Abstract
The estrogen-related receptor alpha (ERR alpha) was one of the first orphan receptors identified through a search for genes encoding proteins related to the steroid nuclear receptor, Estrogen Receptor alpha (ER alpha). The physiological role of ERR alpha has not yet been established nor has a natural ligand been elucidated. Importantly, research indicates that ERR alpha may be a novel drug target to treat breast cancer and/or metabolic disorders. A homogeneous time-resolved fluorescence (HTRF) assay has been developed to screen for ERR alpha-specific antagonists. This assay uses the ERR ligand binding domain and the coactivator interaction domain of Proliferator-activated Receptor gamma Coactivator-1 alpha (PGC-1 alpha) to examine the ability of compounds to antagonize the constitutive interaction between ERR alpha and the coactivator. A dissociation-enhanced lanthanide fluorescence immunoassay (DELFIA) was also created to counter screen compounds identified in the HTRF screen. Here we report the discovery of high-affinity ERR alpha subtype selective antagonists. Additionally, a homology model of ERRa in an antagonist conformation has been developed and after subsequent docking studies, we offer a model showing the molecular determinants that suggest why our novel tri-cyclic antagonist, N-[(2Z)-3-(4,5-dihydro-1,3-thiazol-2-yl)-1,3-thiazolidin-2-yl idene]-5 H dibenzo[a,d] [7]annulen-5-amine, binds to ERR alpha with high affinity but does not bind to either ERR beta or ERR gamma. Drug Dev Res 69:203-218, 2008. (C) 2008 Wiley-Liss, Inc.