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)

Bryostatins are macrocyclic lactones isolated from the marine bryozoan Bugula neritina. They are currently evaluated for putative antineoplastic activity. Bryostatins bind and activate protein kinase C (PK-C), the cellular receptor for the phorbol ester, and elicit PK-D-dependent cellular functions. Such functions include the expression of the interleukin-2 receptor (IL-2R). Northern blot hybridization with a human IL-2R and an IL-2 cDNA showed that bryostatin 1 (bryo 1), like the phorbol ester, PMA, activates the IL-2R gene. Activation with bryo 1 or PMA in the presence of a calcium ionophore, A23187, increased IL-2 message. These findings indicate that calcium mobilization is necessary for bryo 1 or PMA induced IL-2 gene expression. Unlike PMA, bryo 1 did not cause a vigorous proliferative response of T-lymphocytes unless A23187 was added to the cultures. A bryostatin congener, bryo 13, was inactive in the above assays. Short-term treatment of T-cells with bryo 1 and PMA resulted in an equivalent down-regulation of surface CD3 and CD4 receptors without affecting the CD8 receptor. Bryo 1 or PMA mediated expression of surface IL-2R and T-cell proliferation induced by bryo 1 or PMA were sensitive to inhibition by the PK-C antagonists staurosporine (Sts) and H-7. In contrast, CD4 and CD3 down-regulation were resistant to H-7, but could be blocked by Sts, although the Sts concentration required to block bryo 1 or PMA-induced down-modulation was 2.5-fold higher than required to inhibit IL-2R expression and T-cell proliferation. These results indicate that bryostatins activate T-cell through PK-C.
 ...
PMID:Activation of T-cells by bryostatins: induction of the IL-2 receptor gene transcription and down-modulation of surface receptors. 221 Sep 11

Human melanoma-specific, HLA restricted, cytotoxic T-cell lines can be generated by in vitro stimulation and culturing of peripheral lymphocytes, or lymph node cells, with autologous or HLA-A region matched melanomas in the presence of a low concentration (5 U/ml) of IL-2. Stimulation is followed by a period of clonal expansion and differentiation into cytotoxic T-cells specific for melanoma. We investigated the effect of the PKC modulating drug phorbol dibutyrate combined with the calcium ionophore Ionomycin on growth and differentiation of the cell lines. The growth of the T-cell lines was substantially augmented in the presence of the drugs with increases of 10-fold or more in clonal expansion by 3 weeks of culture. The cell lines were IL-2 dependent for growth in the presence or absence of the drugs and the phenotypic distribution remained predominantly CD3+ T-cells of mixed CD4 and CD8 phenotypes. In spite of the increased rate of growth in the presence of the drugs, autologous melanoma-specific cytotoxicity was almost completely abrogated in those cultures. The cells were, however, nonspecifically lytic in the presence of concanavalin A. The melanoma-specific cytotoxic response was completely restored following culture with IL-2 alone. The results suggest that the human tumor-specific cytotoxic T-cell response can be induced and amplified in the presence of immune modulating drugs.
 ...
PMID:Modulation of in vitro autologous melanoma-specific cytotoxic T-cell responses by phorbol dibutyrate and ionomycin. 229 96

The molecular signals required by resting (G0) B cells for the induction of cell cycle entry, IL-2 production, and high-affinity IL-2 receptor (IL-2R) expression were defined and the effects of incomplete activation signals on the subsequent response to complete signals were examined. Highly enriched rabbit peripheral blood B cells were activated with a calcium ionophore, ionomycin, and a protein kinase C (PKC) activating phorbol ester, phorbol myristate acetate (PMA). It was observed that cell cycle entry to early G1 was induced by either reagent acting alone, but both reagents were required to stimulate IL-2 production, IL-2R expression, and DNA synthesis. These effects of ionomycin and PMA were shown to be mediated by increased intracellular calcium ion concentration [Ca2+]i and PKC activation, respectively. Although, increased [Ca2+]i or PKC activation each led to cell cycle entry, the subsequent response of these preactivated cells to complete activation with both signals was different: Cells pretreated with PMA alone for up to 24 hr could progress further to DNA synthesis after the addition of ionomycin. In contrast, cells activated with ionomycin alone, or those cultured without any stimulus, progressively lost the ability to show DNA synthesis after complete activation. The failure to progress to DNA synthesis in these two cases was, however, differentially regulated by the ability of these cells to produce IL-2 and to express IL-2R. Ionomycin-pretreated cells retained the ability to produce IL-2 but showed about 70% reduction in the numbers of IL-2R; whereas cells cultured without any stimulus lost the ability to produce IL-2 after subsequent complete activation, but showed lesser reduction in IL-2R expression.
 ...
PMID:Molecular signals in B cell activation. I. Differential refractory effects of incomplete signaling by ionomycin or PMA relate to autocrine IL-2 production and IL-2R expression. 232 35

