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 enzymes cAMP-dependent protein kinase (PKA) and protein kinase C (PKC) regulate the activity of cardiac ion channel proteins. In this study the whole-cell arrangement of the patch clamp technique was used to examine the effect of NaI on PKA-stimulated Cl- and Ca2+ channels in isolated guinea pig ventricular myocytes. Cl- currents (ICl) activated either by the beta-adrenergic agonist isoproterenol or the membrane-soluble cAMP analogue, 8-chlorphenylthio (8-CPT) cAMP, were greatly reduced in amplitude after substitution of an external solution containing 140 mM NaCl with a solution containing 140 mM NaI. This reduction was accompanied by a shift of -7 mV in the reversal potential (Erev) for ICl and could be reversed upon return to the NaCl external solution. Inhibition of ICl by NaI occurred in a concentration-dependent manner and was more pronounced for inward ICl (IC50 = 19 mM at -60 mV) than for outward ICl (IC50 = 60 mM at +60 mV). In contrast to ICl activated by PKA, ICl activated by PKC was slightly augmented in the presence of NaI and the Erev was found to shift by -15 mV. Based on these data, the relative permeability of I- to Cl- (PI/PCl) for this channel was calculated to be 1.79. NaI produced no change in the amplitude of inward calcium currents (ICa) recorded under basal conditions, but strongly inhibited ICa augmented by isoproterenol and 8-CPT cAMP, and during dialysis of cells with the catalytic subunit of PKA (CS). The in vitro incorporation of [gamma-32P]ATP into histone IIA and Kemptide, measured in the presence of PKA and cAMP, was not significantly different in assay mixtures containing salts of Cl- and I-. However, the ability of isoproterenol to augment basal ICa in whole-cell experiments was attenuated when experiments were carried out entirely in NaI external solution. Thus, the reduction in ICl and ICa observed in this study may result from a direct effect of I- on the phosphorylation/dephosphorylation of cardiac ion channel proteins or associated regulatory proteins.
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PMID:Inhibition of heart calcium and chloride currents by sodium iodide. Specific attenuation in cAMP-dependent protein kinase-mediated regulation. 128 46

Mefloquine (alpha-(2-piperidyl)-2,8-bis(trifluoromethyl)-4-quinolinemethanol) , an antimalarial drug, has been shown to inhibit human neutrophil functions, particularly oxygen-dependent bactericidal activity. Since calcium- and phospholipid-dependent protein kinase C (PKC) has a central role in the regulation of this function, we hypothesized that its activity might be altered by mefloquine. We found that mefloquine directly inhibited PKC in a dose-dependent manner, with an IC50 of 45 microM. This inhibition appeared to be non-competitive with respect to ATP, histone and phosphatidylserine. In addition, mefloquine inhibited the binding of [3H]phorbol 12,13 dibutyrate to PKC, indicating that it interacts with the regulatory domain of PKC. By contrast, mefloquine had little or no effect on neutrophil cAMP-dependent protein kinase or its catalytic subunit. Phorbol myristate acetate-induced protein phosphorylation in intact neutrophils was also inhibited by preincubation with mefloquine at concentrations similar to those inhibiting superoxide anion production. These data suggest that inhibition of neutrophil functions by mefloquine may be due to the inhibition of cellular PKC and that mefloquine could have further biological effects in situations in which PKC is involved.
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PMID:Inhibition of human neutrophil protein kinase C activity by the antimalarial drug mefloquine. 131 82

Microtubule-associated protein 2 (MAP2) kinase has been isolated and characterized from rat brain. The enzyme has an apparent M(r) of approximately 42,000 and its pI is 4.9. MAP2 was the preferred substrate, but it also phosphorylated myelin basic protein (MBP), histone V-S, tubulin and the PC12 protein substrate pp250. The enzyme is distinct from protein kinase C, cAMP-dependent kinase and the calcium/calmodulin-dependent kinases, as specific inhibitors of these kinases did not affect MAP2 phosphorylation. The addition of the relatively non-specific protein kinase inhibitor H7 (20 microM) had a modest inhibitory effect. The enzyme was active in both 5 mM Mn2+ and Mg2+, and displayed Kms for MAP2, MBP, and ATP of 56 nM, 254 nM, and 4 microM, respectively. This enzyme, which represents a low abundance protein in whole brain, is analogous to the MAP2 kinase observed in growth factor-stimulated cell lines.
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PMID:Isolation and characterization of microtubule-associated protein 2 (MAP2) kinase from rat brain. 132 16

