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)

The mechanism by which cAMP modulates the activity of phosphoinositide-specific phospholipase C (PLC) was studied. Elevation of cAMP inhibited both basal and norepinephrine-stimulated phosphoinositide breakdown in C6Bu1 cells which contain at least three PLC isozymes, PLC-beta, PLC-gamma, and PLC-delta. Treatment of C6Bu1 cells with cAMP-elevating agents (cholera toxin, isobutylmethylxanthine, forskolin, and 8-bromo-cAMP) increased serine phosphate in PLC-gamma, but the phosphate contents in PLC-beta and PLC-delta were not changed. In addition, cAMP-dependent protein kinase selectively phosphorylated purified PLC-gamma among the three isozymes and added a single phosphate at serine. The serine phosphorylation, nevertheless, did not affect the activity of PLC-gamma in vitro. We propose, therefore, that the phosphorylation of PLC-gamma by cAMP-dependent protein kinase alters its interaction with putative modulatory proteins and leads to its inhibition.
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PMID:Phosphorylation of phospholipase C-gamma by cAMP-dependent protein kinase. 247 46

We have characterized a plasma membrane phosphatidylinositol 4,5-bisphosphate (PIP2)-specific phospholipase C (PLC) and a cytosolic phosphatidylinositol (PI)-specific PLC in human liver. Epinephrine, 1 x 10(-5) M, and vasopressin, 1 x 10(-8) M, stimulated PIP2-PLC which was enhanced by guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S). PI-PLC stimulation was not observed by these agents. Insulin and insulin-like growth factors (IGF-I and IGF-II) in the presence and absence of GTP gamma S did not stimulate PIP2-PLC or PI-PLC in plasma membranes and cytosol preparations nor phosphoinositide breakdown in isolated human hepatocytes. Furthermore, serendipitly we found that PIP2-PLC activity was increased in liver membranes from obese patients with type II diabetes when compared to obese and lean controls. We conclude that in human liver, insulin and IGFs are not members of the family of hormones generating inositol trisphosphate (IP3) as a second messenger. Furthermore, the increased PIP2-PLC in diabetic liver may result in: (a) increased intracellular concentrations of IP3 and thus increased Ca2+, which has been postulated to induce insulin resistance; and (b) increased diacylglycerol and thus increased protein kinase C which phosphorylates the insulin receptor at serine residues inactivating the insulin receptor kinase. While the mechanism of increased PIP2-PLC activity in diabetes is unknown, it may initiate a cascade of events that result in insulin resistance.
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PMID:Effect of insulin and insulin-like growth factors I and II on phosphatidylinositol and phosphatidylinositol 4,5-bisphosphate breakdown in liver from humans with and without type II diabetes. 254 Jan 78

A BAL17 B lymphoma cell line bearing mu and delta chains on its surface behaves in a similar manner to normal mature B cells in terms of initial biochemical transmembrane signalling [Mizuguchi, Beaven, Ohara & Paul (1986) J. Immunol. 137, 2162-2167; Mizuguchi, Yong-Yong, Nakabayashi, Huang, Beaven, Chused & Paul (1987) J. Immunol. 139, 1054-1059]. Therefore the effects of protease inhibitors on increases in inositol phospholipid metabolism and intracellular free calcium concentration ([Ca2+]i) were examined. We show that the serine protease inhibitors Tos-Phe-CH2Cl (1-chloro-4-phenyl-3-L-tosylamidobutan-2-one-, TPCK) and Tos-Lys-CH2Cl (7-amino-1-chloro-3-L-tosylamidoheptan-2-one; TLCK) inhibit anti-IgM-mediated accumulation of inositol phosphates in a dose-dependent manner. InsP3 production induced by anti-IgM is also inhibited by pretreatment with Tos-Lys-CH2Cl or Tos-Phe-CH2Cl. Tos-Lys-CH2Cl- Tos-Phe-CH2Cl-mediated inhibition is not overcome by high concentrations of anti-IgM. Moreover, anti-IgM-mediated increases in [Ca2+]i are inhibited by pretreatment of the cells with these inhibitors. However, increases in inositol phospholipid metabolism caused by NaF, an activator of guanine-nucleotide-binding proteins (G-proteins), are approx. 10-fold more resistant to Tos-Lys-CH2Cl and Tos-Phe-CH2Cl inhibition compared with anti-IgM-induced changes. Furthermore, NaF-induced increases in [Ca2+]i are not inhibited by Tos-Lys-CH2Cl or Tos-Phe-CH2Cl pretreatment, suggesting that the inhibitors act at a step proximal to phospholipase C activation. The Tos-Lys-CH2Cl or Tos-Phe-CH2Cl treatment does not change the membrane IgM density as measured by flow cytometry, indicating that the active site of the inhibitors is distal to the membrane IgM molecule. These results indicate that serine proteases may be involved in coupling the receptor cross-linkage to G-protein.
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PMID:Differential sensitivity of anti-IgM-induced and NaF-induced inositol phospholipid metabolism to serine protease inhibitors in BAL17 B lymphoma cells. 255 5

