The voltage dependence of recovery from use-dependent block by QX-222 separates mechanisms for drug egress in the cardiac sodium channel

Abstract Background Mutations in gene SCN5A, encoding cardiac potential-dependent sodium channel Nav1.5, are associated with various arrhythmogenic disorders among which the Brugada syndrome (BrS) and the Long QT syndrome (LQT) are the best characterized. BrS1 is associated with sodium channel dysfunction, which can be reflected by decreased current, impaired activation and enhanced inactivation. We found two novel mutations in our patients with BrS and explored their effect on fast and slow inactivation of cardiac sodium channel. Purpose The aim of this study was to investigate the effect of BrS (Y739D, L1582P) mutations on different inactivation processes in in vitro model. Methods Y739D and L1582P substitutions were introduced in SCN5A cDNA using site-directed mutagenesis. Sodium currents were recorded at room temperature in transfected HEK293-T cells using patch-clamp technique with holding potential −100 mV. In order to access the fast steady-state inactivation curve we used double-pulse protocol with 10 ms prepulses. To analyze voltage-dependence of slow inactivation we used two-pulse protocol with 10s prepulse, 20ms test pulse and 25ms interpulse at −100mV to allow recovery from fast inactivation. Electrophysiological measurements are presented as mean ±SEM. Results Y739D mutation affects highly conserved tyrosine 739 among voltage-gated sodium and calcium channels in the segment IIS2. Mutation L1582P located in the loop IVS4-S5, and leucine in this position is not conserved among voltage-gated channels superfamily. We have shown that Y739D leads to significant changes in both fast and slow inactivation, whereas L1582P enhanced slow inactivation only. Steady-state fast inactivation for Y739D was shifted on 8.9 mV towards more negative potentials compare with that for WT, while L1582P did not enhanced fast inactivation (V1/2 WT: −62.8±1.7 mV; Y739D: −71.7±2.3 mV; L1582P: −58.7±1.4 mV). Slow inactivation was increased for both substitutions (INa (+20mV)/INa (−100mV) WT: 0.45±0.03; Y739D: 0,34±0.09: L1582P: 0.38±0.04). Steady-state fast inactivation Conclusions Both mutations, observed in patients with Brugada syndrome, influence on the slow inactivation process. Enhanced fast inactivation was shown only for Y739D mutant. The more dramatic alterations in sodium channel biophysical characteristics are likely linked with mutated residue conservativity. Acknowledgement/Funding RSF #17-15-01292

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Biochemical and biophysical studies of the interaction of class I antiarrhythmic drugs with the cardiac sodium channel

Drug Development Research ◽

10.1002/ddr.430330310 ◽

1994 ◽

Vol 33 (3) ◽

pp. 277-294 ◽

Cited By ~ 2

Author(s):

Gerald W. Zamponi ◽

Henry J. Duff ◽

Robert J. French ◽

Robert S. Sheldon

Keyword(s):

Sodium Channel ◽

Antiarrhythmic Drugs ◽

Class I ◽

Cardiac Sodium Channel ◽

Biophysical Studies

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Differential effects of cardiac sodium channel mutations on initiation of ventricular arrhythmias in patients with Brugada syndrome

Heart Rhythm ◽

10.1016/j.hrthm.2009.01.031 ◽

2009 ◽

Vol 6 (4) ◽

pp. 487-492 ◽

Cited By ~ 18

Author(s):

Hiroshi Morita ◽

Satoshi Nagase ◽

Daiji Miura ◽

Aya Miura ◽

Shigeki Hiramatsu ◽

...

Keyword(s):

Sodium Channel ◽

Brugada Syndrome ◽

Ventricular Arrhythmias ◽

Differential Effects ◽

Cardiac Sodium Channel

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A cardiac sodium channel mutation identified in Brugada syndrome associated with atrial standstill

Journal of Internal Medicine ◽

10.1046/j.0954-6820.2003.01247.x ◽

2004 ◽

Vol 255 (1) ◽

pp. 137-142 ◽

Cited By ~ 62

Author(s):

N. Takehara ◽

N. Makita ◽

J. Kawabe ◽

N. Sato ◽

Y. Kawamura ◽

...

Keyword(s):

Sodium Channel ◽

Brugada Syndrome ◽

Cardiac Sodium Channel ◽

Channel Mutation ◽

Sodium Channel Mutation

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P266Down regulation of the cardiac sodium channel Nav1.5 by the MAGUK protein CASK: role of its functional domains

Cardiovascular Research ◽

10.1093/cvr/cvy060.186 ◽

2018 ◽

Vol 114 (suppl_1) ◽

pp. S68-S68

Author(s):

A Beuriot ◽

C Eichel ◽

N Doisne ◽

F Louault ◽

A Coulombe ◽

...

Keyword(s):

Sodium Channel ◽

Functional Domains ◽

Cardiac Sodium Channel ◽

Maguk Protein

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Arrhythmic Phenotypes Are a Defining Feature of Dilated Cardiomyopathy-Associated SCN5A Variants: A Systematic Review

Circulation Genomic and Precision Medicine ◽

10.1161/circgen.121.003432 ◽

2021 ◽

Author(s):

Stacey Peters ◽

Bryony A. Thompson ◽

Mark Perrin ◽

Paul James ◽

Dominica Zentner ◽

...

Keyword(s):

Systematic Review ◽

Drug Therapy ◽

Dilated Cardiomyopathy ◽

Sodium Channel ◽

Early Recognition ◽

Treatment Success ◽

Atrial Arrhythmias ◽

Blocking Drug ◽

Cardiac Sodium Channel ◽

Channel Blocking

Background: Variants in the SCN5A gene, that encodes the cardiac sodium channel, Nav1.5, are associated with a highly arrhythmogenic form of dilated cardiomyopathy (DCM). Our aim was to review the phenotypes, natural history, functional effects, and treatment outcomes of DCM-associated rare SCN5A variants. Methods: A systematic review of reported DCM-associated rare SCN5A variants was undertaken using PubMed and Embase. Results: Eighteen SCN5A rare variants in 29 families with DCM (173 affected individuals) were identified. Eleven variants had undergone experimental evaluation, with 7 of these resulting in increased sustained current flow during the action potential (eg, increased window current) and at resting membrane potentials (eg, creation of a new gating pore current). These variants were located in transmembrane voltage-sensing domains and had a consistent phenotype characterized by frequent multifocal narrow and broad complex ventricular premature beats (VPB; 72% of affected relatives), ventricular arrhythmias (33%), atrial arrhythmias (32%), sudden cardiac death (13%), and DCM (56%). This VPB-predominant phenotype was not seen with 1 variant that increased late sodium current, or with variants that reduced peak current density or had mixed effects. In the latter groups, affected individuals mainly showed sinus node dysfunction, conduction defects, and atrial arrhythmias, with infrequent VPB and VA. DCM did not occur in the absence of arrhythmias for any variant. Twelve studies (23 total patients) reported treatment success in the VPB-predominant cardiomyopathy using sodium channel-blocking drug therapy. Conclusions: SCN5A variants can present with a diverse spectrum of primary arrhythmic features. A majority of DCM-associated variants cause a multifocal VPB-predominant cardiomyopathy that is reversible with sodium channel blocking drug therapy. Early recognition of the distinctive phenotype and prompt genetic testing to identify variant carriers are needed. Our findings have implications for interpretation and management of SCN5A variants found in DCM patients with and without arrhythmias.

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