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)

Guanosine 5'-O-(gamma-thio)triphosphate (GTP[S]), NaF and cholecystokinin-octapeptide (CCK-8) were used to examine the participation of G proteins in agonist-induced contraction of smooth muscle cells isolated separately from circular and longitudinal muscle layer of guinea pig intestine. All three agents stimulated inositol 1,4,5-triphosphate (InsP3) production and protein kinase C activity to the same extent in permeabilized (GTP[S] and CCK-8) and nonpermeabilized (NaF and CCK-8) muscle cells. InsP3 production was 9 to 13 times higher in circular muscle cells consistent with preferential hydrolysis of phosphatidylinositol 4,5-biphosphate in this cell type. InsP3 production and protein kinase C activation in permeabilized muscle cells were abolished by guanosine 5'-O-(beta-thio)diphosphate (10 microM). Maximal concentrations of GTP[S] (100 microM), CCK-8 (1 nM) and InsP3 (1 microM) elicited similar increases in [Ca++]i, net 45Ca++ efflux and contraction in permeabilized circular, but not longitudinal, muscle cells [( Ca++]i: 224 +/- 35 nM, 279 +/- 29 nM and 288 +/- 45 nM increase above basal level; 45Ca++ efflux: 35 +/- 2%, 34 +/- 3% and 37 +/- 3% decrease in cell Ca++ content; contraction: 26 +/- 2%, 24 +/- 2% and 25 +/- 2% decrease in cell length). The responses to GTP[S] and CCK-8 were abolished by guanosine 5'-O-(beta-thio)diphosphate (10 microM) and heparin (10 micrograms/ml), whereas the response to InsP3 was abolished by heparin only. Maximal concentrations of NaF and CCK-8 elicited similar increases in [Ca++]i and contraction in nonpermeabilized circular and longitudinal muscle cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Receptor-coupled G proteins mediate contraction and Ca++ mobilization in isolated intestinal muscle cells. 130 82

Elucidation of receptors and mediators regulating gastric pepsinogen secretion has lagged behind understanding of the factors that control acid secretion. During the past decade, as a consequence of the development of in vitro models for studying the control of pepsinogen secretion at the cellular level, much information about chief cell receptors and signal-transduction mechanisms has been obtained, including the identification and characterization of receptors for secretin, vasoactive intestinal polypeptide, cholinergic agonists, gastrin, cholecystokinin, peptide YY, and cholera toxin. Moreover, these cell preparations have permitted secretagogue-induced changes in chief-cell calcium concentration, protein kinase C distribution, and phosphoinositide and cyclic nucleotide content to be measured and related to changes in pepsinogen secretion. This article reviews these advances, discusses areas of uncertainty and controversy, and indicates areas for future investigation.
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PMID:Gastric chief cells: receptors and signal-transduction mechanisms. 131 85

This study investigates the interaction between physiological doses of the synthetic gut hormones, cholecystokinin-octapeptide (CCK8) and secretin on pancreatic juice secretion in the anaesthetized rat and on amylase secretion and Ca2+ and Mg2+ mobilization in isolated pancreatic segments and acinar cells. CCK8 (150 pmol kg-1 h-1) and secretin (100 pmol kg-1 h-1) evoked marked time course increases in pancreatic juice flow, total protein output and amylase secretion in the anaesthetized rat when administered separately compared to saline controls. Simultaneous intravenous infusion of CCK8 and secretin did not yield either an additive response or a potentiation but instead it caused a decrease in secretory responses. Administration of either polymyxin B (10(-8) mol kg-1 h-1) or staurosporine (10(-8) mol kg-1 h-1), two protein kinase C inhibitors, simultaneously with both CCK8 and secretin caused a further decrease in all secretory parameters. Superfusing pancreatic segments with either CCK8 (10(-11) M) or secretin (10(-11) M) elevated amylase output compared to the smaller response with a combination of CCK8 and secretin. Combining staurosporine (10(-6) M) with CCK8 and secretin resulted in a further decrease in amylase output. CCK8 (10(-11) M) evoked a large increase in radiolabelled Ca2+ influx into pancreatic segments and elevated cytosolic free Ca2+ concentration ([Ca2+]i) in acinar cells loaded with the fluorescent dye, Fura-2. Secretin (10(-11) M) alone had no significant effect on Ca2+ mobilization but it markedly attenuated the increases in radiolabelled Ca2+ influx and [Ca2+]i elicited by CCK8. In superfused pancreatic segments CCK8 (10(-11) M) evoked a net efflux of Mg2+ whereas secretin (10(-11) M) induced a net uptake of Mg2+. Combining secretin with CCK8 also resulted in a net uptake of Mg2+. The results indicate that both Ca2+ and Mg2+ mobilization may be associated with the interaction between CCK8 and secretin in the rat pancreas.
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PMID:Interaction between secretin and cholecystokinin-octapeptide in the exocrine rat pancreas in vivo and in vitro. 137 28

