Development of a GPR23 cell-based β-lactamase reporter assay

GPR23 is a G protein-coupled receptor (GPCR) proposed to play a vital role in neurodevelopment processes such as neurogenesis and neuronal migration. To date, no small molecule GPR23 agonists or antagonists have been reported, except for the natural ligand, lysophosphatic acid, and its analogs. Identification of ligands selective for GPR23 would provide valuable tools for studying the pharmacology, physiological function, and pathophysiological implications of this receptor. This report describes how a tetracycline-inducible system was utilized in conjunction with a sensitive β-lactamase reporter gene to develop an assay in which constitutive activity of the receptor could be monitored. This assay was then utilized to screen a 1.1 million compound library to identify the first small molecule inverse agonists for the receptor. We believe that these compounds will be invaluable tools in the further study of GPR23. In addition, we believe that the assay development techniques utilized in this report are broadly applicable to other receptors exhibiting constitutive activity.