Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.1 (protein kinase)
 81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

cAMP is an intracellular second messenger that conveys inhibitory signals for T cell activation and clonal proliferation. cAMP also inhibits the production of IL-2 and IL-2R alpha-chain expression. To determine the mechanisms of this inhibition, human peripheral blood T lymphocytes were stimulated with anti-CD3 mAb, PHA, PMA, or ionomycin, alone or in combination. cAMP elevation by PGE2, cholera toxin, or the cell-permeable analogue 8-bromo-cAMP inhibited the tyrosine phosphorylation of a protein of 100 kDa. This inhibition was associated with decreased IL-2 production and IL-2R alpha expression at both the protein product and the mRNA levels. Nuclear run-off assays showed that the inhibitory effect of cAMP on IL-2 and IL-2R alpha gene expression is mediated at the transcriptional level. H-8, an inhibitor of protein kinase A, reversed the inhibitory effect of cAMP on nuclear transcription of the IL-2 gene, suggesting that this is mediated through activation of protein kinase A. Post-transcriptionally, cAMP elevation decreased the t1/2 of IL-2 mRNA by more than 50%. These data indicate that cAMP inhibits cell membrane, cytoplasmic, and nuclear events associated with T cell activation and highlight the complexities of its action of lymphocyte function.
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PMID:Prostaglandin E2 and other cyclic AMP-elevating agents modulate IL-2 and IL-2R alpha gene expression at multiple levels. 137 2

Prosolin is a major cytosolic phosphoprotein expressed prominently in rapidly proliferating human peripheral lymphocytes but produced at very low levels in resting (G0) PBL. It undergoes rapid phosphorylation upon treatment of growing cells with tumor-producing phorbol esters (TPA) and this phosphorylation event is correlated with a rapid down-regulation of DNA synthesis. In the present report we have studied various agents that, like TPA, act as partial or complete mitogens for G0 PBL and have determined their effect on phosphorylation of prosolin and on DNA synthesis in rapidly proliferating (IL-2-dependent) human PBL. Agents that activate the TCR (OKT3 and PHA), as well as agents that by-pass the receptor but activate biochemical pathways associated with TCR activation (TPA and Ca2(+)-ionophore), all produced rapid phosphorylation of prosolin and prompt down-regulation of DNA synthesis. Four phosphorylated forms of prosolin were produced, indicating activation of a complex phosphorylation pathway. Down-regulation of DNA synthesis did not lead to cell death or to permanent arrest, but was reversed after 24 to 48 h, and was not associated with any reduction in overall protein synthesis. Agents that bind to determinants closely connected to the TCR but without activating it (OKT4 and OKT8) had no effect on either prosolin phosphorylation or DNA synthesis. The results indicate that prosolin is an early target of the protein kinase activities induced by activation of the TCR in proliferating PBL, and suggest that its phosphorylation mediates the TCR signal, transmitting it into a biochemical pathway leading specifically to down-regulation of DNA synthesis. In G0 PBL, in which the negligible expression of prosolin precludes significant production of phosphorylated species, this inhibitory pathway is effectively blocked.
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PMID:T cell receptor activation induces rapid phosphorylation of prosolin, which mediates down-regulation of DNA synthesis in proliferating peripheral lymphocytes. 190 11

In this study we examined by Northern blot analysis the expression of Raf-1 protooncogene in normal human peripheral blood leukocytes. Unlike thymocytes, circulating lymphocytes did not express appreciable levels of Raf-1 mRNA. In contrast, polymorphonuclear cells (PMN) had high levels of Raf-1 transcripts. Also density gradient separated monocytes showed Raf-1 mRNA but at lower levels compared to PMN. Expression of Raf-1 was constitutive inasmuch as it was not induced by the purification procedure. The half-life of Raf-1 mRNA in PMN was greater than 4 h. Functional activation of PMN and monocytes with various stimuli (phorbol esters, tumor necrosis factor, colony stimulating factors, LPS) did not affect Raf-1 expression. By contrast, density gradient purified monocytes allowed to adhere to plastic for 1 h expressed augmented levels of Raf-1. Monocytes cultivated in suspension or allowed to adhere to plastic showed an half-life of Raf-1 transcripts of, respectively, more than 4 h and less than 30 min. Circulating lymphocytes stimulated with mitogens (PHA, conA, anti-CD3 antibodies, and Staphylococcus aureus) also expressed high levels of transcripts of this protooncogene. PHA-induced transcripts in lymphocytes had an half-life greater than 4 h. The pattern of expression of Raf-1 in resting and activated leukocytes suggests that this protooncogene may play a role in expression of differentiated functions and activation of these cells.
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PMID:Differential expression of Raf-1 protooncogene in resting and activated human leukocyte populations. 202 80

