{"gene":"KCNE5","run_date":"2026-04-28T18:06:54","timeline":{"discoveries":[{"year":2002,"finding":"KCNE5 coassembles with KCNQ1 and shifts its voltage activation curve by more than 140 mV in the positive direction, slows activation, and accelerates deactivation compared to KCNQ1+KCNE1; four residues in the transmembrane domain of KCNE5 are critical for this voltage-dependent modulation. KCNE5 is specific for KCNQ1 and does not affect other KCNQ family members or hERG1.","method":"Heterologous expression in Xenopus oocytes or mammalian cells, voltage-clamp electrophysiology, transmembrane domain mutagenesis","journal":"Biophysical journal","confidence":"High","confidence_rationale":"Tier 1 — in vitro electrophysiology with mutagenesis identifying specific transmembrane residues, moderate evidence","pmids":["12324418"],"is_preprint":false},{"year":2008,"finding":"Wild-type KCNE5 suppresses IKs (KCNQ1+KCNE1) current in a concentration-dependent manner; the AF-associated missense mutation L65F abolishes this suppression, resulting in a gain-of-function of IKs indistinguishable from current recorded without KCNE5.","method":"Transient transfection of CHO cells with KCNQ1+KCNE1±KCNE5 or KCNE5-L65F, whole-cell patch-clamp electrophysiology","journal":"Heart rhythm","confidence":"High","confidence_rationale":"Tier 1-2 — functional reconstitution with disease mutant comparison and concentration-dependence, moderate evidence","pmids":["18313602"],"is_preprint":false},{"year":2011,"finding":"KCNE5 variants Y81H and D92E;E93X produce gain-of-function effects on transient outward current (Ito) when coexpressed with KCND3 (Kv4.3), significantly increasing Ito, while producing no significant changes in KCNQ1-mediated current. These variants are linked to Brugada syndrome/IVF via augmented Ito.","method":"Cotransfection with KCND3 or KCNQ1, patch-clamp electrophysiology, action potential simulation modeling","journal":"Circulation. Arrhythmia and electrophysiology","confidence":"High","confidence_rationale":"Tier 1-2 — functional reconstitution with two different channel partners, disease variants tested, complemented by simulation","pmids":["21493962"],"is_preprint":false},{"year":2018,"finding":"Kcne5 knockout in mice increases ventricular KV current density through augmentation of IKslow,1 (KV1.5), Ito,f (KV4), and IKslow,2 (KV2.1). Kcne5 protein localizes to intercalated discs and colocalizes with KV2.1 predominantly in intracellular vesicles in cardiac and HEK293 cells, indicating that KCNE5 reduces IKslow,2 by promoting intracellular sequestration of KV2.1. The AF-associated L65F mutation negatively shifts KV2.1-KCNE5 voltage dependence and increases maximum current density >2-fold.","method":"Kcne5 knockout mice, intracardiac ECG, patch-clamp on isolated ventricular myocytes, immunofluorescence colocalization in HL-1 and HEK293 cells, heterologous expression of disease mutants","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 2 — in vivo KO model with defined electrophysiological phenotype, colocalization, and heterologous functional studies with disease mutants; multiple orthogonal methods in single study","pmids":["30289750"],"is_preprint":false},{"year":2012,"finding":"KCNE5 protein is expressed in first trimester human placenta and localizes mainly to the syncytiotrophoblast and mesenchyme, where it is co-expressed with KCNQ3, suggesting a KCNQ3/KCNE5 channel complex in placental tissue.","method":"qRT-PCR, immunohistochemistry on first trimester placental samples","journal":"Pregnancy hypertension","confidence":"Low","confidence_rationale":"Tier 3 — localization by IHC with no functional consequence directly demonstrated","pmids":["26105295"],"is_preprint":false}],"current_model":"KCNE5 is an X-linked ancillary β-subunit that associates with voltage-gated K+ channel α-subunits (KCNQ1, KV4.3/KCND3, KV2.1) to modulate their gating: it potently inhibits KCNQ1 by shifting its voltage activation threshold >140 mV rightward (requiring four transmembrane-domain residues), suppresses IKs in a concentration-dependent manner, inhibits KV2.1 by promoting its intracellular sequestration, and modulates KV4.3-mediated Ito; loss-of-function or gain-of-function mutations in KCNE5 dysregulate these currents and predispose to atrial fibrillation and Brugada syndrome."