Mitochondrial and extramitochondrial apoptotic signaling pathways in cerebrocortical neurons.
In cultured cerebrocortical neurons, mild excitotoxic insults or staurosporine result in apoptosis. We show here that N-methyl-d-aspartate (NMDA) receptor-mediated, but not staurosporine-mediated, apoptosis is preceded by depolarization of the mitochondrial membrane potential (Deltapsi(m)) and ATP loss. Both insults, however, release cytochrome c (Cyt c) into the cytoplasm. What prompts mitochondria to release Cyt c and the mechanism of release are as yet unknown. We examined the effect of inhibition of the adenine nucleotide translocator (ANT), a putative component of the mitochondrial permeability transition pore. Inhibition of the mitochondrial ANT with bongkrekic acid (BA) prevented NMDA receptor-mediated apoptosis of cerebrocortical neurons. Concomitantly, BA prevented Deltapsi(m) depolarization, promoted recovery of cellular ATP content, and blocked caspase-3 activation. However, in the presence of BA, Cyt c was still released. Because BA prevented NMDA-induced caspase-3 activation and apoptosis, the presence of Cyt c in the neuronal cytoplasm is not sufficient for the induction of caspase activity or apoptosis. In contrast to these findings, BA was ineffective in preventing staurosporine-induced activation of caspases or apoptosis. Additionally, staurosporine-induced, but not NMDA-induced, apoptosis was associated with activation of caspase-8. These results indicate that, in cerebrocortical cultures, excessive NMDA receptor activation precipitates neuronal apoptosis by means of mitochondrial dysfunction, whereas staurosporine utilizes a distinct pathway.
Budd
S L
SL
Center for Neuroscience and Aging Research, The Burnham Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA.
Tenneti
L
L
Lishnak
T
T
Lipton
S A
SA
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001865:Bongkrekic Acid / Q000494:pharmacology; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002540:Cerebral Cortex / Q000166:cytology*; D003574:Cytochrome c Group / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology / Q000502:physiology*; D000226:Mitochondrial ADP, ATP Translocases / Q000037:antagonists & inhibitors / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000502:physiology; D009474:Neurons / Q000166:cytology* / Q000187:drug effects; D010539:Permeability; D047428:Protein Kinase Inhibitors; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D019311:Staurosporine / Q000494:pharmacology
D003574:Cytochrome c Group; D004791:Enzyme Inhibitors; D009419:Nerve Tissue Proteins; D047428:Protein Kinase Inhibitors; D016194:Receptors, N-Methyl-D-Aspartate; D001865:Bongkrekic Acid; D000255:Adenosine Triphosphate; D000226:Mitochondrial ADP, ATP Translocases; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D019311:Staurosporine