a. Fluorogenic substrate cleavage activity of recombinant purified FKBP-caspase-8WT or non-cleavable FKBP-caspase-8DA in the presence of recombinant purified FRB-FLIP, a compound that induces FKBP-FRB heterodimers (heterodimerizer), or FRB-FLIP and heterodimerizer. ND indicates none detected. (Error bars are s.d., n=3) b. Western blot analysis of RIPK3−/−:Caspase-8−/− (DKO) MEF stably expressing the indicated mutants of caspase-8 and RIPK3. Caspase-8CA indicates catalytically inactive caspase-8. c, d. Cell death assessed by propidium iodide (PI) uptake of DKO MEF expressing the indicated caspase-8 mutants in the absence (c) or presence (d) of stably expressed RIPK3, following transfection with scramble or FLIP-targeted siRNA, and 12 hours TNF treatment. (Error bars are s.d., n=3) e, f. Cell death (PI uptake) of SVEC 4–10 cells stably expressing RIPK3 specific (e) or scramble (f) shRNA, transfected with the indicated siRNAs and treated with TNF for 12 hours. (Graph is mean of 2 independent experiments, error bars indicate range) g. Cell death (PI uptake) of L929 cells expressing scramble or RIPK3-specific shRNA, transfected with siRNAs specific for caspase-8 and/or FLIP as indicated. Death was assessed 48h post-transfection. (Error bars are s.d., n=3.) The data presented are representative of results obtained with either of 2 separate siRNAs to both caspase-8 and FLIP.