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 hydrolysis of phosphatidylinositol-4,5-bisphosphate (PIP2) by rat sciatic nerve cytosolic phosphoinositidase C [phosphoinositide-specific phospholipase C (PIC)] was studied at neutral pH and at ionic concentrations that approximate intracellular conditions. The principal water-soluble product formed was shown to be inositol trisphosphate by anion exchange chromatography. The maximum hydrolysis rate (2.5 nmol/min/mg protein) was achieved at less than 100 nM Ca2+. Hydrolysis was markedly increased to 15 nmol/min/mg protein by inclusion of K+ in the reaction mixture. In the presence of 200 mM K+, the optimum Ca2+ was increased to approximately 600 nM. Higher Ca2+ concentrations progressively inhibited PIP2 hydrolysis. Mg2+ also inhibited the reaction, but the presence of equimolar amounts of ATP and Mg2+ had no effect. Appreciable degradation of phosphatidylinositol-4-phosphate (PIP) also occurred in the nanomolar Ca2+ range, whereas breakdown of phosphatidylinositol (PI) required millimolar Ca2+. The presence of PIP but not PI inhibited PIP2 hydrolysis. Upon subcellular fractionation of nerve, more than 50% of recovered PIC activity was in the cytosol and about 20% was located in a myelin-enriched fraction. Using PIP2 as substrate, PIC activities in nerves from normal and streptozotocin-induced diabetic animals were not different. However, the myelin-associated enzyme from diabetic animals was more labile to freezing and thawing.
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PMID:Activity and distribution of phosphoinositidase C in rat sciatic nerve. 133 36

Although the translocation of protein kinase C and phospholipase A2 are well documented, no information is available about the possible down-modulation of transmembrane phospholipase C. We found that TPA induced a dose-dependent (10-200 nM) and time-dependent (15 min-6 h) down-modulation of transmembrane phosphoinositidase C (PLC-PI) on lymphoid cells (CEM-CM3 and WIL2-NS) and epitheloid carcinoma cells (HeLa S3) but not on human fibroblasts (MRC-5). Cell-surface expression of PLC-PI on intact cells was assayed by flow cytometry using saturating concentrations of polyclonal anti-PLC-PI antibodies and phycoerythrin-conjugate. A control phorbol-ester which does not activate protein kinase C (PKC) had no internalization effect on PLC-PI. PKC inhibitors staurosporine (2.5 nM) and H-7 (10 microM) partially inhibited the TPA effect. Cytochalasin B (40 micrograms/ml) did not modify the TPA-induced PLC-PI down-modulation. The effect of TPA on PLC-PI seems quite specific since no internalization was induced by TPA on transmembrane phosphatidylcholine-preferring PLC expression. These results show that TPA can translocate the membrane-bound PLC-PI, probably by PKC activation.
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PMID:Topological regulation of cell-membrane phosphoinositidase C. 165 Jan 98

A monospecific inhibitory antibody directed to phospholipase C (phosphoinositidase C) blocked the antiviral effect of human interferons alpha and beta when tested on human quiescent fibroblasts challenged with the vesicular stomatitis virus. This action was due to specific inhibition of polyphosphoinositide hydrolysis because (a) the F(ab')2 fragment of the antibody molecule was also inhibitory; (b) excess antibodies directed to phospholipase A2 and to a phosphatidylcholine-preferring phospholipase C did not have any inhibitory effect, and (c) the combination of 12-O-tetradecanoyl-phorbol-acetate and calcium ionophore A23187 had an interferon-like antiviral effect which was not influenced by the inhibitory anti-phospholipase C antibodies. To avoid an interferon-like effect due to induction of interferon by second messengers, Vero cells, which lack interferon biosynthesis, were also used. Liposomes containing inositol 1,4,5-triphosphate and 1-oleoyl-2-acetyl-rac-glycerol protected Vero cells against the infection with the vesicular stomatitis virus. These results taken together show that phosphoinositide-derived second messengers are involved in triggering the antiviral effect of interferons alpha and beta.
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PMID:Cell-membrane phospholipase C is involved in inducing the antiviral effect of interferon. 250 82

The ability of alcohols to regulate inositol lipid-specific phospholipase C (phosphoinositidase C) was examined in turkey erythrocyte ghosts prepared by cell lysis of erythrocytes which were prelabeled with [3H] inositol. Guanosine 5'-[gamma-thiotriphosphate] GTP[S] stimulated the production of both [3H]inositol bisphosphate (18-fold) and [3H]inositol trisphosphate (6-fold) in this system. The accumulation of [3H]inositol bisphosphate and [3H]inositol trisphosphate was linear up to 8 min following an initial lag period of 1-2 min. Ethanol (300 mM) reduced the lag period for [3H]inositol phosphate accumulation at submaximal GTP[S] concentrations and caused a shift to the left (3-fold) in the dose-response curve. Other short chain alcohols, methanol (300 mM), 1-propanol (200 mM), and 1-butanol (50 mM) also enhanced the accumulation of [3H] inositol phosphates in the presence of submaximal GTP[S] concentrations. Receptor activation by the purinergic agonist adenosine 5'-[beta-thio]disphosphate (ADP[S]) (10 microM) also reduced the lag period for [3H] inositol phosphate formation and shifted the GTP[S] dose response to the left (10-fold). In addition, ADP[S] increased the response to maximal GTP[S] concentrations. The formation of [3H]inositol phosphates induced by GTP[S] was associated with a concomitant decrease in labeling of both [3H]phosphatidylinositol monophosphate and [3H]phosphatidylinositol bisphosphate, but no decrease in [3H]phosphatidylinositol was observed. All of the alcohols tested enhanced the breakdown of [3H]polyphosphoinositides in the presence of GTP[S]. The dose response to guanosine 5'-[beta gamma-imino]triphosphate for [3H]inositol phosphate formation was displaced to the left by ethanol (300 mM) and ADP[S] (10 microM) (2- and 7-fold), respectively. ADP[S] also enhanced the maximal response to guanosine 5'-[beta gamma-imino]triphosphate. The [3H]inositol phosphate formation produced in response to NaF was unaffected by either ethanol or receptor activation. These results indicate that alcohols initiate an activation of phosphoinositidase C, mediated at the level of the regulatory guanine nucleotide-binding protein.
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PMID:Short chain alcohols activate guanine nucleotide-dependent phosphoinositidase C in turkey erythrocyte membranes. 254 Jan 62

Using the technique of HPLC with Partisil SAX columns, we have found that stimulation of amoebae of Dictyostelium discoideum with the chemoattractant cyclic AMP induces the rapid accumulation of inositol 1,4,5-trisphosphate (Ins(1,4,5)P3), with a peak at 5 s. A smaller HPLC peak (designated P3) that elutes just after the Ins(1,4,5)P3 peak accumulates more slowly to a maximum at 20 s. In control studies, the changes in Ins(1,4,5)P3 were shown not to be due to varying recovery from the cell extracts and a comparison of reverse-phase and Partisil SAX HPLC columns showed similar values for determinations by either method. The involvement of a G-protein in this chemotactic system was confirmed by the finding that accumulation of Ins(1,4,5)P3 was elicited by the addition of GTP gamma S (5'-[gamma-thio]triphosphate) to saponin-permeabilized amoebae. A study of the changes in the lipid-soluble phosphatidyl inositol phosphates demonstrated that cyclic AMP also stimulated a rapid loss of radioactivity from 32P-labelled phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2), which corresponded in its timing to the rise in Ins(1,4,5)P3, indicating that a phosphoinositidase C (phospholipase C) is present that can be stimulated by occupation of the cell surface cyclic AMP receptors.
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PMID:Inositol tris- and polyphosphate formation during chemotaxis of Dictyostelium. 255 21

Using human spermatozoa stimulated with either progesterone or the Ca2+ ionophore A23187 to undergo acrosomal exocytosis, we have investigated potential pathways for generation of diacylglycerol (DAG) and have examined the possibility that DAG plays an important role in the exocytotic response. Both treatments resulted in rapid and considerable generation of DAG, followed by a limited rise in phosphatidic acid (PA). Further experiments indicated that phospholipase C (PLC) activity is important in this generation of DAG, but phospholipase D activity probably is not. In addition, polyphosphoinositide-specific phosphoinositidase C activation and hydrolysis, of phosphatidylinositol 4,5-bisphosphate appears to be a necessary prerequisite for activation of the PLC pathway. Finally the DAG formed appears to be important in acrosomal exocytosis: (i) blocking DAG metabolism with a DAG kinase inhibitor resulted in both increased endogenous levels of DAG and a significantly increased exocytotic response in stimulated cells and (ii) exogenous DAG induced exocytosis in capacitated spermatozoa whereas PA did not. Taken together, these results suggest that DAG plays a key role in events leading to membrane fusion during human sperm acrosomal exocytosis stimulated by natural agonists.
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PMID:A role for diacylglycerol in human sperm acrosomal exocytosis. 923 98

