{"gene":"SCN3B","run_date":"2026-04-28T20:42:07","timeline":{"discoveries":[{"year":2001,"finding":"SCN3B (β3 subunit) co-expressed with SCN5A (Nav1.5) in Xenopus oocytes produced a ~3-fold increase in functional sodium channel expression, a depolarizing shift in steady-state inactivation half-voltage, and faster recovery from inactivation compared to SCN5A alone; these effects were distinct from those of SCN1B, indicating SCN3B modulates Nav1.5 kinetics and membrane targeting.","method":"Xenopus oocyte co-expression, cell-attached macropatch recording, Northern/Western blot","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 1-2 — functional reconstitution in oocytes with electrophysiology, replicated across multiple kinetic parameters","pmids":["11744748"],"is_preprint":false},{"year":2004,"finding":"SCN3B is a p53-inducible gene: p53 directly binds two response elements (upstream of exon 1 and in intron 3) to drive SCN3B transcription; SCN3B protein localizes to the endoplasmic reticulum, and its overexpression induces apoptosis and suppresses colony formation, placing SCN3B in a p53-dependent apoptotic pathway.","method":"Chromatin immunoprecipitation, reporter gene assay, adenoviral overexpression, colony formation assay, immunofluorescence localization","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods (ChIP, reporter assay, functional apoptosis assay, localization) in single study","pmids":["15334053"],"is_preprint":false},{"year":2009,"finding":"The SCN3B loss-of-function mutation V54G reduces peak Nav1.5 sodium current and causes a positive shift in inactivation; co-immunoprecipitation showed Navβ3 physically associates with Nav1.5, and immunocytochemistry demonstrated that V54G dramatically reduces trafficking of Nav1.5 to the plasma membrane.","method":"Whole-cell patch clamp (HEK-293 and COS cells), co-immunoprecipitation, immunocytochemistry","journal":"Cardiovascular research","confidence":"High","confidence_rationale":"Tier 1-2 — reciprocal functional assay + Co-IP + localization, multiple cell systems","pmids":["20042427"],"is_preprint":false},{"year":2009,"finding":"Scn3b knockout mice show reduced peak Na+ current density, negative shift of inactivation in ventricular myocytes, shorter ventricular effective refractory periods, and inducible ventricular tachycardia in Langendorff-perfused hearts, establishing Scn3b as a regulator of ventricular sodium channel function and arrhythmia susceptibility in vivo.","method":"Scn3b−/− knockout mouse (homologous recombination), whole-cell patch clamp of isolated myocytes, Langendorff perfusion, programmed electrical stimulation, RT-PCR","journal":"Progress in biophysics and molecular biology","confidence":"High","confidence_rationale":"Tier 2 — clean KO mouse with cellular electrophysiology and intact-heart phenotype","pmids":["19351516"],"is_preprint":false},{"year":2009,"finding":"Scn3b knockout mice exhibit slower heart rates, longer P-wave durations, prolonged PR intervals, sinus node dysfunction, and atrial fibrillation induced by burst pacing, demonstrating Scn3b is required for normal sino-atrial and intra-cardiac conduction.","method":"Scn3b−/− knockout mouse, in vivo ECG, Langendorff perfusion with atrial electrogram recordings, burst pacing, immunofluorescence","journal":"Acta physiologica","confidence":"High","confidence_rationale":"Tier 2 — clean KO with multiple electrophysiological readouts and protein-level confirmation","pmids":["19796257"],"is_preprint":false},{"year":2010,"finding":"SCN3B mutations R6K, L10P, and M161T identified in lone AF patients all cause loss-of-function reduction in sodium current when expressed in heterologous systems, supporting a mechanism whereby decreased Nav1.5 current enhances AF susceptibility.","method":"Whole-cell patch clamp in heterologous expression system, mutational analysis","journal":"Cardiovascular research","confidence":"Medium","confidence_rationale":"Tier 2 — functional electrophysiology on patient-derived mutations, single lab","pmids":["21051419"],"is_preprint":false},{"year":2010,"finding":"The SCN3B A130V mutation found in a lone AF patient dramatically reduces Nav1.5 sodium current density without affecting channel kinetics; when co-expressed with wild-type SCN3B, A130V negates WT function (dominant-negative mechanism); surface biotinylation showed A130V does not affect cell surface expression of Nav1.5 or SCN3B, suggesting it impairs ion conduction rather than trafficking.","method":"Whole-cell patch clamp (HEK293/Nav1.5 stable line), co-expression dominant-negative assay, surface biotinylation/Western blot","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods establishing dominant-negative mechanism and ruling out trafficking defect","pmids":["20558140"],"is_preprint":false},{"year":2012,"finding":"The SCN3B Val110Ile mutation associated with Brugada syndrome impairs cytoplasmic trafficking of Nav1.5, reduces its cell surface expression, and significantly decreases sodium current in transfected cells.","method":"Direct sequencing, whole-cell patch clamp, cell surface expression assay in transfected cells","journal":"Circulation journal","confidence":"Medium","confidence_rationale":"Tier 2 — functional electrophysiology + surface expression, single lab","pmids":["23257389"],"is_preprint":false},{"year":2016,"finding":"SCN3B is highly expressed in embryonic hearts and iPSC-derived cardiomyocytes; SCN3B augments INa of loss-of-function SCN5A E1784K mutant channels; knockdown of SCN3B in LQTS3/BrS iPSC-derived cardiomyocytes unmasks the Brugada syndrome electrophysiological phenotype, demonstrating that embryonic SCN3B expression masks BrS disease manifestation.","method":"iPSC-derived cardiomyocytes, siRNA knockdown, heterologous expression electrophysiology, patch clamp","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 — iPSC disease model with genetic rescue/knockdown and heterologous functional validation","pmids":["27677334"],"is_preprint":false},{"year":2016,"finding":"IL-2 upregulates SCN3B transcript and protein levels (via p53 induction) in cardiac cells and increases sodium current density; the effect on sodium current is independent of SCN3B alone, suggesting a broader regulatory network.","method":"qRT-PCR, Western blot, whole-cell patch clamp, SCN3B knockdown in HL-1 and HEK293 cells","journal":"BMC cardiovascular disorders","confidence":"Medium","confidence_rationale":"Tier 2-3 — multiple methods but mechanistic independence of SCN3B from IL-2 Na+ current effect reduces clarity","pmids":["26728597"],"is_preprint":false},{"year":2022,"finding":"Two rare 5′UTR variants of SCN3B are associated with lone AF; the c.