},"narrative":{"teleology":[{"year":2002,"claim":"Establishing that KCNE5 is a KCNQ1-specific modulatory subunit resolved the question of whether this orphan β-subunit had a defined channel partner and revealed an unusually large (~140 mV) positive shift in voltage activation as its primary inhibitory mechanism.","evidence":"Voltage-clamp electrophysiology in Xenopus oocytes and mammalian cells with transmembrane-domain mutagenesis","pmids":["12324418"],"confidence":"High","gaps":["Whether KCNE5 modulates channels beyond the KCNQ and hERG families was untested","Physiological relevance of the inhibition in native cardiomyocytes was not demonstrated","Stoichiometry of the KCNQ1–KCNE5 complex was not determined"]},{"year":2008,"claim":"Demonstrating that KCNE5 suppresses IKs in a concentration-dependent manner and that the AF-associated L65F mutation abolishes this suppression linked KCNE5 loss-of-function directly to a disease-relevant gain of IKs current.","evidence":"Whole-cell patch-clamp of CHO cells coexpressing KCNQ1/KCNE1 with wild-type or L65F KCNE5 at varying ratios","pmids":["18313602"],"confidence":"High","gaps":["Whether L65F affects KCNE5 trafficking or assembly rather than gating modulation was not resolved","No in vivo or native tissue confirmation of IKs augmentation by the L65F variant"]},{"year":2011,"claim":"Showing that KCNE5 variants Y81H and D92E;E93X selectively augment Kv4.3-mediated Ito without altering KCNQ1 current established KCNE5 as a multipartner β-subunit and connected gain-of-function Ito to Brugada syndrome pathogenesis.","evidence":"Patch-clamp electrophysiology of KCND3 or KCNQ1 coexpressed with mutant KCNE5, complemented by action-potential simulation","pmids":["21493962"],"confidence":"High","gaps":["Direct physical interaction between KCNE5 and Kv4.3 was not demonstrated by biochemical methods","Whether the Ito augmentation involves KChIP accessory subunits present in native cardiomyocytes was unknown"]},{"year":2018,"claim":"Kcne5 knockout mice revealed that KCNE5 tonically suppresses multiple ventricular Kv currents (IKslow,1, Ito,f, IKslow,2) in vivo, and that the mechanism for Kv2.1 inhibition involves promoting intracellular sequestration rather than solely altering gating.","evidence":"Kcne5-null mice with intracardiac ECG, patch-clamp on isolated ventricular myocytes, immunofluorescence colocalization in cardiac and HEK293 cells, and heterologous expression of L65F mutant with Kv2.1","pmids":["30289750"],"confidence":"High","gaps":["Atrial electrophysiology in the knockout was not characterized, leaving the AF-relevant substrate undefined","Molecular mechanism by which KCNE5 promotes Kv2.1 vesicular retention is unknown","Whether KCNE5 directly binds Kv1.5 or acts indirectly was not resolved"]},{"year":null,"claim":"The structural basis of KCNE5 interactions with its multiple Kv α-subunit partners, the stoichiometry of these complexes, and the precise trafficking mechanism by which KCNE5 retains Kv2.1 intracellularly remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of any KCNE5-containing channel complex exists","Subunit stoichiometry for KCNE5 with KCNQ1, Kv4.3, or Kv2.1 has not been determined","Atrial-specific roles of KCNE5 have not been tested in conditional knockout models"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,2,3]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,1,2,3]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,1,3]}],"complexes":[],"partners":["KCNQ1","KCNE1","KCND3","KCNV2"],"other_free_text":[]},"mechanistic_narrative":"KCNE5 is an X-linked auxiliary β-subunit of voltage-gated potassium channels that modulates cardiac repolarization by inhibiting multiple Kv α-subunits. It coassembles with KCNQ1 and shifts its voltage activation by >140 mV in the depolarizing direction through four critical transmembrane-domain residues, and it suppresses IKs (KCNQ1/KCNE1) current in a concentration-dependent manner [PMID:12324418, PMID:18313602]. KCNE5 also associates with Kv2.1, promoting its intracellular vesicular sequestration to reduce IKslow,2, and modulates Kv4.3-mediated Ito; Kcne5 knockout in mice increases ventricular Kv current density across multiple channel subtypes [PMID:30289750, PMID:21493962]. Loss-of-function mutations in KCNE5 (e.g., L65F) abolish IKs suppression and augment Kv2.1 current, predisposing to atrial fibrillation, while gain-of-function variants (Y81H, D92E;E93X) augment Ito and are linked to Brugada syndrome [PMID:18313602, PMID:21493962, PMID:30289750]."