Figure 4.

ER calcium agonists are unable to stimulate mitochondrial apoptosis in MEFs expressing Bak–cb5. (A) TG induces increased death in clones #2 and #6. Cells were treated with TG (5 μM) and cell death was measured by PI-staining 24 h later. (B) TG does not induce cytochrome c release. Cells were treated as in (A) in the presence of 100 μM zVAD.fmk, and stained for cytochrome c at the shown times. (C) Absence of caspase-3 and -9 processing induced by TG. Cells were treated with TG (5 μM) for the indicated times and lysed for western blotting. (D) C₂-ceramide and H₂O₂ fail to activate caspases in Bak–cb5-expressing cells. Cells were treated for the indicated times with C₂-ceramide (100 μM) or H₂O₂ (1 mM).