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)

Rat submandibular cells treated with methylcholanthrene are able to be propagated in continuous culture while retaining beta-adrenergic responsiveness. A specific clone, RSMT-A5, has been isolated and studied in detail. RSMT-A5 cells possess beta-adrenergic receptors (BARS) as judged by [3H]-dihydroalprenolol ([3H]-DHA) binding studies. [3H]-DHA binds to RSMT-A5 membranes in a specific and saturable manner with respect to time and [3H]-DHA concentration. Specific binding is saturable within three min of incubation, and a Scatchard analysis reveals a single class of high affinity binding sites with an equilibrium dissociation constant of 0.62 +/- 0.03 nM and a receptor density of 101 +/- 4 fmole/mg protein. Antagonist competition studies indicate that the BARs are primarily of the beta 2-subtype. The BARs are functional since isoproterenol stimulation results in an increased intracellular cAMP content, marked morphological change, and decreased cell volume and chloride content. These same responses can be evoked by treating RSMT-A5 cells with 8-bromo-cAMP. Ion transport inhibitors such as bumetanide (an inhibitor of Na/K/Cl cotransport), SITS and DIDS (inhibitors of chloride-bicarbonate exchange), amiloride (an inhibitor of Na-H exchange), ouabain (an inhibitor of Na/K-ATPase), and dipyridamole and 9-anthracene carboxylic acid (chloride channel blockers) fail to inhibit the isoproterenol-stimulated change in chloride content. The effects of either isoproterenol or 8-bromo-cAMP on both chloride content and cell volume can be inhibited by the chloride channel blocker N-phenylanthranilic acid, however. Taken together, our results indicate that RSMT-A5 cells possess a beta-adrenergic receptor system which controls intracellular volume and chloride content by modulating transport processes that are 1) cAMP-responsive and 2) inhibitable by the putative chloride channel blocker N-phenylanthranilic acid.
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PMID:Beta-adrenergic control of cell volume and chloride transport in an established rat submandibular cell line. 256 99

1. Antigen-stimulated histamine secretion from rat peritoneal mast cells was inhibited when extracellular chloride was replaced by either isethionate or gluconate anions, but the histamine release still remained quite substantial. 2. Rat peritoneal mast cells take up 36Cl and the uptake reaches a steady state after 60 min incubation with the isotope. At steady state, the intracellular chloride level in the cells was calculated to be 29 +/- 11.5 mM. 3. The chloride uptake in mast cells was exponential with a rate constant of 0.036 min-1 in resting cells. When the cells were stimulated with antigen, and rate constant for chloride uptake increased to 0.90 min-1: an increase of 25 fold. Under identical experimental conditions histamine release increased 3 fold. 4. The rate of chloride uptake in either resting cells or in antigen-stimulated cells was not changed when the extracellular medium was nominally calcium-free but histamine release was almost completely inhibited in the absence of extracellular calcium. 5. The putative chloride channel blocker DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid) 0.3 to 30 microM, produced a concentration-related inhibition of antigen-stimulated histamine secretion but DIDS (30 microM) did not inhibit the antigen-stimulated increase of chloride uptake. 6. The cyclic AMP analogue, dibutyryl cyclic AMP (1 mM) produced a delayed increase in chloride uptake in resting mast cells but neither dibutyryl cyclic AMP nor 8-bromo cyclic AMP per se induced any histamine secretion. 7. Ouabain (1 mM) which inhibits the Na+/K+ ATPase in rat peritoneal mast cells, failed to affect the uptake of chloride in resting mast cells. 8. The Na/K/2C1-cotransport inhibitor, furosemide (0.7 mM), slowed the unstimulated chloride uptake in resting mast cells and abolished the increased antigen-induced chloride uptake when added together with antigen. In contrast, spontaneous and antigen-induced histamine release were unaffected by the presence of furosemide. However, when furosemide was added to the cell suspension 5 min before stimulation, furosemide was without effect on the antigen-induced chloride uptake.9. In addition to the chloride uptake mediated by chloride channels which may be related to the mechanism of histamine secretion, crosslinking of the high affinity membrane receptors for IgE is followed by a fast chloride uptake that is likely to occur through a furosemide-sensitive Na/K/2C1-cotransporter.
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PMID:IgE-receptor activated chloride uptake in relation to histamine secretion from rat mast cells. 751 96

GEF1 encodes the single CLC putative chloride channel in yeast. Its disruption leads to a defect in iron metabolism (Greene, J. R., Brown, N. H., DiDomenico, B. J., Kaplan, J., and Eide, D. (1993) Mol. Gen. Genet. 241, 542-553). Since disruption of GEF2, a subunit of the vacuolar H+-ATPase, leads to a similar phenotype, it was previously suggested that the chloride conductance provided by Gef1p is necessary for vacuolar acidification. We now show that gef1 cells indeed grow less well at less acidic pH. However, no defect in vacuolar acidification is apparent from quinacrine staining, and Gef1p co-localizes with Mnt1p in the medial Golgi. Thus, Gef1p may be important in determining Golgi pH. Systematic alanine scanning of the amino and the carboxyl terminus revealed several regions essential for Gef1p localization and function. One sequence (FVTID) in the amino terminus conforms to a class of sorting signals containing aromatic amino acids. This was further supported by point mutations. Alanine scanning of the carboxyl terminus identified a stretch of roughly 25 amino acids which coincides with the second CBS domain, a conserved protein motif recently identified. Mutations in the first CBS domain also destroyed proper function and localization. The second CBS domain can be transplanted to the amino terminus without loss of function, but could not be replaced by the corresponding domain of the homologous mammalian channel ClC-2.
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PMID:Golgi localization and functionally important domains in the NH2 and COOH terminus of the yeast CLC putative chloride channel Gef1p. 961 22

Several members of the CLC family of Cl- channels and transporters are expressed in vesicles of the endocytotic-lysosomal pathway, all of which are acidified by V-type proton pumps. These CLC proteins are thought to facilitate vesicular acidification by neutralizing the electric current of the H+-ATPase. Indeed, the disruption of ClC-5 impaired the acidification of endosomes, and the knock-out (KO) of ClC-3 that of endosomes and synaptic vesicles. KO mice are available for all vesicular CLCs (ClC-3 to ClC-7), and ClC-5 and ClC-7, as well as its beta-subunit Ostm1, are mutated in human disease. The associated mouse and human pathologies, ranging from impaired endocytosis and nephrolithiasis (ClC-5) to neurodegeneration (ClC-3), lysosomal storage disease (ClC-6, ClC-7/Ostm1) and osteopetrosis (ClC-7/Ostm1), were crucial in identifying the physiological roles of vesicular CLCs. Whereas the intracellular localization of ClC-6 and ClC-7/Ostm1 precluded biophysical studies, the partial expression of ClC-4 and -5 at the cell surface allowed the detection of strongly outwardly rectifying currents that depended on anions and pH. Surprisingly, ClC-4 and ClC-5 (and probably ClC-3) do not function as Cl- channels, but rather as electrogenic Cl--H+ exchangers. This hints at an important role for luminal chloride in the endosomal-lysosomal system.
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PMID:Chloride and the endosomal-lysosomal pathway: emerging roles of CLC chloride transporters. 1711 Apr 6