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:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A functional approach was utilized to isolate protein effectors from cAMP-stimulated rabbit gastric microsomes capable of stimulating H(+)-K(+)-ATPase activity. These studies have resulted in isolation of a cAMP-dependent protein kinase product from rabbit gastric microsomes which is capable of stimulating the proton pump of the parietal cell, H(+)-K(+)-ATPase, in inhibited gastric microsomes. This protein is membrane-bound and may be extracted from gastric microsomes only in the phosphorylated state. This phosphoprotein has at least 20 phosphorylation sites and produces enhancement of H(+)-K(+)-ATPase activity which equals that induced by the K+ ionophore, valinomycin. It would appear, therefore, that cAMP-mediated acid secretion involves phosphorylation of a membrane-bound cAMP-dependent protein kinase substrate in close proximity to the proton pump which produces K+ conductance and thereby controls the rate of acid secretion. The degree of phosphorylation of this protein is probably controlled by the activities of cAMP-dependent protein kinase and phosphoprotein phosphatase.
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PMID:Regulation of gastric H(+)-K(+)-ATPase by cAMP-dependent protein kinase. 841 3

We have investigated the effect of genistein on the hormone-stimulated Ca2+ influx and on a 28pS nonselective cation channel in mouse pancreatic acinar cells using the Ca2+ indicator fluo3 and the patch-clamp technique. The identity of the Ca2+ influx pathway has not been established in this cell type so far. Therefore we have investigated the Ca2+-dependent nonselective cation channel as a potential pathway for Ca2+ influx. Capacitative Ca2+ entry was induced by depletion of intracellular Ca2+ stores with 500nM acetylcholine or with the Ca2+ ATPase inhibitor 2,5di-tert- butylhydroquinone. In the presence of 100microM genistein, Ca2+ release was unimpaired, whereas Ca2+ influx was reversibly suppressed. Patch-clamp experiments demonstrated that genistein had no effect on Ca2+-activated nonselective cation channels, the activity of which was measured in excised membrane patches (inside/out) or in the whole-cell configuration. Therefore we conclude that this 28pS nonselective cation channel does not contribute to Ca2+ influx into mouse exocrine pancreatic cells. With the exception of genistein and tyrphostin 25, other tyrosine kinase inhibitors such as methyl-2,5-dihydroxycinnamate, lavendustin A, herbimycin A, and tyrphostin B56 were without effect on Ca2+ signalling. Thus, the involvement of tyrosine phosphorylation in the activation of the Ca2+ entry mechanism in mouse pancreatic acinar cells is unclear.
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PMID:Capacitative Ca2+ influx and a Ca2+-dependent nonselective cation pathway are discriminated by genistein in mouse pancreatic acinar cells. 859 44

The salt-sensitive phenotype of yeast cells deficient in the phosphoprotein phosphatase, calcineurin, was used to identify genes from the higher plant Arabidopsis thaliana that complement this phenotype. cDNA clones corresponding to two different sequences, designated STO (salt tolerance) and STZ (salt tolerance zinc finger), were found to increased tolerance of calcineurin mutants and of wild-type yeast to both Li+ and Na+ ions. STZ is related to Cys2/His2-type zinc-finger proteins found in higher plants, and STO is similar to the Arabidopsis CONSTANS protein in regions that may also be zinc fingers. Although neither protein has sequence similarity to any protein phosphatase, STO was able to at least partially compensate for all tested additional phenotypic effects of calcineurin deficiency, and STZ compensated for a subset of these effects. Salt tolerance produced by STZ appeared to be partially dependent on ENA1/PMR2, a P-type ATPase required for Li+ and Na+ efflux in yeast, whereas the effect of STO on salt tolerance was independent of ENA1/PMR2. STZ and STO were found to be expressed in Arabidopsis roots and leaves, whereas only STO message was detectable in flowers. An apparent increase in the level of STZ mRNA was observed in response NaCl exposure in Arabidopsis seedlings, but the level of STO mRNA was not altered by this treatment.
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PMID:Two classes of plant cDNA clones differentially complement yeast calcineurin mutants and increase salt tolerance of wild-type yeast. 866 38

