ESTROGEN RECEPTOR BETA, A KEY FACTOR IN THE REGULATION OF PITUITARY CELL PROLIFERATION

SILVINA GUTIERREZ; JORGE H. MUKDSI; FLORENCIA PICECH; ALICIA I. TORRES; LILIANA DEL VALLE SOSA; JUAN P. PETITI; ANA L. DE PAUL; CAROLINA B. GUIDO; PABLO A. PÉREZ

Sao Paulo

Workshop; São Paulo School for Advanced Science in Cell Biology ? SPCELL; 2018

FAPESP, ASCB, EMBO

The pituitary gland is an endocrine organ whose proliferative activity varies in the different physiological states, being regulated by 17β-estradiol (E2) acting through estrogen receptors (ER) α and β. The ERα has been widely studied, while the implications of ERβ on the pituitary cell proliferation remain unknown. In this context, the aim of this work was to analyze the ERβ role and its regulation by E2, analyzing the participation of cyclin D1 and the tumor suppressors p21 and PTEN. To carry out this objective, female rats chronically treated with E2 and GH3 cells transfected with ERβ and stimulated with E2 or ER agonists were used. ERβ, Cyclin D1, PTEN and p21 expression and localization were determined by western blot and confocal microscopy. The cell cycle progression was analyzed by flow cytometry and the cellular proliferation was quantified by BrdU technique. Statistical analysis: ANOVA-Tukey.The results showed that in vivo, E2 treatment increased the gland?s size and weight while decreased the number of ERβ+ pituitary cells. In the other hand, the ovariectomy increased this ER subtype, suggesting that E2 inhibits the ERβ expression in this gland. We also observed that cells with different ERα/β index responded differentially to the proliferative stimulus of E2. The over-expression of ERβ in GH3 cells (GH3β+) inhibited the expression of ERα and cyclin D1, inducing cell cycle arrest and decreasing the mitogenic activity.Next we observed that the tumor suppressor PTEN was up-regulated in GH3β+ cells mainly in the nuclear compartment, where it is known to exert a stronger antiproliferative effect. In GH3β-, PTEN expression levels were lower and was found only near the plasma membrane.Finally, a relevant finding was the identification of a functional interaction between ERβ and p21, being the activation of ERβ able to induce nuclear translocation of p21, where it inhibits the cell cycle. Together, these results suggest that ERβ expression is inhibited by E2 and that this subtype inhibits cell proliferation by decreasing ERα and cyclin D1 expression, modulating p21 and PTEN levels and their subcellular localization as mechanisms involved in the adaptation of the proliferation to the hormonal requirements.