AP1 proteins mediate the cAMP response of the dopamine β-hydroxylase gene

Abstract

Neurotransmitter biosynthesis is regulated by environmental stimuli, which transmit intracellular signals via second messengers and protein kinase pathways. For the catecholamine biosynthetic enzymes, dopamine β-hydroxylase and tyrosine hydroxylase, regulation of gene expression by cyclic AMP, diacyl glycerol, and Ca2+ leads to increased neurotransmitter biosynthesis. In this report, we demonstrate that the cAMP-mediated regulation of transcription from the dopamine β-hydroxylase promoter is mediated by the AP1 proteins c-Fos, c-Jun, and JunD. Following treatment of cultured cells with cAMP, protein complexes bound to the dopamine β-hydroxylase AP1/cAMP response element element change from consisting of c-Jun and JunD to include c-Fos, c-Jun, and JunD. The homeodomain protein Arix is also a component of this DNA-protein complex, binding to the adjacent homeodomain recognition sites. Transfection of a dominant negative JunD expression plasmid inhibits cAMP-mediated expression of the dopamine β-hydroxylase promoter construct in PC12 and CATH.a cells. In addition to the role of c-Fos in regulating dopamine β-hydroxylase gene expression in response to cAMP, a second pathway, involving Rap1/BRaf is involved. These experiments illustrate an unusual divergence of cAMP-dependent protein kinase signaling through multiple pathways that then reconverge on a single element in the dopamine β-hydroxylase promoter to elicit activation of gene expression.