Estradiol regulates alternative splicing of estrogen receptor-α mRNA in differentiated NG108-15 neuronal cells

Abstract

The biological actions of estrogen are mostly conveyed through interaction with two different types of estrogen receptor (ER), ER-α and ER-β. With regard to ER-α, an alternatively spliced form and its translated product, truncated estrogen receptor product-1 (TERP-1), have been identified in the rat pituitary. TERP-1 has the ability to inhibit the ER binding to DNA response element by forming hetero-dimers with the wild-type ER. Furthermore, TERP-1 expression increased concurrently with serum estrogen levels. Although estrogen also plays important roles in the central nervous system, the existence and regulatory mechanism of alternatively spliced ER-α mRNA expression has remained unclear. The present study evaluated the expression of the alternatively spliced form of the ER-α gene, and examined the influence of a representative ER ligand, 17β-estradiol (E 2), on the expression in differentiated NG108-15 neuronal cells. A real-time RT-PCR analysis using primer sets designed to amplify from exons 3 to 4, exons 4 to 5, exons 5 to 6, exons 6 to 7, and exons 7 to 8 of the mouse ER-α gene revealed the existence of alternatively spliced ER-α mRNA and its putative transcription initiation site, located between exon 4 and exon 5. Although E 2 had no apparent effect on the overall expression of ER-α mRNA, it reduced the incidence of the alternatively spliced form of ER-α. The down-regulation by E 2 predominantly arose via binding to nuclear ERs. The present study demonstrated that alternatively spliced ER-α mRNA is expressed in differentiated NG108-15 neuronal cells, and provides evidence for the functional up-regulation of ER-α via the ligand-binding activation of ERs.