title: Rapid tyrosine phosphorylation of Grb2 and Shc in T cells exposed to anti-CD3, anti-CD4, and anti-CD45 stimuli: differential effects of aging.
abstract: Two adapter proteins, Grb2 and Shc, have recently been implicated in the transmission of activation signals from the stimulated T cell receptor to Ras. We show here that in vitro stimulation of mouse splenic T cells with crosslinked anti-CD3 antibody leads within 30 s to phosphorylation of both Grb2 and Shc. Treatment with crosslinked anti-CD45 antibody leads to phosphorylation of Grb2 and also to a slight retardation in the mobility of this protein in an SDS polyacrylamide gel; both changes are seen within 30 s of crosslinking. Crosslinked anti-CD4 antibody leads to phosphorylation of Shc and to the phosphorylation of a 30-kDa protein that cross-reacts with anti-Grb2 antibodies. Aging leads to a decline in CD3-stimulated phosphorylation of Shc (but not Grb2), and to an increase in CD4-stimulated phosphorylation of Grb2, Shc, and the 30-kDa Grb2-like protein. Increased tyrosine-phosphorylation of Grb2 after exposure to either anti-CD3 or anti-CD45 suggests that Grb2 may be a common substrate for both CD3-linked kinases and the CD45 phosphatase. The differences between T cells from young and old mice suggest that aging may lead to a set of alterations in kinase/substrate coupling that contribute to immune dysfunction in the elderly, and that activation of the Ras pathway might be impaired by aging in T lymphocytes.
authors.affiliation: University of Michigan Institute of Gerontology, Ann Arbor 48109, USA.
authors.forename: J
authors.initials: J
authors.lastname: Ghosh
authors.forename: R A
authors.initials: RA
authors.lastname: Miller
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000375:Aging / Q000097:blood* / Q000276:immunology; D000818:Animals; D000911:Antibodies, Monoclonal; D001798:Blood Proteins / Q000378:metabolism*; D017252:CD3 Complex / Q000276:immunology; D015704:CD4 Antigens / Q000276:immunology; D051380:GRB2 Adaptor Protein; D017493:Leukocyte Common Antigens / Q000276:immunology; D008297:Male; D051379:Mice; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D013997:Time Factors
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000911:Antibodies, Monoclonal; D001798:Blood Proteins; D017252:CD3 Complex; D015704:CD4 Antigens; D051380:GRB2 Adaptor Protein; C495949:Grb2 protein, mouse; D011506:Proteins; D017493:Leukocyte Common Antigens; D017027:Protein Tyrosine Phosphatases