Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

We have investigated the characteristics of the receptor for ATP on neuronal cells and the involvement of phospholipase C and phospholipase D in the effector mechanisms, using PC12 rat phaeochromocytoma cells in culture. We show that the cells respond, with generation of total inositol phosphates, to ATP and adenosine 5'-O-(3-thiotriphosphate) (ATP gamma S) but not to 2-methylthioadenosine5'-triphosphate (2MeSATP), beta,gamma-methylene ATP, or adenosine 5'-O-(2-thiodiphosphate) (ADP beta S). The largest response to ATP gamma S was mainly independent of extracellular calcium, had an EC50 of 7.93 +/- 0.76 microM, and was competitively inhibited by the nonspecific antagonist suramin. The pyrimidine nucleotide UTP also elicited a response in these cells. Measurement of [3H]inositol triphosphate showed a rapid rise to maximum (10-15 sec) in response to both ATP gamma S and UTP but no response to 2MeSATP. Cells prelabeled with 32Pi and stimulated in the presence of 50 mM butanol responded to ATP gamma S, ATP, and UTP with enhanced formation of [32P]phosphatidylbutanol as well as [32P]phosphatidic acid, indicating that agonist-stimulated phosphatidic acid occurs by both phospholipase D and phospholipase C activity. The stimulation of phospholipase D was inhibited by the presence of a protein kinase C inhibitor, Ro 31-8220. The dose-response curve for the stimulation by ATP gamma S of phospholipase C was shifted to the right by the presence of UTP, indicating that both compounds act on the same receptors. The data provide the first evidence for the existence of a nucleotide receptor on neuronal cells (insensitive to both purines and pyrimidines) and show that this receptor is linked to both phospholipase C and phospholipase D.
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PMID:Neuronal "nucleotide" receptor linked to phospholipase C and phospholipase D? Stimulation of PC12 cells by ATP analogues and UTP. 154 77

The contribution of an omega-conotoxin GVIA (omega Cgtx)-sensitive Ca2+ influx pathway to the effects of angiotensin II (AII) receptor activation was examined in bovine adrenal medullary (BAM) cells. Pretreatment of BAM cells with 10(-6) M omega Cgtx blocked stimulation of exocytosis by the degradation-resistant analogue, sarcosine1-angiotensin II (S1-AII). In contrast, omega Cgtx had no effect on basal secretion, nor did it inhibit [3H]norepinephrine and [32P]ATP release in response to bradykinin, another phospholipase C-linked receptor agonist. Similarly, omega Cgtx pretreatment inhibited the stimulation of 45Ca2+ uptake by S1-AII, but did not affect the response to bradykinin. This selective inhibition did not appear to be due to blockade of AII receptors by omega Cgtx, as the accumulation of 3H-labeled inositol phosphates in response to S1-AII was not inhibited. The peak S1-AII-stimulated increase in the intracellular free Ca2+ concentration (Cai) in fura 2-loaded BAM cells also was not significantly reduced by omega Cgtx (or by stimulating in nominally Ca(2+)-free buffer), indicating that this response is dependent on intracellular Ca2+ pools. However, a small omega Cgtx-sensitive Cai response was detected after depletion of intracellular Ca2+ pools with ionomycin. This study shows that AII receptors, but not bradykinin receptors, are linked to an omega Cgtx-sensitive Ca2+ influx pathway in BAM cells.
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PMID:Angiotensin II receptors are coupled to omega-conotoxin-sensitive calcium influx in bovine adrenal medullary chromaffin cells. 154 65

