Small molecule ligands for the orphan GPR27

Abstract

Background G protein-coupled receptors (GPCRs) are involved in many physiological processes and constitute the target of around 30% of marketed therapies. Nonetheless, ~100 human GPCRs have no known ligand and are designated as "orphan". This project focuses on GPR27, a rhodopsin-like alpha orphan of the SREB family (Super conserved Receptors Expressed in the Brain), presumably involved in the regulation of insulin secretion [1]. Methods In order to identify small molecules activating GPR27, we developed a firefly luciferase complementation assay (based on [2]) to assess the binding of ß-arrestin2 to the activated GPCR. To increase the affinity for and strengthen the interaction with ß-arrestin2, a GPR27-V2R chimera has been used for library screening. Results Small molecules activating GPR27-V2 have been identified in the DiverSetTM library (ChemBridge). After exclusion of non-specific activities using another unrelated GPCR, two compounds sharing a common scaffold with activity in the low micromolar range were selected for further investigations. We confirmed their agonist profile by performing complete concentration-response curves on our arrestin complementation assay as well as orthogonal assays. These compounds show good specificity being inactive on GPR85-V2 and GPR173-V2 (the two other SREB members). With these original tools, we characterized the recruitment of ß-arrestin2 to activated GPR27 WT. Conclusion We identified small molecule ligands for GPR27 that will serve as valuable tools for studying the pharmacology of GPR27 as well as its physiological roles, for example in insulin secretion. 1 Ku G.M., Pappalardo Z., Luo C.C., German M.S., McManus M.T. An siRNA Screen in Pancreatic Beta Cells Reveals a Role for Gpr27 in Insulin Production. PLoS genetics. 2012, 8, e1002449. 2 Takakura H., Hattori M., Takeuchi M., Ozawa T. Visualization and Quantitative Analysis of G Protein-Coupled Receptor−β-Arrestin Interaction in Single Cells and Specific Organs of Living Mice Using Split Luciferase Complementation. ACS Chem. Biol. 2012, 7, 901−910