Mechanism of slow hERG1 channel deactivation induced by RPR260243.

Abstract

The opening and closing of voltage-dependent potassium channels is dependent on a tight coupling between movement of the voltage sensing S4 segments and the activation gate. A specific interaction between intracellular amino- and carboxyl-termini is required for the characteristically slow rate of hERG1 channel deactivation. Compounds that activate hERG1 channel function represent a novel approach for prevention of arrhythmia associated with prolonged ventricular repolarization. RPR260243 (RPR), a quinoline oxo-propyl piperidine derivative activates hERG1 by dramatically slowing the rate of channel closure, a gating process called deactivation. Here we report that similar to wild-type channels, RPR greatly slows the deactivation rate of channels missing their amino-termini, or of split channels lacking a covalent link between the voltage sensor domain and the pore domain. By contrast, RPR did not slow deactivation of C-terminal truncated hERG1 channels. D540K hERG1 mutant channels are closed at −80 mV, but can be activated by pulsing to more depolarized or hyperpolarized potentials. RPR slowed the deactivation of channels that were activated by depolarization, but not by hyperpolarization. Together, these findings indicate that RPR does not slow deactivation by stabilizing an interaction involving the amino-terminus, does not require a covalent link between the voltage sensor and pore domains, but can favorably bind at the intracellular site of S5 and S6, thereby possibly delaying closure of the helix bundle crossing gate. Furthermore, we gain insights into RPRs binding mode by comparing WT and D540K modeling results.