Ethanol Reduces Aspartyl‐(asparaginyl)‐β‐hydroxylase Protein Stability Through Increased GSK‐3β Activity: Relevance to Impaired Neuronal Migration in the Fetal Alcohol Syndrome

Abstract

Gestational exposure to ethanol causes fetal alcohol syndrome, which is associated with impaired neuronal migration in the central nervous system. Previous studies linked expression of aspartyl-(asparaginyl)-β-hydroxylase (AAH) to cell motility and showed that AAH was regulated by insulin and IGF-I stimulation. The present work examines the effects of ethanol on neuronal migration in the context of AAH expression. In an in vivo rat model of gestational ethanol exposure, and an in vitro culture model using human SH-Sy5y cells, impaired neuronal migration was associated with reduced levels of AAH protein expression by Western blot analysis and confocal microscopy. However, there were no associated reductions in AAH mRNA abundance, suggesting the effect was mediated at a post-transcriptional level. Since AAH protein has multiple GSK3β, CK2, and PKA phosphorylation sites, and ethanol increases both GSK3β and PKA activities, we examined the effects of ethanol on AAH protein phosphorylation. Immunoprecipitation/Western blot analysis demonstrated increased AAH phosphorylation in ethanol-treated cells, and increased AAH expression and motility in cells treated with chemical inhibitors of CK2, PKA, or GSK3β. These results suggest that ethanol impaired neuronal migration during development is mediated in part by GSK3β, and possibly PKA and CK2 phosphorylation followed by accelerated degradation of AAH protein in the brain. NIH # T32-DK060415