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

Abstract

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 E tC.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 E tC.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 E tC.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 E tC.1 cells. Our data are discussed in view of other reports alluding to the complexity and cell-type specificity of E2-mediated transcription.