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)

Ligation of Ag receptors in T and B lymphocytes initiates signal transduction cascades which alter the expression of genes that regulate cellular proliferation and differentiation. The transmission of signals from the membrane to the nucleus is mediated principally through the action of protein tyrosine and serine/threonine kinases. We have identified and characterized a novel serine/threonine kinase that phosphorylated the proto-oncogene product, c-Fos, and is termed Fos kinase. Fos kinase was rapidly activated after ligation of the CD3 and CD2 receptors in Jurkat and normal human T lymphocytes and in response to IL-6 and anti-IgM in the human B cell lines AF10 and Ramos, respectively. The phorbol ester, PMA, was also a potent inducer of Fos kinase activity in all of the above populations, suggesting that PKC plays a role in the regulation of this enzyme. Fos kinase phosphorylates c-Fos at a site near the C-terminus, as well as a peptide derived from this region (residues 359-370, RKGSSSNEPSSD), and Fos peptide competitively inhibited c-Fos phosphorylation. Fos kinase was shown to be distinct from other identified serine/threonine kinases, including protein kinase A, protein kinase C, casein kinase II, MAP kinases, p70S6K and p90RSK. Fos kinase was purified by anion exchange chromatography and exhibited an apparent M(r) = 65,000 and isoelectric point = 6.1. Fos kinase may play a role in transcriptional regulation through its capacity to phosphorylate c-Fos at a site required for expression of the transcriptional transrepressive activity of this molecule. Moreover, its rapid activation suggests it may have a wider role within signal transduction cascades in lymphocytes.
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PMID:Activation of a novel serine/threonine kinase that phosphorylates c-Fos upon stimulation of T and B lymphocytes via antigen and cytokine receptors. 815 58

In this report we show that interferon gamma treatment of U937 cells induces increased expression of the gamma-subunit of the high-affinity Fc receptor for IgG (Fc gamma RI). Interferon treatment results in a 10-fold increased expression of the gamma-subunit and induces expression of a phosphorylated form (gamma 1). The increased expression of the gamma-subunit correlates with its ability to transmit a signal via Fc gamma R, as measured by activation of the respiratory burst using insoluble immune complexes. During Fc gamma R activation, a mobility shift occurs in the phosphorylated form of this gamma 1-subunit. Phosphoamino acid analysis demonstrates that this gamma 1 subunit is threonine phosphorylated in resting differentiated U937 cells and becomes predominantly serine phosphorylated on Fc receptor activation. The mobility shift in the gamma-subunit can be induced by treating U937 cells with phorbol 12-myristate 13-acetate or by monoclonal antibody cross-linking of Fc gamma RI. Hence the gamma-subunit is serine phosphorylated in response to Fc gamma RI and protein kinase C activation. Therefore the gamma-subunit, initially described as a subunit of Fc epsilon RI, now appears to be involved in signal transduction via Fc gamma RI. The data also suggest that the gamma-subunit, in contrast with the zeta-subunit of the T-cell receptor-CD3 complex, is a substrate for serine/threonine kinase(s) in the cell. The serine phosphorylation of the gamma-subunit suggests a divergence of structure and function between the gamma-subunit and its homologue, the zeta-subunit of the T-cell receptor. Phosphorylation of the gamma-subunit on serine may play some regulatory role in Fc gamma RI signal transduction in myeloid cells.
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PMID:Serine/threonine phosphorylation of the gamma-subunit after activation of the high-affinity Fc receptor for immunoglobulin G. 817 19

