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

The regulation and expression of protein kinase C (PKC) and phosphomyristin C (PMC) (a principal substrate of PKC which is the major myristylated protein in lymphocyte and glioma lines that express it) in murine B and T lymphocytes were investigated. Both PMC and PKC are differentially regulated during T-cell development. The level of PMC expression is highest in CD4-8-, intermediate in CD4+8+, and lowest in J11d-, CD4, or CD8 single-positive thymocytes. PKC is equally expressed by all three thymic populations. In striking contrast to thymocytes, resting peripheral lymph node T cells and T-cell clones express little if any PMC and reduced levels of PKC. Neither PKC nor PMC is significantly induced upon the activation of lymph node T cells: treatment with anti-CD3 antibodies or anti-CD3 and interleukin-2 fails to induce PKC, whereas PMC is not induced by anti-CD3 alone and is only slightly induced by anti-CD3 and interleukin-2. In contrast to the situation with T cells, PMC and PKC are constitutively expressed at moderate levels in mature B cells. PMC is greatly increased in B-cell blasts generated by cross-linking the antigen receptor with anti-immunoglobulin. These results demonstrate that PMC and PKC are differentially regulated during the development and activation of B and T cells, suggesting that cellular events that rely upon PKC and PMC may differ during ontogeny and activation of different lymphocyte subsets.
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PMID:A major myristylated substrate of protein kinase C and protein kinase C itself are differentially regulated during murine B- and T-lymphocyte development and activation. 278 36

An acidic phosphoprotein of Mr 80,000, the 80K protein, is a substrate for protein kinase C in fibroblasts and epidermal carcinoma cells. We purified the 80K protein from human squamous carcinoma Ca9-22 cells and fractionated it into two distinct molecular species, designated the 80K-L and 80K-H proteins. The amino acid sequences of the NH2-terminal region and cyanogen bromide-cleaved fragments of the 80K-H protein were determined and a corresponding oligonucleotide sequence was synthesized. Using this as a probe, two cDNA clones, lambda 80H-1 and lambda 80H-2, were selected from a lambda gt10 cDNA library from human A431 cells. The nucleotide sequence has an open reading frame of 1581 nucleotides encoding a protein of 527 amino acids. The deduced amino acid sequence revealed an extremely Glu-rich region. RNA blot analysis with the lambda 80H-1 cDNA clone detected two polyadenylated transcripts of 2.3 and 3.5 kb in Ca9-22 cells. Spot blot hybridization using flow-sorted human chromosomes provided evidence that the gene (G19P1) encoding 80K-H protein maps to human chromosome 19.
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PMID:Isolation of cDNAs encoding a substrate for protein kinase C: nucleotide sequence and chromosomal mapping of the gene for a human 80K protein. 279 84

B16 melanoma cells differentiate upon treatment with retinoic acid (RA). This differentiation process is accompanied by an increase of protein kinase C alpha (PKC alpha) mRNA and protein levels. Overexpression of PKC alpha in these cells results in a more differentiated phenotype, suggesting the importance of this protein in the control of differentiation by RA. The purpose of the study reported here was to determine the subcellular distribution of the RA-induced PKC alpha, whether the RA-induced increase in PKC alpha protein levels was accompanied by an increase in in situ enzyme activity, and whether RA altered AP-1 transcriptional activity. We found that RA treatment increased PKC alpha protein levels in all subcellular compartments examined, but it also induced a selective enrichment in nuclear-associated PKC alpha levels. Treating cells with an active phorbol ester induced translocation of PKC alpha to membrane fractions, but had no effect on nuclear PKC alpha levels. RA also increased PKC enzymatic activity in intact cells as determined by phosphorylation of the PKC-specific endogenous substrate MARCKS. However, while RA induced a five- to eightfold increase in total cellular PKC alpha protein levels, it only increased MARCKS phosphorylation by twofold. In light of the increase in in situ PKC enzyme activity and the enrichment of nuclear PKC alpha, we determined whether AP-1 activity might be increased in RA-treated cells. Use of luciferase reporter gene constructs with or without AP-1 elements transfected into B16 cells indicated that RA induced a four- to fivefold increase in AP-1 transcriptional activity. These results suggest a hypothesis whereby RA-induced nuclear PKC alpha might lead to increased AP-1 activity and show that RA-induced growth inhibition and differentiation are not always accompanied by an inhibition of AP-1 activity as has been proposed by other investigators.
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PMID:Retinoic acid specifically increases nuclear PKC alpha and stimulates AP-1 transcriptional activity in B16 mouse melanoma cells. 749 37

