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)

PGJ2 and delta 12PGJ2 (1 microM to 30 microM) inhibited the growth of human astrocytoma cells (1321N1) in a time-dependent manner within 48 hrs, determined by [3H]thymidine incorporation into acid-insoluble fraction or amounts of protein. The EC50 values for PGJ2 and delta 12PGJ2 were approximately 8 microM and 6 microM, respectively. [3H]Thymidine incorporation to acid insoluble fraction was inhibited by these PGs within 1 hr, indicating that these PGs rapidly affect cell functions. Although it has been reported that an increase in cyclic AMP inhibits cell growth, PGJ2 and delta 12PGJ2, but not PGE1, reduced isoproterenol (10 microM)-induced accumulation of cyclic AMP, suggesting that PGJ2 and delta 12PGJ2 may disturb adenylate cyclase system, which might be independent on cell growth. On the other hand, these PGs inhibited the incorporation of [3H]inositol into phospholipid fraction within 6 hrs. Furthermore, PGJ2 and delta 12PGJ2 inhibited carbachol- and/or histamine-induced accumulation of inositol phosphates with a similar dose-dependency to their inhibitions of cell growth. In membrane preparations, however, PGJ2 and delta 12PGJ2 failed to inhibit GTP gamma S (10 microM)- nor Ca2+ (1 mM)-induced accumulation of inositol phosphates. The site of PGJ2 or delta 12PGJ2 in inhibition of inositol phosphate accumulation would not be phospholipase C nor a putative GTP binding protein involved in activation of phospholipase C. The present results indicate that PGJ2 and delta 12PGJ2 inhibit cell growth in human astrocytoma cells and the inhibition of phosphoinositide turnover by these PGs might be involved in the inhibition of cell growth.
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PMID:PGJ2 and delta 12PGJ2 inhibit cell growth accompanied with inhibition of phosphoinositide turnover in human astrocytoma cells. 217 1

We recently reported that prostaglandin (PG) E2 stimulated phosphoinositide metabolism in cultured bovine adrenal chromaffin cells and that PGE2 and ouabain induced a gradual secretion of catecholamines from the cells (Yokohama, H., Tanaka, T., Ito, S., Negishi, M., Hayashi, H., and Hayaishi, O. (1988) J. Biol. Chem. 263, 1119-1122). Here we examined the involvement of two signal pathways, Ca2+ mobilization and protein kinase C activation resulting from phosphoinositide metabolism, in the PGE2-induced catecholamine release. Either the Ca2+ ionophore ionomycin or 12-O-tetradecanoylphorbol 13-acetate (TPA) could enhance the release in the presence of ouabain, and ionomycin-induced release was additive to PGE2-induced release, but TPA-induced release was not additive. PGE2 dose-dependently stimulated the formation of diacylglycerol and caused the translocation of 4% of the total protein kinase C activity to become membrane-bound within 5 min. These effects were specific for PGE2 and PGE1 among PGs tested (PGE2 = PGE1 greater than PGF2 alpha greater than PGD2). Furthermore, the phosphoinositide-specific phospholipase C inhibitor neomycin inhibited PGE2-induced accumulation of inositol phosphates, diacylglycerol formation, translocation of protein kinase C, and also stimulation of catecholamine release. Both PGE2- and TPA-induced release were inhibited by the depletion of protein kinase C caused by prolonged exposure to TPA, but ionomycin-induced release was not inhibited. We recently found that the amiloride-sensitive Na+, H+-antiport participates in PGE2-evoked catecholamine release (Tanaka, T., Yokohama, H., Negishi, M., Hayashi, H., Ito, S., and Hayaishi, O. (1990) J. Neurochem. 54, 86-95). In agreement with our recent report, PGE2 and TPA induced a sustained increase in intracellular pH that was abolished by the protein kinase C inhibitor staurosporine but not by the calmodulin inhibitor W-7. Ionomycin also induced a marked increase in intracellular pH, but this increase was abolished by W-7 but not by staurosporine. These results demonstrate that PGE2-induced activation of the Na+, H(+)-antiport and catecholamine release in the presence of ouabain are mediated by activation of protein kinase C, rather than by Ca2+ mobilization, resulting from phosphoinositide metabolism.
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PMID:Involvement of protein kinase C in prostaglandin E2-induced catecholamine release from cultured bovine adrenal chromaffin cells. 231 53

Adenylate cyclase and phospholipase C activity were examined in platelet membranes obtained from 19 male subjects with combat-related posttraumatic stress disorder (PTSD) and 35 age- and gender-matched healthy controls. Basal and forskolin-stimulated adenylate cyclase activity were significantly lower in the PTSD group whereas aluminum chloride plus sodium fluoride (AlCl3/NaF)- and prostaglandin E1 (PGE1)-stimulated responses were normal. There was no difference in phospholipase C activity between the two groups. The lower basal and forskolin-stimulated adenylate cyclase responses replicate a previous report and suggest that PTSD may be associated with an abnormality of the catalytic subunit of the receptor-adenylate cyclase complex.
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PMID:Platelet adenylate cyclase and phospholipase C activity in posttraumatic stress disorder. 232 69

