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)

5-Hydroxytryptamine (5-HT) has been shown to activate the hypothalamo-pituitary-adrenal axis, possibly by a direct action on hypothalamic CRF synthesis and release. In order to study the mechanisms involved in this effect, foetal hypothalamic cells were cultured and corticotropin-releasing factor-41 (CRF) release was measured by radioimmunoassay. 5-HT induced CRF release in a dose-dependent manner. Further studies were performed with a specific protein kinase C inhibitor, H-7 (1-(5-isoquinolinesulfonyl)-2-methyl-piperazine) and a specific cyclic adenosine monophosphate-dependent protein kinase inhibitor, IP-20. Basal release of CRF-41 from the cultured hypothalamic cells was unaffected by IP-20 and was only diminished at a high (50 microM) concentration of H-7. 5-HT stimulated-CRF release, however, was blocked by both H-7 and IP-20. Dexamethasone and aldosterone both caused a dose-dependent inhibition of 5-HT induced CRF release. These results demonstrate that CRF can be released from hypothalamic neurons in response to 5-HT through a protein kinase C and protein kinase A dependent mechanism and that 5-HT stimulated CRF release can be inhibited by dexamethasone and aldosterone.
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PMID:5-Hydroxytryptamine stimulates corticosteroid-sensitive CRF release from cultured foetal hypothalamic cells. Role of protein kinases. 163

The interaction of high density lipoproteins (HDL) with the HDL receptor stimulates the translocation of cholesterol from intracellular pools to the plasma membrane where the cholesterol becomes available for removal by appropriate acceptors. The role of signal transduction through protein kinase C in HDL receptor-dependent cholesterol translocation and efflux was examined using cholesterol-loaded cultured human skin fibroblasts. Treatment of cells with HDL3 activated protein kinase C, demonstrated by a transient increase in membrane associated kinase activity. Kinase activation appeared to be dependent on binding of HDL3 to the HDL receptor, since tetranitromethane-modified HDL3, which does not bind to the receptor, was without effect. Translocation of intracellular sterol to the plasma membrane was stimulated by treatment of cells with the protein kinase C activators, dioctanoylglycerol and phorbol myristic acetate, and the calcium ionophore A23187. Conversely, treatment of cells with sphingosine, a protein kinase C inhibitor, reduced HDL3-mediated translocation and efflux of intracellular sterols. However, sphingosine had no effect on efflux of labeled cholesterol derived from the plasma membrane. Down-regulation of cellular protein kinase C activity by long term incubation with phorbol esters also inhibited HDL3-mediated efflux of intracellular sterols and abolished the ability of sphingosine to further inhibit HDL3-mediated efflux. These studies support the conclusion that HDL receptor-mediated translocation and efflux of intracellular cholesterol occurs through activation of protein kinase C.
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PMID:Protein kinase C as a mediator of high density lipoprotein receptor-dependent efflux of intracellular cholesterol. 164 39

The effect of the CD28 activation pathway on the immunosuppressive action of CsA was assessed. Human peripheral blood lymphocytes were stimulated with anti-CD3, bryostatin (Bryo) a novel activator of protein kinase C (PKC) and anti-CD28 singly or in combination, to which graded doses of CsA were added to determine relative sensitivity. Proliferation, IL-2 production, and IL-2 receptor expression were assessed and the IC50 determined. Lymphocytes stimulated with Bryo exhibited a marginal proliferative response but expressed the IL-2 receptor despite the presence of CsA. Addition of anti-CD3 or anti-CD28 to Bryo-stimulated lymphocytes promoted a vigorous proliferative response. CsA effectively inhibited the proliferative response and IL-2 production induced with anti-CD3 and Bryo but did not inhibit the response of cells stimulated with anti-CD28 and Bryo. However, II-2 receptor expression in both sets of cultures were comparable due to the induction of IL-2 receptor by Bryo and was not inhibited by CsA. Costimulation of lymphocytes with anti-CD3 plus anti-CD28 resulted in a 2-3-fold enhancement of proliferation compared with lymphocytes stimulated with anti-CD3 alone. Addition of CsA to lymphocytes stimulated with anti-CD3 resulted in the dose-dependent suppression of the proliferative response and IL-2 production (IC50 = 10-25 nM) but less so for IL-2 receptor expression (IC50 = 100-150 nM). In comparison, the proliferative response and IL-2 production elicited by anti-CD3 + anti-CD28 was more resistant to the effects of CsA (IC50 = 100-200 nM). However, IL-2 receptor expression exhibited comparable sensitivity to CsA (IC50 = 100-200 nM) in the presence of anti-CD28. Combination drug:drug studies revealed that CsA and the protein kinase C inhibitor H-7 were additive for both anti-CD3 and anti-CD3 plus anti-CD28 response. On the other hand, the cGMP-dependent protein kinase inhibitor H-8 was synergistic with CsA in inhibiting the response of lymphocytes to anti-CD3 plus anti-CD28 but only additive for responses to anti-CD3. Taken together, these data suggest that CsA inhibits T cell activation at two distinct levels, leading to inhibition of IL-2 production and inhibition of IL-2 receptor expression. Activation of the CD28 pathway partially overcomes the inhibitory activity of CsA on IL-2 production and may be mediated by indirect activation of a cGMP-dependent protein kinase.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The effect of the CD28 activation pathway on the immunosuppressive action of cyclosporine. 164 6

This study investigated the intracellular signal transduction regulating the appearance of HLA class I antigens on Huh 6 cells induced by interferon-gamma. The expression was blocked by a protein kinase C inhibitor, H-7, but not by a calmodulin antagonist, W-7, nor by a protein kinase A inhibitor, H-8, at low dose. The antigen expression was induced by a direct activator of protein kinase C, phorbol myristate acetate, but not by calcium ionophore A23187 nor an analog of cAMP, dbcAMP. Therefore, we concluded that protein kinase C is involved in the expression of HLA class I antigens on Huh 6 cells induced by interferon-gamma but Ca(2+)-calmodulin and cAMP are not.
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PMID:Signal transduction pathways in the induction of HLA class I antigen expression on Huh 6 cells by interferon-gamma. 164 5

The mechanisms by which hydrogen peroxide and, for comparison, 4-beta-phorbol-12-myristate-13-acetate (PMA) stimulate release of radiolabeled arachidonic acid (14C-AA) in cultured intestinal epithelial cells (INT 407) were investigated. Both hydrogen peroxide and PMA caused a rapid (3 min) and dose-related intracellular release of free 14C-AA, followed by a dose- and time-dependent release of 14C-AA into the extracellular medium, but hydrogen peroxide was about 50,000 times less effective than PMA in releasing 14C-AA. No 14C-AA was released on stimulation with 4-alpha-phorbol-12,13-di-decanoate (PDD), a phorbol ester that does not activate protein kinase C. The 14C-AA release was reduced by the phospholipase A2 inhibitors nordihydroguaiaretic acid and 4-bromophenacyl bromide and by the calmodulin/protein kinase C inhibitor trifluoperazine and the protein kinase C inhibitor 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7). However, H-7 was less effective than the other inhibitors in reducing the hydrogen peroxide-stimulated 14C-AA release. The hydrogen peroxide-stimulated, but not the PMA-stimulated, rapid (3 min) 14C-AA release was associated with an increased influx of extracellular calcium. Stimulation of the cells with PMA resulted in phosphorylation of a cellular protein of about 32 kDa, whereas no phosphorylation of this protein was detected after stimulation with hydrogen peroxide. Taken together, these findings indicate that (i) both PMA and hydrogen peroxide may stimulate phospholipase A2-mediated AA release from human intestinal epithelial cells; (ii) this stimulation is brought about via protein kinase C and calmodulin-mediated events; (iii) PMA-stimulated 14C-AA release is associated with phosphorylation of a 32-kDa protein, possibly lipocortin, whereas the hydrogen peroxide-stimulated release is not; and (iv) calmodulin is more important for the hydrogen peroxide-stimulated 14C-AA release than is protein kinase C. The possibility that hydrogen peroxide-evoked AA release may contribute to the mucosal abnormality in Crohn's disease is discussed.
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PMID:Hydrogen peroxide stimulates phospholipase A2-mediated arachidonic acid release in cultured intestinal epithelial cells (INT 407). 164 90