We report that sustained increase of intracellular calcium ion concentration and protein kinase C (PKC) activation maintained throughout the G1 phase of cell cycle do not provide sufficient signals to cause S-phase entry in rabbit B cells, and that additional signals transduced by IL-2 and IL-2 receptor interaction are essential for G1 to S transition. We have shown earlier that rabbit B cells can be activated to produce IL-2 and express functional IL-2 receptors after treatment with ionomycin and PMA. Herein we have compared the response of rabbit PBLs, which contain about 50% T cells, with those of purified B cells. After activation with ionomycin or PMA, comparable numbers of PBLs and B cells entered the cell cycle; but DNA synthesis by the PBL cultures was three to four times higher than that of cultures of purified B cells. Interestingly, IL-2 production by the PBL cultures was also three to four times higher than in B cell cultures, suggesting an involvement of IL-2 in inducing DNA synthesis in these cells. The hypothesis that IL-2, which is produced in early G1, acts in late G1 and is required for G1 to S transition in B cells was supported by the following observations: (i) IL-2 production by B cells was detected as early as 6 hr after activation and preceded DNA synthesis by at least 24 hr. (ii) B cell blasts in G1 (produced by treatment of resting B cells with ionomycin and PMA) showed DNA synthesis in response to IL-2, but showed very little DNA synthesis in response to restimulation with ionomycin and PMA. (iii) A polyclonal rabbit anti-human IL-2 antibody caused nearly complete inhibition of DNA synthesis by B cells activated by ionomycin and PMA. (iv) A PKC inhibitor, K252b, inhibited DNA synthesis in ionomycin and PMA-stimulated cells if added at the beginning of culture but was not inhibitory if added 16 hr later. We conclude that increased [Ca2+]i and PKC activation are not sufficient signals for G1 to S transition in B cells; entry into S is signaled by IL-2, and IL-2-mediated signal transduction probably does not involve increased [Ca2+]i or PKC activation.
 ...
PMID:Molecular signals in B cell activation. II. IL-2-mediated signals are required in late G1 for transition to S phase after ionomycin and PMA treatment. 232 36

Recently published reports suggest that the activation of protein kinase C (PKC) plays an important role in the activation pathway of many cell types. In this study, we examined the role of PKC in human T-cell proliferation, IL-2 production, and IL-2R expression, when cultured with the mitogen PHA, the PKC inhibitor H-7, and H-7 control HA1004. H-7 inhibited the PHA-stimulated [3H]thymidine uptake, IL-2 production, and IL-2R expression in a dose-related manner. Further, we found H-7 inhibited T-cell proliferation, IL-2 production, IL-2 mRNA from PHA plus PMA-stimulated cultures. We also found that H-7 inhibited the early-stage activation of PHA-stimulated cells. The presence of exogenous purified human IL-2 or rIL-4 partly reversed the immunosuppression caused by H-7. In contrast, HA1004 had no effect on cell proliferation, IL-2 production, or IL-2R expression. Our results demonstrate that PKC activation is one major pathway through which T-cells become activated.
 ...
PMID:Regulation of mitogen-stimulated human T-cell proliferation, interleukin-2 production, and interleukin-2 receptor expression by protein kinase C inhibitor, H-7. 238 93

We have studied the ability of human peripheral blood mononuclear cells (PBMC) to produce interferon-alpha (IFN-alpha) and IFN-gamma in the presence of pharmacologic agents known to influence calcium transport or calcium-dependent processes. We have found that the production of human (Hu) IFN-gamma is affected significantly by alterations in calcium flux; however, this influence is dependent upon the nature of the compound used to induce IFN. Inhibitors of protein kinase C decreased yields of IFN-gamma but inhibition of calmodulin did not. The presence of vitamin D3 reduced IFN-gamma titers when PHA and IL-2 were used to induce IFN, but not when ionomycin was used as the inducer. The production of IFN-gamma by PBMC was reduced by diminished concentrations in extracellular calcium but not extracellular magnesium. In contrast, neither the presence of any of the pharmacological agents tested above nor the reduction of the calcium concentration influenced the production of HuIFN-alpha by PBMC.
 ...
PMID:Calcium and the production of interferon by human peripheral blood mononuclear cells. 246 90

Among the cytokines tested here (IL-2, IL-3, IL-4, IL-5, IL-6, granulocyte colony stimulating factor (G-CSF), granulocyte/macrophage colony stimulating factor (GM-CSF), interferon-alpha (IFN-alpha), interferon-beta (IFN-beta) and interferon-gamma (IFN-gamma] only interleukin 1(IL-1) augmented HIV-long terminal repeat(LTR) directed chloramphenicol acetyl transferase(CAT) activity in protein kinase C(PKC)-independent manner. However, a stimulation by IL-1 was not as efficient as that due to tumor necrosis factor and the HIV production was not significant. IL-1 was not cytotoxic to MOLT-4/HIV cells.
 ...
PMID:Effect of interleukin-1 on the augmentation of human immunodeficiency virus gene expression. 248 Jul 82

