Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.3.14 (ATP synthase)
7,042 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The regulation of cholesterol side-chain cleavage enzyme (P450scc) by glucocorticoids was investigated in mouse Leydig cell cultures. We recently demonstrated that P450scc is constitutively synthesized in Leydig cells and that the rate of P450scc synthesis is increased by chronic treatment of the cultures with 8-bromo-cAMP. We now report that glucocorticoids, specifically, decrease the constitutive and cAMP-induced synthesis of P450scc protein as well as the accumulation of P450scc mRNA. The treatment of cultures with as little as 10 nM dexamethasone resulted in a 50-60% decrease in the rate of synthesis of P450scc protein and mRNA content. The glucocorticoid-mediated decrease in P450scc synthesis was prevented when cultures were treated with the antiglucocorticoid RU-486. RU-486 alone had no effect on the rate of protein synthesis. The effect was specific for glucocorticoids; corticosterone (100 nM) or cortisol (100 nM) brought about a similar decrease as dexamethasone. Treatment of cultures with the progesterone agonist R5020 (100 nM), testosterone (2 microM), or estradiol (50 nM) had no effect on the rate of specific protein synthesis. The synthesis of iron sulfur protein reductase (ISP-reductase) and F1-ATPase were not affected by dexamethasone, indicating that the effect was specific for P450scc. The amount of P450scc mRNA was decreased 61% by dexamethasone and increased 144% by treatment with 8-bromo-cAMP. These data together with our previous finding on the negative regulation of P450(17 alpha) protein synthesis by testosterone suggest that the steroidogenic P450 enzymes in Leydig cells are negatively regulated by steroid hormones acting via their cognate receptors.
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PMID:Glucocorticoid-mediated repression of P450scc mRNA and de novo synthesis in cultured Leydig cells. 253 67

With a variety of forms of ischemic and toxic tissue injury, cellular accumulation of Ca2+ and generation of oxygen free radicals may have adverse effects upon cellular and, in particular, mitochondrial membranes. Damage to mitochondria, resulting in impaired ATP synthesis and diminished activity of cellular energy-dependent processes, could contribute to cell death. In order to model, in vitro, conditions present post-ischemia or during toxin exposure, the interactions between Ca2+ and oxygen free radicals on isolated renal mitochondria were characterized. The oxygen free radicals were generated by hypoxanthine and xanthine oxidase to simulate in vitro one of the sources of oxygen free radicals in the early post-ischemic period in vivo. With site I substrates, pyruvate and malate, Ca2+ pretreatment, followed by exposure to oxygen free radicals, resulted in an inhibition of electron transport chain function and complete uncoupling of oxidative phosphorylation. These effects were partially mitigated by dibucaine, a phospholipase A2 inhibitor. With the site II substrate, succinate, the electron transport chain defect was not manifest and respiration remained partially coupled. The electron transport chain defect produced by Ca2+ and oxygen free radicals was localized to NADH CoQ reductase. Calcium and oxygen free radicals reduced mitochondrial ATPase activity by 55% and adenine nucleotide translocase activity by 65%. By contrast oxygen free radicals alone reduced ATPase activity by 32% and had no deleterious effects on translocase activity. Dibucaine partially prevented the Ca2+-dependent reduction in ATPase activity and totally prevented the Ca2+-dependent translocase damage observed in the presence of oxygen free radicals. These findings indicate that calcium potentiates oxygen free radical injury to mitochondria. The Ca2+-induced potentiation of oxygen free radical injury likely is due in part to activation of phospholipase A2. This detrimental interaction associated with Ca2+ uptake by mitochondria and exposure of the mitochondria to oxygen free radicals may explain the enhanced cellular injury observed during post-ischemic reperfusion.
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PMID:Mechanism of calcium potentiation of oxygen free radical injury to renal mitochondria. A model for post-ischemic and toxic mitochondrial damage. 287 85

A case of mitochondrial enzymopathy, called also ophthalmoplegia plus, was observed in a 31-year-old man. Histoenzymatic investigations demonstrated in the myocytes decreased and irregularity of reactions for succinic dehydrogenase, tetrazole reductase and mitochondrial ATPase. In electron microscopy paracrystalline structures, lamellar bodies and concentrically condensed cristae were seen in the mitochondria, and increased glycogen stores outside the mitochondria.
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PMID:[A case of mitochondrial enzymopathy]. 297 67

