Cysteine 723 in the C-linker segment confers oxidative inhibition of hERG1 potassium channels.
Excess reactive oxygen species (ROS) play a crucial role under pathophysiological conditions, such as ischaemia/reperfusion and diabetes, potentially contributing to cardiac arrhythmia. hERG1 (KCNH2) potassium channels terminate the cardiac action potential and malfunction can lead to long-QT syndrome and fatal arrhythmia. To investigate the molecular mechanisms of hERG1 channel alteration by ROS, hERG1 and mutants thereof were expressed in HEK293 cells and studied with the whole-cell patch-clamp method. Even mild ROS stress induced by hyperglycaemia markedly decreased channel current. Intracellular H2O2 or cysteine-specific modifiers also strongly inhibited channel activity and accelerated deactivation kinetics. Mutagenesis revealed that cysteine 723 (C723), a conserved residue in a structural element linking the C-terminal domain to the channel's gate, is critical for oxidative functional modification. Moreover, kinetics of channel closure strongly influences ROS-induced modification, where rapid channel deactivation diminishes ROS sensitivity. Because of its fast deactivation kinetics, the N-terminally truncated splice variant hERG1b possesses greater resistance to oxidative modification.
Kolbe
Katrin
K
Centre for Molecular Biomedicine, Department of Biophysics, Friedrich Schiller University of Jena, Hans-Knöll-Str. 2, D-07745 Jena, Germany.
Schönherr
Roland
R
Gessner
Guido
G
Sahoo
Nirakar
N
Hoshi
Toshinori
T
Heinemann
Stefan H
SH
D002460:Cell Line; D003545:Cysteine; D051638:Ether-A-Go-Go Potassium Channels / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D006801:Humans; D015640:Ion Channel Gating; D007700:Kinetics; D008564:Membrane Potentials; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D016877:Oxidants / Q000494:pharmacology; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000187:drug effects; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D017382:Reactive Oxygen Species / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D014162:Transfection
D051638:Ether-A-Go-Go Potassium Channels; C496884:KCNH1 protein, human; D016877:Oxidants; D026902:Potassium Channel Blockers; D017382:Reactive Oxygen Species; D011994:Recombinant Proteins; D013439:Sulfhydryl Reagents; D005947:Glucose; D003545:Cysteine