{"gene":"KCNE2","run_date":"2026-06-10T01:55:23","timeline":{"discoveries":[{"year":1999,"finding":"KCNE2 (MiRP1) assembles with HERG (KCNH2) to form IKr potassium channels. Co-expression of MiRP1 with HERG alters gating kinetics, unitary conductance, regulation by potassium, and biphasic inhibition by E-4031, making the complex resemble native cardiac IKr. Three KCNE2 missense mutations associated with LQT syndrome cause channels that open slowly and close rapidly, reducing potassium currents.","method":"Electrophysiology (whole-cell and single-channel patch clamp), heterologous expression in Xenopus oocytes and mammalian cells, functional characterization of LQT-associated mutants","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution of channel complex, functional characterization with multiple methods, widely replicated landmark paper","pmids":["10219239"],"is_preprint":false},{"year":2000,"finding":"KCNE2 (MiRP1) co-assembles with KCNQ2 and/or KCNQ3 (M-type channel subunits expressed in brain) and accelerates their deactivation kinetics. KCNE2 mRNA is expressed in brain regions that also express KCNQ2/KCNQ3.","method":"Co-immunoprecipitation, heterologous expression in COS cells, whole-cell electrophysiology","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP plus electrophysiology, single lab","pmids":["11034315"],"is_preprint":false},{"year":2001,"finding":"The cyclic nucleotide binding domain (CNBD) of HERG may be involved in its interaction with KCNE2: co-expression of KCNE2 with CNBD-mutant HERG conferred a partially dominant current suppression not seen with wild-type HERG alone, indicating KCNE2 plays a role in determining phenotypic severity of some LQT2 mutations.","method":"Site-directed mutagenesis of HERG CNBD, heterologous co-expression, whole-cell electrophysiology","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis plus functional electrophysiology, single lab","pmids":["11278781"],"is_preprint":false},{"year":2001,"finding":"KCNE2 co-expression with HERG alters both current kinetics and current density; incorporation of these effects into a quantitative action potential model showed that only changes in current density (not kinetics) significantly affect ventricular repolarization.","method":"Heterologous co-expression, whole-cell electrophysiology, computational action potential modeling","journal":"Circulation research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — electrophysiology with quantitative modeling, single lab","pmids":["11440975"],"is_preprint":false},{"year":2002,"finding":"A novel KCNE2 missense mutation V65M accelerates the inactivation time course of HERG/MiRP1 channels, thereby reducing IKr current density; mutant and wild-type MiRP1 co-localize with HERG subunits and form functional channels.","method":"Whole-cell patch clamp in CHO cells, single-strand conformation polymorphism analysis, direct sequencing, co-localization immunofluorescence","journal":"Journal of molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — electrophysiology plus co-localization, single lab","pmids":["12185453"],"is_preprint":false},{"year":2003,"finding":"KCNE2 co-expression with HCN4 in Xenopus oocytes and CHO cells enhances HCN4 current amplitudes, slows activation kinetics, and shifts half-maximal activation voltage to more negative potentials. The C-terminal tail of KCNE2 (but not other KCNE subunits) interacts with the C-terminal tail of HCN4 in yeast two-hybrid assays.","method":"Two-electrode voltage clamp (Xenopus oocytes), patch clamp (CHO cells), yeast two-hybrid protein interaction assay","journal":"Pflugers Archiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — electrophysiology in two expression systems plus yeast two-hybrid, single lab","pmids":["12856183"],"is_preprint":false},{"year":2003,"finding":"Wild-type MiRP1 modulates HERG channel gating (more negative steady-state activation, altered inactivation), and three LQT6-associated MiRP1 mutants (T8A, Q9E, M54T) further alter HERG gating in distinct ways. During premature action potential clamp protocols, T8A and Q9E mutants augment HERG currents in early diastole, a potentially pro-arrhythmic mechanism.","method":"Whole-cell patch clamp in CHO cells at 37°C, action potential clamp protocols","journal":"The Journal of physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — electrophysiology with multiple mutants and physiological AP clamp, single lab","pmids":["12923204"],"is_preprint":false},{"year":2004,"finding":"KCNE2 (MiRP1) co-assembles with HCN2 in neonatal rat ventricular myocytes, as demonstrated by co-immunoprecipitation of both expressed and endogenous subunits. Co-expression of MiRP1 with HCN2 produces a 4-fold increase in pacemaker current maximal conductance and alters activation/deactivation kinetics at physiologically relevant voltages.","method":"Adenoviral overexpression in neonatal rat ventricular myocytes, co-immunoprecipitation (expressed and endogenous proteins), whole-cell patch clamp","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP of both exogenous and endogenous proteins in native cardiac cells, plus functional electrophysiology","pmids":["15292247"],"is_preprint":false},{"year":2004,"finding":"KCNE2 and KCNQ1 form a heteromeric K+ channel in the luminal membrane of gastric parietal cells. The KCNE2/KCNQ1 channel is activated by acidic pH, PIP2, cAMP, and purinergic receptor stimulation. KCNQ1 distribution in parietal cells does not substantially change during stimulation-induced H+,K+-ATPase trafficking.","method":"In situ hybridization, immunofluorescence, confocal microscopy in parietal cells and COS cells, patch clamp electrophysiology","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (imaging, electrophysiology, pharmacology) confirming luminal localization and function","pmids":["15579540"],"is_preprint":false},{"year":2004,"finding":"KCNE2 R27C is a gain-of-function mutation affecting the KCNQ1-KCNE2 channel (responsible for a background potassium current) and is associated with familial atrial fibrillation. Unlike LQT-associated KCNE2 mutations, R27C does not alter HERG-KCNE2 current or HCN channel currents.","method":"Gene sequencing in AF kindreds, heterologous expression in Xenopus oocytes/mammalian cells, whole-cell electrophysiology","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional electrophysiology with multiple channel partners tested, single lab","pmids":["15368194"],"is_preprint":false},{"year":2006,"finding":"KCNE2 is essential for gastric acid secretion in vivo. Kcne2−/− mice have severe achlorhydria, abnormal parietal cell morphology, hypergastrinemia, and gastric glandular hyperplasia. KCNQ1 exhibited abnormal distribution in gastric glands from Kcne2−/− mice. Kcne2+/− mice showed reduced proton secretion (gene-dose effect), demonstrating that KCNE2 is required for normal gastric acid secretion.","method":"Targeted murine kcne2 gene disruption (knockout), gastric acid secretion measurement, histology, immunohistochemistry, Western blotting","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined cellular and physiological phenotype including gene-dose effect, multiple orthogonal readouts","pmids":["16754665"],"is_preprint":false},{"year":2006,"finding":"KCNE2 is co-localized with KCNQ1 and KCNE1 at the surface membrane and t-tubules of adult rat ventricular myocytes. Co-immunoprecipitation shows KCNQ1, KCNE1, and KCNE2 can form a tripartite complex. KCNE2 co-expression with KCNQ1 and KCNE1 decreases IKs current amplitude without altering its slow gating kinetics.","method":"Immunocytochemistry, co-immunoprecipitation in cardiomyocytes, patch clamp in oocytes and COS-7 cells","journal":"Heart rhythm","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP plus electrophysiology in native myocytes, single lab","pmids":["17161791"],"is_preprint":false},{"year":2006,"finding":"KCNE2 modulates Kv4.3 (the major alpha subunit of cardiac Ito): co-expression in COS-7 cells reduces peak current density, slows inactivation kinetics, causes a positive shift of steady-state inactivation, and accelerates recovery from inactivation.","method":"Whole-cell patch clamp in COS-7 cells after transfection","journal":"Journal of Southern Medical University","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single electrophysiology method, no co-IP or structural data","pmids":["17259113"],"is_preprint":false},{"year":2007,"finding":"KCNE2 has differential association with HERG compared to KCNE1: when forward trafficking is blocked (by Brefeldin A or ER-retention signals), KCNE2 abundance and association with HERG increase, while KCNE1 is preferentially retained in the ER. A significant fraction of KCNE2 is found extracellularly (soluble and vesicle-associated). HERG co-localizes more completely with KCNE1 at all membrane compartments.","method":"Co-immunoprecipitation, confocal immunofluorescence, surface labeling, Brefeldin A trafficking block, ER-retention signal engineering","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal biochemical and imaging methods, single lab","pmids":["17895974"],"is_preprint":false},{"year":2007,"finding":"A T10M mutation in MiRP1 (KCNE2) causes ≤80% reduction in hERG tail current, left-shifted steady-state inactivation, and 50% slower recovery from inactivation, providing a mechanism for reduced-penetrance inherited arrhythmia exacerbated by superimposed electrolyte disturbances.","method":"Whole-cell voltage clamp in transfected CHO cells","journal":"Cardiovascular research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — electrophysiology with multiple gating parameters measured, single lab","pmids":["18006462"],"is_preprint":false},{"year":2008,"finding":"The secondary structure of MiRP1 (KCNE2) was characterized: the N-terminal extracellular domain is predominantly non-ordered in aqueous media but alpha-helical in lipid micelles; the transmembrane domain is predominantly alpha-helix/non-ordered; the C-terminal domain is predominantly alpha-helical when incorporated into lipid bilayers. Full-length MiRP1 contains ~34% alpha-helix, 23% beta-strand, and 43% non-ordered structure.","method":"FTIR and CD spectroscopy of synthetic MiRP1 peptides in various detergent/lipid environments","journal":"Protein and peptide letters","confidence":"Low","confidence_rationale":"Tier 1 / Weak — structural spectroscopy of synthetic peptides, not native protein; single lab, no functional validation","pmids":["18221016"],"is_preprint":false},{"year":2008,"finding":"KCNE2 (MiRP1) modulates Kv4.3 Ito current when co-expressed as part of the Kv4.3/KChIP2/MiRP1 complex: it slows activation and inactivation kinetics and produces an 'overshoot' during recovery from inactivation. Co-expression of both KChIP2c and KCNE2 with Kv4.2 yields a current profile more similar to native cardiac Ito than either beta subunit alone.","method":"Whole-cell patch clamp in CHO cells stably expressing Kv4.3/KChIP2 or COS-7 cells transfected with Kv4.2/KChIP2c/KCNE2","journal":"Acta pharmacologica Sinica / British journal of pharmacology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — electrophysiology only, no co-IP or structural confirmation, single lab","pmids":["18501111","18536731"],"is_preprint":false},{"year":2008,"finding":"Targeted disruption of murine kcne2 prolonged ventricular action potential duration and reduced IK,slow1 by 50% (generated by Kv1.5, a novel in vivo partner for MiRP1) and Ito,f by ~25% (generated by Kv4 alpha subunits). Ventricular MiRP1 protein co-immunoprecipitated with native Kv1.5 and Kv4.2 but not Kv1.4 or Kv4.3. Kcne2 deletion also reduced mature Kv1.5 protein levels by 50% and disrupted Kv1.5 trafficking to intercalated discs.","method":"Targeted murine kcne2 gene disruption, whole-cell patch clamp in isolated ventricular myocytes, co-immunoprecipitation from native tissue, Western blotting, immunohistochemistry, in vivo QTc measurement","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO, co-IP from native tissue, multiple orthogonal methods, defined cellular/physiological phenotype","pmids":["18603586"],"is_preprint":false},{"year":2009,"finding":"KCNE2 modulates all four cardiac HCN isoforms: co-expression increases current densities of HCN1, HCN2, and HCN4, accelerates activation kinetics, and increases single-channel amplitude and conductance. KCNE2 also increases HCN2 and HCN4 membrane protein expression (2.2-fold and 1.6-fold, respectively). These effects demonstrate direct functional interaction at the single-channel level.","method":"Whole-cell patch clamp and single-channel recordings in CHO cells, Western blotting of membrane fractions","journal":"American journal of physiology. Heart and circulatory physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — whole-cell and single-channel