Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The muscarinic acetylcholine receptor-mediated inhibition of adenylate cyclase was studied in slices of guinea-pig cerebral cortex under normal and depolarizing conditions. Carbachol (1 mM) inhibited basal and isoproterenol (50 microM)-stimulated cyclic AMP (cAMP) accumulation by 20% and 25%, respectively, in normal Krebs-Ringer bicarbonate buffer solution (KRB). High-K+ medium (42 mM K+) increased cAMP accumulation to 330% of the basal level and abolished the inhibitory effect of carbachol. It also abolished the effect of morphine, an agonist of opioid receptors. Low-Ca2+ KRB or the presence of the Ca2+ channel blocker nifedipine, counteracted the effect of high K+ and restored the inhibitory effect of carbachol on the cAMP level. Pretreatment of slices with W-7 or trifluoperazine, two calmodulin antagonists, had the same effect as low Ca2+ or nifedipine on high-K(+)-stimulated cAMP accumulation and caused reappearance of the inhibitory effects of carbachol and morphine. On the contrary, H-7, an inhibitor of protein kinase C, and neomycin, an inhibitor of phospholipase C, had no significant effect on high-K(+)-induced phenomena and did not restore the effect of carbachol. These data suggest that the Ca2(+)-calmodulin system activated by membrane depolarization regulates the cAMP level directly and also by affecting the receptor-mediated process in nerve cells.
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PMID:Disappearance in high-K+ medium of receptor-mediated inhibition of adenylate cyclase in guinea-pig cortical slices. 217 2

When dispersed chief cells from guinea pig stomach were first incubated with carbachol, washed, and then reincubated with carbachol in fresh incubation solution, the stimulation of pepsinogen secretion and the rise in intracellular calcium concentration during the second incubation were reduced. Carbachol did not cause residual enzyme secretion, but the same range of concentrations that causes enzyme secretion caused desensitization that was rapid, temperature dependent, and reversible with time. Preincubation with carbachol caused approximately a 65% reduction in enzyme secretion stimulated during a subsequent incubation with this agonist, but the potency of carbachol was unaffected. Prior exposure to carbachol also reduced subsequent stimulation caused by cholecystokinin (CCK-8), gastrin I, ionophore A23187, or 12-O-tetradecanoylphorbol 13-acetate but did not alter stimulation by any agonist that increases cellular cAMP. Carbachol pretreatment of Fura-loaded chief cells caused a threefold increase in the EC50 for carbachol-stimulated [Ca2+]i and approximately a 30% reduction in the maximal rise in [Ca2+]i in response to carbachol or CCK-8. Inhibition of [N-methyl-3H] scopolamine binding by carbachol following carbachol pretreatment indicated that modulation of receptor affinity or number did not account for functional desensitization. These data indicate that carbachol causes heterologous desensitization of pepsinogen secretion stimulated by agonists that mobilize cellular Ca2+ or activate protein kinase C through a postreceptor action and suggest that an attenuated rise in chief cell calcium is one mechanism mediating the desensitization of enzyme secretion.
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PMID:Cholinergic desensitization of pepsinogen secretion and calcium mobilization of dispersed guinea pig chief cells. 229 23

The effects of the phorbol ester, 12-O-tetradecanoylphorbol 13-acetate (TPA) on amylase secretion and cytoplasmic free calcium concentration ([Ca2+]i) were investigated in dispersed guinea pig pancreatic acini. Carbachol evoked dose-dependent increases in amylase secretion and [Ca2+]i with half-maximal responses at 2.5 and 5 microM, respectively. Carbachol-induced calcium transients could be blocked by atropine. In the presence of a maximal effective dose of carbachol, cholecystokinin octapeptide caused no further increase in [Ca2+]i, suggesting that both agonists act on the same pool of trigger calcium. TPA (10(-9)-10(-6) M) stimulated amylase secretion with no change in [Ca2+]i. Maximum amylase secretion occurred at 0.5 microM TPA. Preincubation of acini in the presence of TPA resulted in a time- and dose-dependent inhibition (IC50 = 30 nM) of the carbachol-induced rise in [Ca2+]i, the maximal effect being observed within 3 min. The inactive phorbol ester, 4 alpha-phorbol 12,13-didecanoate was ineffective in inhibiting the carbachol-stimulated rise in [Ca2+]i. These findings suggest that, in addition to stimulating amylase secretion, probably through protein kinase C, TPA may also exert a negative feedback control over secretagogue-induced calcium transients.
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PMID:Calcium concentration and amylase secretion in guinea pig pancreatic acini: interactions between carbachol, cholecystokinin octapeptide and the phorbol ester, 12-O-tetradecanoylphorbol 13-acetate. 243 19

