Reconstitution of T Cell Receptor ζ-Mediated Calcium Mobilization in Nonlymphoid Cells

Abstract
T cell antigen receptor (TCR) activation involves interactions between receptor subunits and nonreceptor protein tyrosine kinases (PTKs). Early steps in signaling through the ζ chain of the TCR were examined in transfected COS-1 cells. Coexpression of the PTK p59 fynT , but not p56 lck , with ζ or with a homodimeric TCRβ-ζ fusion protein produced tyrosine phosphorylation of both ζ and phospholipase C (PLC)-γ1, as well as calcium ion mobilization in response to receptor cross-linking. CD45 coexpression enhanced these effects. No requirement for the PTKZAP-70 was observed. Thus, p59 fynT may link ζ directly to the PLC-γ1 activation pathway.