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)

Protein kinase C was purified 6,900-fold from rabbit pancreas with a total yield of 15% by a procedure involving ammonium sulfate fractionation, diethyl aminoethyl ion exchange chromatography, hydroxylapatite chromatography, and finally protamine-agarose affinity chromatography. After these purification steps the protein kinase C preparation contained two major protein bands as judged by silver staining after SDS-polyacrylamide gel electrophoresis: 80 and 69-kDa bands. Monoclonal antibodies directed against bovine brain protein kinase C (alpha- and beta-subtype) recognized only the 80-kDa band. On the other hand, both the 80 and 69-kDa proteins were recognized by a polyclonal monospecific antibody directed against rat brain protein kinase C. Analysis of rabbit pancreas protein kinase C subtypes by means of hydroxylapatite chromatography showed the presence of the III (alpha) subtype as the major subtype. The enzyme depended absolutely on the presence of both phosphatidylserine and Ca2+ for its activity, with apparent Ka values of 3.1 micrograms/ml and 247 microM for phosphatidylserine and Ca2+, respectively. When dioctanoylglycerol or the phorbol ester 12-O-tetradecanoyl-phorbol 13 acetate (TPA) was present, the Ka value for Ca2+ decreased to 10 and 18 microM, respectively. In the presence of the phorbol ester, pancreatic protein kinase C could be activated without added Ca2+. The enzyme also required Mg2+ for its activity. The Ka value was 3.6 mM and maximal activity was reached at 10 mM Mg2+. Pancreatic protein kinase C activity showed a broad pH dependence, with optimal activity at pH 6.75. The Km value for ATP and for histone-H1 was 8.5 microM and 20.4 micrograms/ml, respectively. The present study shows that the kinetic properties of protein kinase C purified from rabbit pancreas closely resemble those found in other tissues.
Pancreas 1992
PMID:Purification and characterization of rabbit pancreas protein kinase C. 155 44

Pretreatment of rat pancreatic acini with phorbol 12-myristate, 13-acetate (PMA), a protein kinase C (PK-C) activator, caused the desensitization of carbamylcholine (CBC)-induced amylase release in a concentration- and time-dependent fashion. The less potent phorbol-12, 13-dibutyrate (PDBu) also provoked a desensitization, but the inactive 4-alpha-phorbol-12,13-didecanoate had no effect. PMA or PDBu also significantly reduced subsequent amylase release induced by caerulein or secretin in contrast to CBC, which only reduced amylase release induced by CBC or secretin. Preincubation of acini with PMA did not lead to a decrease in PMA or A23187-stimulated amylase release. A 3 h resting period did not restore the desensitization induced by PMA or PDBu. Pretreatment with PMA did not cause changes in muscarinic receptor high- and low-affinity populations as observed with CBC pretreatment. The PK-C inhibitor H-7 completely prevented the desensitization induced by PDBu but not that induced by CBC. TMB-8, another PK-C inhibitor, also completely prevented the desensitization induced by PDBu but only partially that induced by CBC. These results suggest that phorbol esters can induce desensitization of muscarinic receptor-stimulated amylase release by a different mechanism than that involved in muscarinic agonist-induced desensitization.
Pancreas 1990
PMID:Carbamylcholine and phorbol esters desensitize muscarinic receptors by different mechanisms in rat pancreatic acini. 168 90

Pretreatment of rat pancreatic acini with 12-O-tetradecanoyl-phorbol-13-acetate (TPA) for 5 or 10 min reduced cytosolic free calcium and amylase secretion stimulated by submaximal concentration (10(-6) M) of carbachol in a dose-dependent manner. 10(-7) M TPA inhibited initial amylase secretion and had no effect on sustained secretion stimulated by 10(-6) M carbachol. 1-(5-Isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H7), a protein kinase C inhibitor, partially blocked these inhibitory effects of TPA. Cytosolic calcium concentration and initial amylase secretion were recovered with 10-100 microM H7 in TPA-treated acini. H7 was more effective than N-(2-guanidinoethyl)-5-isoquinoline-sulfonamide hydrochloride in increasing cytosolic free calcium in TPA-treated acini. TPA completely blocked an increase in cytosolic free calcium by 10 mM NaF. These findings indicated that TPA caused the inhibitory effects by means of activating protein kinase C, and suggested that protein kinase C might regulate enzyme secretion by inhibiting calcium mobilization, probably through a postreceptor-mediated mechanism.
Pancreas 1991 Jan
PMID:Effects of H7 and staurosporine on cytosolic free calcium and amylase secretion in rat pancreatic acini. 170 30