The involvement of cyclic nucleotides in the regulation of cell growth is well established as are the findings that sustained high levels of intracellular cyclic adenosine monophosphate (cAMP) inhibit ligand-induced lymphocyte proliferation. However, there is considerable controversy concerning the precise role of cAMP in this regard or the target of its action. A number of studies with cAMP analogs or forskolin have implicated the early events after ligand binding as being particularly susceptible whereas others have failed to do so or offered alternate targets. We have examined the effects of cell permeant analogs of cAMP and forskolin on human T cell proliferation. After brief exposure to submitogenic concentrations of PHA or phorbol ester plus ionomycin, we have examined the effects of increased cAMP levels during initial activation (or induction of competence) and progression to DNA synthesis. We find that these drugs that inhibit T cell proliferation have little effect on induction of competence or early activation events including transmembrane Ca2+ uptake, release of Ca2+ from internal stores or induction of the genes encoding c-fos or early growth response gene. In contrast, it is the progression phase of the proliferative response which appears to be the major target for cAMP-protein kinase A-mediated inhibition of human T cell proliferation.
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PMID:Increased cyclic adenosine monophosphate levels block progression but not initiation of human T cell proliferation. 216 63

This study examined the phosphorylation of cytoplasmic and nuclear proteins in peripheral blood mononuclear cells (PBMC) of systemic lupus erythematosus (SLE) patients. The cytoplasmic and nuclear protein kinase activity in PBMC from SLE patients was at least five-fold higher than that of normal healthy subjects. PBMC of SLE patients produced different nuclear endogenous substrates on phosphorylation and also displayed distinct protein kinase activity. Nuclear phosphoproteins, with human PBMC DNA-binding ability, of 38 kD and 70 kD were detected from both SLE patients and normal healthy subjects, while the 40 kD phosphoprotein, with tyrosine as the main phosphorylation residue, was found only in SLE patients. Other nuclear phosphoproteins, and most of the detected cytoplasmic phosphoproteins, were present in higher levels in both normal PBMC with mitogen stimulation, such as PHA, and SLE PBMC. The expression level of the 40 kD nuclear phosphotyrosyl-protein showed a positive correlation with the clinical disease activity of SLE. These results suggest that PBMC from SLE patients had distinct tyrosine protein kinase (TPK) activity and/or a different endogenous substrate of nuclear DNA-binding proteins in tyrosine phosphorylation. The possible significance of tyrosine phosphorylation in PBMC of SLE patients in the pathogenesis, and its clinical meaning, are discussed.
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PMID:Nuclear phosphotyrosyl-protein with DNA-binding ability in peripheral blood mononuclear cells from systemic lupus erythematosus patients. 270 78

The addition of IL 2 to Con A-activated splenic T cells induced the rapid and time-dependent phosphorylation of membrane proteins with m.w. of 115,000 to 105,000, 90,000, and 66,000, and to a lesser extent 55,000 to 58,000, 40,000, and 34,000. Immunoprecipitations conducted with an anti-IL 2 receptor antibody indicated that the murine IL 2 receptor (55,000 to 58,000) was included in the set of IL 2-dependent phosphoproteins. Phosphorylation of these same proteins was also seen after IL 2 treatment of PHA-activated T cells and of the IL 2-dependent line CTLL-2. Membrane phosphorylation was dependent on physiologically relevant IL 2 concentrations (0.2 to 1 ng/ml), and was detected as early as 1 min after IL 2 addition, with maximal levels of phosphorylation achieved by 15 min. In contrast to these observations, the pattern of cytoplasmic protein phosphorylation remained unchanged after IL 2 addition, although IL 2 did augment the level of preexisting cytoplasmic phosphorylation induced by lectin. The pattern of membrane protein phosphorylation induced by IL 2 also overlapped in part with that induced after stimulation of Con A-activated T cells with the phorbol ester PMA. IL 2-stimulated phosphorylation was inhibited by the addition of agents that both stimulate cyclic AMP-dependent protein kinases and block lymphocyte mitogenesis. No effect was seen upon addition of agents that enhance cyclic GMP-dependent protein kinases. These observations support a role for specific membrane as opposed to cytoplasmic protein phosphorylation in the regulation of lymphocyte growth by IL 2, and also suggest that protein kinase A, and perhaps protein kinase C, participate as regulators of the IL 2 signaling mechanism.
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PMID:Interleukin 2-dependent phosphorylation of interleukin 2 receptors and other T cell membrane proteins. 300 13

The role of protein kinase-C (PK-C) protein phosphorylation on the mitogen triggered responses of T-lymphocytes was examined by observing the effect of polymyxin-B (an inhibitor of PK-C) on mitogen induced protein and DNA synthesis. Polymyxin-B inhibited 3H-thymidine incorporation by PHA activated T-lymphocytes over a range of PHA concentrations. 3H-leucine incorporation by PHA activated T-lymphocytes was inhibited by polymyxin-B in a dose dependent manner. A partially purified PK-C fraction from polymyxin-B treated PHA activated T-lymphocytes demonstrated less than 25% of the phosphorylating activity of untreated lymphocytes. These results suggest that protein synthesis during the T-lymphocyte activation process is dependent on PK-C activity.
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PMID:Effect of polymyxin-B on T-lymphocyte protein synthesis. 300 31

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

We studied the effects of beta 2-adrenoceptor agonist on IgE production in vitro in human and in vitro and in vivo in mouse. We observed that salbutamol and fenoterol potentiate the IL-4-induced IgE production from peripheral blood mononuclear cells. This effect is associated by an enhanced mRN expression for IgE. Fenoterol also potentiated, but in a lesser extent, the IgE production from purified B lymphocytes stimulated by both IL-4 and CD40, suggesting that the activity of beta 2-adrenoceptor agonist is mediated through T lymphocyte or monocyte modulation. Fenoterol also inhibited the PHA-induced IFN-gamma production by T lymphocytes. Analogues of cAMP or activator of PKA also elicited an increase in IgE production. Moreover, the effect of fenoterol on IgE production was suppressed in the presence of PKA inhibitor. Salbutamol also potentiated the IL-4-induced IgE production from murine splenocytes activated by LPS. Furthermore, mice sensitized to ovalbumin elicited increased IgE responses after daily injection of salbutamol. This was accompanied by an increased in cytokines of Th2 subtypes. Our results showed that beta 2-adrenoceptor agonist, which are currently used in the treatment of asthma, potentiate the IgE production in vitro and in vivo.
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PMID:[Effects of beta-adrenergic compounds on IgE production]. 858 26

Age-related changes in the functional properties of human T cells are well described, but less is known about possible changes in T cell signaling pathways. The signaling pathways mediated by mitogen-activated protein kinases (MAPK) are considered essential for normal cellular growth and function. Several stimuli trigger MAPK activation in human T cells and MEK (MAPK or ERK kinases) are immediate upstream inducers of MAPK activation. The current study investigated if aging might influence the activation and expression of MAPK and MEK in human T cells. Exposure of peripheral blood T cells from young subjects to PHA or cross-linked anti-CD3 monoclonal antibodies stimulated rapid increases in MAPK and MEK enzymatic activity. By contrast, significant reductions of MAPK and MEK activation were observed in stimulated T cells from 7 of 13 elderly subjects. Kinetic studies showed that the age-related impairments represented reduction in both the levels and duration of MAPK activation. In addition, Western immunoblot analysis did not reveal significant age-related differences in T cell expression of p42mapk/ERK2, p44mapk/ERK1, or MEK, suggesting impairments in upstream inducers of MEK/MAPK activation. Other experiments determined if agents that directly stimulate upstream Ras or Raf kinase components of the early MAPK cascade might reverse the age-related impairments of MAPK activation. Treatment of elderly T cells with fluoroaluminate (AlF(-)4), phorbol esters/Ca2+ ionophores, or okadaic acid stimulated increased MAPK activation compared to anti-CD3. However, these agents failed to restore MAPK activation in elderly T cells to the levels seen in young T cells. These results suggest that aberrancies in the MAPK activation cascade may underlie the age-related reductions of MAPK activation in human T cells stimulated via the TCR/CD3 complex.
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PMID:Age-related reductions in the activation of mitogen-activated protein kinases p44mapk/ERK1 and p42mapk/ERK2 in human T cells stimulated via ligation of the T cell receptor complex. 864 Aug 66


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