title: Co-expression of KCNE2 and KChIP2c modulates the electrophysiological properties of Kv4.2 current in COS-7 cells.
abstract: OBJECTIVE
  Several beta-subunits have been suggested to modulate the electrophysiological properties of the transient outward current (I(to)) in cardiac myocytes, including the obligatory beta-subunit K+-channel interacting protein (KChIP2) and KCNE2. However, neither KChIP2 nor KCNE2 modulation of Kv4.x (x=2 and/or 3) can fully recapitulate the electrophysiological properties of native I(to). The present study is to investigate how I(to) current is modulated when both KChIP2 and KCNE2 are coexpressed.
  
  
  METHODS
  Kv4.2, KChIP2c, and KCNE2 cDNA were simultaneously transfected into COS-7 cells at a molar ratio of 3:1:1. Whole-cell currents were recorded by the patch-clamp method.
  
  
  RESULTS
  In comparison with the current regulated by KChIP2c alone, the co-expression of KCNE2 further slowed Kv4.2 current inactivation kinetics, but diminished KChIP2c-induced positive shift of the voltage-dependent activation of Kv4.2 current. Importantly, co-expression of KCNE2 accelerated the current recovery from inactivation, and caused an povershootq of peak current amplitude during Kv4.2 current recovery, a phenomenon which has been uniquely described for human I(to). However, co-expression of KCNE2 exerted no further effect on Kv4.2 current amplitude, the rate of Kv4.2 current activation and voltage-dependent inactivation.
  
  
  CONCLUSIONS
  Co-expression of Kv4.2 with KChIP2c and KCNE2, but not with KChIP2c or KCNE2 alone, yields a current profile similar to native I(to). Both KChIP2c and KCNE2 simultaneously participate in recapitulation of the electrophysiological properties of I(to) in cardiac myocytes.
authors.affiliation: Department of Pathophysiology, Southern Medical University, Guangzhou 510515, China.
authors.forename: Wen-juan
authors.initials: WJ
authors.lastname: Liu
authors.forename: Hai-tang
authors.initials: HT
authors.lastname: Wang
authors.forename: Wei-wei
authors.initials: WW
authors.lastname: Chen
authors.forename: Jian-xin
authors.initials: JX
authors.lastname: Deng
authors.forename: Yong
authors.initials: Y
authors.lastname: Jiang
authors.forename: Jie
authors.initials: J
authors.lastname: Liu
mesh_terms: D000818:Animals; D019556:COS Cells; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D004594:Electrophysiology; D006801:Humans; D007700:Kinetics; D051605:Kv Channel-Interacting Proteins / Q000096:biosynthesis / Q000235:genetics*; D018408:Patch-Clamp Techniques; D024642:Potassium Channels, Voltage-Gated / Q000096:biosynthesis / Q000235:genetics*; D051672:Shal Potassium Channels / Q000502:physiology*
chemical_list: C489619:KCNE2 protein, human; C496752:KCNIP2 protein, human; D051605:Kv Channel-Interacting Proteins; D024642:Potassium Channels, Voltage-Gated; D051672:Shal Potassium Channels