-324C>A variant increases SCN3B transcriptional activity, representing a gain-of-function regulatory mutation; GATA4 was identified as a transcriptional regulator of SCN3B that interacts with this variant to enhance SCN3B expression.","method":"Luciferase reporter assay, transcription factor binding analysis, patient sequencing","journal":"Life (Basel, Switzerland)","confidence":"Medium","confidence_rationale":"Tier 2-3 — reporter assay with GATA4 interaction, single lab","pmids":["36362949"],"is_preprint":false},{"year":2022,"finding":"miR-190a-5p directly suppresses IL-2 expression (validated by luciferase reporter assay), thereby reducing IL-2-driven upregulation of SCN3B sodium current; miR-190a-5p inhibitor reverses this suppression, defining a miR-190a-5p/IL-2/SCN3B regulatory axis in cardiac arrhythmia.","method":"Luciferase reporter assay, qRT-PCR, whole-cell patch clamp, FISH","journal":"Frontiers in cardiovascular medicine","confidence":"Medium","confidence_rationale":"Tier 2-3 — multiple methods establishing miRNA-target relationship and functional sodium current link","pmids":["35083300"],"is_preprint":false},{"year":2025,"finding":"The SCN3B in-frame deletion ΔT138 causes minimal gross structural perturbation (confirmed by circular dichroism and computational modeling) but reduces peak Nav1.5 current and channel availability and accelerates fast inactivation when both WT and ΔT138 β3 are co-expressed; surface biotinylation and co-immunoprecipitation showed normal β3 surface expression and intact interaction with Nav1.5.","method":"Site-directed mutagenesis, circular dichroism spectroscopy, whole-cell patch clamp, surface biotinylation, co-immunoprecipitation, surface cross-linking","journal":"Journal of molecular and cellular cardiology","confidence":"High","confidence_rationale":"Tier 1 — reconstitution with mutagenesis, structural analysis, and multiple functional assays in single study","pmids":["39761910"],"is_preprint":false},{"year":2024,"finding":"SCN3B P87I mutation reduces peak INa by ~60% and decreases plasma membrane localization of both SCN3B and Nav1.5 (SCN5A) as shown by confocal imaging and Western blot, with computational cardiac action potential simulations predicting altered endocardial/epicardial action potential morphology.","method":"Whole-cell patch clamp, confocal immunofluorescence, Western blot, computational action potential modeling","journal":"Frontiers in cardiovascular medicine","confidence":"Medium","confidence_rationale":"Tier 2-3 — functional + localization data, single lab, no Co-IP","pmids":["38450374"],"is_preprint":false},{"year":2025,"finding":"Overexpression of SCN3B in breast cancer cell lines inhibits cell migration and invasion, and influences expression of >800 genes associated with cell migration and extracellular matrix interactions.","method":"Overexpression in breast cancer cell lines, migration/invasion assays, gene expression profiling","journal":"Biochemical genetics","confidence":"Low","confidence_rationale":"Tier 3 — single lab, phenotypic assay without defined molecular mechanism","pmids":["40072811"],"is_preprint":false}],"current_model":"SCN3B encodes the voltage-gated sodium channel β3 (Navβ3) auxiliary subunit that physically associates with the cardiac α-subunit Nav1.5 (SCN5A), promotes its trafficking to the plasma membrane, and modulates its kinetics (shifting steady-state inactivation and accelerating recovery from inactivation); loss-of-function SCN3B mutations reduce Nav1.5 surface expression and peak sodium current, causing arrhythmia syndromes including Brugada syndrome, idiopathic ventricular fibrillation, and atrial fibrillation, while SCN3B transcription is directly regulated by p53 (via intronic and upstream response elements) and by GATA4, and the protein also participates in a p53-dependent apoptotic pathway localized to the endoplasmic reticulum."},"narrative":{"teleology":[{"year":2001,"claim":"The fundamental question of whether the β3 subunit modulates the cardiac sodium channel was answered: co-expression with Nav1.5 increased functional channel expression ~3-fold, shifted inactivation, and accelerated recovery, establishing SCN3B as a kinetic and trafficking modulator of Nav1.5.","evidence":"Xenopus oocyte co-expression with macropatch electrophysiology","pmids":["11744748"],"confidence":"High","gaps":["Physical interaction between β3 and Nav1.5 was not directly demonstrated","In vivo cardiac relevance not yet tested","Mechanism of increased functional expression (trafficking vs. gating) unresolved"]},{"year":2004,"claim":"The unexpected finding that p53 directly transactivates SCN3B and that SCN3B overexpression induces apoptosis placed the sodium channel subunit in a p53-dependent cell-death pathway at the endoplasmic reticulum, broadening its biology beyond ion conduction.","evidence":"ChIP for p53 binding, luciferase reporter assays, adenoviral overexpression with colony formation and apoptosis assays, immunofluorescence localization","pmids":["15334053"],"confidence":"High","gaps":["Downstream apoptotic mechanism (how ER-localized β3 triggers cell death) undefined","Relevance of the p53–SCN3B axis in cardiac tissue not explored","No confirmation that endogenous sodium currents mediate the apoptotic effect"]},{"year":2009,"claim":"Loss of Scn3b in knockout mice demonstrated in vivo cardiac necessity: reduced sodium current, ventricular tachycardia susceptibility, sinus node dysfunction, and atrial fibrillation established Navβ3 as required for normal cardiac conduction and rhythm.","evidence":"Scn3b−/− knockout mice with whole-cell patch clamp of isolated myocytes, in vivo ECG, Langendorff perfusion with programmed electrical stimulation","pmids":["19351516","19796257"],"confidence":"High","gaps":["Whether β3 loss alters expression/localization of other β subunits or compensatory channels not addressed","Mechanism linking reduced current to arrhythmia substrate (fibrosis, gap junctions) not defined"]},{"year":2009,"claim":"The first human disease-causing mutation (V54G) was shown to reduce Nav1.5 trafficking to the plasma membrane and decrease sodium current, establishing a direct physical association by co-immunoprecipitation and linking SCN3B loss-of-function to Brugada syndrome.","evidence":"Whole-cell patch clamp in HEK-293 and COS cells, co-immunoprecipitation, immunocytochemistry","pmids":["20042427"],"confidence":"High","gaps":["Structural basis for how V54G disrupts trafficking unknown","Whether V54G also affects interaction with other Nav α subunits not tested"]},{"year":2010,"claim":"Multiple SCN3B mutations in atrial fibrillation patients revealed that β3 dysfunction can operate through at least two distinct mechanisms — impaired trafficking (most mutations) versus dominant-negative suppression of ion conduction without trafficking defect (A130V) — diversifying the pathophysiological repertoire.","evidence":"Whole-cell patch clamp, co-expression dominant-negative assay, surface biotinylation in HEK293 cells","pmids":["21051419","20558140"],"confidence":"High","gaps":["Structural basis for dominant-negative mechanism of A130V unknown","Whether dominant-negative mutations affect other sodium channel isoforms untested"]},{"year":2016,"claim":"High SCN3B expression in embryonic/iPSC-derived cardiomyocytes was shown to mask the Brugada syndrome phenotype of SCN5A mutations, explaining why BrS manifests in adulthood when SCN3B expression declines, and an IL-2/p53 axis was identified that upregulates SCN3B transcription.","evidence":"iPSC-derived cardiomyocytes with siRNA knockdown and heterologous expression electrophysiology; qRT-PCR, Western blot, and patch clamp for IL-2 studies","pmids":["27677334","26728597"],"confidence":"High","gaps":["Developmental regulation of SCN3B expression in human heart not mapped in vivo","IL-2 effect on sodium current was partly independent of SCN3B, suggesting additional mediators"]},{"year":2022,"claim":"Identification of GATA4 as a transcriptional regulator of SCN3B via the 5′UTR and a miR-190a-5p/IL-2/SCN3B regulatory axis extended the upstream control network governing SCN3B expression in the heart.","evidence":"Luciferase reporter assays, transcription factor binding analysis, qRT-PCR, whole-cell patch clamp","pmids":["36362949","35083300"],"confidence":"Medium","gaps":["GATA4 regulation not confirmed by ChIP in cardiac cells","Physiological relevance of miR-190a-5p axis in cardiac tissue in vivo not demonstrated","Interplay between GATA4 and p53 regulatory inputs uncharacterized"]},{"year":2025,"claim":"Structural-functional dissection of the ΔT138 in-frame deletion showed that β3 mutations can alter Nav1.5 gating (reducing current and accelerating inactivation) without disrupting β3 structure, surface expression, or physical interaction with Nav1.5, defining a third loss-of-function mechanism — pure gating modulation.","evidence":"Site-directed mutagenesis, circular dichroism spectroscopy, whole-cell patch clamp, surface biotinylation, co-immunoprecipitation","pmids":["39761910"],"confidence":"High","gaps":["Atomic-resolution structure of β3–Nav1.5 complex not available","Whether ΔT138 mechanism applies in cardiomyocytes not tested"]},{"year":null,"claim":"Key unresolved questions include the atomic structure of the β3–Nav1.5 interface, the mechanism by which ER-localized β3 induces p53-dependent apoptosis, and whether β3 modulates neuronal or other non-cardiac sodium channel isoforms in vivo.","evidence":"","pmids":[],"confidence":"High","gaps":["No high-resolution structure of β3 alone or in complex with Nav1.5","Apoptotic mechanism downstream of β3 at the ER undefined","Role of β3 with non-cardiac Nav α-subunits not functionally characterized in native tissues"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,2,6,12]},{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,3,6]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[2,6,7,13]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[1]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,3,8]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,3,4]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[2,7,13]}],"complexes":["Voltage-gated sodium channel complex (Nav1.5/β3)"],"partners":["SCN5A","GATA4","TP53"],"other_free_text":[]},"mechanistic_narrative":"SCN3B encodes the voltage-gated sodium channel β3 auxiliary subunit (Navβ3), which physically associates with the pore-forming α-subunit Nav1.5 (SCN5A) to promote its trafficking to the plasma membrane and modulate channel gating — increasing functional sodium channel expression, shifting steady-state inactivation, and accelerating recovery from inactivation [PMID:11744748, PMID:20042427]. Scn3b-knockout mice exhibit reduced ventricular sodium current density, sinus node dysfunction, conduction slowing, and inducible ventricular tachycardia and atrial fibrillation, establishing Navβ3 as essential for normal cardiac electrical function [PMID:19351516, PMID:19796257]. Loss-of-function SCN3B mutations cause Brugada syndrome, idiopathic ventricular fibrillation, and atrial fibrillation through reduced Nav1.5 current arising from impaired trafficking, altered gating, or dominant-negative suppression of channel conductance [PMID:20042427, PMID:20558140, PMID:23257389, PMID:21051419]. SCN3B transcription is directly activated by p53 via intronic and upstream response elements and by GATA4 at the 5′UTR, and SCN3B overexpression induces apoptosis, linking the gene to a p53-dependent cell-death pathway at the endoplasmic reticulum [PMID:15334053, PMID:36362949]."