Lithium has been reported to alter thyroid function and cause goiter in some patients. To explain the mechanism of lithium action in the thyroid gland, we studied the effect of lithium on thyroid function and cell growth in FRTL-5 rat thyroid cells and on de novo thyroid hormone formation in primary cultures of porcine thyroid follicles. TSH-induced iodide uptake was suppressed at 2 mM lithium in both FRTL-5 cells and porcine follicles. In porcine thyroid follicles, iodide uptake stimulated by 8-bromo-cAMP, iodine organification, and de novo thyroid hormone formation were also reduced by lithium; however, 2 mM lithium did not inhibit TSH-induced cAMP production. In FRTL-5 cells, lithium also inhibited forskolin-stimulated iodide uptake. These results suggested that lithium exerts its effect at a step involving cAMP signal transduction rather than inhibiting cAMP production. In both FRTL-5 thyroid cells and porcine follicles, lithium enhanced cell growth in basal states (lacking TSH) and with TSH treatment. In porcine thyroid cells, the protein kinase C activator, tetradecanoyl phorbol-13-acetate, increased cell growth, and lithium had an additive effect with tetradecanoyl phorbol-13-acetate on cell growth. To examine the possibility that the action of lithium was mediated by the protein kinase C pathway, porcine cells were incubated with lithium and H7, a selective protein kinase C inhibitor. Lithium-induced cell growth was suppressed to the basal level by H7. These results suggest that lithium exerts its growth-promoting effect through the protein kinase C system.
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PMID:Effect of lithium on function and growth of thyroid cells in vitro. 164 47

We have previously demonstrated that platelet-activating factor (PAF) binds specifically on cell membranes isolated from U937 cells. We now describe biological evidence showing that the effect of PAF on U937 cells is a receptor-mediated event. myo-[3H]Inositol-labeled U937 cells were used to investigate the possible role of phosphoinositide metabolism in these cells after binding of PAF. Formation of inositol phosphates (IP1, IP2, and IP3) in response to PAF was increased two- to threefold more than in vehicle control in U937 cells. The effect of PAF on endogenous protein phosphorylation was also studied by using 32PO4-labeled cells. PAF stimulates the phosphorylation of a 45-kDa protein in a time-dependent and dose-related fashion. Since the phospholipase C-generated diglyceride is an important activator of protein kinase C, the phosphorylated 45-kDa protein could be the substrate of protein kinase C. In this regard, we were able to demonstrate that phorbol ester enhances the phosphorylation of the same 45-kDa protein band. In addition, sphingosine, a protein kinase C inhibitor, inhibits the phosphorylation of the same 45-kDa protein band. Down-regulation of the protein kinase C also inhibits the 45-kDa protein phosphorylation. These results suggest that protein kinase C is involved in the PAF-U937 cell interaction.
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PMID:Activation mechanisms of platelet-activating factor in U937 cells: possible involvement of protein kinase C. 165 12

