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)

The present work investigated the association between prostaglandin E2 (PGE2) from macrophages and its inhibition of murine lymphokine-activated killer (LAK) cell generation. The coculture of indomethacin with interleukin-2 (IL-2) augmented LAK cell activity in an indomethacin dose-response manner, and diminished PGE2 content in the corresponding culture supernatant in a reverse dose-response manner. The correlation between the increase in LAK cell activity and the decrease in PGE2 content was highly significant. Identical results were obtained with diclofenac. A profound inhibition of LAK cell activity by exogenous PGE2 in a dose-response manner was detected. Polyclonal anti-PGE2 antiserum augmented in a dose-dependent manner the LAK cell activity, by neutralizing PGE2 in the medium. A reduction of PGE2 content in the culture supernatant was also detected when the macrophage subpopulations were cultured and was indomethacin dose-dependent. In comparison with that of normal mouse splenocytes, the incubation of whole splenocytes of tumor-bearing mice, which contained a greater subpopulation of macrophages (24% vs. 12%), produced a greater PGE2 content and a correspondingly depressed LAK cell activity. Additionally, PGE2 reduced protein kinase C (PKC) activity along with LAK cell activity generated from macrophage-depleted T cells and natural-killer-like cells. These results overall indicate that PGE2 from macrophages in murine splenocyte cultures inhibits the LAK cell generation, and PKC may be involved in the inhibition mechanism.
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PMID:Prostaglandin E2 from macrophages of murine splenocyte cultures inhibits the generation of lymphokine-activated killer cell activity. 202 83

Macrophages cultured with IL-2 and IFN-gamma before exposure to microorganisms developed the ability to resist infection with the obligate intracellular parasite, Leishmania major. The induction of this macrophage effector response was maximal by 6 to 8 h after lymphokine addition, and was independent of lymphokine treatment sequence. Activation of macrophages for resistance to infection was the result of the direct action of IL-2 and IFN-gamma on macrophages: the effector reaction was demonstrated in both resident peritoneal macrophages depleted of T cells and bone marrow-derived cells, a homogeneous macrophage population. Radiolabeled murine rIFN-gamma, human rIL-2, and mAb to the IL-2R (7D4), each bound to murine bone marrow-derived macrophages in a specific and saturable manner, which suggested that unstimulated macrophages have receptors for both lymphokines. Treatment of macrophages with IFN-gamma increased the specific binding of IL-2; treatment of cells with IL-2, however, did not up-regulate the IFN-gamma-R. Addition of protein or RNA synthesis inhibitors (cycloheximide, emetine, actinomycin D) during exposure to rIL-2 and rIFN-gamma totally abrogated the ability of macrophages to express this effector reaction; inhibitors of protein kinase C, PG, or calcium redistribution had no effect. Soluble polyclonal anti-TNF-alpha antibodies in culture fluids after activation of macrophages with IL-2 and IFN-gamma totally abrogated the expression of resistance to infection. The T cell growth hormone IL-2 acts as cofactor with IFN-gamma for induction of a macrophage antimicrobial activity, and TNF-alpha may be the effector molecule for resistance to infection regulated by these two lymphokines.
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PMID:IL-2. A cofactor for induction of activated macrophage resistance to infection. 211 43

