A benzodiazepine activator locks Kv7.1 channels open by electro-mechanical uncoupling.

Schreiber JA; Möller M; Zaydman M; Zhao L; Beller Z; Becker S; Ritter N; Hou P; Shi J; Silva J; Wrobel E; Strutz-Seebohm N; Decher N; Schmitt N; Meuth SG; Düfer M; Wünsch B; Cui J; Seebohm G

Abstract

Loss-of-function mutations in Kv7.1 often lead to long QT syndrome (LQTS), a cardiac repolarization disorder associated with arrhythmia and subsequent sudden cardiac death. The discovery of agonistic IKs modulators may offer a new potential strategy in pharmacological treatment of this disorder. The benzodiazepine derivative (R)-L3 potently activates Kv7.1 channels and shortens action potential duration, thus may represent a starting point for drug development. However, the molecular mechanisms underlying modulation by (R)-L3 are still unknown. By combining alanine scanning mutagenesis, non-canonical amino acid incorporation, voltage-clamp electrophysiology and fluorometry, and in silico protein modelling, we show that (R)-L3 not only stimulates currents by allosteric modulation of the pore domain but also alters the kinetics independently from the pore domain effects. We identify novel (R)-L3-interacting key residues in the lower S4-segment of Kv7.1 and observed an uncoupling of the outer S4 segment with the inner S5, S6 and selectivity filter segments.