Activation of nuclear factor kappaB and Bcl-x survival gene expression by nerve growth factor requires tyrosine phosphorylation of IkappaBalpha.
NGF has been shown to support neuron survival by activating the transcription factor nuclear factor-kappaB (NFkappaB). We investigated the effect of NGF on the expression of Bcl-xL, an anti-apoptotic Bcl-2 family protein. Treatment of rat pheochromocytoma PC12 cells, human neuroblastoma SH-SY5Y cells, or primary rat hippocampal neurons with NGF (0.1-10 ng/ml) increased the expression of bcl-xL mRNA and protein. Reporter gene analysis revealed a significant increase in NFkappaB activity after treatment with NGF that was associated with increased nuclear translocation of the active NFkappaB p65 subunit. NGF-induced NFkappaB activity and Bcl-xL expression were inhibited in cells overexpressing the NFkappaB inhibitor, IkappaBalpha. Unlike tumor necrosis factor-alpha (TNF-alpha), however, NGF-induced NFkappaB activation occurred without significant degradation of IkappaBs determined by Western blot analysis and time-lapse imaging of neurons expressing green fluorescent protein-tagged IkappaBalpha. Moreover, in contrast to TNF-alpha, NGF failed to phosphorylate IkappaBalpha at serine residue 32, but instead caused significant tyrosine phosphorylation. Overexpression of a Y42F mutant of IkappaBalpha potently suppressed NFG-, but not TNF-alpha-induced NFkappaB activation. Conversely, overexpression of a dominant negative mutant of TNF receptor-associated factor-6 blocked TNF-alpha-, but not NGF-induced NFkappaB activation. We conclude that NGF and TNF-alpha induce different signaling pathways in neurons to activate NFkappaB and bcl-x gene expression.
Interdisciplinary Center for Clinical Research, Research Group "Apoptosis and Cell Death,", D-48149 Münster, Germany.
N T
NT
Bui
A
A
Livolsi
J F
JF
Peyron
J H
JH
Prehn
D000818:Animals; D000831:Animals, Newborn; D002470:Cell Survival; D003546:Cysteine Endopeptidases; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D006624:Hippocampus / Q000166:cytology; D020672:I-kappa B Proteins; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D020932:Nerve Growth Factor / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects; D016716:PC12 Cells; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis*; D012333:RNA, Messenger; D051381:Rats; D011916:Rats, Inbred F344; D012694:Serine; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014443:Tyrosine; D051020:bcl-X Protein
C494813:Bcl2l1 protein, rat; D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D009097:Multienzyme Complexes; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C000606206:Nfkbia protein, rat; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D051020:bcl-X Protein; D000072000:NF-KappaB Inhibitor alpha; D014443:Tyrosine; D012694:Serine; D020932:Nerve Growth Factor; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex