title: N-terminal arginines modulate plasma-membrane localization of Kv7.1/KCNE1 channel complexes.
abstract: OBJECTIVE
  The slow delayed rectifier current (I(Ks)) is important for cardiac action potential termination. The underlying channel is composed of Kv7.1 α-subunits and KCNE1 β-subunits. While most evidence suggests a role of KCNE1 transmembrane domain and C-terminus for the interaction, the N-terminal KCNE1 polymorphism 38G is associated with reduced I(Ks) and atrial fibrillation (a human arrhythmia). Structure-function relationship of the KCNE1 N-terminus for I(Ks) modulation is poorly understood and was subject of this study.
  
  
  METHODS
  We studied N-terminal KCNE1 constructs disrupting structurally important positively charged amino-acids (arginines) at positions 32, 33, 36 as well as KCNE1 constructs that modify position 38 including an N-terminal truncation mutation. Experimental procedures included molecular cloning, patch-clamp recording, protein biochemistry, real-time-PCR and confocal microscopy.
  
  
  RESULTS
  All KCNE1 constructs physically interacted with Kv7.1. I(Ks) resulting from co-expression of Kv7.1 with non-atrial fibrillation '38S' was greater than with any other construct. Ionic currents resulting from co-transfection of a KCNE1 mutant with arginine substitutions ('38G-3xA') were comparable to currents evoked from cells transfected with an N-terminally truncated KCNE1-construct ('Δ1-38'). Western-blots from plasma-membrane preparations and confocal images consistently showed a greater amount of Kv7.1 protein at the plasma-membrane in cells co-transfected with the non-atrial fibrillation KCNE1-38S than with any other construct.
  
  
  CONCLUSIONS
  The results of our study indicate that N-terminal arginines in positions 32, 33, 36 of KCNE1 are important for reconstitution of I(Ks). Furthermore, our results hint towards a role of these N-terminal amino-acids in membrane representation of the delayed rectifier channel complex.
authors.affiliation: Division of Cardiology, Section of Electrophysiology, JW Goethe-University, Frankfurt, Germany.
authors.forename: Zenawit
authors.initials: Z
authors.lastname: Girmatsion
authors.forename: Peter
authors.initials: P
authors.lastname: Biliczki
authors.forename: Ina
authors.initials: I
authors.lastname: Takac
authors.forename: Christin
authors.initials: C
authors.lastname: Schwerthelm
authors.forename: Stefan H
authors.initials: SH
authors.lastname: Hohnloser
authors.forename: Joachim R
authors.initials: JR
authors.lastname: Ehrlich
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001120:Arginine / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006801:Humans; D051657:KCNQ1 Potassium Channel / Q000737:chemistry / Q000378:metabolism*; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
chemical_list: D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; D012333:RNA, Messenger; D001120:Arginine
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