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 substrate specificity determinants of protein kinase C are probed using synthetic peptides encompassing the major phosphorylation site serine 115 in bovine MBP. The results indicate that basic residues arginine 107 and 113 N-terminal to the phosphorylation site are essential for the substrate activity of the peptides. Substitutions of these basic residues by alanine cause a marked decrease in their substrate activity and the resulting peptide analogs become specific and rather potent inhibitors of protein kinase C. Leukemic cells are particularly abundant in protein kinase C and its substrate proteins, and the enzyme system has been shown to play a key role in cell growth. The agents that stimulate protein kinase C include tumor promoting phorbol esters (such as TPA) and mezerein, and the putative second messenger diacylglycerol. Many antineoplastic agents, on the other hand, inhibit the enzyme which include adriamycin, tamoxifen, alkyl-lysophospholipid, selenium, retinal and lipoidal amine CP-46, 665-1. Immunocytochemical studies of protein kinase C in leukemic cells indicate that it is localized in the plasma membrane, cytoplasm, nucleus and Golgi apparatus, and the subcellular distribution of the enzyme might be related to the phases of the cell cycle. TPA induces translocation of the enzyme to plasma membrane, suggesting an additional mode of action for the tumor promotor.
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PMID:Phospholipid/calcium-dependent protein kinase (protein kinase C) system: a major site of bioregulation. 243 6

The activities of Ca2+.phospholipid-dependent protein kinase (protein kinase C) in rat salivary gland were assayed using synthetic peptide syntide-2(Pro-Leu-Ala-Arg-Thr-Leu-Ser-Val-Ala-Gly-Leu-Pro-Gly-Lys- Lys) as substrate. Levels of the protein kinase C were less than 0.05 units/g in the parotid and submandibular glands. The protein kinase C inhibitor, H-7, inhibited amylase secretion from rat parotid gland stimulated by PMA or the combination of phosphatidylserine and 1,2-diolein. The results supported the hypothesis of the secretory mechanism that protein kinase C mediates amylase secretion in rat parotid glands.
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PMID:The role of protein kinase C on amylase secretion from rat parotid gland. 244 8

Little is known about the important cellular substrates for protein kinase C and their potential roles in mediating protein kinase C-dependent processes. We evaluated the protein kinase C phosphorylation sites in a major cellular substrate for the kinase, a protein of apparent Mr 80,000 in bovine and 60,000 in chicken tissues; we have recently determined the primary sequences of these proteins and tentatively named them the myristoylated alanine-rich C kinase substrates. The proteins were purified to apparent homogeneity from bovine and chicken brains, phosphorylated with protein kinase C, digested with trypsin, and the phosphopeptides purified and sequenced. Four distinct phosphopeptides were identified from both the bovine and chicken proteins. Two of the phosphorylated serines were contained in the repeated motif FSFKK, one in the sequence LSGF, and one in the sequence SFK. All four sites were contained within a basic domain of 25 amino acids which was identical in the chicken and bovine proteins. All of the sites phosphorylated in the cell-free system appeared to be phosphorylated in intact cells; an additional site may have been present in the proteins from intact cells. The identity of the phosphorylation site domains from two proteins of overall 65% amino acid sequence identity suggests a potential role for this domain in the physiological function of the myristoylated alanine-rich C kinase substrate proteins.
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PMID:Characterization of the phosphorylation sites in the chicken and bovine myristoylated alanine-rich C kinase substrate protein, a prominent cellular substrate for protein kinase C. 247 66

The product of the c-src proto-oncogene, pp60c-src, is phosphorylated at Ser-17 by cyclic AMP-dependent protein kinase A and at Ser-12 by calcium-phospholipid-dependent protein kinase C (when stimulated by 12-O-tetradecanoyl phorbol acetate). We tested the effects of Ser----Ala and Ser----Glu mutations at these sites in pp60c-src and in pp60c-src(F527) (a mutant whose transforming activities are enhanced by Tyr-527----Phe mutation) by transfecting single-, double-, and triple-mutant src expression plasmids into NIH 3T3 cells. Tryptic phosphopeptide analyses of the mutant proteins confirmed prior biochemical identifications of the phosphorylation sites and showed that neither separate nor coordinate mutations at Ser-12 and Ser-17 affected Tyr-416, Tyr-527, or Ser-48 phosphorylation or prevented mitosis-specific phosphorylations of either pp60c-src or pp60c-src(F527). Ser-12 mutation did not affect phosphorylation of the Ser-17-containing peptide, but mutation of Ser-17 significantly increased phosphorylation at Ser-12. Specific kinase activities (both with and without in vivo 12-O-tetradecanoyl phorbol acetate treatment) and the abilities of pp60c-src and pp60c-src(F527) to induce foci, transformed morphologies, and anchorage-independent growth were unaffected by any of the serine mutations. Thus, pp60c-src transforming activity in NIH 3T3 cells is relatively insensitive to phosphorylation at these sites, but there is a suggestion that Ser-17 phosphorylation may have a subtle regulatory effect.
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PMID:Mutation of amino acids in pp60c-src that are phosphorylated by protein kinases C and A. 247 54