The effects of FSH and (Bu)2cAMP on synthesis of the components of the cholesterol side-chain cleavage (SCC) enzyme complex, namely SCC cytochrome P-450 (P-450scc), the iron-sulfur protein adrenodoxin (ISP), and NADPH:ISP reductase (Red), were investigated in granulosa cells obtained from ovaries of immature estrogen-primed rats cultured for up to 72 h in defined medium in the presence or absence of FSH and (Bu)2cAMP. The cells were lysed, and proteins were subjected to polyacrylamide gel electrophoresis, followed by immunoblotting using antibodies specific to bovine adrenocortical P-450scc, ISP, and Red. A time-dependent increase was observed in the specific contents of these three components of SCC, but not of the reference mitochondrial protein, F1-ATPase, upon treatment with FSH or (Bu)2cAMP. The increase in the content of these three enzymes was accompanied by a rise in progesterone and 20 alpha-hydroxyprogesterone production. The synthesis of P-450scc, ISP, and Red increased 3- to 4-fold with time upon FSH or (Bu)2cAMP treatment respectively, as evidenced by pulse labeling of the cell proteins with [35S]methionine, followed by immunoprecipitation. Immunoprecipitation of P-450scc and ISP from an in vitro translation system programmed by RNA isolated from cultured cells revealed that treatment with FSH or (Bu)2cAMP resulted in an increase in the levels of translatable mRNA specific for these proteins, and that the initial products of translation were precursor forms of cytochrome P-450scc and ISP, similar to those observed in bovine adrenal and granulosa cells. It is concluded that in cultured rat ovarian granulosa cells, FSH induces the synthesis of cytochrome P-450scc, ISP, and Red by increasing the content of translatable mRNA coding for the precursor forms of these enzymes and that this action is mediated by cAMP. Furthermore, the effects of FSH and (Bu)2cAMP provide an explanation for the action of these compounds to stimulate progestin synthesis in cultured ovarian cells.
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PMID:Synthesis of the cholesterol side-chain cleavage enzymes in cultured rat ovarian granulosa cells: induction by follicle-stimulating hormone and dibutyryl adenosine 3',5'-monophosphate. 301 93

A newborn female, the second child of consanguineous parents, exhibited general muscle hypotonia, apathy, hepatomegaly and failure to thrive from birth and signs of craniofacial dysmorphia were present. Pipecolic and trihydroxicoprostanoic acid were excreted in the urine and serum transferrin, ferritin and iron were markedly elevated. At the age of 7 weeks the baby died of respiratory insufficiency. Besides malformations of the brain, renal cysts, liver damage with hypoplastic intrahepatic bile ducts and cholestasis, increased storage of iron and cytochemically proven deficiency of peroxisomes in liver and kidney, morphological studied provided evidence of a mitochondrial myopathy in striated muscle with the accumulation of enlarged bizarre mitochondria, showing only minor structural abnormalities. No defects of NADH-reductase, succinate-dehydrogenase or cytochrome-c-oxidase were demonstrated histochemically. Cytochemical-ultrastructural investigation of mitochondrial ATPase revealed activation of the ATP-synthesising enzyme even before the addition of an uncoupler, this indicating loosely coupled oxidative phosphorylation. In addition a high rate of subcellular autophagy with segregation of mitochondria and focal loss of fibrils was present. Muscle damage in Zellweger syndrome appears to be the consequence of complex, interacting metabolic processes. The mitochondrial myopathy thereby induced allows a better understanding of general muscle hypotonia, one of the leading symptoms of this disorder.
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PMID:Mitochondrial myopathy with loosely coupled oxidative phosphorylation in a case of Zellweger syndrome. A cytochemical-ultrastructural study. 614 41

