Role of protein kinase C in signal attenuation following T cell receptor engagement.
T lymphocyte activation through stimulation of the T cell receptor complex and co-stimulatory receptors is associated with acute tyrosine phosphorylation of intracellular proteins, which in turn mediate downstream signaling events that regulate interleukin-2 expression and cell proliferation. The extent of protein tyrosine phosphorylation is rapidly attenuated after only 1-2 min of stimulation as a means of tightly controlling the initial signaling response. Here we show that this attenuation of tyrosine phosphorylation of Shc, CrkL, and the proto-oncogene Cbl is mimicked by treatment of mouse T lymphocytes or cultured Jurkat cells with phorbol 12-myristate 13-acetate. This effect is blocked by the specific protein kinase C inhibitor GF109203X, but not by PD98059, an inhibitor of MEK1/2 kinase. Activation of protein kinase C by phorbol ester also causes rapid (t(1)/(2) = 2 min) dissociation of both CrkL and p85/phosphoinositide 3-kinase from Cbl concomitant with Cbl tyrosine dephosphorylation. More important, GF109203X treatment of Jurkat cells prior to T cell receptor stimulation by anti-CD3/CD4 antibodies results in an enhanced (2-fold) peak of Cbl phosphorylation compared with that observed in control cells. Furthermore, the rate of attenuation of both Cbl tyrosine phosphorylation and its association with CrkL following stimulation with anti-CD3/CD4 antibodies is much slower in Jurkat cells treated with GF109203X. Taken together, these data provide strong evidence that one or more isoforms of phorbol ester-responsive protein kinase C play a key role in a feedback mechanism that attenuates tyrosine phosphorylation of proteins and reverses formation of signaling complexes in response to T cell receptor activation.
Program in Molecular Medicine and the Department of Biochemistry and Molecular Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
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Fernández
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Czech
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Meisner
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D006801:Humans; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D051379:Mice; D050722:Oncogene Protein v-cbl; D011493:Protein Kinase C / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D000090063:Proto-Oncogene Mas; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D015682:Retroviridae Proteins, Oncogenic / Q000378:metabolism; D055765:Shc Signaling Adaptor Proteins; D015398:Signal Transduction; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; C000715470:MAS1 protein, human; D050722:Oncogene Protein v-cbl; D011506:Proteins; D000090063:Proto-Oncogene Mas; D011948:Receptors, Antigen, T-Cell; D015682:Retroviridae Proteins, Oncogenic; C528024:SHC1 protein, human; D055765:Shc Signaling Adaptor Proteins; C528034:Shc1 protein, mouse; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D014443:Tyrosine; D011494:Protein Kinases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate