Transcriptional activity of estrogen receptors ERα and ERβ in the EtC.1 cerebellar granule cell line

Estrogen receptors alpha and beta (ERα and ERβ) are expressed in the cerebellum throughout development and in the adult suggesting an important role of 17-β-estradiol (E2) in this brain structure. In the present study, we have characterized the functionality of estrogen receptors (ERs) expressed in the immature cerebellar granule cell line EtC.1 by transfecting such cells with a luciferase reporter gene (ERE-Luc) coupled to an estrogen response element promoter. The induction of luciferase activity in EtC.1 cells by E2 and ER-subtype selective agonists was compared in normal cells and in cells overexpressing human ERα or ERβ (hERα or hERβ). E2-mediated transcription of the reporter gene was blocked by the ER antagonist ICI 182,780 (ICI), demonstrating the presence of functional native ERs. The selective agonist for ERα (PPT) showed a reduced response in luciferase induction compared to E2. Moreover, the ERβ agonist (DPN) was unable to induce luciferase activity. E2-induced ERE-Luc transcription was not increased by overexpression of hERα. In contrast, hERβ overexpression reduced the efficacy of E2 and abolished ERα-selective agonist activity. The ERβ-specific agonist did not induce gene reporter activity unless hERβ was overexpressed in the cells, suggesting that the endogenous ERβ in EtC.1 cells is transcriptionally inactive. ICI inhibition of E2 responses was not affected by overexpression of the human ERs. The data suggest that ERα plays a predominant role in E2-mediated transcription in EtC.1 cells. Our data are discussed in view of other reports alluding to the complexity and cell-type specificity of E2-mediated transcription.