Time-dependent in vitro activation of caspase-8 by cytochrome c and dATP in extracts of BJAB cells.

Extracts from BJAB cells were incubated for different time periods in the presence or absence of 10 μM cytochrome c and 1 mM dATP. Then Western blot analyses were performed by the use of antihuman caspase-3 (A, upper panel) or antihuman caspase-8 antibodies (A, lower panel). Positions of molecular mass markers are indicated at the left. Arrows indicate the positions of procaspase-3 (*), the 17-kd active subunit of caspase-3 (**), procaspase-8 (#), and the 18-kd active subunit of caspase-8 (##). The experiments were repeated twice and yielded similar results. Additionally, caspase-3–like or caspase-8–like activities were measured in a colorimetric assay using Ac-DEVD-pNA or Ac-IETD-pNA, respectively (B). Caspase activities are given as mmol substrate cleaved per minute ± SD (n = 3).