Growth hormone-releasing hormone (GHRH) and the phorbol ester tetradecanoylphorbol acetate (TPA) each stimulated a rapid and extensive (up to 15-fold) increase in the secretion of growth hormone from cultured ovine anterior pituitary cells. Effects of the releasing hormone on growth hormone secretion were associated with a concurrent, large increase in cellular cyclic AMP accumulation. TPA induced a much smaller (26-78%), though still significant, increase in cellular cyclic AMP levels. Forskolin and isobutylmethylxanthine (IBMX) also stimulated growth hormone secretion and cyclic AMP accumulation. When combined with a maximally effective concentration of GHRH these compounds did not further elevate growth hormone secretion even though they induced further increases in cyclic AMP concentration; this is consistent with activation occurring via a common cyclic AMP-dependent pathway. In contrast TPA when combined with maximally effective concentrations of either GHRH, forskolin or IBMX caused additional release of growth hormone, suggesting that the TPA-induced secretion involved a cyclic AMP-independent process. However, TPA also markedly potentiated the cellular cyclic AMP accumulation due to each of these agents. That TPA induced stimulation of basal and GHRH-stimulated cyclic AMP levels measured in the presence of IBMX suggests an action affecting cyclic AMP synthesis. Carbachol had no effect on basal or GHRH-stimulated growth hormone secretion or cyclic AMP levels. The two actions of TPA, one on secretion and one on cyclic AMP metabolism, may result from activation of some common event possibly involving protein kinase C. Our results suggest that GHRH and TPA activate independent pathways regulating growth hormone secretion.
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PMID:Regulation of growth hormone secretion and cyclic AMP metabolism in ovine pituitary cells: interactions involved in activation induced by growth hormone-releasing hormone and phorbol esters. 246 92

Phosphoinositide hydrolysis, a major mechanism for signal transduction in neural cells, generates diacylglycerol, which can in turn activate protein kinase C (PKC). Although cholinergic agonists elicit phosphoinositide hydrolysis in neural tissues, little is known about activation of PKC by cholinergic agonists. PKC requires phosphatidylserine for activation, and in intact cells this lipid requirement is satisfied by binding of the enzyme to cell membranes. Therefore, in intact cells, activation of PKC is often associated with a decrease in cytosolic PKC activity accompanied by an increase in membrane-associated activity. We studied cholinergic-induced activation of PKC by examining changes in the subcellular distribution of the enzyme in PC12 cells treated with cholinergic drugs. Carbachol (1 mM) induced large and rapid increases in membrane-associated PKC activity; a maximal increase of 460% occurred after 5 sec of incubation. Carbachol-induced PKC translocation was concentration-dependent, with a biphasic dose-response curve yielding approximate EC50 values of 10(-6) M and 10(-4) M for the high- and low-affinity components, respectively. Experiments with selective cholinergic agents demonstrated that both muscarinic and nicotinic receptors are involved in carbachol-induced PKC translocation, but the response is predominantly mediated by nicotinic receptor stimulation. Muscarinic-induced association of PKC with cell membrane fractions was resistant to extraction by chelators, whereas nicotinic-mediated membrane binding was partially reduced by homogenization of cells in the presence of EGTA. Omission of calcium from the incubation medium or chelation of calcium with EGTA completely blocked muscarinic- and nicotinic-induced translocation. In addition, the calcium channel blocker nifedipine reduced the nicotinic response by 60%. (ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Nicotinic and muscarinic agonists stimulate rapid protein kinase C translocation in PC12 cells. 249 78