We have evaluated potential molecular mechanisms by which a group of synthetic lymphokine-like molecules, the 7,8-disubstituted guanine ribonucleosides, acts on second messenger pathways to augment the responses of murine B lymphocytes. Despite its extensive structural homology with GTP, 7-methyl-8-oxoguanosine (7-Me-8-oGuo), a prototypical disubstituted nucleoside, does not inhibit the binding of guanosine 5'-3-O-(thio)triphosphate either to purified G-proteins, or to G-proteins in situ in the plasma membrane. In contrast to anti-IgM antibodies, 7-Me-8-oGuo fails to induce elevation of intracellular free calcium in B lymphocytes. It does not elicit enhanced production of inositol phosphates in either unfractionated or large, cycling B cells (the cells on which it acts preferentially). It is unable to modify the cellular distribution or activity of protein kinase C, whereas phorbol 12-myristate 13-acetate, anti-IgD antibodies, and lipopolysaccharide do activate protein kinase C. Inhibitors of protein kinase C activity diminish stimulation of mRNA transcription by anti-IgD antibodies and lipopolysaccharide but not by 7-Me-8-oGuo. These data demonstrate that 7-Me-8-oGuo either uses a pathway distinct from that mediated by G-proteins, intracellular free calcium, inositol phosphates, and protein kinase C, or else bypasses the early events of this pathway, activating the cell at a point beyond their involvement. In either event, these nucleosides represent the only class of activator to date that is capable of driving B cell proliferation and differentiation without involvement of protein kinase C.
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PMID:Activity of an intracellular lymphocyte stimulator is independent of G-protein interactions, [Ca2+]i elevation, phosphoinositide hydrolysis, and protein kinase C translocation. 216 55

Interleukin 3 (IL-3) is required for the survival and proliferation of mouse bone marrow derived mast cells (BMMC). Although interleukin 4 (IL-4) has no direct effect on growth activity, it synergizes with IL-3 in promoting the growth of these cells. The intracellular mechanism by which these ligand-receptor interactions promote mast cell growth are not well documented in the literature. Here we present evidence that both IL-3 and IL-4 have been found to activate protein kinase C (PKC) and phosphatidylinositol turnover in BMMC, in a similar time- and dose-dependent manner, indicating that activation of PKC is not sufficient to induce proliferation in these cells. In this work we addressed the question as to whether the activation of PKC is necessary for mast cell proliferation. Activation of PKC by phorbol myristate acetate causes inhibition of IL-3-mediated growth for the first 72 h of incubation. The inhibition in IL-3-mediated proliferation gradually lessens with the stages of PKC depletion, which is complete after 72 h. The enhancement in phorbol myristate acetate-treated cells grows as PKC is depleted. The inactive phorbol ester, 4-alpha-phorbol, had no effect on proliferation of BMMC. Cells, PKC-depleted by chronical phorbol ester treatment, responded to IL-3 or IL-4 with a significant increase in [3H] thymidine uptake over PKC containing cells stimulated with the same lymphokine. Use of antibodies to these lymphokines showed that the enhanced response of the PKC-depleted BMMC was not due to the additional autocrine production of IL-3 or IL-4 by these cells. The PKC-depleted cells retain the capacity to return to almost normal levels of PKC activity and sensitivity to IL-3 and IL-4, after 72 and 120 h, respectively. These results indicate that PKC plays an important inhibitory role in IL-3- and IL-4-mediated proliferation of BMMC.
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PMID:Protein kinase C plays an inhibitory role in interleukin 3- and interleukin 4-mediated mast cell proliferation. 226 15

The ability of tumor necrosis factor (TNF)-alpha to activate T lymphocytes in combination with other stimuli has been studied. TNF was strongly co-mitogenic with low doses of anti-CD3 antibodies or phorbol esters (those which are strong activators of protein kinase C, PKC) but poorly with phytohemagglutinin or concanavalin A. No synergism was seen with the calcium ionophore A23187. TNF was co-mitogenic with several phorbol esters known to activate PKC but was uneffective with inactive phorbol esters such as methyl-phorbol 12-myristate 13-acetate. Furthermore, H-7 a known inhibitor of PKC, inhibited the proliferative response of T cells induced by esters plus TNF. This effect took place at low doses of TNF and was also observed with purified T lymphocytes indicating that the effect of TNF was not dependent on accessory cells. This proliferative effect of TNF was inhibited by an anti-interleukin 2 receptor (IL2R) antibody, MAR 108, which blocks IL2 binding to its receptor. Although PKC activation induced CD25 (IL2R) expression but very little IL2 synthesis, TNF did not synergize by augmenting the synthesis of this lymphokine in peripheral blood lymphocytes stimulated with phorbol esters. By contrast, TNF strongly increased the membrane level of CD25 and to a lesser extent that of the activation antigen, 4F2, over the levels already induced by phorbol esters on T cells. More interestingly, TNF significantly increased the number of high-affinity IL2R on purified T cells in the presence of phorbol 12,13-dibutyrate. Our results indicate that TNF is co-mitogenic with those stimuli which strongly activate PKC and suggest that TNF may play a role on T cell activation increasing the number of effective IL2/IL2R interactions when these are limiting.
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PMID:Synergy of tumor necrosis factor with protein kinase C activators on T cell activation. 231 52

As illustrated in Fig. 3, our understanding of lymphokine production is incomplete. Nuclear effects of PKC are probably mediated by phosphorylated substrates. Some of the substrates are themselves being identified as kinases and phosphatases, adding more complexity to the pathway. Use of resistant cell lines is one of the approaches that may help link early phosphorylation events with later transcriptional responses.
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PMID:Control of lymphokine production by protein kinase C. 240 15

The thymic leukemia cell line EL4 has been shown to produce the lymphokine Interleukin-2 (IL-2) following stimulation with phorbol ester (PMA). We investigated intracellular enzyme pathways triggered by phorbol stimulation using an EL4 cell line which responds to PMA with IL-2 synthesis (EL4r) and one which does not produce IL-2 following stimulation (EL4nr). By comparing these two cell lines we hoped to establish which enzyme activities were associated with IL-2 synthesis. The enzyme pathways studied included calcium/phospholipid dependent protein kinase (C-kinase) activity, the induction of polyamine synthesis, RNA, DNA and protein synthesis and finally IL-2 production. Our results indicate that both EL4 cell lines have a receptor for PMA, which can activate the C-kinase enzyme. Further, in both cell lines PMA activates the nuclear synthesis of polyamines as demonstrated by ornithine decarboxylase induction. Both RNA and protein synthesis measured by 3H-uridine and 3H-leucine uptake respectively appear comparable between EL4r and EL4nr. The only difference in cellular responsiveness between EL4r and EL4nr was in the 3H-thymidine uptake, and IL-2 production. IL-2 production or lack of production was established by 3H-uridine and 3H-thymidine incorporation as well as viable cell count using the IL-2 dependent cell line CTLL-2. We, therefore, conclude that EL4r and EL4nr cells show similar intracellular responses to phorbol ester except for 3H-thymidine uptake and detectable IL-2 production. Our results suggest that failure of PMA-stimulated EL4nr cells to produce IL-2 is either due to inability of this cell line to synthesize IL-2 or the production of defective IL-2. It is not due to failure of PMA to activate C-kinase or the subsequent nuclear events.
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PMID:The activation of calcium/phospholipid dependent protein kinase and the association with interleukin-2 production. 242 45

Interleukin 2 (IL-2) stimulated the differentiation of human peripheral blood leukocytes into lymphokine-activated killer cells, as well as DNA synthesis of human T lymphocytes. Both effects of IL-2 could be inhibited by prostaglandin E2, a potent stimulator of adenylate cyclase; however, the inhibitory effect of prostaglandin E2 could be overcome by increased concentrations of IL-2. The opposite effects of IL-2 and prostaglandin E2 were paralleled by their respective abilities to inhibit and stimulate cAMP production in intact cells. Other agents, which inhibit adenylate cyclase directly (somatostatin, beta-endorphin, UK 14.3041) or indirectly by activation of protein kinase C (phenylephrine), could stimulate both differentiation and proliferation. None of these agents alone or in combination were as effective as maximal concentrations of IL-2. However, all agents potentiated differentiation and proliferation induced by submaximal and maximal concentrations of IL-2. Additionally, combinations of agents which stimulated protein kinase C with those that inhibited adenylate cyclase were additive in the potentiation of IL-2-induced differentiation. Neither inhibition nor potentiation of IL-2-induced lymphokine-activated killer cell differentiation was accompanied by changes in Tac expression or gamma-interferon production. The data indicate that the stimulation of lymphokine-activated killer cell differentiation and lymphocyte proliferation in human cells share a common initial biochemical signal. Although the inhibition of adenylate cyclase is not sufficient to maximally stimulate either process and cannot bypass the requirement for IL-2, modulation of this enzyme complex, positively or negatively, can regulate the ultimate physiologic response to IL-2.
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PMID:Potentiation of lymphokine-activated killer cell differentiation and lymphocyte proliferation by stimulation of protein kinase C or inhibition of adenylate cyclase. 244 68