Calphostin-C with perylenequinone structure is known to bind the regulatory domain of protein kinase C (PKC) and to inhibit kinase activity in vitro in a light-dependent fashion. We have found that calphostin-C induces substantial serine and threonine phosphorylation of the epidermal growth factor (EGF) receptor in a light-dependent fashion in the EGF receptor-hyperproducing squamous carcinoma cell line NA. Tryptic phospho-peptide mapping and phospho-amino acid analysis revealed that calphostin-C-enhanced phosphorylation was on threonine 669, serine 671, serine 1046/1047, and serine 1166. However, calphostin-C did not inhibit phosphorylation of the 80 K protein, a cytosolic major substrate of PKC (MARCKS). Staurosporine, a potent PKC inhibitor with affinity for the catalytic domain of PKC, inhibited phosphorylation of the 80 K protein and 12-O-tetradecanoyl-13-phorbol acetate induction of EGF receptor phosphorylation but did not inhibit the calphostin-C induction of the EGF receptor phosphorylation. These results suggest that the target of calphostin-C in vivo is different from that of staurosporine and thus calphostin-C in vivo does not inhibit PKC. Furthermore, calphostin-C enhanced the internalization of phosphorylated EGF receptor. Thus, calphostin-C apparently activates a novel signal transduction pathway which involves phosphorylation and internalization of the EGF receptor via light-dependent mechanism.
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PMID:Calphostin-C stimulates epidermal growth factor receptor phosphorylation and internalization via light-dependent mechanism. 750 75

Phosphorylation of glutamate receptors (GluRs) is emerging as an important regulatory mechanism. In this study 32P labeling of non-NMDA GluRs was investigated in cultured hippocampal neurons stimulated 2-15 min with agonists that selectively stimulate either Ca2+/calmodulin-dependent protein kinase II (CaM-kinase II), Ca2+/phospholipid-dependent protein kinase C (PKC), or cAMP-dependent protein kinase A (PKA). Treatment of hippocampal neurons with glutamate/glycine (Glu/Gly), ionomycin, or 12-O-tetradecanoylphorbol 13-acetate (TPA) increased 32P labeling of immunoprecipitated alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionate (AMPA)-type GluRs by 145%, 180%, and 227%, respectively, of control values. This increased phosphorylation of GluRs was predominantly 32P-Ser with little 32P-Thr and no detectable 32P-Tyr. Glu/Gly and ionomycin, but not TPA, also increased 32P labeling of CaM-kinase II by 175% and 195%, respectively, of control values. Of these three agonists, only TPA stimulated phosphorylation of MARCKS (225% of control), a specific substrate of PKC. Forskolin treatment gave a three- to fourfold increase in the active catalytic subunit of PKA but did not result in the 32P labeling of AMPA-type GluRs, CaM-kinase II, or MARCKS. Phosphorylation of GluRs in response to Glu/Gly was blocked by a specific NMDA receptor/ion channel antagonist (DL-2-amino-5-phosphonovaleric acid) or by a cell-permeable inhibitor of CaM-kinase II (1-[N,O-bis(1,5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4- phenylpiperazine, KN-62). These results are consistent with the hypothesis that Ca2+ influx through the NMDA-type ion channel can activate CaM-kinase II, which in turn can phosphorylate and regulate AMPA-type GluR ion channels (McGlade-McCulloh et al., 1993).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Phosphorylation of AMPA-type glutamate receptors by calcium/calmodulin-dependent protein kinase II and protein kinase C in cultured hippocampal neurons. 750 63