Propranolol, a beta-adrenergic receptor antagonist, also inhibits phosphatidate phosphohydrolase, the enzyme that converts phosphatidic acid into diacylglycerol. This latter effect has prompted recent use of propranolol in studies examining the importance of diacylglycerol and phosphatidic acid in cellular signalling events. Here, we show that propranolol is also an inhibitor of protein kinase C. At concentrations greater than or equal to 20 microM, propranolol reduced [3H]phorbol dibutyrate binding (IC50 = 200 microM) and phorbol myristate acetate-stimulated superoxide anion release (IC50 = 130 microM) in human neutrophils. Scatchard analysis showed that propranolol lowers the number of phorbol diester binding sites without significantly affecting their affinity. In vitro kinetic analysis, performed in a mixed micellar assay with protein kinase C purified from human neutrophils, suggested a competitive inhibition of propranolol with the cofactor phosphatidylserine. Complex kinetic patterns were observed with respect to diacylglycerol and ATP, approximating competitive and noncompetitive inhibition, respectively. Taken together, these results suggest that the drug interacts at the level of the regulatory domain of the enzyme. Fifty % inhibition occurred at approximately 150 microM propranolol. Similar levels of inhibition were obtained using exogenous (histone) and endogenous (p47-phox, a NADPH oxidase component) substrates. Protein kinase C-alpha and protein kinase C-beta, two protein kinase C isozymes present in human neutrophils, were inhibited by propranolol in a comparable manner. In the range of concentrations tested (30-1000 microM), neither cAMP-dependent protein kinase nor neutrophil protein tyrosine kinases were affected. The racemic form of propranolol and the (+) and the (-) stereoisomers were equally active, and other beta-adrenergic receptor antagonists (pindolol) and agonists (isoproterenol) were inactive. This suggests that the inhibitory action of propranolol on protein kinase C is related to the amphipathic nature of the drug rather than to its beta-adrenergic receptor blocking ability. Analogs of propranolol were synthesized and found to be more potent protein kinase C inhibitors, with IC50 values in the 10-20 microM range. We conclude that the ability of propranolol to inhibit both protein kinase C and PA phosphohydrolase complicates interpretation of results when this drug is used in signal transduction studies. In addition, propranolol may be a useful prototype for the synthesis of new protein kinase C inhibitors.
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PMID:Propranolol, a phosphatidate phosphohydrolase inhibitor, also inhibits protein kinase C. 132

Endogenous inhibitor of protein kinases (type II inhibitor, GABA-modulin) blocks the phosphorylation catalyzed by cAMP-dependent protein kinase (PKA) and protein kinase C (PKC) as a competitive inhibitor of substrate proteins when histone is used as a substrate. Moreover, type II inhibitor blocks the phosphorylation of endogenous membrane proteins by PKC. Stimulation of alpha 1-adrenoceptors induced rapid redistribution of PKC from cytosol to membrane fraction which lasted at least 3 h, accompanied by rapid and short-lasting translocation of type II inhibitor from membrane to cytosol fraction. The cytosol content of type II inhibitor reached maximal level 10 and 20 min and became normal again 40 min after i.p. administration of methoxamine. The above actions of methoxamine were completely blocked by pretreatment with prazosin. It seems that short-lasting redistribution of type II inhibitor from membrane to cytosol fraction allows the effective phosphorylation of membrane proteins by PKC after stimulation of alpha 1-adrenoceptors.
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PMID:Regulation of protein kinase C after stimulation of alpha 1-adrenoceptors in rat hippocampus. 136 26

It has been suggested that phosphorylation of myelin basic protein (MBP) in CNS is catalyzed by protein kinase C (PKC). In order to demonstrate that PKC in the myelin phosphorylates MBP, PKC was partially purified from rat CNS myelin by solubilization with Triton X-100 followed by a DEAE-cellulose column. MBP and histone III-S were phosphorylated in the presence of Ca2+ and phospholipid by rat myelin PKC. High voltage electrophoresis revealed that the phosphoamino acids in MBP by this kinase was serine residue, which is known to be the amino acid phosphorylated by PKC. The activity of PKC extracted from myelin was inhibited by the addition of psychosine to the incubation mixture. To confirm the presence of PKC molecule and to identify the isoform of PKC in the myelin, the solubilized myelin fraction was applied on SDS-PAGE, transferred to a nitrocellulose sheet and stained with anti-PKC monoclonal antibodies. Rat CNS myelin contained the PKC of about 80 kDa (intact PKC), and no proteolytic fragments were observed. PKC isozymes in myelin were type II and III. A developmental study from 14 to 42 postnatal days showed that PKC activity in CNS myelin seemed to parallel the deposition of myelin protein.
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PMID:Protein kinase C in rat brain myelin. 138 Jun 75

