2022- Genetically-encoded BRET probes shed light on ligand bias–induced variable ion selectivity in TRPV1 and P2X5/7
SyncroPatch 384PE (a predecessor model of the SyncroPatch 384 instrument) Publication in PNAS (2022)
Chappe Y., Pierredon S., Joushomme A., Molle P., Garenne A., Canovi A., Barbeau S., Poulletier De Gannes F., Hurtier A., Lagroye I., Ducret T., Quignard J., Compan V., Percherancier Y.
PNAS (2022) doi:10.1073/pnas.2205207119
Whether ion channels experience ligand-dependent dynamic ion selectivity remains of critical importance since this could support ion channel functional bias. Tracking selective ion permeability through ion channels, however, remains challenging even with patch-clamp electrophysiology. In this study, we have developed highly sensitive bioluminescence resonance energy transfer (BRET) probes providing dynamic measurements of Ca2+ and K+ concentrations and ionic strength in the nanoenvironment of Transient Receptor Potential Vanilloid-1 Channel (TRPV1) and P2X channel pores in real time and in live cells during drug challenges. Our results indicate that AMG517, BCTC, and AMG21629, three well-known TRPV1 inhibitors, more potently inhibit the capsaicin (CAPS)-induced Ca2+ influx than the CAPS-induced K+ efflux through TRPV1. Even more strikingly, we found that AMG517, when injected alone, is a partial agonist of the K+ efflux through TRPV1 and triggers TRPV1-dependent cell membrane hyperpolarization. In a further effort to exemplify ligand bias in other families of cationic channels, using the same BRET-based strategy, we also detected concentration- and time-dependent ligand biases in P2X7 and P2X5 cationic selectivity when activated by benzoyl-adenosine triphosphate (Bz-ATP). These custom-engineered BRET-based probes now open up avenues for adding value to ion-channel drug discovery platforms by taking ligand bias into account.