The relationship between lipid domains and enzyme activity was studied via the direct visualization and quantitation of domains by fluorescence digital imaging microscopy. The substrate used in these experiments was a basic peptide derived from a prominent cellular substrate (MARCKS) of protein kinase C. The MARCKS peptide and phosphatidylserine, which were labeled by two different fluorophores, colocalized into domains in large vesicles (5-10 microns). Increasing the ionic strength disrupted the domains of the MARCKS peptide and phosphatidylserine, and this was accompanied by a decrease in protein kinase C activity. Dansylpolylysine, which inhibits protein kinase C, was similar to the MARCKS peptide in forming domains enriched in phosphatidylserine. The degree of enrichment of the MARCKS peptide in the phosphatidylserine domains decreased proportionally with protein kinase C activity when polylysine was added. Polylysine caused the MARCKS peptide to be displaced from the domains into the nondomain areas of the vesicles. This suggested that binding of the substrate to the vesicles was not the critical factor for protein kinase C activity, but rather it was the organization of the substrate into domains that was related to the activation of the enzyme. Gramicidin, which was chosen to represent a neutral membrane protein, was excluded from the domains with phosphatidylserine, and it had no effect on the enrichment of the domains or the enzyme activity. The results of this study show that the formation of membrane domains can be important for the activation of protein kinase C and the activity can be inhibited by disrupting the domains.
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PMID:Membrane domains containing phosphatidylserine and substrate can be important for the activation of protein kinase C. 753 92

Activation of protein kinase C (PKC) by angiotensin II or 12-O-tetradecanoylphorbol-13-acetate (TPA) was associated with a mitogenic response in RIE-1 rat intestinal epithelial cells. However, whereas in control experiments using Swiss 3T3 cells TPA stimulated phosphorylation of the major PKC substrate, MARCKS, the agent did not induce the phosphorylation of any protein with the electrophoretic mobility pattern of MARCKS in RIE-1 cells. However, TPA was able to activate PKC in RIE-1 cells since the agent reduced ('transmodulated') 125I-EGF binding to the cells. The failure of TPA to induce phosphorylation of MARCKS in RIE-1 cells was due to the lack of expression of MARCKS protein and mRNA by these cells. MARCKS is not therefore required for mitogenic signalling via PKC in RIE-1 cells.
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PMID:The myristoylated alanine-rich C-kinase substrate (MARCKS) is not required for mitogenic signalling via protein kinase C in cultured rat intestinal epithelial (RIE-1) cells. 754 20

Sphingosylphosphorylcholine (SPC) is a potent mitogen for Swiss 3T3 cells, but the signaling mechanisms involved are poorly characterized. Here, we report that addition of SPC induces a rapid and transient activation of p42 mitogen-activated protein kinase (p42MAPK) in these cells. SPC-induced p42MAPK activation peaked at 5 min and was undetectable after 30 min of incubation with SPC. The effect of SPC on p42MAPK activation was comparable to that induced by bombesin and platelet-derived growth factor. As SPC strongly induced phosphorylation of the major protein kinase C (PKC) substrate 80K/MARCKS in either intact or permeabilized cells, we examined whether PKC could be involved in SPC-induced p42MAPK activation. Here, we demonstrate that p42MAPK activation by SPC was dependent on PKC activity as shown by inhibition of PKC with the bisindolymaleimide GF 109203X or down-regulation of PKC by prolonged treatment of Swiss 3T3 cells with phorbol esters. Activation of both PKC and p42MAPK by SPC was markedly inhibited by treatment with pertussis toxin, implicating a G proteins(s) of the Gi/G(o) subfamily in the action of SPC. SPC-induced rapid activation of a downstream target of p42MAPK, p90 ribosomal S6 kinase (p90rsk), also required PKC and a pertussis toxin-sensitive G protein. In addition, SPC-induced mitogenesis was dependent on a Gi protein in Swiss 3T3 cells. SPC also induced p42MAPK activation and DNA synthesis in secondary cultures of mouse embryo fibroblasts through a pertussis toxin-sensitive pathway. As G proteins link many cell surface receptors to effector proteins, we hypothesize, therefore, that SPC could bind to a receptor that mediates at least some of its biological effects in Swiss 3T3 cells and mouse embryo fibroblasts.
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PMID:Sphingosylphosphorylcholine activation of mitogen-activated protein kinase in Swiss 3T3 cells requires protein kinase C and a pertussis toxin-sensitive G protein. 759 45

