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)

Sequential stimulation and washout procedures were employed to examine the kinetics and reversibility of pharmacologically manipulated second messenger signals mediating phenotypic changes and proliferative activation of resting human T lymphocytes. Phorbol dibutyrate (PDBu) was used to stimulate protein kinase C (Ca2+/phospholipid-dependent enzyme) while ionomycin was used to manipulate intracellular Ca2+ levels. Stimulation by PDBu alone induced phosphorylation of several endogenous substrates and altered expression of phenotypic markers, downregulating expression of CD4 and CD3 while increasing expression of CD2 and the interleukin 2 (IL-2) receptor. Stimulation with ionomycin alone caused an increase in intracellular Ca2+ levels but did not induce proliferation or cause major changes in the expression of phenotypic markers (CD2, CD3, CD4, CD8, IL-2, and transferrin receptors). Analysis of endogenous PDBu stimulated phosphosubstrates indicated that some substrates (pp92, pp82, pp55) underwent dephosphorylation, returning to base-line levels following PDBu removal while others (pp61, pp65) showed only partial dephosphorylation, while one (pp28) remained phosphorylated. Washing ionomycin-stimulated cells resulted in an approximately 75% reduction of intracellular Ca2+. Ionomycin exposure did not alter the affinity (KD = 22.3 +/- 7.4 nM) or number of receptors (53,497 +/- 8,291 receptors/cell) for [3H]PDBu. These data suggest that signals induced by PDBu or ionomycin are reversible following removal of the stimulating agents with respect to proliferative activation of T lymphocytes. Furthermore, a transcriptional mechanism regulating the production of IL-2 mRNA requires simultaneous activation of protein kinase C and elevation of intracellular Ca2+.
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PMID:Coordination and reversibility of signals for proliferative activation and interleukin-2 mRNA production in resting human T lymphocytes by phorbol ester and calcium ionophore. 326 69

We have investigated the induction of competence (IL-2 responsiveness) and progression in human T lymphocyte proliferation triggered by phorbol ester and calcium ionophore. The degree of proliferation induced with the phorbol ester, phorbol 12,13-dibutyrate (PDB) and the calcium ionophore ionomycin was dependent on the duration of exposure to these agents, with more than 6 h required for obtaining maximum proliferation. Following brief exposure to both agents for 30 min, which did not cause significant proliferation, T cells became competent to proliferate in response to exogenous interleukin 2 (IL-2). These competent T cells also progressed to DNA synthesis following incubation with PDB in the absence of ionomycin. Induction of competence to proliferate in response to either PDB or IL-2 was blocked by EGTA, suggesting that transmembrane Ca2+ flux was obligatory at this stage. Since other phorbol esters and synthetic diacylglycerols also stimulated DNA synthesis in competent cells, it is likely that progression was triggered by activation of protein kinase C. Following a brief exposure to PDB and ionomycin, subsequent incubation with PDB induced gene expression and secretion of IL-2 and augmented the expression of IL-2 receptors in the competent cells. Thus, we have demonstrated that Ca2+ mobilization is required for rendering T cells competent to express functional IL-2 receptors, to produce IL-2 in response to subsequent incubation with PDB, and that sustained activation of protein kinase C seems necessary for IL-2 production and subsequent progression of competent T cells to DNA synthesis.
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PMID:Induction of competence and progression signals in human T lymphocytes by phorbol esters and calcium ionophores. 326 71

The role that extracellular calcium plays in activating resting cloned cytotoxic T lymphocytes (CTL) to proliferate and to produce lymphokines was examined. In these cells, stimulation with interleukin 2 (IL-2) induced a proliferative response without a concomitant production of macrophage-activating factor (MAF), whereas stimulation with antigen or lectin (in the absence of IL-2) induced MAF production but not proliferation. In the case of IL-2-induced proliferation, extracellular calcium was required to initiate proliferation as well as to prevent cellular arrest later in the G2 + M phase of the cell cycle. In MAF production extracellular calcium was required both to activate the phosphatidylinositol signal-transducing mechanism and to mobilize intracellular calcium in antigen- or lectin-stimulated cytotoxic T lymphocytes. Further, extracellular calcium was required for only 8 of the 18 hr of stimulation time which was needed to achieve maximal MAF production, indicating that both calcium-dependent and -independent events exist in the signal pathway. Additional experiments with calcium ionophores and activators of protein kinase C indicated that although both intracellular calcium mobilization and de novo protein phosphorylation are involved in MAF production, an optimal increase in the level of intracellular calcium by itself is insufficient to induce the production of this lymphokine.
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PMID:Molecular mechanisms involved in T cell activation. III. The role of extracellular calcium in antigen-induced lymphokine production and interleukin 2-induced proliferation of cloned cytotoxic T lymphocytes. 327 84

