{"gene":"KCNA5","run_date":"2026-04-28T18:06:54","timeline":{"discoveries":[{"year":1991,"finding":"KCNA5 (HK2/hPCN1) was molecularly cloned from human ventricle and insulinoma/islet tissue, and functional expression in Xenopus oocytes demonstrated a voltage-dependent, slowly inactivating outward K+ current sensitive to low concentrations of 4-aminopyridine, establishing it as a Shaker-family delayed rectifier potassium channel.","method":"cDNA cloning, Northern blot, functional expression in Xenopus oocytes with two-electrode voltage clamp","journal":"FASEB journal / Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 1 — original molecular cloning with functional reconstitution in two independent studies","pmids":["2001794","1986382"],"is_preprint":false},{"year":1993,"finding":"Stable mammalian cell expression of Kv1.5 (HK2) revealed a rapidly activating, slowly inactivating delayed rectifier current with well-defined gating kinetics (activation midpoint ~−14 mV, slow biexponential inactivation with voltage-independent time constants ~240 ms and ~2,700 ms), K+ selectivity, and 4-AP sensitivity, establishing the channel's intrinsic biophysical properties.","method":"Stable transfection in mouse L-cells, whole-cell patch-clamp electrophysiology","journal":"The Journal of general physiology","confidence":"High","confidence_rationale":"Tier 1 — rigorous in vitro reconstitution with comprehensive biophysical characterization","pmids":["8505626"],"is_preprint":false},{"year":1995,"finding":"Kv1.5 protein is highly localized at intercalated disk regions in human atrial and ventricular myocytes, as determined by colocalization with connexin and N-cadherin; NH2-terminal antibodies additionally stained vascular smooth muscle, suggesting epitope accessibility and possibly different channel structure in cardiac versus vascular myocytes.","method":"Immunofluorescence with epitope-specific antibodies in explanted human cardiac tissue, confocal colocalization","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — direct localization experiment in native tissue with two distinct antibodies and colocalization controls","pmids":["7615797"],"is_preprint":false},{"year":1996,"finding":"Kv1.5 (hKv1.5) directly associates with Src tyrosine kinase via the channel's proline-rich N-terminal sequences and the SH3 domain of Src; this interaction results in tyrosine phosphorylation of hKv1.5 and suppression of channel current in cells co-expressing v-Src, establishing a signaling complex between a potassium channel and a protein tyrosine kinase.","method":"Co-immunoprecipitation from transfected cells and human myocardium, SH3 domain pull-down, whole-cell patch clamp in v-Src co-expressing cells","journal":"Science","confidence":"High","confidence_rationale":"Tier 1-2 — reciprocal co-IP in native tissue plus functional electrophysiology, replicated in heterologous system","pmids":["8953041"],"is_preprint":false},{"year":1996,"finding":"Endogenous Kvβ2.1 co-assembles with transfected hKv1.5 α-subunit and shifts the midpoints of activation and inactivation by ~14 mV and ~12 mV toward hyperpolarized potentials, respectively, and increases the extent of slow inactivation, explaining cell-line-dependent differences in Kv1.5 current kinetics.","method":"Molecular cloning, immunopurification, Western blot detection of endogenous Kvβ2.1; functional co-expression in HEK293 cells with patch clamp","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — biochemical identification of endogenous subunit assembly combined with functional rescue reconstitution","pmids":["8576199"],"is_preprint":false},{"year":1998,"finding":"Ketoconazole directly blocks both HERG and Kv1.5 channels heterologously expressed in Xenopus oocytes, with IC50 values of ~49 µM and ~107 µM, respectively; the mechanism of block differs between the two channels, and combined application with terfenadine at IC50 concentrations produces additive rather than competitive block.","method":"Heterologous expression in Xenopus oocytes, two-microelectrode voltage-clamp pharmacology","journal":"The Journal