title: Caveolin-3 suppresses late sodium current by inhibiting nNOS-dependent S-nitrosylation of SCN5A.
abstract: OBJECTIVE
  Mutations in CAV3-encoding caveolin-3 (Cav3) have been implicated in type 9 long QT syndrome (LQT9) and sudden infant death syndrome (SIDS). When co-expressed with SCN5A-encoded cardiac sodium channels these mutations increased late sodium current (INa) but the mechanism was unclear. The present study was designed to address the mechanism by which the LQT9-causing mutant Cav3-F97C affects the function of caveolar SCN5A.
  
  
  RESULTS
  HEK-293 cells expressing SCN5A and LQT9 mutation Cav3-F97C resulted in a 2-fold increase in late INa compared to Cav3-WT. This increase was reversed by the neural nitric oxide synthase (nNOS) inhibitor L-NMMA. Based on these findings, we hypothesized that an nNOS complex mediated the effect of Cav3 on SCN5A. A SCN5A macromolecular complex was established in HEK-293 cells by transiently expressing SCN5A, α1-syntrophin (SNTA1), nNOS, and Cav3. Compared with Cav3-WT, Cav3-F97C produced significantly larger peak INa amplitudes, and showed 3.3-fold increase in the late INa associated with increased S-nitrosylation of SCN5A. L-NMMA reversed both the Cav3-F97C induced increase in late and peak INa and decreased S-nitrosylation of SCN5A. Overexpression of Cav3-F97C in adult rat cardiomyocytes caused a significant increase in late INa compared to Cav3-WT, and prolonged the action potential duration (APD90) in a nNOS-dependent manner.
  
  
  CONCLUSIONS
  Cav3 is identified as an important negative regulator for cardiac late INa via nNOS dependent direct S-nitrosylation of SCN5A. This provides a molecular mechanism for how Cav3 mutations increase late INa to cause LQT9. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes".
authors.affiliation: Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI 53792, USA.
authors.forename: Jianding
authors.initials: J
authors.lastname: Cheng
authors.forename: Carmen R
authors.initials: CR
authors.lastname: Valdivia
authors.forename: Ravi
authors.initials: R
authors.lastname: Vaidyanathan
authors.forename: Ravi C
authors.initials: RC
authors.lastname: Balijepalli
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ackerman
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Makielski
mesh_terms: D000818:Animals; D051244:Caveolin 3 / Q000502:physiology*; D057809:HEK293 Cells; D006801:Humans; D008133:Long QT Syndrome / Q000235:genetics; D008564:Membrane Potentials; D020125:Mutation, Missense; D032383:Myocytes, Cardiac / Q000502:physiology; D062554:NAV1.5 Voltage-Gated Sodium Channel / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D051381:Rats; D026403:S-Nitrosothiols / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism
chemical_list: C417736:CAV3 protein, human; D051244:Caveolin 3; D062554:NAV1.5 Voltage-Gated Sodium Channel; D026403:S-Nitrosothiols; C568320:SCN5A protein, human; D009569:Nitric Oxide; D012964:Sodium; D052248:Nitric Oxide Synthase Type I
keywords: Caveolin-3; LQT9; Long QT syndrome; Nitric oxide synthase; Sodium current; Sudden infant death syndrome
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