},"prefetch_data":{"uniprot":{"accession":"Q9UJ90","full_name":"Potassium voltage-gated channel subfamily E regulatory beta subunit 5","aliases":["AMME syndrome candidate gene 2 protein","Potassium channel subunit beta MiRP4","Potassium voltage-gated channel subfamily E member 1-like protein"],"length_aa":142,"mass_kda":15.0,"function":"Potassium channel ancillary subunit that is essential for generation of some native K(+) currents by virtue of formation of heteromeric ion channel complex with voltage-gated potassium (Kv) channel pore-forming alpha subunits. Functions as an inhibitory beta-subunit of the repolarizing cardiac potassium ion channel KCNQ1","subcellular_location":"Membrane","url":"https://www.uniprot.org/uniprotkb/Q9UJ90/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KCNE5","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/KCNE5","total_profiled":1310},"omim":[{"mim_id":"607554","title":"ATRIAL FIBRILLATION, FAMILIAL, 3; ATFB3","url":"https://www.omim.org/entry/607554"},{"mim_id":"607542","title":"POTASSIUM CHANNEL, VOLTAGE-GATED, KQT-LIKE SUBFAMILY, MEMBER 1; KCNQ1","url":"https://www.omim.org/entry/607542"},{"mim_id":"604433","title":"POTASSIUM CHANNEL, VOLTAGE-GATED, ISK-RELATED SUBFAMILY, MEMBER 3; KCNE3","url":"https://www.omim.org/entry/604433"},{"mim_id":"300328","title":"POTASSIUM CHANNEL, VOLTAGE-GATED, ISK-RELATED FAMILY, MEMBER 1-LIKE; KCNE1L","url":"https://www.omim.org/entry/300328"},{"mim_id":"300194","title":"AMME COMPLEX","url":"https://www.omim.org/entry/300194"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"brain","ntpm":16.6},{"tissue":"tongue","ntpm":4.5}],"url":"https://www.proteinatlas.org/search/KCNE5"},"hgnc":{"alias_symbol":[],"prev_symbol":["KCNE1L"]},"alphafold":{"accession":"Q9UJ90","domains":[{"cath_id":"1.20.5","chopping":"54-91","consensus_level":"medium","plddt":81.9232,"start":54,"end":91}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UJ90","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UJ90-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UJ90-F1-predicted_aligned_error_v6.png","plddt_mean":62.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KCNE5","jax_strain_url":"https://www.jax.org/strain/search?query=KCNE5"},"sequence":{"accession":"Q9UJ90","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UJ90.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UJ90/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UJ90"}},"corpus_meta":[{"pmid":"18313602","id":"PMC_18313602","title":"Gain of function in IKs secondary to a mutation in KCNE5 associated with atrial fibrillation.","date":"2008","source":"Heart rhythm","url":"https://pubmed.ncbi.nlm.nih.gov/18313602","citation_count":99,"is_preprint":false},{"pmid":"21493962","id":"PMC_21493962","title":"KCNE5 (KCNE1L) variants are novel modulators of Brugada syndrome and idiopathic ventricular fibrillation.","date":"2011","source":"Circulation. Arrhythmia and electrophysiology","url":"https://pubmed.ncbi.nlm.nih.gov/21493962","citation_count":94,"is_preprint":false},{"pmid":"12324418","id":"PMC_12324418","title":"KCNE5 induces time- and voltage-dependent modulation of the KCNQ1 current.","date":"2002","source":"Biophysical journal","url":"https://pubmed.ncbi.nlm.nih.gov/12324418","citation_count":94,"is_preprint":false},{"pmid":"16054468","id":"PMC_16054468","title":"Relation of 97T polymorphism in KCNE5 to risk of atrial fibrillation.","date":"2005","source":"The American journal of cardiology","url":"https://pubmed.ncbi.nlm.nih.gov/16054468","citation_count":53,"is_preprint":false},{"pmid":"27484720","id":"PMC_27484720","title":"KCNE4 and KCNE5: K(+) channel regulation and cardiac