I. The development of estrogen receptor coactivator binding inhibitors. II. Investigations into the binding modes of ligands selective for estrogen receptor alpha

Based on our analysis of a recent X-ray crystal structure of the ERα ligand binding domain complexed to a helical peptide containing a single nuclear receptor box motif, we have designed a series of small molecules to inhibit the binding of p160 coactivator proteins to the ER. This is a novel approach to blocking ER action because we are attempting to interrupt the pathway at a point subsequent to hormone binding.; A variety of compounds based on aromatic cores including triazene, pyrimidine, and naphthalene have been synthesized. Two in vitro assays utilizing fluorescence polarization and fluorescence resonance energy transfer have been developed to test the compounds for ER binding and inhibition of coactivator recruitment. The most promising class of CBIs proved to be compounds with a pyrimidine core, which displaced a coactivator peptide from the ER with K_i's equal to approximately 30 μM. This work provides the first examples of non-peptide coactivator binding inhibitors that we are aware of.; There are two genes for the estrogen receptor, the classical ERα and the more recently discovered ERβ. Though the receptors share significant sequence identity, they have a different tissue distribution, ligand specificity, and possibly biological roles. The development of modulators selective for one subtype over the other could help in understanding the physiological significance of the two receptors.; Our laboratory has previously discovered that certain heterocycles show high binding affinity and selectivity for ERα. In order to design more potent and selective derivatives, a better understanding of how they bind to the receptor is needed. Using a comparative binding analysis method and molecular modeling, we were able to assess the binding mode of a furan agonist and antagonist. As an agonist, the furan binds to the receptor with the C(2) phenol acting as the A-ring in most cases. As an antagonist, the furan binds with the C(5) phenol acting as the A-ring mimic and the basic side chain extending back into the pocket in a similar fashion to known antagonists. The preparation of various mono and bisphenolic furan analogs in conjunction with molecular modeling assisted in confirming these assertions.