title: Functional consequences of methionine oxidation of hERG potassium channels.
abstract: Reactive species oxidatively modify numerous proteins including ion channels. Oxidative sensitivity of ion channels is often conferred by amino acids containing sulfur atoms, such as cysteine and methionine. Functional consequences of oxidative modification of methionine in human ether à go-go related gene 1 (hERG1), which encodes cardiac I(Kr) channels, are unknown. Here we used chloramine-T (ChT), which preferentially oxidizes methionine, to examine the functional consequences of methionine oxidation of hERG channels stably expressed in a human embryonic kidney cell line (HEK 293) and native hERG channels in a human neuroblastoma cell line (SH-SY5Y). ChT (300 microM) significantly decreased whole-cell hERG current in both HEK 293 and SH-SY5Y cells. In HEK 293 cells, the effects of ChT on hERG current were time- and concentration-dependent, and were markedly attenuated in the presence of enzyme methionine sulfoxide reductase A that specifically repairs oxidized methionine. After treatment with ChT, the channel deactivation upon repolarization to -60 or -100 mV was significantly accelerated. The effect of ChT on channel activation kinetics was voltage-dependent; activation slowed during depolarization to +30 mV but accelerated during depolarization to 0 or -10mV. In contrast, the reversal potential, inactivation kinetics, and voltage-dependence of steady-state inactivation remained unaltered. Our results demonstrate that the redox status of methionine is an important modulator of hERG channel.
authors.affiliation: Department of Integrative Pharmacology, Abbott Laboratories, 100 Abbott Park Road, Abbott Park, IL 60064, USA. zhi.su@abbott.com
authors.forename: Zhi
authors.initials: Z
authors.lastname: Su
authors.forename: James
authors.initials: J
authors.lastname: Limberis
authors.forename: Ruth L
authors.initials: RL
authors.lastname: Martin
authors.forename: Rong
authors.initials: R
authors.lastname: Xu
authors.forename: Katrin
authors.initials: K
authors.lastname: Kolbe
authors.forename: Stefan H
authors.initials: SH
authors.lastname: Heinemann
authors.forename: Toshinori
authors.initials: T
authors.lastname: Hoshi
authors.forename: Bryan F
authors.initials: BF
authors.lastname: Cox
authors.forename: Gary A
authors.initials: GA
authors.lastname: Gintant
mesh_terms: D000200:Action Potentials; D002460:Cell Line; D002700:Chloramines / Q000494:pharmacology; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels / Q000378:metabolism*; D006801:Humans; D008715:Methionine / Q000378:metabolism* / Q000494:pharmacology*; D010084:Oxidation-Reduction / Q000187:drug effects; D011188:Potassium / Q000378:metabolism; D014105:Tosyl Compounds / Q000494:pharmacology
chemical_list: D002700:Chloramines; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; D014105:Tosyl Compounds; C016300:chloramine-T; D008715:Methionine; D011188:Potassium