of pharmacology and experimental therapeutics","confidence":"High","confidence_rationale":"Tier 1 — direct pharmacological characterization in reconstituted system with mechanistic analysis","pmids":["9694927"],"is_preprint":false},{"year":1999,"finding":"A 27-kDa Kv1.5 repressor element binding factor (KBF) was identified in GH3 and cardiac nuclear extracts that specifically binds a 52-bp dinucleotide-repetitive silencer element (KRE) in the Kv1.5 promoter; this KBF–KRE interaction may regulate the cardiac- and GH3-specific expression of the Kv1.5 gene.","method":"Electromobility gel shift assay (EMSA), magnetic DNA affinity purification, UV cross-linking","journal":"Circulation research","confidence":"Medium","confidence_rationale":"Tier 2 — direct biochemical identification of DNA-binding protein, single lab","pmids":["10222341"],"is_preprint":false},{"year":2000,"finding":"α-actinin-2 physically interacts with Kv1.5 via the channel's N-terminus/core region, as shown by in vitro co-immunoprecipitation and co-expression in HEK cells; co-localization at the membrane was observed, and disruption of the actin cytoskeleton or antisense knockdown of α-actinin-2 modulated Kv1.5 ion and gating current density.","method":"In vitro translation co-immunoprecipitation, co-expression in HEK cells, confocal colocalization, actin cytoskeleton disruption, antisense knockdown with patch clamp","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (biochemical interaction + functional consequence)","pmids":["10812072"],"is_preprint":false},{"year":2000,"finding":"Protein tyrosine phosphatase epsilon (PTP epsilon) dephosphorylates Kv1.5 in sciatic nerve tissue and Schwann cells; loss of PTP epsilon leads to hyperphosphorylation of Kv1.5 (and Kv2.1) and increased delayed-rectifier K+ channel activity, accompanied by hypomyelination, establishing PTP epsilon as a negative regulator of Kv1.5 channel activity in vivo.","method":"PTP epsilon knockout mice, Western blot for tyrosine phosphorylation, Xenopus oocyte co-expression electrophysiology, substrate-trapping co-IP with Kv2.1","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1-2 — genetic knockout with biochemical and functional validation in native tissue","pmids":["10921884"],"is_preprint":false},{"year":2001,"finding":"SAP97 co-immunoprecipitates with Kv1.5 in COS-7 cells and co-localizes with Kv1.5 at intercalated disks and lateral membranes in cardiac myocytes; SAP97–Kv1.5 interaction requires the three C-terminal residues (TDL) of Kv1.5; co-expression with SAP97 augments Kv1.5-encoded outward K+ currents in Xenopus oocytes.","method":"Co-immunoprecipitation from transfected COS-7 cells, immunocytochemistry in cardiac myocytes, C-terminal mutagenesis, Xenopus oocyte functional expression","journal":"American journal of physiology. Heart and circulatory physiology","confidence":"High","confidence_rationale":"Tier 2 — reciprocal biochemical interaction with mutagenesis confirmation and functional readout","pmids":["11709425"],"is_preprint":false},{"year":2003,"finding":"Mutagenesis of residues Thr-479, Thr-480, Val-505, Ile-508, and Val-512 in the pore helix and S6 segment of Kv1.5 drastically reduced affinity for the channel blocker S0100176 (e.g., T480A increased IC50 362-fold), identifying these inner-cavity residues as the drug-binding site and providing a molecular basis for open-channel block of Kv1.5.","method":"Ala-scanning mutagenesis, heterologous expression in Xenopus oocytes, voltage-clamp pharmacology, homology modeling based on KcsA crystal structure","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — systematic mutagenesis with structural modeling, multiple mutants tested","pmids":["14578345"],"is_preprint":false},{"year":2003,"finding":"SAP97 increases hKv1.5 currents through an indirect mechanism dependent on the Kv1.5 N-terminus; deletion of the N-terminus abolished SAP97-mediated current increase, whereas deletion of the C-terminal PDZ-binding motif had no effect; no direct physical interaction between SAP97 and Kv1.5 was detected in cardiac myocytes or transfected