EAG Domains Regulate LQT Mutant hERG Channels in Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Abstract

The generation of human induced pluripotent stem (hiPS) cells provides a novel path for a wide range of disease research, including LQTS. The human ether-a-go-go related gene (hERG) encodes the α-subunit of a voltage-gated potassium channel underlying IKr. hERG potassium channels contain nearly 300 different disease-causing mutations, which can lead to long QT syndrome (LQTS). Its N-terminal region contains an eag domain, which is important for modulating channel deactivation properties. R56Q is a point mutation located in the PAS domain that is associated with LQTS, a defect known to increase the rate of deactivation profoundly. Previous work showed that R56Q profoundly increased the rate of deactivation and lessend steady-state inactivation in Xenopus oocytes and mammalian HEK293 cells. We also showed that a soluble eag domain could restore the aberrant deactivation kinetics and inactivation properties of hERG R56Q. Here, we tested whether the delivery of adenoviral eag domains could rescue hERG R56Q channels expressed in cardiomyocytes derived from human iPSCs (hiPSC-CMs). We used whole-cell patch-clamp recordings to measure currents from iPSC-CMs expressing hERG, hERG R56Q and hERG R56Q+eag domains. We found that the adenoviral delivery of hERG R56Q to iPSC-CM resulted in channels with a faster rate of deactivation compared to that of WT hERG, indicating that hERG R56Q retained its aberrant gating in cardiomyocytes. We found that adenoviral delivery of eag domains restored slow deactivation kinetics to hERG R56Q channels in iPSC-CMs. The results indicated that adenoviral-delivery of a small polypeptide (i.e. eag domain) could restore the current deficiencies in a hERG LQT-mutant channel. This result indicates that eag domain polypeptides may be a biological therapeutic for LQTS.