Activation of protein kinase C (PKC) by phorbol 12-myristate 13-acetate (PMA) was compared with calcium/phosphatidylserine (Ca/PS). The substrate specificity of PKC was more limited with PS/PMA. Substrates could be divided into three overlapping groups according to their relative level of phosphorylation: C1, relatively preferred substrates with Ca/PS, included dephosphin, histone, and peptide GS1-10. C2, relatively preferred with PS/PMA, included myelin basic protein and MARCKS. C3, substrates independent of activators. PS/PMA altered the Vmax of PKC for substrate, and decreased the Km for Mg2+. Differential substrate phosphorylation by PS/PMA also occurred for PKC isozymes resolved by hydroxylapatite chromatography and was most dramatic for PKC-alpha, which could no longer phosphorylate histone or GS1-12. Differential activities of PKC were also observed in synaptosol and in intact synaptosomes where PMA stimulated phosphorylation of MARCKS, but not dephosphin. It was further shown that dephosphin was indeed a substrate of PKC in the intact synaptosomes by use of a repolarization-dependent dephosphin phosphorylation assay. The differential PKC activities could also be distinguished by inhibitors. H-7 was equipotent, palmitoylcarnitine did not inhibit in vitro C2 phosphorylation, but inhibited dephosphin in intact synaptosomes, and sphingosine did not inhibit C1 substrates and was without effect on dephosphin in intact synaptosomes. Therefore PS/PMA alters or limits the substrate specificity of PKC, leading to a differential substrate phosphorylation in vitro and in intact synaptosomes and differential inhibitor sensitivity. The pattern of protein phosphorylation observed after PKC activation in intact cells will therefore be dependent upon the activator.
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PMID:Differential stimulation of protein kinase C activity by phorbol ester or calcium/phosphatidylserine in vitro and in intact synaptosomes. 140 Apr 74

The changes of kinetic characteristics (apparent Km and Vmax) of the Ca2+ phospholipid-dependent protein kinase (protein kinase C) from the rat liver for substrates ATP and histone Hl 2 and 24 hours after total X-ray irradiation have been established. The obtained results evidence for the important role of these changes in early radiosensitivity of protein kinase C.
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PMID:[Kinetic characteristics of Ca2+-phospholipid-dependent protein kinase from the rat liver in the early stages after x-ray irradiation]. 141 26

The aim was to examine systematically the potencies of protein kinase C inhibitors as a function of the kinase activator. Protein kinase C is activated by at least four stimulators: calcium plus phosphatidylserine (Ca/PS), phorbol 12-myristate 13-acetate plus PS (PS/PMA), arachidonic acid plus calcium (Ca/AA) and the synthetic peptide activator PCK530-558. With histone or GS1-12 as substrates, protein kinase C was maximally activated by Ca/PS, or to maxima of 62%, 89% or 82% with PS/PMA, Ca/AA or PKC530-558, respectively. One group of inhibitors, including H-7 and staurosporine, were equipotent, regardless of the activator. All other inhibitors showed variable selectivity, dependent upon the activator. A second group of inhibitors, including sphingosine and lipophosphoglycan, were eight or 200 times more potent for inhibition of PS/PMA-stimulated activity (relative to Ca/PS) and a third group, including retinal and palmitoylcarnitine, were 14 or 262 times more potent towards Ca/PS-stimulated activity. A final group (rhodamine 6G) was nine times more potent when Ca/AA was the activator. Similar results were obtained using the endogenous substrates dephosphin or MARCKS in synaptosol. Phosphorylation of MARCKS was stimulated by PS/PMA or Ca/PS, while phosphorylation of dephosphin was stimulated only by Ca/PS. The phosphorylation of either by Ca/PS-activated kinase was nine times more potently inhibited by palmitoylcarnitine, while phosphorylation of MARCKS by PS/PMA-activated kinase was 10 times more potently inhibited by sphingosine. H-7 inhibited both at similar concentrations. A model encompasses these differences in potency if the inhibitors are divided into four groups (A-D) according to their competitive inhibition with the appropriate activator or at the active site. The non-selective inhibitors interact at the active sites of protein kinase C (group A). The compounds which preferentially inhibit PS/PMA-activated kinase (sphingosine and lipophosphoglycan) are competitive inhibitors of PMA and 1,2-diacylglycerol (group B), those selective for Ca/PS-activated kinase (palmitoylcarnitine and retinal) are competitive with PS (group C) and those selective for Ca-AA activation (rhodamine 6G) are likely to be competitive with fatty acid (group D). Therefore, the effectiveness of protein kinase C inhibitors is dependent upon the activator employed.
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PMID:Potencies of protein kinase C inhibitors are dependent on the activators used to stimulate the enzyme. 141 56

Using a PKC-epsilon cDNA probe a cDNA for PKC-eta has been cloned from a rat lung cDNA library. When expressed in COS cells, rat PKC-eta appeared as an 84 kDa protein. PKC-eta expressed in COS cells, was solubilized by 1% Triton X-100 and purified away from the endogenous PKC-alpha by ammonium sulphate fractionation. The activity of this PKC-eta preparation was characterized with respect to cofactor dependence and substrate specificity. Various PKC pseudosubstrate peptides are phosphorylated by PKC-eta in a phospholipid and TPA-dependent but calcium-independent manner. The polypeptide histone IIIS is a poor substrate.
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PMID:Biochemical properties of rat protein kinase C-eta expressed in COS cells. 142 52


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