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)

Human interleukin-2 (IL-2) is a lymphokine which is capable of activating lymphocytes and supporting the long-term in vitro growth of activated T cell clones. Recombinant human IL-2, expressed in either E. coli or cos cells, was shown to be phosphorylated by protein kinase C. Phosphorylated IL-2 synthesized in E. coli was analyzed by SDS-PAGE, reverse phase HPLC, and tryptic peptide mapping. The phosphorylated tryptic peptide was identified as the N-terminal fragment containing a single phosphorylation site at the serine residue at position 7. There was no difference in biological activity between non-phosphorylated and phosphorylated IL-2, as determined by a T cell growth assay. Although the physiological role of phosphorylation of IL-2 is unclear, IL-2 can be labeled with [gamma-32P] ATP and protein kinase C to a high specific radioactivity, and the synthesis of biologically active 32p-labeled IL-2 may be useful for receptor-binding studies of the cells containing low level of phosphoprotein phosphotases.
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PMID:Phosphorylation of human interleukin-2 (IL-2). 278 33

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

We have identified a murine T lymphocyte clone that apparently lacks diacylglycerol- and phospholipid-activated protein kinase C (PKC): cell extracts do not display phosphatidylserine, Ca2+, or phorbol ester-dependent phosphotransferase activity; the enzyme was not detected in immunoblots with PKC-specific antibodies; phorbol ester binding sites are not detectable in intact cells; and activators of PKC do not stimulate proliferation or Na+/H+ exchange in intact cells. Only PKC beta mRNA was detected in normal murine T lymphocytes. The mutant T lymphocytes contained amounts of 4.4 kb PKC beta message similar to those in normal murine lymphocytes, but the 2.9 kb and 1.2 kb messages found in normal lymphocytes were barely detectable. No abnormalities were detected on Southern analysis, suggesting that the abnormality may be at the level of message splicing or stability. Since PKC-deficient cells proliferate in response to the T lymphocyte growth factor, interleukin-2, we conclude that activation of PKC is not essential for the growth-promoting action of interleukin-2.
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PMID:Interleukin-2 induces proliferation of T lymphocyte mutants lacking protein kinase C. 284 11

We investigated whether sn-1,2-dioctanoylglycerol (diC8) activates highly purified human T cells. diC8's signaling activity was also compared with that of 12-O-tetradecanoylphorbol-13-acetate (TPA). diC8 and ionomycin were synergistic in promoting T-cell proliferation. The proliferative response was dependent upon an operational interleukin-2 (IL-2) system and exhibited a high degree of specificity; sn-1,2-diC8 was twice as active as racemic-1,2-diC8, and diC8 and TPA were not synergistic. diC8's signaling activity differed from that of TPA. diC8, unlike TPA, failed to elicit IL-2 receptors or proliferation, independently of ionomycin. diC8 also failed to promote the proliferation of T cells signaled with anti-CD3 or -CD2 monoclonal antibodies. Two different inhibitors of PKC, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine or staurosporine, inhibited T-cell proliferation induced with diC8 and ionomycin, but not with TPA and ionomycin. These observations, in addition to demonstrating the differential activity of diC8 and TPA, document a signaling role for diacylglycerol in the activation of normal T cells.
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PMID:Activation of human T cells with the physiological regulator of protein kinase C. 290 30

The interleukin-2 (IL-2) receptor, the leukocyte-specific membrane glycoprotein, T200, and the class I major histocompatibility antigens (HLA) have been identified as substrates for protein kinase C in vitro. IL-2 receptors on normal human T lymphocytes and the leukemic cell line, HUT102B2, are rapidly phosphorylated in vivo in response to the tumor-promoting phorbol ester, 12-O-tetradecanoylphorbol 13-acetate (TPA). Tryptic peptide analysis showed that the in vitro and in vivo 32P-labeled IL-2 receptors were phosphorylated on the same sites. A synthetic peptide corresponding to the carboxyl-terminal cytoplasmic tail of the IL-2 receptor was shown to be phosphorylated in vitro by protein kinase C. Tryptic digestion of the peptide generated the same 32P-labeled species as those found for the IL-2 receptor. From these studies, it was concluded that Ser-247 is the major site of phosphorylation in the IL-2 receptor and that Thr-250 is a minor site. These results also provide direct evidence that the in vivo phosphorylation of the IL-2 receptor stimulated by TPA is catalyzed by protein kinase C. The sites phosphorylated in the HLA antigens in vitro by protein kinase C or in vivo after TPA stimulation were also localized to the carboxyl-terminal cytoplasmic domain of the heavy chain by limited proteolysis.
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PMID:Identification of lymphocyte integral membrane proteins as substrates for protein kinase C. Phosphorylation of the interleukin-2 receptor, class I HLA antigens, and T200 glycoprotein. 294 17

