HERG channel (dys)function revealed by dynamic action potential clamp technique.
The human ether-a-go-go-related gene (HERG) encodes the rapid component of the cardiac delayed rectifier potassium current (I(Kr)). Per-Arnt-Sim domain mutations of the HERG channel are linked to type 2 long-QT syndrome. We studied wild-type and/or type 2 long-QT syndrome-associated mutant (R56Q) HERG current (I(HERG)) in HEK-293 cells, at both 23 and 36 degrees C. Conventional voltage-clamp analysis revealed mutation-induced changes in channel kinetics. To assess functional implication(s) of the mutation, we introduce the dynamic action potential clamp technique. In this study, we effectively replace the native I(Kr) of a ventricular cell (either a human model cell or an isolated rabbit myocyte) with I(HERG) generated in a HEK-293 cell that is voltage-clamped by the free-running action potential of the ventricular cell. Action potential characteristics of the ventricular cells were effectively reproduced with wild-type I(HERG), whereas the R56Q mutation caused a frequency-dependent increase of the action potential duration in accordance with the clinical phenotype. The dynamic action potential clamp approach also revealed a frequency-dependent transient wild-type I(HERG) component, which is absent with R56Q channels. This novel electrophysiological technique allows rapid and unambiguous determination of the effects of an ion channel mutation on the ventricular action potential and can serve as a new tool for investigating cardiac channelopathies.
Experimental and Molecular Cardiology Group and the Department of Physiology, Academic Medical Center, University of Amsterdam, The Netherlands. g.berecki@amc.uva.nl
Géza
G
Berecki
Jan G
JG
Zegers
Arie O
AO
Verkerk
Zahurul A
ZA
Bhuiyan
Berend
B
de Jonge
Marieke W
MW
Veldkamp
Ronald
R
Wilders
Antoni C G
AC
van Ginneken
D000200:Action Potentials; D000818:Animals; D001703:Biophysics / Q000379:methods; D002460:Cell Line; D000072237:ERG1 Potassium Channel; D004594:Electrophysiology; D004699:Endocardium / Q000378:metabolism; D051638:Ether-A-Go-Go Potassium Channels; D006801:Humans; D007473:Ion Channels / Q000737:chemistry; D007477:Ions; D007700:Kinetics; D008133:Long QT Syndrome / Q000378:metabolism; D008564:Membrane Potentials; D008954:Models, Biological; D032342:Muscle Cells / Q000378:metabolism; D009154:Mutation; D032383:Myocytes, Cardiac / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010496:Pericardium / Q000378:metabolism; D010641:Phenotype; D024642:Potassium Channels, Voltage-Gated / Q000737:chemistry* / Q000502:physiology*; D011817:Rabbits; D013696:Temperature; D013997:Time Factors
D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D007473:Ion Channels; D007477:Ions; C000606913:KCNH2 protein, human; D024642:Potassium Channels, Voltage-Gated