Stimulation of intact rat pancreatic acini with cholecystokinin (CCK) enhances the phosphorylation of the ribosomal protein S6 in a dose-dependent manner with half maximal stimulation at 40 pM and maximal stimulation at 1 nM CCK octapeptide. Soluble cellular extracts contained S6 kinase activity assayed using purified rat pancreatic ribosomes as substrate. Stimulation by CCK of S6 kinase was concentration dependent, being half maximal at 50 pM and maximal at 1 nM CCK. The phorbol ester 12-O-tetradecanoyl-phorbol 13-acetate (TPA), an activator of protein kinase C, also increased both S6 phosphorylation in intact acini and soluble S6 kinase activity. In order to determine whether S6 kinase mediated S6 phosphorylation following CCK treatment of acini, two-dimensional phosphopeptide analysis was performed for S6 proteins phosphorylated under various conditions. These data suggest that a specific soluble S6 kinase, the activation of which appears to be directly or indirectly mediated by protein kinase C, is the functional enzyme in intact acini that mediates the action of CCK to increase S6 phosphorylation and may be involved in increased protein synthesis in pancreatic acini treated with CCK.
Pancreas 1990 Nov
PMID:Cholecystokinin stimulates a specific ribosomal S6 kinase in rat pancreatic acini. 228 Oct 80

Quercetin (Q) has been shown to inhibit Ca2+-dependent processes. The present study evaluates the effect of Q on amylase release stimulated by various agonists in dispersed rat pancreatic acini. Q inhibited amylase release stimulated by an optimal concentration of carbachol. The inhibition was dependent on Q concentration. Preincubation with Q was not necessary. Maximal inhibition (up to 60% of control) was reached at 50 microM of Q and was completely reversible. Full responsiveness of the acini to agonist stimulation was reestablished as early as 5 min upon the removal of Q. At 50 microM, Q inhibited stimulated amylase release by optimal concentrations of tetradecanoylphorbol-13-acetate (TPA) (10(-6) M), A23187 (3 x 10(-6) M), cholecystokinin C-terminal octapeptide (CCK-OP) (10(-9) M) and carbachol (3 x 10(-6) M), but not by vasoactive intestinal polypeptide (VIP) (3 x 10(-7) M). Instead, Q promoted amylase release stimulated by VIP. The inhibition of amylase secretion by Q occurred only at near optimal, optimal, and supraoptimal concentrations of TPA, A23187, CCK-OP, and carbachol. The potentiation effect of Q on VIP-stimulated amylase secretion was, however, seen at all concentrations of VIP used (10(-8) to 10(-6) M). Quercetin also inhibited protein kinase C activity from rat pancreas in a dose-dependent manner. Maximal inhibition (approximately 85%) was seen at 100 microM of Q. These results provide further support that the intermediary steps for stimulated enzyme secretion in pancreatic acini by TPA, A23187, CCK-OP, and carbachol involve calmodulin and/or protein kinase C, whereas VIP does not.(ABSTRACT TRUNCATED AT 250 WORDS)
Pancreas 1988
PMID:Selectivity of quercetin inhibition on stimulated amylase release in rat pancreatic acini. 245 93

