([[Beta].sub.E]). Here we show that the uncompetitive inhibitor aurovertin B binds to bovine [F.sub.1] at two equivalent sites in [[Beta].sub.TP] and [[Beta].sub.E], in a cleft between the nucleotide binding and C-terminal domains. In [[Beta].sub.DP], the aurovertin B pocket is incomplete and is inaccessible to the inhibitor. The aurovertin B bound to [[Beta].sub.TP] interacts with [Alpha]-Glu399 in the adjacent [[Alpha].sub.TP] subunit, whereas the aurovertin B bound to [[Beta].sub.E] is too distant from [[Alpha].sub.E] to make an equivalent interaction. Both sites encompass [Beta]Arg-412, which was shown by mutational studies to be involved in binding aurovertin. Except for minor changes around the aurovertin pockets, the structure of bovine [F.sub.1]-ATPase is the same as determined previously. Aurovertin B appears to act by preventing closure of the catalytic interfaces, which is essential for a catalytic mechanism involving cyclic interconversion of catalytic sites.

Blocking of oxidative phosphorylation by carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone (FCCP) increases Ca2+-activated K+ (K(sub Ca)) channel current and decreases voltage-gated K+ (K(sub v)) current in pulmonary artery myocytes. A reduction in oxidative ATP synthesis appears to be involved in the decrease of the K(sub v) currents. FCCP increases the K(sub Ca) current by increasing intracellular Ca release. FCCP uncouples mitochondrial respiration from ATP formation.

The mitochondria are tuned to oscillating (Ca2+)c signals, the frequency of which can control the CSMDHs over the full range of potential activities. Such signals mediate the extracellular stimuli. Oscillations of (Ca2+)c induced by IP3-dependent hormones are efficiently transmitted to the mitochondria as (Ca2+)m oscillations. Each (Ca2+)m spike was sufficient to cause a maximal transient activation of the CSMDHs and (Ca2+)m oscillations.

Two genes, enzyme pyridine nucleotide transhydrogenase and chaperonin (cpn60), isolated from Entamoeba histolytica show direct evidence for the secondary loss of mitochondrial function. Ribosomal RNA based on phylogenetic analysis of E. histolytica reveal that a homolog of cpc60 is related to mitochondrial lineage.

Programmed cell death (PCD) of thymocytes is the event which causes the negative intrathymic selection of the T-cell repertoire. A multiparametric quantitative analysis on normal or apoptotic thymocytes provides data from a few hours of culture in culture medium or with dexamethasone. Light scattering properties, plasma membrane integrity, chromatin condensation and DNA fragmentation were used to analyze both preapoptotic and apoptotic stages.

Reduced coenzyme Q is the main source of oxygen radical production during the Ca2+-induced mitochondrial membrane permeabilization, following rotenone-induced anoxia. The addition of either ethylene glycol-bis-N,N,N',N'-tetraacetic acid, ruthenium red, catalase, or dithiothreitol before the succinate or oxygen addition, prevented mitochondrial swellings showing the involvement of Ca2+ in the membrane permeabilization.