The fungal metabolite BE-23372M is a structurally novel protein kinase inhibitor. Its IC50 for epidermal growth factor (EGF) receptor kinase was 0.03 microM. IC50 values of BE-23372M for other protein tyrosine kinases, erbB-2, p43v-abl, insulin receptor kinase, and p60c-src were 0.42, 1.0, 3.3, and 4.5 microM, respectively, and the IC50 for protein kinase C, a serine/threonine kinase, was 4.1 microM. Cdc2 kinase, casein kinases I and II and cAMP-dependent protein kinase were not inhibited by 20 microM BE-23372M. A kinetic study showed that BE-23372M was competitive with respect to the substrate peptide and to ATP. Autophosphorylation of solubilized EGF receptor kinase was clearly inhibited by 0.1 microM BE-23372M. Autophosphorylation of EGF receptor in A431 cells was also inhibited. These results show that BE-23372M is a potent and specific EGF receptor kinase inhibitor. It should be a valuable tool for EGF receptor kinase research.
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PMID:BE-23372M, a novel and specific inhibitor for epidermal growth factor receptor kinase. 818 23

It has previously been shown in T cells that stimulation of protein kinase C (PKC) or the T cell antigen receptor (TCR) induces the rapid accumulation of the active guanosine triphosphate-bound form of p21ras. These stimuli also induce the activation of extracellular signal-regulated kinase 2 (ERK2), a serine/threonine kinase that is rapidly activated via a kinase cascade in response to a variety of growth factors in many cell types. In this study, we show that p21ras is a component of the TCR signaling pathway that controls ERK2 activation. In the human Jurkat T cell line, transient expression of constitutively active p21ras induces ERK2 activation, measured as an increase in the ability of an ERK2-tag reporter protein to phosphorylate myelin basic protein. Thus, constitutively active p21ras bypasses the requirement for PKC activation or TCR triggering to induce ERK2 activation. In addition, activation of PKC or the TCR produces signals that cooperate with activated p21ras to stimulate ERK2. Conversely, expression of a dominant negative mutant of ras, Ha-ras N17, blocks ERK2 activation after TCR stimulation, indicating that endogenous p21ras function is necessary for the TCR-stimulated ERK2 activation. Taken together, these results demonstrate that the activation of p21ras is both necessary and sufficient to induce ERK2 activation in T cells.
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PMID:p21ras couples the T cell antigen receptor to extracellular signal-regulated kinase 2 in T lymphocytes. 837 29

IL-6 is a multi-functional cytokine that utilizes 80-kDa ligand-binding and 130-kDa signal-transducing subunits to stimulate diverse cellular responses. Although IL-6R ligation has been associated with tyrosine protein phosphorylation and activation of an unidentified serine/threonine kinase, very little is known about the intermediary signaling events between the cell membrane and the nucleus. rIL-6 treatment of the human B cell line, AF-10, induced MAP kinase (mitogen-activated protein kinase) activity as determined by in vitro phosphorylation of microtubule-associated protein-2 (MAP-2) and the synthetic peptide APRTPGGRR, corresponding to amino acids 95-98 of bovine myelin basic protein. The kinetics of the response was rapid and dependent on the dose of rIL-6. The response was cytokine specific, did not require the presence of extracellular Ca2+, and was minimally affected by the presence of staurosporine. MAP kinase activation in AF-10 cells occurred in parallel with appearance of 42- and 44-kDa tyrosine phosphoproteins (p42 and p44). Moreover, MAP kinase activation was diminished when AF-10 cells were stimulated with rIL-6 in the presence of tyrosine protein kinase inhibitors, genistein and geldanomycin. p42 and p44 co-electrophoresed on SDS-PAGE with extracellular signal-related kinase (ERK)-2, and ERK-1, respectively; both are members of the ERK family. In addition to p42MAPK and p44MAPK, rIL-6 also activated a MAP-2 kinase that eluted at a lower salt concentration (20 to 60 mM NaCl, peak I) from Mono-Q resin than p42MAPK (120 to 180 mM NaCl, peak II). The identify of this kinase is unknown but it is not an MPB kinase or a protein that exhibits immunoreactivity with anti-ERK antisera. In another IL-6-responsive B cell line, SKW6.4, rIL-6-activated peak I MAP-2 kinase but failed to activate ERK-2. The protein kinase C agonist, PMA, did, however, activate ERK-2 in SKW6.4 cells. These results show that the pleiotrophic cytokine, IL-6, activates p42MAPK/ERK-2 and at least one other serine/threonine kinase in B cell lines.
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PMID:Recombinant IL-6 activates p42 and p44 mitogen-activated protein kinases in the IL-6 responsive B cell line, AF-10. 838 18

To investigate the mechanism underlying resistance to tumour necrosis factor-alpha (TNF alpha)-induced cytotoxicity, we have developed a human hybrid cell line, designated A10, derived from the fusion of human U-937 monocytoid cells and human monocytes, which expressed large numbers of TNF alpha receptors and yet remained highly resistant to TNF alpha. However, in the presence of the protein kinase C (PKC) inhibitors RO-31-7549 or RO-31-8220 (donated by Roche), these cells became sensitive to TNF alpha-induced cytotoxicity, suggesting that PKC activity is required for protective mechanisms. On investigation of protein phosphorylation in TNF alpha-stimulated permeabilized A10 cells, a rapid increase in serine/threonine phosphorylation of phosphoproteins of molecular masses 130, 90, 80, 65 and 42 kDa was found. Subsequently, we found a similar pattern of increased phosphorylation following stimulation of A10 cells with mezerein, a phorbol ester derivative which activates PKC, a serine/threonine kinase. The theory that activation of PKC was responsible for increased phosphorylation was confirmed by a dose-dependent inhibition of the TNF alpha-induced protein phosphorylation by the PKC inhibitors RO-31-7549 and RO-31-8220. The possible link between the TNF alpha-stimulated early protein phosphorylation events and the maintenance of protective mechanisms against TNF alpha-induced cytotoxicity is discussed.
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PMID:Protein kinase C-dependent phosphorylation is involved in resistance to tumour necrosis factor-alpha-induced cytotoxicity in a human monocytoid cell line. 838 29

p74raf-1, a serine/threonine kinase, is structurally related to the protein kinase C (PKC) family and contains a cysteine motif in its N-terminal domain, which is essential for its regulation. It has been shown that p74raf-1 functions upstream of mitogen-activated protein (MAP) kinase kinase. We have constructed a p74raf-1 mutant (N delta raf) that only contains the N-terminal regulatory domain. When transiently expressed in COS-M6 cells, N delta raf efficiently blocked the activation of the MAP extracellular signal regulated kinase (ERK2), induced by either epidermal growth factor, phorbol ester, serum, or oncogenic p21ras. Similar constructs with the cysteine motifs from either PKC-alpha or diacylglycerol kinase did not inhibit activation of ERK2. Overexpression of full-length p74raf-1 rescued the inhibition of ERK2 by N delta raf in a stimulus dependent manner, indicating that N delta raf acts as a competitive inhibitor of wild-type p74raf-1. In contrast, overexpression of either PKC-alpha, -epsilon, or -zeta in N delta raf-containing cells could not rescue the inhibition of ERK2. We conclude that p74raf-1 is an essential mediator of epidermal growth factor- and phorbol ester-induced ERK2 activation and that the MAP kinase kinase activity of p74raf-1 cannot be substituted with either PKC-alpha, -epsilon or -zeta.
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PMID:A dominant-negative mutant of raf blocks mitogen-activated protein kinase activation by growth factors and oncogenic p21ras. 839 1

Previous studies have demonstrated that treatment of human U-937 myeloid leukemia cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) is associated with growth arrest and induction of monocytic differentiation. The present work describes the isolation of a U-937 cell variant, designated TUR, which is unresponsive to the growth-inhibitory effects of this agent. The results demonstrate that, in contrast to U-937 cells, the TUR line fails to respond to TPA with induction of the c-jun, junB, c-fos, and EGR-1 early response genes. The finding that these cells also fail to exhibit adherence or induction of the tumor necrosis factor and c-fms genes further supports their resistance to TPA-induced differentiation. In contrast, TUR cells responded to 1,25-dihydroxyvitamin D3, another inducer of monocytic differentiation, with growth arrest and induction of early response gene and c-fms transcripts. TUR cells also responded to okadaic acid, an inhibitor of type 1 and 2A protein phosphatases, with similar changes in gene expression. Further characterization of TUR cells has demonstrated decreased expression of protein kinase C as compared to wild-type U-937 cells. We also demonstrate that although treatment of U-937 cells with TPA is associated with activation of the Raf-1 serine/threonine kinase, there was no detectable decrease in electrophoretic mobility of this protein in TPA-treated TUR cells. Taken together, these findings indicate that the TUR variant is defective in TPA-induced signaling events upstream to activation of Raf-1 kinase.
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PMID:Resistance to phorbol ester-induced differentiation of a U-937 myeloid leukemia cell variant with a signaling defect upstream to Raf-1 kinase. 839 7

