Activation of tyrosine kinase p60fyn following T cell antigen receptor cross-linking.
Activation of T cells by specific antigens in the context of major histocompatibility complex encoded proteins is mediated by the T cell antigen receptor (TcR), consisting of a variable (Ti) and an invariant (CD3) subunits. Tyrosine phosphorylation is considered to be one of the earliest steps in TcR-mediated signal transduction. There are indications that the p60fyn protein tyrosine kinase is involved in signaling via TcR. However, enzymatic activation of the Src-related tyrosine kinases upon TcR triggering has not been shown yet, therefore the identity of TcR-activated tyrosine kinase(s) remains unclear. We demonstrate that cross-linking of CD3 activates p60fyn and induces tyrosine phosphorylation of cellular proteins in human T cells (resting peripheral T cells, a helper T cell clone, a helper T cell clone immortalized with Herpesvirus saimiri, and a leukemic T cell line). Activation of p60fyn was fast, and its maximum (2-4-fold activation as compared with the basal activity) was followed by a decline. The amount of p60fyn in the cells remained unchanged. None of the other T cell Src-related tyrosine kinases was activated after cross-linking of CD3. Activation of p60fyn was induced by anti-CD3, but not by anti-CD4, anti-CD2, or anti-CD28. The activation was correlated with an increase of the phosphotyrosine content of p60fyn. These studies provide direct proof for the functional association between p60fyn and the TcR.
Tsygankov
A Y
AY
Department of Molecular Biology, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, New Jersey 08543-4000.
Bröker
B M
BM
Fargnoli
J
J
Ledbetter
J A
JA
Bolen
J B
JB
D002478:Cells, Cultured; D003432:Cross-Linking Reagents; D004789:Enzyme Activation; D006801:Humans; D010766:Phosphorylation; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism
D003432:Cross-Linking Reagents; D011948:Receptors, Antigen, T-Cell; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases