Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In neuroblastoma x glioma hybrid NG108-15 cells, ATP induced a concentration-dependent increase in the intracellular Ca2+ concentration ([Ca2+]i), accompanied by inositol phosphate formation. Under the same conditions, we found a marked increase in cAMP levels produced by ATP at concentrations similar to those required to increase [Ca2+]i. The Ca2+ ionophore A23187 or bradykinin, which evoked inositol phosphate formation and increases in [Ca2+]i, did not increase, and instead slightly decreased, cAMP content, indicating that ATP-induced cAMP accumulation was not due to activation of Ca(2+)-sensitive adenylyl cyclase. The effect of ATP on cAMP production was not dependent on generation of adenosine caused by ATP hydrolysis. Among several P2 purinoceptor agonists, adenosine-5'-O-(3-thio)triphosphate, 5'-adenylylimidodiphosphate, and adenosine-5'-O-(2-thio)diphosphate evoked both cAMP accumulation and Ca2+ mobilization. In contrast, beta,gamma-methylene-ATP selectively elicited cAMP accumulation, whereas 2-methylthio-ATP and UTP induced only Ca2+ mobilization, without affecting cAMP levels. The potent P2x purinoceptor agonist alpha,beta-methylene-ATP did not induce cAMP accumulation or Ca2+ mobilization. The cAMP accumulation induced by ATP was not affected by the P2 receptor antagonist suramin but was inhibited by P1 receptor antagonists such as 8-(p-sulfophenyl)theophylline, 3-isobutyl-1-methylxanthine, and xanthine amine congener. However, the ATP-induced increase in [Ca2+]i was not affected by suramin or xanthine amine congener. Taken together, these results indicate that ATP activates two distinct purinoceptors that are coupled to different signal transduction systems, one being adenylyl cyclase and the other phospholipase C, in NG108-15 cells. Furthermore, pharmacological profiles of the adenylyl cyclase-coupled receptor were quite different from those of any known purinoceptor subtypes, especially in the unusual sensitivity of the receptor to P1 and P2 receptor agonists and antagonists. It is therefore suggested that ATP-induced cAMP accumulation may be mediated by a novel subtype of purinoceptor in NG108-15 cells.
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PMID:Extracellular ATP stimulates adenylyl cyclase and phospholipase C through distinct purinoceptors in NG108-15 cells. 772 48

We have investigated the binding of [35S]adenosine 5'-O-(2-thiodiphosphate) ([35S]ADP beta S) to intact cultured bovine aortic endothelial cells which have been previously shown to co-express P2y and P2u purinoceptors and to bovine adrenal medulla endothelial cells which solely possess P2u purinoceptors. ADP beta S has been shown to stimulate phospholipase C activity in these cells via the P2y purinoceptor and does not interact with the P2u purinoceptor. We describe a simple equilibrium binding procedure designed for the study of low affinity agonists and compare these results with those obtained by separation of bound and free by filtration. Saturation analysis of equilibrium binding data revealed two sites for ADP beta S binding; one with KD = 3.3 x 10(-8) M, Bmax = 32 pmol/mg protein; and the other with KD = 4.3 x 10(-6) and Bmax = 2155 pmol/mg protein. Use of filtration did not significantly alter the KD of either of these sites, nor the Bmax of the high affinity site, but reduced the Bmax of the low affinity site by more than 95%. The rank order of agonist potency for competing for [35S]ADP beta S binding indicated that most of this was to non-P2y purinoceptor sites as beta,gamma-methylene ATP, a P2x purinoceptor agonist, was more potent than 2-methylthio ATP, a P2y purinoceptor agonist. Binding was also carried out in the presence of beta,gamma-methylene ATP, in an attempt to reduce non-P2y purinoceptor binding and produced similar results. Specific [35S]ADP beta S binding sites were also found in bovine adrenal medulla endothelial cells which do not possess P2y purinoceptors. These results indicate that [35S]ADP beta S was able to bind to endothelial cells from different parts of the vasculature but that the ligand can only be considered suitable for investigation of P2y purinoceptors on mammalian cells when specific conditions are designed to reduce the large amount of non-receptor binding.
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PMID:Binding of [35S]adenosine 5'-O-(2-thiodiphosphate) to endothelial cells in culture. 776 84

Extracellular ATP secreted from stimulated nerves plays a role in neurotransmission. This study examined the effects of extracellular ATP on phospholipase A2 and C signalling pathways in rabbit astrocytes. ATP caused prostaglandin E2 (PGE2) generation and phosphoinositide hydrolysis in a time- and concentration-dependent manner. A P2y purinoceptor-selective agonist, 2-methylthio-ATP also caused phosphoinositide hydrolysis, but not PGE2 generation. A P2x purinoceptor-selective agonist, alpha, beta-methylene-ATP did not cause either phosphoinositide hydrolysis or PGE2 generation. Although pertussis toxin had no effect on 2-methylthio-ATP-induced phosphoinositide hydrolysis, it markedly decreased ATP-induced PGE2 generation, with significant inhibition of phosphoinositide hydrolysis. Dexamethasone and indomethacin which potently inhibited ATP-induced PGE2 generation, caused partial inhibition of phosphoinositide hydrolysis, suggesting that pertussis toxin-sensitive component of ATP-induced phospholipase C activation is mediated by cyclo-oxygenase metabolites of arachidonic acid. These results suggest that a stimulation of P2y receptor results in phospholipase C activation in a pertussis toxin-insensitive manner, and that a P2 receptor other than the P2y or P2x subtypes is involved in ATP-induced phospholipase A2 activation via a pertussis toxin-sensitive G protein.
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PMID:Effects of ATP on phosphoinositide hydrolysis and prostaglandin E2 generation in rabbit astrocytes. 917 88