Analyses of a novel SCN5A mutation (C1850S): conduction vs. repolarization disorder hypotheses in the Brugada syndrome

Brugada syndrome (BrS) is a rare inherited disease that can give rise to ventricular arrhythmia and ultimately sudden cardiac death. Numerous loss-of-function mutations in the cardiac sodium channel Nav1.5 have been associated with BrS. However, few mutations in the auxiliary Navβ1-4 subunits have been linked to this disease. Here we investigated differences in expression and function between Navβ1 and Navβ1b and whether the H162P/Navβ1b mutation found in a BrS patient is likely to be the underlying cause of disease. The impact of Navβ subunits was investigated by patch-clamp electrophysiology, and the obtained in vitro values were used for subsequent in silico modeling. We found that Navβ1b transcripts were expressed at higher levels than Navβ1 transcripts in the human heart. Navβ1 and Navβ1b coexpressed with Nav1.5 induced a negative shift on steady state of activation and inactivation compared with Nav1.5 alone. Furthermore, Navβ1b was found to increase the current level when coexpressed with Nav1.5, Navβ1b/H162P mutated subunit peak current density was reduced by 48% (-645 ± 151 vs. -334 ± 71 pA/pF), V1/2 steady-state inactivation shifted by -6.7 mV (-70.3 ± 1.5 vs. -77.0 ± 2.8 mV), and time-dependent recovery from inactivation slowed by >50% compared with coexpression with Navβ1b wild type. Computer simulations revealed that these electrophysiological changes resulted in a reduction in both action potential amplitude and maximum upstroke velocity. The experimental data thereby indicate that Navβ1b/H162P results in reduced sodium channel activity functionally affecting the ventricular action potential. This result is an important replication to support the notion that BrS can be linked to the function of Navβ1b and is associated with loss-of-function of the cardiac sodium channel.

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“…All experiments were performed on a minimum of three batches of transfected cells. Data analyses were performed as previously described (23).…”

Section: Methodsmentioning

confidence: 99%

Investigations of the Na_vβ1b sodium channel subunit in human ventricle; functional characterization of the H162P Brugada syndrome mutant

Yuan

Koivumäki

Liang

et al. 2014

American Journal of Physiology-Heart and Circulatory Physiology

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“…Since then, many mutations in all domains of SCN5A have been associated with LQTS [Ackerman et al, 2004;Hofman-Bang et al, 2006;Napolitano et al, 2005], some in CCD [Bezzina et al, 2003;Laitinen-Forsblom et al, 2006;Petitprez et al, 2008;Probst et al, 2006], AF [Darbar et al, 2008;Makiyama et al, 2008b], and DCM [Olson et al, 2005]. In the clinical sudden infant and adult death syndromes (SIDS and SADS), mutations are also found in SCN5A Behr et al, 2008;Wang et al, 2007].…”

Section: Brs1-mutations In Scn5amentioning

confidence: 99%

The genetic basis of Brugada syndrome: A mutation update

et al. 2009

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Brugada syndrome (BrS) is a condition characterized by a distinct ST-segment elevation in the right precordial leads of the electrocardiogram and, clinically, by an increased risk of cardiac arrhythmia and sudden death. The condition predominantly exhibits an autosomal dominant pattern of inheritance with an average prevalence of 5:10,000 worldwide. Currently, more than 100 mutations in seven genes have been associated with BrS. Loss-of-function mutations in SCN5A, which encodes the a-subunit of the Na v 1.5 sodium ion channel conducting the depolarizing I Na current, causes 15-20% of BrS cases. A few mutations have been described in GPD1L, which encodes glycerol-3-phosphate dehydrogenase-1 like protein; CACNA1C, which encodes the a-subunit of the Ca v 1.2 ion channel conducting the depolarizing I L,Ca current; CACNB2, which encodes the stimulating b2-subunit of the Ca v 1.2 ion channel; SCN1B and SCN3B, which, in the heart, encodes b-subunits of the Na v 1.5 sodium ion channel, and KCNE3, which encodes the ancillary inhibitory b-subunit of several potassium channels including the Kv4.3 ion channel conducting the repolarizing potassium I to current. BrS exhibits variable expressivity, reduced penetrance, and ''mixed phenotypes,'' where families contain members with BrS as well as long QT syndrome, atrial fibrillation, short QT syndrome, conduction disease, or structural heart disease, have also been described.

