Bax-dependent caspase-3 activation is a key determinant in p53-induced apoptosis in neurons

p53 is a pivotal molecule regulating the death of neurons both after acute injury and during development. The molecular mechanisms by which p53 induce s apoptosis in neuronal cells, however, are not well understood. We have sh own previously that adenovirus-mediated p53 gene delivery to neurons was su fficient to induce apoptosis. In the present study we have examined the mol ecular mechanism by which p53 evokes neuronal cell death. Adenovirus-mediat ed delivery of p53 to cerebellar granule neurons resulted in caspase-3 (CPP 32) activation followed by terminal deoxynucleotidyl transferase-mediated b iotinylated UTP nick end labeling (TUNEL) staining and loss of viability as determined by an MTT survival assay. To determine whether Bax is essential for caspase-3 activation, p53 was expressed in Bax-deficient cells. Bax nu ll neurons did not exhibit caspase-3 activation in response to p53 and were protected from apoptosis. To determine whether Bax-dependent caspase-3 act ivation was required in p53-mediated neuronal cell death, caspase-3-deficie nt neurons were examined. Our results indicate that caspase-3-deficient neu rons exhibit a remarkable delay in apoptosis and a dramatic decrease in TUN EL-positive cells. These studies demonstrate that p53-induced cell death in postmitotic neurons involves a Bax-dependent caspase-3 activation, suggest ing that these molecules are important determinants in neuronal cell death after injury.