Apoptosis in cerebellar granule neurons is associated with reduced interaction between CREB-binding protein and NF-kappaB.
Cerebellar granule neurons undergo apoptosis when switched from medium containing depolarizing levels of potassium (high K+ medium, HK) to medium containing low K+ (LK). NF-kappaB, a ubiquitously expressed transcription factor, is involved in the survival-promoting effects of HK. However, neither the expression nor the intracellular localization of the five NF-kappaB proteins, or of IkappaB-alpha and IkappaB-beta, are altered in neurons primed to undergo apoptosis by LK, suggesting that uncommon mechanisms regulate NF-kappaB activity in granule neurons. In this study, we show that p65 interacts with the transcriptional co-activator, CREB-binding protein (CBP), in healthy neurons. The decrease in NF-kappaB transcriptional activity caused by LK treatment is accompanied by a reduction in the interaction between p65 and CBP, an alteration that is accompanied by hyperphosporylation of CBP. LK-induced CBP hyperphosphorylation can be mimicked by inhibitors of protein phosphatase (PP) 2A and PP2A-like phosphatases such as okadaic acid and cantharidin, which also causes a reduction in p65-CBP association. In addition, treatment with these inhibitors induces cell death. Treatment with high concentrations of the broad-spectrum kinase inhibitor staurosporine prevents LK-mediated CBP hyperphosphorylation and inhibits cell death. In vitro kinase assays using glutathione-S-transferase (GST)-CBP fusion proteins map the LK-regulated site of phosphorylation to a region spanning residues 1662-1840 of CBP. Our results are consistent with possibility that LK-induced apoptosis is triggered by CBP hyperphosphorylation, an alteration that causes the dissociation of CBP and NF-kappaB.
Yalcin
Asligul
A
Department of Molecular and Cell Biology, University of Texas at Dallas, Richardson 75083, USA.
Koulich
Elena
E
Mohamed
Salah
S
Liu
Li
L
D'Mello
Santosh R
SR
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D050882:CREB-Binding Protein; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D051381:Rats; D015534:Trans-Activators / Q000378:metabolism*; D051996:Transcription Factor RelA
D004791:Enzyme Inhibitors; D016328:NF-kappa B; D009687:Nuclear Proteins; D015534:Trans-Activators; D051996:Transcription Factor RelA; D050882:CREB-Binding Protein; C494365:Crebbp protein, rat; D010749:Phosphoprotein Phosphatases; D011188:Potassium