Fig. 2. TIAM1 is cleaved in a zVAD-inhibitable manner in three distinct apoptotic systems. Cells were exposed to their respective apoptotic stimuli for the indicated times. Cells were harvested, immunoprecipitated with antibody against the COOH terminus of TIAM1, and then immunoblotted with the same antibody. A, Jurkat cells were treated with antibodies against Fas (100 ng/ml); B, PC12 cells were subjected to serum withdrawal; C, HMN1 cells were treated with C2-ceramide (50 µM). Where indicated, zVAD was added to a final concentration of 50 µM, which is sufficient to block apoptosis in all three cell types. Arrowhead, Mr 75,000 cleavage product.