Rabbit myelin basic protein (MBP) was phosphorylated by a ganglioside-stimulated protein kinase to a stoichiometry of 1.4 and 2.1 mol phosphate/mol MBP in the presence and absence of GTlb, respectively. Two-dimensional peptide mapping analyses revealed that two of the sites of phosphorylation were distinct from those catalyzed by cAMP-dependent protein kinase or protein kinase C. Phosphorylation of one of these sites by ganglioside-stimulated protein kinase was inhibited by GTlb, suggesting that the inhibitory effect of gangliosides on MBP phosphorylation may be substrate-directed. Although ganglioside-stimulated protein kinase did not phosphorylate MBP at a domain containing residues 82-117, a synthetic peptide Arg-Phe-Ser-Trp-Gly-Ala-Glu-Gly-Gln-Lys corresponding to residues 111-120 was phosphorylated by the kinase in a ganglioside-stimulated manner. These findings suggest that the conformation of MBP may be important in determining its phosphorylatability.
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PMID:Phosphorylation of myelin basic protein and peptides by ganglioside-stimulated protein kinase. 248 Jan 29

Protein kinase C activity has been measured in extracts of larval brain of Drosophila melanogaster, with the synthetic nonapeptide substrate Ala-Ala-Ala-Ser-Phe-Lys-Ala-Lys-Lys-amide. Protein kinase C activity in such extracts is abolished in a Ca2+-dependent manner at 18 degrees C, and partly converted to a form independent of effectors. The decay of protein kinase C activity can be prevented by leupeptin or a crude calpastatin preparation isolated from fly heads, indicating the presence of the Ca2+-dependent neutral protease, calpain, in larval brains. The total protein kinase C levels were nearly the same in wild type and three different dunce "memory-mutant" strains. In contrast, the soluble/particulate activity ratios were different: wild-type, 0.91; dunce M11, 0.46; dunce M11/Df(1)dm75e19, 1.23; dunce2, 0.88. These data suggest that the membrane adherence of protein kinase C in larval brain is governed by the actor of genes other than dunce.
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PMID:Protein kinase C in larval brain of wild-type and dunce memory-mutant Drosophila. 250 May 6

Sn-1,2-diacylglycerols (DAG) and ionized-free calcium can act as intracellular second messengers for cell activation. Traditionally, T-lymphocyte activation is assessed by measurements of DNA synthesis or lymphokine production, but these responses require several days to occur and involve multiple intermediary regulatory steps. In contrast, we have found that T-lymphocytes demonstrate rapid enhancement of A-(alanine-favoring) system amino acid uptake when treated with DAG or ionomycin. A 30-40% increase in the initial velocity of uptake (vi) of the synthetic A-system specific amino acid, methylamino-isobutyric acid (MeAIB), was measured following 5 min of exposure to DAG or ionomycin. The vi was enhanced 60% from 12 to 19 mumol/liter cell water per min after 30 min exposure of T-cells to optimal concentrations of dioctanoylglycerol (30 microM), oleoylacetylglycerol (30 microM), or ionomycin (5 microM) (P less than .01 for each agent). A 50-fold excess of non-radioactive MeAIB inhibited 80% of [14C]MeAIB uptake in both unstimulated and stimulated cells, indicating that uptake remained largely carrier-mediated on treatment with these agents. Cycloheximide, 100 micrograms/ml, inhibited protein synthesis but did not block the A-system amino acid transport enhancement induced by DAG or ionomycin. The DAG-induced increase in the vi was blocked 40% with 100 microM H-7, an inhibitor of protein kinase C. H-7 treatment did not inhibit the ionomycin-induced A-system enhancement. A marked increase in cytoplasmic free calcium was measured when T-lymphocytes were exposed to ionomycin but not on DAG exposure, and the A-system effect of ionomycin but not DAG was blocked by extracellular EGTA. These data are compatible with two pathways for rapid enhancement of A-system amino acid uptake in T-lymphocytes. DAG stimulation is mediated via protein kinase C whereas ionomycin produces an A-system effect of similar magnitude independent of protein kinase C by an increase in cytoplasmic calcium.
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PMID:Diacylglycerol and calcium induce rapid enhancement of A-system amino acid transport by independent mechanisms in human T-lymphocytes. 250 95