electrophysiology plus protein expression analysis, single lab","pmids":["19429827"],"is_preprint":false},{"year":2009,"finding":"KCNE2 forms native cardiac complexes with Kv2.1, as shown by co-immunoprecipitation from rat heart tissue. KCNE2 (MiRP1) co-expression reduces Kv2.1 current density 2-fold and slows activation and deactivation kinetics. LQT-associated KCNE2 mutations M54T and I57T greatly alter Kv2.1 activation kinetics.","method":"Co-immunoprecipitation from rat heart tissue, whole-cell patch clamp in CHO cells","journal":"The Journal of membrane biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP from native tissue plus functional electrophysiology, single lab","pmids":["19219384"],"is_preprint":false},{"year":2009,"finding":"KCNE2 can substitute for KCNE1 in the KCNQ1-KCNE1 (IKs) channel complex due to dynamic KCNE1 turnover. KCNE2 independently traffics to the cell surface without requiring KCNQ1 co-assembly. In guinea pig ventricular myocytes, adenovirus-mediated KCNE2 expression co-localizes with native KCNQ1 and reduces native IKs current density.","method":"Pulse-chase experiments in COS-7 cells, biotinylation assays, vesicle injection in Xenopus oocytes, adenoviral gene delivery in adult cardiomyocytes, electrophysiology","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal approaches (pulse-chase, biotinylation, electrophysiology in native myocytes), single lab","pmids":["19372218"],"is_preprint":false},{"year":2009,"finding":"LQT6 KCNE2 M54T mutation modulates Kv4.3 (Ito alpha subunit): M54T and I57T variants significantly increase Ito current density, slow inactivation, and accelerate recovery from inactivation compared to wild-type KCNE2, suggesting a gain-of-function for Ito that may contribute to arrhythmogenesis.","method":"Whole-cell patch clamp in heterologous cell line co-expressing Kv4.3 and wild-type or mutant KCNE2","journal":"Heart rhythm","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — electrophysiology with multiple mutants, single lab; mechanistically distinct finding from same mutations studied elsewhere","pmids":["20042375"],"is_preprint":false},{"year":2010,"finding":"Solution NMR backbone assignments of human MiRP1 (KCNE2) were achieved in LMPG detergent micelles. CD spectroscopy revealed high alpha-helical content. Secondary structure analysis based on backbone chemical shifts showed multiple alpha-helical stretches along the primary sequence.","method":"Solution NMR (triple resonance backbone assignment), circular dichroism spectroscopy, protein expression and purification in E. coli","journal":"Protein expression and purification","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — NMR backbone assignment is rigorous structural method, but no functional validation in this study; single lab","pmids":["21087668"],"is_preprint":false},{"year":2011,"finding":"KCNE2 (along with KCNE1) retains homomeric N-type inactivating Kv alpha subunits (Kv1.4, Kv3.4) intracellularly early in the secretory pathway, suppressing their surface expression. This retention requires alpha-beta co-assembly, does not involve dynamin-dependent endocytosis, and acts as a checkpoint governing Kv channel alpha-subunit composition.","method":"Electrophysiology, co-immunoprecipitation, immunofluorescence, Brefeldin A treatment, dynamin inhibitor studies in mammalian cells","journal":"Biophysical journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (electrophysiology, biochemistry, imaging, pharmacological dissection), single lab but rigorous","pmids":["21943416","21943417"],"is_preprint":false},{"year":2011,"finding":"In the choroid plexus epithelium (CPe), KCNE2 is enriched in the apical membrane where it co-localizes with KCNQ1 and KCNA3. Kcne2 deletion increases CPe outward K+ current 2-fold, alters KCNQ1 and KCNA3 trafficking polarity, hyperpolarizes the CPe membrane by 9 mV, and increases CSF [Cl−] by 14%.","method":"Immunofluorescence with Kcne2−/− negative control, whole-cell patch clamp in CPe cells, pharmacological dissection (XE991, margatoxin, dendrotoxin), ion concentration measurements","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined cellular and CSF phenotype, multiple orthogonal methods","pmids":["21859894"],"is_preprint":false},{"year":2011,"finding":"KCNE2 S98 phosphorylation modulates hERG/IKr amplitude by accelerating hERG protein degradation and reducing cell-surface hERG protein levels. S98 dephosphorylation leads to increased hERG/IKr amplitude. KCNE2 protein is more abundant in ventricles than atria in human and animal hearts.","method":"Adenovirus-mediated genetic manipulation in adult cardiac myocytes, phospho-specific antibody (Ab2), Western blotting, immunofluorescence","journal":"American journal of physiology. Heart and circulatory physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phospho-specific antibody with adenoviral manipulation revealing novel PTM-dependent mechanism, single lab","pmids":["22180649"],"is_preprint":false},{"year":2012,"finding":"KCNQ1-KCNE2 is required for adequate thyroid iodide (I−) uptake. Pharmacological blockade of KCNQ1 impairs thyroid I− uptake in vivo and in vitro. Kcne2 deletion doubles the rate of free I− efflux from the thyroid following ClO4− injection but does not affect Duox/TPO-mediated I− organification.","method":"Dynamic positron emission tomography in vivo, in vitro I− uptake assays, Kcne2 knockout mice, pharmacological inhibition with chromanol 293B","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo PET combined with in vitro assays and genetic KO, multiple orthogonal methods defining the mechanistic step","pmids":["22549510"],"is_preprint":false},{"year":2012,"finding":"Kcne2 gene deletion impairs HCN channel function in thalamocortical neurons: it shifts the voltage-dependence of Ih activation to more hyperpolarized potentials, slows gating kinetics, decreases Ih density, and increases input resistance and burst firing. Whole-brain HCN1 and HCN2 (but not HCN4) expression is reduced. Co-immunoprecipitation from whole-brain lysates did not detect KCNE2 interaction with HCN1 or HCN2.","method":"Kcne2 knockout mice, whole-cell patch clamp in brain slices (VB thalamic and cortical layer 6 neurons), Western blotting, co-immunoprecipitation","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO with defined neuronal phenotype; co-IP was negative, suggesting indirect mechanism in this tissue","pmids":["22880098"],"is_preprint":false},{"year":2013,"finding":"An LQT6 M54T MiRP1 mutation decreases HCN4 current density by 80% and slows HCN4 activation at physiologically relevant voltages in ventricular myocytes, causing sinus bradycardia through effects on pacemaker If. M54T effects on HCN4 are additive with its effects on hERG kinetics.","method":"Whole-cell patch clamp in neonatal rat ventricular myocytes transfected with human HCN4 or HCN2 ± wild-type or M54T MiRP1, computational simulation","journal":"Journal of cardiovascular electrophysiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — electrophysiology in native myocyte background with computational modeling, single lab","pmids":["23631727"],"is_preprint":false},{"year":2014,"finding":"KCNQ1, KCNE2, and Na+-coupled solute transporters (SMIT1, SGLT1) form reciprocally regulating complexes. KCNE2 and KCNQ1 co-localize and co-immunoprecipitate with SMIT1 in choroid plexus epithelium. The constitutively active KCNQ1-KCNE2 heteromeric channel inhibits myo-inositol transport by SMIT1. Kcne2−/− mice show reduced myo-inositol in CSF and increased seizure susceptibility corrected by myo-inositol injections.","method":"Co-immunoprecipitation from choroid plexus, heterologous co-expression with myo-inositol uptake assays, global metabolite profiling (Kcne2−/− mice), behavioral assays","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 2 / Strong — co-IP from native tissue, functional transport assays, in vivo metabolomics, and rescue experiments; multiple orthogonal methods","pmids":["24595108"],"is_preprint":false},{"year":2014,"finding":"KCNE2 physically interacts with Cav1.2 (L-type Ca2+ channel alpha subunit) and modulates L-type Ca2+ current (ICa,L): KCNE2 overexpression decreases ICa,L amplitude and alters its voltage-dependence and inactivation kinetics; knockdown has opposite effects. Deletion of the N-terminal inhibitory module (NTI) of Cav1.2 abolishes KCNE2 regulation. The AF-associated R27C mutation enhances KCNE2 suppression of ICa,L.","method":"Co-immunoprecipitation and co-localization in cardiomyocytes and HEK293 cells, whole-cell patch clamp, adenoviral overexpression and RNA interference","journal":"Journal of molecular and cellular cardiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus electrophysiology in native cardiomyocytes with domain deletion mutagenesis, single lab","pmids":["24681347"],"is_preprint":false},{"year":2014,"finding":"KCNE2 transmembrane domain residue Ile64 interacts with KCNQ1 residues Phe340 and Phe275 (different interaction mode from KCNE1). KCNE2 N-terminus decreases surface expression and activity of KCNQ1; KCNE2 C-terminus has minimal influence on KCNQ1 gating (unlike KCNE1 C-terminus).","method":"Electrophysiology, immunofluorescence, solution NMR and backbone flexibility analysis of transmembrane domains","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — NMR structural analysis plus electrophysiology; interaction residues identified, single lab","pmids":["24827085"],"is_preprint":false},{"year":2016,"finding":"Filamin C (FLNC) interacts with the C-terminal domain of KCNE2 specifically under hypoxic conditions (not normoxia), as demonstrated by yeast two-hybrid screening and co-immunoprecipitation/co-localization.","method":"Yeast two-hybrid screening of cardiac cDNA library, co-localization and co-immunoprecipitation under normoxic and hypoxic conditions","journal":"Cardiovascular journal of Africa","confidence":"Low","confidence_rationale":"Tier 3 / Weak — co-IP/co-localization, single lab, no functional electrophysiology readout","pmids":["26956495"],"is_preprint":false},{"year":2016,"finding":"Kcne2 deletion attenuates acute myocardial infarction: Kcne2−/− mice show 40% lower infarct size and decreased apoptosis after ischemia/reperfusion injury. This is mechanistically linked to 2-fold increased GSK-3β phosphorylation (inactivation) in Kcne2−/− mice; GSK-3β inhibitor mimicked and did not further enhance cardioprotection in Kcne2−/−mice.","method":"Coronary ligation IRI model, infarct size quantification, Western blotting for GSK-3β phosphorylation, pharmacological GSK-3β inhibition (SB216763), Millar catheter cardiac function","journal":"Cardiovascular research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological epistasis plus genetic KO with mechanistic biochemical readout, single lab","pmids":["26952045"],"is_preprint":false},{"year":2017,"finding":"Kcne2 deletion in mice impairs pancreatic β-cell insulin secretion up to 8-fold and diminishes β-cell peak outward K+ current, causing type 2 diabetes. Skeletal muscle insulin receptor β and insulin receptor substrate 1 are down-regulated 2-fold by Kcne2 deletion.","method":"Kcne2 knockout mice, glucose tolerance testing, in vitro insulin secretion assay, whole-cell patch clamp in pancreatic β-cells, Western blotting","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined cellular electrophysiology phenotype and functional secretion defect, multiple orthogonal methods","pmids":["28280005"],"is_preprint":false},{"year":2017,"finding":"Decreased cardiac KCNE2 expression contributes to pathological hypertrophy via activation of calcineurin-NFAT and MAPK pathways, mediated through enhanced L-type Ca2+ channel activity (increased intracellular Ca2+ transient). KCNE2 knockdown increased calcineurin activity and nuclear NFAT levels; inhibitors of L-type Ca2+ channel (nifedipine) or calcineurin (FK506) attenuated hypertrophy. KCNE2 overexpression by ultrasound-microbubble gene transfer suppressed TAC-induced hypertrophy in vivo.","method":"Adenoviral knockdown and overexpression in neonatal rat ventricular myocytes, TAC mouse model, pharmacological inhibition, calcineurin activity assay, Western blotting, ultrasound-microbubble gene delivery","journal":"Circulation. Heart failure","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — bidirectional manipulation with multiple pathway readouts and in vivo validation, single lab","pmids":["28611128"],"is_preprint":false},{"year":2019,"finding":"The stoichiometry of KCNE2 subunits in complex with HCN channel pore-forming subunits differs by HCN isoform and is concentration-dependent. Disease-linked KCNE2 gene variants can alter this stoichiometry with functional implications.","method":"Single-molecule subunit counting (fluorescence) in heterologous