HOXA10 regulates endometrial GABAA receptor expression and membrane translocation

Sadeghi H, Taylor HS. HOXA10 regulates endometrial GABAA receptor expression and membrane translocation. Am J Physiol Endocrinol Metab 298: E889 –E893, 2010. First published January 26, 2010; doi:10.1152/ajpendo.00577.2009.—Expression of the GABAA receptor has been described previously in the human endometrium in both luminal epithelium and stroma. Its expression is increased during decidualization in rodents and in the implantation window of human endometrium. Here we localized GABA subunit receptor protein in human endometrium and identified regulators of gene expression and activation. GABAA was localized to the cell surface, and expression increased during the window of embryo implantation in human endometrium. The well-differentiated human endometrial adenocarcinoma cell line Ishikawa was treated with progesterone and transfected with pcDNA-HOXA10, HOXA10 siRNA, or respective controls. GABAA receptor mRNA expression was evaluated by real-time RT-PCR. Protein expression and localization were evaluated using immunofluorescence. GABAA receptor mRNA expression was increased significantly after either progesterone treatment or HOXA10 transfection. Coadministration of progesterone along with HOXA10 transfection had no additional effect on the expression of GABAA receptor mRNA over either agent alone. Blocking HOXA10 expression with siRNA prevented progesteroneinduced GABAA receptor mRNA expression. Additionally, either HOXA10 or progesterone independently caused increased translocation of the GABA receptor from the cytoplasm to the cell membrane. Translocation in response to progesterone was blocked with HOXA10 siRNA. Progesterone-induced GABAA subunit receptor expression is likely mediated indirectly through progesterone’s regulation of HOXA10 expression. Modification of subtype composition and translocation of the GABA receptor ion channel likely modulate endometrial receptivity. Whereas HOXA10 typically enhances the expression of progesterone-responsive genes, here HOXA10 expression leads to production of a less progestin-responsive GABA receptor subtype, likely buffering the effects of luteal phase progesterone on GABA receptor activity.