Experimental results of induction of T-lymphocyte proliferation by means of tumor promotors-activators of protein kinase C (PKC) are reviewed. A hypothesis has been put forward that the discrepancy of the data so far available can be explained on the account of the difference in membrane-associated PKC activation patterns produced by tumor promotors and by interleukin 2. It is established that the former induce a permanent PKC activation, whereas the latter induces a transient one. Although enhancing DNA synthesis, the permanent (non-physiological) activation must induce an accumulation of cells in the cell cycle phases following the S-phase.
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PMID:[Possible role of protein kinase C in the T-lymphocyte cell cycle]. 331 52

We have investigated interleukin 2 (IL-2)-induced protein phosphorylation in an IL-2 dependent murine cell line by the two-dimensional gel electrophoresis. IL-2 rapidly and markedly induced phosphorylation of a cellular protein distinct from the IL-2 receptor, with a molecular weight of 67,000 daltons and an isoelectric point of 5.8, named pp67. IL-2 dose-responses of pp67 phosphorylation and cell proliferation were well correlated. Phosphoamino acid analysis showed that the phosphorylation site of pp67 was a serine residue. Further, when the cells were treated with 12-O-tetradecanoylphorbol-13-acetate (TPA) instead of IL-2, similar increase of pp67 phosphorylation was observed. Such IL-2 dependent protein phosphorylation was also detected in various human IL-2 receptor bearing T cells. Thus we speculate that the phosphorylation of pp67 could be regulated by protein kinase C and it could be a common feature in an early event of the intracellular growth signaling from the IL-2 receptor.
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PMID:Interleukin 2 (IL-2) rapidly induces phosphorylation of a cellular protein, pp67, in an IL-2 dependent murine cell line. 348 73

Phorbol myristate acetate (PMA) at concentrations of 2 X 10(-10) to 2 X 10(-7) M was able to sustain proliferation of the interleukin 2 (IL-2)-dependent murine T-cell line CTLL-K. This line, which died within 24 hr without exogenously added IL-2, survived for at least 96 hr and completed two to three cycles of replication in the presence of an optimal dose of PMA. PMA did not increase proliferation induced by saturating amounts of IL-2, but it mimicked IL-2 activity when no IL-2 or only suboptimal doses of IL-2 were present. This effect was completely independent of any residual IL-2 activity and was not mediated by the endogenous production of IL-2. The finding that stimulation of CTLL-K cells with 1-oleoyl-2-acetyl-glycerol or 1,2-dioctanoyl-glycerol rather than with PMA was not sufficient to induce any proliferation suggests that diacylglycerols and phorbol esters have qualitatively different effects on protein kinase C activity. Falsely positive results could occur when IL-2-dependent T-cell lines were used as indicator cells for IL-2, since evidence is presented that PMA-responsive cells could emerge spontaneously from T-cell clones that originally were not responsive or only weakly influenced by PMA.
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PMID:Phorbol myristate acetate-induced proliferation of an IL-2-dependent T-cell line: action of PMA is independent of IL-2 and cannot be mimicked by diacylglycerols. 349 76

Tumor-promoting phorbol esters (PE) can modulate cellular functions and cell surface determinant expression in a variety of cell types, including T lymphocytes, presumably by activating the enzyme, protein kinase C (PKC). To examine whether PKC might be involved in regulating the expression of genes encoding the antigen-specific T cell receptor (TCR), we cultured the murine thymoma line, EL4, in the presence of 12-O-tetradecanoylphorbol 13-acetate (TPA) and analyzed the expression of TCR alpha or beta-chain genes by Northern blots. TPA stimulation of an interleukin 2 (IL 2)-producing variant, EL4+, induced a 3-4-fold increase in TCR beta, but not alpha, chain mRNA. Maximal increase was obtained with 3 ng/ml TPA and 12 h of stimulation. This effect appeared related to PKC activation because other tumor-promoting PE known to be PKC activators, but not inactive PE, induced the same increase. TPA stimulation of EL4+ cells also induced de novo expression of the IL 2 gene and subsequent secretion of this lymphokine. However, the increased expression of the TCR beta-chain gene and the induction of the IL 2 gene were not linked since expression of TCR beta-chain mRNA was increased to a similar degree in EL4+ and IL 2-nonproducing EL4- sublines, and cyclosporin A selectively blocked TPA-induced IL 2-gene expression in EL4+ cells without affecting the increase in TCR beta-chain mRNA. These findings suggest that PKC activation, an event that supposedly occurs after antigen-mediated triggering of the TCR, can regulate the expression of at least some of the genes encoding this receptor.
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PMID:Protein kinase C-activating phorbol esters augment expression of T cell receptor genes. 349 24

