Label-Free Profiling of Ligands for Endogenous Gpcrs Using a Cell-Based High-Throughput Screening Technology

This article reports the use of Corning Epic system—a label-free and noninvasive optical system that is centered on resonant waveguide grating biosensors—to profile endogenous G protein-coupled receptors (GPCRs) in living cells under physiologically relevant conditions. The endogenous GPCRs examined were bradykinin B 2 receptor in A431 cells and protease-activated receptor subtype 1 (PAR 1 ) in Chinese hamster ovary (CHO) cells. The activation of either receptor led to G q -mediated signaling in the respective cells, as confirmed by Fluo-3 assays. Stimulation of CHO cells with thrombin, a PAR 1 natural agonist, resulted in an optical response relating to dynamic mass redistribution that is similar to that induced by bradykinin in A431 cells. Based on the kinetics of agonist-mediated optical signatures, two time points, one before and another 5 min after the stimulation, were chosen to develop high-throughput (HT) screening assays. Results showed that such endpoint measurements enable not only HT screening of compounds using endogenous GPCRs, but also determining the efficacies of agonists. Those results suggested that the Corning Epic label-free system is an easily scaleable biosensor, amenable as an HTS platform for GPCR drug discovery and deorphanization.