SCN5A encodes the alpha subunit of the human voltage-dependent Na channel (hNaV1.5) found in heart. We have made the novel observation that up to four very common variants of NaV1.5 exist in human heart and at least some have functional implications. Mutations in this channel also cause sudden cardiac death in the congenitally acquired long QT syndrome (LQT3) and the Brugada Syndrome (BS). We have recently characterized four novel SCN5A mutations and found: 1) Two in Sudden Infant Death Syndrome (A997S, R1826H) are LQT3.2) LQT3 (M1766L) and BS (G1743) mutations have expression defects """"""""rescued"""""""" by antiarrhythmic drugs. 3) M1766L has normal or absent current depending on the variant NaV1.5 background used to test it. We propose to investigate further the extent and mechanisms of expression defects and their """"""""rescue"""""""" and the importance of """"""""background"""""""". Through collaboration with Dr. Ackerman at Mayo Clinic we also have >20 additional novel SCN5A mutations to investigate for novel functional defects and arrhythrnia mechanism. We will make and express these channels in cell culture, define function by voltage clamp and immunocytochemistry, and correlate molecular function with clinical phenotype through arrhythmia mechanism.
In Aim 1 we will investigate the expression and function of wild type variants, and also how mutant channel expression and function depends upon the background clone.
In Aim 2 we will study novel mutants.
In Aim 3 we will investigate mutants with """"""""gain of function"""""""" and test the hypothesis that late current decay in LQT3 correlates with enhanced rate dependent QT interval adaptation, later onset, and better prognosis than mutations without late current decay.
In Aim 4 we will investigate mutations with """"""""loss of function"""""""", the mechanism for loss of function including novel trafficking defects, and test the hypothesis that this loss can be """"""""rescued"""""""" by drugs.
In Aim 5 we will co-express mutations with the beta1 and beta3 subunit, and assess effects of PKA stimulation, to test the hypothesis that these areas are critical to the mechanism of action. These studies on the novel findings will have implications for arrhythmia mechanism and genotype-phenotype correlation in both mutation arrhythmia syndromes and more generally for the variants in """"""""normal' hearts that may generate insight into genetic predisposition to acquired arrhythmia. At a more basic level these """"""""natural"""""""" experiments will contribute to understanding the structure-function relationship of this important channel.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
1R01HL071092-01A1
Application #
6612188
Study Section
Special Emphasis Panel (ZRG1-CCVS (01))
Program Officer
Wang, Lan-Hsiang
Project Start
2003-09-15
Project End
2007-08-31
Budget Start
2003-09-15
Budget End
2004-08-31
Support Year
1
Fiscal Year
2003
Total Cost
$363,750
Indirect Cost
Name
University of Wisconsin Madison
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
161202122
City
Madison
State
WI
Country
United States
Zip Code
53715
Makielski, Jonathan C (2016) Late sodium current: A mechanism for angina, heart failure, and arrhythmia. Trends Cardiovasc Med 26:115-22
Hu, Rou-Mu; Tan, Bi-Hua; Tester, David J et al. (2015) Arrhythmogenic Biophysical Phenotype for SCN5A Mutation S1787N Depends upon Splice Variant Background and Intracellular Acidosis. PLoS One 10:e0124921
Yang, Kai-Chien; Kyle, John W; Makielski, Jonathan C et al. (2015) Mechanisms of sudden cardiac death: oxidants and metabolism. Circ Res 116:1937-55
Kyle, John W; Makielski, Jonathan C (2014) Diseases caused by mutations in Nav1.5 interacting proteins. Card Electrophysiol Clin 6:797-809
Adsit, Graham S; Vaidyanathan, Ravi; Galler, Carla M et al. (2013) Channelopathies from mutations in the cardiac sodium channel protein complex. J Mol Cell Cardiol 61:34-43
Cheng, Jianding; Valdivia, Carmen R; Vaidyanathan, Ravi et al. (2013) Caveolin-3 suppresses late sodium current by inhibiting nNOS-dependent S-nitrosylation of SCN5A. J Mol Cell Cardiol 61:102-10
Hu, Rou-Mu; Tan, Bi-Hua; Orland, Kate M et al. (2013) Digenic inheritance novel mutations in SCN5a and SNTA1 increase late I(Na) contributing to LQT syndrome. Am J Physiol Heart Circ Physiol 304:H994-H1001
Cheng, Jianding; Norstrand, David W Van; Medeiros-Domingo, Argelia et al. (2011) LQTS-associated mutation A257G in *1-syntrophin interacts with the intragenic variant P74L to modify its biophysical phenotype. Cardiogenetics 1:
Cheng, Jianding; Tester, David J; Tan, Bi-Hua et al. (2011) The common African American polymorphism SCN5A-S1103Y interacts with mutation SCN5A-R680H to increase late Na current. Physiol Genomics 43:461-6
Cheng, Jianding; Makielski, Jonathan C; Yuan, Ping et al. (2011) Sudden unexplained nocturnal death syndrome in Southern China: an epidemiological survey and SCN5A gene screening. Am J Forensic Med Pathol 32:359-63

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