arrhythmogenesis.","date":"2016","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/27484720","citation_count":39,"is_preprint":false},{"pmid":"30289750","id":"PMC_30289750","title":"Deletion in mice of X-linked, Brugada syndrome- and atrial fibrillation-associated Kcne5 augments ventricular KV currents and predisposes to ventricular arrhythmia.","date":"2018","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/30289750","citation_count":25,"is_preprint":false},{"pmid":"21985337","id":"PMC_21985337","title":"KCNE5 polymorphism rs697829 is associated with QT interval and survival in acute coronary syndromes patients.","date":"2011","source":"Journal of cardiovascular electrophysiology","url":"https://pubmed.ncbi.nlm.nih.gov/21985337","citation_count":13,"is_preprint":false},{"pmid":"15193977","id":"PMC_15193977","title":"Does KCNE5 play a role in long QT syndrome?","date":"2004","source":"Clinica chimica acta; international journal of clinical chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15193977","citation_count":10,"is_preprint":false},{"pmid":"30129429","id":"PMC_30129429","title":"Case report of familial sudden cardiac death caused by a DSG2 p.F531C mutation as genetic background when carrying with heterozygous KCNE5 p.D92E/E93X mutation.","date":"2018","source":"BMC medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30129429","citation_count":8,"is_preprint":false},{"pmid":"26105295","id":"PMC_26105295","title":"OS081. Novel KCNQ3/KCNE5 isoform protein and mRNA expression in first trimester human placentae.","date":"2012","source":"Pregnancy hypertension","url":"https://pubmed.ncbi.nlm.nih.gov/26105295","citation_count":2,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7207,"output_tokens":1496,"usd":0.022031},"stage2":{"model":"claude-opus-4-6","input_tokens":4726,"output_tokens":3679,"usd":0.173407},"total_usd":0.195438,"stage1_batch_id":"msgbatch_01DzrsgVgYngY1hvM3DU1yF2","stage2_batch_id":"msgbatch_01KA9b7iRzKFdhoBUT7vCvSe","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2002,\n      \"finding\": \"KCNE5 coassembles with KCNQ1 and shifts its voltage activation curve by more than 140 mV in the positive direction, slows activation, and accelerates deactivation compared to KCNQ1+KCNE1; four residues in the transmembrane domain of KCNE5 are critical for this voltage-dependent modulation. KCNE5 is specific for KCNQ1 and does not affect other KCNQ family members or hERG1.\",\n      \"method\": \"Heterologous expression in Xenopus oocytes or mammalian cells, voltage-clamp electrophysiology, transmembrane domain mutagenesis\",\n      \"journal\": \"Biophysical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro electrophysiology with mutagenesis identifying specific transmembrane residues, moderate evidence\",\n      \"pmids\": [\"12324418\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Wild-type KCNE5 suppresses IKs (KCNQ1+KCNE1) current in a concentration-dependent manner; the AF-associated missense mutation L65F abolishes this suppression, resulting in a gain-of-function of IKs indistinguishable from current recorded without KCNE5.\",\n      \"method\": \"Transient transfection of CHO cells with KCNQ1+KCNE1±KCNE5 or KCNE5-L65F, whole-cell patch-clamp electrophysiology\",\n      \"journal\": \"Heart rhythm\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — functional reconstitution with disease mutant comparison and concentration-dependence, moderate evidence\",\n      \"pmids\": [\"18313602\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"KCNE5 variants Y81H and D92E;E93X produce gain-of-function effects on transient outward current (Ito) when coexpressed with KCND3 (Kv4.3), significantly increasing Ito, while producing no significant changes in KCNQ1-mediated current. These variants are linked to Brugada syndrome/IVF via augmented Ito.