expression","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — single-molecule counting is quantitative, but single lab and stoichiometry not independently validated","pmids":["31235733"],"is_preprint":false},{"year":2019,"finding":"A conserved arginine/lysine-based motif (KSKR) in the KCNE2 proximal C-terminus is required for ER export of KCNE2 and its forward trafficking to the cell surface. This trafficking is essential for KCNE2-mediated suppression of KCNQ1 cell surface expression and current. The KCNE2 C-terminus does not appear to physically interact with KCNQ1 (C-terminus truncation did not reduce KCNE2-KCNQ1 apparent affinity), unlike KCNE1.","method":"Site-directed mutagenesis of the motif, biotinylation assays of surface expression, whole-cell electrophysiology in HEK293 cells","journal":"Channels","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis plus biochemical and electrophysiological validation, single lab","pmids":["31679457"],"is_preprint":false},{"year":2019,"finding":"Kcne2 deletion reduces pulmonary expression of Kcnq1 and Kcnb1. Kcne2 co-immunoprecipitates with Kcnq1 in mouse lungs, indicating pulmonary Kcnq1-Kcne2 channel complexes. Kcne2 deletion impairs gas exchange (reduced blood O2, increased CO2) and increases pulmonary inflammation and vascular leakage.","method":"Co-immunoprecipitation from lung tissue, Western blotting, blood gas analysis, bronchoalveolar lavage, Kcne2 knockout mice","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP from native tissue plus KO phenotype, single lab","pmids":["31162977"],"is_preprint":false},{"year":2020,"finding":"Cardiac-specific Kcne2 deletion (Kcne2CS−/−) causes dilated cardiomyopathy and terminal heart failure (median survival 28 weeks). Global Kcne2 deletion reduces gut Bacteroidales species (through achlorhydria), which correlates with improved survival. Proton-pump inhibitor omeprazole similarly altered the microbiome and delayed heart failure in Kcne2CS−/− mice, extending survival 10-fold at 44 weeks.","method":"Cardiac-specific vs global Kcne2 knockout mice, cardiac histology, microbiome profiling, pharmacological PPI treatment, survival analysis","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cardiac-specific KO with defined cardiomyopathy phenotype and pharmacological rescue via microbiome modulation, single lab","pmids":["32584506"],"is_preprint":false},{"year":2021,"finding":"Testin (encoded by TES, a focal adhesion protein) interacts with the KCNE2 intracellular C-terminal domain, identified by yeast two-hybrid screening and confirmed by co-immunoprecipitation. Testin nullifies KCNE2 effects on Kv1.5 voltage dependence and activation kinetics without affecting KCNE2 regulation of KCNQ1.","method":"Yeast two-hybrid screening, co-immunoprecipitation in vitro, whole-cell patch clamp in CHO cells","journal":"Channels","confidence":"Low","confidence_rationale":"Tier 3 / Weak — co-IP plus electrophysiology, single lab, in vitro system only","pmids":["33464998"],"is_preprint":false},{"year":2022,"finding":"KCNQ1 gain-of-function mutations (R116L, V185M, P369L) that cause gingival fibromatosis/pituitary hormone deficiency act by impairing Ca2+ sensitivity of the KCNQ1-KCNE2 channel complex; normally, KCNE2 limits resting Q1E2 conductance by requiring calcified calmodulin for effective channel opening.","method":"Whole-cell patch clamp with intracellular Ca2+ manipulation, calmodulin co-expression, KCNQ1 mutagenesis in heterologous cells","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — patch clamp with defined ionic/Ca2+ manipulations and mutagenesis, single lab; defines mechanism for Q1E2 complex regulation by Ca2+/calmodulin","pmids":["36077086"],"is_preprint":false}],"current_model":"KCNE2 (MiRP1) is a single-transmembrane β subunit that promiscuously co-assembles with multiple voltage-gated cation channel α subunits—including HERG/KCNH2, KCNQ1, HCN1-4, Kv1.5, Kv2.1, Kv4.2/4.3, KCNQ2/3, and Cav1.2—to modulate their gating kinetics, current density, protein trafficking, and surface expression; in native tissues KCNE2 is essential for gastric acid secretion (via apical KCNQ1-KCNE2 in parietal cells), thyroid iodide uptake, CSF homeostasis (via KCNQ1/KCNA3 regulation in choroid plexus), cardiac ventricular repolarization, pancreatic β-cell insulin secretion, and lung function, with S98 phosphorylation providing an additional post-translational mechanism that accelerates hERG protein degradation to reduce IKr amplitude."},"narrative":{"mechanistic_narrative":"KCNE2 (MiRP1) is a single-transmembrane ancillary β subunit that promiscuously co-assembles with diverse voltage-gated cation channel α subunits to tune their gating, conductance, surface trafficking, and current density across cardiac, epithelial, neuronal, and endocrine tissues [PMID:10219239, PMID:18603586]. Its founding role is in cardiac repolarization, where co-assembly with HERG (KCNH2) reconstitutes native-like IKr and where multiple missense mutations (e.g. V65M, T10M, M54T) reduce IKr by accelerating inactivation or altering gating, defining the long-QT (LQT6) phenotype [PMID:10219239, PMID:12185453, PMID:18006462], while the gain-of-function R27C variant acts through the KCNQ1-KCNE2 background current to cause familial atrial fibrillation [PMID:15368194]. Beyond hERG, KCNE2 modulates an unusually broad partner set—HCN1-4 pacemaker channels [PMID:15292247, PMID:19429827, PMID:23631727], KCNQ1 (alone and within tripartite KCNQ1-KCNE1 IKs complexes) [PMID:15579540, PMID:17161791], Kv1.5, Kv2.1, and Kv4 family channels [PMID:18603586, PMID:19219384], and the L-type Ca2+ channel Cav1.2 [PMID:24681347]—through direct physical interaction at defined transmembrane and C-terminal contacts [PMID:12856183, PMID:24827085]. A major function is regulation of channel biogenesis and surface delivery: KCNE2 retains N-type-inactivating Kv α subunits in the early secretory pathway as a composition checkpoint [PMID:21943416, PMID:21943417], requires a C-terminal KSKR motif for its own ER export [PMID:31679457], and suppresses KCNQ1 surface expression, with S98 phosphorylation accelerating hERG degradation as a post-translational brake on IKr [PMID:22180649]. In native epithelia, the apical KCNQ1-KCNE2 channel is essential for gastric acid secretion in parietal cells [PMID:15579540, PMID:16754665], thyroid iodide uptake [PMID:22549510], and choroid plexus K+/Cl−/myo-inositol homeostasis via co-regulation with KCNA3 and the solute transporter SMIT1 [PMID:21859894, PMID:24595108]; mouse Kcne2 loss further impairs pancreatic β-cell insulin secretion to cause type 2 diabetes [PMID:28280005] and disrupts pulmonary gas exchange [PMID:31162977]. Cardiac-specific Kcne2 deletion produces dilated cardiomyopathy and heart failure [PMID:32584506], and reduced cardiac KCNE2 drives pathological hypertrophy through enhanced Cav1.2-mediated Ca2+ entry and calcineurin-NFAT signaling [PMID:28611128].","teleology":[{"year":1999,"claim":"Established KCNE2's founding function—that a small accessory subunit converts HERG into native-like cardiac IKr and that its mutations cause long-QT syndrome—answering what MiRP1 contributes to a physiological current.","evidence":"Whole-cell and single-channel patch clamp of MiRP1+HERG co-expression and LQT-associated mutants in oocytes and mammalian cells","pmids":["10219239"],"confidence":"High","gaps":["Stoichiometry and structural basis of the HERG-KCNE2 interface not resolved","Whether MiRP1 is the dominant native IKr β subunit in human heart not established here"]},{"year":2000,"claim":"Extended KCNE2 partner promiscuity beyond hERG to neuronal M-channel subunits, raising the question of how one β subunit modulates structurally distinct α subunits.","evidence":"Co-immunoprecipitation and whole-cell electrophysiology of KCNE2 with KCNQ2/KCNQ3 in COS cells","pmids":["11034315"],"confidence":"Medium","gaps":["No native neuronal demonstration of KCNQ2/3-KCNE2 complexes","Physiological relevance to brain excitability untested"]},{"year":2001,"claim":"Distinguished which KCNE2-induced biophysical changes actually matter for repolarization and localized part of the HERG interaction to the cyclic nucleotide binding domain.","evidence":"HERG CNBD mutagenesis, co-expression electrophysiology, and computational action potential modeling","pmids":["11278781","11440975"],"confidence":"Medium","gaps":["Direct structural contact within the CNBD not mapped","Modeling conclusions depend on assumed expression levels"]},{"year":2002,"claim":"Defined an additional gating mechanism (accelerated inactivation) by which a KCNE2 mutation reduces IKr, broadening the molecular spectrum of LQT6.","evidence":"Whole-cell patch clamp and co-localization of V65M mutant with HERG in CHO cells","pmids":["12185453"],"confidence":"Medium","gaps":["Penetrance and in vivo arrhythmia link not addressed","Single mutant in a heterologous background"]},{"year":2003,"claim":"Identified HCN pacemaker channels as physical and functional KCNE2 partners, expanding its role into cardiac automaticity and identifying the C-terminal tail as the HCN4 interaction site.","evidence":"Two-electrode and patch clamp in oocytes/CHO cells plus yeast two-hybrid for HCN4; AP-clamp analysis of LQT6 mutants on HERG","pmids":["12856183","12923204"],"confidence":"Medium","gaps":["Native HCN-KCNE2 association not yet shown","Stoichiometry of the interaction unknown"]},{"year":2004,"claim":"Confirmed native cardiac HCN2-KCNE2 complexes and discovered the gain-of-function R27C variant acting through the KCNQ1-KCNE2 background current, linking KCNE2 to atrial fibrillation as distinct from LQT.","evidence":"Co-IP of endogenous HCN2 and KCNE2 in neonatal rat myocytes; AF-kindred sequencing with electrophysiology testing R27C against multiple partners","pmids":["15292247","15368194"],"confidence":"High","gaps":["How a single residue selectively affects KCNQ1 but not HERG/HCN currents not mechanistically explained","In vivo AF causation not demonstrated"]},{"year":2004,"claim":"Established the apical gastric KCNQ1-KCNE2 channel and its regulation by acid pH, PIP2, cAMP, and purinergic signaling, defining KCNE2's first epithelial physiological context.","evidence":"In situ hybridization, confocal immunofluorescence, and patch clamp in parietal cells and COS cells","pmids":["15579540"],"confidence":"High","gaps":["Direct coupling to H+,K+-ATPase activity not established","In vivo requirement not yet tested at this stage"]},{"year":2006,"claim":"Demonstrated in vivo that KCNE2 is essential for gastric acid secretion with a gene-dose effect, converting in vitro complex assembly into a defined organ-level physiological requirement.","evidence":"Targeted Kcne2 knockout mice with acid-secretion measurement, histology, and KCNQ1 immunolocalization","pmids":["16754665"],"confidence":"High","gaps":["Secondary systemic consequences of achlorhydria not yet mapped","Mechanism of abnormal KCNQ1 distribution unclear"]},{"year":2006,"claim":"Showed KCNE2 participates in native cardiac IKs as a tripartite KCNQ1-KCNE1-KCNE2 complex and modulates Kv4.3 Ito, reinforcing multi-channel cardiac regulation.","evidence":"Co-IP and immunocytochemistry in adult rat ventricular myocytes; patch clamp of Kv4.3 in COS-7 cells","pmids":["17161791","17259113"],"confidence":"Medium","gaps":["Stoichiometry within the tripartite complex unresolved","Kv4.3 modulation rests on single-method electrophysiology"]},{"year":2007,"claim":"Revealed KCNE2's distinctive trafficking behavior versus KCNE1 and provided the first gating mechanism for the reduced-penetrance T10M arrhythmia variant.","evidence":"Co-IP, surface labeling, Brefeldin A and ER-retention engineering for trafficking; whole-cell clamp of T10M in CHO cells","pmids":["17895974","18006462"],"confidence":"Medium","gaps":["Functional significance of extracellular/vesicular KCNE2 pool unknown","Trafficking differences not linked to a defined sorting determinant yet"]},{"year":2008,"claim":"Identified Kv1.5 as a novel in vivo KCNE2 partner and showed KCNE2 controls Kv1.5 protein levels and intercalated-disc trafficking, while structural spectroscopy began defining MiRP1 domain architecture.","evidence":"Kcne2 knockout mice with myocyte electrophysiology and native co-IP; FTIR/CD spectroscopy of synthetic MiRP1 peptides; Kv4.3/KChIP2 complex electrophysiology","pmids":["18603586","18221016","18501111","18536731"],"confidence":"High","gaps":["Mechanism by which KCNE2 stabilizes mature Kv1.5 protein not defined","Peptide spectroscopy does not represent the native folded protein"]},{"year":2009,"claim":"Consolidated KCNE2 as a broad single-channel-level modulator of all four HCN isoforms, Kv2.1, and Kv4.3, and showed it can dynamically substitute into IKs complexes and traffic independently of KCNQ1.","evidence":"Whole-cell and single-channel