Modulation of the Grb2-associated protein complex in human CD4+ T cells by receptor activation.
A panel of human CD4+ T cell clones was utilized to dissect and analyze the biochemical consequences of activation of CD3 or CD28. To molecularly characterize receptor-activated proximal signaling events, tyrosine-phosphorylated proteins co-precipitating with a Grb2 fusion protein after receptor activation were analyzed. Ligation of CD28, but not other costimulatory molecules, induced the tyrosine phosphorylation of two previously identified Grb2 binding proteins (pp76 and pp116). A third Grb2 binding protein (pp36) was extensively tyrosine phosphophorylated in response to combined CD3 and CD28 activation, but not in response to ligation of either receptor alone. cAMP and co-ligation of CD45 affected the receptor-activated tyrosine phosphorylation of Grb2-associated proteins. Furthermore, we demonstrated that two signaling molecules, Vav and phosphatidylinositol 3'-kinase (PI(3)K), also interacted with the Grb2 protein complex. The activity of PI(3)K was required for T cell activation, because wortmannin, a PI(3)K inhibitor, blocked T cell proliferation and cytokine production induced by ligation of CD3 and CD28. In conclusion, we demonstrate that in activated human T cell clones, the composition of Grb2 protein complex is modulated by costimulatory signals and cAMP, which may be important for the regulation of intracellular signal transduction.
Lahesmaa
R
R
Department of Leukocyte Biology, Syntex Research, Palo Alto, CA 94303, USA.
Allsup
A
A
Soderberg
C
C
Jackman
J
J
Findell
P
P
Peltz
G
G
D048868:Adaptor Proteins, Signal Transducing; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002999:Clone Cells; D000242:Cyclic AMP / Q000502:physiology; D066246:ErbB Receptors / Q000378:metabolism*; D051380:GRB2 Adaptor Protein; D006801:Humans; D008213:Lymphocyte Activation; D011506:Proteins / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D015398:Signal Transduction; D018417:Th1 Cells / Q000276:immunology
D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; D011506:Proteins; D011948:Receptors, Antigen, T-Cell; D000242:Cyclic AMP; D066246:ErbB Receptors