title: Structural basis for ether-a-go-go-related gene K+ channel subtype-dependent activation by niflumic acid.
abstract: Niflumic acid [2-((3-(trifluoromethyl)phenyl)amino)-3-pyridinecarboxylic acid, NFA] is a nonsteroidal anti-inflammatory drug that also blocks or modulates the gating of a wide spectrum of ion channels. Here we investigated the mechanism of channel activation by NFA on ether-a-go-go-related gene (ERG) K(+) channel subtypes expressed in Xenopus laevis oocytes using two-electrode voltage-clamp techniques. NFA acted from the extracellular side of the membrane to differentially enhance ERG channel currents independent of channel state. At 1 mM, NFA shifted the half-point for activation by -6, -18, and -11 mV for ERG1, ERG2, and ERG3 channels, respectively. The half-point for channel inactivation was shifted by +5 to +9 mV by NFA. The structural basis for the ERG subtype-specific response to NFA was explored with chimeric channels and site-directed mutagenesis. The molecular determinants of enhanced sensitivity of ERG2 channels to NFA were isolated to an Arg and a Thr triplet in the extracellular S3-S4 linker.
authors.affiliation: Nora Eccles Harrison Cardiovascular Research and Training Institute, Department of Physiology, University of Utah, 95 South 2000 East, Salt Lake City, UT 84112, USA.
authors.forename: David
authors.initials: D
authors.lastname: Fernandez
authors.forename: John
authors.initials: J
authors.lastname: Sargent
authors.forename: Frank B
authors.initials: FB
authors.lastname: Sachse
authors.forename: Michael C
authors.initials: MC
authors.lastname: Sanguinetti
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003198:Computer Simulation; D004305:Dose-Response Relationship, Drug; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels / Q000737:chemistry* / Q000378:metabolism*; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects*; D008969:Molecular Sequence Data; D009544:Niflumic Acid / Q000494:pharmacology*; D009865:Oocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D013997:Time Factors; D014982:Xenopus laevis
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; D024642:Potassium Channels, Voltage-Gated; D011993:Recombinant Fusion Proteins; D009544:Niflumic Acid