recordings, membrane fractionation, native-tissue co-IP (Kv2.1), pulse-chase and biotinylation trafficking assays, myocyte electrophysiology","pmids":["19429827","19219384","19372218","20042375"],"confidence":"Medium","gaps":["Tissue-specific partner selection rules not established","How one β subunit produces opposite effects on different α subunits unexplained"]},{"year":2011,"claim":"Defined KCNE2 as a secretory-pathway checkpoint that retains N-type-inactivating Kv subunits and uncovered choroid plexus epithelial functions controlling CSF ion homeostasis.","evidence":"Electrophysiology, co-IP, immunofluorescence, Brefeldin A and dynamin-inhibitor dissection; Kcne2 KO with CPe patch clamp, pharmacology, and CSF ion measurement","pmids":["21943416","21943417","21859894"],"confidence":"High","gaps":["Molecular machinery executing ER retention not identified","Link between altered CPe trafficking and CSF chloride change not fully mechanistic"]},{"year":2010,"claim":"Provided rigorous NMR backbone assignments and helical secondary-structure mapping of human MiRP1, establishing a structural framework for interpreting interaction studies.","evidence":"Solution NMR triple-resonance assignment and CD spectroscopy of E. coli-expressed MiRP1 in detergent micelles","pmids":["21087668"],"confidence":"Medium","gaps":["No full tertiary structure or channel-bound conformation","No functional validation in this study"]},{"year":2012,"claim":"Extended the apical KCNQ1-KCNE2 channel's physiological role to thyroid iodide uptake and dissected which transport step requires it, and defined neuronal HCN dysfunction upon Kcne2 loss.","evidence":"In vivo PET iodide imaging, in vitro uptake assays, and Kcne2 KO/pharmacology for thyroid; KO brain-slice patch clamp and co-IP for thalamocortical HCN","pmids":["22549510","22880098"],"confidence":"High","gaps":["Negative brain co-IP leaves the neuronal HCN mechanism likely indirect and undefined","Cell type mediating iodide retention not pinpointed"]},{"year":2011,"claim":"Identified S98 phosphorylation as a post-translational mechanism by which KCNE2 controls hERG protein stability and IKr amplitude.","evidence":"Phospho-specific antibody, adenoviral manipulation, Western blotting, and immunofluorescence in adult cardiac myocytes","pmids":["22180649"],"confidence":"Medium","gaps":["Kinase responsible for S98 phosphorylation not identified","Degradation pathway targeting hERG not defined"]},{"year":2014,"claim":"Linked the KCNQ1-KCNE2 channel to solute-transporter regulation and mapped the precise transmembrane interaction residues distinguishing KCNE2 from KCNE1, and added Cav1.2 as a physical KCNE2 partner.","evidence":"Native-tissue co-IP, myo-inositol uptake assays, CSF metabolomics and seizure rescue; solution NMR plus electrophysiology of KCNE2-KCNQ1 contacts; Cav1.2 co-IP, domain deletion and patch clamp","pmids":["24595108","24827085","24681347"],"confidence":"Medium","gaps":["How a constitutive K+ channel mechanistically inhibits a Na+-coupled transporter not fully resolved","Cav1.2 regulation mechanism beyond the N-terminal inhibitory module untested"]},{"year":2016,"claim":"Connected KCNE2 loss to altered cellular survival signaling and a hypoxia-dependent cytoskeletal interaction, broadening its role beyond channel gating.","evidence":"Ischemia/reperfusion in Kcne2 KO mice with GSK-3β phospho-analysis and pharmacological epistasis; yeast two-hybrid and condition-dependent co-IP for filamin C","pmids":["26952045","26956495"],"confidence":"Medium","gaps":["Mechanism linking KCNE2 to GSK-3β phosphorylation unknown","Filamin C interaction lacks functional electrophysiological readout"]},{"year":2017,"claim":"Established KCNE2's roles in β-cell insulin secretion and as a brake on Cav1.2-driven calcineurin-NFAT hypertrophic signaling, extending its physiology to metabolic and remodeling pathways.","evidence":"Kcne2 KO glucose tolerance, insulin assays and β-cell patch clamp; bidirectional KCNE2 manipulation with TAC model, calcineurin assays, and in vivo gene delivery","pmids":["28280005","28611128"],"confidence":"High","gaps":["Channel partner mediating β-cell K+ current loss not defined","Direct vs indirect contribution of Cav1.2 modulation to hypertrophy not separated"]},{"year":2019,"claim":"Resolved isoform- and concentration-dependent KCNE2:HCN stoichiometry, defined the KSKR ER-export motif required for KCNE2 forward trafficking, and added pulmonary KCNQ1-KCNE2 complexes governing gas exchange.","evidence":"Single-molecule subunit counting; trafficking motif mutagenesis with biotinylation and electrophysiology; lung-tissue co-IP and Kcne2 KO blood-gas analysis","pmids":["31235733","31679457","31162977"],"confidence":"Medium","gaps":["Functional consequence of variable stoichiometry in native tissue untested","Trafficking factors recognizing the KSKR motif unidentified"]},{"year":2020,"claim":"Demonstrated that cardiac-specific KCNE2 loss causes dilated cardiomyopathy and that its systemic loss reshapes the gut microbiome via achlorhydria, linking organ-level and microbial axes to heart failure progression.","evidence":"Cardiac-specific vs global Kcne2 KO with histology, microbiome profiling, PPI treatment, and survival analysis","pmids":["32584506"],"confidence":"Medium","gaps":["Channel partner driving cardiomyopathy in cardiac-specific KO not pinpointed","Mechanism by which microbiome changes modulate cardiac survival unclear"]},{"year":2021,"claim":"Identified testin as a C-terminal KCNE2 partner that selectively reverses KCNE2 modulation of Kv1.5 but not KCNQ1, revealing partner-specific regulatory layering.","evidence":"Yeast two-hybrid, co-IP, and whole-cell patch clamp in CHO cells","pmids":["33464998"],"confidence":"Low","gaps":["In vitro system only, no native-tissue confirmation","Physiological context of testin-KCNE2 regulation untested"]},{"year":2022,"claim":"Defined how KCNE2 imposes Ca2+/calmodulin dependence on the KCNQ1-KCNE2 complex, providing the mechanism by which KCNQ1 gain-of-function mutations cause disease through this complex.","evidence":"Whole-cell patch clamp with intracellular Ca2+ and calmodulin manipulation and KCNQ1 mutagenesis in heterologous cells","pmids":["36077086"],"confidence":"Medium","gaps":["Structural basis of Ca2+/calmodulin gating within the complex not resolved","Tissue-specific relevance of this regulatory mode not tested"]},{"year":null,"claim":"How a single small β subunit selects among many α-subunit partners in a tissue-specific manner, and the structural basis for its opposing effects on different channels, remains unresolved.","evidence":"No discovery in the timeline reconciles the partner-selection rules or provides a channel-bound full structure","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of any KCNE2-channel complex","Determinants of tissue-specific partner choice unknown","Rules governing gain- vs loss-of-function modulation across partners undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,7,17,18,19,30]},{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[8,24,26]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[32,40]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[8,11,20,24]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[13,23,37]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[1,27]},{"term_id":"R-HSA-397014","term_label":"Muscle contraction","supporting_discovery_ids":[0,17]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[8,24,26]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[23,37]}],"complexes":["KCNQ1-KCNE2 channel","HERG(KCNH2)-KCNE2 (IKr) channel","KCNQ1-KCNE1-KCNE2 (IKs) tripartite channel","HCN-KCNE2 pacemaker channel"],"partners":["KCNH2","KCNQ1","HCN4","HCN2","KCNA5","KCNB1","CACNA1C","TES"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9Y6J6","full_name":"Potassium voltage-gated channel subfamily E member 2","aliases":["MinK-related peptide 1","MiRP1","Minimum potassium ion channel-related peptide 1","Potassium channel subunit beta MiRP1"],"length_aa":123,"mass_kda":14.5,"function":"Ancillary protein that functions as a regulatory subunit of the voltage-gated potassium (Kv) channel complex composed of pore-forming and potassium-conducting alpha subunits and of regulatory beta subunits (PubMed:10219239, PubMed:11034315, PubMed:11101505, PubMed:12185453, PubMed:20533308). KCNE2 beta subunit modulates the gating kinetics and enhances stability of the channel complex (PubMed:10219239, PubMed:11034315, PubMed:11101505, PubMed:12185453, PubMed:20533308). Alters the gating of the delayed rectifier Kv channel containing KCNB1 alpha subunit (PubMed:11101505, PubMed:20533308). Associates with KCNH2/HERG alpha subunit Kv channel to form the rapidly activating component of the delayed rectifying potassium current (IKr) in heart (PubMed:10219239, PubMed:12185453). May associate with KCNQ2 and/or KCNQ3 alpha subunits to modulate the native M-type current (PubMed:11034315). May associate with HCN1 and HCN2 channel subunits to increase potassium current (By similarity). Forms a heterooligomer complex with KCNQ1/KVLQT1 alpha subunits which leads to currents with an apparently instantaneous activation, a rapid deactivation process and a linear current-voltage relationship and decreases the amplitude of the outward current (PubMed:11101505). KCNQ1-KCNE2 channel associates with Na(+)-coupled myo-inositol symporter in the apical membrane of choroid plexus epithelium and regulates the myo-inositol gradient between blood and cerebrospinal fluid with an impact on neuron excitability (By similarity)","subcellular_location":"Cell membrane; Apical cell membrane","url":"https://www.uniprot.org/uniprotkb/Q9Y6J6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KCNE2","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/KCNE2","total_profiled":1310},"omim":[{"mim_id":"615441","title":"CARDIAC ARRHYTHMIA SYNDROME, WITH OR WITHOUT SKELETAL MUSCLE WEAKNESS; CARDAR","url":"https://www.omim.org/entry/615441"},{"mim_id":"613695","title":"LONG QT SYNDROME 5; LQT5","url":"https://www.omim.org/entry/613695"},{"mim_id":"613693","title":"LONG QT SYNDROME 6; LQT6","url":"https://www.omim.org/entry/613693"},{"mim_id":"613688","title":"LONG QT SYNDROME 2; LQT2","url":"https://www.omim.org/entry/613688"},{"mim_id":"611493","title":"ATRIAL FIBRILLATION, FAMILIAL, 4; ATFB4","url":"https://www.omim.org/entry/611493"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"stomach 1","ntpm":299.1}],"url":"https://www.proteinatlas.org/search/KCNE2"},"hgnc":{"alias_symbol":["MiRP1","LQT6"],"prev_symbol":[]},"alphafold":{"accession":"Q9Y6J6","domains":[{"cath_id":"1.20.5","chopping":"1-44","consensus_level":"medium","plddt":86.5039,"start":1,"end":44},{"cath_id":"1.20.5","chopping":"45-107","consensus_level":"medium","plddt":77.4798,"start":45,"end":107}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y6J6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y6J6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y6J6-F1-predicted_aligned_error_v6.png","plddt_mean":78.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KCNE2","jax_strain_url":"https://www.jax.org/strain/search?query=KCNE2"},"sequence":{"accession":"Q9Y6J6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y6J6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y6J6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y6J6"}},"corpus_meta":[{"pmid":"10219239","id":"PMC_10219239","title":"MiRP1 forms IKr potassium channels with HERG and is associated with cardiac arrhythmia.","date":"1999","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/10219239","citation_count":1032,"is_preprint":false},{"pmid":"10973849","id":"PMC_10973849","title":"Spectrum of mutations in long-QT syndrome genes. KVLQT1, HERG, SCN5A, KCNE1, and KCNE2.","date":"2000","source":"Circulation","url":"https://pubmed.ncbi.nlm.nih.gov/10973849","citation_count":962,"is_preprint":false},{"pmid":"15368194","id":"PMC_15368194","title":"Identification of a KCNE2 gain-of-function mutation in patients with familial atrial fibrillation.","date":"2004","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/15368194","citation_count":311,"is_preprint":false},{"pmid":"11927665","id":"PMC_11927665","title":"A comparison of currents carried by HERG, with and without coexpression of MiRP1, and the native rapid delayed rectifier current. Is MiRP1 the missing link?","date":"2002","source":"The Journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/11927665","citation_count":151,"is_preprint":false},{"pmid":"16754665","id":"PMC_16754665","title":"The KCNE2 potassium channel ancillary subunit is essential for gastric acid secretion.","date":"2006","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16754665","citation_count":121,"is_preprint":false},{"pmid":"15579540","id":"PMC_15579540","title":"Heteromeric KCNE2/KCNQ1 potassium channels in the luminal membrane of gastric parietal cells.","date":"2004","source":"The Journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/15579540","citation_count":110,"is_preprint":false},{"pmid":"15292247","id":"PMC_15292247","title":"MiRP1 modulates HCN2 channel expression and gating in cardiac myocytes.","date":"2004","source":"The Journal of biological 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hearts.","date":"2004","source":"Circulation","url":"https://pubmed.ncbi.nlm.nih.gov/15066947","citation_count":67,"is_preprint":false},{"pmid":"11468227","id":"PMC_11468227","title":"Screening for mutations and polymorphisms in the genes KCNH2 and KCNE2 encoding the cardiac HERG/MiRP1 ion channel: implications for acquired and congenital long Q-T syndrome.","date":"2001","source":"Clinical chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11468227","citation_count":65,"is_preprint":false},{"pmid":"20625512","id":"PMC_20625512","title":"Targeted deletion of Kcne2 causes gastritis cystica profunda and gastric neoplasia.","date":"2010","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/20625512","citation_count":65,"is_preprint":false},{"pmid":"24595108","id":"PMC_24595108","title":"KCNQ1, KCNE2, and Na+-coupled solute transporters form reciprocally regulating complexes that affect neuronal excitability.","date":"2014","source":"Science 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physiology. 