Safingol is a lysosphingolipid protein kinase C (PKC) inhibitor that competitively interacts at the regulatory phorbol binding domain of PKC. We investigated the effects of safingol on antineoplastic drug sensitivity and PKC activity of MCF-7 tumor cell lines. Safingol treatment of 32P-labeled MCF-7 WT and MCF-7 DOXR cells inhibited phosphorylation of the myristoylated alanine-rich protein kinase C substrate in both cell lines, suggesting inhibition of cellular PKC. However, only in MCF-7 DOXR cells did safingol treatment increase accumulation of [3H]vinblastine and enhance toxicity of Vinca alkaloids and anthracyclines. Drug accumulation changes in MCF-7 DOXR cells treated with safingol were accompanied by inhibition of basal and phorbol 12,13-dibutyrate-stimulated phosphorylation of P-glycoprotein (P-gp). Expression of P-gp and levels of mdr1 message in MCF-7 DOXR cells were not altered by safingol treatment alone or in combination with vinblastine. Treatment of MCF-7 DOXR cell membranes with safingol did not inhibit [3H]vinblastine binding or [3H]azidopine photoaffinity labeling of P-gp. Furthermore, safingol did not stimulate P-gp ATPase activity in membranes prepared from MCF-7 DOXR cells. We conclude that enhanced drug accumulation and sensitivity in MCF-7 DOXR cells treated with safingol are correlated with inhibition of PKC rather than competitive interference with P-gp drug binding through direct interaction with P-glycoprotein.
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PMID:Partial inhibition of multidrug resistance by safingol is independent of modulation of P-glycoprotein substrate activities and correlated with inhibition of protein kinase C. 759 89

The phospholipase A2 neurotoxin, beta-bungarotoxin, presynaptically blocks acetylcholine release. Its mechanism of action is unknown; however, our previous studies suggest that it inhibits phosphorylation of synaptosomal proteins, which might be expected to decrease neurotransmitter release. In our present study, we found that 1 nM beta-BuTX blocked phorbol ester-stimulated phosphorylation of GAP-43, MARCKS and synapsin I without affecting their basal phosphorylation. In contrast, a 1 nM concentration of the non-neurotoxic enzyme. Naja naja atra phospholipase A2 did not affect the phorbol ester-stimulated phosphorylation of these proteins but increased the basal phosphorylation of GAP-43 and MARCKS. Although it has been suggested that cytosolic calmodulin is increased by phosphorylation of the protein kinase C substrates, GAP-43 and MARCKS, we found no change in calmodulin levels by phorbol ester or beta-bungarotoxin. The stimulation of phosphorylation by Naja naja atra phospholipase A2 may be due to products liberated as a result of its phospholipase A2 activity. In contrast, the inhibition of phosphorylation by beta-bungarotoxin appears to be due to an action which may be unrelated its relatively weak phospholipase A2 activity. Inhibition of phosphorylation by beta-bungarotoxin is a possible mechanism by which it could block acetylcholine release. Furthermore, beta-bungarotoxin may be a useful tool to study the physiological role of phosphorylation of synaptosomal proteins in neurotransmitter release.
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PMID:beta-Bungarotoxin blocks phorbol ester-stimulated phosphorylation of MARCKS, GAP-43 and synapsin I in rat brain synaptosomes. 767 66


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