Genetic screening in C. elegans identifies rho-GTPase activating protein 6 as novel HERG regulator

• Published in: Journal of molecular and cellular cardiology Vol. 46; no. 2; pp. 257 - 267
• Main Authors: Potet, Franck, Petersen, Christina I, Boutaud, Olivier, Shuai, Wen, Stepanovic, Svetlana Z, Balser, Jeffrey R, Kupershmidt, Sabina
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-02-2009
• Subjects: Animals; Arrhythmia; Arrhythmias, Cardiac - genetics; Arrhythmias, Cardiac - metabolism; Caenorhabditis elegans - genetics; Caenorhabditis elegans - metabolism; Caenorhabditis elegans Proteins - genetics; Caenorhabditis elegans Proteins - metabolism; Cardiovascular; Electrophysiology; ERG1 Potassium Channel; Ether-A-Go-Go Potassium Channels - genetics; Ether-A-Go-Go Potassium Channels - metabolism; GTPase-Activating Proteins - genetics; GTPase-Activating Proteins - metabolism; HERG; Humans; Ion channel; Long QT Syndrome; Long QT Syndrome - genetics; Long QT Syndrome - metabolism; Potassium - metabolism; Potassium Channels - genetics; Potassium Channels - metabolism; Potassium current; Protein trafficking; rho GAP; RNA Interference; HERG; Arrhythmia; rho GAP; Long QT Syndrome; Potassium current; Ion channel; Protein trafficking
• ISSN: 0022-2828; 1095-8584
• DOI: 10.1016/j.yjmcc.2008.10.015

Abstract The human ether-a-go-go related gene (HERG) constitutes the pore forming subunit of IKr , a K+ current involved in repolarization of the cardiac action potential. While mutations in HERG predispose patients to cardiac arrhythmias (Long QT syndrome; LQTS), altered function of HERG regulators are undoubtedly LQTS risk factors. We have combined RNA interference with behavioral screening in Caenorhabditis elegans to detect genes that influence function of the HERG homolog, UNC-103. One such gene encodes the worm ortholog of the rho-GTPase activating protein 6 (ARHGAP6). In addition to its GAP function, ARHGAP6 induces cytoskeletal rearrangements and activates phospholipase C (PLC). Here we show that IKr recorded in cells co-expressing HERG and ARHGAP6 was decreased by 43% compared to HERG alone. Biochemical measurements of cell-surface associated HERG revealed that ARHGAP6 reduced membrane expression of HERG by 35%, which correlates well with the reduction in current. In an atrial myocyte cell line, suppression of endogenous ARHGAP6 by virally transduced shRNA led to a 53% enhancement of IKr . ARHGAP6 effects were maintained when we introduced a dominant negative rho-GTPase, or ARHGAP6 devoid of rhoGAP function, indicating ARHGAP6 regulation of HERG is independent of rho activation. However, ARHGAP6 lost effectiveness when PLC was inhibited. We further determined that ARHGAP6 effects are mediated by a consensus SH3 binding domain within the C-terminus of HERG, although stable ARHGAP6–HERG complexes were not observed. These data link a rhoGAP-activated PLC pathway to HERG membrane expression and implicate this family of proteins as candidate genes in disorders involving HERG.