HEK cells.","method":"N- and C-terminal deletion mutants, transfection in HEK cells, co-immunoprecipitation, yeast two-hybrid, confocal microscopy, patch clamp","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 — multiple methods but indirect mechanism without identified intermediary","pmids":["12860415"],"is_preprint":false},{"year":2004,"finding":"Overexpressed human Kv1.5 in pulmonary artery smooth muscle cells (PASMC) generates a 15-pS single-channel current and large whole-cell K+ current; ET-1, nicotine, bepridil, and correolide each significantly and reversibly reduced Kv1.5 currents, and nicotine/bepridil accelerated inactivation kinetics, identifying specific modulators of the channel.","method":"Heterologous overexpression (KCNA5) in PASMC and cell lines, single-channel and whole-cell patch clamp, pharmacology","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 1 — single-channel and whole-cell recordings with pharmacological characterization","pmids":["17267549"],"is_preprint":false},{"year":2004,"finding":"Overexpression of KCNA5 in COS-7 cells and rat PASMC significantly increases Kv current (IKV) and enhances staurosporine-induced caspase-3 activation and apoptosis; apoptotic volume decrease (AVD) is accelerated, and 4-AP blockade of KCNA5 channels inhibits staurosporine-induced apoptosis, demonstrating that K+ efflux through Kv1.5 channels promotes apoptotic cell shrinkage and apoptosis.","method":"Transient transfection of KCNA5, whole-cell patch clamp, caspase-3 activity assay, flow cytometry for apoptosis, pharmacological blockade with 4-AP","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 2 — multiple cell types, pharmacological rescue, defined cellular phenotype","pmids":["15140747"],"is_preprint":false},{"year":2004,"finding":"Kv1.5 (along with Kv2.1) accounts for virtually all O2-sensitive current in resistance pulmonary artery smooth muscle cells; intracellular anti-Kv1.5 antibodies inhibit correolide-sensitive IK, and anti-Kv1.5 plus anti-Kv2.1 additively depolarize resistance PASMCs and inhibit hypoxic depolarization, establishing Kv1.5 as the predominant O2-sensitive Kv channel mediating hypoxic pulmonary vasoconstriction.","method":"Intracellular antibody application, patch clamp in isolated resistance PASMCs, selective pharmacology (correolide), immunohistochemistry","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 — intracellular antibody experiments plus pharmacological dissection in native cells","pmids":["15217912"],"is_preprint":false},{"year":2005,"finding":"Kv1.5 surface expression is regulated by retrograde trafficking via the dynein motor complex: disruption of dynein-dynactin (p50/dynamitin overexpression), inhibition of endocytosis (dynamin inhibitory peptide), or microtubule depolymerization (nocodazole) all increase Kv1.5 current density and plasma membrane localization; co-immunoprecipitation demonstrated direct Kv1.5–dynein interaction requiring an intact SH3-binding domain in the Kv1.5 N-terminus.","method":"Dominant-negative dynein overexpression, dynamin inhibitory peptide, nocodazole treatment, co-immunoprecipitation, Proteinase K surface accessibility assay, confocal imaging, patch clamp","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods, direct biochemical interaction, functional consequence","pmids":["16051887"],"is_preprint":false},{"year":2005,"finding":"Acute hypoxia selectively inhibits Kv1.5 (KCNA5) channel activity in PASMC but not in mesenteric artery smooth muscle cells (MASMC), HEK-293, or COS-7 cells; overexpression of KCNA5 in rat MASMC did not confer hypoxia sensitivity, whereas overexpression in PASMC did, demonstrating that a PASMC-specific hypoxia-sensitive mechanism is required for Kv1.5 inhibition.","method":"Heterologous KCNA5 overexpression in multiple cell types, whole-cell patch clamp under varying PO2","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 2 — cell-type-specific transfer-of-function experiment with multiple controls","pmids":["16236819"],"is_preprint":false},{"year":2005,"finding":"Kv1.5 protein is degraded by