1. Vesicles from Paracoccus denitrificans were prepared by applying an osmotic shock to spheroplasts derived from cells that had been grown anaerobically with succinate as carbon source and nitrate as electron acceptor. In the presence of either phenazinemethosulphate or N,N,N' N',-tetramethyl-p-phenylenediamine, the oxidation of isoascorbate supported the uptake of both S14CN- and 86Rb+ (in the presence of valinomycin), whereas NADH and succinate oxidation resulted only in S14CN- uptake. These observations show that the preparations contain both right-side-out and inside-out vesicles, and are related to the earlier proposal that the stimulation of an NADH-2,6-dichloroindophenol reductase activity by bee venom is an indicator of the proportion of right-side-out vesicles present. The implications impinge on previous conclusions [Burnell, J. N., John. P. and Whatley, F. R. (1975) Biochem. J. 150, 527-536 and FEBS Lett. 58, 215-218] about the mechanisms of sulphate and phosphate transport in P. denitrificans. 2. The relationship between the protonmotive force (delta p; transmembrane proton electrochemical gradient expressed in mV) and the phosphorylation potential (delta Gp) generated by vesicles from P. denitrificans has been studied as a function of the concentration of an uncoupler of oxidative phosphorylation. With either NADH or succinate as substrate, the uncoupler had a more pronounced effect on delta p than on delta Gp, so that the ratio delta Gp/F x delta p increased within a limited range of values of delta p close to the maximum. delta Gp/F x delta p was, however, approximately constant over the remaining range of delta p that was titrated. A fraction of 'highly coupled' vesicles, separated from the initial preparation by centrifugation through a Ficoll pad, showed similar titration behaviour. This demonstrated that heterogeneity within a vesicle preparation was not responsible for significant distortion of the true relationship between delta p and delta Gp. Values of delta p and delta Gp/F x delta p (H+/ATP) from 143-108 mV and 3.9-4.4, respectively, were determined when NADH was substrate, whereas with succinate, delta p ranged from 123-88 mV and delta Gp/F x delta p (H+/ATP) from 4.5-5.6. The variation in the value of delta Gp/F x delta p, which can be equated with a minimum value for the H+/ATP of the ATP synthase enzyme, is similar to, but less pronounced than, some of the data previously reported for mitochondria. Thus the observations with these bacterial vesicles, which represent an experimentally simpler system than mitochondria, might be taken as further evidence that measurements of the bulk phase delta p might not truly reflect the driving force for ATP synthesis sensed by the ATP synthase enzyme. However, other explanations that would make the data consistent with a chemiosmotic mechanism cannot be eliminated...
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PMID:Characterisation of membrane vesicles from Paracoccus denitrificans and measurements of the effect of partial uncoupling on their thermodynamics of oxidative phosphorylation. 630 33

The effects of BRB-I-28 and its derivatives (GLG-V-13, SAZ-VII-22 and SAZ-VII-23), a novel group of antiarrhythmic agents, were investigated on the rat heart mitochondrial respiratory chain. The results indicate that BRB-I-28 and its derivatives have concentration-dependent inhibitory effects on NADH oxidase and NADH-CoQ reductase (complex I), but they have no significant effects on succinate oxidase, succinate dehydrogenase (complex II), CoQ-cytochrome c reductase (complex III), cytochrome c oxidase (complex IV), and NADH-K3Fe(CN)6 reductase. The site of inhibition of BRB-I-28 and its derivatives on the respiratory chain was localized between flavoprotein n (FPn) and CoQ, which is similar to the effect of rotenone and several other antiarrhythmic drugs such as amiodarone, propranolol, etc. BRB-I-28 and its derivatives also have significant inhibitory effects on mitochondrial ATPase activity as reported for other antiarrhythmic drugs such as amiodarone, propranolol, quinidine, and lidocaine. However, BRB-I-28 and its derivatives have no direct effects on sarcoplasmic reticulum Ca(2+)-ATPase activity. The inhibitory effects of BRB-I-28 and its derivatives on mitochondrial oxidative phosphorylation may result in the depletion of ATP. This effect, in combination with their effects on Na+,K(+)-ATPase, could possibly produce an increase in Ca2+ concentration in cytosol. This may be another mechanism by which these DHBCN derivatives produce an increase in systemic arterial blood pressure and contractile force of isolated cardiac muscle. On the other hand, inhibition on mitochondrial respiration may account for some of the potential toxic effects of these diheterabicyclo[3.3.1]nonane derivatives.
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PMID:Effects of novel antiarrhythmic agents, BRB-I-28 and its derivatives, on the heart mitochondrial respiratory chain and sarcoplasmic reticulum Ca(2+)-ATPase. 799 64

