title: Modulation of KCNQ1 alternative splicing regulates cardiac IKs and action potential repolarization.
abstract: BACKGROUND
  Slow delayed-rectifier potassium current (IKs) channels, made of the pore-forming KCNQ1 and auxiliary KCNE1 subunits, play a key role in determining action potential duration (APD) in cardiac myocytes. The consequences of drug-induced KCNQ1 splice alteration remain unknown.
  
  
  OBJECTIVE
  To study the modulation of KCNQ1 alternative splicing by amiloride and the consequent changes in IKs and action potentials (APs) in ventricular myocytes.
  
  
  METHODS
  Canine endocardial, midmyocardial, and epicardial ventricular myocytes were isolated. Levels of KCNQ1a and KCNQ1b as well as a series of splicing factors were quantified by using the reverse transcriptase-polymerase chain reaction and Western blot. The effect of amiloride-induced changes in the KCNQ1b/total KCNQ1 ratio on AP was measured by using whole-cell patch clamp with and without isoproterenol.
  
  
  RESULTS
  With 50 μmol/L of amiloride for 6 hours, KCNQ1a at transcriptional and translational levels increased in midmyocardial myocytes but decreased in endo- and epicardial myocytes. Likewise, changes in splicing factors in midmyocardial were opposite to that in endo- and epicardial myocytes. In midmyocardial myocytes amiloride shortened APD and decreased isoproterenol-induced early afterdepolarizations significantly. The same amiloride-induced effects were demonstrated by using human ventricular myocyte model for AP simulations under beta-adrenergic stimulation. Moreover, amiloride reduced the transmural dispersion of repolarization in pseudo-electrocardiogram.
  
  
  CONCLUSIONS
  Amiloride regulates IKs and APs with transmural differences and reduces arrhythmogenicity through the modulation of KCNQ1 splicing. We suggested that the modulation of KCNQ1 splicing may help prevent arrhythmia.
authors.affiliation: Department of Biomedical Engineering, Cardiac Bioelectricity and Arrhythmia Center, Washington University in St. Louis, St Louis, Missouri 63130-4899, USA.
authors.forename: Hsiang-Chun
authors.initials: HC
authors.lastname: Lee
authors.forename: Yoram
authors.initials: Y
authors.lastname: Rudy
authors.forename: Phd
authors.initials: P
authors.lastname: Po-Yuan
authors.forename: Sheng-Hsiung
authors.initials: SH
authors.lastname: Sheu
authors.forename: Jan-Gowth
authors.initials: JG
authors.lastname: Chang
authors.forename: Jianmin
authors.initials: J
authors.lastname: Cui
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D017398:Alternative Splicing / Q000235:genetics*; D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D015153:Blotting, Western; D051668:Delayed Rectifier Potassium Channels / Q000235:genetics* / Q000378:metabolism; D004232:Diuretics / Q000494:pharmacology*; D004285:Dogs; D006352:Heart Ventricles; D007545:Isoproterenol / Q000494:pharmacology; D051657:KCNQ1 Potassium Channel / Q000235:genetics* / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D051668:Delayed Rectifier Potassium Channels; D004232:Diuretics; D051657:KCNQ1 Potassium Channel; D000584:Amiloride; D007545:Isoproterenol
keywords: AP; APD; Action potential; Alternative splicing; Amiloride; CL; EAD; ECG; Endo; Epi; I(CaL); I(Ks); ISO; KCNQ1; L-type calcium current; Mid; ORd; O’Hara-Rudy; PKA; RT-PCR; TDR; action potential; action potential duration; cycle length; early afterdepolarization; electrocardiogram; endocardial; epicardial; isoproterenol; midmyocardial; protein kinase A; reverse transcriptase-polymerase chain reaction; slow delayed-rectifier potassium current; transmural dispersion of repolarization