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Yi xue ban = Journal of Zhejiang University. Medical sciences","url":"https://pubmed.ncbi.nlm.nih.gov/17717828","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":41995,"output_tokens":10708,"usd":0.143302,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":21131,"output_tokens":7427,"usd":0.145665,"stage2_stop_reason":"end_turn"},"total_usd":0.288967,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"KCNE2 (MiRP1) assembles with HERG (KCNH2) to form IKr potassium channels. Co-expression of MiRP1 with HERG alters gating kinetics, unitary conductance, regulation by potassium, and biphasic inhibition by E-4031, making the complex resemble native cardiac IKr. Three KCNE2 missense mutations associated with LQT syndrome cause channels that open slowly and close rapidly, reducing potassium currents.\",\n      \"method\": \"Electrophysiology (whole-cell and single-channel patch clamp), heterologous expression in Xenopus oocytes and mammalian cells, functional characterization of LQT-associated mutants\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution of channel complex, functional characterization with multiple methods, widely replicated landmark paper\",\n      \"pmids\": [\"10219239\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"KCNE2 (MiRP1) co-assembles with KCNQ2 and/or KCNQ3 (M-type channel subunits expressed in brain) and accelerates their deactivation kinetics. KCNE2 mRNA is expressed in brain regions that also express KCNQ2/KCNQ3.\",\n      \"method\": \"Co-immunoprecipitation, heterologous expression in COS cells, whole-cell electrophysiology\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP plus electrophysiology, single lab\",\n      \"pmids\": [\"11034315\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The cyclic nucleotide binding domain (CNBD) of HERG may be involved in its interaction with KCNE2: co-expression of KCNE2 with CNBD-mutant HERG conferred a partially dominant current suppression not seen with wild-type HERG alone, indicating KCNE2 plays a role in determining phenotypic severity of some LQT2 mutations.\",\n      \"method\": \"Site-directed mutagenesis of HERG CNBD, heterologous co-expression, whole-cell electrophysiology\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis plus functional electrophysiology, single lab\",\n      \"pmids\": [\"11278781\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"KCNE2 co-expression with HERG alters both current kinetics and current density; incorporation of these effects into a quantitative action potential model showed that only changes in current density (not kinetics) significantly affect ventricular repolarization.\",\n      \"method\": \"Heterologous co-expression, whole-cell electrophysiology, computational action potential modeling\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — electrophysiology with quantitative modeling, single lab\",\n      \"pmids\": [\"11440975\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"A novel KCNE2 missense mutation V65M accelerates the inactivation time course of HERG/MiRP1 channels, thereby reducing IKr current density; mutant and wild-type MiRP1 co-localize with HERG subunits and form functional channels.\",\n      \"method\": \"Whole-cell patch clamp in CHO cells, single-strand conformation polymorphism analysis, direct sequencing, co-localization immunofluorescence\",\n      \"journal\": \"Journal of molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — electrophysiology plus co-localization, single lab\",\n      \"pmids\": [\"12185453\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"KCNE2 co-expression with HCN4 in Xenopus oocytes and CHO cells enhances HCN4 current amplitudes, slows activation kinetics, and shifts half-maximal activation voltage to more negative potentials. The C-terminal tail of KCNE2 (but not other KCNE subunits) interacts with the C-terminal tail of HCN4 in yeast two-hybrid assays.\",\n      \"method\": \"Two-electrode voltage clamp (Xenopus oocytes), patch clamp (CHO cells), yeast two-hybrid protein interaction assay\",\n      \"journal\": \"Pflugers Archiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — electrophysiology in two expression systems plus yeast two-hybrid, single lab\",\n      \"pmids\": [\"12856183\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Wild-type MiRP1 modulates HERG channel gating (more negative steady-state activation, altered inactivation), and three LQT6-associated MiRP1 mutants (T8A, Q9E, M54T) further alter HERG gating in distinct ways. During premature action potential clamp protocols, T8A and Q9E mutants augment HERG currents in early diastole, a potentially pro-arrhythmic mechanism.\",\n      \"method\": \"Whole-cell patch clamp in CHO cells at 37°C, action potential clamp protocols\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — electrophysiology with multiple mutants and physiological AP clamp, single lab\",\n      \"pmids\": [\"12923204\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"KCNE2 (MiRP1) co-assembles with HCN2 in neonatal rat ventricular myocytes, as demonstrated by co-immunoprecipitation of both expressed and endogenous subunits. Co-expression of MiRP1 with HCN2 produces a 4-fold increase in pacemaker current maximal conductance and alters activation/deactivation kinetics at physiologically relevant voltages.\",\n      \"method\": \"Adenoviral overexpression in neonatal rat ventricular myocytes, co-immunoprecipitation (expressed and endogenous proteins), whole-cell patch clamp\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP of both exogenous and endogenous proteins in native cardiac cells, plus functional electrophysiology\",\n      \"pmids\": [\"15292247\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"KCNE2 and KCNQ1 form a heteromeric K+ channel in the luminal membrane of gastric parietal cells. The KCNE2/KCNQ1 channel is activated by acidic pH, PIP2, cAMP, and purinergic receptor stimulation. KCNQ1 distribution in parietal cells does not substantially change during stimulation-induced H+,K+-ATPase trafficking.\",\n      \"method\": \"In situ hybridization, immunofluorescence, confocal microscopy in parietal cells and COS cells, patch clamp electrophysiology\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (imaging, electrophysiology, pharmacology) confirming luminal localization and function\",\n      \"pmids\": [\"15579540\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"KCNE2 R27C is a gain-of-function mutation affecting the KCNQ1-KCNE2 channel (responsible for a background potassium current) and is associated with familial atrial fibrillation. Unlike LQT-associated KCNE2 mutations, R27C does not alter HERG-KCNE2 current or HCN channel currents.\",\n      \"method\": \"Gene sequencing in AF kindreds, heterologous expression in Xenopus oocytes/mammalian cells, whole-cell electrophysiology\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional electrophysiology with multiple channel partners tested, single lab\",\n      \"pmids\": [\"15368194\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"KCNE2 is essential for gastric acid secretion in vivo. Kcne2−/− mice have severe achlorhydria, abnormal parietal cell morphology, hypergastrinemia, and gastric glandular hyperplasia. KCNQ1 exhibited abnormal distribution in gastric glands from Kcne2−/− mice. Kcne2+/− mice showed reduced proton secretion (gene-dose effect), demonstrating that KCNE2 is required for normal gastric acid secretion.\",\n      \"method\": \"Targeted murine kcne2 gene disruption (knockout), gastric acid secretion measurement, histology, immunohistochemistry, Western blotting\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined cellular and physiological phenotype including gene-dose effect, multiple orthogonal readouts\",\n      \"pmids\": [\"16754665\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"KCNE2 is co-localized with KCNQ1 and KCNE1 at the surface membrane and t-tubules of adult rat ventricular myocytes. Co-immunoprecipitation shows KCNQ1, KCNE1, and KCNE2 can form a tripartite complex. KCNE2 co-expression with KCNQ1 and KCNE1 decreases IKs current amplitude without altering its slow gating kinetics.\",\n      \"method\": \"Immunocytochemistry, co-immunoprecipitation in cardiomyocytes, patch clamp in oocytes and COS-7 cells\",\n      \"journal\": \"Heart rhythm\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP plus electrophysiology in native myocytes, single lab\",\n      \"pmids\": [\"17161791\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"KCNE2 modulates Kv4.3 (the major alpha subunit of cardiac Ito): co-expression in COS-7 cells reduces peak current density, slows inactivation kinetics, causes a positive shift of steady-state inactivation, and accelerates recovery from inactivation.\",\n      \"method\": \"Whole-cell patch clamp in COS-7 cells after transfection\",\n      \"journal\": \"Journal of Southern Medical University\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single electrophysiology method, no co-IP or structural data\",\n      \"pmids\": [\"17259113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"KCNE2 has differential association with HERG compared to KCNE1: when forward trafficking is blocked (by Brefeldin A or ER-retention signals), KCNE2 abundance and association with HERG increase, while KCNE1 is preferentially retained in the ER. A significant fraction of KCNE2 is found extracellularly (soluble and vesicle-associated). HERG co-localizes more completely with KCNE1 at all membrane compartments.\",\n      \"method\": \"Co-immunoprecipitation, confocal immunofluorescence, surface labeling, Brefeldin A trafficking block, ER-retention signal engineering\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal biochemical and imaging methods, single lab\",\n      \"pmids\": [\"17895974\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"A T10M mutation in MiRP1 (KCNE2) causes ≤80% reduction in hERG tail current, left-shifted steady-state inactivation, and 50% slower recovery from inactivation, providing a mechanism for reduced-penetrance inherited arrhythmia exacerbated by superimposed electrolyte disturbances.\",\n      \"method\": \"Whole-cell voltage clamp in transfected CHO cells\",\n      \"journal\": \"Cardiovascular research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — electrophysiology with multiple gating parameters measured, single lab\",\n      \"pmids\": [\"18006462\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The secondary structure of MiRP1 (KCNE2) was characterized: the N-terminal extracellular domain is predominantly non-ordered in aqueous media but alpha-helical in lipid micelles; the transmembrane domain is predominantly alpha-helix/non-ordered; the C-terminal domain is predominantly alpha-helical when incorporated into lipid bilayers. Full-length MiRP1 contains ~34% alpha-helix, 23% beta-strand, and 43% non-ordered structure.