NOS1AP polymorphisms reduce NOS1 activity and interact with prolonged repolarization in arrhythmogenesis

C. Ronchi, J. Bernardi, M. Mura, M. Stefanello, B. Badone, M. Rocchetti, L. Crotti, P. Brink, P.J. Schwartz, M. Gnecchi*, A. Zaza*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


Aims NOS1AP single-nucleotide polymorphisms (SNPs) correlate with QT prolongation and cardiac sudden death in patients affected by long QT syndrome type 1 (LQT1). NOS1AP targets NOS1 to intracellular effectors. We hypothesize that NOS1AP SNPs cause NOS1 dysfunction and this may converge with prolonged action-potential du-ration (APD) to facilitate arrhythmias. Here we test (i) the effects of NOS1 inhibition and their interaction with prolonged APD in a guinea pig cardiomyocyte (GP-CMs) LQT1 model; (ii) whether pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from LQT1 patients differing for NOS IAP variants and mutation penetrance display a phenotype compatible with NOS1 deficiency.Methods and results In GP-CMs, NOS1 was inhibited by S-Methyl-L-thiocitrulline acetate (SMTC) or Vinyl-L-NIO hydrochloride (L-VNIO); LQT1 was mimicked by I-Ks blockade (JNJ303) and beta-adrenergic stimulation (isoproterenol). hiPSC-CMs were obtained from symptomatic (S) and asymptomatic (AS) KCNQ1-A341V carriers, harbouring the minor and major alleles of NOS IAP SNPs (rs16847548 and rs4657139), respectively. In GP-CMs, NOS1 inhibition prolonged APD, enhanced I-CaL and I-NaL, stowed Ca2+ decay, and induced delayed afterdepolarizations. Under action-potential damp, switching to shorter APD suppressed 'transient inward current' events induced by NOS1 inhibition and re-duced cytosolic Ca2+. In S (vs. AS) hiPSC-CMs, APD was longer and I-CaL larger; NOS1AP and NOS1 expression and co-localization were decreased.Conclusion The minor NOS1AP alleles are associated with NOS1 loss of function. The latter likely contributes to APD prolon-gation in LQT1 and converges with it to perturb Ca2+ handling. This establishes a mechanistic link between NOS IAP SNPs and aggravation of the arrhythmia phenotype in prolonged repolarization syndromes.[GRAPHICS].
Original languageEnglish
Pages (from-to)472-483
Number of pages12
JournalCardiovascular Research
Issue number2
Publication statusPublished - 1 Feb 2021


  • arrhythmias
  • hipsc-derived cardiomyocytes
  • lqt1
  • nos1 defect
  • nos1ap polymorphism
  • LQT1
  • hiPSC-derived cardiomyocytes
  • NOS1AP polymorphism
  • Arrhythmias
  • NOS1 defect


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