ORDERING THE CELL-DEATH PATHWAY - DIFFERENTIAL-EFFECTS OF BCL2, AN INTERLEUKIN-1-CONVERTING ENZYME FAMILY PROTEASE INHIBITOR, AND OTHER SURVIVAL AGENTS ON JNK ACTIVATION IN SERUM NERVE GROWTH FACTOR-DEPRIVED PC12 CELLS

Previous studies indicate that activation of c-Jun kinase (JNK) is nec essary for apoptosis of trophic factor-deprived PC12 cells and that de ath in this system is suppressed by multiple agents, including BCL2, i nhibitors of the interleukin-1-converting enzyme (ICE) family of prote ases, blockers of transcription, and a variety of small molecules with differing modes of action. Here, we determine the order in which thes e agents block apoptosis relative to JNK activation. Overexpression of BCL2 promotes PC12 cell survival and blocks JNK activation caused by trophic factor withdrawal. Similarly, the survival-promoting agents au rintricarboxylic acid, N-acetylcysteine, the nitric oxide generator di ethylenetriamine nitric oxide, 8-bromo-cGMP, and 8-(4-chlorophenylthio )-cAMP act upstream to inhibit JNK activation. In contrast, zVAD-fluor omethylketone (a permeant ICE family inhibitor), actinomycin D, and th e G(1)/S cell cycle inhibitor deferoxamine, all promote survival after trophic factor withdrawal, but do not affect JNK activation. These fi ndings are consistent with the presence of an ordered cell death pathw ay triggered by trophic factor deprivation in which 1) BCL2 and a numb er of survival-promoting agents act upstream of JNK, 2) ICE family pro tease actions, regulated genes required for cell death, and certain ce ll cycle blockers lie either downstream of JNK or on independent pathw ays required for apoptotic death.