Fig. 5.
Enhanced killing when Bax D68R is forced onto membranes. (A) MEF may possess sufficient endogenous Bcl-xL (blue) to counter the small fraction of membrane-bound Bax D68R (orange) (Fig. 2A). This capacity might be overwhelmed if the predominantly cytosolic Bax D68R is driven onto membranes. (B) Bax S184L is fully functional. The viability of reconstituted bax−/−bak−/− MEF (described in Fig. 2A) after etoposide treatment (0–10 μM) for 24 h was assessed by propidium iodide exclusion using flow cytometry. (C) Combining the deregulated D68R mutation with S184L enhances Bax-mediated apoptosis. Colony formation was assessed for parental bax−/−bak−/− MEF, or these MEF stably overexpressing Bcl-xL, after infection with retroviruses expressing WT Bax or mutant (D68R, S184L, or D68R/S184L) forms of Bax. Data represent means ± 1 SEM of 3 or more independent experiments. Results were compared using two-tailed unpaired Student's t tests. ns, P > 0.05.