p59fyn tyrosine kinase regulates p56lck tyrosine kinase activity and early TCR-mediated signaling

To study the role of p59^fyn in T cell activation, we used antisenseRNA to inhibit p59^fyn expression in a T cell clone. Transfectantswith reduced levels of p59^fyn were functionally impaired intheir responses to antigen, Con A + recombinant IL-1 and cross-linkingwith anti-TCR mAb. Induction of tyrosine phosphorylation onmost intracellular substrates was greatly reduced. We also notedthat the Ick kinase activity was greatly reduced even thoughthe amount of Ick protein was equivalent to that present inparental D10 cells. Our results suggest that the protein tyrosinekinase p59^fyn is critical in TCR-mediated signaling and alsosuggests that p59^fyn may regulate p56^fyn tyrosine kinase activity.