In vitro effects of three immunosuppressive drugs, cyclosporin, methylprednisolone, and 6-mercaptopurine (the active moiety of azathioprine), have been assessed by various proliferative assays including mixed lymphocyte reaction (MLR), concanavalin A (Con A), OKT3 monoclonal antibody (MoAb), phorbol myristate acetate (PMA), and A23187 ionophore-induced mitogenesis. The influence of these drugs on the capacity to produce interleukin-2 (IL-2) after phytohemagglutinin (PHA) induction has also been evaluated. Depending upon the nature of the stimulus used, differences were found among the three immunosuppressive drugs, suggesting that different T-cell activation mechanisms are involved. The response to alloantigens (MLR) or to mitogens (Con A and OKT3 MoAb) resulted in significant inhibition by all three immunosuppressive agents, although 6-mercaptopurine was somewhat less potent at the pharmacological concentration of 0.1 microgram/ml. When PMA (which activates cells through protein kinase C) and A23187 ionophore (which enhances Ca2+ influx into the cytoplasm through membrane channels) were used, dissociations were observed, suggesting that drugs act differentially on early stages of T-cell activation. Inhibition of PMA-induced activation by cyclosporin was very limited in contrast to the potent effect of methylprednisolone. The latter drug could thus preferentially affect an activation step involving the PMA receptor. Furthermore, the inhibitory influence of methylprednisolone on A23187 ionophore-induced proliferation was equivalent to that of cyclosporin, while 6-mercaptopurine had no effect except at the high concentration of 1 microgram/ml in which direct inhibition of DNA replication is probably involved. IL-2 production induced by PHA was strongly blocked by methylprednisolone and cyclosporin but not by 6-mercaptopurine, at least when a pharmacological concentration was used. In view of the relative independence of ionophore-induced activation from the influence of IL-2, this response could be linked to the intrinsic mechanism of antiproliferative activity of immunosuppressive drugs which probably act mostly at the level of IL-2 production. These results also provide a cellular approach to the synergies between immunosuppressive drugs. Most of the tests are more strongly affected by cyclosporin than by 6-mercaptopurine, probably explaining the potent steroid-sparing effect of cyclosporin.
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PMID:Differential in vitro actions of cyclosporin, methylprednisolone, and 6-mercaptopurine: implications for drugs' influence on lymphocyte activation mechanisms. 294 29

To further characterize the mechanisms responsible for defective interleukin-2 (IL-2) production in patients with systemic lupus erythematosus (SLE), we studied the effect of irradiation on the capacity of lymphocytes to produce this lymphokine when stimulated with phytohemagglutinin (PHA), or with a combination of PHA and a phorbol myristic acid ester (PMA). Irradiation increased PHA induced IL-2 production in patients with SLE and normal controls, and reached normal levels in 10 of 16 patients with SLE. This effect was due to inactivation of CD8+ suppressor cells. When PMA was used as a costimulant, maximal enhancement of IL-2 production was observed in both groups, but values in SLE remained significantly lower than in normals. These differences were not overcome by irradiation, raising the possibility that SLE suppressor cells act upon a site proximal to protein kinase C. Our studies have confirmed that active endogenous suppression may be responsible for most of the defective PHA induced IL-2 production in SLE and that this suppression is radiosensitive.
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PMID:Further characterization of interleukin-2 production by lymphocytes of patients with systemic lupus erythematosus. 297 35