In this study we used the bovine thoracic aorta endothelial cell line AG 4762 and primary bovine aortic endothelial cells to investigate the formation of phosphatidic acid (PA) in response to activation of P2-purinergic receptors. 2-Methylthio ATP (2MeSATP) stimulated the formation of [32P]-PA in bovine aortic endothelial cells labelled with 32P(i) for 2.5 hr. A comparison of the response to other ATP analogues suggests that this was mediated via a P2Y-purinergic receptor. Using various agonists at 30 microM there was a correlation between the formation of [32P]PA and of total inositol phosphates in the presence of lithium. The 2MeSATP-stimulated accumulation of [32P]PA showed an initial high rate, followed by a more sustained slower rate. The initial response was independent of extracellular calcium while the later response was dependent on calcium influx. The protein kinase C stimulator phorbol myristate acetate (PMA) produced only a very small enhancement of [32P]PA accumulation compared to 2MeSATP. The 2MeSATP stimulation of both inositol phosphates and [32P]PA was almost eliminated by the presence of PMA. Using cells prelabelled with [3H]methylcholine 2MeSATP produced only a small non-significant enhancement of [3H]choline formation; PMA by contrast formed a much larger amount of [3H]choline. There was no evidence of a change in [3H]phosphocholine. The dissociation between phospholipase D (PLD) activation and [32P]PA accumulation and the correlation between stimulation of [32P]PA accumulation and phospholipase C (PLC) activation all suggest that, using this protocol for labelling cells, the principle route of the stimulation of formation of [32P]PA is via the activation of PLC followed by metabolism of diacylglycerol (DAG) by DAG kinase. These results show that activation of P2Y-purinergic receptors on aortic endothelial cells leads to the formation of phosphatidic acid and that both PLD and PLC pathways are likely to contribute to this response.
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PMID:Stimulation of phosphatidic acid synthesis in bovine aortic endothelial cells in response to activation of P2-purinergic receptors. 156 76

The effect of exposure of porcine pulmonary artery endothelial cells to hypoxic (0% O2) and normoxic (20% O2) conditions for 24 and 48 h on phospholipid metabolism was studied. Sonicates prepared from endothelial cells that were exposed to 24 h of hypoxia showed significant increases in phospholipase A1 (91%), phospholipase C (75%), and diacylglycerol lipase (57%) activities. Hypoxic exposure of cells for 48 h caused an increase in diacylglycerol lipase activity (54%) only. Hypoxia also caused significant decreases in ATP levels and ATP-dependent arachidonyl coenzyme A (CoA) synthetase activity. Phospholipase A2, lysophosphatidylcholine acyltransferase, and diacylglycerol acyltransferase activities were not influenced by 24 or 48 h of hypoxia. When endothelial cells were prelabeled with [3H]arachidonic acid and then exposed to hypoxia, increased counts were recovered from the free fatty acid fraction of medium and from the cell fatty acid esters, lysophospholipids, diacylglycerols, and triacylglycerols. There was a concomitant decreased recovery of counts from cell phospholipids. These results indicate that hypoxic exposure of endothelial cells altered phospholipid metabolism by activating deacylation pathways and inhibiting reacylation via ATP-dependent arachidonyl CoA synthetase.
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PMID:Effect of hypoxia on phospholipid metabolism in porcine pulmonary artery endothelial cells. 159 Apr 10

We have studied the influence of phospholipase C treatment of intact purified chloroplast on the translocation of a plastid destined precursor protein. Under standard import conditions, i.e. in the light in the presence of 2 mM ATP translocation was completely abolished but binding was observed at slightly elevated levels. An experimental regime which allowed binding but not import of the precursor protein, i.e. in the dark in the presence of 10 microM ATP, demonstrated that translocation intermediates, normally detected at this stage, were missing in phospholipase treated chloroplasts. The precursor was completely sensitive to protease treatment, indicating that the transfer of the precursor from the receptor to the import apparatus was blocked by phospholipase treatment.
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PMID:Transfer of a chloroplast-bound precursor protein into the translocation apparatus is impaired after phospholipase C treatment. 162 46

The combined action of phosphatidylcholine preferring phospholipase C (PC-PLC) and intracellular lipases has recently been shown to cause glycerol output in energy deprived rat cardiomyocytes. In the present study we examined the effect of hypothermia and rewarming on PC-PLC evoked glycerol output in freshly isolated, calcium-tolerant myocytes. The cells were preincubated for 60 min at hypothermic (5 degrees C) or normothermic (37 degrees C) conditions in Krebs-Henseleit bicarbonate buffer (pH 7.4) supplemented with 1 mM DL-carnitine, 1% B.S.A. and 5 mM glucose. Addition of PC-PLC resulted in a significantly higher (P less than 0.05) output of glycerol in myocytes undergoing rewarming than in myocytes kept constantly at 5 degrees C or 37 degrees C. The values obtained for PC-PLC induced glycerol output (difference in glycerol output between incubations with and without PC-PLC) were 6.77 +/- 2.6 (37 degrees C), 4.54 +/- 1.7 (5 degrees C) and 22.85 +/- 5.9 (5-37 degrees C) nmol/10(6) cells.h. Rewarming in addition caused a significantly higher (P less than 0.05) leakage of lactate dehydrogenase (LDH) from the rewarmed cells as compared to cells at constant temperatures (5 degrees C or 37 degrees C). However, there was no additional effect of PC-PLC on LDH leakage. The elevated PC-PLC induced glycerol output in rewarmed myocytes was not related to a fall in the percentage of rod-shaped cells or a reduced cellular content of ATP, since no differences could be detected between the various myocyte preparations with respect to these parameters.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of hypothermia and rewarming on phospholipase C-evoked glycerol output in rat myocardial cells. 163 71

The effects of phorbol 12-myristate 13-acetate (TPA) or ATP on phosphatidylcholine (PC) hydrolysis were investigated in cultured type II pneumocytes prelabeled with [3H]choline or 1-O-[3H]octadecyl-sn-glycero-3-phosphocholine ([3H]lyso-PAF). In cells prelabeled with [3H]choline, TPA or ATP stimulated an increase in [3H]choline, [3H]phosphocholine, and [3H]glycerophosphocholine. The formation of these choline metabolites was associated with a concomitant loss of [3H]PC but not from disaturated PC or phosphatidylinositol. In cells prelabeled with [3H]lyso-PAF, the formation of [3H]phosphatidic acid (PA) and then [3H]1,2-DG was stimulated by TPA or ATP and was associated with a loss of 3H from PC but not from disaturated PC or phosphatidylinositol. There was a concentration-dependent formation of [3H]1,2-DG and [3H]PA in response to ATP. Downregulation of protein kinase C with TPA abolished the stimulation of PC hydrolysis. In addition to the generation of metabolites indicative of phospholipase C and/or D activity, [3H]lyso-PC, a product of phospholipase A2, was also generated in response to TPA. These findings suggest an important role for PC breakdown in signal transduction in type II pneumocytes.
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PMID:Stimulation of phosphatidylcholine hydrolysis in type II alveolar epithelial cells. 163 29

Perturbation of the T-cell receptor (TCR) complex is followed by the rapid hydrolysis of inositol phospholipids (InsPL) by phospholipase C (PLC), producing diacylglycerol and inositol phosphates, which act as second messengers in signal transduction. The mechanism coupling the TCR to InsPL hydrolysis is not clearly defined, and no information is available on this mechanism in the CD4+ helper subset of T-lymphocytes (Th). We have tested the hypothesis that guanine-nucleotide-binding proteins (G-proteins) may couple the TCR to PLC in a murine Th type II (Th2) cell clone. Cell permeabilization with streptolysin O (SLO) or tetanolysin (TL) was used to allow membrane-impermeable nucleotides access to intracellular sites of action. Exposure of permeabilized Th2 cells to guanosine 5'-[gamma-thio]triphosphate (GTP gamma S), a non-hydrolysable GTP analogue, resulted in a 2.1-2.5-fold increase in inositol phosphate generation. Similarly, perturbation of the TCR with the monoclonal antibody 145.2C11 (directed against the epsilon-chain of the CD3 component of the TCR) resulted in a 3.1-4.2-fold increase in InsPL hydrolysis by permeabilized cells. Both lysins were similarly effective in allowing GTP gamma S induction of InsPL hydrolysis, but TL-permeabilized cells responded better to TCR perturbation than SLO-treated cells. A role for G-proteins in TCR coupling to PLC was further supported by the inhibition of TCR-induced InsPL hydrolysis by guanosine 5'-[beta-thio]diphosphate (GDP beta S), a guanine nucleotide analogue that inhibits G-protein function. ATP was required for TCR-mediated InsPL hydrolysis, and potentiated GTP gamma S-induced hydrolysis. Other nucleotides (i.e. CTP, GDP, GTP, ITP) did not affect the response. These data indicate that G-proteins may contribute to the regulation of PLC activation in Th2 cells, coupling it to the TCR.
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PMID:A role for guanine-nucleotide-binding proteins in mediating T-cell-receptor coupling to inositol phospholipid hydrolysis in a murine T-helper (type II) lymphocyte clone. 164 19

Extracellular ATP (10(-3) M) stimulated [3H]phosphatidylcholine secretion approximately 3.4-fold in rat type II pneumocytes prelabeled overnight with [3H]choline. The same concentration of ATP caused a rapid increase in [3H]inositol trisphosphate (IP3) and a decrease in [3H]phosphatidylinositol bisphosphate (PIP2) in [3H]inositol-prelabeled cells. ATP also caused a biphasic increase in 1,2-[3H]diacylglycerol in cells prelabeled with [3H]arachidonic acid: a rapid increase that peaked at 10 s followed by a larger increase that peaked at 5-10 min. The first peak in diacylglycerol and the increase in IP3 are consistent with phospholipase C action on PIP2 and generation of second messengers that promote mobilization of intracellular Ca2+ and activation of protein kinase C. However, at the level of phosphatidylcholine secretion the stimulatory effects of ATP and of direct activators of protein kinase C, 12-O-tetradecanoylphorbol-13-acetate (TPA) and 1,2-dioctanoyl-sn-glycerol, were at least additive, suggesting that activation of protein kinase C may not be the major signal transduction mechanism in ATP action or alternatively that ATP activates a different isoform of protein kinase C. Pretreatment of type II cells with TPA for 30 min led to a subsequent 40% diminution in the stimulatory effects of ATP on both phosphatidylcholine secretion and IP3 generation.
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PMID:ATP-stimulated inositol phospholipid metabolism and surfactant secretion in rat type II pneumocytes. 164 84

The activity of a phospholipase C which hydrolyses exogenous phosphatidylinositol-4,5-bisphosphate [( 3H]PtdIns(4,5)P2) in membranes prepared from frozen postmortem human brain and rat brain was investigated. Enzyme characteristics were essentially similar in membranes prepared from frozen postmortem brain and fresh or frozen rat brain. The [3H]PtdIns(4,5)P2 solubilization and assay procedure employed resulted in an efficient availability of the substrate for the enzyme. The non-hydrolysable guanosine triphosphate analogue guanosine 5'-[beta gamma-imido]diphosphate (Gpp[NH]p) stimulated hydrolysis rapidly with a half maximum activity of approximately 25 microM. This stimulation was not specific for guanine nucleotides as ATP, imidodiphosphate and pyrophosphate also caused enzyme activation. However these activation effects could be distinguished by the polyanion spermine. The non-hydrolysable guanine dinucleotide analogue guanosine 5'-[beta-thio]diphosphate acted as a partial agonist thereby inhibiting the stimulatory effect of Gpp[NH]p. Gpp[NH]p-stimulated enzyme activity showed a maximum response in the presence of 1 mM deoxycholate and displayed a pH optima in the range 7.0-7.5. PtdIns(4,5)P2 hydrolysis was observed in the absence of added calcium, but hydrolytic cleavage was inhibited in the presence of divalent ion chelators. Magnesium inhibited PtdIns(4,5)P2 hydrolysis in a concentration-dependent manner. Elucidation of these aspects of the phosphatidylinositol cycle in normal human postmortem brain will permit comparative studies in CNS disease states.
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PMID:Assay of a phosphatidylinositol bisphosphate phospholipase C activity in postmortem human brain. 164 35


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