Fig. 5. Fas-mediated apoptosis is associated with the activation of p38 and ß isoforms. (A) A pan anti-p38 antibody was used to immunoblot immunoprecipitated p38 and p38ß, by using their respective specific antibodies. Fas-activation did not affect the cellular level of these kinases. (B) Fas induced phosphorylation of p38 and p38ß was detected by immunoprecipitating phosphorylated p38 using phospho-specific anti-p-38 antibody and immunoblotting with antibodies specific for p38 (blot 1) or p38ß (blot 2). (C) The expression of p38 is selectively abrogated in si-p38 cells (top panel) whereas p38ß was suppressed only in si-p38ß cells (bottom panel) (D) Expression of JNK1 and JNK2 was decreased in si-JNK1/2 cells.