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 suppressive effect of the glucocorticoid dexamethasone (DEX) on purified CD4+ T cells was found to depend on the activation pathway. In contrast to anti-CD3- or PHA-induced T cell proliferation, the alternative pathway of T cell activation, i.e., through anti-CD2 and anti-CD28, appeared largely resistant to DEX. By titrating anti-CD28 or the protein kinase C (PKC) activator PMA in the DEX-sensitive systems, it was demonstrated that inhibition by DEX could be abrogated by enhancing the CD28 signal or by stimulation of the PKC-dependent pathway. Supraoptimal concentrations of PMA were inhibitory for proliferation and this effect was partly prevented by DEX. These data suggest that the outcome of the effect of DEX on CD4+ T cells is dependent on the activation pathway, in particular the role and composition of the transcription factor AP-1.
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PMID:Abrogation of the suppressive effects of dexamethasone by PKC activation or CD28 triggering. 791 97

TCR (beta-chain) transgenic mice were tolerized with the superantigen staphylococcal enterotoxin B (SEB). Three to 28 days after tolerization with SEB, flow cytometry of peripheral T cells showed the persistence of SEB-unresponsive T cells that did not express reduced levels of the TCR (beta-chain) transgene. Stimulation of the tolerized T cells with a panel of superantigens (SEC1), mitogens (Con A, PHA, and pertussis toxin) and mAb (anti-CD3 epsilon) did not induce T cell proliferation. In contrast to other models, exogenous rIL-2 did not reverse unresponsiveness and induce proliferation. In addition, lymphokines rIL-4 and rIL-6 also did not induce proliferation. However, the unresponsive T cells did respond to the combination of PMA plus ionomycin, but not to PMA or ionomycin alone. Thus, the block in signal transduction in the anergic state occurs between the stimulation of cell surface receptors and the activation of protein kinase C and the increase in intracellular calcium. In addition, these results show that mature T cells tolerized with the superantigen SEB are unresponsive to a wide array of T cell stimuli, indicating a block in a common signal transduction pathway.
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PMID:Superantigen-induced peripheral tolerance inhibits T cell responses to immunogenic peptides in TCR (beta-chain) transgenic mice. 809 52

In Jurkat cells, the three Ca(2+)-ATPase blockers, thapsigargin, cyclopiazonic acid, and di-tert-butylhydroquinone (DtBuHQ) induced both a release of Ca2+ from intracellular stores and a Ca2+ influx. In contrast to CD3 mAb, the Ca(2+)-ATPase inhibitors did not induce the formation of inositol trisphosphate from the hydrolysis of phosphatidylinositides. Emptying intracellular Ca2+ stores was accompanied by a decrease of phosphatidylserine (PtdSer) synthesis as previously observed in PHA- or CD3 mAb-treated Jurkat cells. In the presence of a phorbol ester able to activate protein kinase C, TPA, the three Ca(2+)-ATPase inhibitors induced Jurkat cells to synthesize large amounts of interleukin-2 demonstrating that early signal transduction mechanisms can be bypassed by Ca(2+)-ATPase inhibitors. In purified human peripheral blood T lymphocytes, the same inhibitors induced moderate if any cytosolic Ca2+ rise, in the absence of external calcium. Nevertheless analysis of PtdSer synthesis suggested that intracellular stores were efficiently depleted by DtBuHQ and cyclopiazonic acid but not by thapsigargin. In contrast, the three compounds induced similar Ca2+ influx. However, in the presence of TPA, cyclopiazonic acid and DtBuHQ induce highly purified T cells to proliferate while thapsigargin did not, suggesting that the status of internal Ca2+ store may have a decisive role in T cell activation.
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PMID:Ca(2+)-ATPase inhibitors induce interleukin-2 synthesis and T cell proliferation. 833 Mar 10

Cyclosporine A (CsA) and its major metabolites: M1, M17 and M21 and two analogues: cyclosporines C (CsC) and D (CsD), were studied for their capacity to interfere with different in vitro activation pathways. Their inhibition potentials against the reaction of Graft-versus-Host (GvH) were also studied. The results showed: CsA, CsC and metabolite M17 were the most active compounds upon the inhibition of lymphocyte proliferation induced by different mitogens (ConA, PHA, PWM) and also on the proliferation of mixed lymphocyte cultures (MLC). The same results were observed concerning the direct activation by protein kinase C using a combined action of phorbol ester + calcium ionophore. In vivo using local GvH reaction, CsA and CsC proved more active than M17 in the two different combinations: H-2d --> (H-2b x H-2d)F1 and H-2k --> (H-2b x H-2k)F1 CsD and two metabolites M1 and M21 showed no or weak immunosuppressive effects. Overall, the immunosuppressive potency of six compounds could be schematized as: CsA > or = CsC > M17 > M1 > or = CsD > M21.
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PMID:In vitro and in vivo comparative studies on immunosuppressive properties of cyclosporines A, C, D and metabolites M1, M17 and M21. 834 48

