Arginine site 264 in murine estrogen receptor-alpha is dispensable for the regulation of the skeleton

Mutation of arginine 264 in ER alpha has been shown to abrogate rapid membrane ER alpha-mediated endothelial effects. Our novel finding that mutation of R264 is dispensable for ER alpha-mediated skeletal effects supports the concept that R264 determines tissue specificity of ER alpha. Estrogen protects against bone loss but is not a suitable treatment due to adverse effects in other tissues. Therefore, increased knowledge regarding estrogen signaling in estrogen-responsive tissues is warranted to aid the development of bone-specific estrogen treatments. Estrogen receptor-alpha (ER alpha), the main mediator of estrogenic effects in bone, is widely subjected to posttranslational modifications (PTMs). In vitro studies have shown that methylation at site R260 in the human ER alpha affects receptor localization and intracellular signaling. The corresponding amino acid R264 in murine ER alpha has been shown to have a functional role in endothelium in vivo, although the methylation of R264 in the murine gene is yet to be empirically demonstrated. The aim of this study was to investigate whether R264 in ER alpha is involved in the regulation of the skeleton in vivo. Dual-energy X-ray absorptiometry (DEXA) analysis at 3, 6, 9, and 12 mo of age showed no differences in total body areal bone mineral density (BMD) between R264A and wild type (WT) in either female or male mice. Furthermore, analyses using computed tomography (CT) demonstrated that trabecular bone mass in tibia and vertebra and cortical thickness in tibia were similar between R264A and WT mice. In addition, R264A females displayed a normal estrogen treatment response in trabecular bone mass as well as in cortical thickness. Furthermore, uterus, thymus, and adipose tissue responded similarly in R264A and WT female mice after estrogen treatment. In conclusion, our novel finding that mutation of R264 in ER alpha does not affect the regulation of the skeleton, together with the known role of R264 for ER alpha-mediated endothelial effects, supports the concept that R264 determines tissue specificity of ER alpha. NEW & NOTEWORTHY Mutation of arginine 264 in ER alpha has been shown to abrogate rapid membrane ER alpha-mediated endothelial effects. Our novel finding that mutation of R264 is dispensable for ER alpha-mediated skeletal effects supports the concept that R264 determines tissue specificity of ER alpha.

Automated summary

Mutation of arginine 264 in ER alpha has been shown to abolish rapid membrane ER alpha-mediated endothelial effects. The novel finding that mutation of R264 is dispensable for ER alpha-mediated skeletal effects supports the concept that R264 determines the tissue specificity of ER alpha.