},"prefetch_data":{"uniprot":{"accession":"Q9NY72","full_name":"Sodium channel regulatory subunit beta-3","aliases":[],"length_aa":215,"mass_kda":24.7,"function":"Regulatory subunit of multiple voltage-gated sodium (Nav) channels directly mediating the depolarization of 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. The accessory beta subunits participate in localization and functional modulation of the Nav channels (PubMed:20558140, PubMed:21051419). Modulates the activity of SCN2A/Nav1.2, causing a hyperpolarizing shift in the voltage-dependence of inactivation of the channel and increasing the fraction of channels operating in the fast gating mode (By similarity). Modulates the activity of SCN5A/Nav1.5 (PubMed:20558140, PubMed:21051419, PubMed:24567321, PubMed:31950564). Could also regulate the atypical sodium channel SCN7A/Nav2.1 (PubMed:35301303). Modulates the activity of SCN10A/Nav1.8, regulating its oligomerization and accelerating the recovery from inactivation (PubMed:14975698)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q9NY72/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SCN3B","classification":"Not Classified","n_dependent_lines":5,"n_total_lines":1208,"dependency_fraction":0.0041390728476821195},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/SCN3B","total_profiled":1310},"omim":[{"mim_id":"615378","title":"ATRIAL FIBRILLATION, FAMILIAL, 14; ATFB14","url":"https://www.omim.org/entry/615378"},{"mim_id":"615377","title":"ATRIAL FIBRILLATION, FAMILIAL, 13; ATFB13","url":"https://www.omim.org/entry/615377"},{"mim_id":"613120","title":"BRUGADA SYNDROME 7; BRGDA7","url":"https://www.omim.org/entry/613120"},{"mim_id":"611819","title":"LONG QT SYNDROME 10; LQT10","url":"https://www.omim.org/entry/611819"},{"mim_id":"608583","title":"ATRIAL FIBRILLATION, FAMILIAL, 1; ATFB1","url":"https://www.omim.org/entry/608583"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"},{"location":"Vesicles","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":73.3},{"tissue":"pituitary gland","ntpm":26.6}],"url":"https://www.proteinatlas.org/search/SCN3B"},"hgnc":{"alias_symbol":["HSA243396","SCNB3"],"prev_symbol":[]},"alphafold":{"accession":"Q9NY72","domains":[{"cath_id":"2.60.40.10","chopping":"26-150","consensus_level":"high","plddt":91.5392,"start":26,"end":150},{"cath_id":"1.20.5","chopping":"151-185","consensus_level":"medium","plddt":93.8957,"start":151,"end":185}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NY72","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NY72-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NY72-F1-predicted_aligned_error_v6.png","plddt_mean":86.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SCN3B","jax_strain_url":"https://www.jax.org/strain/search?query=SCN3B"},"sequence":{"accession":"Q9NY72","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NY72.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NY72/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NY72"}},"corpus_meta":[{"pmid":"21051419","id":"PMC_21051419","title":"Mutations in sodium channel β-subunit SCN3B are associated with early-onset lone atrial fibrillation.","date":"2010","source":"Cardiovascular research","url":"https://pubmed.ncbi.nlm.nih.gov/21051419","citation_count":99,"is_preprint":false},{"pmid":"11744748","id":"PMC_11744748","title":"The sodium channel beta-subunit SCN3b modulates the kinetics of SCN5a and is expressed heterogeneously in sheep heart.","date":"2001","source":"The Journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/11744748","citation_count":92,"is_preprint":false},{"pmid":"20558140","id":"PMC_20558140","title":"Functional dominant-negative mutation of sodium channel subunit gene SCN3B associated with atrial fibrillation in a Chinese GeneID population.","date":"2010","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/20558140","citation_count":65,"is_preprint":false},{"pmid":"39289188","id":"PMC_39289188","title":"Is the voltage-gated sodium channel β3 subunit (SCN3B) a biomarker for glioma?","date":"2024","source":"Functional & integrative genomics","url":"https://pubmed.ncbi.nlm.nih.gov/39289188","citation_count":64,"is_preprint":false},{"pmid":"20042427","id":"PMC_20042427","title":"Loss-of-function mutation of the SCN3B-encoded sodium channel {beta}3 subunit associated with a case of idiopathic ventricular fibrillation.","date":"2009","source":"Cardiovascular research","url":"https://pubmed.ncbi.nlm.nih.gov/20042427","citation_count":63,"is_preprint":false},{"pmid":"23257389","id":"PMC_23257389","title":"Novel SCN3B mutation associated with brugada syndrome affects intracellular trafficking and function of Nav1.5.","date":"2012","source":"Circulation journal : official journal of the Japanese Circulation Society","url":"https://pubmed.ncbi.nlm.nih.gov/23257389","citation_count":60,"is_preprint":false},{"pmid":"15334053","id":"PMC_15334053","title":"Identification of SCN3B as a novel p53-inducible proapoptotic gene.","date":"2004","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/15334053","citation_count":60,"is_preprint":false},{"pmid":"19351516","id":"PMC_19351516","title":"Scn3b knockout mice exhibit abnormal ventricular electrophysiological properties.","date":"2009","source":"Progress