title: The residue I257 at S4-S5 linker in KCNQ1 determines KCNQ1/KCNE1 channel sensitivity to 1-alkanols.
abstract: OBJECTIVE
  KCNQ1 and KCNE1 form a complex in human ventricular cardiomyocytes, which are important in maintaining a normal heart rhythm. In the present study we investigated the effects of a homologous series of 1-alkanols on KCNQ1/KCNE1 channels expressed in Xenopus oocytes.
  
  
  METHODS
  ECG recording was made in rats injected with ethanol-containing solution (0.3 mL, ip). Human KCNQ1 channel and its auxiliary subunit KCNE1 were heterologously coexpressed in Xenopus oocytes, which were superfused with ND96 solution; 1-alkanols (ethanol, 1-butanol and 1-hexanol) were delivered through a gravity-driven perfusion device. The slow-delayed rectifier potassium currents IKs (KCNQ1/KCNE1 currents) were recorded using a two-electrode voltage clamp method. Site-directed mutations (I257A) were made in KCNQ1.
  
  
  RESULTS
  In ECG recordings, a low concentration of ethanol (3%, v/v) slightly increased the heart rate of rats, whereas the higher concentrations of ethanol (10%, 50%, v/v) markedly reduced it. In oocytes coexpressing KCNQ1/KCNE1 channels, ethanol, 1-butanol and 1-hexanol dose-dependently inhibited IKs currents with IC50 values of 80, 11 and 2.7 mmol/L, respectively. Furthermore, the 1-alkanols blocked the KCNQ1 channel in both open and closed states, and a four-state model could adequately explain the effects of 1-alkanols on the closed-state channel block. Moreover, the mutation of I257A at the intracellular loop between S4 and S5 in KCNQ1 greatly decreased the sensitivity to 1-alkanols; and the IC50 values of ethanol, 1-butanol and 1-hexanol were increased to 634, 414 and 7.4 mmol/L, respectively. The mutation also caused the ablation of closed-state channel block.
  
  
  CONCLUSIONS
  These findings provide new insight into the intricate mechanisms of the blocking effects of ethanol on the KCNQ1 channel.
authors.affiliation: College of Life Sciences, Wuhan University, Wuhan 430072, China.
authors.forename: Chang
authors.initials: C
authors.lastname: Xie
authors.affiliation: Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Hao-wen
authors.initials: HW
authors.lastname: Liu
authors.affiliation: Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Na
authors.initials: N
authors.lastname: Pan
authors.affiliation: Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Jiu-ping
authors.initials: JP
authors.lastname: Ding
authors.affiliation: College of Life Sciences, Wuhan University, Wuhan 430072, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Yao
mesh_terms: D020001:1-Butanol / Q000494:pharmacology*; D000818:Animals; D004562:Electrocardiography; D000431:Ethanol / Q000494:pharmacology*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D000441:Hexanols / Q000494:pharmacology*; D015640:Ion Channel Gating; D051657:KCNQ1 Potassium Channel / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008954:Models, Biological; D009154:Mutation; D009865:Oocytes / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D017208:Rats, Wistar; D013329:Structure-Activity Relationship; D014982:Xenopus laevis
chemical_list: D000441:Hexanols; C489622:KCNE1 protein, human; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; D024642:Potassium Channels, Voltage-Gated; D000431:Ethanol; C036260:1-hexanol; D020001:1-Butanol