NEDD2 IS REQUIRED FOR APOPTOSIS AFTER TROPHIC FACTOR WITHDRAWAL, BUT NOT SUPEROXIDE-DISMUTASE (SOD1) DOWN-REGULATION, IN SYMPATHETIC NEURONS AND PC12 CELLS

Activation of cysteine aspartases (caspases) seems to be a required el ement of apoptotic death in many paradigms. We have shown previously t hat general inhibitors of cysteine aspartases block apoptosis of PC12 cells and sympathetic neurons evoked by either trophic factor (nerve g rowth factor and/or serum) deprivation or superoxide dismutase (SOD1) downregulation. Moreover, activation of a caspase family member simila r or equivalent to the interleukin-1 beta-converting enzyme (ICE) was implicated for death caused by SOD1 downregulation, but not withdrawal of trophic support. The experiments presented here demonstrate that d iminished expression of the cysteine aspartase Nedd2 in PC12 cells and sympathetic neurons induced by an appropriate vector peptide-linked a ntisense oligonucleotide rescues them from death caused by trophic fac tor deprivation without inhibiting apoptosis in the same cell types ev oked by SOD1 downregulation. Neither the level (as revealed by Western immunoblotting) nor the cellular distribution (as revealed immunohist ochemical ly) of Nedd2 was altered demonstrably by trophic factor depr ivation. However, evidence for proteolytic processing of Nedd2 (consis tent with commencement of activation) was observed in PC12 cells after withdrawal of trophic support. These findings indicate that neuronal death triggered by different initial causes may be mediated by distinc t members of the cysteine aspartase family.