Coactivators in Assay Design for Nuclear Hormone Receptor Drug Discovery

Abstract

Nuclear hormone receptors (NHRs) represent one of the most important drug targets in terms of therapeutic applications. The NHR superfamily consists of a family of DNA binding transcription factors whose function can be controlled by small molecules (steroids or organic acids). Therefore, NHRs are suitable protein targets for the therapies of human diseases. Some of the current marketed drugs, including several anticancer and antidiabetic drugs, are known to target NHRs. Examples include the anticancer and retinoid X receptor-targeting Targretin and the antidiabetic and peroxisome proliferative-activated receptor-gamma-targeting thiaozolidinediones. More NHR-targeting drugs are expected in the coming years. Identification of specific NHR modulators, as well as identification of ligands for orphan NHRs, will lead to new therapies for many human diseases. Many pharmaceutical companies are investing in NHR-targeted drugs, which are estimated to be 10-15% of the US dollars 400 billion global pharmaceutical market. This minireview discusses various aspects of NHR drug discovery, with a focus on the application of NHR coactivators in assay design for NHR ligand identification.

Current In Vitro High Throughput Screening Approaches to Assess Nuclear Receptor Activation

“…In typical ligand binding assays, such as the scintillation proximity assay (SPA) or fluorescent polarization (FP), compounds are screened for their ability to compete with a labeled reference ligand for LBD binding ( Table 1). Either an agonist or antagonist can be detected in this type of competitive binding assay [57]. SPA have evolved into powerful tools for HTS because of their ability to measure the binding capacity of very diverse classes of drug targets [58].…”

“…Agonist binding to the LBD induces the formation of an LBD-LxxLL complex. The presence of VP16 AD in this complex promotes the assembly of RNA polymerase II complexes (basal transcriptional machinery) at the promoter region (TATA box), and subsequently enhances transcription of the reporter gene [57].…”

A High-Content Glucocorticoid Receptor Translocation Assay for Compound Mechanism-of-Action Evaluation

“…Nuclear receptors (NRs) have been classified broadly by their ligands, the availability of ligand and coregulators (coactivators and corepressors), and the underlying protein-protein interactions and signaling events that control transcription. 3,4 Identification and characterization of therapeutic modulators have been the focus of NR-based drug discovery efforts. Various assay methodologies have been used to identify and study NR modulators either with the full-length receptor or the ligand binding domain (LBD) of the receptor, in a cell-free or cell-based format.…”

BAPJ69-4A: A yeast two-hybrid strain for both positive and negative genetic selection

“…Approximately 10-15% of the pharmaceutical drugs presently on the market are targeted toward nuclear receptors either as agonists or antagonists (Chen et al, 2003). Agonists are small molecule ligands that bind and activate the nuclear receptor, through inducing the conformational change necessary to activate the LBD.…”