The role of major histocompatibility complex-encoded class I molecules in the proliferation of human B lymphocytes is presently unclear. This question was addressed by investigating the effect of three individually derived anti-HLA class I monoclonal antibodies (mAb) on purified human B cells (less than 1.5% T cells) stimulated by either the T-independent mitogen Staphylococcus aureus or the phorbol ester, phorbol-12-myristate-13-acetate. The three anti-HLA class I antibodies, whether specific for gene products of the HLA-A locus (mAb 131), HLA-B locus (mAb 4E), or HLA-A, -B, and -C locus (mAb W6/32), inhibited S. aureus-induced proliferation by 70 to 90%. This inhibition was significant over a 5-day culture period, was not altered by the addition of exogenous interleukin 2 or B cell growth factor, and was not due to nonspecific cytotoxicity. In addition, the inhibition of proliferation was unchanged when the mAb were added 12 hr after the initiation of culture. The proliferative response was not affected by either of the control antibodies OKB7 and R3-367. In contrast with S. aureus-stimulated B cells, phorbol-12-myristate-13-acetate-induced proliferation was resistant to the inhibitory activity of HLA class I-specific antibodies. These results suggest that HLA class I molecules are involved in human B lymphocyte proliferation and may regulate a critical event preceding the upregulation of protein kinase C activity.
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PMID:Anti-HLA class I antibodies inhibit the T cell-independent proliferation of human B lymphocytes. 349 78

The haematopoietic growth factors multi-colony-stimulating factor, granulocyte/macrophage colony-stimulating factor, granulocyte colony-stimulating factor and interleukin 2 specifically control the production and proliferation of distinct leucocyte series. Each growth factor acts on a unique surface receptor associated with an appropriate signal-transduction apparatus. In this report we identify a 68 kDa substrate which is phosphorylated after stimulation of different cell types with multi-colony-stimulating factor, granulocyte colony-stimulating factor and interleukin 2. The 68 kDa substrate is also phosphorylated in each cell line stimulated with synthetic diacylglycerol, a direct activator of protein kinase C. Interestingly, granulocyte/macrophage colony-stimulating factor does not induce phosphorylation of the 68 kDa molecule. The 68 kDa molecule that is phosphorylated after stimulation with each ligand yielded similar peptide maps after chymotryptic digestion; furthermore, the substrate was always phosphorylated on threonine residues. Phosphorylation of the same residues in the 68 kDa substrate suggests that activation of protein kinase C is one common signal-transduction event associated with the action of multi-colony-stimulating factor, granulocyte colony-stimulating factor and interleukin 2.
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PMID:Identification of a signal-transduction pathway shared by haematopoietic growth factors with diverse biological specificity. 350 46

Phorbol esters trigger production of interleukin 2 by EL4 thymoma cells via an interaction with specific receptors, now considered to be identical with protein kinase C. Several in vitro substrates for protein kinase C were characterized by incubating cytosol from phorbol ester-responsive and -nonresponsive cells with [32P]adenosine triphosphate and CaCl2 with or without phosphatidylserine and diolein and separating proteins by gel electrophoresis. Phosphorylation of these proteins was calcium dependent in the range of 1-100 microM and stimulated by 10-150 micrograms of phosphatidylserine per ml. Calcium concentrations above 500 microM inhibited 32P incorporation and decreased phospholipid stimulation. Phorbol-12-myristate-13-acetate stimulated phosphorylation of these proteins, with a maximal concentration of 10 nM, providing strong evidence that these are protein kinase C substrates. The substrates for protein kinase C coeluted with the enzyme after binding to a phosphatidylserine affinity column in a calcium-dependent manner. Molecular weights of the protein kinase C substrates in sensitive cell cytosol were approximately 92,000, 84,000, 70,000, 67,000, 53,000, 45,000, 40,000, 36,000, and 20,000. A similar EL4 line which has phorbol ester receptors and protein kinase C, but does not produce interleukin 2 in response to phorbol esters, lacked the Mr 45,000 substrate and often also lacked the Mr 40,000 and 36,000 substrates. These proteins were also analyzed by two-dimensional electrophoresis. These results provide evidence of differences in the two cell lines in the ability of some proteins to serve as substrates for protein kinase C. Four proteins in a highly purified preparation of protein kinase C, at molecular weights of 66,000, 74,000, and 78,000 (all with pI 6.5-7.1) and of 62,000 (pI 6.2-6.4), were protein kinase C substrates, one of which is probably protein kinase C.
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PMID:Substrates for protein kinase C in cytosol of EL4 mouse thymoma cells. 369 22


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