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SCN5A

Domain

The sequence contains 4 internal repeats, each with 5 hydrophobic segments (S1, S2, S3, S5, S6) and one positively charged segment (S4). Segments S4 are probably the voltage-sensors and are characterized by a series of positively charged amino acids at every third position.

The IQ domain mediates association with calmodulin.

Function

Pore-forming subunit of Nav1.5, a voltage-gated sodium (Nav) channel that directly mediates the depolarizing phase of action potentials in excitable membranes. Navs, also called VGSCs (voltage-gated sodium channels) or VDSCs (voltage-dependent sodium channels), operate by switching between closed and open conformations depending on the voltage difference across the membrane. In the open conformation they allow Na(+) ions to selectively pass through the pore, along their electrochemical gradient. The influx of Na(+) ions provokes membrane depolarization, initiating the propagation of electrical signals throughout cells and tissues (PubMed:1309946, PubMed:21447824, PubMed:23085483, PubMed:23420830, PubMed:25370050, PubMed:26279430, PubMed:26392562, PubMed:26776555). Nav1.5 is the predominant sodium channel expressed in myocardial cells and it is responsible for the initial upstroke of the action potential in cardiac myocytes, thereby initiating the heartbeat (PubMed:11234013, PubMed:11804990, PubMed:12569159, PubMed:1309946). Required for normal electrical conduction including formation of the infranodal ventricular conduction system and normal action potential configuration, as a result of its interaction with XIRP2 (By similarity).

Involvement in disease

Progressive familial heart block 1A

PFHB1A

A cardiac bundle branch disorder characterized by progressive alteration of cardiac conduction through the His-Purkinje system, with a pattern of a right bundle-branch block and/or left anterior hemiblock occurring individually or together. It leads to complete atrio-ventricular block causing syncope and sudden death.

None

The disease is caused by variants affecting the gene represented in this entry.

Long QT syndrome 3

LQT3

A heart disorder characterized by a prolonged QT interval on the ECG and polymorphic ventricular arrhythmias. They cause syncope and sudden death in response to exercise or emotional stress, and can present with a sentinel event of sudden cardiac death in infancy.

None

The disease is caused by variants affecting the gene represented in this entry.

Brugada syndrome 1

BRGDA1

A tachyarrhythmia characterized by right bundle branch block and ST segment elevation on an electrocardiogram (ECG). It can cause the ventricles to beat so fast that the blood is prevented from circulating efficiently in the body. When this situation occurs, the individual will faint and may die in a few minutes if the heart is not reset.

None

The disease is caused by variants affecting the gene represented in this entry.

Sick sinus syndrome 1

SSS1

The term 'sick sinus syndrome' encompasses a variety of conditions caused by sinus node dysfunction. The most common clinical manifestations are syncope, presyncope, dizziness, and fatigue. Electrocardiogram typically shows sinus bradycardia, sinus arrest, and/or sinoatrial block. Episodes of atrial tachycardias coexisting with sinus bradycardia ('tachycardia-bradycardia syndrome') are also common in this disorder. SSS occurs most often in the elderly associated with underlying heart disease or previous cardiac surgery, but can also occur in the fetus, infant, or child without heart disease or other contributing factors. SSS1 onset is in utero, infancy, or early childhood.

None

The disease is caused by variants affecting the gene represented in this entry.

Familial paroxysmal ventricular fibrillation 1

VF1

A cardiac arrhythmia marked by fibrillary contractions of the ventricular muscle due to rapid repetitive excitation of myocardial fibers without coordinated contraction of the ventricle and by absence of atrial activity.

None

The disease is caused by variants affecting the gene represented in this entry.

Sudden infant death syndrome

SIDS

SIDS is the sudden death of an infant younger than 1 year that remains unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and review of clinical history. Pathophysiologic mechanisms for SIDS may include respiratory dysfunction, cardiac dysrhythmias, cardiorespiratory instability, and inborn errors of metabolism, but definitive pathogenic mechanisms precipitating an infant sudden death remain elusive.

None

Disease susceptibility is associated with variants affecting the gene represented in this entry.

Atrial standstill 1

ATRST1

A rare arrhythmia characterized by the absence of electrical and mechanical activity in the atria. Electrocardiographically, it is characterized by bradycardia, the absence of P waves, and a junctional narrow complex escape rhythm.

None

The disease may be caused by variants affecting distinct genetic loci, including the gene represented in this entry. A mutation in SCN5A has been detected in combination with a rare GJA5 genotype in a large family with atrial standstill.

Cardiomyopathy, dilated, 1E

CMD1E

A disorder characterized by ventricular dilation and impaired systolic function, resulting in congestive heart failure and arrhythmia. Patients are at risk of premature death.

None

The disease is caused by variants affecting the gene represented in this entry.

Atrial fibrillation, familial, 10

ATFB10

A familial form of atrial fibrillation, a common sustained cardiac rhythm disturbance. Atrial fibrillation is characterized by disorganized atrial electrical activity and ineffective atrial contraction promoting blood stasis in the atria and reduces ventricular filling. It can result in palpitations, syncope, thromboembolic stroke, and congestive heart failure.

None

The disease is caused by variants affecting the gene represented in this entry.

Post-translational modifications

Ubiquitinated by NEDD4L; which promotes its endocytosis. Does not seem to be ubiquitinated by NEDD4 or WWP2.

Phosphorylation at Ser-1503 by PKC in a highly conserved cytoplasmic loop slows inactivation of the sodium channel and reduces peak sodium currents (Probable). Regulated through phosphorylation by CaMK2D (By similarity).

Lacks the cysteine which covalently binds the conotoxin GVIIJ. This cysteine (position 868) is speculated in other sodium channel subunits alpha to be implied in covalent binding with the sodium channel subunit beta-2 or beta-4.

N-glycosylated at Asn-318, probably hinders potential interaction with regulatory subunits.

Sequence Similarities

Belongs to the sodium channel (TC 1.A.1.10) family. Nav1.5/SCN5A subfamily.

Tissue Specificity

Found in jejunal circular smooth muscle cells (at protein level). Expressed in human atrial and ventricular cardiac muscle but not in adult skeletal muscle, brain, myometrium, liver, or spleen. Isoform 4 is expressed in brain.

Cellular localization

Alternative names

Sodium channel protein type 5 subunit alpha, Sodium channel protein cardiac muscle subunit alpha, Sodium channel protein type V subunit alpha, Voltage-gated sodium channel subunit alpha Nav1.5, hH1, SCN5A

swissprot:Q14524