the ubiquitin-proteasome pathway with a half-life of ~6.7 h; proteasome inhibitors (MG132, ALLN) prolong the half-life, increase Kv1.5 protein levels and ubiquitinated forms, accumulate channel in the ER/Golgi, and increase IKur currents; lysosomal inhibitors have no effect, and this proteasomal degradation pathway was confirmed in rat atrial cells for endogenous Kv1.5.","method":"Pulse-chase analysis, immunofluorescence, proteasome/lysosomal inhibitor pharmacology, patch clamp, Western blot for ubiquitinated forms","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 2 — multiple inhibitors and pulse-chase kinetics, confirmed in native cells","pmids":["16185660"],"is_preprint":false},{"year":2005,"finding":"C-terminal polymorphisms P532L and R578K in KCNA5 produce near-normal channel gating but confer striking resistance to quinidine block (IC50 increased from 8.4 µM to 133 µM and 54 µM, respectively), identifying the C-terminus as a region modulating drug sensitivity.","method":"SSCP/direct sequencing for variant identification, patch-clamp pharmacology in transfected CHO cells","journal":"Clinical pharmacology and therapeutics","confidence":"High","confidence_rationale":"Tier 1 — functional mutagenesis with quantitative IC50 determination","pmids":["15735608"],"is_preprint":false},{"year":2006,"finding":"Kv1.5 does not co-localize with caveolin-3 in rat and canine atrial or ventricular myocytes (co-localization <12%) and does not associate with low-density raft fractions in HEK293 cells, while co-immunoprecipitation shows Kv1.5 associates with α-actinin but not caveolin-3, demonstrating that Kv1.5 resides outside caveolae in cardiac myocytes.","method":"Co-immunoprecipitation, sucrose-gradient fractionation, wide-field deconvolution microscopy, immunoelectron microscopy","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal localization methods in native cardiac tissue","pmids":["17054951"],"is_preprint":false},{"year":2006,"finding":"Kv1.3/Kv1.5 heterotetrameric channels are expressed in macrophages with variable Kv1.3/Kv1.5 stoichiometry across mononuclear phagocyte subtypes; the presence of Kv1.5 in the complex confers resistance to Kv1.3-specific pharmacological agents, compromising the efficacy of Kv1.3-targeted treatments for immune modulation.","method":"Patch-clamp electrophysiology, pharmacological profiling of heterotetrameric channels in macrophage subsets","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — functional pharmacological characterization, single lab","pmids":["17157812"],"is_preprint":false},{"year":2007,"finding":"SUMO-1, -2, and -3 modify Kv1.5 at two membrane-proximal cytoplasmic consensus sites; Kv1.5 interacts with the SUMO-conjugating enzyme Ubc9 in vivo; purified recombinant Kv1.5 is SUMOylated in a minimal in vitro reaction; SUMO-specific proteases SENP2 and Ulp1 deconjugate SUMO from Kv1.5; loss of SUMOylation (site mutations or SENP2 co-expression) causes a ~15 mV hyperpolarizing shift in steady-state inactivation without altering activation, establishing SUMOylation as a post-translational modifier that selectively tunes Kv1.5 inactivation gating.","method":"In vivo SUMOylation assays, in vitro reconstituted SUMOylation, co-IP with Ubc9, site-directed mutagenesis of SUMO consensus sites, SENP2 co-expression, whole-cell patch clamp","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution plus mutagenesis plus functional electrophysiology, multiple SUMO isoforms tested","pmids":["17261810"],"is_preprint":false},{"year":2007,"finding":"Membrane cholesterol depletion by methyl-β-cyclodextrin (MCD) causes redistribution of Kv1.5 from cholesterol-enriched clusters into larger clusters dispersed across the plasma membrane, increasing IKur current density; Kv1.5 subunits co-fractionate with low-density sucrose gradient fractions distinct from caveolae, indicating that Kv1.5 localizes to non-caveolar cholesterol-rich microdomains whose disruption augments channel activity.","method":"Methyl-β-cyclodextrin cholesterol depletion, sucrose-gradient fractionation, live-cell confocal imaging