The biochemical events encompassing the dephosphorylation of protein kinase C substrates by protein kinase A activators have been investigated in a neurotumor cell line, NCB-20. Treatment of [32P]orthophosphate-labeled cells with protein kinase A activators (e.g. forskolin, dibutyryl cAMP, prostaglandin E1) resulted in an inhibition of protein kinase C activity due to a failure of the protein kinase C complex to translocate into the membrane. Phospholipase C activity, as measured by the synchronous release of diacylglycerol and inositol phosphates (inositol 1,4,5-trisphosphate, inositol 1,4-bisphosphate, and inositol 1-phosphate) in response to bradykinin, was inhibited up to 50% following exposure to protein kinase A activators. At the same time, phospholipase C-specific inositol phospholipid substrates (phosphatidylinositol, phosphatidylinositol 4-phosphate, and phosphatidylinositol 4,5-bisphosphate) were found to accumulate in NCB-20 cells following treatment with protein kinase A activators. This suggests that phospholipase C may be altered through protein kinase A-mediated protein phosphorylation. Second messenger generation (inositol phosphates, diacylglycerol, and Ca2+) is therefore inhibited through cyclic AMP-mediated shutdown of the inositol lipid cycle at the level of phospholipase C.
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PMID:Rapid dephosphorylation of protein kinase C substrates by protein kinase A activators results from inhibition of diacylglycerol release. 247 91

The possibility that an increased intracellular concentration of cyclic AMP (cAMP) can regulate the extent of muscarinic receptor-stimulated phosphoinositide (PPI) turnover in the human neuroblastoma cell line SK-N-SH was examined. Addition of either forskolin (or its water-soluble analog, L-85,8051), theophylline, isobutylmethylxanthine, or cholera toxin, agents that interact with either the catalytic unit of adenylate cyclase, cAMP phosphodiesterase, or the guanine nucleotide binding protein linked to adenylate cyclase activation, resulted in a 45-181% increase in cAMP concentration and a 27-70% inhibition of carbachol-stimulated inositol phosphate release. Through the use of digitonin-permeabilized cells, the site of inhibition was localized to a step at, or distal to, the guanine nucleotide binding protein that regulates phospholipase C activity. In contrast, when intact SK-N-SH cells were exposed to prostaglandin E1, the ensuing increases in cAMP were not accompanied by an inhibition of stimulated PPI turnover. These differential effects of increased cAMP concentrations on stimulated PPI turnover may reflect the compartmentation of cAMP within SK-N-SH cells.
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PMID:Muscarinic receptor-stimulated phosphoinositide turnover in human SK-N-SH neuroblastoma cells: differential inhibition by agents that elevate cyclic AMP. 247 99

A part of the GTP gamma S-binding activity in murine thymocyte membranes was found to have affinity to a concanavalin A (Con A)-Sepharose column. The material was identified as Gi (inhibitory GTP-binding protein) on the basis of the molecular weight and by islet activating protein-dependent ADP-ribosylation and anti-alpha i (alpha subunit of Gi) immunoblotting. However, when the membranes prepared from Con A-stimulated thymocytes were used, no GTP gamma S-binding activity was detected in the Con A-bound fraction, suggesting that Gi physically and specifically associated with Con A acceptors dissociates upon Con A stimulation. Furthermore, another GTP gamma S-binding protein (25 kDa), which is quite similar to a novel phosphoinositide-specific phospholipase C (PI-PLC)-associated G protein in calf thymocytes (Wang, P., Toyoshima, S., & Osawa, T. (1988) J. Biochem. 103, 137-142), was detected among the Con A-Sepharose-bound proteins with the chemical cross-linking technique. When the 40 kDa and 25 kDa G proteins associated with Con A receptor(s) were isolated and their direct effects on the activity of partially purified PI-PLC as to phosphatidylinositol 4,5-bisphosphate hydrolysis were examined, the 25 kDa G protein was found to enhance the PI-PLC activity more effectively. On the other hand, pretreatment of cells with islet-activating protein completely abolished the inhibitory effect of Con A on the prostaglandin E1 and isoproterenol-induced increases of cellular cAMP.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Concanavalin A receptor(s) possibly interacts with at least two kinds of GTP-binding proteins in murine thymocytes. 254 73

A wide spectrum of prostaglandins (PG) stimulate both the production of cyclic AMP and an increase in free cytosolic Ca2+ concentration [( Ca2+]i) in the osteogenic osteosarcoma cell line, UMR-106-01, which has characteristics compatible with osteoblasts. Using PG-stimulated determinations of the second messengers cyclic AMP and [Ca2+]i, a method for classification of PG receptors is presented. UMR-106-01 cells demonstrate three subclasses of PG receptors. One receptor interacts with PGF2 alpha, PGD2, and thromboxane B2 (TxB2) to increase [Ca2+]i. A second receptor binds PGE2, PGE1, PGI2, PGA2 and 6-oxo-PGF1 alpha to increase [Ca2+]i by stimulation of a second separate phospholipase C pool. A third receptor accepts PGE2, PGE1, PGA2, PGI2 and to a lesser extent PGF2 alpha, PGD2 and TxB2 to increase cyclic AMP. Such a classification system may be applicable to other cells responding to multiple PGs by inducing changes in cellular second messengers.
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PMID:Classification of prostaglandin receptors based on coupling to signal transduction systems. 255 9

