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)

An initial event in T cell activation is the specific adherence of T cells via their T cell receptor to the MHC peptide complex. We have studied this adherence by incubating T cells with preformed HLA DR4Dw4 peptide complexes attached to a solid support. Adherence of sodium 51Cr-labeled T cell clones specific for the influenza hemagglutinin peptide, HA 307-319, was maximal after 15 min and was specific for the HLA DR4Dw4-HA 307-319 complex. The binding was temperature dependent and could be blocked with azide or protein kinase C inhibitors, indicating that for adherence the T cells need to be metabolically active and have a functioning protein kinase C pathway. The adherence could be blocked with CD4- or CD3-reactive murine mAb, suggesting that the TCR and CD4 molecules work in concert to induce strong adherence to the HLA DR4Dw4-HA 307-319 complex. A subsequent event in T cell activation is proliferation, which is thought to need additional proteins such as IL-1 or other adhesion molecules. MHC peptide complexes coated on microtiter plates also induced proliferation in the human T cell clones. Removal of any monocytes by treatment of human T cell clones with anti-CD14 in conjunction with C, followed by purification over a nylon wool column, did not abrogate proliferation. After prolonged culture of the T cell clones in plates coated with peptide-pulsed HLA DR4Dw4 in the presence of IL-2, the T cell clones continued to proliferate in response to peptide. These results suggest that human T cell clones do not require a second signal from a monocyte or other APC to proliferate.
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PMID:Purified HLA class II peptide complexes can induce adherence and activation of peptide-specific human T cell clones. 153 49

Recent attention has focused on the role keratinocytes (KC) may play in the induction of T cell-mediated inflammatory responses in skin, particularly because KC, when activated by immunologic stimuli, express MHC class II Ag and secrete immunomodulatory cytokines. We tested the capacity of normal human KC that were stimulated with PMA to induce PBMC proliferation. PMA-treated, but not untreated, KC induced proliferation of allogeneic as well as autologous PBMC; in addition, when purified CD4+ or CD8+ T cells were used as responders, each subset proliferated. PBMC proliferation was not due to direct action of PMA on PBMC, nor to contamination of KC cultures with Langerhans cells (LC) or dermal APC. Pretreatment with different protein kinase C inhibitors abrogated the capacity of PMA-stimulated KC to induce proliferation. Paraformaldehyde-fixed PMA-KC stimulated PBMC proliferation, whereas supernatants from PMA-treated KC failed to do so, indicating that a membrane-associated activity on PMA-KC contributes to the induction of PBMC proliferation. PMA induced intercellular adhesion molecule-1 (ICAM-1) expression on KC; furthermore, mAb against ICAM-1 or against its ligand lymphocyte function-associated Ag (LFA-1) (CD11a/CD18) significantly, but incompletely, reduced the stimulatory capacity of PMA-treated KC, indicating that ICAM-1/LFA-1 interaction contributed to PBMC proliferation. IFN-gamma or TNF-alpha also induced ICAM-1 on KC, but these KC failed to stimulate proliferation, suggesting that PMA induces additional signals from KC, which act in concert with ICAM-1 to promote proliferation. Finally, mAb against HLA-ABC or HLA-DR did not inhibit proliferation. We conclude that PMA can activate KC to stimulate T cell proliferation in a MHC-independent fashion. This activation is mediated by protein kinase C and in part by the induction of ICAM-1 expression on KC.
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PMID:Phorbol myristate acetate-activated keratinocytes stimulate proliferation of resting peripheral blood mononuclear lymphocytes via a MHC-independent, but protein kinase C- and intercellular adhesion molecule-1-dependent, mechanism. 167 Sep 43

In nonobese diabetic (NOD) mice, T cells play a major role in mediating autoimmunity against pancreatic islet beta-cells. We and others previously reported that age-related alterations in the thymic and peripheral T cell repertoire and function occur in prediabetic NOD mice. To study the mechanism responsible for these T cell alterations, we examined whether a defect exists in the thymus of NOD mice at the level of TCR-mediated signaling after activation by Con A and anti-CD3. We found that thymocytes from NOD mice respond weakly to Con A- and anti-CD3-induced proliferation, compared with thymocytes from control BALB/c, BALB.B, (BALB.B x BALB.K)F1, C57BL/6, and nonobese non-diabetic mice. This defect correlates with the onset of insulitis, because it can be detected at 7 to 8 weeks of age, whereas younger mice displayed a normal T cell responsiveness. Thymic T cells from (NOD x BALB/c)F1 mice, which are insulitis- and diabetes-free, exhibit an intermediate stage of unresponsiveness. This T cell defect is not due to a difference in the level of CD3 and IL-2R expression by NOD and BALB/c thymocytes, and both NOD CD4+ CD8- and CD4- CD8+ mature thymic T cells respond poorly to Con A. BALB/c but not NOD thymic T cells respond to Con A in the presence of either BALB/c or NOD thymic APC, suggesting that the thymic T cell defect in NOD mice is intrinsic to NOD thymic T cells and is not due to an inability of NOD APC to provide a costimulatory signal. The defect can be partially reversed by the addition of rIL-2 to NOD thymocytes. To determine whether a defect in signal transduction mediates this NOD thymic T cell unresponsiveness, we tested whether these cells elevate their intracellular free Ca2+ ion concentration in response to Con A. An equivalent Con A-induced increase in Ca2+ ion concentration in both NOD and BALB/c thymocytes was observed, suggesting a normal coupling between the CD3 complex and phospholipase C in NOD thymocytes. In contrast to their low proliferative response to Con A or anti-CD3, NOD thymocytes respond normally (i.e., as do BALB/c thymocytes) to the combinations of PMA plus the Ca2+ ionophore ionomycin and PMA plus Con A but weakly to Con A plus ionomycin. Our data suggest that the age-related NOD thymocyte unresponsiveness to Con A and anti-CD3 results from a defect in the signaling pathway of T cell activation that occurs upstream of protein kinase C activation.
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PMID:Defective thymic T cell activation by concanavalin A and anti-CD3 in autoimmune nonobese diabetic mice. Evidence for thymic T cell anergy that correlates with the onset of insulitis. 182 15

Smooth muscle caldesmon was phosphorylated by protein kinase C up to 1.90 mol P/mol caldesmon. Phosphorylated caldesmon was completely digested by trypsin and the produced phosphopeptides were purified by C-8 and C-18 reverse phase chromatography. Four phosphopeptides were determined and two phosphoserines were identified. Both were localized in the C-terminal domain at serine-587 and serine-726. By following the time course of phosphorylation, serine-587 was found to be the preferred site. Effects of the phosphorylation of caldesmon by protein C on the inhibition of acto-H-meromyosin ATPase activity was also examined. While unphosphorylated caldesmon inhibited the ATPase activity by 60%, phosphorylated caldesmon hardly inhibited the ATPase activity. Therefore, it was concluded that the phosphorylation at serine-726 and serine-587 reverses the inhibitory activity of caldesmon.
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PMID:Determination of the phosphorylation sites of smooth muscle caldesmon by protein kinase C. 189 46

Effects of streptozotocin-induced diabetes and administration of the insulinmimetic agent, vanadate in rats on the liver protein kinase C-induced phosphorylation of exogenous C (Histone III-S) and endogenous substrates were investigated. Diabetes caused a significant fall (40-60%) in liver cytosolic protein C activity measured using both types of substrates. Vanadate treatment for a period of 5 weeks restored them to normal levels. Phosphorylation of cytosolic target proteins for protein kinase C followed a similar pattern in response to diabetes and vanadate. These treatments had no effect on particulate protein kinase C activity. Vanadate also had no effect in normal livers with respect to the protein kinase C system.
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PMID:Decrease of liver protein kinase C in streptozotocin-induced diabetic rats and restoration by vanadate treatment. 224 91

