The combination of bcl-2 expression and NGF-deprivation facilitates the selective destruction of BAD protein in living sympathetic neurons.
Bcl-2 overexpression prevents neuronal death after injury or neurotrophic factor-deprivation but the biochemical consequences of survival maintenance by Bcl-2 have hardly been explored. We show that unlike NGF, adenovirally delivered hBcl-2 supports the survival of over 80% of the neurons without activating ERK and Akt phosphorylation, or suppressing JNK phosphorylation, or enhancing cell growth. However, the proapoptotic protein BAD, whose phosphorylation is induced by NGF, is degraded in NGF-deprived neurons expressing hBcl-2, while the level of Bcl-xL remains unaffected. Interestingly, degradation of BAD protein is prevented by the pan-caspase inhibitor Boc.Asp(OMe)fmk. We propose that NGF-deprivation promotes dephosphorylation of BAD while hBcl-2 facilitates its release into the cytoplasm where it is degraded by noncaspase, Boc.Asp(O-Me)fmk-inhibitable proteases. The potential importance of BAD degradation is suggested by our finding that overexpressed BAD kills NGF-maintained sympathetic neurons by apoptosis, while hBcl-2 prevents BAD-induced death.
Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QW, United Kingdom.
M L
ML
Roberts
K
K
Virdee
C P
CP
Sampson
I
I
Gordon
P
P
Parone
A M
AM
Tolkovsky
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D015870:Gene Expression / Q000502:physiology; D005822:Genetic Vectors; D020932:Nerve Growth Factor / Q000494:pharmacology*; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics*; D051381:Rats; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D013564:Sympathetic Nervous System / Q000166:cytology*; D051025:bcl-Associated Death Protein
C494821:Bad protein, rat; D002352:Carrier Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051025:bcl-Associated Death Protein; D012694:Serine; D020932:Nerve Growth Factor