Nav1.5 is the major cardiac voltage-gated sodium channel encoded by [SCN5A](/genes/scn5a). It drives the fast inward sodium current underlying phase-0 depolarization in working myocardium and much of the cardiac conduction system.[@zimmer2023][@abriel2007] Functionally, Nav1.5 determines conduction velocity, excitability reserve, and susceptibility to ventricular and atrial rhythm instability when gating is disturbed.[@zimmer2023][@li2015]
Within NeuroWiki, Nav1.5 is important as a channelopathy benchmark: it shows how subtle gating defects, modifier genes, and structural context combine into heterogeneous clinical phenotypes.[@li2015][@kapplinger2018]
Structure And Electrophysiology
Nav1.5 shares the conserved Nav architecture (DI-DIV, each with S1-S6 segments) but has tissue-specific regulatory context in cardiomyocytes, including interaction with scaffolding and intercalated-disc proteins.[@zimmer2023][@abriel2007] Pathogenic variants can alter:
Nav1.5 is the major cardiac voltage-gated sodium channel encoded by [SCN5A](/genes/scn5a). It drives the fast inward sodium current underlying phase-0 depolarization in working myocardium and much of the cardiac conduction system.[@zimmer2023][@abriel2007] Functionally, Nav1.5 determines conduction velocity, excitability reserve, and susceptibility to ventricular and atrial rhythm instability when gating is disturbed.[@zimmer2023][@li2015]
Within NeuroWiki, Nav1.5 is important as a channelopathy benchmark: it shows how subtle gating defects, modifier genes, and structural context combine into heterogeneous clinical phenotypes.[@li2015][@kapplinger2018]
Structure And Electrophysiology
Nav1.5 shares the conserved Nav architecture (DI-DIV, each with S1-S6 segments) but has tissue-specific regulatory context in cardiomyocytes, including interaction with scaffolding and intercalated-disc proteins.[@zimmer2023][@abriel2007] Pathogenic variants can alter:
Peak sodium current density (loss-of-function phenotypes)
Late/persistent sodium current (gain-of-function phenotypes)
Voltage dependence and kinetics of activation/inactivation
Trafficking or membrane localization of channel complexes[@zimmer2023][@li2015][@ruan2012]
The resulting conduction instability can manifest across a spectrum rather than as isolated monogenic labels.[@li2015][@kapplinger2018]
Disease Spectrum
Arrhythmia And Conduction Disorders
SCN5A/Nav1.5 dysfunction is classically associated with inherited arrhythmia syndromes, including Brugada-pattern phenotypes, long-QT mechanisms, conduction disease, and overlap presentations.[@li2015][@kapplinger2018][@ruan2012][@antzelevitch2018]
A major contemporary point is pleiotropy: one variant may map to multiple electrophysiologic outcomes depending on background genetics and cellular environment.[@li2015][@kapplinger2018]
Beyond Rhythm-Only Framing
Newer analyses describe broader SCN5A channelopathy scope, including cardiomyopathic and occasional neurologic/epilepsy overlap phenotypes in specific families.[@li2015] This does not make Nav1.5 a primary neurodegeneration protein, but it reinforces a shared principle across brain and heart: channel dysfunction is often network disease, not single-parameter disease.[@zimmer2023][@li2015]
Relevance To Neurodegeneration Frameworks
Nav1.5 has limited direct AD/PD causality evidence. Its translational relevance is conceptual and methodological:
It provides mature genotype-phenotype curation paradigms applicable to CNS ion-channel targets.
It highlights why variant reclassification and functional validation are necessary before therapeutic claims.[@kapplinger2018][@ruan2012]
It supports cross-linking with [ion channel dysfunction in neurodegeneration](/mechanisms/ion-channel-dysfunction-neurodegeneration) and [sodium channel blockers for neurodegeneration](/therapeutics/sodium-channel-blockers-neurodegeneration).
Therapeutic Context
Clinical strategy depends on mechanism class rather than the gene label alone:[@li2015][@kapplinger2018]
Loss-of-function predominant states prioritize avoidance of pro-arrhythmic sodium-channel blockade and device-based risk mitigation when indicated.
Gain-of-function/late-current phenotypes may respond to selective late-current suppressive approaches in carefully selected patients.
The key lesson for neurodegeneration translational work: channel-targeted interventions require variant-aware, mechanism-aware trial design.
Open Questions
How should SCN5A variants be stratified for prospective mechanism-matched therapy?
Which non-coding and protein-interaction modifiers explain incomplete penetrance?
Can cardiac channelopathy functional pipelines be adapted to CNS sodium-channel targets?
See Also
[SCN5A](/genes/scn5a)
[Nav1.4 Sodium Channel](/proteins/nav1-4-protein)
[Nav1.9 Sodium Channel](/proteins/nav1-9-protein)
[Ion Channel Dysfunction in Neurodegeneration](/mechanisms/ion-channel-dysfunction-neurodegeneration)
[Sodium Channel Blockers for Neurodegeneration](/therapeutics/sodium-channel-blockers-neurodegeneration)
[Abriel H, Cardiac sodium channel Nav1.5 and its associated proteins (2007)](https://pubmed.ncbi.nlm.nih.gov/18033008/)
[Li W, Yin L, Shen C, Hu K, Ge J, Sun A, The cardiac sodium channel gene SCN5A and its gene product NaV1.5: Role in physiology and pathophysiology (2015)](https://pubmed.ncbi.nlm.nih.gov/26361848/)
[Kapplinger JD, Giudicessi JR, Ye D, et al, Enhanced Classification of Brugada Syndrome-Associated and Long-QT Syndrome-Associated Genetic Variants in the SCN5A-Encoded NaV1.5 Cardiac Sodium Channel (2018)](https://pubmed.ncbi.nlm.nih.gov/30203441/)
[Ruan Y, Liu N, Priori SG, Sodium channel mutations and arrhythmia (2012)](https://pubmed.ncbi.nlm.nih.gov/22460359/)