The phosphorylation of the lipocortin-related protein, p68, found in Ca2+-dependent association with the submembranous cytoskeleton has been studied using isolated human placental syncytiotrophoblast plasma membrane vesicles. p68 undergoes rapid, cation-independent phosphorylation in unstimulated membrane vesicles which was inhibited, in a dose-dependent manner, by insulin, platelet-derived growth factor, macrophage colony stimulating factor, protein kinase C-activating phorbol esters and phosphatidylinositol-specific phospholipase C. Epidermal growth factor had no effect on overall p68 phosphorylation. Transferrin induced an increase in p68 phosphorylation. However, phosphotyrosine was detected in p68 after treatment with epidermal growth factor, macrophage colony stimulating factor or transferrin, whereas a reduction in p68 phosphorylation appeared to be restricted to serine. cAMP and both cholera and pertussis toxins inhibited p68 phosphorylation. Both toxins were synergistic with the effects of insulin and platelet-derived growth factor whilst being antagonistic to the effect of transferrin. Epidermal growth factor and both human and equine immunoglobulin G, all of which alone did not affect overall p68 phosphorylation, reduced cholera or pertussis toxin-induced inhibition of p68 phosphorylation. Several phosphatase inhibitors failed to prevent macrophage colony stimulating factor-induced reduction of p68 phosphorylation. These results indicate that (i) p68 is a potential substrate of receptor tyrosyl kinases, (ii) p68 is not phosphorylated by protein kinase C or cAMP-dependent kinase and (iii) p68 phosphorylation is inhibited by activation of multiple pathways including those employing diacylglycerol or cAMP as second messengers.
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PMID:The phosphorylation of p68, a calcium-binding protein associated with the human syncytiotrophoblast submembranous cytoskeleton, is modulated by growth factors, activators of protein kinase C and cyclic AMP. 255 24

In a number of cell lines, epidermal growth factor (EGF) rapidly stimulates the breakdown of inositol phospholipids. Phosphatidylinositol-specific phospholipase C (PLC), therefore, plays an important role in this biological response to EGF, but the mechanism by which EGF-receptor complexes modulate the activation of PLC is not understood. We have previously suggested that tyrosine phosphorylation of PLC or an unknown PLC-associated protein by the EGF receptor is involved in the activation process (Wahl, M. I., Daniel, T. O., and Carpenter, G. (1988) Science 241, 968-970) and have recently shown by immunoprecipitation that the addition of EGF to 32P-labeled cells increases tyrosine and serine phosphorylation of PLC-II (Wahl, M. I., Nishibe, S., Suh, P.-G., Rhee, S. G., and Carpenter, G. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 1568-1572). In this communication we demonstrate that PLC-II (Mr = 145,000) purified from bovine brain can be phosphorylated in vitro in an EGF-dependent manner by the tyrosine kinase activity of the purified EGF receptor. While PLC-II is an efficient phosphorylation substrate for the purified EGF receptor, PLC-I is a poor substrate and PLC-III is not phosphorylated to any detectable extent. Though all three PLC isozymes possess typical tyrosine phosphorylation sequences, the EGF receptor is surprisingly selective in vitro for the phosphorylation of PLC-II. High performance liquid chromatography comparison of tryptic phosphotyrosyl peptides from PLC-II phosphorylated in vivo and in vitro indicated a similar pattern of multiple tyrosine phosphorylation sites. These findings show that the EGF receptor can directly phosphorylate PLC-II in an efficient and selective manner.
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PMID:Tyrosine phosphorylation of phospholipase C-II in vitro by the epidermal growth factor receptor. 273 23

