Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
 ...
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

Rabbit brain cortical membranes, which have been extracted with 2 M KCl, hydrolyze exogenously added [3H]phosphatidylinositol [( 3H]PI) in a guanine nucleotide- and carbachol-dependent manner. Both oxotremorine-M and carbachol are full agonists with EC50 values of 8 and 73 microM, respectively. Pirenzepine and atropine inhibit carbachol-stimulated [3H]PI hydrolysis. The hydrolysis-resistant guanine nucleotide analog guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) is the most potent in supporting carbachol-stimulated hydrolysis of PI. There is no effect of carbachol in the absence of guanine nucleotides or in the presence of 100 microM adenosine 5'-O-(3-thiotriphosphate), adenosine-5'-(beta, gamma-imido)triphosphate, or sodium pyrophosphate. Guanylyl-5'-(beta,gamma-imido)triphosphate [Gpp(NH)p] in the presence of carbachol also stimulates PI hydrolysis although much less than that seen with GTP gamma S. GDP and Gpp(NH)p are potent antagonists of the GTP gamma S-dependent carbachol response. Optimal stimulation by carbachol and GTP gamma S was observed at 0.3-1 microM free Ca2+ and 6 mM MgCl2. Limited trypsinization resulted in loss of receptor-regulated PI breakdown and a slight decrease in basal activity. These results demonstrate that phospholipase C hydrolysis of exogenous PI by rabbit cortical membranes may be stimulated by carbachol in a guanine nucleotide-dependent manner.
 ...
PMID:Muscarinic cholinergic stimulation of exogenous phosphatidylinositol hydrolysis is regulated by guanine nucleotides in rabbit brain cortical membranes. 201 56

Activation of rat uterine myometrial muscarinic receptors with a variety of agonists results in increased phosphatidylinositol metabolism. Activation with carbachol is concentration- and time-dependent and is most apparent by following the accumulation of inositol monophosphate although there are small but significant increases of inositol bisphosphate and inositol trisphosphate. Carbachol stimulation of phospholipid turnover is greatest in the upper third of the uterus. The carbachol-induced increase of inositol monophosphate is antagonized by atropine and by the selective M-3 muscarinic receptor antagonist 4-diphenylacetoxy-N-methylpiperidine methobromide. Pirenzepine, a selective M-1 receptor antagonist is less active, whereas gallamine and 11-2[[(diethylamino)methyl]-1-piperidinyl]acetyl]-5, 11-dihydro-6H-pyrido[2,3-b][1,4]benzodiazepine-6-one, selective M-2 receptor antagonists, are minimally effective suggesting that muscarinic M-3 receptors modulate phospholipid turnover in the rat myometrium. Displacement of tritium-quinuclidinyl benzilate binding by muscarinic antagonists also supports the presence of M-3 receptors in the uterus. Incubation with phorbol 12, 13-dibutyrate significantly reduced the accumulation of inositol monophosphate induced by carbachol implying that protein kinase C might modulate the responsiveness of the M-3 receptors in the rat uterus. Our results suggest that the intracellular concentration of calcium required for the contraction of the rat myometrium may be modulated, in part, through M-3 muscarinic receptors coupled to phospholipase C-activated turnover of phosphoinositides.
 ...
PMID:Pharmacological characterization of the muscarinic receptors mediating phosphoinositide hydrolysis in rat myometrium. 254 Mar 9

Primary astrocytic cultures derived from day-15 chick embryo (E15) cerebral hemispheres (CH) or cerebellum (CB) express a calcium/phospholipid-dependent isoform as the major protein kinase C (PKC-alpha/beta). PKC was activated (translocation of activity from cytosol to membrane) following stimulation with carbachol, so we tested for activation of phospholipase C (PLC) as the source of diacylglycerol released from polyphosphoinositide (PIP2) hydrolysis. Carbachol activated PLC (inositol phosphate release) 4-fold in a time- and dose-dependent manner in cortical (CH) astrocytes, but there was no activation of PLC in astrocytes from cerebellum (CB). Pirenzepine, but not gallamine, attenuated both carbachol-induced PKC translocation and PIP2 hydrolysis in E15CH astrocytes, arguing for contribution of M1 subtype. The phorbol ester TPA completely inhibited PIP2 hydrolysis, both basal and carbachol-stimulated, and elicited a stronger, but shorter (10 min) activation of PKC than that observed with carbachol. We investigated phospholipase D (PLD) activation as an alternate source of diacylglycerol in astrocytes, since the ratio of PLC to PKC activation by carbachol was lower in astrocytes than observed in neurons. We observed a dramatic (10-fold) time- and dose-dependent activation of PLD by TPA in CH and a 3-fold increase in CB. The duration of TPA-dependent PLD activation correlated well with increased cell proliferation and changes in astrocytic phenotype markers. Carbachol-stimulated PLD activation was observed in CH but not in CB astrocytes, being mostly dependent on the M3 receptor subtype in the former. In contrast, glutamate elicited a greater PLD activation in CB astrocytes, than in CH astrocytes. TPA activation of PLD was totally blocked by staurosporine (PKC inhibitor) and genistein (a tyrosine kinase inhibitor) in cerebellar (CB) astrocytes; however, total inhibition of TPA-dependent PLD activation was only achieved in cortical (CH) astrocytes after addition of EGTA. Thapsigargin activated PLD in both populations, further emphasizing the PLD activation dependency on [Ca2+]i. Taken together with our previous observations that TPA induces proliferation, cytoskeleton changes, and decreases of glutamine synthetase activity, these data suggest that phospholipase D is a differential but important participant in the regulation of the signalling of mitosis and differentiation in astrocytes during their development.
 ...
PMID:Differential regulation of phospholipases C and D by phorbol esters and the physiological activators carbachol and glutamate in astrocytes from chicken embryo cerebrum and cerebellum. 755 28

