A Computational-Based Approach to Identify Estrogen Receptor α/β Heterodimer Selective Ligands

The biologic effects of estrogens are transduced by two estrogen receptors (ERs), ER α and ER β , which function in dimer forms. The ER α / α homodimer promotes and the ER β / β inhibits estrogen-dependent growth of mammary epithelial cells; the functions of ER α / β heterodimers remain elusive. Using compounds that promote ER α / β heterodimerization, we have previously shown that ER α / β heterodimers appeared to inhibit tumor cell growth and migration in vitro. Further dissection of ER α / β heterodimer functions was hampered by the lack of ER α / β heterodimer-specific ligands. Herein, we report a multistep workflow to identify the selective ER α / β heterodimer-inducing compound. Phytoestrogenic compounds were first screened for ER transcriptional activity using reporter assays and ER dimerization preference using a bioluminescence resonance energy transfer assay. The top hits were subjected to in silico modeling to identify the pharmacophore that confers ER α / β heterodimer specificity. The pharmacophore encompassing seven features that are potentially important for the formation of the ER α / β heterodimer was retrieved and subsequently used for virtual screening of large chemical libraries. Four chemical compounds were identified that selectively induce ER α / β heterodimers over their respective homodimers. Such ligands will become unique tools to reveal the functional insights of ER α / β heterodimers.