New potential binding determinant for hERG channel inhibitors.

P Saxena,A Stary-Weinzinger,E Timin,A Hohaus,A Windisch,S Hering,E.-M Zangerl-Plessl,T Linder

doi:10.1038/srep24182

Abstract

Human ether-à-go-go related gene (hERG) 1 channels conduct the rapid delayed rectifier K+ current (IKr) and are essential for the repolarization of the cardiac action potential. hERG1 inhibition by structurally diverse drugs may lead to life threatening arrhythmia. Putative binding determinants of hERG1 channel blockers include T623, S624 and V625 on the pore helix, and residues G648, Y652 and F656, located on segment S6. We and others have previously hypothesized that additional binding determinants may be located on helix S5, which is in close contact with the S6 segments. In order to test this hypothesis, we performed a detailed investigation combining ionic current measurements with two-microelectrode voltage clamp and molecular modeling techniques. We identified a novel aromatic high affinity binding determinant for blockers located in helix S5, F557, which is equally potent as Y652. Modeling supports a direct interaction with the outer pore helix.

Highlights

The F557L mutant and the wild type Human ether-à-go-go related gene (hERG) (WT) channels were expressed in Xenopus laevis oocytes and potassium currents were measured with the two-microelectrode voltage clamp technique
This suggests that F557L on segment S5 is an strong molecular determinant of hERG inhibition as the well-established putative binding determinant Y652 (Fig. 2)
It is widely accepted that block of hERG K+ channels by structurally diverse molecules is mediated by two aromatic side chains Y652 and F65612

Summary

Introduction

The effects of F557L and Y652A on tail current inhibition by these drug concentrations are illustrated in Supplementary Fig. S1. F557L shifted the concentration response curves for all studied hERG blockers to the right, ranging from a 4 fold (amiodarone) to more than 50 fold (dofetilide) increase in IC50. To address whether residue F557 influences drug block via direct π -π and/or hydrophobic interactions, or if the experimentally observed effects are allosteric, we performed in silico modeling studies.

Results

Conclusion