Figure 6.

Caspase-8 processing is defective in tafazzin-deficient cells. (A) A schematic diagram of caspase-8 autoprocessing during Fas-mediated apoptosis. (B) Control and Barth syndrome–derived lymphoblastoid cells were treated as in Fig. 5 A and analyzed by Western blotting for caspase-8 cleavage. Two different antibodies were used: anti-DED of caspase-8 and anti-p18 domain (which also detects the cleaved p43 form). (C) Control and tafazzin-knockdown HeLa cells were treated as in Fig. 5 B and analyzed for caspase-8 cleavage as in B. (D) The different HeLa-derived clones were treated with anti-Fas antibody as indicated for 14 h. The lysates were incubated with biotin–VAD-fmk to precipitate active caspases, and active caspase-8 was detected by immunoblotting. The graph represents a densitometric analysis of the p43 immunoblot as a percentage of total actin levels. (E) MCF-7 cells were either left untreated or treated with either TNF-α together with cycloheximide (TNF-α) or anti-Fas antibody (Fas). Caspase-8 processing was assessed by the anti-p18 antibody. (F) shCont1 and Bcl-xL–expressing HeLa cells were treated as in Fig. 5 B, and caspase-8 activation was assessed by anti-DED (top) or anti-p18 (middle) antibodies.