Decreased expression of procaspase-2L prevents activation of the mitochondrial pathway to cell death.

(A) The appearance of the active p19 and p17 fragments of caspase-3 was detected by Western blot analysis in U937/neo and U937/AS3 after anti-Fas Ab treatment. HSC-70 expression level is shown as protein loading control in each lane. (B) Kinetics of DEVD-AMC hydrolysis in U937/neo (●) and U937/AS3 (○) cells. Enzyme activities were measured as initial velocities and expressed relative to control untreated cells. One representative of 2 independent experiments is shown. (C) Subcellular localization of cyctochrome c was performed from enriched mitochondrial (MIT) and cytosolic (CYT) extracts prepared from control and anti-Fas Ab–treated (6 hours) U937/neo and U937/AS3 cells. (D) Expression of Bid was monitored in U937/neo and U937/AS3 cells by Western blot analysis at indicated times after anti-Fas Ab treatment.