Stimuli that induce a cholinergic neuronal phenotype of NG108-15 cells upregulate ChAT and VAChT mRNAs but fail to increase VAChT protein

The vesicular acetylcholine transporter (VAChT) and choline acetyltransfera se (ChAT) are encoded by genes organized in a single gene locus, and coregu lation of the transcription of the two genes has been repeatedly reported i n cholinergic tissues. In the present study, different stimuli were used to induce the differentiation of the hybridoma cells NG108-15 and we examined their effects on the modulation of VAChT and ChAT expression at the mRNA a nd protein levels. All agents upregulated the VAChT and ChAT mRNA levels, b ut to a different extent, ChAT activity was increased by retinoic acid, dex amethasone, and dibutyrylcyclic AMP (dbcAMP), and a synergistic effect was observed with a combined dexamethasone and dbcAMP treatment. Nonetheless, n o changes in the VAChT protein level could be observed, as judged from liga nd binding studies as well as from immunochemical detection. Hemicholinium- 3-sensitive choline uptake, hemicholinium-3 binding, and acetylcholine cont ent were increased by differentiating agents, with a rank order of potency comparable to their effects on ChAT activity. Prominent changes were observ ed in the expression of vesicular protein markers, particularly with the as sociated treatment dexamethasone and dbcAMP. Thus, it appears that although the different stimuli we have been using are able to stimulate neuronal fe atures and activate the transcription of cholinergic genes, they did not co ntrive to increase the level of VAChT protein in these cells. (C) 2001 Else vier Science Inc.