Vasoactive intestinal peptide (VIP) or 12-O-tetradecanoylphorbol-13-acetate (TPA) individually stimulated amylase release in dispersed rat pancreatic acini. Pretreatment of acini with TPA (10(-6) M) for 5 min at 37 degrees C potentiated their subsequent response to stimulation by VIP at a dose range of 10(-8)-10(-6) M in that the treated pancreatic acini released more amylase than could be accounted for by the additive effects of VIP or TPA acting individually. This potentiation effect of TPA was still evident when isobutyl methylxanthine was given together with VIP. Further, the maximal' dose-response curve to VIP shifted 2 log units to the left (3 x 10(-9) versus 3 x 10(-7) M). The TPA preincubation was found also to potentiate VIP-stimulated net increases in intracellular cyclic AMP (cAMP) levels. A close correlation existed between the net releases of amylase and the net increases in intracellular cAMP levels (r = 0.97). This suggested that TPA potentiated the response of rat pancreatic acini to VIP by modulating the cAMP system. The TPA as a potent activator of protein kinase C may act as a modulator of the adenylate cylase-cAMP system in rat pancreatic acini.
Pancreas 1989
PMID:Phorbol ester potentiates VIP-stimulated amylase release in rat pancreatic acini. 247 14

The human fetal pancreas, like the adult pancreas, releases insulin in response to agents that increase intracellular levels of calcium and cyclic AMP. It differs from the adult pancreas in that glucose causes either minimal or no insulin secretion from it. Whether activation of protein kinase C will cause release of insulin from this immature cell, as it does from the adult pancreas, is unknown. This was the phenomenon examined in the experiments below. Activators of protein kinase C, 1.3 microM 12-O-tetradecanoylphorbol-13-acetate (TPA) and 25.1 microM 1-oleoyl-2-acetylglycerol, caused significant release of insulin from cultured explants of human fetal pancreas. Lower concentrations of TPA--0.65 microM or less--had no such effect. Agents that are known to inhibit protein kinase C, 100 microM 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine, 2 mM polymyxin B, and 1 mM dibucaine, caused abolition of the insulinogenic effect of 1.3 microM TPA. Glucose, at 2.8, 5, and 10 mM, also inhibited the positive effect of TPA. However, when the concentration of glucose was increased to 20 or 30 mM, stimulation of insulin secretion returned to levels achieved with TPA alone. These levels were significantly higher than the minimal response achieved with 20 mM glucose. Such data support the involvement of protein kinase C activation in insulin secretion from the human fetal pancreas. It is postulated that this involvement may occur physiologically.
Pancreas 1988
PMID:Activators of protein kinase C stimulate insulin secretion from the human fetal pancreas. 306 76

We previously demonstrated that the supramaximally effective concentrations of caerulein caused marked changes in the apical cytoskeleton of the rat pancreatic acinar cell. These changes included ablation of microvilli, the terminal actin web, and intermediate filament bands. The present study was designed to elucidate part of the intracellular signalling mechanism mediating these changes. For these studies we used a cholecystokinin (CCK) analogue, CCK-JMV-180, that has been previously demonstrated not to inhibit enzyme secretion and to prevent the inhibition caused by caerulein. We investigated the effects of CCK-JMV-180 alone and in combination with supramaximal concentrations of caerulein on the morphology of the apical structures, on 1,2-diacylglycerol production (a measure of phospholipase C activity), and on amylase secretion in rat pancreatic acini. Supramaximally effective concentrations of caerulein caused inhibition of enzyme secretion. CCK-JMV-180 had no effect on the ultrastructure of the apical region of the acinar cell and it prevented the ablation of apical cytoskeleton induced by a supramaximal concentration of caerulein (10 nM). CCK-JMV-180 inhibited the increase in 1,2-diacylglycerol formation and the inhibition of amylase release caused by 10 nM caerulein. Mimicking the effect of 1,2-diacylglycerol on activation of protein kinase C with phorbol 12-myristate 13-acetate and reproducing changes in [Ca2+]i caused by 10 nM caerulein with 100 nM bombesin did not alter the apical cytoskeleton. These results suggest that the cytoskeletal changes observed with inhibitory concentrations of caerulein are caused by the phospholipase C effects of caerulein on membrane phospholipids.
Pancreas 1993 Sep
PMID:Cholecystokinin JMV-180 and caerulein effects on the pancreatic acinar cell cytoskeleton. 750 12

The involvement of phospholipase D (PLD) in phosphatidylcholine hydrolysis by epidermal (EGF), insulin-like (IGF-I), and basic fibroblast (bFGF) growth factors was investigated in rat pancreatic acini. Acini were prelabeled with [3H]myristic acid which is mostly incorporated into phosphatidylcholine. EGF, IGF-I, and bFGF caused significant and dose-dependent increases in [3H]phosphatidic acid (PA) accumulation in the presence of propranolol, a phosphatidic acid phosphohydrolase inhibitor. The effects of EGF and IGF-I were significant after 5, 15, and 30 min of stimulation, whereas that of bFGF was evident only at 30 min. PA production in response to all three factors was dose dependent with maximal responses to EGF at 25 nM, to IGF-I at 16.5 nM, and to bFGF at 50 pM. Preincubation of acini with staurosporine, a protein kinase C and tyrosine kinase inhibitor, totally inhibited PA production by the three factors. Similarly, acini preincubation with genistein, a specific tyrosine kinase inhibitor, also neutralized the influence of the three factors on PA accumulation. In the presence of 1% ethanol, EGF, IGF-I, and bFGF caused significant phosphatidylethanol production after 20 min of incubation, thus confirming the involvement of PLD in PA production. These data present for the first time the description of a new signaling pathway through which EGF, IGF-I, and bFGF may operate to induce some of their specific effects on the pancreas in association with these growth factor receptors' tyrosine kinase activity.
Pancreas 1995 Jan
PMID:Activation of pancreatic acinar cell phospholipase D by epidermal, insulin-like, and basic fibroblast growth factors involves tyrosine kinase. 789 61

The effect of salicylate and nonsalicylate antiinflammatory drugs and prostaglandins (PGs) on pancreatic exocrine secretion are controversial. We studied the effect of aspirin (ASA) on secretin- and cholecystokinin (CCK)- or meal-stimulated pancreatic secretion. The interrelation between ASA, PG, and pancreatic exocrine secretion was also investigated. Conscious rats with chronic duodenal, pancreatic, and biliary cannulas received secretin (5 pmol/kg/h, i.v.) and CCK (56 pmol/kg/h) or a meal with administration of cimetidine (20 mg/kg/h, i.v.), ASA (1.2, 12, or 60 mumol/h, i.v.), Salicylic acid (SA) (1.2, 12, or 60 mumol/h, i.v.), prostaglandin E2 (PGE2) (10 micrograms/kg/h), or indomethacin (2 mg/kg) was given, respectively. Pancreatic flow volume, bicarbonate, and protein were determined every 15 min. An inhibitor, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7) (36 micrograms/kg/h) and an activator, phorbol ester (12-O-tetradecanoyl-phorbol 13-acetate, TPA) (100 ng/kg/h) were used for evaluation of the role of protein kinase C on basal and secretagogue-stimulated pancreatic secretion. ASA, but not SA inhibited the secretin- and CCK-stimulated pancreatic secretion including volume, bicarbonate, and protein in a dose-dependent manner without affecting basal pancreatic secretion. ASA and indomethacin suppressed meal-stimulated pancreatic secretion up to 83.8%. PGE2 significantly inhibited the secretin- and CCK-stimulated pancreatic secretion which was further suppressed by the concomitant ASA infusion. Modulation of protein kinase C failed to affect pancreatic secretion. The data indicate that ASA inhibits both secretin- and CCK-stimulated pancreatic secretion by a mechanism independent of prostaglandin biosynthesis inhibition.
Pancreas 1995 Jan
PMID:Aspirin inhibits secretagogue-stimulated and postprandial pancreatic exocrine secretion in conscious rats. 789 65


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