EC:2.7.11.13 - FACTA Search

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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 regulation of second-messenger production and protein phosphorylation by glutamate has been investigated in primary cultures of pure hippocampal pyramidal neurons. Embryonic rat pyramidal neurons were prepared according to the procedures of Bartlett and Banker (1984) and studied 1-21 d after plating. Glutamate caused a transient increase in intracellular free [Ca2+], determined with fura-2, in the presence of 1.26 mM extracellular Ca2+, but not in 50 nM free Ca(2+)-containing solution. Glutamate also transiently increased cellular diacylglycerol content in both normal and low-[Ca2+] media. Neurons were prelabeled with 32P-orthophosphate to label intracellular ATP, then stimulated with glutamate (100 microM). A rapid transient incorporation of 32P into primarily three proteins of 120, 87, and 48 kDa was found by analysis of two-dimensional gels. At 30 sec after glutamate stimulation, 32P incorporation into the 87-kDa and 48-kDa proteins peaked (240% and 170% basal levels, respectively), and by 2 min, phosphorylation of the 87-kDa protein had returned to basal levels, while that of the 48-kDa protein decreased but remained above control levels. The phosphorylation of these proteins appeared to be mediated by protein kinase C (PKC) because all three showed an increase in phosphorylation after phorbol ester treatment of cultures. Phosphate incorporation was accompanied by an acidic shift in the isoelectric point of both 87- and 48-kDa proteins. Glutamate stimulation resulted in phosphorylation in the presence and absence of Ca2+ influx. Antibody recognition and biochemical characteristics indicated that the 87-kDa phosphoprotein is the PKC substrate MARCKS (myristoylated, alanine-rich C-kinase substrate). The 48-kDa protein, though very similar to GAP-43, was not recognized by specific antibodies raised against GAP-43. These results suggest that glutamate stimulates the transient generation of second messengers that activate PKC in hippocampal neurons, resulting in a significant increase in the phosphorylation of three specific proteins.
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PMID:Glutamate-stimulated protein phosphorylation in cultured hippocampal pyramidal neurons. 167 25

We have investigated whether TNF-induced changes in human endothelial cell (EC) surface Ag expression are mediated by protein kinase C (PKC). This suggestion arose from the observations that PMA, a potent PKC activator, can mimic TNF by inducing expression of endothelial leukocyte adhesion molecule 1, intercellular adhesion molecule 1 (ICAM-1), and class I MHC molecules on human EC. However, in contrast to the actions of PMA, TNF neither causes membrane translocation of PKC nor induces the phosphorylation of the myristoylated alanine-rich C kinase substrate, two measures of PKC activation. Moreover, the PKC inhibitor staurosporine can block PMA-induced endothelial leukocyte adhesion molecule 1 expression at 4 h, but does not inhibit the actions of TNF. At 24 h, staurosporine itself induces intercellular adhesion molecule 1 and class I MHC, and acts additively with TNF. Twenty four hour treatment with PMA causes loss of PKC. We propose that at 24 h, staurosporine and PMA share a mechanism of action, namely diminution of PKC activity. However, 24 h treatment with TNF does not reduce the amount of PKC nor does it prevent activation of PKC by PMA. We conclude that TNF effects in EC are not mediated by PKC activation or inactivation.
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PMID:Tumor necrosis factor induction of endothelial cell surface antigens is independent of protein kinase C activation or inactivation. Studies with phorbol myristate acetate and staurosporine. 170 32

Members of the protein kinase C (PKC) family are characterized by an NH2-terminal regulatory domain containing binding sites for calcium, phosphatidylserine, and diacylglycerol (or tumor-promoting phorbol esters), a small central hinge region and a COOH-terminal catalytic domain. We have constructed fusion proteins in which the regulatory domain of PKC alpha was removed and replaced by a 19-amino acid leader sequence containing a myristoylation consensus or by the same sequence in which the amino-terminal glycine was changed to alanine to prevent myristoylation. The goal was to generate constitutively active mutants of PKC that were either membrane bound, due to their myristoylation, or cytoplasmic. Western blotting of fractions from COS cells transfected with plasmids encoding wild-type and mutant proteins revealed that PKC alpha resided entirely in a Triton X-100 soluble (TS) fraction, whereas both the myristoylated and nonmyristoylated mutants were associated primarily with the nuclear envelope fraction. A similar mutant that lacked the 19 amino acid leader sequence was also found almost entirely in the nuclear envelope, as was a truncation mutant containing only the regulatory domain, hinge region, and a small portion of the catalytic domain. However, an additional truncation mutant consisting of only the regulatory domain plus the first one-third of the hinge region was almost entirely in the TS fraction. A nonmyristoylated fusion protein containing only the catalytic domain was also found in the nuclear envelope. Immunostaining of cells transfected with these constructs revealed that both the myristoylated and nonmyristoylated mutants were localized in nuclei, whereas wild-type PKC alpha was primarily cytoplasmic and perinuclear. Phorbol dibutyrate treatment of PKC alpha-transfected cells resulted in increased perinuclear and nuclear staining. The results are consistent with a model in which activation of PKC, by phorbol esters or by deletion of the regulatory domain, exposes regions in the hinge and catalytic domains that interact with a PKC "receptor" present in the nuclear envelope, and may explain the ability of wild-type PKC to be translocated to the nucleus under certain conditions.
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PMID:Deletion of the regulatory domain of protein kinase C alpha exposes regions in the hinge and catalytic domains that mediate nuclear targeting. 173 20