We report that a 100 residue segment in the carboxy-terminus half of phosphatidylinositol-specific phospholipase C is similar to a segment in the amino-terminus half of protein kinase C. The computer-based comparison score is 9.5 standard deviations higher than that of 2500 comparisons of randomized sequences of these segments (P = 10(-21), suggesting that the two segments have similar biological properties. Phospholipase C has a segment that is homologous to part of the non-catalytic domain of src kinase and other tyrosine protein kinases. The similarity of phospholipase C with protein kinase C, a serine/threonine kinase suggests that novel exon shuffling occurred among serine/threonine and tyrosine kinases and phospholipase C.
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PMID:Similarity between phospholipase C and the regulatory domain of protein kinase C. 274 13

Isolation of two membrane-bound alkaline phosphatase (AP) species from avian growth plate cartilage matrix vesicle (MV) fractions is described. AP was first released from the membranes by phosphatidylinositol-specific phospholipase C (PIase C), followed by chromatography on DEAE-Bio-Gel A and Reactive-Red agarose. Two AP species having apparent Mr of 81.5 and 77 kDa by SDS-PAGE were purified in high yield and specific activity by this simple method. Treatment with neuraminidase to remove sialic acid residues reduced their size slightly, but did not diminish the difference in Mr between the two species. Digestion with N-glycanase, however, decreased both AP species to a common size of 59 kDa. This reveals that both enzymes are highly glycosylated and suggests that the two forms may result from differences in degree of glycation. The amino acid compositions of the two avian enzyme forms are very similar, but are markedly enriched in serine, glycine and glutamate when compared to those reported for mammalian liver-kidney-bone AP. Possible differences in amino acid sequence between the two avian forms have not been excluded. The cross-reactivity of polyclonal antibodies to these enzymes with bovine kidney, but not intestinal AP, indicate that the avian cartilage APs are of the liver-kidney-bone isozyme type.
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PMID:Isolation of two glycosylated forms of membrane-bound alkaline phosphatase from avian growth plate cartilage matrix vesicle-enriched microsomes. 280 49

In lymphocytes, the Na+/H+ antiport can be stimulated by 12-O-tetradecanoylphorbol 13-acetate (TPA) and by osmotic shrinking. Since TPA acts by stimulating protein kinase C, we undertook experiments to determine if protein phosphorylation also underlies the osmotic stimulation of the antiport. We found that at least one of the membrane polypeptides labeled in cells treated with TPA is also phosphorylated by hypertonic shrinking. In both instances phosphorylation is alkali labile and associated with serine and threonine residues. We tested the possibility that shrinking activates phospholipase C, thereby stimulating protein kinase C through release of diacylglycerol. No decrease in phosphatidylinositol 4,5-bisphosphate levels was detected in hypertonically treated cells. Moreover, the concentrations of inositol phosphates, including inositol trisphosphate, were not altered in shrunken cells. Thus, shrinking does not appear to activate phospholipase C. Whereas TPA induced intracellular redistribution of soluble protein kinase C, no such effect was detected in osmotically activated cells. It was concluded that osmotic stimulation of the Na+/H+ antiport is associated with activation of protein phosphorylation by a kinase that is similar, but not identical to protein kinase C. Experiments in Na+-free or amiloride-containing media indicate that phosphorylation is not a consequence of activation of the antiport.
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PMID:Protein phosphorylation during activation of Na+/H+ exchange by phorbol esters and by osmotic shrinking. Possible relation to cell pH and volume regulation. 301 4