in biophysics and molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/19351516","citation_count":53,"is_preprint":false},{"pmid":"26728597","id":"PMC_26728597","title":"Regulation of SCN3B/scn3b by Interleukin 2 (IL-2): IL-2 modulates SCN3B/scn3b transcript expression and increases sodium current in myocardial cells.","date":"2016","source":"BMC cardiovascular disorders","url":"https://pubmed.ncbi.nlm.nih.gov/26728597","citation_count":45,"is_preprint":false},{"pmid":"19796257","id":"PMC_19796257","title":"Scn3b knockout mice exhibit abnormal sino-atrial and cardiac conduction properties.","date":"2009","source":"Acta physiologica (Oxford, England)","url":"https://pubmed.ncbi.nlm.nih.gov/19796257","citation_count":44,"is_preprint":false},{"pmid":"27677334","id":"PMC_27677334","title":"Embryonic type Na+ channel β-subunit, SCN3B masks the disease phenotype of Brugada syndrome.","date":"2016","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/27677334","citation_count":37,"is_preprint":false},{"pmid":"31297029","id":"PMC_31297029","title":"Effects of GRM4, SCN2A and SCN3B polymorphisms on antiepileptic drugs responsiveness and epilepsy susceptibility.","date":"2019","source":"Saudi pharmaceutical journal : SPJ : the official publication of the Saudi Pharmaceutical Society","url":"https://pubmed.ncbi.nlm.nih.gov/31297029","citation_count":17,"is_preprint":false},{"pmid":"36362949","id":"PMC_36362949","title":"Two Novel Functional Mutations in Promoter Region of SCN3B Gene Associated with Atrial Fibrillation.","date":"2022","source":"Life (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/36362949","citation_count":6,"is_preprint":false},{"pmid":"35083300","id":"PMC_35083300","title":"miR-190a-5p Partially Represses the Abnormal Electrical Activity of SCN3B in Cardiac Arrhythmias by Downregulation of IL-2.","date":"2022","source":"Frontiers in cardiovascular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/35083300","citation_count":5,"is_preprint":false},{"pmid":"38769694","id":"PMC_38769694","title":"Enterotoxin-related genes PPFIA4 and SCN3B promote colorectal cancer development and progression.","date":"2024","source":"Journal of biochemical and molecular toxicology","url":"https://pubmed.ncbi.nlm.nih.gov/38769694","citation_count":3,"is_preprint":false},{"pmid":"20730464","id":"PMC_20730464","title":"Mutational analysis of SCN2B, SCN3B and SCN4B in a large Chinese Han family with generalized tonic-clonic seizure.","date":"2010","source":"Neurological sciences : official journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology","url":"https://pubmed.ncbi.nlm.nih.gov/20730464","citation_count":3,"is_preprint":false},{"pmid":"39761910","id":"PMC_39761910","title":"A novel SCN3B in-frame codon deletion in a Brugada syndrome patient: Implications for disrupted NaV1.5 function.","date":"2025","source":"Journal of molecular and cellular cardiology","url":"https://pubmed.ncbi.nlm.nih.gov/39761910","citation_count":2,"is_preprint":false},{"pmid":"38450374","id":"PMC_38450374","title":"Identification of a novel Scn3b mutation in a Chinese Brugada syndrome pedigree: implications for Nav1.5 electrophysiological properties and intracellular distribution of Nav1.5 and Navβ3.","date":"2024","source":"Frontiers in cardiovascular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/38450374","citation_count":1,"is_preprint":false},{"pmid":"40072811","id":"PMC_40072811","title":"SCN3B is an Anti-breast Cancer Molecule with Migration Inhibition Effect.","date":"2025","source":"Biochemical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/40072811","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11643,"output_tokens":3391,"usd":0.042897},"stage2":{"model":"claude-opus-4-6","input_tokens":6825,"output_tokens":2625,"usd":0.149625},"total_usd":0.192522,"stage1_batch_id":"msgbatch_011rkcQdVV1RaFq9XhcG6df6","stage2_batch_id":"msgbatch_01RzgrJafdF4EWHhj5mNi6dh","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2001,\n      \"finding\": \"SCN3B (β3 subunit) co-expressed with SCN5A (Nav1.5) in Xenopus oocytes produced a ~3-fold increase in functional sodium channel expression, a depolarizing shift in steady-state inactivation half-voltage, and faster recovery from inactivation compared to SCN5A alone; these effects were distinct from those of SCN1B, indicating SCN3B modulates Nav1.5 kinetics and membrane targeting.\",\n      \"method\": \"Xenopus oocyte co-expression, cell-attached macropatch recording, Northern/Western blot\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — functional reconstitution in oocytes with electrophysiology, replicated across multiple kinetic parameters\",\n      \"pmids\": [\"11744748\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"SCN3B is a p53-inducible gene: p53 directly binds two response elements (upstream of exon 1 and in intron 3) to drive SCN3B transcription; SCN3B protein localizes to the endoplasmic reticulum, and its overexpression induces apoptosis and suppresses colony formation, placing SCN3B in a p53-dependent apoptotic pathway.\",\n      \"method\": \"Chromatin immunoprecipitation, reporter gene assay, adenoviral overexpression, colony formation assay, immunofluorescence localization\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (ChIP, reporter assay, functional apoptosis assay, localization) in single study\",\n      \"pmids\": [\"15334053\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"The SCN3B loss-of-function mutation V54G reduces peak Nav1.5 sodium current and causes a positive shift in inactivation; co-immunoprecipitation showed Navβ3 physically associates with Nav1.5, and immunocytochemistry demonstrated that V54G dramatically reduces trafficking of Nav1.5 to the plasma membrane.