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)

The transporters responsible for apical proton secretion were examined in neonatal and adult proximal convoluted tubules (PCT). Transporter activity was assayed from the rate of recovery of cell pH after cell acidification following exposure to NH4Cl. Cell pH was monitored in in vitro perfused tubules using the pH sensitive dye 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein. Recovery from an acid load in adult PCT occurred at 0.52 +/- 0.09 pH units/min in the presence of sodium and 0.25 +/- 0.05 in the absence of sodium (p less than 0.05). One mmol/L N-ethylmaleimide, an inhibitor of the H(+)-ATPase, inhibited the sodium-independent pH recovery from an acid load consistent with a H(+)-ATPase on the apical membrane. In neonatal PCT, recovery from an acid load was 0.39 +/- 0.08 pH units/min in the presence of sodium and only 0.08 pH units/min in the absence of sodium (p less than 0.05). Studies using 4 mmol/L luminal amiloride, an inhibitor of the Na+/H+ antiporter, were consistent with a larger fraction of pH recovery from an acid load in neonatal PCT being due to the Na+/H+ antiporter compared with adult PCT. Thus, maturation of the PCT involves an increase in activity of a sodium-independent proton secretory mechanism, presumably the H(+)-ATPase.
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PMID:Developmental changes in rabbit juxtamedullary proximal convoluted tubule acidification. 131 22

A 5.6-kb fragment of alkaliphilic Bacillus firmus OF4 DNA was isolated by screening a library of total genomic DNA constructed in pGEM3Zf(+) for clones that reversed the Na+ sensitivity of Escherichia coli NM81, in which the gene encoding an Na+/H+ antiporter (NhaA) is deleted (E. Padan, N. Maisler, D. Taglicht, R. Karpel, and S. Schuldiner, J. Biol. Chem. 264:20297-20302, 1989). The plasmid, designated pJB22, contained two genes that apparently encode transposition functions and two genes that are apparent homologs of the cadA and cadC genes of cadmium resistance-conferring plasmid pI258 of Staphylococcus aureus. E. coli NM81 transformed with pJB22 had enhanced membrane Na+/H+ antiporter activity that was cold labile and that decreased very rapidly following isolation of everted vesicles. Subclones of pJB22 containing cadC as the only intact gene showed identical complementation patterns in vivo and in vitro. The cadC gene product of S. aureus has been proposed to act as an accessory protein for the Cd2+ efflux ATPase (CadA) (K. P. Yoon and S. Silver, J. Bacteriol. 173:7636-7642, 1991); perhaps the alkaliphile CadC also binds Na+ and enhances antiporter activity by delivering a substrate to an integral membrane antiporter. A 6.0-kb fragment overlapping the pJB22 insert was isolated to complete the sequence of the cadA homolog. A partial sequence of a region approximately 2 kb downstream of the cadA locus shares sequence similarity with plasmids from several gram-positive bacteria. These results suggest that the region of alkaliphile DNA containing the cadCA locus is present on a transposon that could reside on a heretofore-undetected endogenous plasmid.
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PMID:The cadC gene product of alkaliphilic Bacillus firmus OF4 partially restores Na+ resistance to an Escherichia coli strain lacking an Na+/H+ antiporter (NhaA). 132 Nov 15

Proton transport by the vanadate-sensitive ATPase in plasma membrane (PM) vesicles from the marine unicellular microalga Platymonas viridis was investigated. The ATP-dependent generation of delta pH across the membranes of PM vesicles was followed by the changes in the absorbance of the aminoacridine probe, Acridine orange. Na+ caused the decay of delta pH generated by the ATPase, the rate of the decay being dependent on the concentrations of Na+ added. The phenomenon was specific for Na+. Amiloride inhibited Na(+)-dependent delta pH decay. The experiments support the idea of a Na(+)-extruding mechanism (H(+)-translocating ATPase plus Na+/H+ antiporter) operating in the PM of marine alga Pl. viridis.
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PMID:H(+)-translocating ATPase and Na+/H+ antiport activities in the plasma membrane of the marine alga Platymonas viridis. 132 76

Cells from the inner stripe of the rabbit outer medullary collecting duct (OMCDi) were grown in primary culture, and their acid-base transport properties were characterized using intracellular pH (pHi) measurements with the fluorescent probe 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF). Basal pHi in HCO(3-)-buffered solutions was 7.28 +/- 0.04 (n = 20). The presence of a Cl-/HCO(3-)-antiporter was demonstrated by reversible alkalinization on bath Cl- removal. The mean alkalinization seen on Cl- removal was 0.16 +/- 0.02 pH units (n = 20) and was inhibited 92% by 10(-4) M 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. Studies were also performed to determine the presence of an Na+/H+ antiporter and an H(+)-adenosinetriphosphatase (H(+)-ATPase). After an NH4Cl acid load the cells exhibited both Na(+)-dependent and Na(+)-independent pHi recovery mechanisms. The Na(+)-dependent mechanism was inhibited by amiloride. The Na(+)-independent mechanism was completely inhibited by 10(-3) M N-ethylmaleimide or 2.5 x 10(-9) M bafilomycin A1, but was not significantly altered by removal of bathing solution K+. Thus, the Na(+)-dependent recovery mechanism exhibited characteristics of an Na+/H+ antiporter, whereas the Na(+)-independent recovery mechanism was consistent with the presence of an H(+)-ATPase.
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PMID:Characterization of acid-base transporters in cultured outer medullary collecting duct cells. 133 12

Cells of Methanohalophilus halophilus swelled when exposed to hypotonic solutions of NaCl at pH 7.0. The swelling of the cells ceased in the presence of Mg2+. Methane formation by non-growing cells was strongly dependent on the NaCl concentration. Among other monovalent and divalent cations only Li+ and Mg2+ could partly substitute for a specific function of sodium ions. The artificial Na+/H+ antiporter, monensin, exerted a strong inhibitory effect on methane formation from methylamine. The membrane-bound Mg(2+)-stimulated ATPase of these cells was enhanced at low (40 mM) NaCl concentration while higher concentrations of this solute were inhibitory. The results obtained show that sodium ions are a prerequisite for optimal methane formation and ATPase activity in these cells. However, both of these processes required different sodium ion concentrations.
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PMID:Mode of sodium ion action on methanogenesis and ATPase of the moderate halophilic methanogenis bacterium Methanohalophilus halophilus. 153 42

The role of Na+/K+ exchange in regulating lipopolysaccharide (LPS)-mediated induction of cytokine gene expression has been examined in murine peritoneal macrophages. Depletion of K+ from the culture medium resulted in a three- to five-fold potentiation of tumor necrosis factor-alpha (TNF alpha), KC (gro), and IP-10 mRNA expression in LPS-treated macrophages. The potentiating effect was apparently the result of inhibition of Na+/K+ exchange through the Na+/K(+)-adenosine triphosphatase (ATPase) because ouabain-mediated inhibition of Na+/K(+)-ATPase was also able to potentiate cytokine mRNA expression as much or more than did K+ depletion. The effects of K+ depletion or ouabain treatment were not caused by depolarization of the macrophage membrane because depolarization mediated by elevating extracellular K+ levels was inhibitory to cytokine mRNA expression. Depletion of Na+ by substitution with choline in the culture medium also markedly potentiated LPS-induced gene expression. The Na+/H+ antiporter was not, however, involved in potentiating cytokine expression because treatment of macrophages with amiloride either had no effect on or was inhibitory to the LPS-induced changes in mRNA levels. The potentiation of gene expression was selective and was at least partially the result of increased transcriptional activity of each gene. Whereas Na+ depletion and ouabain both inhibited 86Rb+ uptake by macrophages, treatment with LPS had no effect either on Rb+ uptake or on efflux. Thus altered Na+/K+ exchange is not a component of the primary signalling pathway(s) mediating response to LPS. Nevertheless, modulation of macrophage Na+/K+ exchange by agents encountered during an inflammatory response may be an important determinant of the magnitude and quality of specific gene expression.
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PMID:Modulation of Na+/K+ exchange potentiates lipopolysaccharide-induced gene expression in murine peritoneal macrophages. 165 Mar 75

The rat MTAL secretes protons into the tubular fluid and thus absorbs bicarbonate at substantial rates. Yet the cellular mechanisms of H+/HCO3- transport in the rat MTAL remain largely unsettled. We have performed intracellular pH recovery studies with use of the fluorescent probe BCECF in suspensions of rat MTAL fragments. Luminal H+ secretion occurs by two mechanisms (each responsible for 50% of the normal pHi recovery rate): (1) an electroneutral Na+/H+ antiporter that has an Na-Km of about 11 mM and is inhibited by amiloride (Ki = 2.8 x 10(-5) M); (2) a primary H+ pump that is inhibited by 10(-4) M NEM and 10(-4) M omeprazole, but not by 10(-4) M vanadate or removal of external K. These results suggest the presence of a vacuolar H(+)-ATPase rather than a H(+)-K(+)-ATPase. Basolateral HCO3 exit occurs predominantly by a Cl(-)- and Na(+)-independent electroneutral K+/HCO3- symporter, that has an HCO3-Km of about 17 mM, and is partially inhibited by 10(-4) M DIDS. Basolateral HCO3- efflux was not accompanied by variations of membrane potential monitored with the Em-sensitive fluorescent probe DIS-C3-5, and was not affected by maneuvers that depolarize the cells. It was strongly inhibited by cellular K depletion and dependent on transmembrane K gradient. We conclude that the rat MTAL should secrete protons through both Na+/H+ antiporter and H(+)-ATPase, and that basolateral HCO3- exit should occur through an electroneutral K+/HCO3- symporter.
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PMID:Mechanisms of H+/HCO3- transport in the medullary thick ascending limb of rat kidney. 165 72