\",\n      \"method\": \"Cotransfection with KCND3 or KCNQ1, patch-clamp electrophysiology, action potential simulation modeling\",\n      \"journal\": \"Circulation. Arrhythmia and electrophysiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — functional reconstitution with two different channel partners, disease variants tested, complemented by simulation\",\n      \"pmids\": [\"21493962\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Kcne5 knockout in mice increases ventricular KV current density through augmentation of IKslow,1 (KV1.5), Ito,f (KV4), and IKslow,2 (KV2.1). Kcne5 protein localizes to intercalated discs and colocalizes with KV2.1 predominantly in intracellular vesicles in cardiac and HEK293 cells, indicating that KCNE5 reduces IKslow,2 by promoting intracellular sequestration of KV2.1. The AF-associated L65F mutation negatively shifts KV2.1-KCNE5 voltage dependence and increases maximum current density >2-fold.\",\n      \"method\": \"Kcne5 knockout mice, intracardiac ECG, patch-clamp on isolated ventricular myocytes, immunofluorescence colocalization in HL-1 and HEK293 cells, heterologous expression of disease mutants\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo KO model with defined electrophysiological phenotype, colocalization, and heterologous functional studies with disease mutants; multiple orthogonal methods in single study\",\n      \"pmids\": [\"30289750\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"KCNE5 protein is expressed in first trimester human placenta and localizes mainly to the syncytiotrophoblast and mesenchyme, where it is co-expressed with KCNQ3, suggesting a KCNQ3/KCNE5 channel complex in placental tissue.\",\n      \"method\": \"qRT-PCR, immunohistochemistry on first trimester placental samples\",\n      \"journal\": \"Pregnancy hypertension\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — localization by IHC with no functional consequence directly demonstrated\",\n      \"pmids\": [\"26105295\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KCNE5 is an X-linked ancillary β-subunit that associates with voltage-gated K+ channel α-subunits (KCNQ1, KV4.3/KCND3, KV2.1) to modulate their gating: it potently inhibits KCNQ1 by shifting its voltage activation threshold >140 mV rightward (requiring four transmembrane-domain residues), suppresses IKs in a concentration-dependent manner, inhibits KV2.1 by promoting its intracellular sequestration, and modulates KV4.3-mediated Ito; loss-of-function or gain-of-function mutations in KCNE5 dysregulate these currents and predispose to atrial fibrillation and Brugada syndrome.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"KCNE5 is an X-linked auxiliary β-subunit of voltage-gated potassium channels that modulates cardiac repolarization by inhibiting multiple Kv α-subunits. It coassembles with KCNQ1 and shifts its voltage activation by >140 mV in the depolarizing direction through four critical transmembrane-domain residues, and it suppresses IKs (KCNQ1/KCNE1) current in a concentration-dependent manner [PMID:12324418, PMID:18313602]. KCNE5 also associates with Kv2.1, promoting its intracellular vesicular sequestration to reduce IKslow,2, and modulates Kv4.3-mediated Ito; Kcne5 knockout in mice increases ventricular Kv current density across multiple channel subtypes [PMID:30289750, PMID:21493962]. Loss-of-function mutations in KCNE5 (e.g., L65F) abolish IKs suppression and augment Kv2.1 current, predisposing to atrial fibrillation, while gain-of-function variants (Y81H, D92E;E93X) augment Ito and are linked to Brugada syndrome [PMID:18313602, PMID:21493962, PMID:30289750].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Establishing that KCNE5 is a KCNQ1-specific modulatory subunit resolved the question of whether this orphan β-subunit had a defined channel partner and revealed an unusually large (~140 mV) positive shift in voltage activation as its primary inhibitory mechanism.\",\n      \"evidence\": \"Voltage-clamp electrophysiology in Xenopus oocytes and mammalian cells with transmembrane-domain mutagenesis\",\n      \"pmids\": [\"12324418\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether KCNE5 modulates channels beyond the KCNQ and hERG families was untested\",\n        \"Physiological relevance of the inhibition in native cardiomyocytes was not demonstrated\",\n        \"Stoichiometry of the KCNQ1–KCNE5 complex was not determined\"\n      ]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Demonstrating that KCNE5 suppresses IKs in a concentration-dependent manner and that the AF-associated L65F mutation abolishes this suppression linked KCNE5 loss-of-function directly to a disease-relevant gain of IKs current.