\",\n      \"method\": \"Whole-cell patch clamp (HEK-293 and COS cells), co-immunoprecipitation, immunocytochemistry\",\n      \"journal\": \"Cardiovascular research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — reciprocal functional assay + Co-IP + localization, multiple cell systems\",\n      \"pmids\": [\"20042427\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Scn3b knockout mice show reduced peak Na+ current density, negative shift of inactivation in ventricular myocytes, shorter ventricular effective refractory periods, and inducible ventricular tachycardia in Langendorff-perfused hearts, establishing Scn3b as a regulator of ventricular sodium channel function and arrhythmia susceptibility in vivo.\",\n      \"method\": \"Scn3b−/− knockout mouse (homologous recombination), whole-cell patch clamp of isolated myocytes, Langendorff perfusion, programmed electrical stimulation, RT-PCR\",\n      \"journal\": \"Progress in biophysics and molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO mouse with cellular electrophysiology and intact-heart phenotype\",\n      \"pmids\": [\"19351516\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Scn3b knockout mice exhibit slower heart rates, longer P-wave durations, prolonged PR intervals, sinus node dysfunction, and atrial fibrillation induced by burst pacing, demonstrating Scn3b is required for normal sino-atrial and intra-cardiac conduction.\",\n      \"method\": \"Scn3b−/− knockout mouse, in vivo ECG, Langendorff perfusion with atrial electrogram recordings, burst pacing, immunofluorescence\",\n      \"journal\": \"Acta physiologica\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with multiple electrophysiological readouts and protein-level confirmation\",\n      \"pmids\": [\"19796257\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"SCN3B mutations R6K, L10P, and M161T identified in lone AF patients all cause loss-of-function reduction in sodium current when expressed in heterologous systems, supporting a mechanism whereby decreased Nav1.5 current enhances AF susceptibility.\",\n      \"method\": \"Whole-cell patch clamp in heterologous expression system, mutational analysis\",\n      \"journal\": \"Cardiovascular research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional electrophysiology on patient-derived mutations, single lab\",\n      \"pmids\": [\"21051419\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The SCN3B A130V mutation found in a lone AF patient dramatically reduces Nav1.5 sodium current density without affecting channel kinetics; when co-expressed with wild-type SCN3B, A130V negates WT function (dominant-negative mechanism); surface biotinylation showed A130V does not affect cell surface expression of Nav1.5 or SCN3B, suggesting it impairs ion conduction rather than trafficking.\",\n      \"method\": \"Whole-cell patch clamp (HEK293/Nav1.5 stable line), co-expression dominant-negative assay, surface biotinylation/Western blot\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods establishing dominant-negative mechanism and ruling out trafficking defect\",\n      \"pmids\": [\"20558140\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The SCN3B Val110Ile mutation associated with Brugada syndrome impairs cytoplasmic trafficking of Nav1.5, reduces its cell surface expression, and significantly decreases sodium current in transfected cells.\",\n      \"method\": \"Direct sequencing, whole-cell patch clamp, cell surface expression assay in transfected cells\",\n      \"journal\": \"Circulation journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional electrophysiology + surface expression, single lab\",\n      \"pmids\": [\"23257389\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"SCN3B is highly expressed in embryonic hearts and iPSC-derived cardiomyocytes; SCN3B augments INa of loss-of-function SCN5A E1784K mutant channels; knockdown of SCN3B in LQTS3/BrS iPSC-derived cardiomyocytes unmasks the Brugada syndrome electrophysiological phenotype, demonstrating that embryonic SCN3B expression masks BrS disease manifestation.\",\n      \"method\": \"iPSC-derived cardiomyocytes, siRNA knockdown, heterologous expression electrophysiology, patch clamp\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — iPSC disease model with genetic rescue/knockdown and heterologous functional validation\",\n      \"pmids\": [\"27677334\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"IL-2 upregulates SCN3B transcript and protein levels (via p53 induction) in cardiac cells and increases sodium current density; the effect on sodium current is independent of SCN3B alone, suggesting a broader regulatory network.\",\n      \"method\": \"qRT-PCR, Western blot, whole-cell patch clamp, SCN3B knockdown in HL-1 and HEK293 cells\",\n      \"journal\": \"BMC cardiovascular disorders\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — multiple methods but mechanistic independence of SCN3B from IL-2 Na+ current effect reduces clarity\",\n      \"pmids\": [\"26728597\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Two rare 5′UTR variants of SCN3B are associated with lone AF; the c.-324C>A variant increases SCN3B transcriptional activity, representing a gain-of-function regulatory mutation; GATA4 was identified as a transcriptional regulator of SCN3B that interacts with this variant to enhance SCN3B expression.\",\n      \"method\": \"Luciferase reporter assay, transcription factor binding analysis, patient sequencing\",\n      \"journal\": \"Life (Basel, Switzerland)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — reporter assay with GATA4 interaction, single lab\",\n      \"pmids\": [\"36362949\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"miR-190a-5p directly suppresses IL-2 expression (validated by luciferase reporter assay), thereby reducing IL-2-driven upregulation of SCN3B sodium current; miR-190a-5p inhibitor reverses this suppression, defining a miR-190a-5p/IL-2/SCN3B regulatory axis in cardiac arrhythmia.