The c-Raf-1 serine/threonine kinase is an important component of signal transduction pathways mediating the effects of a variety of growth factors. In activated T cells, IL-2 has been shown to induce activation of c-Raf-1, but c-Raf-1 has not previously been shown to be activated through the T-cell receptor (TCR) in resting G0 T cells. Using a sensitive immune complex kinase reaction, we show that cross-linking of the stimulatory and costimulatory receptors CD3, CD4, or CD28 induces c-Raf-1 activation in highly purified resting peripheral blood human T cells. In contrast, cross-linking the nonstimulatory receptor CD45 did not induce c-Raf-1. Surprisingly, although earlier studies had shown delayed kinetics in response to Thy-1 stimulation in murine cells, c-Raf-1 activation in response to CD3 cross-linking was one of the earliest measurable events. In spite of its early kinetics, c-Raf-1 activation was found to be downstream of several other early signal transduction events, including activation of a tyrosine kinase and a tyrosine phosphatase. Several lines of evidence suggest that activation of c-Raf-1 in response to TCR stimulation may be PKC-dependent: first, phorbol esters are extremely potent activators of c-Raf-1 in human T cells; second, the kinetics of accumulation of products of phosphatidylinositol hydrolysis coincides with the kinetics of c-Raf-1 activation; and third, physiologic activation of the PLC/PKC pathway through a transfected, G-protein-coupled receptor HM1 induced similar levels of c-Raf-1 activation with a similar time course. We conclude that c-Raf-1 activation is tightly coupled to TCR stimulation and may participate in signal transduction pathways in resting, G0 T cells. The observation that the HM1 receptor can also activate c-Raf-1 suggests that T cells have the capability to utilize both tyrosine kinase-dependent and tyrosine kinase-independent mechanisms of c-Raf-1 activation.
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PMID:Rapid activation of C-Raf-1 after stimulation of the T-cell receptor or the muscarinic receptor type 1 in resting T cells. 840 89

Raf-1 is a serine/threonine kinase which is essential in cell growth and differentiation. Tyrosine kinase oncogenes and receptors and p21ras can activate Raf-1, and recent studies have suggested that Raf-1 functions upstream of MEK (MAP/ERK kinase), which phosphorylates and activates ERK. To determine whether or not Raf-1 directly activates MEK, we developed an in vitro assay with purified recombinant proteins. Epitope-tagged versions of Raf-1 and MEK and kinase-inactive mutants of each protein were expressed in Sf9 cells, and ERK1 was purified as a glutathione S-transferase fusion protein from bacteria. Raf-1 purified from Sf9 cells which had been coinfected with v-src or v-ras was able to phosphorylate kinase-active and kinase-inactive MEK. A kinase-inactive version of Raf-1 purified from cells that had been coinfected with v-src or v-ras was not able to phosphorylate MEK. Raf-1 phosphorylation of MEK activated it, as judged by its ability to stimulate the phosphorylation of myelin basic protein by glutathione S-transferase-ERK1. We conclude that MEK is a direct substrate of Raf-1 and that the activation of MEK by Raf-1 is due to phosphorylation by Raf-1, which is sufficient for MEK activation. We also tested the ability of protein kinase C to activate Raf-1 and found that, although protein kinase C phosphorylation of Raf-1 was able to stimulate its autokinase activity, it did not stimulate its ability to phosphorylate MEK.
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PMID:Reconstitution of the Raf-1-MEK-ERK signal transduction pathway in vitro. 841 57


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