Assuntos
Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Tirosina Quinases/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Receptores de Interleucina-2/fisiologia , Transdução de Sinais , Linfócitos T/imunologia , Células Cultivadas , Citosol/metabolismo , Ativação Enzimática , Humanos , Interleucina-2/farmacologia , Ativação Linfocitária , Proteínas Proto-Oncogênicas c-raf , Receptores de Interleucina-2/efeitos dos fármacos , Linfócitos T/efeitos dos fármacos , Linfócitos T/enzimologiaRESUMO
Stimulation of the interleukin-2 (IL-2) receptor results in phosphorylation and activation of cytosolic Raf-1 serine/threonine kinase. Herein, we report that enzymatically active Raf-1 is physically associated with the IL-2 receptor beta chain (p75) in T-cell blasts. Following stimulation with IL-2, Raf-1 dissociates from the IL-2 receptor complex and translocates to the cytosol. Genistein, a protein tyrosine kinase inhibitor, prevents the dissociation of enzymatically active Raf-1 from the ligand-stimulated IL-2 receptor complex. These data favor a model of IL-2 receptor activation in which an IL-2-activated protein tyrosine kinase phosphorylates the IL-2 receptor and/or receptor-bound Raf-1. Following tyrosine phosphorylation, enzymatically active Raf-1 dissociates from the IL-2 receptor and translocates into the cytosol.
Assuntos
Interleucina-2/farmacologia , Monócitos/metabolismo , Proteínas Quinases/sangue , Proteínas Tirosina Quinases/sangue , Proteínas Proto-Oncogênicas/sangue , Receptores de Interleucina-2/metabolismo , Western Blotting , Membrana Celular/metabolismo , Células Cultivadas , Citosol/metabolismo , Humanos , Interleucina-2/metabolismo , Metionina/sangue , Modelos Biológicos , Monócitos/imunologia , Proteínas Proto-Oncogênicas c-raf , Proteínas Recombinantes/metabolismo , Proteínas Recombinantes/farmacologiaRESUMO
Interleukin-2 (IL-2) stimulates proliferation of T lymphocytes and is involved in the activation of both natural killer and lymphokine-activated killer precursor cells. The intracellular messengers which mediate IL-2-dependent events have not yet been identified. IL-2 receptor is not a protein-tyrosine kinase. Activation of a cellular protein-tyrosine kinase and direct association of a protein-tyrosine kinase activity with the IL-2 receptor occurs within minutes of IL-2 stimulation. We investigated the activation of phosphatidylinositol 3-kinase (PI 3-kinase) in IL-2-mediated signal transduction using the IL-2-dependent murine T-cell line, CTLL-2, and human phytohemagglutinin-stimulated peripheral blood lymphocytes (phytohemagglutinin blasts). Within a minute following stimulation of these cells with IL-2, PI 3-kinase activity could be detected in antiphosphotyrosine (anti-P-Tyr) antibody immunoprecipitates. IL-2 triggered a direct association of PI 3-kinase with the IL-2 receptor as detected in immunoprecipitates using anti-IL-2 receptor beta chain antibody. In vivo labeled CTLL-2 cells have a time-dependent increase in D-3-phosphorylated polyphosphoinositides following stimulation with IL-2. This is the first group of second messengers identified in IL-2-mediated signal transduction.