\",\n      \"method\": \"Luciferase reporter assay, qRT-PCR, whole-cell patch clamp, FISH\",\n      \"journal\": \"Frontiers in cardiovascular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — multiple methods establishing miRNA-target relationship and functional sodium current link\",\n      \"pmids\": [\"35083300\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The SCN3B in-frame deletion ΔT138 causes minimal gross structural perturbation (confirmed by circular dichroism and computational modeling) but reduces peak Nav1.5 current and channel availability and accelerates fast inactivation when both WT and ΔT138 β3 are co-expressed; surface biotinylation and co-immunoprecipitation showed normal β3 surface expression and intact interaction with Nav1.5.\",\n      \"method\": \"Site-directed mutagenesis, circular dichroism spectroscopy, whole-cell patch clamp, surface biotinylation, co-immunoprecipitation, surface cross-linking\",\n      \"journal\": \"Journal of molecular and cellular cardiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution with mutagenesis, structural analysis, and multiple functional assays in single study\",\n      \"pmids\": [\"39761910\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SCN3B P87I mutation reduces peak INa by ~60% and decreases plasma membrane localization of both SCN3B and Nav1.5 (SCN5A) as shown by confocal imaging and Western blot, with computational cardiac action potential simulations predicting altered endocardial/epicardial action potential morphology.\",\n      \"method\": \"Whole-cell patch clamp, confocal immunofluorescence, Western blot, computational action potential modeling\",\n      \"journal\": \"Frontiers in cardiovascular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — functional + localization data, single lab, no Co-IP\",\n      \"pmids\": [\"38450374\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Overexpression of SCN3B in breast cancer cell lines inhibits cell migration and invasion, and influences expression of >800 genes associated with cell migration and extracellular matrix interactions.\",\n      \"method\": \"Overexpression in breast cancer cell lines, migration/invasion assays, gene expression profiling\",\n      \"journal\": \"Biochemical genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, phenotypic assay without defined molecular mechanism\",\n      \"pmids\": [\"40072811\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SCN3B encodes the voltage-gated sodium channel β3 (Navβ3) auxiliary subunit that physically associates with the cardiac α-subunit Nav1.5 (SCN5A), promotes its trafficking to the plasma membrane, and modulates its kinetics (shifting steady-state inactivation and accelerating recovery from inactivation); loss-of-function SCN3B mutations reduce Nav1.5 surface expression and peak sodium current, causing arrhythmia syndromes including Brugada syndrome, idiopathic ventricular fibrillation, and atrial fibrillation, while SCN3B transcription is directly regulated by p53 (via intronic and upstream response elements) and by GATA4, and the protein also participates in a p53-dependent apoptotic pathway localized to the endoplasmic reticulum.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"SCN3B encodes the voltage-gated sodium channel β3 auxiliary subunit (Navβ3), which physically associates with the pore-forming α-subunit Nav1.5 (SCN5A) to promote its trafficking to the plasma membrane and modulate channel gating — increasing functional sodium channel expression, shifting steady-state inactivation, and accelerating recovery from inactivation [PMID:11744748, PMID:20042427]. Scn3b-knockout mice exhibit reduced ventricular sodium current density, sinus node dysfunction, conduction slowing, and inducible ventricular tachycardia and atrial fibrillation, establishing Navβ3 as essential for normal cardiac electrical function [PMID:19351516, PMID:19796257]. Loss-of-function SCN3B mutations cause Brugada syndrome, idiopathic ventricular fibrillation, and atrial fibrillation through reduced Nav1.5 current arising from impaired trafficking, altered gating, or dominant-negative suppression of channel conductance [PMID:20042427, PMID:20558140, PMID:23257389, PMID:21051419]. SCN3B transcription is directly activated by p53 via intronic and upstream response elements and by GATA4 at the 5′UTR, and SCN3B overexpression induces apoptosis, linking the gene to a p53-dependent cell-death pathway at the endoplasmic reticulum [PMID:15334053, PMID:36362949].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"The fundamental question of whether the β3 subunit modulates the cardiac sodium channel was answered: co-expression with Nav1.5 increased functional channel expression ~3-fold, shifted inactivation, and accelerated recovery, establishing SCN3B as a kinetic and trafficking modulator of Nav1.5.\",\n      \"evidence\": \"Xenopus oocyte co-expression with macropatch electrophysiology\",\n      \"pmids\": [\"11744748\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Physical interaction between β3 and Nav1.5 was not directly demonstrated\",\n        \"In vivo cardiac relevance not yet tested\",\n        \"Mechanism of increased functional expression (trafficking vs. gating) unresolved\"\n      ]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"The unexpected finding that p53 directly transactivates SCN3B and that SCN3B overexpression induces apoptosis placed the sodium channel subunit in a p53-dependent cell-death pathway at the endoplasmic reticulum, broadening its biology beyond ion conduction.