\",\n      \"evidence\": \"Whole-cell patch-clamp of CHO cells coexpressing KCNQ1/KCNE1 with wild-type or L65F KCNE5 at varying ratios\",\n      \"pmids\": [\"18313602\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether L65F affects KCNE5 trafficking or assembly rather than gating modulation was not resolved\",\n        \"No in vivo or native tissue confirmation of IKs augmentation by the L65F variant\"\n      ]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showing that KCNE5 variants Y81H and D92E;E93X selectively augment Kv4.3-mediated Ito without altering KCNQ1 current established KCNE5 as a multipartner β-subunit and connected gain-of-function Ito to Brugada syndrome pathogenesis.\",\n      \"evidence\": \"Patch-clamp electrophysiology of KCND3 or KCNQ1 coexpressed with mutant KCNE5, complemented by action-potential simulation\",\n      \"pmids\": [\"21493962\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Direct physical interaction between KCNE5 and Kv4.3 was not demonstrated by biochemical methods\",\n        \"Whether the Ito augmentation involves KChIP accessory subunits present in native cardiomyocytes was unknown\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Kcne5 knockout mice revealed that KCNE5 tonically suppresses multiple ventricular Kv currents (IKslow,1, Ito,f, IKslow,2) in vivo, and that the mechanism for Kv2.1 inhibition involves promoting intracellular sequestration rather than solely altering gating.\",\n      \"evidence\": \"Kcne5-null mice with intracardiac ECG, patch-clamp on isolated ventricular myocytes, immunofluorescence colocalization in cardiac and HEK293 cells, and heterologous expression of L65F mutant with Kv2.1\",\n      \"pmids\": [\"30289750\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Atrial electrophysiology in the knockout was not characterized, leaving the AF-relevant substrate undefined\",\n        \"Molecular mechanism by which KCNE5 promotes Kv2.1 vesicular retention is unknown\",\n        \"Whether KCNE5 directly binds Kv1.5 or acts indirectly was not resolved\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The structural basis of KCNE5 interactions with its multiple Kv α-subunit partners, the stoichiometry of these complexes, and the precise trafficking mechanism by which KCNE5 retains Kv2.1 intracellularly remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No high-resolution structure of any KCNE5-containing channel complex exists\",\n        \"Subunit stoichiometry for KCNE5 with KCNQ1, Kv4.3, or Kv2.1 has not been determined\",\n        \"Atrial-specific roles of KCNE5 have not been tested in conditional knockout models\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 2, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 1, 2, 3]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 1, 3]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"KCNQ1\",\n      \"KCNE1\",\n      \"KCND3\",\n      \"KCNV2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\nWait, let me correct the partners. Looking at the timeline, KCNV2 is not mentioned. The partners mentioned are KCNQ1, KCNE1 (co-expressed in IKs studies), KCND3 (Kv4.3), and KV2.1 (KCNB1). Let me fix this.\n\n```json\n{\n  \"mechanistic_narrative\": \"KCNE5 is an X-linked auxiliary β-subunit of voltage-gated potassium channels that modulates cardiac repolarization by inhibiting multiple Kv α-subunits. It coassembles with KCNQ1 and shifts its voltage activation by >140 mV in the depolarizing direction through four critical transmembrane-domain residues, and it suppresses IKs (KCNQ1/KCNE1) current in a concentration-dependent manner [PMID:12324418, PMID:18313602]. KCNE5 also associates with Kv2.1, promoting its intracellular vesicular sequestration to reduce IKslow,2, and modulates Kv4.3-mediated Ito; Kcne5 knockout in mice increases ventricular Kv current density across multiple channel subtypes [PMID:30289750, PMID:21493962]. Loss-of-function mutations in KCNE5 (e.g., L65F) abolish IKs suppression and augment Kv2.1 current, predisposing to atrial fibrillation, while gain-of-function variants (Y81H, D92E;E93X) augment Ito and are linked to Brugada syndrome [PMID:18313602, PMID:21493962, PMID:30289750].