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“…For electrophysiological studies, HEK293 cells were transiently co-transfected with 0.4 µg wild type (WT) or R121W, or 0.2 µg WT + 0.2 µg R121W Na v 1.5 constructs together with 0.2 µg of pcDNA3-EGFP as a reporter gene. Patch-clamp experiments were performed at room temperature (20–22°C) 2 days after transfection [6]. …”

Section: Methodsmentioning

confidence: 99%

“…The cells were lysed in buffer (320 m M sucrose, 5 m M sodium phosphate, within a protease inhibitor cocktail tablet, pH 7.4) [6]. Band density was quantified by Quantity-One software.…”

Section: Methodsmentioning

confidence: 99%

Sick Sinus Syndrome, Progressive Cardiac Conduction Disease, Atrial Flutter and Ventricular Tachycardia Caused by a Novel <i>SCN5A</i> Mutation

et al. 2010

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Mutations in the cardiac sodium channel encoded by the gene SCN5A can result in a wide array of phenotypes. We report a case of a young male with a novel SCN5A mutation (R121W) afflicted by sick sinus syndrome, progressive cardiac conduction disorder, atrial flutter and ventricular tachycardia. His father carried the same mutation, but had a milder phenotype, presenting with progressive cardiac conduction later in life. The mutation was found to result in a loss-of-function in the sodium current. In conclusion, the same SCN5A mutation can result in a wide array of clinical phenotypes and perhaps the spectrum of SCN5A loss-of-function associated disease entities should be viewed as one syndrome.

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Analyses of a novel SCN5A mutation (C1850S): conduction vs. repolarization disorder hypotheses in the Brugada syndrome

Abstract: Our data confirm that mutations of the C-terminal domain of Na(v)1.5 alter the inactivation of the channel and support the notion that conduction alterations may play a significant role in the pathogenesis of BrS.

Cited by 37 publications

References 27 publications

Investigations of the Na_vβ1b sodium channel subunit in human ventricle; functional characterization of the H162P Brugada syndrome mutant

Investigations of the Na_vβ1b sodium channel subunit in human ventricle; functional characterization of the H162P Brugada syndrome mutant

The genetic basis of Brugada syndrome: A mutation update

Sick Sinus Syndrome, Progressive Cardiac Conduction Disease, Atrial Flutter and Ventricular Tachycardia Caused by a Novel <i>SCN5A</i> Mutation

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Analyses of a novel SCN5A mutation (C1850S): conduction vs. repolarization disorder hypotheses in the Brugada syndrome

Abstract: Our data confirm that mutations of the C-terminal domain of Na(v)1.5 alter the inactivation of the channel and support the notion that conduction alterations may play a significant role in the pathogenesis of BrS.

Cited by 37 publications

References 27 publications

Investigations of the Navβ1b sodium channel subunit in human ventricle; functional characterization of the H162P Brugada syndrome mutant

Investigations of the Navβ1b sodium channel subunit in human ventricle; functional characterization of the H162P Brugada syndrome mutant

The genetic basis of Brugada syndrome: A mutation update

Sick Sinus Syndrome, Progressive Cardiac Conduction Disease, Atrial Flutter and Ventricular Tachycardia Caused by a Novel <i>SCN5A</i> Mutation

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Investigations of the Na_vβ1b sodium channel subunit in human ventricle; functional characterization of the H162P Brugada syndrome mutant

Investigations of the Na_vβ1b sodium channel subunit in human ventricle; functional characterization of the H162P Brugada syndrome mutant