\",\n      \"evidence\": \"ChIP for p53 binding, luciferase reporter assays, adenoviral overexpression with colony formation and apoptosis assays, immunofluorescence localization\",\n      \"pmids\": [\"15334053\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Downstream apoptotic mechanism (how ER-localized β3 triggers cell death) undefined\",\n        \"Relevance of the p53–SCN3B axis in cardiac tissue not explored\",\n        \"No confirmation that endogenous sodium currents mediate the apoptotic effect\"\n      ]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Loss of Scn3b in knockout mice demonstrated in vivo cardiac necessity: reduced sodium current, ventricular tachycardia susceptibility, sinus node dysfunction, and atrial fibrillation established Navβ3 as required for normal cardiac conduction and rhythm.\",\n      \"evidence\": \"Scn3b−/− knockout mice with whole-cell patch clamp of isolated myocytes, in vivo ECG, Langendorff perfusion with programmed electrical stimulation\",\n      \"pmids\": [\"19351516\", \"19796257\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether β3 loss alters expression/localization of other β subunits or compensatory channels not addressed\",\n        \"Mechanism linking reduced current to arrhythmia substrate (fibrosis, gap junctions) not defined\"\n      ]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"The first human disease-causing mutation (V54G) was shown to reduce Nav1.5 trafficking to the plasma membrane and decrease sodium current, establishing a direct physical association by co-immunoprecipitation and linking SCN3B loss-of-function to Brugada syndrome.\",\n      \"evidence\": \"Whole-cell patch clamp in HEK-293 and COS cells, co-immunoprecipitation, immunocytochemistry\",\n      \"pmids\": [\"20042427\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis for how V54G disrupts trafficking unknown\",\n        \"Whether V54G also affects interaction with other Nav α subunits not tested\"\n      ]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Multiple SCN3B mutations in atrial fibrillation patients revealed that β3 dysfunction can operate through at least two distinct mechanisms — impaired trafficking (most mutations) versus dominant-negative suppression of ion conduction without trafficking defect (A130V) — diversifying the pathophysiological repertoire.\",\n      \"evidence\": \"Whole-cell patch clamp, co-expression dominant-negative assay, surface biotinylation in HEK293 cells\",\n      \"pmids\": [\"21051419\", \"20558140\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis for dominant-negative mechanism of A130V unknown\",\n        \"Whether dominant-negative mutations affect other sodium channel isoforms untested\"\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"High SCN3B expression in embryonic/iPSC-derived cardiomyocytes was shown to mask the Brugada syndrome phenotype of SCN5A mutations, explaining why BrS manifests in adulthood when SCN3B expression declines, and an IL-2/p53 axis was identified that upregulates SCN3B transcription.\",\n      \"evidence\": \"iPSC-derived cardiomyocytes with siRNA knockdown and heterologous expression electrophysiology; qRT-PCR, Western blot, and patch clamp for IL-2 studies\",\n      \"pmids\": [\"27677334\", \"26728597\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Developmental regulation of SCN3B expression in human heart not mapped in vivo\",\n        \"IL-2 effect on sodium current was partly independent of SCN3B, suggesting additional mediators\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identification of GATA4 as a transcriptional regulator of SCN3B via the 5′UTR and a miR-190a-5p/IL-2/SCN3B regulatory axis extended the upstream control network governing SCN3B expression in the heart.\",\n      \"evidence\": \"Luciferase reporter assays, transcription factor binding analysis, qRT-PCR, whole-cell patch clamp\",\n      \"pmids\": [\"36362949\", \"35083300\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"GATA4 regulation not confirmed by ChIP in cardiac cells\",\n        \"Physiological relevance of miR-190a-5p axis in cardiac tissue in vivo not demonstrated\",\n        \"Interplay between GATA4 and p53 regulatory inputs uncharacterized\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Structural-functional dissection of the ΔT138 in-frame deletion showed that β3 mutations can alter Nav1.5 gating (reducing current and accelerating inactivation) without disrupting β3 structure, surface expression, or physical interaction with Nav1.5, defining a third loss-of-function mechanism — pure gating modulation.\",\n      \"evidence\": \"Site-directed mutagenesis, circular dichroism spectroscopy, whole-cell patch clamp, surface biotinylation, co-immunoprecipitation\",\n      \"pmids\": [\"39761910\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Atomic-resolution structure of β3–Nav1.5 complex not available\",\n        \"Whether ΔT138 mechanism applies in cardiomyocytes not tested\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the atomic structure of the β3–Nav1.5 interface, the mechanism by which ER-localized β3 induces p53-dependent apoptosis, and whether β3 modulates neuronal or other non-cardiac sodium channel isoforms in vivo.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No high-resolution structure of β3 alone or in complex with Nav1.5\",\n        \"Apoptotic mechanism downstream of β3 at the ER undefined\",\n        \"Role of β3 with non-cardiac Nav α-subunits not functionally characterized in native tissues\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2, 6, 12]},\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 3, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [2, 6, 7, 13]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 3, 8]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 3, 4]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [2, 7, 13]}\n    ],\n    \"complexes\": [\n      \"Voltage-gated sodium channel complex (Nav1.5/β3)\"\n    ],\n    \"partners\": [\n      \"SCN5A\",\n      \"GATA4\",\n      \"TP53\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}