The serine protease inhibitors diethyl p-nitrophenyl phosphate and phenylmethylsulfonyl fluoride (chemical modifiers of serine residue) and N-acetyl-l-tryptophan ethyl ester (competitive inhibitor of chymotryptic protease) inhibited 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (AGEPC; platelet-activating factor)-induced platelet aggregation and secretion. The inhibition was dependent on the preincubation time with the serine protease inhibitor and on the concentration of AGEPC and inhibitor. The IC50 value of diethyl-p-nitrophenyl phosphate, phenylmethylsulfonyl fluoride, and N-acetyl-l-tryptophan ethyl ester towards 5 X 10(-10) M AGEPC in serotonin release was 2.2 X 10(-4), 8.0 X 10(-4), and 5.0 X 10(-4) M, respectively. In experiments where platelets were incubated with these inhibitors and then washed with buffer, the inhibition of AGEPC stimulation was not observed. Prostaglandin H2 analog U46619 (10(-6) to 10(-5) M)- and thrombin (0.1 unit/ml)-induced platelet activation were also blocked by 1 mM diethyl p-nitrophenyl phosphate and 1 mM N-acetyl-l-tryptophan ethyl ester. The binding of AGEPC (1.5 X 10(-11) to 9.4 X 10(-10) M) to platelets and the platelet cyclic AMP level were not affected by diethyl p-nitrophenyl phosphate, phenylmethylsulfonyl fluoride, and N-acetyl-l-tryptophan ethyl ester. However, 1 mM diethyl p-nitrophenyl phosphate and 1 mM N-acetyl-l-tryptophan ethyl ester suppressed 10(-9) M AGEPC-induced breakdown of phosphatidylinositol 4,5-bisphosphate and formation of phosphatidic acid to 10-12 and 39-42%, 40-kDa protein phosphorylation to 4 and 30%, and arachidonic acid release to 17 and 28% of controls, respectively. On the other hand, 5 mM diethyl p-nitrophenyl phosphate did not inhibit diacylglycerol production and arachidonic acid release initiated by 2.5 mM deoxycholate treatment, suggesting that receptor-mediated phospholipase C and phospholipase A2 activation were inhibited by the serine protease inhibitor, but the deoxycholate (physicochemical stimulant)-initiated activation was not. AGEPC-induced 20-kDa protein phosphorylation and the inhibitory action of AGEPC on cyclic AMP accumulation were abolished in the presence of diethyl p-nitrophenyl phosphate and phenylmethylsulfonyl fluoride. However, a tryptic protease inhibitor, 1 mM p-aminobenzamidine and 1 mM benzoyl-l-arginine methyl ester, did not prevent the AGEPC-induced platelet secretion.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Platelet-activating factor stimulation of rabbit platelets is blocked by serine protease inhibitor (chymotryptic protease inhibitor). 310 43

To examine the role of endogenous arachidonic acid (AA) as the possible second messenger signal in interferon-gamma (IFN-gamma) production, helper cell-depleted mouse spleen cell cultures were treated with the enzyme phospholipase A2 (PLA2). Treatment with PLA2 from several different animal sources at concentrations between 10 and 300 U/ml resulted in complete, dose-dependent restoration of competence for IFN-gamma production. By comparison, phospholipase C (PLC) from several different species failed to restore competence at concentrations between 0.3 and 30 U/ml; the inability of PLC to provide the helper signal for induction of IFN-gamma was not due to cytotoxicity. Since PLA2 provides competence for IFN-gamma production by sn-2 hydrolysis, it was of interest to identify eicosanoids and other lipids released from [3H]-AA labeled cells by PLA2 and PLC. Treatment of spleen cells with PLA2, but not PLC, resulted in the appreciable release of AA only. Sufficient AA was released from spleen cells for restoration of competence for production of IFN-gamma. All glycerol-derived cell membrane phospholipids examined (phosphatidylethanolamine, -inositol, -choline, and -serine) incorporated labeled AA which was releasable by treatment with PLA2. The data support and extend previous studies which suggested that AA plays a pivotal role in mediation of the interleukin 2 helper signal for IFN-gamma production.
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PMID:Phospholipase A2 treatment of lymphocytes provides helper signal for interferon-gamma induction. Evidence for second messenger role of endogenous arachidonic acid. 311 9


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