17β-Estradiol induces Akt-1 through estrogen receptor-β in the frog (Rana esculenta) male germ cells

Abstract

Several lines of evidence support the key role of estrogens in male fertility. Here, we investigate the regulation of the serine/threonine kinase Akt-1 in the frog (Rana esculenta) testis during the annual sexual cycle and, whether 17beta-estradiol (E2) exerts a role in the Akt-1 activity. Akt-1 has been shown to be the mediator of growth factor-dependent cell proliferation, survival, and metabolism in a variety of cell types. First, we demonstrate by immunohistochemistry, the presence of estrogen receptor-beta (ERbeta), and Akt-1 in the spermatogonia (SPG), spermatocytes (SPC), and spermatids (SPT). Western-blot analysis revealed that ERbeta isoform (molecular weight 55 kDa) was highly expressed in May (reproductive period) with respect to January and November (winter stasis); in parallel, Akt-1 (molecular weight 60 kDa) is highly phosphorylated (Ser-473) during the period of active spermatogenesis (May) compared with the winter stasis (January and November). In addition, in vitro experiments demonstrate that E2 treatment induces the activation of Akt-1, and this effect is counteracted by the anti-estrogen ICI 182-780. In conclusion, our data show that E2 induces Akt-1 phosphorylation (Ser-473) possibly via ERbeta in frog (R. esculenta) male germ cells.