Activation of tyrosine hydroxylase (TH) gene transcription induced by brain-derived neurotrophic factor (BDNF) and its selective inhibition through Ca²⁺ signals evoked via the N-methyl-d-aspartate (NMDA) receptor

Tyrosine hydroxylase (TH) is the rate-limiting enzyme in the biosynthesis of catecholamine but its transcriptional regulation is not fully understood. Using a reporter assay with cultured rat cortical neurons, we demonstrated that the TH gene promoter was activated by brain-derived neurotrophic factor (BDNF), through its specific receptor TrkB and the ERK/MAP kinase pathway. Using a series of mutant TH gene promoters, we found that the cAMP-response element (CRE) plays a crucial role in the TH promoter activity and the Egr-1-responsive element (ERE), at least in part, is responsible for the BDNF-induced activation. Notably, the influx of Ca²⁺ evoked via the N-methyl-d-aspartate receptor (NMDA-R) but not via the L-type voltage-dependent Ca²⁺ channel (L-VDCC) selectively antagonized the activation of the gene promoter, suggesting a new link between the catecholaminergic and glutamatergic systems. The Ca²⁺ signals evoked via NMDA-R did not affect the phosphorylation of ERK1/2 induced by BDNF. These results suggest that the TH gene's transcription is positively regulated by BDNF, through the CRE and ERE of the promoter, but selectively antagonized by the Ca²⁺ signals evoked via NMDA-R without disturbing the ERK/MAP kinase pathway, the regulation by which may underlie the development of the catecholaminergic system in the brain.