THE CAMP-DEPENDENT PROTEIN-KINASE REGULATES TRANSCRIPTION OF THE DOPAMINE-BETA-HYDROXYLASE GENE

Dopamine beta-hydroxylase (DBH) catalyzes the conversion of dopamine t o norepinephrine, and is expressed specifically in neurons and neuroen docrine cells that release norepinephrine and epinephrine. In the pres ent study, we used DBH-expressing human neuroblastoma SK-N-BE(2)C and rat pheochromocytoma (PC12) cell lines to investigate the role of cAMP -dependent protein kinase (PKA) in transcriptional regulation of the D BH gene. Coexpression of the catalytic subunit of PKA (PKA(c)) robustl y stimulated the transcriptional activity of the DBH gene in a dose-de pendent manner. Conversely, coexpression of a specific inhibitor of PK A abrogated forskolin- and cAMP-mediated but not phorbol ester-mediate d transcriptional induction of DBH. Deletion of the cAMP response elem ent (CRE) dramatically reduced the stimulatory effect of PKA, indicati ng that the CRE mediates the induction of DBH by PKA. In DBH-nonexpres sing HeLa and C6 glioma cell lines, coexpression of PKA, changed the t ranscriptional activity of the DBH promoter to a minimal degree, indic ating that basal and PKA-mediated transcription of the DBH gene occur in a cell type-specific manner. Finally, both basal and cAMP-stimulate d transcription of the DBH gene are diminished in three PKA-deficient PC12 cell lines, compared to wild-type cells. Based on these data, we conclude that PKA, via the CRE, plays an important role in basal and c AMP-inducible transcription, but is not required for phorbol ester-med iated induction, of the DBH gene in noradrenergic cells. The present r esults, together with previous evidence supporting a critical role for PKA in the transcriptional regulation of the tyrosine hydroxylase (TH ) gene, suggest that the PKA pathway can regulate transcription of the TH and DBH genes in a coordinated fashion.