title: Re-trafficking of hERG reverses long QT syndrome 2 phenotype in human iPS-derived cardiomyocytes.
abstract: OBJECTIVE
  Long QT syndrome 2 (LQTS2) caused by missense mutations in hERG channel is clinically associated with abnormally prolonged ventricular repolarization and sudden cardiac deaths. Modelling monogenic arrhythmogenic diseases using human-induced pluripotent stem cells (hiPSCs) offers unprecedented mechanistic insights into disease pathogenesis. We utilized LQTS2-hiPSC-derived cardiomyocytes (CMs) to elucidate pathological changes and to demonstrate reversal of LQTS2 phenotype in a therapeutic intervention using a pharmacological agent, (N-[N-(N-acetyl-l-leucyl)-l-leucyl]-l-norleucine) (ALLN).
  
  
  RESULTS
  We generated LQTS2-specific CMs (A561V missense mutation in KCNH2) from iPSCs using the virus-free reprogramming method. These CMs recapitulate dysfunction of hERG potassium channel with diminished IKr currents, prolonged repolarization durations, and elevated arrhythmogenesis due to reduced membrane localization of glycosylated/mature hERG. Dysregulated expression of folding chaperones and processing proteasomes coupled with sequestered hERG in the endoplasmic reticulum confirmed trafficking-induced disease manifestation. Treatment with ALLN, not only increased membrane localization of mature hERG but also reduced repolarization, increased IKr currents and reduced arrhythmogenic events. Diverged from biophysical interference of hERG channel, our results show that modulation of chaperone proteins could be therapeutic in LQTS2 treatment.
  
  
  CONCLUSIONS
  Our in vitro study shows an alternative approach to rescue diseased LQTS2 phenotype via corrective re-trafficking therapy using a small chemical molecule, such as ALLN. This potentially novel approach may have ramifications in other clinically relevant trafficking disorders.
authors.affiliation: Research and Development Unit, National Heart Centre Singapore, Singapore National Heart Research Institute Singapore, Singapore ashish.mehta@nhcs.com.sg winston.shim.s.n@nhcs.com.sg.
authors.forename: Ashish
authors.initials: A
authors.lastname: Mehta
authors.affiliation: Research and Development Unit, National Heart Centre Singapore, Singapore.
authors.forename: Glen Lester
authors.initials: GL
authors.lastname: Sequiera
authors.affiliation: Research and Development Unit, National Heart Centre Singapore, Singapore.
authors.forename: Chrishan J A
authors.initials: CJ
authors.lastname: Ramachandra
authors.affiliation: Research and Development Unit, National Heart Centre Singapore, Singapore.
authors.forename: Yuliansa
authors.initials: Y
authors.lastname: Sudibyo
authors.affiliation: Research and Development Unit, National Heart Centre Singapore, Singapore.
authors.forename: Yingying
authors.initials: Y
authors.lastname: Chung
authors.affiliation: Research and Development Unit, National Heart Centre Singapore, Singapore.
authors.forename: Jingwei
authors.initials: J
authors.lastname: Sheng
authors.affiliation: Department of Paediatrics, KK Women's and Children Hospital, Singapore.
authors.forename: Keng Yean
authors.initials: KY
authors.lastname: Wong
authors.affiliation: Department of Paediatrics, KK Women's and Children Hospital, Singapore.
authors.forename: Teng Hong
authors.initials: TH
authors.lastname: Tan
authors.affiliation: Department of Cardiology, National Heart Centre Singapore, Singapore Cardiovascular and Metabolic Disorders Program, DUKE-NUS, Singapore.
authors.forename: Philip
authors.initials: P
authors.lastname: Wong
authors.affiliation: Department of Cardiology, National Heart Centre Singapore, Singapore Cardiovascular and Metabolic Disorders Program, DUKE-NUS, Singapore.
authors.forename: Reginald
authors.initials: R
authors.lastname: Liew
authors.affiliation: Research and Development Unit, National Heart Centre Singapore, Singapore National Heart Research Institute Singapore, Singapore Cardiovascular and Metabolic Disorders Program, DUKE-NUS, Singapore ashish.mehta@nhcs.com.sg winston.shim.s.n@nhcs.com.sg.
authors.forename: Winston
authors.initials: W
authors.lastname: Shim
mesh_terms: D000818:Animals; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels / Q000235:genetics / Q000502:physiology*; D006801:Humans; D057026:Induced Pluripotent Stem Cells / Q000166:cytology*; D007976:Leupeptins / Q000627:therapeutic use*; D008133:Long QT Syndrome / Q000188:drug therapy* / Q000503:physiopathology; D008297:Male; D051379:Mice; D009154:Mutation; D032383:Myocytes, Cardiac / Q000378:metabolism*; D010641:Phenotype; D021381:Protein Transport
chemical_list: D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; C000606915:Kcnh2 protein, mouse; D007976:Leupeptins; C063261:acetylleucyl-leucyl-norleucinal
keywords: Cardiomyocytes; Induced pluripotent stem cells; Ion channels; Long QT syndrome; Trafficking