title: A mutation causing Brugada syndrome identifies a mechanism for altered autonomic and oxidant regulation of cardiac sodium currents.
abstract: BACKGROUND
  The mechanisms of the electrocardiographic changes and arrhythmias in Brugada syndrome (BrS) remain controversial. Mutations in the sodium channel gene, SCN5A, and regulatory proteins that reduce or eliminate sodium current (INa) have been linked to BrS. We studied the properties of a BrS-associated SCN5A mutation in a protein kinase A (PKA) consensus phosphorylation site, R526H.
  
  
  RESULTS
  In vitro PKA phosphorylation was detected in the I-II linker peptide of wild-type (WT) channels but not R526H or S528A (phosphorylation site) mutants. Cell surface expression of R526H and S528A channels was reduced compared with WT. Whole-cell INa through all channel variants revealed no significant differences in the steady-state activation, inactivation, and recovery from inactivation. Peak current densities of the mutants were significantly reduced compared with WT. Infection of 2D cultures of neonatal rat ventricular myocytes with WT and mutant channels increased conduction velocity compared with noninfected cells. PKA stimulation significantly increased peak INa and conduction velocity of WT but not mutant channels. Oxidant stress inhibits cardiac INa; WT and mutant INa decreases with the intracellular application of reduced nicotinamide adenine dinucleotide (NADH), an effect that is reversed by PKA stimulation in WT but not in R526H or S528A channels.
  
  
  CONCLUSIONS
  We identified a family with BrS and an SCN5A mutation in a PKA consensus phosphorylation site. The BrS mutation R526H is associated with a reduction in the basal level of INa and a failure of PKA stimulation to augment the current that may contribute to the predisposition to arrhythmias in patients with BrS, independent of the precipitants.
authors.affiliation: From the Division of Cardiology, Department of Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, MD (T.A., F.F., D.E., S.B., G.F.T.); and Department of Biomedical Engineering (G.K., L.T.) and Department of Biological Chemistry (G.G.H.), Johns Hopkins University, Baltimore, MD.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Aiba
authors.affiliation: From the Division of Cardiology, Department of Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, MD (T.A., F.F., D.E., S.B., G.F.T.); and Department of Biomedical Engineering (G.K., L.T.) and Department of Biological Chemistry (G.G.H.), Johns Hopkins University, Baltimore, MD.
authors.forename: Federica
authors.initials: F
authors.lastname: Farinelli
authors.affiliation: From the Division of Cardiology, Department of Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, MD (T.A., F.F., D.E., S.B., G.F.T.); and Department of Biomedical Engineering (G.K., L.T.) and Department of Biological Chemistry (G.G.H.), Johns Hopkins University, Baltimore, MD.
authors.forename: Geran
authors.initials: G
authors.lastname: Kostecki
authors.affiliation: From the Division of Cardiology, Department of Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, MD (T.A., F.F., D.E., S.B., G.F.T.); and Department of Biomedical Engineering (G.K., L.T.) and Department of Biological Chemistry (G.G.H.), Johns Hopkins University, Baltimore, MD.
authors.forename: Geoffrey G
authors.initials: GG
authors.lastname: Hesketh
authors.affiliation: From the Division of Cardiology, Department of Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, MD (T.A., F.F., D.E., S.B., G.F.T.); and Department of Biomedical Engineering (G.K., L.T.) and Department of Biological Chemistry (G.G.H.), Johns Hopkins University, Baltimore, MD.
authors.forename: David
authors.initials: D
authors.lastname: Edwards
authors.affiliation: From the Division of Cardiology, Department of Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, MD (T.A., F.F., D.E., S.B., G.F.T.); and Department of Biomedical Engineering (G.K., L.T.) and Department of Biological Chemistry (G.G.H.), Johns Hopkins University, Baltimore, MD.
authors.forename: Subrata
authors.initials: S
authors.lastname: Biswas
authors.affiliation: From the Division of Cardiology, Department of Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, MD (T.A., F.F., D.E., S.B., G.F.T.); and Department of Biomedical Engineering (G.K., L.T.) and Department of Biological Chemistry (G.G.H.), Johns Hopkins University, Baltimore, MD.
authors.forename: Leslie
authors.initials: L
authors.lastname: Tung
authors.affiliation: From the Division of Cardiology, Department of Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, MD (T.A., F.F., D.E., S.B., G.F.T.); and Department of Biomedical Engineering (G.K., L.T.) and Department of Biological Chemistry (G.G.H.), Johns Hopkins University, Baltimore, MD. gtomasel@jhmi.edu.
authors.forename: Gordon F
authors.initials: GF
authors.lastname: Tomaselli
mesh_terms: D000328:Adult; D000818:Animals; D053840:Brugada Syndrome / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism* / Q000503:physiopathology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004562:Electrocardiography; D006321:Heart / Q000503:physiopathology; D006801:Humans; D008297:Male; D032342:Muscle Cells / Q000378:metabolism; D020125:Mutation, Missense; D062554:NAV1.5 Voltage-Gated Sodium Channel / Q000235:genetics* / Q000378:metabolism; D016877:Oxidants / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*
chemical_list: D062554:NAV1.5 Voltage-Gated Sodium Channel; D016877:Oxidants; D017382:Reactive Oxygen Species; C568320:SCN5A protein, human; D012964:Sodium; D017868:Cyclic AMP-Dependent Protein Kinases
keywords: death, sudden, cardiac; ion channel; mutation; reactive oxygen species