The mitogen-activated 70K S6 kinase has an apparent Km for 40 S ribosomal subunits of 0.25 microM. The apparent Km for a synthetic peptide derived from the carboxyl terminus of S6 and containing all of the in vivo sites of phosphorylation was 2.5-fold higher. A number of shorter peptides revealed that the substrate recognition determinants for the preferred site of phosphorylation, Ser236, reside in a seven-amino acid stretch of S6, residues 231-217. Critical to recognition is a block of 3 consecutive arginines, especially Arg231 and Arg233. In contrast, replacement of Ser235 or the preferred site of phosphorylation, Ser236, with alanine has little effect on the apparent Km. Based on this data the consensus recognition sequence would be Arg-(Arg)-Arg-X-X-Ser-X. A number of kinases known to phosphorylate S6, including cAMP-dependent protein kinase and protein kinase C and the 92K S6 kinase II, were also tested for their ability to phosphorylate a decapeptide containing all the critical recognition determinants. Finally, a synthetic peptide containing a putative 70K S6 kinase autoinhibitory domain did not serve as a substrate for the enzyme but did inhibit its activity, although much less effectively than a synthetic peptide containing all the recognition determinants.
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PMID:Substrate recognition determinants of the mitogen-activated 70K S6 kinase from rat liver. 173 63

We have used normal human monocytes as a model system to begin elucidating the signal transduction mechanism associated with the IL-3R. Normal human monocytes deprived of human serum and CSF become quiescent in vitro. Stimulation of these cells with rIL-3 induces expression of the c-jun protooncogene, as detected by Northern blotting of total monocyte RNA. This protooncogene is also induced in these cells by phorbol ester through direct stimulation of protein kinase C. Concentrations of the protein kinase C inhibitor I-(5-isoquindinyl-sulfonyl)-2 methylpiperazine (H-7) between 30 and 100 microM (5-20 x Ki) inhibit this induction by phorbol ester. The same concentration-range of H-7 completely inhibited the induction of c-jun by human IL-3. A structural analog of H-7 designated HA-1004 preferentially inhibits cyclic nucleotide-dependent protein kinase rather that protein kinase C. HA-1004 at 5 to 20 x Ki did not inhibit IL-3-induced c-jun mRNA accumulation. Further 30 microM genistein that is an effective inhibitor of cellular tyrosine kinases did not inhibit IL-3-induced c-jun expression. Immunoprecipitation of lysates from [32P]orthophosphate labeled cells with antiphosphotyrosine polyclonal antibody showed that IL-3-stimulated phosphorylation of a 70-kDa protein and a 110-kDa protein on tyrosine, and that these protein phosphorylations were completely inhibited by 30 microM genistein. As further confirmation that IL-3 is stimulating protein kinase C in human monocytes we have found that IL-3 stimulates phosphorylation of the unique protein kinase C substrate myristoylated alanine-rich C kinase substrate in these cells. It is therefore likely that the interaction of IL-3 with its receptor generates diacylglycerol and stimulates the Ca2+/phospholipid-dependent protein kinase C.
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PMID:Human IL-3 induction of c-jun in normal monocytes is independent of tyrosine kinase and involves protein kinase C. 173 30

Synaptosomes prepared from brain tissues are known to retain morphological and functional characteristics of the nerve ending. Little information is available, however, as to the biochemical events underlying synaptogenesis and transmitter release. Increasing body of evidence suggests that protein kinase C (PKC) plays crucially important roles through phosphorylation of membrane proteins such as GAP-43 (for 43-kDa growth-associated protein) and 87-kDa MARCKS (for myristoylated, alanine-rich C kinase substrate) in many aspects of the neuronal function. Among them, arrangement of membrane cytoskeletal protein is proposed to be one of the primary sites of PKC action. The present study is an attempt to isolate and characterize PKC associated with synaptosomal membrane cytoskeleton. Rat brain synaptosomal Triton X-100 insoluble elements (cytoskeleton) contains specific [3H]phorbol dibutyrate binding activity and 78-kDa protein which reacts with an antibody against beta II-PKC subspecies. Although 78-kDa protein could not be solublized by the treatment with various ionic and non-ionic detergents and/or high concentrations of salts such as NaCl and LiBr, the fragment of 78-kDa protein was produced and solublized from cytoskeleton by limited proteolysis with calpain II, which cleaves PKC at one or two specific sites of the enzyme to produce catalytic and regulatory fragments. The solubilized 46-kDa fragment was identical with the catalytic fragment of beta II-PKC. The results indicate that this PKC subspecies is tightly associated with the cytoskeletal network of synaptic membranes.
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PMID:Isolation and characterization of protein kinase C from rat brain synaptosome cytoskeleton. 174 42