of GFP-Kv1.5, whole-cell patch clamp in atrial myocytes and neonatal cardiomyocytes","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 2 — direct live-cell imaging of redistribution correlated with functional current change, multiple techniques","pmids":["17525113"],"is_preprint":false},{"year":2007,"finding":"S-acylation (palmitoylation) of Kv1.5 via hydroxylamine-sensitive thioester bonds on both N- and C-terminal cysteines is required for normal channel surface expression; pharmacological inhibition of S-acylation reduces surface expression, accumulates channel in intracellular compartments, and targets it for proteasomal degradation; C-terminal cysteines govern S-acylation, and mutation of intracellular cysteines paradoxically increases surface expression, suggesting that fatty acylation acts as a quality-control step.","method":"Hydroxylamine sensitivity assay for thioester bonds, pharmacological S-acylation inhibition, proteasome inhibitor rescue, time-course surface expression analysis, confocal imaging","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 2 — multiple pharmacological approaches with defined mechanistic readouts","pmids":["17344312"],"is_preprint":false},{"year":2007,"finding":"Caveolin-1 and -3 are required for targeting Kv1.5 to low-density detergent-resistant lipid raft fractions; in cells lacking endogenous caveolin, Kv1.5 association with rafts requires exogenous caveolin co-expression; caveolin-trafficking mutants sequester Kv1.5 in intracellular compartments; wild-type caveolin-1 co-expression induces depolarizing shifts in Kv1.5 activation and inactivation analogous to high membrane cholesterol, indicating caveolin modulates Kv1.5 function by regulating its trafficking to cholesterol-rich microdomains.","method":"Sucrose density gradient fractionation, co-immunoprecipitation (channel-caveolin complex), dominant-negative caveolin trafficking mutants, patch-clamp electrophysiology","journal":"Molecular pharmacology","confidence":"High","confidence_rationale":"Tier 2 — biochemical interaction plus trafficking mutant phenotype plus functional gating changes","pmids":["18045854"],"is_preprint":false},{"year":2007,"finding":"The mitochondria-ROS-HIF-1α-Kv1.5 pathway constitutes an O2-sensing mechanism in PASMCs; decreased mitochondrial ROS in PAH creates a pseudohypoxic state that activates HIF-1α and down-regulates Kv1.5 expression, contributing to PASMC depolarization, Ca2+ influx, and the proliferative/apoptosis-resistant phenotype; dichloroacetate (PDK inhibitor) corrects mitochondrial abnormalities and restores Kv1.5 expression in experimental PAH.","method":"Fawn-hooded rat model of PAH, dichloroacetate treatment, ROS measurement, HIF-1α manipulation, Kv1.5 expression analysis, patch clamp","journal":"American journal of physiology. Heart and circulatory physiology","confidence":"High","confidence_rationale":"Tier 2 — genetic animal model plus pharmacological rescue with pathway validation","pmids":["18083891"],"is_preprint":false},{"year":2008,"finding":"After internalization, Kv1.5 is rapidly trafficked through Rab5-positive early endosomes and Rab4-positive recycling endosomes; dominant-negative Rab5, Rab4, Rab7, and Rab11 constructs all increase Kv1.5 current density; a fraction of internalized channels traffics to Rab7-positive late endosomes for degradation; Rab4 mediates rapid recycling back to the plasma membrane, establishing a post-internalization trafficking itinerary for the channel.","method":"Dominant-negative Rab GTPase expression, colocalization with Rab-positive endosome markers, whole-cell patch clamp","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 2 — systematic dominant-negative approach across four Rab GTPases with functional readout","pmids":["18755741"],"is_preprint":false},{"year":2008,"finding":"SAP97 overexpression in cardiac myocytes clusters endogenous Kv1.5 subunits at myocyte–myocyte contacts, reduces lateral mobility of GFP-Kv1.5 as measured by FRAP, and increases IKur current density (~74% increase) and single-channel number; in CHO cells, SAP97 organizes