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 studied the relationship between phosphoinositide hydrolysis, phosphatidylcholine hydrolysis, and sn-1,2-diacylglycerol (DAG) formation in response to carbachol stimulation in rat parotid acinar cells. Previously, we demonstrated that DAG formation stimulated with 1 microM carbachol was biphasic: the first peak occurred at 5 min and the second one at 20 min. It was also demonstrated that the second peak was regulated in part by a calmodulin/protein kinase C-dependent mechanism. Based on the kinetic analysis of DAG formation and [32P]phosphoinositide breakdown, the first peak of carbachol (1 microM)-stimulated DAG accumulation was found to be related to the breakdown of [32P]phosphatidylinositol 4-monophosphate ([32P]PIP) and [32P]phosphatidylinositol 4,5-bisphosphate ([32P]PIP2). The second peak was found to be related to [32P]PIP2 breakdown. Carbachol stimulated the release of [3H]phosphocholine into the medium, indicating that the predominant pathway for phosphatidylcholine hydrolysis was via phospholipase C. Moreover, carbachol stimulated the release of [3H]choline metabolites in a time- and dose-dependent manner. This agonist slightly stimulated the release of [3H]ethanolamine metabolites. A calmodulin/protein kinase C-dependent mechanism was also studied and was found to be involved in carbachol-stimulated phosphatidylcholine hydrolysis; W-7, a calmodulin inhibitor and staurosporine, a protein kinase C inhibitor, inhibited the carbachol (1-microM)-induced release of [3H]choline metabolites at 20 min in a dose-dependent manner, but did not have inhibitory effects at 5 min. These results suggest that the first peak of DAG accumulation induced by carbachol is predominantly associated with the breakdown [32P]PIP and of [32P]PIP2 and that the second peak is predominantly associated with [32P]PIP2 breakdown and phosphatidylcholine hydrolysis.
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PMID:Mechanism of carbachol-stimulated diacylglycerol formation in rat parotid acinar cells. 132 65

In the dog iris sphincter, muscarinic acetylcholine receptors are coupled either to the stimulation of phospholipase C and muscle contraction or to the stimulation of adenylate cyclase and muscle relaxation, this was found to be dependent upon the concentration of the muscarinic agonist. In contrast to the dog, muscarinic receptors in iris sphincters from different mammalian species were found to be coupled to phospholipase C and contraction at all concentrations of carbachol investigated (1-100 microM). In the dog sphincter, lower concentrations (less than 5 microM) of carbachol stimulated myo-inositol 1,4,5-trisphosphate (IP3) production, inhibited cAMP formation and induced contraction, and higher concentrations (greater than 5 microM) enhanced cAMP formation, inhibited IP3 production and induced relaxation. The mechanisms for the stimulatory effects on cAMP formation through muscarinic receptors were investigated. Carbachol (25 microM) increased both basal and isoproterenol- and forskolin-stimulated cAMP levels. Atropine inhibited the carbachol-stimulated increase in cAMP levels in a dose-dependent manner with an IC50 of 9 nM. Intracellular Ca2+, derived from IP3-induced Ca2+ release and/or from muscarinic receptor-operated Ca2+ influx, and protein kinase C may mediate the muscarinic receptor-linked rise in intracellular cAMP. This conclusion is supported by the following findings. (1) At short time intervals (less than 1 min) carbachol (25 microM) increased IP3 production and contraction and this was followed (between 1 and 20 min) by cAMP formation and muscle relaxation. (2) Carbachol-stimulated IP3 production was detected at a concentration of the agonist 26-fold lower than that required for cAMP formation, and it was completely blocked by the phorbol ester, phorbol 12,13-dibutyrate (50 nM). (3) A Ca(2+)-calmodulin stimulated adenylate cyclase was demonstrated in membranes from dog iris sphincter but not in that from rabbit and bovine. (4) Trifluoperazine (0.1 microM), a calmodulin antagonist, inhibited the carbachol-stimulated cAMP accumulation. (5) The Ca2+ ionophore A23187 and the phorbol ester increased cAMP production in a dose-dependent manner. A23187 potentiated cAMP production induced by either carbachol or by the phorbol ester. (6) Muscarinic stimulation of cAMP production persisted even after the tissue was pretreated with the phorbol ester or staurosporine. (7) Nifedipine (0.01-0.5 microM), a Ca2+ channel antagonist, inhibited carbachol stimulation of cAMP production, suggesting the presence of a muscarinic receptor-operated Ca2+ influx pathway in this tissue.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Carbachol stimulates adenylate cyclase and phospholipase C and muscle contraction-relaxation in a reciprocal manner in dog iris sphincter smooth muscle. 132 47

In order to evaluate the possible contribution of phospholipase D (PLD) stimulation to the mitogenic response, a screening of a variety of different compounds, some of which are known to be potent mitogens, was performed using the well characterized Chinese hamster lung fibroblast (CCL39) cell line. In wild type CCL39 cells, or derivatives expressing high levels of either the human M1 muscarinic receptor (Hm1) or the human epidermal growth factor (EGF) receptor (39M1-81 and 39ER22 clones, respectively), thrombin, a potent mitogen for all three cell types, elicited the rapid activation of PLD (t1/2 activation, 30 s). Carbachol-mediated activation of the Hm1 receptor in the 39M1-81 clone, which is not a mitogenic signal, produced a similarly rapid although greater activation of PLD. Addition of EGF to the 39ER22 clone was able to provoke both a mitogenic response and stimulate PLD, albeit a comparatively small effect. In each case, the stimulation of PLD correlated closely with the ability to stimulate inositol phospholipid breakdown and was entirely dependent on the activation of protein kinase C. Moreover, the ability of both thrombin and carbachol to stimulate PLD was found to be rapidly desensitized, with a similar time course of desensitization (t1/2 desensitization, 90 s). It has recently been reported that an increase in phospholipase C (PLC)-mediated phosphocholine (PC) hydrolysis by either addition of agonist or by extracellular addition of PC-specific PLC enzyme constitutes a mitogenic signal. In this regard, in addition to stimulation of PLD, thrombin and carbachol were both able to stimulate the activity of a phosphocholine-specific phospholipase C (PC-PLC), which did not appear to desensitize within the time course employed. By contrast, EGF was unable to elicit the stimulation of PC-PLC. Ligands such as fibroblast growth factor (FGF) and platelet-derived growth factor (PDGF), which bind to and activate receptors with intrinsic tyrosine kinase activity, are potent mitogens for CCL39 cells but were unable to stimulate either PLD or PC-PLC activity. Furthermore, exogenous addition of purified PC-PLC enzyme, although able to induce a strong and lasting hydrolysis of PC, was unable to produce a mitogenic signal on its own. On the basis of these results, we conclude that the activation of both PLD and PC-PLC is neither sufficient nor required to produce a mitogenic response.
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PMID:Stimulation of phosphatidylcholine breakdown by thrombin and carbachol but not by tyrosine kinase receptor ligands in cells transfected with M1 muscarinic receptors. Rapid desensitization of phosphocholine-specific (PC) phospholipase D but sustained activity of PC-phospholipase C. 133 Oct 66

Phosphorylation of cardiac sarcolemma proteins under stimulation of M-receptors by agonist carbacholine used to stimulate phosphatidylinositide cycle, was investigated in the isolated, rabbit heart perfused with 32Pi. Carbacholine (10(-7) stimulates the polyphosphoinositide metabolism which is expressed in the activated incorporation of 32P from [gamma-32P]ATP in polyphosphoinositide as well as in the increased content of the labelled inositol trisphosphate released through phosphatidylinositol-4,5-bisphosphate break-down by phospholipase C. The diacylglycerol produced simultaneously with inositol triphosphate as a second messenger activates the protein kinase C. This was confirmed by considerable activation of phosphorylation sarcolemma proteins-substrates of protein kinase C, with Mr 94, 87, 78, 51 and 46 kDa.
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PMID:[Phosphorylation of myocardial sarcolemma proteins during induction of the phosphatidylinositol cycle in isolated perfused rabbit heart]. 165 8