One might predict that cytochalasin D, which slows polymerization of actin in solution and which inhibits actin-containing microfilament function in live B lymphocytes, would also prevent actin polymerization in these cells. However, we have used the NBD-Phallacidin flow cytometric assay for F-actin and the DNase I inhibition assay for G-actin to demonstrate that cytochalasin D (at 20 micrograms/ml and higher) stimulates actin polymerization in murine B lymphocytes within the first 30 sec of exposure. A similar response was seen in human neutrophils. Actin polymerization induced in neutrophils by chemotactic peptides has been linked to activation of the polyphosphoinositide-calcium increase-protein kinase C signal transduction pathway. As B lymphocytes also transduce signals using this pathway, we investigated whether cytochalasin D induced actin polymerization by activating this pathway. Cytochalasin D and ionomycin both stimulated a rapid increase in internal calcium (by 1 min) in the B cell which was inhibitable by EGTA, implicating calcium influx. Ionomycin also induced actin polymerization, detectable later, by 10 min. EGTA blocked the ionomycin-induced actin polymerization, but not that induced by cytochalasin D. Cytochalasin D-induced actin polymerization was not associated with detectable hydrolysis of polyphosphoinositides, nor was it inhibited by H7 (a protein kinase C inhibitor) or by HA1004 (an inhibitor of cyclic nucleotide-dependent kinases). Furthermore, anti-immunoglobulin antibodies, which stimulate B lymphocytes through the polyphosphoinositide hydrolysis-calcium increase-protein kinase C pathway, failed to induce actin polymerization in these cells. These antibodies did, however, stimulate the cells to perform activities that involve actin-containing microfilaments. Other primary activators of B lymphocytes (dextran sulfate, PMA, and LPS) and a panel of lymphokines previously shown to enhance B lymphocyte activation (IL-1, IL-2, IL-4, IL-5) were also screened in the F-actin assay and no evidence for actin polymerization was found. We conclude that the actin polymerization response to cytochalasin D in the B cell does not involve the polyphosphoinositide hydrolysis-calcium increase-protein kinase C pathway, nor does it depend on cyclic nucleotide-dependent kinases. Furthermore, our studies failed to provide any evidence that early actin polymerization occurs in murine B lymphocyte activation.
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PMID:Actin polymerization in murine B lymphocytes is stimulated by cytochalasin D but not by anti-immunoglobulin. 165 14

Neonatal mouse cardiac poly(A)+ mRNA microinjection into Xenopus oocytes directed the expression of a delayed rectifier K+ current. A cDNA encoding this channel, called mIsK, was cloned from a neonatal mouse heart cDNA library whose properties were studied after expression of the complementary RNA in Xenopus oocytes. Among the different known K+ channel blockers, only the class III antiarrhythmic clofilium inhibited mIsK in the 10-100 microM range. The channel was completely insensitive to other antiarrhythmics such as quinine, quinidine, sotalol or amiodarone. mIsK was enhanced by increasing intracellular Ca2+ and by microinjected Ca(2+)-calmodulin dependent protein kinase II. These stimulations were reversed by the calmodulin antagonist W7. Conversely, the phorbol ester PMA, the diacylglycerol analog OAG and microinjected purified protein kinase C inhibited mIsK. This inhibitory effect could be prevented by the protein kinase C inhibitor staurosporine. These results were consistent with the presence of consensus sequences for kinase II and kinase C in the mIsK structure. Cultured newborn mouse ventricular cardiac cells exhibited a delayed rectifier K+ current which had biophysical properties similar to those of cloned mIsK and which was inhibited by clofilium and protein kinase C activators. In situ hybridization experiments revealed that mIsK mRNA was homogeneously distributed in the cardiac tissue. Neonatal mouse heart expressed the most mIsK mRNA compared with various other rat and mouse tissues. Since this K+ channel generates a current which appears to be involved in the control of both the action potential duration and the beating rate, these results suggest an important role for the mIsK channel in cardiac cell physiology and cardiac pathology.
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PMID:Cloning, expression, pharmacology and regulation of a delayed rectifier K+ channel in mouse heart. 165 3

The effects of a potent phosphatase inhibitor, calyculin A (CL-A), on inward currents in guinea pig taenia coli smooth muscle cells were examined. CL-A increased the inward current, and this effect of CL-A was inhibited by a protein kinase C inhibitor, H-7, and by nifedipine. Phorbol 12,13-dibutyrate, an activator of protein kinase C, also increased the inward current and this effect was antagonized by H-7. These results suggest that in guinea pig taenia coli smooth muscle cells CL-A may facilitate the opening of the L-type Ca2+ channels through the protein kinase C-dependent phosphorylation system.
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PMID:Calyculin A increases voltage-dependent inward current in smooth muscle cells isolated from guinea pig taenia coli. 165 14


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