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PubMed1992

Respiratory chain defect of myocardial mitochondria in idiopathic dilated cardiomyopathy of Doberman pinscher dogs.

Idiopathic dilated cardiomyopathy (IDCM) is a primary myocardial disease of unknown cause. We tested the hypothesis that IDCM was associated with a myocardial metabolic defect by determining a comprehensive biochemical profile of metabolite concentrations and enzyme activities for the major metabolic pathways of the myocardium. We used the Doberman pinscher breed as a naturally occurring canine model of IDCM and compared its myocardial profile with that of healthy adult mongrels. Compared with controls, myocardium in IDCM had markedly reduced mitochondrial electron transport activity and myoglobin concentration, in association with acidosis and energy depletion following anoxic challenge: 60% decreased NADH dehydrogenase and 50% decreased ATP synthetase activities; 90% decreased myoglobin concentration; and 30% reduced ATP and 50% increased lactate and proton concentrations. Sarcoplasmic reticulum Ca(2+)-transport ATPase was decreased by 42%. There was a 15% compensatory increase in fatty acid oxidation and Krebs cycle activity. Other biochemical changes were mild by comparison with the mitochondrial defects. We conclude that IDCM is associated with a marked impairment of mitochondrial production of ATP, arising from decreased activity of the mitochondrial electron transport system, including myoglobin. These changes may be secondary to an underlying genetic defect or may indicate a deficiency of the mitochondrial respiratory chain that predisposes this breed to heart failure.

ATP Synthetase Complexes↗
PubMed1997

Regulation of ATP synthase subunit e gene expression by hypoxia: cell differentiation stage-specific control.

Using the technique of differential display, we identified genes that are expressed differentially under normoxic and hypoxic conditions. One regulated gene encoded subunit e of mitochondrial F1F0-ATP synthase (subunit e). The hypoxia-mediated regulation of subunit e expression in C2C12 cells was influenced by the stage of cellular differentiation. Under normoxic conditions, subunit e expression was markedly upregulated during the transition from myoblast to myotube. After exposure to hypoxia for 24 h, subunit e mRNA expression markedly decreased (>70%) in C2C12 myotubes. In contrast, subunit e mRNA levels increased slightly in response to hypoxia in C2C12 myoblasts. Studies performed with primary rat cardiocytes demonstrated that expression of subunit e mRNA and a cardiac-enriched related transcript was downregulated after a hypoxic exposure. We conclude that expression of subunit e is regulated, at the pretranslational level, by oxygen availability via cell differentiation stage-specific mechanisms consistent with the proposed regulatory role of this protein in cellular ATP production.

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PubMed2004

Endothelial cell surface ATP synthase-triggered caspase-apoptotic pathway is essential for k1-5-induced antiangiogenesis.

We have recently reported the identification of kringle 1-5 (K1-5) of plasminogen as a potent and specific inhibitor of angiogenesis and tumor growth. Here, we show that K1-5 bound to endothelial cell surface ATP synthase and triggered caspase-mediated endothelial cell apoptosis. Induction of endothelial apoptosis involved sequential activation of caspases-8, -9, and -3. Administration of neutralizing antibodies directed against the alpha- and beta-subunits of ATP synthase to endothelial cells attenuated activation of these caspases. Furthermore, inhibitors of caspases-3, -8, and -9 also remarkably blocked K1-5-induced endothelial cell apoptosis and antiangiogenic responses. In a mouse tumor model, we show that caspase-3 inhibitors abolished the antitumor activity of K1-5 by protecting the tumor vasculature undergoing apoptosis. These results suggest that the specificity of the antiendothelial effect of K1-5 is attributable, at least in part, to its interaction with the endothelial cell surface ATP synthase and that the caspase-mediated endothelial apoptosis is essential for the angiostatic activity of K1-5. Thus, our findings provide a mechanistic insight with respect to the angiostatic action and signaling pathway of K1-5 and angiostatin.

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PubMed2006

Angiostatin is directly cytotoxic to tumor cells at low extracellular pH: a mechanism dependent on cell surface-associated ATP synthase.

Angiostatin, a proteolytic fragment of plasminogen, is a potent angiogenesis inhibitor able to suppress tumor growth and metastasis through inhibition of endothelial cell proliferation and migration. Previously, we showed that angiostatin binds and inhibits F(1)F(o) ATP synthase on the endothelial cell surface and that anti-ATP synthase antibodies reduce endothelial cell proliferation. ATP synthase also occurs on the extracellular surface of a variety of cancer cells, where its function is as yet unknown. Here, we report that ATP synthase is present and active on the tumor cell surface, and angiostatin, or antibody directed against the catalytic beta-subunit of ATP synthase, inhibits the activity of the synthase. We show that tumor cell surface ATP synthase is more active at low extracellular pH (pH(e)). Low pH(e) is a unique characteristic of the tumor microenvironment. Although the mechanism of action of angiostatin has not been fully elucidated, angiostatin treatment in combination with acidosis decreases the intracellular pH (pH(i)) of endothelial cells, leading to cell death. We also find that, at low pH(e), angiostatin and anti-beta-subunit antibody induce intracellular acidification of A549 cells, as well as a direct cytotoxicity that is absent in tumor cells with low levels of extracellular ATP synthase. These results establish angiostatin as an antitumorigenic and antiangiogenic agent through a mechanism implicating tumor cell surface ATP synthase. Furthermore, these data provide evidence that extracellular ATP synthase plays a role in regulating pH(i) in cells challenged by acidosis.

