BAX translocation is a critical event in neuronal apoptosis: regulation by neuroprotectants, BCL-2, and caspases.
Members of the BCL-2 family of proteins either promote or repress programmed cell death. Here we report that neonatal sympathetic neurons undergoing apoptosis after nerve growth factor (NGF) deprivation exhibited a protein synthesis-dependent, caspase-independent subcellular redistribution of BAX from cytosol to mitochondria, followed by a loss of mitochondrial cytochrome c and cell death. Treatment with elevated concentrations of the neuroprotectants KCl or cAMP at the time of deprivation prevented BAX translocation and cytochrome c release. However, administration of KCl or cAMP 12 hr after NGF withdrawal acutely prevented loss of mitochondrial cytochrome c, but not redistribution of BAX; rescue with NGF acutely prevented both events. Overexpression of Bcl-2 neither altered the normal subcellular localization of BAX nor prevented its redistribution with deprivation but did inhibit the subsequent release of cytochrome c, caspase activation, and cell death. Bcl-2 overexpression did not prevent cell death induced by cytoplasmic microinjection of cytochrome c into NGF-deprived competent-to-die neurons. These observations suggest that the subcellular redistribution of BAX is a critical event in neuronal apoptosis induced by trophic factor deprivation. BCL-2 acts primarily, if not exclusively, at the level of mitochondria to prevent BAX-mediated cytochrome c release, whereas NGF, KCl, or cAMP may abort the apoptotic program at multiple checkpoints.
Putcha
G V
GV
Departments of Neurology and Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Deshmukh
M
M
Johnson
E M
EM
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000502:physiology*; D020169:Caspases / Q000378:metabolism*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000378:metabolism; D008959:Models, Neurological; D009414:Nerve Growth Factors / Q000502:physiology*; D009474:Neurons / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D018696:Neuroprotective Agents / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D017783:Superior Cervical Ganglion / Q000166:cytology / Q000502:physiology*; D051028:bcl-2-Associated X Protein
C494827:Bax protein, mouse; D003574:Cytochrome c Group; D009414:Nerve Growth Factors; D018696:Neuroprotective Agents; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D011189:Potassium Chloride; D000242:Cyclic AMP; D020169:Caspases