0053: The estrogen receptor alpha C451 palmitoylation site is absolutely required for vascular membrane-initiated action of estrogens in mice

Abstract

Estrogen Receptor alpha (ERα) activation functions AF-1 and AF-2 classically mediate gene transcription in response to estradiol (E2). A fraction of ERα is targeted to plasma membrane and elicits membrane-initiated steroid signalling (MISS), but the physiological roles of MISS in vivo are poorly understood. We therefore generated a mouse with a point mutation of the palmitoylation site of ERα (C451A-ERα) to obtain membrane-specific loss-of-function of ERα. The abrogation of membrane localization of ERα in vivo was confirmed in primary hepatocytes, and it resulted in female infertility with abnormal ovaries lacking corpora lutea and increase in luteinizing hormone levels. In contrast, E2 action in the uterus was preserved in C451A-ERα mice and endometrial epithelial proliferation was similar to wild-type. However, E2 vascular actions such as rapid dilatation, the acceleration of endothelial repair and endothelial NO synthase phosphorylation were abrogated in C451A-ERα mice. A complementary mutant mouse lacking the transactivation function AF-2 of ER (ERα-AF2°) provided selective loss-of-function of nuclear ERα actions. In ERα-AF2°, the acceleration of endothelial repair in response to estrogen-dendrimer conjugate, which is a membrane-selective ER ligand, was unaltered, demonstrating integrity of MISS actions. In genome-wide analysis of uterine gene expression, the vast majority of E2-dependent gene regulation was abrogated in ERα-AF2° whereas in C451A-ERα it was nearly fully preserved, indicating that membrane-to-nuclear receptor crosstalk in vivo is modest in the uterus. Thus, this work is the first to genetically segregate membrane versus nuclear actions of a steroid hormone receptor and to demonstrate their in vivo tissue-specific roles.