The cyclic undecapeptide cyclosporine A (CsA) is a potent immunosuppressive agent that inhibits the initial activation of T lymphocytes. This agent appears to be most effective in blocking the action of mitogens such as concanavalin A and the calcium ionophore A23187, which cause an influx of Ca2+, but not those that may act by alternate mechanisms. These observations suggest that CsA may block a Ca2+-dependent step in T cell activation. We have shown that stimulation of the T3-T cell receptor complex-associated Ca2+ transporter activates the Na+/H+ antiport (Rosoff, P. M., and L. C. Cantley, 1985, J. Biol. Chem., 260: 14053-14059). The tumor-promoting phorbol esters, which are co-mitogenic for T cells, activate the exchanger by a separate pathway which is mediated by protein kinase C. Both the rise in intracellular Ca2+ and intracellular pH may be necessary for the successful triggering of cellular activation. In this report we show that CsA blocks the T3-T cell receptor-stimulated, Ca2+ influx-dependent activation of Na+/H+ exchange, but not the phorbol ester-mediated pathway in a transformed human T cell line. CsA inhibited mitogen-stimulation of interleukin-2 production in a separate cell line. CsA also inhibited vasopressin stimulation of the antiporter in normal rat kidney fibroblasts, but had no effect on serum or 12-O-tetradecanoyl phorbol 13-acetate stimulation. CsA did not affect serum or vasopressin or serum stimulation of normal rat kidney cell proliferation. CsA also had no effect on lipopolysaccharide or phorbol ester stimulation of Na+/H+ exchange activity or induction of differentiation in 70Z/3 pre-B lymphocytes in which these events are initiated by the protein kinase C pathway. These data suggest that mechanisms of activation of Na+/H+ exchange that involve an elevation in cytosolic Ca2+ are blocked by CsA but that C kinase-mediated regulation is unaffected. The importance of the Na+/H+ antiport in the regulation of growth and differentiation of T cells is discussed.
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PMID:Cyclosporine A inhibits Ca2+-dependent stimulation of the Na+/H+ antiport in human T cells. 301 82

The recombinant human interleukin-2 (IL-2) receptor was expressed in mouse mammary epithelial cells following the transfection of these cells with an expression vector containing the human IL-2 receptor cDNA. The recombinant IL-2 receptor in these cells was rapidly phosphorylated in response to phorbol myristate acetate (PMA), but its phosphorylation could not be detected in the absence of PMA or upon addition of human IL-2. The C-terminal, cytoplasmic peptide domain of the IL-2 receptor, Gln-Arg-Arg-Gln-Arg-Lys-Ser-Arg-Arg-Thr-Ile, was synthesized and used as a substrate for protein kinase C. The Km for phosphorylation of the peptide by protein kinase C was 23 microM. The stoichiometry of phosphorylation was 1 mol of phosphate/mol of peptide and serine was the predominant amino acid phosphorylated. Because this peptide was a good substrate for protein kinase C in vitro, it was possible that the same serine (serine 247) was also phosphorylated in the receptor in the cell. The IL-2 receptor gene in the expression vector was therefore altered by site-directed mutagenesis to code for an IL-2 receptor containing an alanine in the place of serine 247. The IL-2 receptor expressed by these cells was not phosphorylated in the presence of PMA. These data suggest that protein kinase C, in response to PMA, phosphorylates the C-terminal serine residue (serine 247) in the human IL-2 receptor.
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PMID:Phosphorylation of the human interleukin-2 receptor and a synthetic peptide identical to its C-terminal, cytoplasmic domain. 308 77

The purpose of these investigations was to compare the immunosuppressive mechanism of cyclosporine (CsA) with those of lipid-soluble local anesthetics and calmodulin antagonists. Chlorpromazine (CPZ) and pentobarbital (PB) both inhibit lymphocyte activation by attenuating sodium and potassium ion potentials. CPZ and N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide (W-7) can also block calcium-dependent activation processes by inhibition of calmodulin and protein kinase C. All four compounds were found to suppress human and murine lymphoproliferation to both alloantigen or mitogen in a dose-dependent and saturable manner. Exogenous interleukin-2 (IL-2) restored mitogenic responsiveness to cultures suppressed using W-7 and CsA, but not to lymphocytes suppressed with either CPZ or PB. Cytofluorographic analysis revealed that the degree of suppression in drug-treated lymphocytes was significantly correlated with the surface expression of receptors for transferrin and interleukin-2. Inhibition of IL-2 activation by PB was demonstrated to result from a blockade of the mitogenic growth factor signal using the IL-2-dependent cell line HT-2. Thus, the mechanism of action of cyclosporine can be differentiated from those of anesthetic immunosuppressants at the level of responsiveness to interleukin-2. The data support the hypothesis that cyclosporine may be an antagonist of calmodulin that selectively blocks early events in T lymphocyte activation leading to IL-2 synthesis, but does not inhibit the expression or function of the IL-2 receptor.
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PMID:Comparison of the immunosuppressive effects of cyclosporine, lipid-soluble anesthetics, and calmodulin antagonists. Response to exogenous interleukin 2. 309 93


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