Referenced in: none

Automatically associated channels: Kv7.1 , Slo1

Title: Instability of KCNE1-D85N that causes long QT syndrome: stabilization by verapamil.

Authors: Shinji Sakata, Yasutaka Kurata, Peili Li, Tomomi Notsu, Kumi Morikawa, Junichiro Miake, Katsumi Higaki, Yasutaka Yamamoto, Akio Yoshida, Yasuaki Shirayoshi, Kazuhiro Yamamoto, Minoru Horie, Haruaki Ninomiya, Susumu Kanzaki, Ichiro Hisatome

Journal, date & volume: Pacing Clin Electrophysiol, 2014 Jul , 37, 853-63

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/24499369

Abstract
A KCNE1 polymorphism, D85N, causes long QT syndrome (LQTS) with a decrease in the slowly activating delayed-rectifier K(+) channel current (IKs ). We examined impacts of D85N polymorphism on KCNE1 protein stability and functions, and tested the ability of various drugs to modify them.KCNE1-D85N or the wild-type protein was coexpressed in COS7 cells with KCNQ1 to form K(+) channels. Expression, degradation, and intracellular localization of KCNE1 proteins, as well as the currents conferred by KCNQ1/KCNE1 complexes, were determined using immunoblots, immunofluorescence, and patch-clamp techniques.The protein level of KCNE1-D85N was lower than that of the wild-type, in spite of the comparable levels of their mRNA. KCNE1-D85N was highly ubiquitinated and rapidly degraded as compared to the wild-type; a proteasome inhibitor, MG132, inhibited its degradation and increased its steady-state level. Both KCNE1-D85N and the wild-type proteins were co-immunoprecipitated with KCNQ1. Immunofluorescent signals of KCNE1-D85N accumulated in the endoplasmic reticulum and Golgi apparatus, with reduced levels on the cell membrane. Patch-clamp experiments demonstrated that the membrane current corresponding to IKs was much smaller in cells expressing KCNE1-D85N than in those expressing the wild-type. Verapamil (0.5-10 μM) increased the protein level of KCNE1-D85N, decreased its ubiquitination, slowed its degradation, and enhanced KCNQ1/KCNE1-D85N channel currents. Pretreatment with amiodarone abolished these effects of verapamil.KCNE1-D85N is less stable than the wild-type protein, and is rapidly degraded through the ubiquitin-proteasome system. Verapamil may be of a therapeutic value in LQTS patients via preventing degradation of KCNE1-D85N.