Comprehensive Assessment Of Disease Mutant Forms Of The Human Kcnq1 Potassium Channel

The voltage-gated potassium channel KCNQ1 is critical for the cardiac action potential. Mutations in KCNQ1 and its accessory protein KCNE1 are the most common cause of congenital long-QT syndrome (LQTS). There are a variety of mechanisms by which a given mutation may cause KCNQ1 channel dysfunction and prolonged activation potentials. The ideal treatment of patients harboring a KCNQ1 mutation is dependent on which specific mechanisms cause loss of function. In the present study, we have employed a multidisciplinary approach to systematically investigate the specific effects of 51 KCNQ1 mutations on the channel structure, stability, trafficking, and (i.e. through collaboration) electrophysiological properties. The 51 mutations, located in the voltage sensor domain (VSD), are disease causing, benign, or of unknown significance. High quality NMR spectra of the isolated wild type VSD and of its mutant forms that are locked in fully activated state or in resting state serve as reference spectra. The 1H-15N TROSY spectrum of each mutant was collected and compared with the reference spectra to determine whether the mutation destabilizes the protein, or shifts the basal activated vs. resting state equilibrium. We have also expressed each mutant full length KCNQ1 in HEK293 cells and quantitatively assessed its total protein expression and cell surface expression using flow cytometry. These results will help elucidate the exact defects of each mutant associated with LQTS, potentially providing information that can be used to inform personalized treatment of LQTS subjects harboring KCNQ1 mutations.This work was supported by NIH Grant RO1 HL122010. We also thank the lab of Prof. Alfred George at Northwestern University for providing the cDNA for the KCNQ1-VSD mutants.