The action of carbamoylcholine (Cchol), NaF and other agonists on the generation of inositol phosphates (IPs) was studied in dog thyroid slices prelabelled with myo-[2-3H]inositol. The stimulation by Cchol (0.1 microM-0.1 mM) of IPs accumulation through activation of a muscarinic receptor [Graff, Mockel, Laurent, Erneux & Dumont (1987) FEBS Lett. 210, 204-210] was pertussis- and cholera-toxin insensitive. Ins(1,4,5)P3, Ins(1,3,4)P3 and InsP4 were generated. NaF (5-20 mM) also increased IPs generation (Graff et al., 1987); this effect was potentiated by AlCl3 (10 microM) and unaffected by pertussis toxin. Although phorbol dibutyrate (5 microM) abolished the cholinergic stimulation of IPs generation (Graff et al., 1987), it did not affect the fluoride-induced response. Cchol and NaF did not require extracellular Ca2+ to exert their effect, and neither KCl-induced membrane depolarization nor ionophore A23187 (10 microM) had any influence on basal IPs levels, or on cholinergic stimulation. However, more stringent Ca2+ depletion with EGTA (0.1 or 1 mM) decreased basal IPs levels as well as the amplitude of the stimulation by Cchol without abolishing it. Dibutyryl cyclic AMP, forskolin, cholera toxin and prostaglandin E1 had no effect on basal IPs levels and did not decrease the response to Cchol. Iodide (4 or 40 microM) also strongly decreased the cholinergic action on IPs, this inhibition being relieved by methimazole (1 mM). Our data suggest that Cchol activates a phospholipase C hydrolysing PtdIns(4,5)P2 in the dog thyroid cell in a cyclic AMP-independent manner. This activation requires no extracellular Ca2+ and depends on a GTP-binding protein insensitive to both cholera toxin and requires no extracellular Ca2+ and depends on a GTP-binding protein insensitive to both cholera toxin and pertussis toxin. The data are consistent with a rapid metabolism of Ins(1,4,5)P3 to Ins(1,3,4)P3 via the Ins(1,4,5)P3 3-kinase pathway, followed by dephosphorylation by a 5-phosphomonoesterase. Indeed, a Ca2+-sensitive InsP3 3-kinase activity was demonstrated in tissue homogenate. Stimulation of protein kinase C and an organified form of iodine inhibit the Cchol-induced IPs generation. The negative feedback of activated protein kinase C could be exerted at the level of the receptor or of the receptor-G-protein interaction.
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PMID:Stimulation of generation of inositol phosphates by carbamoylcholine and its inhibition by phorbol esters and iodide in dog thyroid cells. 255 11

In human platelets, prostaglandin E1 and forskolin inhibit 5-hydroxytryptamine-induced phospholipase C, C-kinase and myosin light-chain kinase activity in a concentration-dependent way. Phospholipase C activation, however, was only partly inhibited, and this at higher concentrations than the protein kinases. Direct activation of the C kinase either by exogenous synthetic diacylglycerol or by 12-O-tetradecanoylphorbol 13-acetate was antagonized by prostaglandin E1 and forskolin. Since C-kinase activation is one of the key events in excitatory signal transduction in the platelets, we suggest that the inhibitory effect of agents that increase platelet cyclic AMP on platelet secretion and aggregation might reside in their capacity to antagonize C-kinase activity.
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PMID:Prostaglandin E1 and forskolin antagonize C-kinase activation in the human platelet. 282 2

The activity of phosphatidylinositol-specific phospholipase C was significantly reduced in platelets obtained from 20 euthymic manic-depressive patients on therapeutic lithium doses (mean blood level 0.85 mEq/l) compared to an age- and sex-matched group of 36 control subjects. The activities of prostaglandin E1-, aluminum/NaF-, and forskolin-stimulated platelet adenylate cyclase activity were also measured in a similar group of 16 lithium-treated and 22 control subjects. A marked reduction in both postreceptor (aluminum/NaF and forskolin) and receptor-stimulated (prostaglandin E1) platelet adenylate cyclase activity was observed in the lithium-treated group (mean blood level 0.81 mEq/l). These findings support the hypothesis that lithium's therapeutic mode of action in manic-depressive psychosis is mediated by the combined down-regulation of both principal second messenger systems, inositol phosphates and cyclic adenosine monophosphate, by reducing the activity of phosphatidylinositol-specific phospholipase C and adenylate cyclase.
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PMID:Lithium modulation of second messenger signal amplification in man: inhibition of phosphatidylinositol-specific phospholipase C and adenylate cyclase activity. 283 60


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