CASPASE-2 (NEDD-2) PROCESSING AND DEATH OF TROPHIC FACTOR-DEPRIVED PC12 CELLS AND SYMPATHETIC NEURONS OCCUR INDEPENDENTLY OF CASPASE-3 (CPP32)-LIKE ACTIVITY

We have previously shown that caspase-2 (Nedd-2) is required for apopt osis induced by withdrawal of trophic support from PC12 cells and symp athetic neurons. Here, we examine the relationship of caspase-2 proces sing and cell death to induction of caspase-3 (CPP32)-like activity in PC12 cells. Caspase-2 processing, at a site tentatively identified as D333, led to the formation of an N-terminal 37 kDa product. This proc essing correlated temporally with induction of caspase-3-like activity . Agents previously shown to inhibit caspase-3-like activation, such a s bcI-2 and the Cdk inhibitor flavopiridol, also acted upstream of cas pase-2 processing. The general caspase inhibitors BAF and zVAD-FMK inh ibited N-terminal caspase-2 processing. In contrast, the more selectiv e caspase inhibitor DEVD-FMK inhibited the induction of caspase-3-like activity but did not affect caspase-2 processing or significantly sup press death in PC12 cells or sympathetic neurons. This indicates that caspase3-like activity is not required for either caspase-2 processing or apoptosis in this paradigm. An antisense oligonucleotide to caspas e-2 inhibited cell death but did not affect caspase-3-like activity, i ndicating that caspase-2 is not upstream of this activity and that act ivation of caspase-3-like caspases is not sufficient for death. Thus, in our paradigm, caspase-2 processing and caspase3-like activity are i nduced independently of each other. Moreover, although death requires caspase-2, caspase-3-like activity is neither necessary nor sufficient for death.