Dataset Information

K_V4.3 Expression Modulates Na_V1.5 Sodium Current.

ABSTRACT: In cardiomyocytes, the voltage-gated transient outward potassium current (I_to) is responsible for the phase-1 repolarization of the action potential (AP). Gain-of-function mutations in KCND3, the gene encoding the I_to carrying K_V4.3 channel, have been associated with Brugada syndrome (BrS). While the role of I_to in the pro-arrhythmic mechanism of BrS has been debated, recent studies have suggested that an increased I_to may directly affect cardiac conduction. However, the effects of an increased I_to on AP upstroke velocity or sodium current at the cellular level remain unknown. We here investigated the consequences of K_V4.3 overexpression on Na_V1.5 current and consequent sodium channel availability. We found that overexpression of K_V4.3 protein in HEK293 cells stably expressing Na_V1.5 (HEK293-Na_V1.5 cells) significantly reduced Na_V1.5 current density without affecting its kinetic properties. In addition, K_V4.3 overexpression decreased AP upstroke velocity in HEK293-Na_V1.5 cells, as measured with the alternating voltage/current clamp technique. These effects of K_V4.3 could not be explained by alterations in total Na_V1.5 protein expression. Using computer simulations employing a multicellular in silico model, we furthermore demonstrate that the experimentally observed increase in K_V4.3 current and concurrent decrease in Na_V1.5 current may result in a loss of conduction, underlining the potential functional relevance of our findings. This study gives the first proof of concept that K_V4.3 directly impacts on Na_V1.5 current. Future studies employing appropriate disease models should explore the potential electrophysiological implications in (patho)physiological conditions, including BrS associated with KCND3 gain-of-function mutations.

SUBMITTER: Portero V

PROVIDER: S-EPMC5857579 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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KV4.3 Expression Modulates NaV1.5 Sodium Current.

Portero Vincent V Wilders Ronald R Casini Simona S Charpentier Flavien F Verkerk Arie O AO Remme Carol Ann CA

Frontiers in physiology 20180312

In cardiomyocytes, the voltage-gated transient outward potassium current (Ito) is responsible for the phase-1 repolarization of the action potential (AP). Gain-of-function mutations in KCND3, the gene encoding the Ito carrying KV4.3 channel, have been associated with Brugada syndrome (BrS). While the role of Ito in the pro-arrhythmic mechanism of BrS has been debated, recent studies have suggested that an increased Ito may directly af ...[more]

PMID: 29593552

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Project description:RationaleThe cardiac sodium channel NaV1.5, encoded by SCN5A, produces the rapidly inactivating depolarizing current INa that is responsible for the initiation and propagation of the cardiac action potential. Acquired and inherited dysfunction of NaV1.5 results in either decreased peak INa or increased residual late INa (INa,L), leading to tachy/bradyarrhythmias and sudden cardiac death. Previous studies have shown that increased cellular NAD+ and NAD+/NADH ratio increase INa through suppression of mitochondrial reactive oxygen species and PKC-mediated NaV1.5 phosphorylation. In addition, NAD+-dependent deacetylation of NaV1.5 at K1479 by Sirtuin 1 increases NaV1.5 membrane trafficking and INa. The role of NAD+ precursors in modulating INa remains unknown.ObjectiveTo determine whether and by which mechanisms the NAD+ precursors nicotinamide riboside (NR) and nicotinamide (NAM) affect peak INa and INa,Lin vitro and cardiac electrophysiology in vivo.Methods and resultsThe effects of NAD+ precursors on the NAD+ metabolome and electrophysiology were studied using HEK293 cells expressing wild-type and mutant NaV1.5, rat neonatal cardiomyocytes (RNCMs), and mice. NR increased INa in HEK293 cells expressing NaV1.5 (500 μM: 51 ± 18%, p = .02, 5 mM: 59 ± 22%, p = .03) and RNCMs (500 μM: 60 ± 26%, p = .02, 5 mM: 74 ± 39%, p = .03) while reducing INa,L at the higher concentration (RNCMs, 5 mM: -45 ± 11%, p = .04). NR (5 mM) decreased NaV1.5 K1479 acetylation but increased INa in HEK293 cells expressing a mutant form of NaV1.5 with disruption of the acetylation site (NaV1.5-K1479A). Disruption of the PKC phosphorylation site abolished the effect of NR on INa. Furthermore, NAM (5 mM) had no effect on INa in RNCMs or in HEK293 cells expressing wild-type NaV1.5, but increased INa in HEK293 cells expressing NaV1.5-K1479A. Dietary supplementation with NR for 10-12 weeks decreased QTc in C57BL/6 J mice (0.35% NR: -4.9 ± 2.0%, p = .14; 1.0% NR: -9.5 ± 2.8%, p = .01).ConclusionsNAD+ precursors differentially regulate NaV1.5 via multiple mechanisms. NR increases INa, decreases INa,L, and warrants further investigation as a potential therapy for arrhythmic disorders caused by NaV1.5 deficiency and/or dysfunction.

Dataset Information

K_V4.3 Expression Modulates Na_V1.5 Sodium Current.

Publications

K<sub>V</sub>4.3 Expression Modulates Na<sub>V</sub>1.5 Sodium Current.

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