Testis

17Beta-Estradiol Induces the Translocation of the Estrogen Receptors ESR1 and ESR2 to the Cell Membrane, MAPK3/1 Phosphorylation and Proliferation of Cultured Immature Rat Sertoli Cells

Abstract
The aim of the present study was to determine the mechanisms involved in estrogen actions in cultured rat Sertoli cells. RT-PCR detected transcripts for the estrogen receptors ESR1 and ESR2 in cultured immature Sertoli cells and in the testis of 15-, 28- and 120-day old rats. The expression of ESR1 and ESR2 was confirmed in Sertoli cells by immunofluorescence and Western blot. Immunohistochemistry with cryosections of testes from immature and adult rats revealed that ESR1 is present in Sertoli, Leydig and some peritubular myoid cells, and ESR2 is present in multiple cell types, including germ cells. Treatment of Sertoli cells with 17beta-estradiol (E2) induced a translocation of ESR1 and ESR2 to the plasma membrane and a concomitant phosphorylation of MAPK3/1. Both effects reached a maximum after 10 min and were blocked by PP2, an inhibitor of the SRC family of protein tyrosine kinases, and by the antiestrogen ICI 182,780 (ICI). MAPK3/1 phosphorylation was also decreased in the presence of AG 1478, an inhibitor of the epidermal growth factor receptor (EGFR) kinase, and in the presence of MAP2K1/2 inhibitor UO126. Treatment with E2 for 24 h increased the incorporation of [methyl-³H]thymidine, which was blocked by ICI. These results indicate that E2 activates a SRC-mediated translocation of ESRs to the plasma membrane, which results in the activation of EGFR and MAPK signaling pathway. In addition, activation of ESR1 and/or ESR2 by E2 is involved in proliferation of immature Sertoli cells. The estrogen actions in Sertoli cells might be a key step mediating cellular events important for spermatogenesis and fertility.

Key words: Mechanisms of Hormone Action • Estradiol • Estradiol receptor • Kinases • Sertoli cells