ATP Synthetase Complexes↗
PubMedDate not supplied

Kinetic analysis of ATP-synthetase and ATPase in regenerating rabbit liver.

The activities of ATP-synthetase and ATPase in rabbit liver were evaluated by kinetic analysis of rapid changes in ATP during alteration of oxygen supply, and were compared between normal and hepatectomized rabbits. Velocity constants of ATP-synthetase and ATPase were computed on the assumption that ATP-synthetase and ATPase follow the pseudo-first order reaction of ADP and ATP, respectively. The velocity constant of ATPase increased from the control value of 0.21 to 0.48 (min-1) in the remnant rabbit liver at 24 h after 70% hepatectomy. The velocity constant of ATP-synthetase increased from the control value of 4.05 to 5.24 (min-1) after the hepatectomy. These results indicate that both ATP-synthetase and ATPase are accelerated due to liver regeneration.

ATP Synthetase Complexes↗
PubMed2004

Prolinks: a database of protein functional linkages derived from coevolution.

The advent of whole-genome sequencing has led to methods that infer protein function and linkages. We have combined four such algorithms (phylogenetic profile, Rosetta Stone, gene neighbor and gene cluster) in a single database--Prolinks--that spans 83 organisms and includes 10 million high-confidence links. The Proteome Navigator tool allows users to browse predicted linkage networks interactively, providing accompanying annotation from public databases. The Prolinks database and the Proteome Navigator tool are available for use online at http://dip.doe-mbi.ucla.edu/pronav.

ATP Synthetase Complexes↗
PubMed2004

The proton-driven rotor of ATP synthase: ohmic conductance (10 fS), and absence of voltage gating.

The membrane portion of F(0)F(1)-ATP synthase, F(0), translocates protons by a rotary mechanism. Proton conduction by F(0) was studied in chromatophores of the photosynthetic bacterium Rhodobacter capsulatus. The discharge of a light-induced voltage jump was monitored by electrochromic absorption transients to yield the unitary conductance of F(0). The current-voltage relationship of F(0) was linear from 7 to 70 mV. The current was extremely proton-specific (>10(7)) and varied only slightly ( approximately threefold) from pH 6 to 10. The maximum conductance was approximately 10 fS at pH 8, equivalent to 6240 H(+) s(-1) at 100-mV driving force, which is an order-of-magnitude greater than of coupled F(0)F(1). There was no voltage-gating of F(0) even at low voltage, and proton translocation could be driven by deltapH alone, without voltage. The reported voltage gating in F(0)F(1) is thus attributable to the interaction of F(0) with F(1) but not to F(0) proper. We simulated proton conduction by a minimal rotary model including the rotating c-ring and two relay groups mediating proton exchange between the ring and the respective membrane surface. The data fit attributed pK values of approximately 6 and approximately 10 to these relays, and placed them close to the membrane/electrolyte interface.

ATP Synthetase Complexes↗
PubMed2006

Reconstruction of a kinetic model of the chromatophore vesicles from Rhodobacter sphaeroides.

We present a molecular model of a chromatophore vesicle from Rhodobacter sphaeroides. These vesicles are ideal benchmark systems for molecular and systemic simulations, because they have been well studied, they are small, and they are naturally separated from their cellular environment. To set up a photosynthetic chain working under steady-state conditions, we compiled from the experimental literature the specific activities and geometries that have been determined for their constituents. This data then allowed defining the stoichiometries for all membrane proteins. This article contains the kinetic part of the reconstructed model, while the spatial reconstruction is presented in a companion article. By considering the transport properties of the Cytochrome c(2) and ubiquinone pools, we show that their size and oxidation states allow for an efficient buffering of the statistical fluctuations that arise from the small size of the vesicles. Stoichiometric and kinetic considerations indicate that a typical chromatophore vesicle of Rb. sphaeroides with a diameter of 45 nm should contain approximately five bc(1) monomers.

ATP Synthetase Complexes↗
PubMed2005

Preliminary proteomic analysis of Thiobacillus ferrooxidans growing on elemental sulphur and Fe2+ separately.

Thiobacillus ferrooxidans is one of the most important bacterium used in bioleaching, and can utilize Fe2+ or sulphide as energy source. Growth curves for Thiobacillus ferrooxidans have been tested, which show lag, logarithmic, stationary and aging phases as seen in other bacteria. The logarithmic phases were from 10 to 32 hours for Thiobacillus ferrooxidans cultivated with Fe2+ and from 4 to 12 days for Thiobacillus ferrooxidans cultivated with elemental sulphur. Differences of protein patterns of Thiobacillus ferrooxidans growing on elemental sulphur and Fe2+ separately were investigated after cultivation at 30 degrees C by the analysis of two-dimensional gel electrophoresis (2-DE), matrix-assisted laser desorption/ ionization (MALDI)-Mass spectrometry and ESI-MS/MS. From the 17 identified protein spots, 11 spots were found more abundant when growing on elemental sulphur. By contrast 6 protein spots were found decreased at elemental cultivation condition. Among the proteins identified, cytochrome C have been previously identified as necessary elements of electron-transferring pathway for Thiobacillus ferrooxidans to oxidize Fe2+; ATP synthase alpha chain and beta are expressed increased when Thiobacillus ferrooxidans cultivated with Fe2+ as energy source. ATP synthase Beta chain is the catalytic subunit, and ATP synthase alpha chain is a regulatory subunit. The function of ATPase produces ATP from ADP in the presence of a proton gradient across the membrane.

ATP Synthetase Complexes↗
PubMed1992

[The spatial distribution of mitochondrial respiration and oxidative phosphorylation along the small intestine in rats of different ages].

Growing rats were shown to have the maximum of respiratory and ATP-synthetase activities in the duodenum and proximal part of the small intestine, the minimum--in its distal part, whereas the medial part of the intestinal tube was in intermediate position. These parameters were equally distributed along the small intestine in adult rats. In old rats, the highest rate of oxygen consumption was revealed in the mitochondria of the medial part, the lower one--in the proximal part, and the lowest level was found in the duodenum and in distal part of the small intestine.

2,4-Dinitrophenol↗
PubMed2004

The contribution of uncoupling protein and ATP synthase to state 3 respiration in Acanthamoeba castellanii mitochondria.

Mitochondria of the amoeba Acanthamoeba castellanii possess a free fatty acid-activated uncoupling protein (AcUCP) that mediates proton re-uptake driven by the mitochondrial proton electrochemical gradient. We show that AcUCP activity diverts energy from ATP synthesis during state 3 mitochondrial respiration in a fatty acid-dependent way. The efficiency of AcUCP in mitochondrial uncoupling increases when the state 3 respiratory rate decreases as the AcUCP contribution is constant at a given linoleic acid concentration while the ATP synthase contribution decreases with respiratory rate. Respiration sustained by this energy-dissipating process remains constant at a given linoleic acid concentration until more than 60% inhibition of state 3 respiration by n-butyl malonate is achieved. The present study supports the validity of the ADP/O method to determine the actual contributions of AcUCP (activated with various linoleic acid concentrations) and ATP synthase in state 3 respiration of A.castellanii mitochondria fully depleted of free fatty acid-activated and describes how the two contributions vary when the rate of succinate dehydrogenase is decreased by succinate uptake limitation.

ATP Synthetase Complexes↗
PubMed2004

AT1 receptor blockade alters metabolic, functional and structural proteins after reperfused myocardial infarction: detection using proteomics.

Angiotensin II (AngII) type 1 receptor (AT1R) blockers (ARBs) limit left ventricular (LV) dysfunction and necrosis after reperfused myocardial infarction (RMI) and proteomics can detect changes in protein levels after injury. We applied proteomics to detect changes in levels of specific protein in the ischemic zone (IZ) and non-ischemic zone (NIZ) of dog hearts after in vivo RMI (90 min of anterior ischemia; 120 min of reperfusion) and treatment with intravenous vehicle (control) and the ARBs valsartan or irbesartan (10 mg/kg) over 30 min before RMI. We also assessed LV function, infarction and apoptosis. Both ARBs limited the RMI-induced LV dysfunction, infarct size and apoptosis. Proteomics detected differential expression of 5 randomly selected proteins in the IZ compared to the NIZ after RMI: decrease in a subunit of ATP synthase isoform precursor (consistent with increased conversion to a subunit under metabolic stress), M chain creatine kinase (consistent with cellular damage) and ventricular myosin light chain-1 (consistent with structural damage and decreased contractility); and increase in NAD+ -isocitrate dehydrogenase (ICDH) and alpha subunit and ATP synthase D chain (mitochondrial, consistent with metabolic dysfunction). Importantly, changes in NAD+ -ICDH and ATP synthase D chain were reversed by ARB therapy. Thus, proteomics can detect regional changes in metabolic, contractile, and structural proteins after RMI and several of these proteins are favorably modified by ARBs, suggesting that they may be novel therapeutic targets.

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