Strain F, a recently isolated ruminal bacterium, grew rapidly with glutamate or glutamine as an energy source in the presence but not the absence of Na. Monensin, a Na+/H+ antiporter, completely inhibited bacterial growth and significantly reduced ammonia production (85%), but 3,3',4',5-tetrachlorosalicylanide (a protonophore) and valinomycin had little effect on growth or ammonia production. Dicyclohexylcarbodiimide, a H(+)-ATPase, inhibitor had no effect. The kinetics of glutamate and glutamine transport were biphasic, showing unusually high rates at high substrate concentrations. On the basis of low substrate concentrations (less than 100 microM), the Km values for glutamate and glutamine were 4 and 11 microM, respectively. Strain F had separate carriers for glutamate and glutamine which could be driven by a chemical gradient of Na. An artificial delta psi was unable to drive transport even when Na was present. The glutamate carrier had a single binding site for Na with a Km of 21 mM; the glutamine carrier appeared to have more than one binding site, and the Km was 2.8 mM. Neither carrier could use Li instead of Na. Histidine and serine were also rapidly transported by Na-dependent systems, but serine alone did not allow growth even when Na was present. Because exponentially growing cells at pH 6.9 had little delta psi (-3 mV) and a slightly reversed Z delta pH (+17 mV), it appeared that the membrane bioenergetics of strain F were solely dependent on Na circulation.
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PMID:Transport and deamination of amino acids by a gram-positive, monensin-sensitive ruminal bacterium. 197 63

We have examined the effects of inhibitors of proton transport systems on osteoclastic bone resorption using an in vitro bone slice assay, where osteoclasts (OCs) are free from the influence of other bone cells. Amiloride (AM) and dimethylamiloride (DMA), inhibitors of the Na+/H+ antiporter, were potent inhibitors of bone resorption (IC50 approximately 9 and 0.7 microM for AM and DMA, respectively). Omeprazole (OM), a potent inhibitor of parietal cell K+/H+(-)ATPase, was a poor inhibitor of OC bone resorption (IC50 approximately 100 microM). These results strongly suggest that the Na+/H+ antiporter is the primary proton system used by OCs during bone resorption.
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PMID:Na+/H+ antiporter is the primary proton transport system used by osteoclasts during bone resorption. 215 8

During the early period after poliovirus infection of HeLa cells, cellular Na+/K+ ATPase activity is transiently activated. We investigated the possibility that Na+/K+ ATPase activation is a consequence of Na+/H+ antiporter activation. Increased uptake of the weak organic acid 5,5-dimethyloxazolidine-2,4-dione by infected cells around 2 h after infection suggested cytoplasmic alkalinization equivalent to pH 7.7 during the biosynthetic phase of viral replication. Consistent with the involvement of Na+/H+ antiporter activation in this phenomenon, it was found to be [Na+]-dependent and inhibited by 5-(N-ethyl-N-isopropyl)amiloride (EIPA). However, the pH increase was not associated with an increase in amiloride-sensitive Na+ uptake by infected cells predicted by this mechanism. By contrast, the alkalinization could be abolished with the anion-exchange inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), implicating an anion-exchange mechanism, such as Cl-/HCO3- exchange, in this process. In addition to abolishing virus-induced intracellular alkalinization, both EIPA and DIDS moderately inhibited viral replication. Manipulation of intracellular pH with nigericin in the incubation medium revealed that maximum viral replication required a pH of about 7.7 and that replication was significantly inhibited even at pH 7.3. Thus, the pH increase in infected cells appeared to be physiologically relevant. These findings represent the first demonstration of a biologically meaningful pH increase in cells infected with a lytic virus.
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PMID:Evidence for poliovirus-induced cytoplasmic alkalinization in HeLa cells. 215 10


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