The MARCKS (myristylated alanine-rich C-kinase substrate) protein is an abundant calmodulin-binding protein that is a major and specific endogenous substrate of protein kinase C (PKC). Stimulation of cells with phorbol esters or other activators of PKC has been shown previously to result in rapid phosphorylation of MARCKS proteins and redistribution of these myristylated C-kinase substrates from membrane to cytosol. Here we show that NIH3T3 murine fibroblasts transformed by p21-HA-C-RAS or pp60-V-SRC oncoproteins have markedly reduced levels of p68-MARCKS and that most of the remaining MARCKS protein is found in the cytosol. 3T3 cells containing a nontransforming oncoprotein p26-BCL2, in contrast, exhibited normal levels and distribution of p68-MARCKS. When taken together with recent evidence that MARCKS proteins are involved in regulating organization of the membrane cytoskeleton, our findings suggest that oncoprotein-mediated alterations in MARCKS protein levels and subcellular distribution may contribute to the development or maintenance of the transformed phenotype.
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PMID:Transformed 3T3 cells have reduced levels and altered subcellular distribution of the major PKC substrate protein MARCKS. 183 87

We recently reported that autophosphorylated rat brain protein kinase C (PKC) catalyzes a Ca2(+)- and phosphatidylserine- (PS-) dependent ATPase reaction. The Ca2(+)- and PS-dependent ATPase and histone kinase reactions of PKC each had a Km app(ATP) of 6 microM. Remarkably, the catalytic fragment of PKC lacked detectable ATPase activity. In this paper, we show that subsaturating concentrations of protein substrates accelerate the ATPase reaction catalyzed by PKC and that protein and peptide substrates of PKC induce ATPase catalysis by the catalytic fragment. At subsaturating concentrations, histone III-S and protamine sulfate each accelerated the ATPase activity of PKC in the presence of Ca2+ and PS by as much as 1.5-fold. At saturating concentrations, the protein substrates were inhibitory. Poly(L-lysine) failed to accelerate the ATPase activity, indicating that the acceleration observed with histone III-S and protamine sulfate was not simply a result of their gross physical properties. Furthermore, histone III-S induced the ATPase activity of the catalytic fragment of PKC, at both subsaturating and saturating histone concentrations. The induction of ATPase activity was also elicited by the peptide substrate Arg-Arg-Lys-Ala-Ser-Gly-Pro-Pro-Val, when the peptide was present at concentrations near its Km app. The induction of the ATPase activity by the nonapeptide provides strong evidence that the binding of phospho acceptor substrates to the active site of PKC can stimulate ATP hydrolysis. Taken together, our results indicate that PKC-catalyzed protein phosphorylation is inefficient, since it is accompanied by Pi production.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Stimulation of the ATPase activity of rat brain protein kinase C by phospho acceptor substrates of the enzyme. 184 1

We report that the putative protein kinase C inhibitor, K252a, at concentrations of 0.2 and 1 microM, inhibited the respiratory burst induced by fluoride and formyl-methionyl-leucyl-phenyl-alanine respectively, both in human neutrophils primed with a subthreshold dose of phorbol myristate acetate and in non-primed neutrophils. In addition, K252a effectively inhibited ConA-zymosan-mediated superoxide generation in Ca2(+)-depleted neutrophils, with virtually maximal inhibition seen at 1 microM. These results suggest that protein kinase C is involved in the putative phosphatidylinositol bisphosphate-independent signal transduction mechanism of the respiratory burst as well as the pathway dependent on phosphatidylinositol bisphosphate hydrolysis.
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PMID:The protein kinase C inhibitor, K252a, inhibits superoxide production in human neutrophils activated by both PIP2-dependent and -independent mechanisms. 185 Feb 76

The JAR human placental choriocarcinoma cell line transports taurine, concentrating it over 1000-fold inside the cell. The transport system is energized by a Na+ gradient and exhibits an absolute requirement for Cl-. Neutral beta-amino acids such as beta-alanine and hypotaurine effectively compete with the system, whereas neutral alpha-amino acids such as alanine, leucine and alpha-aminoisobutyric acid do not. The transport system interacts with gamma-aminobutyric acid to an appreciable extent. Kinetic analysis reveals that the taurine transport system in this cell line is of a high-affinity and low-capacity type (apparent dissociation constant 2.3 +/- 0.3 microM; maximal velocity 88.5 +/- 5.0 pmol/3 min per mg of protein). Pretreatment of the JAR choriocarcinoma cells with phorbol 12-myristate 13-acetate results in the inhibition of the taurine transport system in a dose-dependent manner. The inhibition is blocked by co-treatment of the cells with staurosporine, an inhibitor of protein kinase C. The inactive phorbol ester, 4 alpha-phorbol 12,13-didecanoate, has no effect on the transport system. These data show that the choriocarcinoma cells express a taurine transporter with characteristics similar to those of the taurine transporter described in the normal human placenta, and that the activity of the transporter in these cells is under the regulatory control of protein kinase C.
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PMID:Transport of taurine and its regulation by protein kinase C in the JAR human placental choriocarcinoma cell line. 185 47

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