A peptide inhibiting either corpuscolate or purified PKC has been identified from microsomes of PHA-activated human PBMC but it is not detectable in microsomes of resting PBMC. The peptide was obtained from a microsomal preparation in an oligomeric form that could be transformed into a monomeric form by beta-MSH. The active peptide (IN) was retained on a PC-11 chromatographic column and could be eluted with NaCl. IN is ineffective on PKC-dependent protamine phosphorylation of protamine and on Ca2+ and phospholipid-independent activity generated by mild hydrolysis with trypsin of PKC. Ca2+ binding is permissive for IN activity. IN inhibits particulate PKC in PHA-activated PBMC, but is ineffective after TPA activation. All these data indicate that IN acts at the regulatory domain of PKC.
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PMID:Identification of a novel protein kinase C inhibitor in microsomes from phytohaemagglutinin activated human peripheral blood mononuclear cells. 836 75

T lymphocyte activation and proliferation are complex cellular processes involving membrane and cytoplasmatic molecules as well as the secretion and response to cytokines, mainly interleukin 2. There is increasing evidence that autoimmune thrombocytopenic purpura (ATP) is associated with an alteration of the regulation of the immune system. The blastogenic response of purified T lymphocytes to mitogens that interact with membrane molecules (phytohemaglutinin, anti-CD3 monoclonal antibody) and with intracytoplasmic protein kinase C (phorbol myristate acetate) has been investigated in 22 ATP patients and 18 healthy controls. After the signal given by the three different mitogens [3H]-thymidine uptake in T lymphocytes from ATP patients was found to be significantly decreased with respect to that found in healthy controls under similar experimental conditions (P < 0.05). Analysis of the cell cycle progression in these T lymphocytes from ATP patients, showed a significantly diminished percentage of cells in S-phase after PHA stimulation (P < 0.05). The percentage of CD3+ cells in the CD2+ lymphocyte preparations was significantly decreased in ATP patients relative to healthy controls (P < 0.05). But there was no significant correlation between this percentage and the blastogenic response to PHA in the CD2+ cellular preparations from both groups of subjects. No significant differences were found in the percentages of CD4+ and CD8+ cells. These data indicate that the impaired blastogenic response of T lymphocytes from ATP patients may be ascribed to an intrinsic defect in these T cells. This defective proliferative response of T lymphocytes from ATP patients cannot be ascribed to either defective interleukin 2 production or receptor expression which were both similar to those of healthy controls (P > 0.05). And, the presence of saturating amounts of exogenous interleukin 2 did not normalize the defective proliferative response the mitogenic signals on the part of T lymphocytes from ATP patients. We conclude that T lymphocytes from ATP patients have a defective proliferative response to membrane and intracytoplasmatic mitogenic signals.
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PMID:T lymphocytes from autoimmune thrombocytopenic purpura show a defective activation and proliferation after cytoplasmic membrane and intracytoplasmic mitogenic signals. 819 58

T lymphocytes from patients with B cell chronic lymphocytic leukemia (B-CLL) exhibit defective proliferative response to plant lectins. The blastogenic response of purified T lymphocytes to signals that interact with membrane molecules (phytohemagglutinin [PHA], anti-CD3 monoclonal antibody [MAB]) and with the intracytoplasmic protein kinase C (PKC) was investigated in 22 B-CLL patients and 18 healthy controls. 3H-thymidine uptake in T lymphocytes from 14 of 22 B-CLL patients after PHA, anti-CD3, and phorbol myristate acetate (PMA) was found to be lower than in the healthy controls. This defective proliferative response was not corrected by the exogenous addition of interleukin-2 (IL-2) to the culture medium. In analyzing the cell cycle progression of these T lymphocytes from B-CLL patients, we found that the percentage of cells in S phase at 2 days of PHA stimulation was significantly decreased and that it was normalized after 5 days of culture. Defective response of T lymphocytes from B-CLL patients to polyclonal mitogens was observed in those patients with advanced disease (stages A, B, and C). However, this T cell proliferative response was normal in patients with "smoldering B-CLL." We conclude that the defective proliferative response to membrane and intracytoplasmatic mitogenic signals on T lymphocytes from a part of B-CLL patients can be ascribed to delayed activation and cell-cycle progression, and an association between the alterations in the T cell compartment of B-CLL patients and the progression of the disease may be suggested.
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PMID:Diminished DNA synthesis in T cells from B chronic lymphocytic leukemia after phytohemagglutinin, anti-CD3, and phorbol myristate acetate mitogenic signals. 840 37

Immunosuppressive agents may initiate their pharmacologic action by disrupting phosphorylation cascades critical to T lymphocyte intracellular signaling after alloantigen recognition. Activator of DNA Replication (ADR), a transduction signal sensitive to CsA as well as rapamycin (RAPA) immunosuppression, seemed a likely candidate for phosphoregulation. This communication reports the development of a cell-free assay wherein CsA and RAPA inhibit ADR induction by protein kinase C (PKC). ADR and PKC are inactive in the cytosol of resting cells. Endogenous PKC activity in quiescent lymphocytes was triggered with the tumor promoter PMA, leading to the appearance of ADR, an event subsequently quantitated by the ability of ADR to trigger [3H]thymidine triphosphate incorporation into isolated nuclei. After PKC induction, ADR activity is increased (890 +/- 120 vs. 3910 +/- 345 cpm, P < 0.001). In the presence of the PKC inhibitor H7, ADR activity fails to increase (100 +/- 50 vs. 3910 +/- 345 cpm, P < 0.001). The high levels of ADR found in PHA-stimulated cells is marginally affected by in situ PKC induction, although the sustained impact of H7 throughout the cell cycle suggests that ADR is constantly being phosphorylated. Titration of CsA or RAPA into the cell-free system inhibited ADR induction in a dose-dependent fashion. The utility of ADR induction as a marker for immunosuppression was investigated by comparing ADR inducibility in resting cells that had been preloaded with CsA or RAPA with the proliferative index of cells cultivated with CsA or RAPA. ADR induction directly correlated with CsA or RAPA proliferative inhibition. The results suggested that ADR is a constituent of the PKC phosphoregulatory cascade essential for cell cycle progression. The correlation between cell-free ADR inducibility and proliferative inhibition by CsA or RAPA suggest that this procedure may be useful for in vitro prediction of allografted patient immunologic response.
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PMID:Cyclosporine and rapamycin affect protein kinase C induction of the intracellular activation signal, activator of DNA replication. 849 93

T2, an extract of Tripterygium wilfordii Hook F, has been reported to be effective in the treatment of a variety of autoimmune diseases, including rheumatoid arthritis. Previous studies have shown that T2 inhibited mitogen- or antigen-induced proliferation of human peripheral blood T cells and B cells, IL-2 production by T cells and Ig production by B cells. In contrast, T2 did not affect monocyte functions, such as IL-1 production and antigen presentation. The current studies sought to localize the immunosuppressive action of T2 more precisely. Results show that T2 prevented [3H]-uridine uptake by mitogen-stimulated T cells and arrested them in the early GI phase of the cell cycle. The inhibitory effects of T2 could be partially overcome by costimulating PHA activated T cells with PMA and completely nullified by costimulation with PMA plus a monoclonal antibody to CD28. Moreover, T2 had no effect on expression of IL-2R or the transferrin receptor (CD71), but inhibited production of a number of cytokines, including IL-2 and IFN-gamma by activated T cells. T2 suppressed IL-2 mRNA levels, but not IL-2R mRNA levels, in activated T cells. T2-mediated inhibition reflected suppression of IL-2 gene transcription as indicated by suppression of the expression of a reporter gene driven by the IL-2 promoter. T2 had little inhibitory effect on either IL-2 gene expression or cell cycle progression when added after initial mitogenic stimulation, indicating that an early step in the cascade of activation events was inhibited. However, initial activation events including protein tyrosine phosphorylation, the generation of diacylglycerol, IP3, and the translocation of protein kinase C were not inhibited by T2. Moreover, T2 did not inhibit the phosphatase activity of calcineurin. These results have localized the effect of T2 to a step in the T cell activation cascade after initial second messenger generation, tyrosine phosphorylation and protein kinase activation, but before IL-2 gene transcription.
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PMID:The Chinese herbal remedy, T2, inhibits mitogen-induced cytokine gene transcription by T cells, but not initial signal transduction. 855 49

In the present study we compared the effect of rapamycin to that of CsA on the in vitro responses of lectin (PHA), phorbol-ester (PMA) and CA2+ ionophore (ionomycin)-activated peripheral blood mononuclear cells by measuring the release of soluble IL-2R (sIL-2R), high levels of which have been detected in clinical syndromes characterized by an ongoing immune activation. PHA was the stimulant associated with high sIL-2R release, whereas ionomycin-induced sIL-2R release only exceeded the background response and the sensitivity of the ELISA kit. The highest sIL-2R release, however, was obtained when PMA was used in combination with either PHA or ionomycin. Rapamycin inhibited the release of sIL-2R in response to all activators, whereas CsA only abolished the ionomycin-induced sIL-2R release. In parallel experiments rapamycin inhibited cell proliferation in response to all stimulants with the exception of PMA/ionomycin, whereas CsA inhibited all proliferation. Our study clearly shows that for optimal sIL-2R release both Ca+ and protein kinase C-triggered signals are required and that rapamycin has a distinct advantage over CsA in inhibiting the release of sIL-2R, which has been shown to be a reliable marker of lymphocyte activation either in vivo or in vitro.
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PMID:Rapamycin inhibits the in vitro release of soluble interleukin-2 receptor by activated peripheral blood mononuclear cells (PBMC) independently of the mode of activation. 858 87


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