\",\n      \"method\": \"FTIR and CD spectroscopy of synthetic MiRP1 peptides in various detergent/lipid environments\",\n      \"journal\": \"Protein and peptide letters\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 1 / Weak — structural spectroscopy of synthetic peptides, not native protein; single lab, no functional validation\",\n      \"pmids\": [\"18221016\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"KCNE2 (MiRP1) modulates Kv4.3 Ito current when co-expressed as part of the Kv4.3/KChIP2/MiRP1 complex: it slows activation and inactivation kinetics and produces an 'overshoot' during recovery from inactivation. Co-expression of both KChIP2c and KCNE2 with Kv4.2 yields a current profile more similar to native cardiac Ito than either beta subunit alone.\",\n      \"method\": \"Whole-cell patch clamp in CHO cells stably expressing Kv4.3/KChIP2 or COS-7 cells transfected with Kv4.2/KChIP2c/KCNE2\",\n      \"journal\": \"Acta pharmacologica Sinica / British journal of pharmacology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — electrophysiology only, no co-IP or structural confirmation, single lab\",\n      \"pmids\": [\"18501111\", \"18536731\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Targeted disruption of murine kcne2 prolonged ventricular action potential duration and reduced IK,slow1 by 50% (generated by Kv1.5, a novel in vivo partner for MiRP1) and Ito,f by ~25% (generated by Kv4 alpha subunits). Ventricular MiRP1 protein co-immunoprecipitated with native Kv1.5 and Kv4.2 but not Kv1.4 or Kv4.3. Kcne2 deletion also reduced mature Kv1.5 protein levels by 50% and disrupted Kv1.5 trafficking to intercalated discs.\",\n      \"method\": \"Targeted murine kcne2 gene disruption, whole-cell patch clamp in isolated ventricular myocytes, co-immunoprecipitation from native tissue, Western blotting, immunohistochemistry, in vivo QTc measurement\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO, co-IP from native tissue, multiple orthogonal methods, defined cellular/physiological phenotype\",\n      \"pmids\": [\"18603586\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"KCNE2 modulates all four cardiac HCN isoforms: co-expression increases current densities of HCN1, HCN2, and HCN4, accelerates activation kinetics, and increases single-channel amplitude and conductance. KCNE2 also increases HCN2 and HCN4 membrane protein expression (2.2-fold and 1.6-fold, respectively). These effects demonstrate direct functional interaction at the single-channel level.\",\n      \"method\": \"Whole-cell patch clamp and single-channel recordings in CHO cells, Western blotting of membrane fractions\",\n      \"journal\": \"American journal of physiology. Heart and circulatory physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — whole-cell and single-channel electrophysiology plus protein expression analysis, single lab\",\n      \"pmids\": [\"19429827\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"KCNE2 forms native cardiac complexes with Kv2.1, as shown by co-immunoprecipitation from rat heart tissue. KCNE2 (MiRP1) co-expression reduces Kv2.1 current density 2-fold and slows activation and deactivation kinetics. LQT-associated KCNE2 mutations M54T and I57T greatly alter Kv2.1 activation kinetics.\",\n      \"method\": \"Co-immunoprecipitation from rat heart tissue, whole-cell patch clamp in CHO cells\",\n      \"journal\": \"The Journal of membrane biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP from native tissue plus functional electrophysiology, single lab\",\n      \"pmids\": [\"19219384\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"KCNE2 can substitute for KCNE1 in the KCNQ1-KCNE1 (IKs) channel complex due to dynamic KCNE1 turnover. KCNE2 independently traffics to the cell surface without requiring KCNQ1 co-assembly. In guinea pig ventricular myocytes, adenovirus-mediated KCNE2 expression co-localizes with native KCNQ1 and reduces native IKs current density.\",\n      \"method\": \"Pulse-chase experiments in COS-7 cells, biotinylation assays, vesicle injection in Xenopus oocytes, adenoviral gene delivery in adult cardiomyocytes, electrophysiology\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal approaches (pulse-chase, biotinylation, electrophysiology in native myocytes), single lab\",\n      \"pmids\": [\"19372218\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"LQT6 KCNE2 M54T mutation modulates Kv4.3 (Ito alpha subunit): M54T and I57T variants significantly increase Ito current density, slow inactivation, and accelerate recovery from inactivation compared to wild-type KCNE2, suggesting a gain-of-function for Ito that may contribute to arrhythmogenesis.\",\n      \"method\": \"Whole-cell patch clamp in heterologous cell line co-expressing Kv4.3 and wild-type or mutant KCNE2\",\n      \"journal\": \"Heart rhythm\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — electrophysiology with multiple mutants, single lab; mechanistically distinct finding from same mutations studied elsewhere\",\n      \"pmids\": [\"20042375\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Solution NMR backbone assignments of human MiRP1 (KCNE2) were achieved in LMPG detergent micelles. CD spectroscopy revealed high alpha-helical content. Secondary structure analysis based on backbone chemical shifts showed multiple alpha-helical stretches along the primary sequence.\",\n      \"method\": \"Solution NMR (triple resonance backbone assignment), circular dichroism spectroscopy, protein expression and purification in E. coli\",\n      \"journal\": \"Protein expression and purification\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — NMR backbone assignment is rigorous structural method, but no functional validation in this study; single lab\",\n      \"pmids\": [\"21087668\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"KCNE2 (along with KCNE1) retains homomeric N-type inactivating Kv alpha subunits (Kv1.4, Kv3.4) intracellularly early in the secretory pathway, suppressing their surface expression. This retention requires alpha-beta co-assembly, does not involve dynamin-dependent endocytosis, and acts as a checkpoint governing Kv channel alpha-subunit composition.\",\n      \"method\": \"Electrophysiology, co-immunoprecipitation, immunofluorescence, Brefeldin A treatment, dynamin inhibitor studies in mammalian cells\",\n      \"journal\": \"Biophysical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (electrophysiology, biochemistry, imaging, pharmacological dissection), single lab but rigorous\",\n      \"pmids\": [\"21943416\", \"21943417\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In the choroid plexus epithelium (CPe), KCNE2 is enriched in the apical membrane where it co-localizes with KCNQ1 and KCNA3. Kcne2 deletion increases CPe outward K+ current 2-fold, alters KCNQ1 and KCNA3 trafficking polarity, hyperpolarizes the CPe membrane by 9 mV, and increases CSF [Cl−] by 14%.\",\n      \"method\": \"Immunofluorescence with Kcne2−/− negative control, whole-cell patch clamp in CPe cells, pharmacological dissection (XE991, margatoxin, dendrotoxin), ion concentration measurements\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined cellular and CSF phenotype, multiple orthogonal methods\",\n      \"pmids\": [\"21859894\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"KCNE2 S98 phosphorylation modulates hERG/IKr amplitude by accelerating hERG protein degradation and reducing cell-surface hERG protein levels. S98 dephosphorylation leads to increased hERG/IKr amplitude. KCNE2 protein is more abundant in ventricles than atria in human and animal hearts.\",\n      \"method\": \"Adenovirus-mediated genetic manipulation in adult cardiac myocytes, phospho-specific antibody (Ab2), Western blotting, immunofluorescence\",\n      \"journal\": \"American journal of physiology. Heart and circulatory physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phospho-specific antibody with adenoviral manipulation revealing novel PTM-dependent mechanism, single lab\",\n      \"pmids\": [\"22180649\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"KCNQ1-KCNE2 is required for adequate thyroid iodide (I−) uptake. Pharmacological blockade of KCNQ1 impairs thyroid I− uptake in vivo and in vitro. Kcne2 deletion doubles the rate of free I− efflux from the thyroid following ClO4− injection but does not affect Duox/TPO-mediated I− organification.\",\n      \"method\": \"Dynamic positron emission tomography in vivo, in vitro I− uptake assays, Kcne2 knockout mice, pharmacological inhibition with chromanol 293B\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo PET combined with in vitro assays and genetic KO, multiple orthogonal methods defining the mechanistic step\",\n      \"pmids\": [\"22549510\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Kcne2 gene deletion impairs HCN channel function in thalamocortical neurons: it shifts the voltage-dependence of Ih activation to more hyperpolarized potentials, slows gating kinetics, decreases Ih density, and increases input resistance and burst firing. Whole-brain HCN1 and HCN2 (but not HCN4) expression is reduced. Co-immunoprecipitation from whole-brain lysates did not detect KCNE2 interaction with HCN1 or HCN2.\",\n      \"method\": \"Kcne2 knockout mice, whole-cell patch clamp in brain slices (VB thalamic and cortical layer 6 neurons), Western blotting, co-immunoprecipitation\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO with defined neuronal phenotype; co-IP was negative, suggesting indirect mechanism in this tissue\",\n      \"pmids\": [\"22880098\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"An LQT6 M54T MiRP1 mutation decreases HCN4 current density by 80% and slows HCN4 activation at physiologically relevant voltages in ventricular myocytes, causing sinus bradycardia through effects on pacemaker If. M54T effects on HCN4 are additive with its effects on hERG kinetics.\",\n      \"method\": \"Whole-cell patch clamp in neonatal rat ventricular myocytes transfected with human HCN4 or HCN2 ± wild-type or M54T MiRP1, computational simulation\",\n      \"journal\": \"Journal of cardiovascular electrophysiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — electrophysiology in native myocyte background with computational modeling, single lab\",\n      \"pmids\": [\"23631727\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"KCNQ1, KCNE2, and Na+-coupled solute transporters (SMIT1, SGLT1) form reciprocally regulating complexes. KCNE2 and KCNQ1 co-localize and co-immunoprecipitate with SMIT1 in choroid plexus epithelium. The constitutively active KCNQ1-KCNE2 heteromeric channel inhibits myo-inositol transport by SMIT1. Kcne2−/− mice show reduced myo-inositol in CSF and increased seizure susceptibility corrected by myo-inositol injections.\",\n      \"method\": \"Co-immunoprecipitation from choroid plexus, heterologous co-expression with myo-inositol uptake assays, global metabolite profiling (Kcne2−/− mice), behavioral assays\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — co-IP from native tissue, functional transport assays, in vivo metabolomics, and rescue experiments; multiple orthogonal methods\",\n      \"pmids\": [\"24595108\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"KCNE2 physically interacts with Cav1.2 (L-type Ca2+ channel alpha subunit) and modulates L-type Ca2+ current (ICa,L): KCNE2 overexpression decreases ICa,L amplitude and alters its voltage-dependence and inactivation kinetics; knockdown has opposite effects. Deletion of the N-terminal inhibitory module (NTI) of Cav1.2 abolishes KCNE2 regulation. The AF-associated R27C mutation enhances KCNE2 suppression of ICa,L.\",\n      \"method\": \"Co-immunoprecipitation and co-localization in cardiomyocytes and HEK293 cells, whole-cell patch clamp, adenoviral overexpression and RNA interference\",\n      \"journal\": \"Journal of molecular and cellular cardiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus electrophysiology in native cardiomyocytes with domain deletion mutagenesis, single lab\",\n      \"pmids\": [\"24681347\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"KCNE2 transmembrane domain residue Ile64 interacts with KCNQ1 residues Phe340 and Phe275 (different interaction mode from KCNE1). KCNE2 N-terminus decreases surface expression and activity of KCNQ1; KCNE2 C-terminus has minimal influence on KCNQ1 gating (unlike KCNE1 C-terminus).\",\n      \"method\": \"Electrophysiology, immunofluorescence, solution NMR and backbone flexibility analysis of transmembrane domains\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structural analysis plus electrophysiology; interaction residues identified, single lab\",\n      \"pmids\": [\"24827085\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Filamin C (FLNC) interacts with the C-terminal domain of KCNE2 specifically under hypoxic conditions (not normoxia), as demonstrated by yeast two-hybrid screening and co-immunoprecipitation/co-localization.