title: Halide ion effects on human Ether-à-go-go related gene potassium channel properties.
abstract: The human Ether-à-go-go related gene (hERG) potassium channel has been widely used to counter screen potential pharmaceuticals as a biomarker to predict clinical QT prolongation. Thus, higher throughput assays of hERG are valuable for early in vitro screening of drug candidates to minimize failure in later-stage drug development due to this potentially adverse cardiac risk. We have developed a novel method utilizing potassium fluoride to improve throughput of hERG counter screening with an automated patch clamp system, PatchXpress 7000A. In that method, ∼50% substitution of internal Cl(-) with F(-) greatly increases success rate without substantially altering the biophysical properties of the hERG channel or compromising data quality. However, effect of F(-) or other halide ions on hERG channel properties has not been studied in detail. In this study, we examined effects of complete replacement of Cl(-) in internal solution with halide ions, F(-), or Br(-). We found that (1) F(-) slightly shifts the voltage dependence of hERG channel activation to more positive voltages, while Br(-) shifts it to more negative voltages; (2) Br(-) shifts to more positive voltages both the inactivation-voltage relationship and the peak position of channel full activation of hERG; (3) F(-) slows hERG activation, while both F(-) and Br(-) make the channel close faster; (4) neither F(-) nor Br(-) have any effect on hERG inactivation kinetics. In conclusion, compared to Cl(-), F(-) has subtle effect on hERG activation, while Br(-) has distinct effects on certain, but not all biophysical properties of hERG channel.
authors.affiliation: Safety Assessment and Laboratory Animal Resources, Merck Research Laboratories , West Point, Pennsylvania.
authors.forename: Haoyu
authors.initials: H
authors.lastname: Zeng
authors.forename: Bharathi
authors.initials: B
authors.lastname: Balasubramanian
authors.forename: Jacob R
authors.initials: JR
authors.lastname: Penniman
authors.forename: Fumi
authors.initials: F
authors.lastname: Kinose
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Salata
authors.forename: Armando
authors.initials: A
authors.lastname: Lagrutta
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D004353:Drug Evaluation, Preclinical / Q000379:methods; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels / Q000037:antagonists & inhibitors* / Q000502:physiology*; D005434:Flow Cytometry / Q000379:methods; D017022:Flow Injection Analysis / Q000379:methods; D006219:Halogens / Q000494:pharmacology*; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D007477:Ions; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques / Q000379:methods*; D026902:Potassium Channel Blockers / Q000494:pharmacology*
chemical_list: D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D006219:Halogens; D007477:Ions; C000606913:KCNH2 protein, human; D026902:Potassium Channel Blockers