We have studied whether the decreased lymphocyte proliferative responses of AIDS lymphocytes to stimulation by mitogens and antigens may be overcome when challenged with a combination of calcium ionophore A23187 and phorbol ester PMA. Comparison of the proliferative response of lymphocytes from nine patients with AIDS with the response of lymphocytes from nine control subjects showed that the response of AIDS lymphocytes was severely decreased when stimulated with PHA and no further response could be achieved by stimulation with A23187/PMA. On the other hand, no significant difference between the PHA-induced rise of cytoplasmic free calcium concentration ([Ca2+]1) in normal and AIDS lymphocytes was observed. The percentage of cells expressing IL-2 receptors (CD25) was also normal both after addition of PHA and after addition of A23187/PMA and the expression was normal on both CD4 and CD8 cells. The production of IL-2 in normal lymphocytes stimulated with A23187/PMA was 33 times higher than that after stimulation with PHA. In AIDS lymphocytes the production of IL-2 induced by all activators was severely decreased compared to control subjects, although the production of IL-2 after stimulation with A23187/PMA was higher than that in control lymphocytes after stimulation with PHA. The present study shows that a direct activation of protein kinase C combined with mobilization of cytoplasmic calcium does not overcome the lymphocyte proliferative deficiency of AIDS lymphocytes.
 ...
PMID:Stimulation of AIDS lymphocytes with calcium ionophore (A23187) and phorbol ester (PMA): studies of cytoplasmic free Ca, IL-2 receptor expression, IL-2 production, and proliferation. 249 38

The CD69 (Leu-23) activation Ag is a phosphorylated 28 to 32-kDa disulfide-linked homodimer that is rapidly induced after lymphocyte activation. CD69 is not present on the surface of peripheral blood resting T cells, but is constitutively expressed by CD3bright thymocytes. Activation of protein kinase C (PKC) by stimulation of the TCR/CD3 or by phorbol esters directly induces CD69 expression on T cells. In the attempt to elucidate the function of CD69 we investigated the ability of the CD69 glycoprotein to transmit an activation signal. Cross-linking of CD69 by mAb induced a prolonged elevation of intracellular [Ca2+], mostly due to an influx of extracellular Ca2+. This signal alone was unable to effectively activate PKC. When PKC was simultaneously activated by PMA, stimulation of CD69 induced IL-2 and IFN-gamma gene expression, enhancement of CD25 expression, and ultimately IL-2-dependent T cell proliferation. Both CD4+ and CD8+ peripheral T cells responded to CD69-mediated activation. Stimulation of CD69 induced proliferation of thymocytes as well as peripheral T cells, but both required independent PKC activation by PMA. Cyclosporin A, which does not prevent PKC-induced CD69 expression, completely suppressed CD69-induced IL-2 and IFN-gamma gene expression. Although the signal delivered by the CD69 initiates T cell proliferation, it is unable to trigger cytotoxicity programs in CD69+-activated T cells or T cell clones.
 ...
PMID:T cell activation via Leu-23 (CD69). 250 89

Previous data generated by ourselves and others questioned the role of degranulation as a mechanism to explain CTL-mediated cytotoxicity. In this report we examine this tissue in greater depth. CTL-mediated lysis was probed with three different inhibitors. 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene inhibits degranulation in a wide range of cell types, including CTL. EGTA, through chelation of Ca2+, also inhibits degranulation processes in CTL, and would inhibit other events or processes dependent on extracellular Ca2+. We also used prolonged exposure to PMA to exhaust PKC activity in CTL. Using these inhibitors, we have defined three pathways of lysis used by CTL. One pathway requires Ca2+, is PMA sensitive, but does not depend on degranulation. The second pathway is independent of Ca2+, is not PMA sensitive, and also does not depend on degranulation. All primary CTL and cloned CTL lyse most target cells via pathway I. However, when confronted with certain target cells (which we have referred to previously as Ca2+-independent target cells), pathway II is induced. When pathway II is induced, pathway I apparently shuts down. We show here that pathway II does not depend on protein synthesis, and that it also leads to DNA solubilization in target cells. A limited number of cloned CTL use pathways I and II as just described, but use in addition, and simultaneously, a third pathway that appears to involve degranulation. This pathway is seen irregularly in most CTL clones, and may be influenced by levels of IL-2 in the culture medium.
 ...
PMID:Evidence for multiple lytic pathways used by cytotoxic T lymphocytes. 250 76


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>