FIGURE 2.

Elimination of the interdomain autocleavage sites of caspase-8 abrogates its apoptosis inducing activity. Caspase-8-deficient I9.2 Jurkat cells (A and B) or the caspase-8-deficient neuroblastoma cell line NB7 (C and D) were stably transduced with full-length human caspase-8 or the indicated mutants. Equal expression of each mutant, as well as absence of endogenous caspase-8, was confirmed by Western blot for caspase-8 (A and C). Jurkat cells were treated with TRAIL (100 ng/ml) for 6 h, although NB7 cells were treated with 100 ng/ml TNFα + 5 μg/ml cycloheximide for 6 h. Following these treatments, cells were stained with annexin-V-allophycocyanin, and apoptosis was assessed by FACS. Vect., vector; Cat.Mut., catalytic mutant; CHX, cycloheximide.