IMR-32 and SK-N-MC cells were found to contain [3H]quinuclidinyl benzilate specific binding sites inhibited by pirenzepine in a manner suggesting the presence of both M1-type and M2-type muscarinic receptor recognition sites. Neither cell had detectable [3H]8-OH-DPAT binding sites. Carbachol stimulated the rate of inositol phospholipid breakdown in IMR-32 and SK-N-MC human neuroblastoma cells with an EC50 value of about 50 microM in both cases. Pirenzepine inhibited the carbachol (100 microM)-stimulated inositol phospholipid breakdown in both cells with Hill slopes of unity and IC50 values of 15 nM (IMR-32) and 12 nM (SK-N-MC). The 5-HT1A receptor agonist 8-OH-DPAT competitively inhibited carbachol-stimulated inositol phospholipid breakdown with pA2 values of 5.78 (IMR-32) and 5.61 (SK-N-MC). These values are consistent with the inhibitory potency of 8-OH-DPAT towards [3H]quinuclidinyl benzilate binding in these cells. The 5-HT agonists 5-MeODMT and buspirone at micromolar concentrations inhibited carbachol-stimulated breakdown in IMR-32 cells. The inhibition by 8-OH-DPAT and 5-MeODMT was not affected by preincubation with (-)alprenolol. 5-HT (10-100 microM) was without effect on either basal or carbachol-stimulated breakdown. It is concluded that IMR-32 and SK-N-MC neuroblastoma cells express muscarinic M1-type but not serotoninergic receptors coupled to phosphoinositide-specific phospholipase C. 8-OH-DPAT acts as a weak antagonist at these muscarinic receptors.
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PMID:Antagonism by 8-hydroxy-2(di-n-propylamino)tetraline and other serotonin agonists of muscarinic M1-type receptors coupled to inositol phospholipid breakdown in human IMR-32 and SK-N-MC neuroblastoma cells. 182 86

Serotonin 5-HT1A receptors have been reported to be negatively coupled to muscarinic receptor-stimulated phosphoinositide turnover in the rat hippocampus. In the present study, we have investigated further the pharmacological specificity of this negative control and attempted to elucidate the mechanism whereby 5-HT1A receptor activation inhibits the carbachol-stimulated phosphoinositide response in immature or adult rat hippocampal slices. Various 5-HT1A receptor agonists were found to inhibit carbachol (10 microM)-stimulated formation of total inositol phosphates in immature rat hippocampal slices with the following rank order of potency (IC50 values in nM): 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) (11) greater than ipsapirone (20) greater than gepirone (120) greater than RU 24969 (140) greater than buspirone (560) greater than 1-(m-trifluoromethylphenyl)piperazine (1,500) greater than methysergide (5,644); selective 5-HT1B, 5-HT2, and 5-HT3 receptor agonists were inactive. The potency of the 5-HT1A receptor agonists investigated as inhibitors of the carbachol response was well correlated (r = 0.92) with their potency as inhibitors of the forskolin-stimulated adenylate cyclase in guinea pig hippocampal membranes. 8-OH-DPAT (10 microM) fully inhibited the carbachol-stimulated formation of inositol di-, tris-, and tetrakisphosphate but only partially antagonized (-40%) inositol monophosphate production. The effect of 8-OH-DPAT on carbachol-stimulated phosphoinositide turnover was not prevented by addition of tetrodotoxin (1 microM), by prior destruction of serotonergic afferents, by experimental manipulations causing an increase in cyclic AMP levels (addition of 10 microM forskolin), or by changes in membrane potential (increase in K+ concentration or addition of tetraethylammonium). Prior intrahippocampal injection of pertussis toxin also failed to alter the ability of 8-OH-DPAT to inhibit the carbachol response. Carbachol-stimulated phosphoinositide turnover in immature rat hippocampal slices was inhibited by the protein kinase C activators phorbol 12-myristate 13-acetate (10 microM) and arachidonic acid (100 microM). Moreover, the inhibitory effect of 8-OH-DPAT on the carbachol response was blocked by 10 microM quinacrine (a phospholipase A2 inhibitor) but not by BW 755C (100 microM), a cyclooxygenase and lipoxygenase inhibitor. These results collectively suggest that 5-HT1A receptor activation inhibits carbachol-stimulated phosphoinositide turnover by stimulating a phospholipase A2 coupled to 5-HT1A receptors, leading to arachidonic acid release. Arachidonic acid could in turn activate a gamma-protein kinase C with as a consequence an inhibition of carbachol-stimulated phosphoinositide turnover. This inhibition may be the consequence of a phospholipase C phosphorylation and/or a direct effect on the muscarinic receptor.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Potential mechanisms involved in the negative coupling between serotonin 5-HT1A receptors and carbachol-stimulated phosphoinositide turnover in the rat hippocampus. 184 78

Carbachol (CCh, 10(-8)-10(-4) M) increased in concentration-dependent manner the mass of phosphatidic acid (PA), but not the mass of diacylglycerol (DG) in the Taenia coli from guinea pig. The increase in the amount of PA caused by CCh was maintained for 20 min. Release of choline from choline phospholipids labeled with [methyl-3H]choline was not changed by CCh. A DG kinase inhibitor, R59022, inhibited the CCh-induced increase in the mass of PA. These results indicate that the increase in the mass of PA by CCh is due to immediate phosphorylation by DG kinase to PA, of the DG produced by phospholipase C (PLC). It is not due to formation of PA by the direct action of phospholipase D. CCh increased 45Ca2+ uptake into the tissue. R59022 inhibited the sustained phase of CCh-induced contraction and 45Ca2+ uptake into the tissue, but only slightly inhibited the initial phase of the CCh-induced contraction. This inhibition by R59022 may result from the inhibitory effect on the CCh-induced increase in PA. These results suggest that CCh activates both PLC and DG kinase and the resultant increase in the mass of PA contributes to the regulation of the sustained phase of CCh-induced contraction which is related to Ca2+ influx.
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PMID:Role of phosphatidic acid in carbachol-induced contraction in guinea pig Taenia coli. 185 Aug 69

Synaptoneurosomes obtained from the cortex of rat brain prelabeled with [14C]arachidonic acid [( 14C]AA) were used as a source of substrate and enzyme in studies on the regulation of AA release. A significant amount of AA is liberated in the presence of 2 mM EGTA, independently of Ca2+, primarily from phosphatidic acid and polyphosphoinositides (poly-PI). Quinacrine, an inhibitor of phospholipase A2 (PLA2), suppressed AA release by about 60% and neomycin, a putative inhibitor of phospholipase C (PLC), reduced AA release by about 30%. An additive effect was exhibited when both inhibitors were given together. Ca2+ activated AA release. The level of Ca2+ present in the synaptoneurosomal preparation (endogenous level) and 5 microM CaCl2 enhance AA liberation by approximately 25%, whereas 2 mM CaCl2 resulted in a 50% increase in AA release relative to EGTA. The source for Ca(2+)-dependent AA release is predominantly phosphatidylinositol (PI); however, a small pool may also be liberated from neutral lipids. Carbachol, an agonist of the cholinergic receptor, stimulated Ca(2+)-dependent AA release by about 17%. Bradykinin enhanced the effect of carbachol by about 10-15%. This agonist-mediated AA release occurs specifically from phosphoinositides (PI + poly-PI). Quinacrine almost completely suppresses calcium-and carbachol-mediated AA release. Neomycin inhibits this process by about 30% and totally suppresses the effect of bradykinin. Our results indicate that both phospholipases PLA2 and PLC with subsequent action of DAG lipase are responsible for Ca(2+)-independent AA release. Ca(2+)-dependent and carbachol-mediated AA liberation occurs mainly as the result of PLA2 action. A small pool of AA is probably also released by PLC, which seems to be exclusively responsible for the effect of bradykinin.
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PMID:Ca(2+)-independent, Ca(2+)-dependent, and carbachol-mediated arachidonic acid release from rat brain cortex membrane. 191 75

