INDUCTION OF CPP32-LIKE ACTIVITY IN PC12 CELLS BY WITHDRAWAL OF TROPHIC SUPPORT - DISSOCIATION FROM APOPTOSIS

Inhibitors of interleukin-1 beta converting enzyme (ICE) and a related group of cysteine aspartases of the ICE/ced-3 family inhibit cell dea th in a variety of settings, including in PC12 cells and sympathetic n eurons following withdrawal of trophic support. To assess the particul ar member(s) of the ICE/ced-3 family that are relevant to cell death a nd to position their activation within the apoptotic pathway, we have used specific substrates to measure ICE-like and CPP32-like enzymatic activity in naive and neuronally differentiated PC12 cells that had be en deprived of trophic support (nerve growth factor and/or serum). Rap id induction of CPP32-like, but not ICE-like, activity was observed. c -Jun kinase activation and the action of bcl-2 and other survival agen ts, such as cell cycle blockers, a NO generator, N-acetylcysteine, aur intricarboxylic acid, and actinomycin D occurred at a point further up stream in the apoptotic pathway compared with the aspartase activation . In living cells, zVAD-FRIR, a pseudosubstrate aspartase inhibitor, b locked the activity/activation of the aspartase at concentrations abou t one order of magnitude lower than those required to promote survival , raising the possibility that the CPP32-like aspartase is not the mai n death effector in this model.