Cardiac arrhythmias cause more than 400,000 sudden deaths each year in the U.S. Mutations in the cardiac sodium channel gene SCN5A cause several inherited arrhythmias, including Brugada syndrome (BrS) and sick sinus syndrome (SSS). SCN5A encodes the cardiac sodium channel Nav1.5, which produces the cardiac sodium current (INa) responsible for generation and propagation of the cardiac action potential. BrS and SSS mutations in SCN5A act by a loss of function mechanism (i.e. loss or reduction of INa). Reduction of INa is associated with defective trafficking of Nav1.5 to the plasma membrane. However, the molecular mechanisms underlying trafficking of Nav1.5 to the plasma membrane are mostly unknown. To identify critical molecular determinants required for Nav1.5 trafficking, we performed a yeast two-hybrid screen and identified a small protein MOG1 that interacts directly with Nav1.5 and can facilitate trafficking of Nav1.5 to the plasma membrane and increase INa. One dominant negative mutation of MOG1 (E83D) was reported in BrS and also causes a trafficking defect of Nav1.5 and reduced INa. We have found that MOG1 is required for ER export of Nav1.5 during trafficking. Computer-based protein structural modeling followed by protein-protein interaction studies indicate that MOG1 interacts with Sar1-GTPase, one of the most important proteins regulating ER export. Based on these novel findings, we hypothesize that MOG1 regulates ER export of Nav1.5 by regulating the Sar1-GTP cycle. Interestingly, we have found that overexpression of MOG1 in HEK293/tsA201 cells can fully rescue the reduced INa caused by trafficking defects of BrS mutation G1743R and SSS mutation D1275N in SCN5A. We surmise that overexpression of MOG1 can rescue trafficking defects of Nav1.5 mutations causing BrS and SSS in animal models containing mutations G1743R and D1275N as well as heterozygous Scn5a+/- mice (an existing model for BrS). Thus, in this project we will first determine whether overexpression of MOG1 by adeno- associated virus-mediated gene transfer can rescue the trafficking defects of Nav1.5 mutations G1743R and D1275N and attenuate related disease phenotypes in mouse models for BrS and SSS (Aim 1). Currently, no effective therapies exist for BrS or SSS except for invasive implantation of ICDs (Implantable Cardioverter Defibrillators) or pacemakers, respectively. Due to the invasiveness and many side effects associated with ICDs and pacemakers, we believe that the development of a non-invasive therapy, i.e. a novel MOG1- based gene therapy, is highly valuable for human patients. Then, we will utilize a series of integrative biochemical, molecular biological and cellular approaches to identify the molecular mechanisms by which MOG1 controls trafficking of Nav1.5 to cell surface (Aim 2), which may be used to enhance the efficacy of MOG1 gene therapy for BrS and SSS.

Public Health Relevance

A decrease of cardiac sodium currents in the heart causes many significant cardiovascular disorders, including Brugada syndrome (a lethal arrhythmia), sick sinus syndrome, common heart failure, and myocardial ischemia (coronary artery disease and heart attacks). The proposed studies will identify the molecular mechanism by which a small protein MOG1 shuttles the cardiac sodium channel onto the cell surface to increase sodium currents as a driver. The project will then demonstrate that increasing the level of MOG1 in the heart can attenuate disease symptoms associated with reduced sodium currents. If successful, our strategy of MOG1 gene transfer could be translated into an effective, non-invasive therapy for human patients. These studies may lead to development of a novel gene therapy to treat lethal arrhythmias and sudden death associated not only with Brugada syndrome and sick sinus syndrome, but also with more common diseases like myocardial ischemia and heart failure.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
1R01HL126729-01
Application #
8859323
Study Section
Special Emphasis Panel (ZRG1-TAG-Q (01))
Program Officer
Krull, Holly
Project Start
2015-04-01
Project End
2019-03-31
Budget Start
2015-04-01
Budget End
2016-03-31
Support Year
1
Fiscal Year
2015
Total Cost
$396,248
Indirect Cost
$146,249
Name
Cleveland Clinic Lerner
Department
Other Basic Sciences
Type
Schools of Medicine
DUNS #
135781701
City
Cleveland
State
OH
Country
United States
Zip Code
44195
Wang, Li; Wang, Xiaojing; Wang, Longfei et al. (2018) Identification of a new adtrp1-tfpi regulatory axis for the specification of primitive myelopoiesis and definitive hematopoiesis. FASEB J 32:183-194
Li, Xia; Poschmann, Sibylle; Chen, Qiuyun et al. (2018) De novo BK channel variant causes epilepsy by affecting voltage gating but not Ca2+ sensitivity. Eur J Hum Genet 26:220-229
Yu, Gang; Liu, Yinan; Qin, Jun et al. (2018) Mechanistic insights into the interaction of the MOG1 protein with the cardiac sodium channel Nav1.5 clarify the molecular basis of Brugada syndrome. J Biol Chem 293:18207-18217
Wang, Pengxia; Qin, Weixi; Wang, Pengyun et al. (2018) Genomic Variants in NEURL, GJA1 and CUX2 Significantly Increase Genetic Susceptibility to Atrial Fibrillation. Sci Rep 8:3297
Naji, Duraid Hamid; Tan, Chengcheng; Han, Fabin et al. (2018) Significant genetic association of a functional TFPI variant with circulating fibrinogen levels and coronary artery disease. Mol Genet Genomics 293:119-128
Wang, Fan; Wang, Isabel Z; Ellis, Stephen et al. (2018) Analysis of causal effect of APOA5 variants on premature coronary artery disease. Ann Hum Genet 82:437-447
Wang, Zhijie; Yu, Gang; Liu, Yinan et al. (2018) Small GTPases SAR1A and SAR1B regulate the trafficking of the cardiac sodium channel Nav1.5. Biochim Biophys Acta Mol Basis Dis 1864:3672-3684
Si, Wenxia; Xie, Wen; Deng, Wenbing et al. (2018) Angiotensin II increases angiogenesis by NF-?B-mediated transcriptional activation of angiogenic factor AGGF1. FASEB J 32:5051-5062
Li, Sisi; Xi, Quansheng; Zhang, Xiaoyu et al. (2018) Identification of a mutation in CNNM4 by whole exome sequencing in an Amish family and functional link between CNNM4 and IQCB1. Mol Genet Genomics 293:699-710
Wang, Xiaojing; Li, Jia; Yang, Zhongcheng et al. (2018) phlda3 overexpression impairs specification of hemangioblasts and vascular development. FEBS J 285:4071-4081

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