Cytosolic Ca2+ overload may play a key role in the process of lead-induced retinal injury and degeneration. We report that retinal calcium content was elevated following developmental and in vitro lead exposure. To determine the concentration-dependent effects of Ca2+ (5-1000 nM) on retinal mitochondrial bioenergetics an isolation procedure was developed. Isolated mitochondria were efficiently coupled; had good respiratory control ratios with the NAD-linked substrates, glutamate or pyruvate plus malate (G/M or P/M), and the FAD-linked substrate, succinate plus rotenone (S/R); and possessed a Na+/Ca2+ exchanger. The major finding was that at equimolar [Ca2+] > or = 35 nM, mitochondria were more sensitive to and exhibited a greater degree of inhibition of coupled and uncoupled respiration with NAD-linked substrates compared to S/R. At all [Ca2+], decreases in State 3 and uncoupled respiration were similar, thereby eliminating the ATP synthase and ADP/ATP translocase as sites of inhibition and suggesting that opening the mitochondrial permeability transition pore (MTP) did not contribute to the inhibition. The effects of toxicological [Ca2+] were: (1) blocked by ruthenium red, (2) blocked by dibucaine only in the presence of NAD-linked substrates, and (3) partially reversed by NAD+ with G/M after opening the MTP. Results with G/M suggest that Ca2+ acts on the inner membrane phospholipase A2 to decrease NADH CoQ reductase activity and/or produce a NAD+ leak, whereas with S/R, Ca2+ may inhibit succinate dehydrogenase. In conclusion, Ca2+ inhibits retinal mitochondrial ATP production, which may contribute to the retinal cell injury and death observed in developmentally lead-exposed rats.
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PMID:Substrate-dependent effects of calcium on rat retinal mitochondrial respiration: physiological and toxicological studies. 817 38

Bactericidal/permeability-increasing protein [BPI] is a cationic antimicrobial protein from neutrophils that specifically binds to the surfaces of Gram-negative bacteria via the lipid A component of lipopolysaccharide. To obtain information about the responses of Salmonella typhimurium to cell-surface damage by BPI, two-dimensional gel electrophoresis and N-terminal microsequencing were used to identify proteins that were induced or repressed following BPI treatment. The majority of the affected proteins are involved in central metabolic processes. Upon addition of BPI, the beta-subunit of the F1 portion of Escherichia coli ATP synthase was repressed threefold whereas six proteins were induced up to 11-fold. Three of the latter were identified as lipoamide dehydrogenase, enoyl-acyl carrier protein reductase, and the heat-shock protein HtpG. Additionally, a novel protein, BipA, was identified that is induced over sevenfold by BPI; sequence analysis suggests that it belongs to the GTPase superfamily and interacts with ribosomes. A conserved direct-repeat motif is present in the regulatory regions of several BPI-inducible genes, including the bipA gene. Only one of the BPI-responsive proteins was induced when cells were treated with polymyxin B, which also binds to lipid A. We therefore conclude that BPI and polymyxin B affect different global regulatory networks in S. typhimurium even though they bind with high affinity to the same cell-surface component.
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PMID:Salmonella typhimurium responses to a bactericidal protein from human neutrophils. 855 71

The nuclear gene OXA1 was first isolated in Saccharomyces cerevisiae and found to be required at a post-translational step in cytochrome c oxidase biogenesis, probably at the level of assembly. Mutations in OXA1 lead to a complete respiratory deficiency. The protein Oxa1p is conserved through evolution and a human homolog has been isolated by functional complementation of a yeast oxa1- mutant. In order to further our understanding of the role of Oxa1p, we have constructed two yeast strains in which the OXA1 open reading frame was almost totally deleted. Cytochrome spectra and enzymatic activity measurements show the absence of heme aa3 and of a cytochrome c oxido-reductase activity and dramatic decrease of the oligomycin sensitive ATPase activity. Analysis of the respiratory complexes in non-denaturing gels reveals that Oxa1p is necessary for the correct assembly of the cytochrome c oxidase and the ATP synthase complex.
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PMID:The Saccharomyces cerevisiae OXA1 gene is required for the correct assembly of cytochrome c oxidase and oligomycin-sensitive ATP synthase. 861 30


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