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Establishing that KCNE5 is a KCNQ1-specific modulatory subunit resolved the question of whether this orphan β-subunit had a defined channel partner and revealed an unusually large (~140 mV) positive shift in voltage activation as its primary inhibitory mechanism.\",\n      \"evidence\": \"Voltage-clamp electrophysiology in Xenopus oocytes and mammalian cells with transmembrane-domain mutagenesis\",\n      \"pmids\": [\"12324418\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether KCNE5 modulates channels beyond the KCNQ and hERG families was untested\",\n        \"Physiological relevance of the inhibition in native cardiomyocytes was not demonstrated\",\n        \"Stoichiometry of the KCNQ1–KCNE5 complex was not determined\"\n      ]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Demonstrating that KCNE5 suppresses IKs in a concentration-dependent manner and that the AF-associated L65F mutation abolishes this suppression linked KCNE5 loss-of-function directly to a disease-relevant gain of IKs current.\",\n      \"evidence\": \"Whole-cell patch-clamp of CHO cells coexpressing KCNQ1/KCNE1 with wild-type or L65F KCNE5 at varying ratios\",\n      \"pmids\": [\"18313602\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether L65F affects KCNE5 trafficking or assembly rather than gating modulation was not resolved\",\n        \"No in vivo or native tissue confirmation of IKs augmentation by the L65F variant\"\n      ]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showing that KCNE5 variants Y81H and D92E;E93X selectively augment Kv4.3-mediated Ito without altering KCNQ1 current established KCNE5 as a multipartner β-subunit and connected gain-of-function Ito to Brugada syndrome pathogenesis.\",\n      \"evidence\": \"Patch-clamp electrophysiology of KCND3 or KCNQ1 coexpressed with mutant KCNE5, complemented by action-potential simulation\",\n      \"pmids\": [\"21493962\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Direct physical interaction between KCNE5 and Kv4.3 was not demonstrated by biochemical methods\",\n        \"Whether the Ito augmentation involves KChIP accessory subunits present in native cardiomyocytes was unknown\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Kcne5 knockout mice revealed that KCNE5 tonically suppresses multiple ventricular Kv currents (IKslow,1, Ito,f, IKslow,2) in vivo, and that the mechanism for Kv2.1 inhibition involves promoting intracellular sequestration rather than solely altering gating.\",\n      \"evidence\": \"Kcne5-null mice with intracardiac ECG, patch-clamp on isolated ventricular myocytes, immunofluorescence colocalization in cardiac and HEK293 cells, and heterologous expression of L65F mutant with Kv2.1\",\n      \"pmids\": [\"30289750\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Atrial electrophysiology in the knockout was not characterized, leaving the AF-relevant substrate undefined\",\n        \"Molecular mechanism by which KCNE5 promotes Kv2.1 vesicular retention is unknown\",\n        \"Whether KCNE5 directly binds Kv1.5 or acts indirectly was not resolved\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The structural basis of KCNE5 interactions with its multiple Kv α-subunit partners, the stoichiometry of these complexes, and the precise trafficking mechanism by which KCNE5 retains Kv2.1 intracellularly remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No high-resolution structure of any KCNE5-containing channel complex exists\",\n        \"Subunit stoichiometry for KCNE5 with KCNQ1, Kv4.3, or Kv2.1 has not been determined\",\n        \"Atrial-specific roles of KCNE5 have not been tested in conditional knockout models\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 2, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 1, 2, 3]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 1, 3]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"KCNQ1\",\n      \"KCND3\",\n      \"KCNB1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}