Strategies for the identification of allosteric modulators of G-protein-coupled receptors

Once considered a pharmacological curiosity, allosteric modulation of seven transmembrane domain G-protein-coupled receptors (GPCRs) has emerged as a potentially powerful means to affect receptor function for therapeutic purposes. Allosteric modulators, which interact with binding sites topologically distinct from the orthosteric ligand binding sites, can potentially provide improved selectivity and safety, along with maintenance of spatial and temporal aspects of GPCR signaling. Accordingly, drug discovery efforts for GPCRs have increasingly focused on the identification of allosteric modulators. This review is devoted to an examination of the strategies, challenges, and opportunities for high-throughput screening for allosteric modulators of GPCRs, with particular focus on the identification of positive allosteric modulators.