Presentation of Ag to type I CD4+ T cell clones by chemically fixed APC results in the induction of a long-lasting state of proliferative unresponsiveness in the T cell. Ag-specific TCR interactions do occur during this stimulation, as Ag- and Ia molecule-dependent increases in intracellular calcium free ion concentration can be demonstrated, yet free inositol phosphate generation is low and neither IL-2 synthesis nor proliferation occur. The addition of normal allogeneic accessory cells during this stimulation can restore the T cell proliferative response, as well as prevent the induction of unresponsiveness, thus defining an accessory cell-dependent costimulatory activity necessary for proliferation. We have now examined the biochemical effects of this costimulatory activity on early T cell activation. Normal accessory cell costimulatory activity was found to be incapable of augmenting the generation of free inositol phosphate in response to either fixed APC plus Ag or Con A alone. Furthermore, protein kinase C-dependent CD3 gamma-chain phosphorylation occurred in response to either fixed APC plus Ag or Con A alone, and the addition of normal accessory cells had no effect on the level of this phosphorylation. Finally, minimal CD3 zeta-chain tyrosine phosphorylation occurred during the induction of unresponsiveness with Ag and fixed APC alone and this also was not affected by the costimulatory activity. Our results demonstrate that T cell Ag receptor-mediated increases in intracellular calcium free ion concentration and protein kinase C activation occur independently of an accessory cell-derived costimulatory signal. In the absence of this costimulatory signal, these two intracellular second messengers are insufficient to induce a maximal proliferative response and in fact lead to a state of unresponsiveness.
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PMID:An accessory cell-derived costimulatory signal acts independently of protein kinase C activation to allow T cell proliferation and prevent the induction of unresponsiveness. 252 63

Thrombomodulin is an endothelial membrane anticoagulant protein that is a cofactor for protein C activation. We have evaluated the expression of thrombomodulin in cultured mouse hemangioma cells before and after treatment with phorbol myristate acetate (PMA), an agent that stimulates protein kinase C. We also isolated a cDNA encoding 481 amino acids of mouse thrombomodulin and the entire 3'-untranslated portion of its mRNA. The deduced amino acid sequence of mouse thrombomodulin is similar to those determined for human and bovine thrombomodulin. An S1 nuclease protection assay was used to measure thrombomodulin mRNA in hemangioma cells. The half-life for thrombomodulin mRNA was 8.9 +/- 1.8 h (S.D.) in cells treated with actinomycin D. Treatment with PMA had no effect on thrombomodulin mRNA levels. Thrombomodulin turnover was evaluated by immunoprecipitation of [35S]methionine-labeled thrombomodulin. The t1/2 was 19.8 +/- 3.9 h (S.D.); PMA treatment decreased the t1/2 to 10.9 +/- 1.1 h (S.D.) while increasing the rate of synthesis to a maximum of 190% of control. Protein C cofactor activity on hemangioma cells was reduced 35 +/- 4% by treatment with PMA within 30 min. This decrease was associated with a parallel decline in cell surface thrombomodulin antigen and with enhanced phosphorylation of thrombomodulin on serine residues. We conclude that thrombomodulin is phosphorylated in response to treatment of hemangioma cells with PMA which leads to decreased protein C cofactor activity and both increased degradation and synthesis of thrombomodulin.
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PMID:The structure and function of mouse thrombomodulin. Phorbol myristate acetate stimulates degradation and synthesis of thrombomodulin without affecting mRNA levels in hemangioma cells. 284 23

The adrenergic agonist norepinephrine is shown to stimulate endothelium to induce protein S release and degradation, leading to diminished anti-coagulant activity and to down-regulation of protein S cell surface-binding sites. Norepinephrine-induced release of intracellular protein S was blocked by the alpha 1-adrenergic antagonist prazosin (10(-7) M) but not by the alpha-adrenergic antagonist propranolol (10(-6) M) or the alpha 2-adrenergic antagonist yohimbine (10(-5) M) indicating that this response resulted from the specific interaction of norepinephrine with a class of alpha 1-adrenergic receptors not previously observed on endothelium. Attenuation of norepinephrine-induced release of protein S by pertussis toxin in association with the ADP-ribosylation of a 41,000-D membrane protein indicates that this intracellular transduction pathway involves a regulatory G protein. The observation that protein S was released from endothelium in response to maneuvers which elevate intracellular calcium or activate protein kinase C suggests that the response may be mediated via intermediates generated through the hydrolysis of phosphoinositides. Morphologic studies were consistent with a mechanism in which norepinephrine causes exocytosis of vesicles containing protein S. In addition to release of protein S, norepinephrine also induced loss of endothelial cell protein S-binding sites, thereby blocking effective activated protein C-protein S-mediated factor Va inactivation on the cell surface. Norepinephrine-mediated endothelial cell stimulation thus results in loss of intracellular protein S and suppression of cell surface-binding sites, modulating the anti-coagulant protein C pathway on the vessel wall. These studies define a new relationship between an anti-coagulant mechanism and the autonomic nervous system, and indicate a potential role for an heretofore unrecognized class of alpha 1-adrenergic receptors in the regulation of endothelial cell physiology.
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PMID:Norepinephrine down-regulates the activity of protein S on endothelial cells. 296 46

Models for T cell:B cell collaboration suggest that activated B cells process and present Ag to Th cells which subsequently induce B cell proliferation and differentiation. In contrast to activated B cells, resting B cells have generally been shown to be less efficient APC. If this model of T:B collaboration is physiologically correct, then resting B cells must undergo a phenotypic change that permits effective interaction with T cells. In this report, the requirement for rapid signaling through surface Ig on resting B cells for the induction of T:B interaction was investigated with an in vitro clustering assay. Resting splenic B cells were unable to form specific conjugates with T cell clones, unless the B cells were first treated with neuraminidase to remove sialic acid. In contrast, LPS-activated B cells were able to form conjugates without prior treatment. The ability of antibody against LFA-1 or L3T4 to inhibit cluster formation depended on the state of B cell activation in that anti-LFA-1 and anti-L3T4 mAb inhibited cluster formation by neuraminidase-treated resting B cells, but not by LPS-activated B cells. In addition, Ag-specific B cells which were isolated by their capacity to bind specific Ag were able to form clusters without any additional treatment. Moreover, treatment of resting splenic B cells with anti-mu-antibody induced clustering potential in B cells in as little as 10 min, suggesting that signaling through surface Ig was sufficient to induce this phenotypic change in B cells. Furthermore, activation of protein kinase C and Ca2+ mobilization were shown to be involved in that PMA and ionomycin treatment were also able to induce clustering potential in resting B cells. The rapid induction of clustering potential in resting B cells after signaling through surface Ig may represent a fundamental change in B cell physiology which occurs after recognition of specific Ag and may be required for effective cognate recognition between resting hapten-specific B cells and carrier-specific T cells. The potential role of desialylation for the induction of T:B interaction is discussed.
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PMID:The requirement for surface Ig signaling as a prerequisite for T cell:B cell interactions. A possible role for desialylation. 312 36

The protein C kinase activators 1-O-oleoyl, 2-O-acetylglycerol, 12-O-tetradecanoyl phorbol-13-acetate, and mezerein, stimulated deoxyglucose uptake in human neutrophils. The responses were stimulus specific since no effect was noted with the diether analogues 1-O-hexadecyl-2-O-ethylglycerol, 1-O-palmitoyl-2-O-acetyl or 1-O-palmitoyl-3-O-acetyl diesters of propanediol, or with 1,2-diolein. Stimulation of deoxyglucose uptake had the characteristics of carrier facilitated hexose transport. Stimulated uptake of deoxy-glucose was inhibited by trifluoperazine (10-30 microM). Activation of protein kinase C therefore appears to trigger events involved in hexose transport.
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PMID:Stimulation of hexose transport by human polymorphonuclear leukocytes: a possible role for protein kinase C. 315 45


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