APO-1(CD95)-mediated apoptosis in Jurkat cells does not involve src kinases or CD45

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Abstract
Tyrosine phosphorylation has been reported to be an early event required 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 compared two mutant Jurkat cells, one largely deficient in expression of CD45 (J45.01) and a second one deficient in expression of p56lck (JCaM1.6) with wild type Jurkat cells for their ability to undergo APO‐1‐induced apoptosis. No significant difference was observed among the three cell lines. In the mutant Jurkat cells APO‐1 triggering did not result in increased tyrosine phosphorylation of cytosolic proteins. Furthermore, herbimycin A did not inhibit but rather augmented apoptosis at concentrations which effectively degraded the src related kinases lck and fyn. The data suggest that APO‐1‐mediated signalling is independent from src kinases and CD45.