title: T cell receptor-induced phosphorylation of Sos requires activity of CD45, Lck, and protein kinase C, but not ERK.
abstract: Stimulation of the T cell antigen receptor (TCR) activates signaling pathways involving protein kinases, phospholipase Cgamma1, and Ras. How these second messengers interact to initiate distal activation events is an area of intense scrutiny. In this report, we confirm that TCR ligation results in phosphorylation of Sos, a guanine nucleotide exchange factor for Ras. This requires expression of both the CD45 tyrosine phosphatase and the Lck protein tyrosine kinase and depends upon signaling via protein kinase C. In contrast to previous studies examining requirements for Sos phosphorylation following insulin and epidermal growth factor receptor engagement, we show that TCR-induced phosphorylation of Sos does not require activation of the mitogen-activated protein kinase/extracellular-signal regulated kinase (MEK/ERK) pathway. However, the basal phosphorylation of Sos in T cells is affected by either MEK or MEK-dependent kinases. Although Sos phosphorylation results in its dissociation from Grb2 following insulin stimulation in Chinese hamster ovary cells, TCR engagement on the Jurkat T cell line fails to elicit a similar effect. These data demonstrate that the kinases responsible for Sos phosphorylation differ following ligation of various cell surface receptors and that the consequences of Sos phosphorylation relies, at least in part, on sites of its phosphorylation.
authors.affiliation: Molecular Biology Program, University of Iowa, Iowa City, Iowa 52242, USA.
authors.forename: H
authors.initials: H
authors.lastname: Zhao
authors.forename: Y Y
authors.initials: YY
authors.lastname: Li
authors.forename: R V
authors.initials: RV
authors.lastname: Fucini
authors.forename: S E
authors.initials: SE
authors.lastname: Ross
authors.forename: J E
authors.initials: JE
authors.lastname: Pessin
authors.forename: G A
authors.initials: GA
authors.lastname: Koretzky
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D051380:GRB2 Adaptor Protein; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D017493:Leukocyte Common Antigens / Q000502:physiology*; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D048369:MAP Kinase Kinase 1; D008565:Membrane Proteins / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D010768:Phosphoserine / Q000378:metabolism; D010769:Phosphothreonine / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D015398:Signal Transduction; D020664:Son of Sevenless Proteins; D013601:T-Lymphocytes / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; D008565:Membrane Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D011948:Receptors, Antigen, T-Cell; D020664:Son of Sevenless Proteins; D010769:Phosphothreonine; D010768:Phosphoserine; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases; D017493:Leukocyte Common Antigens; D013755:Tetradecanoylphorbol Acetate