Acetylcholine (ACh) caused a dose-dependent contraction of gallbladder muscle cells in either a normal (1.9 mM) Ca2+, zero-Ca2+ or 4 mM Sr2+ medium, with a maximal contraction about 21 +/- 1% at 10(-6) M. Pirenzepine, methoctramine and p-fluoro-hexahydro-sila-difenidol (the M1, M2 and M3 antagonist, respectively) alone had no inhibitory effect on ACh-induced contraction in normal Ca2+ medium, which was blocked by the combination of methoctramine and p-F-HHSiD. In the 4 mM Sr2+ medium, methoctramine dose dependently inhibited ACh-induced contraction and shifted the ACh dose-response curve to the right. The contraction induced by ACh was further blocked by 10(-4) M propranolol (phosphatidic acid phosphohydrolase inhibitor that prevents the production of diacylglycerol from phospholipase D activation), 10(-5) M H-7 and chelerythrine (the protein kinase C inhibitors) by 64%, 75% and 77%, respectively. In contrast, in the zero-Ca2+ medium, p-fluoro-hexahydro-sila-difenidol dose-dependently inhibited ACh-induced contraction and shifted the ACh dose-response curve to the right. The action of ACh was further blocked by 10(-6) M U-73122 (phospholipase C inhibitor) and 10(-5) M CGS 9343B (calmodulin antagonist) by 95% and 77%, respectively. In conclusion, ACh contracts the gallbladder muscle by stimulating the M2 and M3 muscarinic receptors. The M2 receptors are linked to Ca2+ influx, activation of phospholipase D and protein kinase C-dependent pathway, whereas the M3 receptors are preferentially associated with the activation of phospholipase C, intracellular Ca2+ release and calmodulin-dependent pathway.
 ...
PMID:Distinct muscarinic receptors and signal transduction pathways in gallbladder muscle. 775 67

The coupling of muscarinic-cholinergic receptors (mAchR) with the phospholipase C (PLC) second messenger system has been demonstrated in central nervous system (CNS) tissue of many animal species. However, little information exists regarding this association in the developing human CNS. Due to the suggested role of acetylcholine in the regulation of development and differentiation of neural cells, the knowledge of these relationships during human fetal development acquires singular importance. Because of this, we examined the cholinergic stimulation of PLC in human fetal CNS organotypic tissue cultures. Agonist treatment of cultures, in the presence of lithium, resulted in a 4-6-fold increase in inositol phosphates formation. This increase was caused principally by the formation of inositol phosphate (IP). However, kinetic studies demonstrated that the levels of IP2, IP3 and IP4 also increased rapidly after stimulation reaching maximum levels before IP. These results support the hypothesis that muscarinic receptor activation results in an increase in the hydrolysis of PIP2. The inositol phosphate formation was dependent on agonist concentration. The obtained EC50 values were approximately 57 +/- 15 microM for carbachol, 8 +/- 2 microM for acetylcholine and 49 +/- 15 microM for oxotremorine. The agonist-dependent formation of inositol phosphates was inhibited by the muscarinic antagonists atropine and pirenzepine. Pirenzepine inhibited carbachol stimulation with high affinity (Ki = 2.90 +/- 1.15 nM), indicating that PLC activation is the result of activation of the m1 subtype of muscarinic receptors. Treatment of cultures with pertussis toxin did not result in inhibition of agonist-dependent activation of PLC. This result suggests that the m1 muscarinic receptor is coupled to PLC through Gq.
 ...
PMID:Muscarinic receptor-dependent activation of phospholipase C in human fetal central nervous system organotypic tissue culture. 892 76