Characterization of MC4R regulation of the Kir7.1 channel using the Tl+ flux assay

Abstract

The family of inward rectifying potassium channels (Kir channels) plays crucial roles in the regulation of heart rhythms, renal excretion, insulin release, and neuronal activity. Their dysfunction has been attributed to numerous diseases such as cardiac arrhythmia, kidney failure and electrolyte imbalance, diabetes mellitus, epilepsy, retinal degeneration, and other neuronal disorders. We have recently demonstrated that the melanocortin-4 receptor (MC4R), a Gαs-coupled GPCR, regulates Kir7.1 activity through a mechanism independent of Gαs and cAMP. In contrast to the many other members of the Kir channel family, less is known about the biophysical properties, regulation, and physiological functions of Kir7.1. In addition to using conventional patch clamp techniques, we have employed a high-throughput Tl+ flux assay to further investigate the kinetics of MC4R-Kir7.1 signaling in vitro. Here, we discuss the employment of the Tl+ flux assay to study MC4R -mediated regulation of Kir7.1 activity and to screen compounds for drug discovery.