APO-1(CD95)-MEDIATED APOPTOSIS IN JURKAT CELLS DOES NOT INVOLVE SRC KINASES OR CD45

Tyrosine phosphorylation has been reported to be an early event requir ed for APO-1/Fas(CD95) signalling in lymphocytes [Eischen, C.M., Dick, C.J. and Leibson, P.J. (1994) J. Immunol. 153, 1947-1954]. We have co mpared two mutant Jurkat cells, one largely deficient in expression of CD45 (J45.01) and a second one deficient in expression of p56(kk) (JC aM1.6) with wild type Jurkat cells for their ability to undergo APO-1- induced apoptosis, No significant difference was observed among the th ree cell lines. In the mutant Jurkat cells APO-1 triggering did not re sult in increased tyrosine phosphorylation of cytosolic proteins, Furt hermore, herbimycin A did not inhibit but rather augmented apoptosis a t concentrations which effectively degraded the src related kinases lc k and fyn. The data suggest that APO-1-mediated signalling is independ ent from src kinases and CD45.