Carbachol (CCh) a cholinergic agonist which hydrolyses phosphatidyl-inositol bisphosphate (PIP2) to produce the breakdown products inositol trisphosphate (IP3) and diacylglycerol (DAG) was tested for its ability to induce [3H]norepinephrine ([3H]NE) release and to accumulate [3H]inositol phosphate ([3H]IP) under normal and membrane depolarizing conditions. Our results suggest two major points: first, muscarinic acetylcholine receptor (mAChR) agonists and depolarizing agents (of which KCl is the most effective) act in concert to induce potentiation of PI turnover and potentiation of neurotransmitter release. The simultaneous presence of both a depolarizing agent and a receptor agonist is obligatory for eliciting potentiatory effect. Facilitation of release by muscarinic agonist and K+, added together, was 2 to 5-fold above additivity and the levels of [3H]IP accumulated were 3-5-fold above additivity by K+ and CCh. Enhancement of release and of [3H]IP formation is reversed by pirenzepine, a muscarinic (MI) specific antagonist, Kdiss = 0.4 and 0.8 microM, respectively. Second, synergy of IP accumulation in correlation with synergy of neurotransmitter release elicited by mAChR activation and membrane depolarization, suggests a possible role for phospholipase C (PLC) in the bifurcating control of neurotransmitter release and for the involvement of PLC and voltage sensitive channels in mediation of long-term potentiation (LTP).
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PMID:Potentiation of neurotransmitter release coincides with potentiation of phosphatidyl inositol turnover. A possible in vitro model for long term potentiation. 196 29

On separation of rat pancreatic plasma membrane proteins by two-dimensional gel electrophoresis, 15 GTP-binding protein (G-protein) alpha-subunits could be detected immunochemically using an alpha common antibody. These consisted of five 48 kDa proteins (pI 5.70, 5.80, 5.90, 6.10 and 6.25) and five 45 kDa proteins (pI 5.90, 6.05, 6.25, 6.30 and 6.70), presumably corresponding to low- and high-molecular mass forms of the Gs-protein, as well as three 40/41 kDa proteins (pI 5.50, 5.70 and 6.00) and two 39 kDa proteins (pI 5.50 and 6.00). All of these proteins except for the more acidic 39 kDa protein were ADP-ribosylated by cholera toxin (CT). In addition, the three 40/41 kDa proteins and the more alkaline 39 kDa protein were also ADP-ribosylated by pertussis toxin (PT). CT- and PT-induced ADP-ribosylation changed the pI values of G-protein alpha-subunits by 0.2 pI units to more acidic values. Preincubation of isolated pancreatic membranes with cholecystokinin octapeptide (CCK-OP), which stimulates phospholipase C in acinar cells, decreased CT-induced as well as PT-induced ADP-ribosylation of the three 40/41 kDa proteins, whereas CT-induced ADP-ribosylation of one 45 kDa (pI 5.80) and all 48 kDa proteins was enhanced in the presence of CCK. Carbachol, another stimulant of phospholipase C, had no effect. The three 40/41 kDa proteins and one 48 kDa protein could be labelled with the GTP analogue [alpha-32P]GTP-gamma-azidoanilide. CCK, but not carbachol, stimulated incorporation of the GTP analogue into all of these four proteins. Using different anti-peptide antisera specific for alpha-subunits of G-proteins we identified the three 40/41 kDa Gi-proteins as Gi1 (pI 6.00), Gi2 (pI 5.50) and Gi3 (pI 5.70). The Gi3-protein was found to be the major Gi-protein of pancreatic plasma membranes. One of the 39 kDa proteins (pI 6.0) was identified as Go. These results indicate that CCK receptors functionally interact with six Gs-proteins and with Gi1, Gi2 and Gi3-proteins. Since evidence suggests that a 40/41 kDa CT substrate is involved in the stimulation of phospholipase C in pancreatic acinar cells, it is likely that one, two or all three 40/41 kDa Gi-proteins are involved in the coupling of CCK receptors with phospholipase C.
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PMID:Cholecystokinin activates Gi1-, Gi2-, Gi3- and several Gs-proteins in rat pancreatic acinar cells. 211 41


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