Sn-1,2-diacylglycerols (DAG) and ionized-free calcium can act as intracellular second messengers for cell activation. Traditionally, T-lymphocyte activation is assessed by measurements of DNA synthesis or lymphokine production, but these responses require several days to occur and involve multiple intermediary regulatory steps. In contrast, we have found that T-lymphocytes demonstrate rapid enhancement of A-(alanine-favoring) system amino acid uptake when treated with DAG or ionomycin. A 30-40% increase in the initial velocity of uptake (vi) of the synthetic A-system specific amino acid, methylamino-isobutyric acid (MeAIB), was measured following 5 min of exposure to DAG or ionomycin. The vi was enhanced 60% from 12 to 19 mumol/liter cell water per min after 30 min exposure of T-cells to optimal concentrations of dioctanoylglycerol (30 microM), oleoylacetylglycerol (30 microM), or ionomycin (5 microM) (P less than .01 for each agent). A 50-fold excess of non-radioactive MeAIB inhibited 80% of [14C]MeAIB uptake in both unstimulated and stimulated cells, indicating that uptake remained largely carrier-mediated on treatment with these agents. Cycloheximide, 100 micrograms/ml, inhibited protein synthesis but did not block the A-system amino acid transport enhancement induced by DAG or ionomycin. The DAG-induced increase in the vi was blocked 40% with 100 microM H-7, an inhibitor of protein kinase C. H-7 treatment did not inhibit the ionomycin-induced A-system enhancement. A marked increase in cytoplasmic free calcium was measured when T-lymphocytes were exposed to ionomycin but not on DAG exposure, and the A-system effect of ionomycin but not DAG was blocked by extracellular EGTA. These data are compatible with two pathways for rapid enhancement of A-system amino acid uptake in T-lymphocytes. DAG stimulation is mediated via protein kinase C whereas ionomycin produces an A-system effect of similar magnitude independent of protein kinase C by an increase in cytoplasmic calcium.
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PMID:Diacylglycerol and calcium induce rapid enhancement of A-system amino acid transport by independent mechanisms in human T-lymphocytes. 250 95

PMA can induce the proliferation of several CTL clones but not of several Th clones derived and tested in our laboratory. The PMA-stimulated proliferation of our CTL clones (which do not make IL-2 mRNA or protein) occurs independently of IL-2 and is not accompanied by lymphokine release. We now report, however, that protein kinase C (PKC) translocation is induced by PMA in CTL clones as well as in Th clones, which lack a proliferative response to PMA. These results suggest that PKC translocation itself is not a sufficient regulatory mechanism to account for cloned T cell proliferation. Moreover, IL-2 did not induce PKC translocation in a CTL clone, which proliferates when stimulated with IL-2. Thus, PKC translocation may not be necessary for activation of CTL proliferation. Nonetheless, cellular PKC activity appears to be required for the proliferative response of T cell clones after stimulation by PMA/PMA + calcium ionophore (A23187) or by triggering through the TCR: chronic PMA treatment, which depletes intracellular PKC activity, abrogates the proliferative response of T cell clones stimulated by PMA/PMA + A23187 or triggered through the TCR. T cell clones depleted of PKC activity, however, retain the ability to proliferate when challenged with IL-2. Murine T cell clones, therefore, possess PKC-dependent and PKC-independent pathways of proliferation that are not regulated by PKC translocation alone.
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PMID:Protein kinase C-dependent and -independent mechanisms of cloned murine T cell proliferation. The role of protein kinase C translocation and protein kinase C activity. 252 51


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