Mutation of Arginine 264 on ERα (Estrogen Receptor Alpha) Selectively Abrogates the Rapid Signaling of Estradiol in the Endothelium Without Altering Fertility.

Objective: ER alpha (estrogen receptor alpha) exerts nuclear genomic actions and also rapid membrane-initiated steroid signaling. The mutation of the cysteine 451 into alanine in vivo has recently revealed the key role of this ER alpha palmitoylation site on some vasculoprotective actions of 17 beta-estradiol (E2) and fertility. Here, we studied the in vivo role of the arginine 260 of ER alpha which has also been described to be involved in its E2-induced rapid signaling with PI-3K (phosphoinositide 3-kinase) as well as G protein in cultured cell lines. Approach and Results: We generated a mouse model harboring a point mutation of the murine counterpart of this arginine into alanine (R264A-ER alpha). In contrast to theC451A-ER alpha, theR264A-ER alpha females are fertile with standard hormonal serum levels and normal control of hypothalamus-pituitary ovarian axis. Although R264A-ER alpha protein abundance was normal, the well-described membrane ER alpha-dependent actions of estradiol, such as the rapid dilation of mesenteric arteries and the acceleration of endothelial repair of carotid, were abrogated inR264A-ER alpha mice. In striking contrast, E2-regulated gene expression was highly preserved in the uterus and the aorta, revealing intact nuclear/genomic actions in response to E2. Consistently, 2 recognized nuclear ER alpha-dependent actions of E2, namely atheroma prevention and flow-mediated arterial remodeling were totally preserved. Conclusions: These data underline the exquisite role of arginine 264 of ER alpha for endothelial membrane-initiated steroid signaling effects of E2 but not for nuclear/genomic actions. This provides the first model of fertile mouse with no overt endocrine abnormalities with specific loss-of-function of rapid ER alpha signaling in vascular functions.