A benzodiazepine activator locks K_v7.1 channels open by electro-mechanical uncoupling

Loss-of-function mutations in K_v7.1 often lead to long QT syndrome (LQTS), a cardiac repolarization disorder associated with arrhythmia and subsequent sudden cardiac death. The discovery of agonistic I_Ks modulators may offer a new potential strategy in pharmacological treatment of this disorder. The benzodiazepine derivative (R)-L3 potently activates K_v7.1 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 K_v7.1 and observed an uncoupling of the outer S4 segment with the inner S5, S6 and selectivity filter segments.