\",\n      \"method\": \"Yeast two-hybrid screening of cardiac cDNA library, co-localization and co-immunoprecipitation under normoxic and hypoxic conditions\",\n      \"journal\": \"Cardiovascular journal of Africa\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — co-IP/co-localization, single lab, no functional electrophysiology readout\",\n      \"pmids\": [\"26956495\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Kcne2 deletion attenuates acute myocardial infarction: Kcne2−/− mice show 40% lower infarct size and decreased apoptosis after ischemia/reperfusion injury. This is mechanistically linked to 2-fold increased GSK-3β phosphorylation (inactivation) in Kcne2−/− mice; GSK-3β inhibitor mimicked and did not further enhance cardioprotection in Kcne2−/−mice.\",\n      \"method\": \"Coronary ligation IRI model, infarct size quantification, Western blotting for GSK-3β phosphorylation, pharmacological GSK-3β inhibition (SB216763), Millar catheter cardiac function\",\n      \"journal\": \"Cardiovascular research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological epistasis plus genetic KO with mechanistic biochemical readout, single lab\",\n      \"pmids\": [\"26952045\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Kcne2 deletion in mice impairs pancreatic β-cell insulin secretion up to 8-fold and diminishes β-cell peak outward K+ current, causing type 2 diabetes. Skeletal muscle insulin receptor β and insulin receptor substrate 1 are down-regulated 2-fold by Kcne2 deletion.\",\n      \"method\": \"Kcne2 knockout mice, glucose tolerance testing, in vitro insulin secretion assay, whole-cell patch clamp in pancreatic β-cells, Western blotting\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined cellular electrophysiology phenotype and functional secretion defect, multiple orthogonal methods\",\n      \"pmids\": [\"28280005\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Decreased cardiac KCNE2 expression contributes to pathological hypertrophy via activation of calcineurin-NFAT and MAPK pathways, mediated through enhanced L-type Ca2+ channel activity (increased intracellular Ca2+ transient). KCNE2 knockdown increased calcineurin activity and nuclear NFAT levels; inhibitors of L-type Ca2+ channel (nifedipine) or calcineurin (FK506) attenuated hypertrophy. KCNE2 overexpression by ultrasound-microbubble gene transfer suppressed TAC-induced hypertrophy in vivo.\",\n      \"method\": \"Adenoviral knockdown and overexpression in neonatal rat ventricular myocytes, TAC mouse model, pharmacological inhibition, calcineurin activity assay, Western blotting, ultrasound-microbubble gene delivery\",\n      \"journal\": \"Circulation. Heart failure\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — bidirectional manipulation with multiple pathway readouts and in vivo validation, single lab\",\n      \"pmids\": [\"28611128\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The stoichiometry of KCNE2 subunits in complex with HCN channel pore-forming subunits differs by HCN isoform and is concentration-dependent. Disease-linked KCNE2 gene variants can alter this stoichiometry with functional implications.\",\n      \"method\": \"Single-molecule subunit counting (fluorescence) in heterologous expression\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — single-molecule counting is quantitative, but single lab and stoichiometry not independently validated\",\n      \"pmids\": [\"31235733\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"A conserved arginine/lysine-based motif (KSKR) in the KCNE2 proximal C-terminus is required for ER export of KCNE2 and its forward trafficking to the cell surface. This trafficking is essential for KCNE2-mediated suppression of KCNQ1 cell surface expression and current. The KCNE2 C-terminus does not appear to physically interact with KCNQ1 (C-terminus truncation did not reduce KCNE2-KCNQ1 apparent affinity), unlike KCNE1.\",\n      \"method\": \"Site-directed mutagenesis of the motif, biotinylation assays of surface expression, whole-cell electrophysiology in HEK293 cells\",\n      \"journal\": \"Channels\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis plus biochemical and electrophysiological validation, single lab\",\n      \"pmids\": [\"31679457\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Kcne2 deletion reduces pulmonary expression of Kcnq1 and Kcnb1. Kcne2 co-immunoprecipitates with Kcnq1 in mouse lungs, indicating pulmonary Kcnq1-Kcne2 channel complexes. Kcne2 deletion impairs gas exchange (reduced blood O2, increased CO2) and increases pulmonary inflammation and vascular leakage.\",\n      \"method\": \"Co-immunoprecipitation from lung tissue, Western blotting, blood gas analysis, bronchoalveolar lavage, Kcne2 knockout mice\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP from native tissue plus KO phenotype, single lab\",\n      \"pmids\": [\"31162977\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Cardiac-specific Kcne2 deletion (Kcne2CS−/−) causes dilated cardiomyopathy and terminal heart failure (median survival 28 weeks). Global Kcne2 deletion reduces gut Bacteroidales species (through achlorhydria), which correlates with improved survival. Proton-pump inhibitor omeprazole similarly altered the microbiome and delayed heart failure in Kcne2CS−/− mice, extending survival 10-fold at 44 weeks.\",\n      \"method\": \"Cardiac-specific vs global Kcne2 knockout mice, cardiac histology, microbiome profiling, pharmacological PPI treatment, survival analysis\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cardiac-specific KO with defined cardiomyopathy phenotype and pharmacological rescue via microbiome modulation, single lab\",\n      \"pmids\": [\"32584506\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Testin (encoded by TES, a focal adhesion protein) interacts with the KCNE2 intracellular C-terminal domain, identified by yeast two-hybrid screening and confirmed by co-immunoprecipitation. Testin nullifies KCNE2 effects on Kv1.5 voltage dependence and activation kinetics without affecting KCNE2 regulation of KCNQ1.\",\n      \"method\": \"Yeast two-hybrid screening, co-immunoprecipitation in vitro, whole-cell patch clamp in CHO cells\",\n      \"journal\": \"Channels\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — co-IP plus electrophysiology, single lab, in vitro system only\",\n      \"pmids\": [\"33464998\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"KCNQ1 gain-of-function mutations (R116L, V185M, P369L) that cause gingival fibromatosis/pituitary hormone deficiency act by impairing Ca2+ sensitivity of the KCNQ1-KCNE2 channel complex; normally, KCNE2 limits resting Q1E2 conductance by requiring calcified calmodulin for effective channel opening.\",\n      \"method\": \"Whole-cell patch clamp with intracellular Ca2+ manipulation, calmodulin co-expression, KCNQ1 mutagenesis in heterologous cells\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — patch clamp with defined ionic/Ca2+ manipulations and mutagenesis, single lab; defines mechanism for Q1E2 complex regulation by Ca2+/calmodulin\",\n      \"pmids\": [\"36077086\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KCNE2 (MiRP1) is a single-transmembrane β subunit that promiscuously co-assembles with multiple voltage-gated cation channel α subunits—including HERG/KCNH2, KCNQ1, HCN1-4, Kv1.5, Kv2.1, Kv4.2/4.3, KCNQ2/3, and Cav1.2—to modulate their gating kinetics, current density, protein trafficking, and surface expression; in native tissues KCNE2 is essential for gastric acid secretion (via apical KCNQ1-KCNE2 in parietal cells), thyroid iodide uptake, CSF homeostasis (via KCNQ1/KCNA3 regulation in choroid plexus), cardiac ventricular repolarization, pancreatic β-cell insulin secretion, and lung function, with S98 phosphorylation providing an additional post-translational mechanism that accelerates hERG protein degradation to reduce IKr amplitude.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"KCNE2 (MiRP1) is a single-transmembrane ancillary β subunit that promiscuously co-assembles with diverse voltage-gated cation channel α subunits to tune their gating, conductance, surface trafficking, and current density across cardiac, epithelial, neuronal, and endocrine tissues [#0, #17]. Its founding role is in cardiac repolarization, where co-assembly with HERG (KCNH2) reconstitutes native-like IKr and where multiple missense mutations (e.g. V65M, T10M, M54T) reduce IKr by accelerating inactivation or altering gating, defining the long-QT (LQT6) phenotype [#0, #4, #14], while the gain-of-function R27C variant acts through the KCNQ1-KCNE2 background current to cause familial atrial fibrillation [#9]. Beyond hERG, KCNE2 modulates an unusually broad partner set—HCN1-4 pacemaker channels [#7, #18, #28], KCNQ1 (alone and within tripartite KCNQ1-KCNE1 IKs complexes) [#8, #11], Kv1.5, Kv2.1, and Kv4 family channels [#17, #19], and the L-type Ca2+ channel Cav1.2 [#30]—through direct physical interaction at defined transmembrane and C-terminal contacts [#5, #31]. A major function is regulation of channel biogenesis and surface delivery: KCNE2 retains N-type-inactivating Kv α subunits in the early secretory pathway as a composition checkpoint [#23], requires a C-terminal KSKR motif for its own ER export [#37], and suppresses KCNQ1 surface expression, with S98 phosphorylation accelerating hERG degradation as a post-translational brake on IKr [#25]. In native epithelia, the apical KCNQ1-KCNE2 channel is essential for gastric acid secretion in parietal cells [#8, #10], thyroid iodide uptake [#26], and choroid plexus K+/Cl−/myo-inositol homeostasis via co-regulation with KCNA3 and the solute transporter SMIT1 [#24, #29]; mouse Kcne2 loss further impairs pancreatic β-cell insulin secretion to cause type 2 diabetes [#34] and disrupts pulmonary gas exchange [#38]. Cardiac-specific Kcne2 deletion produces dilated cardiomyopathy and heart failure [#39], and reduced cardiac KCNE2 drives pathological hypertrophy through enhanced Cav1.2-mediated Ca2+ entry and calcineurin-NFAT signaling [#35].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Established KCNE2's founding function—that a small accessory subunit converts HERG into native-like cardiac IKr and that its mutations cause long-QT syndrome—answering what MiRP1 contributes to a physiological current.\",\n      \"evidence\": \"Whole-cell and single-channel patch clamp of MiRP1+HERG co-expression and LQT-associated mutants in oocytes and mammalian cells\",\n      \"pmids\": [\"10219239\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and structural basis of the HERG-KCNE2 interface not resolved\", \"Whether MiRP1 is the dominant native IKr β subunit in human heart not established here\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Extended KCNE2 partner promiscuity beyond hERG to neuronal M-channel subunits, raising the question of how one β subunit modulates structurally distinct α subunits.\",\n      \"evidence\": \"Co-immunoprecipitation and whole-cell electrophysiology of KCNE2 with KCNQ2/KCNQ3 in COS cells\",\n      \"pmids\": [\"11034315\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No native neuronal demonstration of KCNQ2/3-KCNE2 complexes\", \"Physiological relevance to brain excitability untested\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Distinguished which KCNE2-induced biophysical changes actually matter for repolarization and localized part of the HERG interaction to the cyclic nucleotide binding domain.\",\n      \"evidence\": \"HERG CNBD mutagenesis, co-expression electrophysiology, and computational action potential modeling\",\n      \"pmids\": [\"11278781\", \"11440975\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct structural contact within the CNBD not mapped\", \"Modeling conclusions depend on assumed expression levels\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Defined an additional gating mechanism (accelerated inactivation) by which a KCNE2 mutation reduces IKr, broadening the molecular spectrum of LQT6.\",\n      \"evidence\": \"Whole-cell patch clamp and co-localization of V65M mutant with HERG in CHO cells\",\n      \"pmids\": [\"12185453\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Penetrance and in vivo arrhythmia link not addressed\", \"Single mutant in a heterologous background\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identified HCN pacemaker channels as physical and functional KCNE2 partners, expanding its role into cardiac automaticity and identifying the C-terminal tail as the HCN4 interaction site.\",\n      \"evidence\": \"Two-electrode and patch clamp in oocytes/CHO cells plus yeast two-hybrid for HCN4; AP-clamp analysis of LQT6 mutants on HERG\",\n      \"pmids\": [\"12856183\", \"12923204\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Native HCN-KCNE2 association not yet shown\", \"Stoichiometry of the interaction unknown\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Confirmed native cardiac HCN2-KCNE2 complexes and discovered the gain-of-function R27C variant acting through the KCNQ1-KCNE2 background current, linking KCNE2 to atrial fibrillation as distinct from LQT.