1. In the present time-course study, we have examined the interactions between the phorbol ester, 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and the synthetic gut hormones, cholecystokinin-octapeptide (CCK-8) and secretin on pancreatic juice secretion in anaesthetized rat. 2. Administration of either TPA (10(-8) mol kg-1 hr-1), secretin (100 pmol kg-1 hr-1) or CCK-8 (150 pmol kg-1 hr-1) in the anaesthetized rat resulted in marked time-course increases in pancreatic juice flow, amylase secretion and total protein output compared to saline controls. The effect of secretin on juice flow was more pronounced and sustained compared to the smaller responses obtained with either CCK-8 or TPA. Similarly, CCK-8 evoked increases in protein output and amylase secretion compared to the responses obtained with either secretin or TPA. 3. Simultaneous infusion of TPA with either CCK-8 or secretin resulted in a marked reduction in pancreatic juice flow, total protein output and amylase secretion compared to the responses obtained with either CCK-8 or secretin alone. 4. Administration of polymyxin B (10(-8) mol kg-1 hr-1), a protein kinase C inhibitor with either TPA and CCK-8 or TPA and secretin caused a partial reduction of the inhibitory effect of TPA on CCK-8 and secretin-evoked secretory responses. 5. The present study further implicates the involvement of protein kinase C in the modulation of CCK-8 and secretin-induced pancreatic juice secretion in the anaesthetized rat.
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PMID:Secretagogue-evoked time-course changes on pancreatic juice secretion in the anaesthetized rat. 137 70

This study shows the presence of seven different low-molecular-weight GTP binding proteins (smg proteins) with molecular masses between 18 and 27 kDa in subfractions of rat pancreatic acinar cells. After stimulation of isolated intact and permeabilized pancreatic acinar cells with cholecystokinin octapeptide (CCK-OP), the diacylglycerol (DG) analogue 12-O-tetradecanoylphorbol 13-acetate (TPA), vasoactive intestinal peptide (VIP), adenosine 3',5'-cyclic monophosphate (cAMP), or guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S), [alpha-32P]GTP binding to 21- to 22-kDa smg protein(s) in microsomal membranes (MM) was reduced, whereas the [alpha-32P]GTP binding to 23-kDa protein(s) was enhanced. In addition, prestimulation of permeabilized cells with GTP gamma S caused enhancement of [alpha-32P]GTP binding to a 19-kDa protein in MM [immunologically identified as the ADP-ribosylation factor (arf)]. In the presence of cytosol, direct addition of GTP gamma S to isolated MM resulted in an apparent translocation of the 19-kDa protein (arf) from the cytosol to membranes. This indicates increased association of arf with the membrane in its GTP-bound state. In CCK-OP-prestimulated acinar cells, [alpha-32P]GTP binding to plasma membrane-located 21- to 22-kDa proteins (immunologically identified as p21ras proteins) was enhanced, suggesting that there is an interrelationship between p21ras proteins and CCK receptors. Our results give evidence for a role of 19-kDa, 21- to 22-kDa, and 23-kDa smg proteins in cAMP-protein kinase A- and DG-protein kinase C-mediated stimulation of intracellular pathways in pancreatic acinar cells.
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PMID:Effects of agonists on p21ras and ras-related proteins in rat pancreatic acinar cells. 141 52

Protein kinase C appears to play an important, yet complex role in the supramaximal inhibition of pancreatic acinar cell secretion observed in response to cholecystokinin (CCK). The addition of protein kinase C activation to the concentration-response curve of a partial agonist acting at the CCK receptor (a phenethyl ester analogue of CCK), transforms a curve without supramaximal inhibition to a full agonist curve typical of CCK. This effect can be elicited by low concentrations of phorbol ester (50pM to 1nM 12-0-tetradecanoyl-phorbol-13-acetate) or by hormonal agonists (0.1 microM carbamylcholine, 10pM bombesin, 1pM CCK-8) which activate protein kinase C, but not by agonists acting via alternate second messengers (VIP). Of interest, this effect is dependent on preincubation of the acinar cells with the protein kinase C activator at 37 degrees C, with the effect rapidly reversed by transient exposure of the cells to lower temperature. This is consistent with mediation by a phosphorylation event. However, the requirement for an extended (greater than 15 min) preincubation period when using minimal kinase activation suggests that this phenomenon is more complicated than a simple bimolecular phosphorylation event and likely includes a series of events such as translocation of substrates and/or enzymes involved.
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PMID:Complex role of protein kinase C in mediating the supramaximal inhibition of pancreatic secretion observed with cholecystokinin. 152 Mar 40

We have investigated the effect of cholecystokinin-octapeptide (CCK-8) on [Ca2+]i and protein kinase C (PKC) activity in Jurkat T-cells. CCK-8 produced a transient [Ca2+]i increase in the presence of extracellular Ca2+. While CCKB receptor antagonist L-365,260 abolished the elevation of [Ca2+]i, CCKA receptor antagonist L-364,718 was without effect. Moreover, the dihydropyridine calcium channel blocker nitrendipine was shown to block the observed calcium response. Results suggest that the calcium effect is caused by an interaction of CCK-8 with CCKB binding sites and an influx of external Ca2+ via dihydropyridine sensitive calcium channels might serve as a source for the increased [Ca2+]i. Because CCK-8 induced no PKC activation CCKB receptor mediated rise of intracellular calcium seems not to include activation of phospholipase C.
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PMID:CCKB receptor stimulation mediates [Ca2+]i increase but no PKC activation in Jurkat T-cells. 152 Aug 57

Stimulation of chief cells with carbachol or cholecystokinin (CCK) results in the production of inositol trisphosphate (IP3) and diacylglycerol (DAG). Although IP3 increases cell calcium concentration, thereby stimulating pepsinogen secretion, the role of DAG and its target, protein kinase C (PKC), is less clear. To examine the relation between the cellular distribution of PKC activity and pepsinogen secretion, we determined PKC activity in cytosolic and membrane fractions from dispersed chief cells from guinea pig stomach. To validate our assay, we studied the actions of the phorbol ester PMA. PMA caused a rapid, dose-dependent, 6-fold increase in pepsinogen secretion and membrane-associated PKC activity. Similarly, dose-response curves for pepsinogen secretion and the increase in membrane-associated PKC activity induced by a membrane-permeant DAG (1-oleoyl-2-acetylglycerol) were superimposable. In contrast, CCK (0.1 nM to 1.0 microM) and carbachol (0.1 microM to 1.0 mM) caused a 4-fold increase in pepsinogen secretion, but did not alter the distribution of PKC activity. These results indicate that in gastric chief cells, PMA- and DAG-induced pepsinogen secretion is accompanied by increased membrane-associated PKC activity. However, the cellular distribution of PKC activity is not altered by CCK or carbachol.
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PMID:Cellular distribution of gastric chief cell protein kinase C activity: differential effects of diacylglycerol, phorbol esters, carbachol, and cholecystokinin. 158 72

Agents like carbachol and cholecystokinin (CCK), that activate chief cell phosphoinositidase C, thereby increasing cell calcium concentration, increase cAMP levels in cholera toxin-treated, but not control, gastric chief cells. In the present study, we found that phorbol esters, like PMA, that activate protein kinase C, also cause augmentation of chief cell cAMP levels. The maximal effect with PMA (100 nM) was about 50% of the maximal response with CCK (10 nM) or carbachol (100 microM). Because protein kinase C is a calcium-dependent enzyme, we examined the effect of modulating cell calcium levels with the ionophore A23187. The ionophore alone caused a dose-dependent augmentation of cAMP levels. Adding 100 nM PMA caused an additive response, such that a maximal cAMP response, equal to that seen with 100 microM carbachol, was observed with 30 nM A23187. Carbachol-, A23187-, and PMA-induced augmentation of cAMP levels was progressively reduced by increasing concentrations of calmidazolium, a calmodulin inhibitor. Combination of phorbol esters that activate protein kinase C with ionophores that increase cell calcium mimics the actions of CCK and carbachol on cAMP levels in cholera toxin-treated chief cells.
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PMID:Actions of phorbol esters on levels of cAMP in cholera toxin-treated chief cells from guinea pig stomach. 159 Dec 73

First incubating guinea pig pancreatic acini with carbachol reduced the subsequent stimulation of amylase release caused by carbachol, cholecystokinin octapeptide (CCK-8), and bombesin but not that caused by vasoactive intestinal peptide, substance P, 8-bromoadenosine 3',5'-cyclic monophosphate, A23187, or 12-O-tetradecanoylphorbol-13-acetate. Carbachol also reduced the subsequent binding of N-[3H]methylscopolamine, 125I-CCK-8, and 125I-[Tyr4]bombesin. Pancreatic acini possess a high-affinity class of cholinergic receptors and a low-affinity cholinergic receptors appears to produce the reduction in carbachol-stimulated amylase release and binding of N-[3H]methylscopolamine. First incubating acini with carbachol caused a complete loss of high-affinity cholinergic receptors with no change in the number or affinity of low-affinity cholinergic receptors. Carbachol occupation of low-affinity cholinergic receptors appears to produce the reduction in CCK-8- and bombesin-stimulated amylase release and in binding of 125I-CCK-8 and 125I-[Tyr4]bombesin. Acini possess two classes of CCK receptors. One class has a high affinity for CCK-8; the other class has a low affinity for CCK-8. First incubating acini with carbachol caused a 60% decrease in the number of high-affinity CCK receptors with no change in the number of low-affinity receptors or the affinities of either class of receptors for CCK-8. Acini possess a single class of bombesin receptors, and first incubating acini with carbachol caused a 40% decrease in the number of bombesin receptors with no change in their affinity for bombesin. 12-O-tetradecanoyl phorbol-13-acetate reproduced the action of carbachol on binding of N-[3H]methylscopolamine and 125I-CCK-8 but not on binding of 125I-[Tyr4]bombesin, suggesting that carbachol activation of protein kinase C may in some way mediate the effect of carbachol on receptors for carbachol and those for CCK but not that on receptors for bombesin.
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PMID:Carbachol desensitizes pancreatic enzyme secretion by downregulation of receptors. 168 17


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