1,2-Bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (BAPTA/AM), an intracellular calcium [( Ca2+]i) chelator, was used to investigate the role of [Ca2+]i in acid secretory activity and protein phosphorylation in parietal cells from rabbit. Chelation of extracellular calcium [( Ca2+]o) with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid did not prevent the initial carbachol-induced elevation of [Ca2+]i as measured with the fluorescent Ca2+ probe, fura-2, and only partially inhibited [14C]-aminopyrine (AP) accumulation, an indirect indicator of acid secretory activity. [Ca2+]i chelation with BAPTA/AM eliminated carbachol-stimulated increases in [Ca2+]i and AP accumulation but only transiently reduced histamine stimulation of AP accumulation. Carbachol increased phosphorylation of a 36-kDa, pI approximately 7 protein (pp36) and transient phosphorylation of a 28-kDa, pI approximately 5 protein (pp28), whereas histamine increased phosphorylation of 40-kDa, pI approximately 6.5 (pp40) and 27-kDa, pI approximately 6.2 (pp27) proteins. Phosphorylation of pp36 and pp28 were mimicked by the protein kinase C activator, 12-O-tetradecanoylphorbol-13-acetate (TPA) and the calcium ionophore, ionomycin, respectively. Two other phosphoproteins with molecular weights of 66,000 and pIs of 5.7 and 5.9 were also phosphorylated in response to TPA and carbachol. Chelation of [Ca2+]i and [Ca2+]o blocked carbachol-induced phosphorylation of pp28 and pp36 and ionomycin phosphorylation of pp28 but not TPA-stimulated phosphorylation of pp36 or the two pp66s or histamine-stimulated phosphorylation of pp27 or pp40. Chelation of [Ca2+]i alone did not block increases in [Ca2+]i or phosphorylation of pp28 in response to ionomycin. Both pp28 and pp36 were localized in both microsomal and cytosolic fractions of cells, which suggests involvement in cytoskeleton-membrane interactions. These phosphoproteins could be common elements of Ca2+-dependent stimulus-secretion coupling as similar proteins were phosphorylated by carbachol and cholecystokinin (CCK) in chief cells. Based on data with TPA and ionomycin, both protein kinase C and an as yet unidentified Ca2+-dependent protein kinase(s) appear to be activated upon stimulation with cholinergic agonists and CCK.
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PMID:Carbachol-induced protein phosphorylation in parietal cells: regulation by [Ca2+]i. 250 25

We examined the effects of various stimuli on immunoreactive insulin (IRI) and glucagon (IRG) release from perfused pancreases isolated from control and streptozocin-induced diabetic (STZ-D) rats. Diabetes was induced by injecting 30 mg/kg STZ into rats fasted for 16-18 h 12-17 days before our experiments. Glucose (11.1 mM) caused a distinct biphasic pattern of IRI release from the control pancreas, whereas the first phase was marginal and the second phase was absent in the diabetic pancreas. Arginine (20 mM)-induced IRI release was similar in both groups, whereas IRG release was greater in the control rats than in the diabetic rats. Thus, this model of STZ-D simulates a certain class of non-insulin-dependent diabetes mellitus (NIDDM). In these diabetic animals, the cholecystokinin (CCK) analogue ceruletide (620 pM) caused a significantly greater increase in IRI release in the presence of 5.6 mM glucose than in the control rats, but ceruletide caused a similar IRG release in both groups. Because CCK and ceruletide stimulate phosphoinositide turnover in pancreatic islets, we examined the effects of carbachol and phorbol ester TPA on IRI release in the presence of 5.6 mM glucose. Carbachol (10 microM), which is thought to generate similar second messengers as ceruletide, induced greater IRI release in diabetic than in control rats. TPA (100 nM) caused a significantly greater increase in IRI release from the diabetic than the control pancreas. Our results demonstrate that the insulin-releasing mechanism involved in protein kinase C activation is enhanced in this model of NIDDM.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Increased beta-cell secretory responsiveness to ceruletide and TPA in streptozocin-induced mildly diabetic rats. 252 62