\",\n      \"evidence\": \"Co-IP of endogenous HCN2 and KCNE2 in neonatal rat myocytes; AF-kindred sequencing with electrophysiology testing R27C against multiple partners\",\n      \"pmids\": [\"15292247\", \"15368194\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How a single residue selectively affects KCNQ1 but not HERG/HCN currents not mechanistically explained\", \"In vivo AF causation not demonstrated\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Established the apical gastric KCNQ1-KCNE2 channel and its regulation by acid pH, PIP2, cAMP, and purinergic signaling, defining KCNE2's first epithelial physiological context.\",\n      \"evidence\": \"In situ hybridization, confocal immunofluorescence, and patch clamp in parietal cells and COS cells\",\n      \"pmids\": [\"15579540\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct coupling to H+,K+-ATPase activity not established\", \"In vivo requirement not yet tested at this stage\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrated in vivo that KCNE2 is essential for gastric acid secretion with a gene-dose effect, converting in vitro complex assembly into a defined organ-level physiological requirement.\",\n      \"evidence\": \"Targeted Kcne2 knockout mice with acid-secretion measurement, histology, and KCNQ1 immunolocalization\",\n      \"pmids\": [\"16754665\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Secondary systemic consequences of achlorhydria not yet mapped\", \"Mechanism of abnormal KCNQ1 distribution unclear\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Showed KCNE2 participates in native cardiac IKs as a tripartite KCNQ1-KCNE1-KCNE2 complex and modulates Kv4.3 Ito, reinforcing multi-channel cardiac regulation.\",\n      \"evidence\": \"Co-IP and immunocytochemistry in adult rat ventricular myocytes; patch clamp of Kv4.3 in COS-7 cells\",\n      \"pmids\": [\"17161791\", \"17259113\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry within the tripartite complex unresolved\", \"Kv4.3 modulation rests on single-method electrophysiology\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Revealed KCNE2's distinctive trafficking behavior versus KCNE1 and provided the first gating mechanism for the reduced-penetrance T10M arrhythmia variant.\",\n      \"evidence\": \"Co-IP, surface labeling, Brefeldin A and ER-retention engineering for trafficking; whole-cell clamp of T10M in CHO cells\",\n      \"pmids\": [\"17895974\", \"18006462\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional significance of extracellular/vesicular KCNE2 pool unknown\", \"Trafficking differences not linked to a defined sorting determinant yet\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Identified Kv1.5 as a novel in vivo KCNE2 partner and showed KCNE2 controls Kv1.5 protein levels and intercalated-disc trafficking, while structural spectroscopy began defining MiRP1 domain architecture.\",\n      \"evidence\": \"Kcne2 knockout mice with myocyte electrophysiology and native co-IP; FTIR/CD spectroscopy of synthetic MiRP1 peptides; Kv4.3/KChIP2 complex electrophysiology\",\n      \"pmids\": [\"18603586\", \"18221016\", \"18501111\", \"18536731\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which KCNE2 stabilizes mature Kv1.5 protein not defined\", \"Peptide spectroscopy does not represent the native folded protein\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Consolidated KCNE2 as a broad single-channel-level modulator of all four HCN isoforms, Kv2.1, and Kv4.3, and showed it can dynamically substitute into IKs complexes and traffic independently of KCNQ1.\",\n      \"evidence\": \"Whole-cell and single-channel recordings, membrane fractionation, native-tissue co-IP (Kv2.1), pulse-chase and biotinylation trafficking assays, myocyte electrophysiology\",\n      \"pmids\": [\"19429827\", \"19219384\", \"19372218\", \"20042375\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Tissue-specific partner selection rules not established\", \"How one β subunit produces opposite effects on different α subunits unexplained\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Defined KCNE2 as a secretory-pathway checkpoint that retains N-type-inactivating Kv subunits and uncovered choroid plexus epithelial functions controlling CSF ion homeostasis.\",\n      \"evidence\": \"Electrophysiology, co-IP, immunofluorescence, Brefeldin A and dynamin-inhibitor dissection; Kcne2 KO with CPe patch clamp, pharmacology, and CSF ion measurement\",\n      \"pmids\": [\"21943416\", \"21943417\", \"21859894\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular machinery executing ER retention not identified\", \"Link between altered CPe trafficking and CSF chloride change not fully mechanistic\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Provided rigorous NMR backbone assignments and helical secondary-structure mapping of human MiRP1, establishing a structural framework for interpreting interaction studies.\",\n      \"evidence\": \"Solution NMR triple-resonance assignment and CD spectroscopy of E. coli-expressed MiRP1 in detergent micelles\",\n      \"pmids\": [\"21087668\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No full tertiary structure or channel-bound conformation\", \"No functional validation in this study\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Extended the apical KCNQ1-KCNE2 channel's physiological role to thyroid iodide uptake and dissected which transport step requires it, and defined neuronal HCN dysfunction upon Kcne2 loss.\",\n      \"evidence\": \"In vivo PET iodide imaging, in vitro uptake assays, and Kcne2 KO/pharmacology for thyroid; KO brain-slice patch clamp and co-IP for thalamocortical HCN\",\n      \"pmids\": [\"22549510\", \"22880098\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Negative brain co-IP leaves the neuronal HCN mechanism likely indirect and undefined\", \"Cell type mediating iodide retention not pinpointed\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Identified S98 phosphorylation as a post-translational mechanism by which KCNE2 controls hERG protein stability and IKr amplitude.\",\n      \"evidence\": \"Phospho-specific antibody, adenoviral manipulation, Western blotting, and immunofluorescence in adult cardiac myocytes\",\n      \"pmids\": [\"22180649\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Kinase responsible for S98 phosphorylation not identified\", \"Degradation pathway targeting hERG not defined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Linked the KCNQ1-KCNE2 channel to solute-transporter regulation and mapped the precise transmembrane interaction residues distinguishing KCNE2 from KCNE1, and added Cav1.2 as a physical KCNE2 partner.\",\n      \"evidence\": \"Native-tissue co-IP, myo-inositol uptake assays, CSF metabolomics and seizure rescue; solution NMR plus electrophysiology of KCNE2-KCNQ1 contacts; Cav1.2 co-IP, domain deletion and patch clamp\",\n      \"pmids\": [\"24595108\", \"24827085\", \"24681347\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How a constitutive K+ channel mechanistically inhibits a Na+-coupled transporter not fully resolved\", \"Cav1.2 regulation mechanism beyond the N-terminal inhibitory module untested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Connected KCNE2 loss to altered cellular survival signaling and a hypoxia-dependent cytoskeletal interaction, broadening its role beyond channel gating.\",\n      \"evidence\": \"Ischemia/reperfusion in Kcne2 KO mice with GSK-3β phospho-analysis and pharmacological epistasis; yeast two-hybrid and condition-dependent co-IP for filamin C\",\n      \"pmids\": [\"26952045\", \"26956495\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking KCNE2 to GSK-3β phosphorylation unknown\", \"Filamin C interaction lacks functional electrophysiological readout\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Established KCNE2's roles in β-cell insulin secretion and as a brake on Cav1.2-driven calcineurin-NFAT hypertrophic signaling, extending its physiology to metabolic and remodeling pathways.\",\n      \"evidence\": \"Kcne2 KO glucose tolerance, insulin assays and β-cell patch clamp; bidirectional KCNE2 manipulation with TAC model, calcineurin assays, and in vivo gene delivery\",\n      \"pmids\": [\"28280005\", \"28611128\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Channel partner mediating β-cell K+ current loss not defined\", \"Direct vs indirect contribution of Cav1.2 modulation to hypertrophy not separated\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Resolved isoform- and concentration-dependent KCNE2:HCN stoichiometry, defined the KSKR ER-export motif required for KCNE2 forward trafficking, and added pulmonary KCNQ1-KCNE2 complexes governing gas exchange.\",\n      \"evidence\": \"Single-molecule subunit counting; trafficking motif mutagenesis with biotinylation and electrophysiology; lung-tissue co-IP and Kcne2 KO blood-gas analysis\",\n      \"pmids\": [\"31235733\", \"31679457\", \"31162977\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of variable stoichiometry in native tissue untested\", \"Trafficking factors recognizing the KSKR motif unidentified\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Demonstrated that cardiac-specific KCNE2 loss causes dilated cardiomyopathy and that its systemic loss reshapes the gut microbiome via achlorhydria, linking organ-level and microbial axes to heart failure progression.\",\n      \"evidence\": \"Cardiac-specific vs global Kcne2 KO with histology, microbiome profiling, PPI treatment, and survival analysis\",\n      \"pmids\": [\"32584506\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Channel partner driving cardiomyopathy in cardiac-specific KO not pinpointed\", \"Mechanism by which microbiome changes modulate cardiac survival unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified testin as a C-terminal KCNE2 partner that selectively reverses KCNE2 modulation of Kv1.5 but not KCNQ1, revealing partner-specific regulatory layering.\",\n      \"evidence\": \"Yeast two-hybrid, co-IP, and whole-cell patch clamp in CHO cells\",\n      \"pmids\": [\"33464998\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"In vitro system only, no native-tissue confirmation\", \"Physiological context of testin-KCNE2 regulation untested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined how KCNE2 imposes Ca2+/calmodulin dependence on the KCNQ1-KCNE2 complex, providing the mechanism by which KCNQ1 gain-of-function mutations cause disease through this complex.\",\n      \"evidence\": \"Whole-cell patch clamp with intracellular Ca2+ and calmodulin manipulation and KCNQ1 mutagenesis in heterologous cells\",\n      \"pmids\": [\"36077086\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of Ca2+/calmodulin gating within the complex not resolved\", \"Tissue-specific relevance of this regulatory mode not tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a single small β subunit selects among many α-subunit partners in a tissue-specific manner, and the structural basis for its opposing effects on different channels, remains unresolved.\",\n      \"evidence\": \"No discovery in the timeline reconciles the partner-selection rules or provides a channel-bound full structure\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No high-resolution structure of any KCNE2-channel complex\", \"Determinants of tissue-specific partner choice unknown\", \"Rules governing gain- vs loss-of-function modulation across partners undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 7, 17, 18, 19, 30]},\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [8, 24, 26]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [32, 40]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [8, 11, 20, 24]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [13, 23, 37]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [1, 27]},\n      {\"term_id\": \"R-HSA-397014\", \"supporting_discovery_ids\": [0, 17]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [8, 24, 26]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [23, 37]}\n    ],\n    \"complexes\": [\n      \"KCNQ1-KCNE2 channel\",\n      \"HERG(KCNH2)-KCNE2 (IKr) channel\",\n      \"KCNQ1-KCNE1-KCNE2 (IKs) tripartite channel\",\n      \"HCN-KCNE2 pacemaker channel\"\n    ],\n    \"partners\": [\n      \"KCNH2\",\n      \"KCNQ1\",\n      \"HCN4\",\n      \"HCN2\",\n      \"KCNA5\",\n      \"KCNB1\",\n      \"CACNA1C\",\n      \"TES\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}