Retinoic acid and nerve growth factor induce differential regulation of nicotinic acetylcholine receptor subunit expression in SN56 cells

Retinoic acid (RA) and nerve growth factor (NGF) have multiple functions in the regulation of neuronal development. In the present study, we characterized the expression of different nicotinic acetylcholine receptor (nAChR) subtypes in the cholinergic SN56 cell line and investigated the roles of RA and NGF in the expression of choline acetyltransferase (ChAT) and different nAChR subtypes. The nAChR agonist [3H]epibatidine was bound to two sites, with apparent affinities of 13 and 380 pM. RT‐PCR analysis revealed expression of α3, α4, α5, α7, β2, and β4 nAChR subunits. RA treatment induced morphological changes, and the mRNA level of ChAT was maximally elevated after 4 days of exposure. The density of [3H]epibatidine binding sites and the mRNA and protein level of the α3 and β2 nAChR subunits were also increased by RA‐induced differentiation. RA down‐regulated the mRNA and protein level of the α4 nAChR subunit, whereas no significant change was observed in the mRNA and protein level of the α7 nAChR subunit. NGF treatment increased the mRNA and protein level of the α3 and β2 nAChR subunits. No morphological effects of NGF were observed, and the mRNA level of ChAT and mRNA and protein level of the α4 and α7 nAChR subunits were not significantly altered. Validation was performed with real‐time RT‐PCR. The present results show that RA and NGF have different effects on the expression of ChAT and the morphology and the expression pattern of different nAChR subunits in cholinergic SN56 cells. © 2006 Wiley‐Liss, Inc.