A retro-inverso analogue of the pseudosubstrate sequence, Arg-Phe-Ala-Arg-Lys-Gly-Ala25-Leu-Arg-Gln-Lys-Asn-Val (1), found in the regulatory domain of all protein kinase C (PKC) subspecies was synthesized. It shows to be an inhibitor (IC50 = 31 microM) of the phosphorylation, by PKC, of [Ala9.10,Lys11.12] glycogen synthase (1-12). Its analogue in which D Ala25 is replaced by D Ser is not a PKC substrate, but a more potent inhibitor, competitive with the peptidic substrate (IC50 = 5 microM, Ki = 2 microM). Both retro-inverso peptides are highly specific for PKC versus adenosine cAMP-dependent protein kinase (PKA) and are totally stable towards proteolysis by trypsin or pronase.
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PMID:Inhibition of protein kinase C by retro-inverso pseudosubstrate analogues. 251 86

Protein kinase C (Ca2+/phospholipid-dependent enzyme) was shown to be present in renal brush border membranes. To evaluate the influence of protein kinase C activation on three apical transport systems, we studied the effect of phorbol myristate acetate (PMA) and of two diacylglycerol analogs, oleoylacetylglycerol and dioctanoylglycerol, on sodium-dependent uptakes of phosphate (Pi), L-alanine, and alpha-methyl-D-glucopyranoside (MGP), as well as on specific phlorizin binding, in cultured rabbit proximal tubular cells. PMA, at 100 ng/ml, decreased the Vmax of Pi and MGP uptake by 30 and 17%, respectively, but not that of alanine uptake. None of the Km values were affected. PMA also decreased the number of phlorizin binding sites by 40%. PMA-induced inhibition of Pi and MGP uptake was time- and concentration-dependent, was mimicked by oleoylacetylglycerol, dioctanoylglycerol, and the diacylglycerol kinase inhibitor R59022, and was reversed by the protein kinase C antagonist 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H7). The effects of PMA persisted in the presence of amiloride and dimethyl amiloride, and were potentiated by Ca2+ ionophore A23187. Opening of tight junctions blunted subsequent PMA-induced decrease of MGP uptake, but not of Pi uptake. It is concluded that: (i) activation of protein kinase C does not affect similarly Na-Pi, Na-hexose, and Na-alanine cotransport; and (ii) different pathways are likely to be involved in the observed effects.
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PMID:Protein kinase C activation has dissimilar effects on sodium-coupled uptakes in renal proximal tubular cells in primary culture. 253 98

The M27 and H59 variants of Lewis lung carcinoma differ in their responsiveness to the chemotactic elastin peptide Val-Gly-Val-Ala-Pro-Gly (VGVAPG). M27 cells, selected for metastasis to lung, are highly responsive to a positive gradient of VGVAPG. H59 cells, selected for metastasis to liver, do not migrate in response to VGVAPG. Although both cell types bind radiolabeled VGVAPG, Scatchard analysis of 125I-Tyr-VGVAPG binding reveals that M27 cells bind the chemoattractant with a Kd of 2.7 nM, whereas nonresponsive H59 cells bind the peptide with a Kd of 67 nM. These findings indicate that the failure of H59 cells to migrate in response to VGVAPG may be due to the reduced affinity of their VGVAPG receptors. Both receptor affinity and chemotactic responsiveness to VGVAPG can be modulated in each of these two tumor cell lines by the levels of active membrane-associated protein kinase C. Treatment of nonresponsive H59 cells with 12-O-tetradecanoylphorbol 13-acetate increases the level of membrane-bound protein kinase C activity with a concomitant increase in VGVAPG binding affinity and induction of chemotactic responsiveness to VGVAPG. Treatment of M27 cells with the protein kinase C inhibitor, staurosporine, reduces VGVAPG binding affinity and abrogates the chemotactic response. We conclude that chemotactic responsiveness of M27 and H59 tumor cells is dependent upon high VGVAPG receptor affinity, which is strongly correlated to high levels of membrane-bound protein kinase C activity.
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PMID:Membrane-bound protein kinase C modulates receptor affinity and chemotactic responsiveness of Lewis lung carcinoma sublines to an elastin-derived peptide. 254 74


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