Discovery and characterization of G protein-gated, inwardly-rectifying, potassium channel modulators

Abstract

G protein-gated, inwardly-rectifying, potassium (K+) (GIRK) channels are important regulators of cellular excitability throughout the body. GIRK channels are composed of four subunits and exist as homomeric and heteromeric channels. Although the vast majority of neuronally-expressed GIRK channels contain GIRK1, GIRK2, and GIRK3 subunits, a discrete population of dopaminergic neurons in the ventral tegmental area do not express GIRK1. Selectively targeting GIRK channels with subunit-selective pharmacological probes may improve our understanding of the role of GIRK channels in reward and addiction circuitry. In an effort to discover activators of GIRK2 channels, we conducted a 100,000-compound high-throughput screen and discovered that VU0529331 activated GIRK2 channels. We learned that VU0529331 increased currents through GIRK1/2 and GIRK2 channels in a concentration-dependent manner without altering K+ selectivity or inward rectification. We established that VU0529331 activity was independent of Gi/o protein-coupled receptor signaling and discovered that VU0529331 also activated homomeric GIRK4, Kir6.1/SUR2a, and Kir6.1/SUR2b channels. VU0529331 is the first reported synthetic small molecule known to activate heteromeric and homomeric GIRK channels. Going forward, this molecule establishes a foundation on which more efficacious and potent analogs can be generated. Together with known GIRK modulators, VU0529331 will enable the investigation of specific GIRK channel roles throughout physiology and disease.