1. We have investigated interactions between intracellular pH (pHi) and the intracellular free calcium concentration ([Ca2+]i) in collagenase-isolated rat lacrimal acinar cells. The fluorescent dyes fura-2 and 2',7'-bis(carboxyethyl)-5-carboxyfluorescein (BCECF) were used to measure [Ca2+]i and pHi, respectively. 2. Application of the weak base NH4Cl alkalinized the cytosol and caused a dose-dependent increase in [Ca2+]i. Trimethylamine (TMA) also alkalinized the cytosol and increased [Ca2+]i. The increase in [Ca2+]i evoked by NH4Cl or TMA was much smaller than that evoked by the secretory agonist acetylcholine (ACh). 3. Application of NH4Cl also increased [Ca2+]i in cells bathed in Ca(2+)-free medium, indicating that NH4Cl released Ca2+ from an intracellular pool. 4. Ammonium chloride had no effect on [Ca2+]i in cells bathed in Ca(2+)-free medium if agonist-sensitive intracellular Ca2+ pools had been depleted with either ACh or the microsomal Ca(2+)-ATPase inhibitor 2,5-di(tert-butyl)hydroquinone. Treatment of cells with NH4Cl in Ca(2+)-free medium reduced the amount of Ca2+ released by ACh. These results suggest that NH4Cl released Ca2+ from the same intracellular pool released by ACh. 5. Calcium release from the agonist-sensitive pool was also triggered when the cytosol was alkalinized by removing the weak acid acetate. 6. Ammonium chloride caused a modest increase in inositol phosphate production, suggesting that NH4Cl may have released stored Ca2+ via an increase in the intracellular inositol 1,4,5-trisphosphate concentration. 7. The increase in [Ca2+]i evoked by NH4Cl was not sustained even in the presence of extracellular Ca2+. In contrast, when a low dose of ACh was used to evoke intracellular Ca2+ release of similar magnitude, sustained Ca2+ entry was observed. 8. Alkalinizing the cytosol appeared to partially inhibit Ca2+ entry triggered by thapsigargin or by ACh. 9. We suggest that alkalinizing the cytoplasm in unstimulated lacrimal acinar cells can release Ca2+ from the intracellular agonist-sensitive Ca2+ pool. However, releasing stored Ca2+ via alkalinization does not appear to trigger significant Ca2+ entry, perhaps because intracellular alkalinization inhibits either the Ca2+ entry pathway or the mechanism which couples the entry pathway to store depletion.
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PMID:Intracellular alkalinization mobilizes calcium from agonist-sensitive pools in rat lacrimal acinar cells. 913 Jan 57

The growth of fission yeast cultures was reversibly inhibited by exposure to the myosin-ATPase inhibitor 2,3-butanedione-2-monoxime (BDM). Wild-type cells treated with 20 mM BDM for approximately two generation times were smaller than untreated controls and had a septation index approximately twice that seen in the absence of the inhibitor. The organization of actin at the cell poles was somewhat disorganized in the presence of BDM; however, cells formed a cytokinetic actin ring. When nitrogen-starved stationary-phase cells were reinoculated into fresh medium in the presence of BDM, the time taken to repolarize the actin cytoskeleton and to resume the characteristic vegetative cell shape before initiation of the first cell division were both substantially delayed. BDM significantly inhibited the increase in cell length of cdc25.22 cells arrested for cell cycle progress by incubation at the restrictive temperature and substantially delayed the initiation of both mitosis and cytokinesis in arrested cdc25.22 cells after release of the temperature block. These results suggest that tip growth and cytokinesis--processes in fission yeast that involve the actin cytoskeleton--also require myosin activity.
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PMID:The myosin ATPase inhibitor 2,3-butanedione-2-monoxime (BDM) inhibits tip growth and cytokinesis in the fission yeast, Schizosaccharomyces pombe. 978 87

SERCA1a, the fast-twitch skeletal muscle isoform of sarco(endo)plasmic reticulum Ca(2+)-ATPase, was expressed in yeast using the promoter of the plasma membrane H(+)-ATPase. In the yeast Saccharomyces cerevisiae, the Golgi PMR1 Ca(2+)-ATPase and the vacuole PMC1 Ca(2+)-ATPase function together in Ca2+ sequestration and Ca2+ tolerance. SERCA1a expression restored growth of pmc1 mutants in media containing high Ca2+ concentrations, consistent with increased Ca2+ uptake in an internal compartment. SERCA1a expression also prevented synthetic lethality of pmr1 pmc1 double mutants on standard media. Electron microscopy and subcellular fractionation analysis showed that SERCA1a was localized in intracellular membranes derived from the endoplasmic reticulum. Finally, we found that SERCA1a ATPase activity expressed in yeast was regulated by calcineurin, a Ca2+/calmodulin-dependent phosphoprotein phosphatase. This result indicates that calcineurin contributes to calcium homeostasis by modulating the ATPase activity of Ca2+ pumps localized in intra-cellular compartments.
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PMID:Rabbit sarcoplasmic reticulum Ca(2+)-ATPase replaces yeast PMC1 and PMR1 Ca(2+)-ATPases for cell viability and calcineurin-dependent regulation of calcium tolerance. 1002 71