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.
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PMID:Pharmacological characterization of the muscarinic receptors mediating phosphoinositide hydrolysis in rat myometrium. 254 Mar 9

We examined the relationship between phosphatidylcholine (PC) hydrolysis, phosphoinositide hydrolysis, and diacylglycerol (DAG) formation in response to muscarinic acetylcholine receptor (mAChR) stimulation in 1321N1 astrocytoma cells. Carbachol increases the release of [3H]choline and [3H]phosphorylcholine ([3H]Pchol) from cells containing [3H]choline-labeled PC. The production of Pchol is rapid and transient, while choline production continues for at least 30 min. mAChR-stimulated release of Pchol is reduced in cells that have been depleted of intracellular Ca2+ stores by ionomycin pretreatment, whereas choline release is unaffected by this pretreatment. Phorbol 12-myristate 13-acetate (PMA) increases the release of choline, but not Pchol, from 1321N1 cells, and down-regulation of protein kinase C blocks the ability of carbachol to stimulate choline production. Taken together, these results suggest that Ca2+ mobilization is involved in mAChR-mediated hydrolysis of PC by a phospholipase C, whereas protein kinase C activation is required for mAChR-stimulated hydrolysis of PC by a phospholipase D. Both carbachol and PMA rapidly increase the formation of [3H]phosphatidic acid ([3H]PA) in cells containing [3H]myristate-labeled PC. [3H]Diacylglycerol ([3H]DAG) levels increase more slowly, suggesting that the predominant pathway for PC hydrolysis is via phospholipase D. When cells are labeled with [3H]myristate and [14C]arachidonate such that there is a much greater 3H/14C ratio in PC compared with the phosphoinositides, the 3H/14C ratio in DAG and PA increases with PMA treatment but decreases in response to carbachol. By analyzing the increase in 3H versus 14C in DAG, we estimate that the DAG that is formed in response to PMA arises largely from PC. Muscarinic receptor activation also causes formation of DAG from PC, but approximately 20% of carbachol-stimulated DAG appears to arise from hydrolysis of the phosphoinositides.
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PMID:Muscarinic receptor activation of phosphatidylcholine hydrolysis. Relationship to phosphoinositide hydrolysis and diacylglycerol metabolism. 254 33

The interaction of neurotransmitters with their specific receptors initiates a cascade of intracellular biochemical events which lead to induction of specific genes. Included in this cascade is the rapid and transient induction of a family of primary early response genes we term TIS genes (Lim et al.: Oncogene 1: 263-270, 1987). Expression of six TIS gene, including c-fos, was examined in secondary cultures of rat neocortical astrocytes exposed to muscarinic and adrenergic agonists and antagonists to study the early genomic responses which accompany neurotransmitter-induced alteration of glial morphology and physiology. Carbachol induced accumulation of mRNA for c-fos and the other TIS genes. Carbachol-mediated induction of TIS mRNA expression was sensitive to atropine blockade and was potentiated by lithium. Norepinephrine (NE), isoproterenol, or phenylephrine also induced TIS mRNA accumulation. In order to determine which second-messenger pathways mediate NE induction of TIS gene expression, the influences of the beta(B) antagonist propranolol (PR), the alpha I(AI) antagonist prazosin (PZ), and the alpha 2(A2) antagonist yohimbine (YB) were examined. The induction of TIS1 mRNA by NE was partially blocked by PR or PZ alone, and completely abolished by both antagonists in combination. YB had no effect on TIS1 mRNA expression. These results suggest that NE induces TIS1 mRNA through both B- and A 1-adrenergic, but not A2, pathways. The lack of effect of inhibitors of phospholipase A2 and cyclooxygenase suggests that the A1 component is mediated through a protein kinase C pathway. The induction of transient gene expression by neurotransmitters may mediate the secondary genomic responses and phenotypic changes occurring in astrocytes in response to alterations in neuronal neurotransmitter release.
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PMID:Induction of c-fos and TIS genes in cultured rat astrocytes by neurotransmitters. 257 4


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