Regulation of src family tyrosine kinases in lymphocytes (original) (raw)
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Activation of human T cells is associated with tyrosine phosphorylation of several cellular proteins
Cellular Signalling, 1989
Human T lymphocytes are activated to proliferate after triggering the TCell Antigen Receptor Complex, CD3-Ti, with either antigen, mitogenic lectins or monoclonal antibodies against its different subunits. Stimulation of Jurkat leukemic human T cells with anti-CD3 or anti-Ti monoclonal antibodies was found to induce, within 1 min, an increase in the phosphorylation of a set of cellular proteins that can be precipitated with anti-phosphotyrosine antibodies. Seven phosphotyrosine-containing proteins were separated with respective mol. wt of 21, 25, 38, 55, 70, 80 and 110 kDa, among which the 38 kDa species is predominant. Moreover, incubation of Jurkat Tcells with sodium orthovanadate, a potent inhibitor of phosphotyrosine proteinphosphatases, was found to potentiate the effects of anti-CD3 mAb on tyrosine phosphorylation. In addition vanadate also induced IL-2 secretion in Jurkat cells when associated with the phorbol ester TPA, further demonstrating the importance of these phosphorylation reactions in the process of T cell activation.
Inhibition of tyrosine phosphorylation prevents T-cell receptor-mediated signal transduction
Proceedings of the National Academy of Sciences, 1990
The binding ofantigen to the multicomponent T-cell receptor (TCR) activates several signal transduction pathways via coupling mechanisms that are poorly understood. One event that follows antigen receptor engagement is the activation of inositol phospholipid-specific phospholipase C (PLC). TCR activation by antigen, lectins, or anti-TCR monoclonal antibody has also been showu to cause increases in tyrosine phosphorylation of TCR-C and other substrates, sug-
Proceedings of the National Academy of Sciences, 1991
Stimulation of the T-cell antigen receptor (TCR), which itself is not a protein-tyrosine kinase (PTK), activates a PTK and phospholipase C (PLC). Using the human T-cell leukemic line Jurkat and normal peripheral blood lymphocytes, we demonstrate that stimulation of the TCR specifically induces the recovery of PLC activity in eluates from anti-phosphotyrosine immunoprecipitates. Stimulation of the human muscarinic receptor, subtype 1, when expressed in Jurkat activates PLC through a guanine nucleotide binding protein but does not induce the recovery of PLC activity in eluates from anti-phosphotyrosine immunoprecipitates. Western blot analysis reveals that PLC-y1 is tyrosine-phosphorylated in response to TCR stimulation. Nearly all of the PLC activity recovered in eluates from anti-phosphotyrosine immunoprecipitates was depleted by anti-PLC-yl antibodies. Stimulation of the TCR on mutants derived from Jurkat that are defective in TCR-induced PLC activation results in markedly reduced, if any, PLC activity recovered in phosphotyrosine immunoprecipitates and in no detectable PLC-yl tyrosine phosphorylation. Thus, the TCR functions like PTK growth factor receptors, but through an indirect interaction, to induce tyrosine phosphorylation of PLC-y1. Since other studies have implicated two members of the src family of PTKs in TCRmediated signal transduction, our findings suggest that the induction of tyrosine phosphorylation of PLC--1 by a mechanism involving a src-like kinase may be the means by which the TCR regulates PLC activity in T cells.
European Journal of Immunology, 1989
Human T cells can be activated and induced to proliferate through either the antigen-specific receptor complex (TcR-CD3) or the CD2 surface molecule. Following stimulation, both serine and tyrosine phosphorylation of cellular protein have been demonstrated to occur. P S~"~, a protein tyrosine kinase associated to the inner face of the plasma membrane, is almost exclusively expressed in lymphoid cells, especiallyTcel1s.Within minutes after activation of a human Tcell-derived line (Jurkat) via stimulation of either the TcR-CD3 complex or the CD2 glycoprotein, we observed a hyperphorphosylation of p56Ick. A concomitant shift to a higher molecular weight in sodium dodecyl sulfatepolyacrylamide gel was also observed. Similar changes were obtained with phorbol 12-myristate 13-acetate. Tryptic phosphopeptide analysis of the hyperphosphorylated form of pS6lck yielded new phosphorylated sites in serine residues and an increased tyrosine phosphorylation. These results suggest that pS6Ick may be intimately connected to the signaling pathway in T cell activation.
Journal of Biological Chemistry
Treatment of rat basophilic leukemia cells (RBL-2H3) with antigen or ionophore leads to an increase in cellular protein tyrosine phosphorylation. Three major proteins of molecular mass of 72,92, and 110 kDa are targeted by antigen and a 110-kDa species by ionophore, A23187. The antigen-and ionophore-induced tyrosine phosphorylation responses are dose-dependent and correlate with increases in serotonin release from activated cells. The presence of extracellular Ca2+ is required to sustain the antigen-and ionophore-stimulated tyrosine phosphorylation as well as mediator release. A protein tyrosine kinase inhibitor, RG 50864, differentially inhibits the antigen-stimulated tyrosine phosphorylation in the decreasing order of 72,91, and 110-kDa proteins. The compound inhibition of the 72-kDa protein tyrosine phosphorylation correlates with that of serotonin release. In ionophore-stimulated cells, the inhibition of the 110-kDa protein tyrosine phosphorylation and serotonin release by RG 50864 occurs in parallel. These results suggest that the 72-and 110-kDa phosphoproteins may represent the respective regulators of serotonin release in antigen-and ionophore-activated cells. The 110-kDa tyrosine phosphorylated proteins from antigen-and ionophore-stimulated cells exhibit identical electrophoretic mobility and VS protease-generated phosphopeptide maps, suggesting that these two proteins may be the same. These results provide new evidence that both the stimulatory actions of antigen and ionophore on mediator release are mediated through enhanced protein tyrosine phosphorylation in RBL-2H3 cells. Significantly, the present study suggests the presence of multiple tyrosine phosphorylation signaling pathways in RBL cells and that their selective utility may be determined by the nature of the stimulus.