1. The effect of creatine phosphate (PCr) on sarcoplasmic reticulum (SR) Ca2+ regulation was studied in mechanically skinned skeletal muscle fibres from rat extensor digitorium longus (EDL). Preparations were perfused with solutions mimicking the intracellular milieu and the [Ca2+] within the muscle was monitored continuously using fura-2. 2. Brief application of 40 mM caffeine caused a transient increase in [Ca2+] due to SR Ca2+ release, and an associated tension response. Withdrawal of PCr resulted in (i) a slow transient release of Ca2+ from the SR (ii) a marked prolongation of the descending phase of the caffeine-induced fluorescence ratio transient and (iii) a decrease in the Ca2+ transient amplitude to 69.2 +/- 2.7 % (n = 16) of control responses. 3. Prolongation of the caffeine-induced Ca2+ transient also occurred following application of the SR Ca2+ pump inhibitor cyclopiazonic acid (CPA). This suggests that (i) the descending phase of the caffeine-induced Ca2+ transient is dependent on the rate of Ca2+ uptake by the SR and (ii) prolongation associated with PCr withdrawal may also reflect a decrease in the net Ca2+ uptake rate. 4. The effects of PCr withdrawal were mimicked by addition of the creatine kinase (CK) inhibitor 2,4-dinitro-1-fluorobenzene (DNFB). Hence, reducing the [PCr] may influence SR Ca2+ regulation by limiting local ATP regeneration by endogenous CK. After treatment with DNFB, PCr withdrawal had no effect on the Ca2+ transient, confirming that PCr does not have an additional direct effect on the SR. 5. The Ca2+ efflux associated with PCr withdrawal was insensitive to ryanodine or Ruthenium Red, but was effectively abolished by pretreatment with the SR Ca2+ pump inhibitor cyclopiazonic acid (CPA). This suggests that the Ca2+ efflux associated with PCr withdrawal is independent of the SR Ca2+ channel, but may involve reversal or inhibition of the Ca2+ ATPase. 6. These data suggest that Ca2+ regulation by the SR is strongly dependent on the supply of ATP via endogenous CK. Depletion of PCr may contribute to impaired SR Ca2+ regulation known to occur in intact skeletal muscle under conditions of fatigue.
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PMID:Effects of creatine phosphate on Ca2+ regulation by the sarcoplasmic reticulum in mechanically skinned rat skeletal muscle fibres. 1033 94

In root hairs of alfalfa (Medicago sativa), the requirement of Ca(2+) for Nod factor signaling has been investigated by means of ion-selective microelectrodes. Measured 50 to 100 microm behind the growing tip, 0.1 microM NodRm-IV(C16:2,S) increased the cytosolic free [Ca2+] by about 0.2 pCa, while the same concentration of chitotetraose, the nonactive glucosamine backbone, had no effect. We demonstrate that NodRm-IV(C16:2,S) still depolarized the plasma membrane at external Ca(2+) concentrations below cytosolic values if the free EGTA concentration remained low (</=0.01 mM). Externally added Sr(2+) was able to replace Ca(2+), and to some extent even enhanced the Nod-factor-induced depolarization, whereas with Mg(2+) it was decreased. This suggests that the Nod factor response is triggered by Ca(2+) from external stores. The addition of the endomembrane Ca(2+)-ATPase inhibitor 2,5-di(t-butyl)-1, 4-benzohydroquinone, which presumably mobilizes Ca(2+) from Ins(1,4, 5)P(3)-sensitive stores, mimicked the Nod factor response, i.e. increased the cytosolic free [Ca2+], triggered Cl(-)-efflux, depolarized the plasma membrane, and alkalized the root hair space. In all cases a refractory state toward Nod factor perception was produced, indicating a shortcut of Nod factor signal transduction by releasing Ca(2+) from internal stores. These latter results strongly support the idea that an elevation of cytosolic free [Ca2+] is indispensable for the transduction of the Nod factor signal, which is consistent with the role of Ca(2+) as a second messenger.
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PMID:Elevation of the cytosolic free [Ca2+] is indispensable for the transduction of the Nod factor signal in alfalfa. 1048 83

