Activation function 2 (AF2) of estrogen receptor-α is required for the atheroprotective action of estradiol but not to accelerate endothelial healing

Abstract

17 beta-Estradiol (E2) regulates estrogen receptor-alpha (ER alpha) target gene transcription through the two independent activation functions (AFs), AF1 and AF2, located in the N-terminal and ligand binding domain of ER alpha, respectively. We previously reported that ER alpha is required for the E2 atheroprotective action as well as for its accelerative action on endothelial healing, but its AF1 function is dispensable. Here, we investigated the role of ER alpha AF2 in these two major beneficial actions of E2 by electively targeting ER alpha AF2 (named ER alpha AF2(0)). Our results prove four points. (i) Compared with WT ER alpha, the ability of ER alpha AF2(0) to stimulate the C3 complement or the estrogen response element-thymidine kinase promoter in two cell lines was dramatically decreased, confirming the importance of AF2 in the E2-induced transcriptional activity of ER alpha. (ii) The uterotrophic action of E2 was totally absent in ER alpha AF2(0) mice, showing the crucial role of ER alpha AF2 in E2-induced uterus hyperplasia. (iii) ER alpha AF2 was dispensable for the accelerative action of E2 on endothelial healing, underlining the functionality of ER alpha AF2(0) in vivo. (iv) Finally, the atheroprotective effect of E2 was abrogated in ER alpha AF2(0) LDL-r(-/-) mice. Thus, whereas ER alpha AF1 and ER alpha AF2 are both required for the uterotrophic action of E2, we show that only ER alpha AF2 is necessary for its atheroprotective effect.