CREM and ICER are differentially implicated in trans-synaptic induction of tyrosine hydroxylase gene expression in adrenal medulla and sympathetic ganglia of rat.

Reserpine treatment leads to a trans-synaptic increase of the tyrosine hydroxylase (TH) gene transcription rate, mRNA and protein levels in catecholaminergic tissues including the adrenal medulla (AM) and the superior cervical ganglia (SCG). The TPA-responsive element plays an important role in the trans-synaptically-induced transcription of the TH gene in the AM, whereas it does not appear to be involved in the SCG (Trocmé et al. [1997] J. Neurosci. Res. 48:489-498). In this study, we show that another regulatory sequence of the TH proximal promoter, the cAMP-responsive element (CRE), binds different factors in the AM and in the SCG. To elucidate the dynamics of promoter regulation a complete time course analysis was conducted. Reserpine treatment enhances, between 1 hr and 8 hr after the injection, the expression and the binding of the repressor ICER in the AM, whereas in the SCG it enhances the binding of CREM factors. These results suggest that the mechanisms mediating trans-synaptic induction of the TH gene are different in the AM and SCG. The interplay between positive and negative transcription factors and their kinetics of action are responsive of the long-term regulation of the TH gene.