FIGURE 4.

Caspase-2 suppresses NF-κB activation and promotes apoptosis following 20 Gy of IR. Casp2^WT, Casp2^KO, Casp2^C320A, and Casp2^S139A MEFs were irradiated (20 Gy), and total cell lysates were prepared at indicated time points following IR and subjected to immunoblotting using an anti-phospho-IκBα (S32) antibody. A, actin was served as a protein-loading control. B and C, resistance to high dose (20 Gy) of IR-induced apoptosis in MEFs deficient in caspase-2 or reconstituted with catalytic dead or S139A mutant caspase-2 determined by caspase-3 cleavage using Western blotting (B) and caspase-3 activity using fluorogenic substrate assays (C).