A distinct three-helix centipede toxin SSD609 inhibits I(ks) channels by interacting with the KCNE1 auxiliary subunit.

Yiming Li,Chenyang Wang,Changlin Tian,Fangming Wu,Xingwang Yang,Longhua Zhang,Yun Zhang,Peibei Sun,Shufang He,Ming Wen

doi:10.1038/srep13399

Abstract

KCNE1 is a single-span transmembrane auxiliary protein that modulates the voltage-gated potassium channel KCNQ1. The KCNQ1/KCNE1 complex in cardiomyocytes exhibited slow activated potassium (Iks) currents. Recently, a novel 47-residue polypeptide toxin SSD609 was purified from Scolopendra subspinipes dehaani venom and showed Iks current inhibition. Here, chemically synthesized SSD609 was shown to exert Iks inhibition in extracted guinea pig cardiomyocytes and KCNQ1/KCNE1 current attenuation in CHO cells. The K+ current attenuation of SSD609 showed decent selectivity among different auxiliary subunits. Solution nuclear magnetic resonance analysis of SSD609 revealed a distinctive three-helix conformation that was stabilized by a new disulfide bonding pattern as well as segregated surface charge distribution. Structure-activity studies demonstrated that negatively charged Glu19 in the amphipathic extracellular helix of KCNE1 was the key residue that interacted with SSD609. The distinctive three-helix centipede toxin SSD609 is known to be the first polypeptide toxin acting on channel auxiliary subunit KCNE1, which suggests a new type of pharmacological regulation for ion channels in cardiomyocytes.

Highlights

Potassium channel KCNQ1 by slowing its activation and enhancing the channel conductance to generate Iks currents[9]
The results will allow for detailed structure–activity relationship studies of SSD609, which could serve as the basis for the development of potential molecular probes or drugs for probing the pathophysiological function of the KCNQ1/KCNE1 channel and related diseases, such as arrhythmia and type II diabetes
Because the Iks current in cardiac myocytes predominantly originates from the KCNQ1/KCNE1 channel, a patch-clamp analysis of the KCNQ1/KCNE1 channels expressed in Chinese hamster ovary (CHO) cells was performed to verify the efficacy of the chemically synthesized SSD609

Summary

Introduction

Potassium channel KCNQ1 by slowing its activation and enhancing the channel conductance to generate Iks currents[9]. Venomic and transcriptomic analyses of the centipede Scolopendra subspinipes dehaani (SSD) were conducted, and many polypeptide toxins were identified with preliminary functional annotations[11]. Primary sequencing of the purified peptide determined that SSD609 consists of 47 amino acids, and preliminary functional assays conducted with the purified peptide indicated that it targets K+ channels, but no detailed analysis has been conducted. The successful synthesis of the peptide greatly facilitated the subsequent illustration of the detailed channel regulation functions of SSD609 and its potential target proteins. The results will allow for detailed structure–activity relationship studies of SSD609, which could serve as the basis for the development of potential molecular probes or drugs for probing the pathophysiological function of the KCNQ1/KCNE1 channel and related diseases, such as arrhythmia and type II diabetes

Methods

Results

Conclusion