Our previous studies have shown that both increase in Ca2+ levels and activation of protein kinase C (PKC) are required for monocyte-mediated O2- production and low density lipoprotein (LDL) peroxidation. Phosphoinositide-specific phospholipase C (phosphoinositidase C or PIC) is believed to mediate release of intracellular Ca2+ through InsP3 formation and activation of PKC through diacylglycerol (DAG). In these studies, we investigated the PIC pathway for its participation in monocytic cell-mediated lipid peroxidation of LDL. We found substantial InsP3 formation in opsonized zymosan (ZOP)-activated U937-b cells, indicating the activation of PIC. Both inhibition of PIC by the PIC inhibitor U-73122 and reduction of the supply of the precursor lipid by lithium chloride suppressed InsP3 formation but did not alter LDL lipid peroxidation nor O2- production by activated cells. Furthermore, we also found that suppression of PIC activity had no substantial inhibitory effect on PKC activity in ZOP-activated human monocytes. Our data suggest that PIC activity is induced upon cell activation resulting in increased levels of InsP3. The activity of this pathway, however, is not required for cell-mediated O2- production, PKC activation or LDL oxidation.
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PMID:Activation of PKC, superoxide anion production and LDL lipid peroxidation are not dependent on phosphoinositide-specific phospholipase C activity in U937 cells. 952 26

Spermatozoa undergo exocytosis in response to agonists that induce Ca2+ influx and, in turn, activation of phosphoinositidase C, phospholipase C, phospholipase A2, and cAMP formation. Since the role of cAMP downstream of Ca2+ influx is unknown, this study investigated whether cAMP modulates phospholipase C or phospholipase A2 using a ram sperm model stimulated with A23187 and Ca2+. Exposure to dibutyryl-cAMP, phosphodiesterase inhibitors or forskolin resulted in enhancement of exocytosis. However, the effect was not due to stimulation of phospholipase C or phospholipase A2: in spermatozoa prelabelled with [3H]palmitic acid or [14C]arachidonic acid, these reagents did not enhance [3H]diacylglycerol formation or [14C]arachidonic acid release. Spermatozoa were treated with the phospholipase A2 inhibitor aristolochic acid, and dibutyryl-cAMP to test whether cAMP acts downstream of phospholipase A2. Under these conditions, exocytosis did not occur in response to A23187 and Ca2+. However, inclusion of dibutyryl-cAMP and the phospholipase A2 metabolite lysophosphatidylcholine did result in exocytosis (at an extent similar to that seen when cells were treated with A23187/Ca2+ and without the inhibitor). Inclusion of lysophosphatidylcholine alone, without dibutyryl-cAMP, enhanced exocytosis to a lesser extent, demonstrating that cAMP requires a phospholipase A2 metabolite to stimulate the final stages of exocytosis. These results indicate that cAMP may act downstream of phospholipase A2, exerting a regulatory role in the exocytosis triggered by physiological agonists.
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PMID:Stimulation of Ca(2+)-dependent exocytosis of the sperm acrosome by cAMP acting downstream of phospholipase A2. 1079 26

During the past half century, we have progressed from simply viewing myo -inositol-containing glycerophospholipids as quantitatively minor membrane constituents to the present, very striking, situation in which more and more important cellular functions are being assigned to a plethora of phosphorylated derivatives of inositol and phosphatidylinositol. Two such examples are discussed briefly: the activation by environmental stresses of the single phosphoinositidase C of yeast, which is related to the phospholipase C delta s of other eukaryotes, and the involvement of PtdIns(3,5) P (2) in endomembrane trafficking.
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PMID:Morton Medal Lecture. New insights into the roles of phosphoinositides and inositol polyphosphates in yeast. 1254 44