H/K-ATPase preparations (the G1 membrane) from pig stomach contain both kinases and phosphatases and show reversible phosphorylation of Tyr(7), Tyr(10), and Ser(27) residues of the alpha-chain of H/K-ATPase. The Tyr-kinase is sensitive to genistein and quercetin and recognized by anti-c-Src antibody. The Ser-kinase is dependent on Ca(2)(+) (K(0.5) = 0.9 microM), sensitive to a PKC inhibitor, and recognized by antibodies against PKCalpha and PKCbetaII. The addition of 3-[(3-cholamidopropyl)dimethylammonio]-1-propane-sulfonic acid (CHAPS) caused a dramatic increase in the phosphorylation of added synthetic copolymer substrates and permitted the phosphorylation of maltose-binding proteins fused with the N-terminal domain of alpha-chains. The phosphotyrosine phosphatase was inhibited by vanadate. The phosphoserine phosphatase was inhibited by okadaic acid and by inhibitor-2. The presence of protein phosphatase-1 was immunologically detected. Column chromatographic separation of CHAPS-solubilized G1 membrane and others indicate the apparent molecular weight of the Src-kinase to be approximately 60 kDa, the PKCalpha and/or PKCbII to be approximately 80 kDa, the Tyr-phosphatase to be 200 kDa, and PP-1 to be approximately 35 kDa. These data show that these membrane-bound enzyme systems are in sufficiently close proximity to be responsible for reversible phosphorylation of Tyr(7), Tyr(10), and Ser(27) of the catalytic subunit of membrane H/K-ATPase in parietal cells, the physiological role of which is unknown.
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PMID:Membrane enzyme systems responsible for the Ca(2+)-dependent phosphorylation of Ser(27), the independent phosphorylation of Tyr(10) and Tyr(7), and the dephosphorylation of these phosphorylated residues in the alpha-chain of H/K-ATPase. 1078 91

Phosphatidylserine (PS) was exposed at the surface of human umbilical vein endothelial cells (HUVECs) and cultured cell lines by agonists that increase cytosolic Ca(2+), and factors governing the adhesion of T cells to the treated cells were investigated. Thrombin, ionophore A23187 and the Ca(2+)-ATPase inhibitor 2, 5-di-tert-butyl-1,4-benzohydroquinone each induced a PS-dependent adhesion of Jurkat T cells. A23187, which was the most effective agonist in releasing PS-bearing microvesicles, was the least effective in inducing the PS-dependent adhesion of Jurkat cells. Treatment of ECV304 and EA.hy926 cells with EGTA, followed by a return to normal medium, resulted in an influx of Ca(2+) and an increase in adhering Jurkat cells. Oxidised low-density lipoprotein induced a procoagulant response in cultured ECV304 cells and increased the number of adhering Jurkat cells, but adhesion was not inhibited by pretreating ECV304 cells with annexin V. PS was not significantly exposed on untreated Jurkat cells, as determined by flow cytometry with annexin V-FITC. However, after adhesion to thrombin-treated ECV304 cells for 10 min followed by detachment in 1 mM EDTA, there was a marked exposure of PS on the Jurkat cells. Binding of annexin V-FITC to the detached cells was inhibited by pretreating them with unlabelled annexin V. Contact with thrombin-treated ECV304 cells thus induced the exposure of PS on Jurkat cells and, as Jurkat cells were unable to adhere to thrombin-treated ECV304 cells in the presence of EGTA, the adhesion of the two cell types may involve a Ca(2+) bridge between PS on both cell surfaces. The number of T cells from normal, human peripheral blood that adhered to ECV304 cells was not increased by treating the latter with thrombin. However, findings made with several T cell lines were generally, but not completely, consistent with the possibility that adhesion to surface PS on endothelial cells may be a feature of T cells that express both CD4(+) and CD8(+) antigens. Possible implications for PS-dependent adhesion of T cells to endothelial cells in metastasis, and early in atherogenesis, are discussed.
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PMID:Phosphatidylserine-dependent adhesion of T cells to endothelial cells. 1083 84


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