Estrogen receptor-[beta] regulates human tryptophan hydroxylase-2 through an estrogen response element in the 5' untranslated region

In the dorsal raphe nucleus, 17[beta]-estradiol (E2) increases the expression of the brain-specific, rate-limiting enzyme for serotonin biosynthesis, tryptophan hydroxylase-2 (Tph2). Although estrogen receptor beta (ER[beta]) has been localized to Tph2 neurons, little is known about the transcriptional regulation of the Tph2 gene by estrogen. Since the ER[beta] agonist, diarylpropionitrile (DPN) also increases Tph2 expression, we tested the hypothesis that E2 regulates the Tph2 promoter through direct interactions with ER[beta]. A serotonergic cell line, B14, which endogenously expresses ER[beta] was transiently transfected with a fragment of the human TPH2 5'-untranslated region (5'-UTR) cloned into a luciferase reporter vector (TPH2-luc). Treatment with E2 or DPN caused a dose-dependent increase of TPH2-luc activity. In contrast, E2 conjugated to bovine serum albumin, which is cell membrane impermeable, had no effect on TPH2-luc activity. An estrogen receptor (ER) antagonist blocked E2 or DPN-induced TPH2-luc activity suggesting a classical ER mechanism. In silico analysis revealed an estrogen-response element (ERE) half-site located within the TPH2 5'-UTR. Deletion and site-directed mutation of this site abolished ligand-induced TPH2-luc activity. These results support the concept that there is a direct and functional interaction between E2:ER[beta] and the ERE half-site of the TPH2 promoter to regulate Tph2 expression. We illustrate a direct regulation of the TPH2 transcription by estradiol and ER[beta] via a newly identified ERE half-site within the TPH2 promoter: (i) Estradiol- or an ER[beta] agonist-induced TPH2 transcription was blocked by an ER antagonist, while (ii) membrane impermeable form of estradiol did not induce transcription. (iii) Deletion or mutation of the ERE half-site abolished ligand-induced TPH2 transcription. [PUBLICATION ABSTRACT]