freely mobile Kv1.5 into poorly mobile plaque-like clusters, establishing that SAP97 retains and immobilizes Kv1.5 in the plasma membrane to increase functional channel expression.","method":"Adenovirus-mediated SAP97 overexpression in neonatal cardiomyocytes, FRAP of GFP-Kv1.5, cell-attached patch clamp, whole-cell patch clamp, immunocytochemistry","journal":"American journal of physiology. Heart and circulatory physiology","confidence":"High","confidence_rationale":"Tier 2 — FRAP mobility measurements plus functional current analysis, multiple cell types","pmids":["18245566"],"is_preprint":false},{"year":2008,"finding":"Kv1.5 in macrophages does not target to lipid rafts, whereas Kv1.3/Kv1.5 heteromers in transfected HEK-293 cells do associate with rafts; LPS-induced macrophage activation increases the Kv1.3/Kv1.5 ratio and caveolin expression, redirecting Kv1.5 to lipid rafts; Kvβ2.1 co-expression impairs Kv1.5 raft targeting, and a Cav3(DGV) mutant sequesters Kv1.5 in intracellular vesicles, demonstrating that Kv1.5 membrane microdomain targeting is regulated by partner protein stoichiometry.","method":"Sucrose density gradient fractionation, cholesterol-depletion experiments, confocal microscopy, dominant-negative caveolin-3 mutant expression, LPS macrophage activation","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple methods but complex system with cell-type-dependent outcomes","pmids":["18668522"],"is_preprint":false},{"year":2008,"finding":"FHL1 (four-and-a-half LIM protein 1) was identified as a Kv1.5 binding partner by GST-KCNA5 C-terminal pull-down from human atrium followed by mass spectrometry; co-immunoprecipitation confirmed the interaction in human atrium and CHO cells; FHL1 co-expression markedly increased Kv1.5 current density, shifted activation to more positive potentials, and enhanced slow inactivation extent and speed, identifying FHL1 as a key regulatory component of the IKur complex.","method":"GST pull-down from human atrium, mass spectrometry identification, co-immunoprecipitation, confocal colocalization, whole-cell patch clamp in CHO cells","journal":"Cardiovascular research","confidence":"High","confidence_rationale":"Tier 2 — proteomic discovery confirmed by reciprocal co-IP in native tissue and functional electrophysiology","pmids":["18281375"],"is_preprint":false},{"year":2008,"finding":"Hypoxia suppresses Kv1.5 channel expression in rat pulmonary artery smooth muscle cells via the 15-lipoxygenase/15-HETE pathway; pharmacological inhibition of 15-LOX rescued Kv1.5 mRNA and protein expression under hypoxia and partially restored IKV; exogenous 15-HETE mimicked hypoxia-induced Kv1.5 downregulation and current inhibition, establishing a lipid-mediated mechanism for hypoxic Kv1.5 suppression.","method":"15-LOX inhibitor pharmacology, Kv1.5 mRNA/protein expression analysis, whole-cell patch clamp in PASMC, exogenous 15-HETE application","journal":"Prostaglandins & other lipid mediators","confidence":"Medium","confidence_rationale":"Tier 2 — pharmacological pathway dissection with expression and functional data, single lab","pmids":["18984061"],"is_preprint":false},{"year":2009,"finding":"T1 domain mutations G182R and E211D in KCNA5 (found in IPAH patients) produce functional channels with accelerated inactivation at more hyperpolarized potentials; mutant channel protein is present predominantly in immature glycosylated form, reduced in expression, and retained intracellularly rather than trafficked to the plasma membrane, demonstrating that the T1 domain regulates both Kv1.5 inactivation kinetics and subcellular localization.","method":"Site-directed mutagenesis, whole-cell patch clamp in HEK-293 and COS-1 cells, Western blot for glycosylation state, immunofluorescence for subcellular localization","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 1-2 — mutagenesis combined with biophysical and biochemical characterization","pmids":["20018952"],"is_preprint":false},{"year":2009,"finding":"Acute hypoxia selectively inhibits Kv1.5 (KCNA5) current in PASMC but not MASMC; KCNA5 overexpression in PASMC confers hypoxia sensitivity to the overexpressed current, whereas overexpression in MASMC, HEK, or COS cells does not, confirming that a PASMC-specific hypoxia-sensing mechanism is required and contributes to intracellular Ca2+ homeostasis regulation during hypoxia.","method":"KCNA5 overexpression, whole-cell patch clamp at varying PO2, comparison across cell types","journal":"Annals of the New York Academy of Sciences","confidence":"Medium","confidence_rationale":"Tier 2 — replication of cell-type specificity across multiple cell types, single group","pmids":["19845612"],"is_preprint":false},{"year":2010,"finding":"A novel KCNA5 mutation deleting 11 amino acids in the N-terminal proline-rich SH3-binding domain causes ~60% loss-of-function in IKur and exerts dominant-negative effects on wild-type Kv1.5 current; pretreatment with the Src inhibitor PP2 prevented v-Src tyrosine kinase from suppressing wild-type Kv1.5 current by ~90%, whereas the mutant channel was unresponsive to v-Src, implicating tyrosine kinase signaling through the SH3-binding domain as a regulatory mechanism.","method":"Site-directed mutagenesis, whole-cell patch clamp in transfected cells, Src kinase inhibitor (PP2) pharmacology, dominant-negative analysis","journal":"Heart rhythm","confidence":"High","confidence_rationale":"Tier 1-2 — loss-of-function mutagenesis with mechanistic pathway dissection using kinase inhibitor","pmids":["20638934"],"is_preprint":false},{"year":2012,"finding":"Mutations E48G, A305T, and D322H in Kv1.5 (found in lone AF patients) display preserved surface expression and gain-of-function in patch-clamp studies; mutations Y155C, D469E, and P488S display decreased surface expression and loss-of-function; establishing that both gain- and loss-of-function mutations in KCNA5 are associated with atrial fibrillation.","method":"Confocal microscopy for surface expression, whole-cell patch-clamp electrophysiology in transfected cells","journal":"European heart journal","confidence":"High","confidence_rationale":"Tier 2 — direct biophysical characterization of multiple mutations with localization analysis","pmids":["23264583"],"is_preprint":false},{"year":2012,"finding":"The C-terminal domain of Kv1.5 (residues Arg543–Val583) is required for interaction with Kvβ-subunits in a pyridine nucleotide-dependent manner: NADPH accelerates Kv1.5-Kvβ3-mediated inactivation while NADP+ decreases inactivation and reverses the Kvβ2 activation shift; deletion of the C-terminus abolishes these nucleotide-dependent effects; a GST-C-terminal fusion protein binds Kvβ2:NADPH with higher affinity than Kvβ2:NADP+.","method":"C-terminal deletion mutagenesis, co-expression with Kvβ2/Kvβ3, whole-cell patch clamp with intracellular NADPH/NADP+ in pipette solution, GST pull-down from mouse brain lysates, structural analysis","journal":"Pflugers Archiv","confidence":"High","confidence_rationale":"Tier 1-2 — mutagenesis combined with biochemical pull-down and functional electrophysiology","pmids":["22426702"],"is_preprint":false},{"year":2015,"finding":"Kv1.5 channel function is required for coronary metabolic dilation: Kv1.5-null mice show impaired myocardial blood flow increase during cardiac stress despite higher cardiac work, and isolated arteries from null mice have impaired relaxation to H2O2 (a reactive oxygen species involved in redox-dependent vasodilation) but normal responses to adenosine and acetylcholine; smooth-muscle-specific rescue of Kv1.5 in null mice restores metabolic dilation, directly linking Kv1.5 in vascular smooth muscle to redox-sensitive coronary flow regulation.","method":"Kv1.5 knockout mice, inducible smooth-muscle-specific Kv1.5 re-expression, in vivo myocardial blood flow measurement, tissue O2 tension, isolated artery pharmacology","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 — genetic null + tissue-specific rescue establishes cell-type-specific mechanism","pmids":["26224794"],"is_preprint":false},{"year":2015,"finding":"PKC activation reduces Kv1.5 membrane expression and current in Xenopus oocytes and MDCK cells; AMPK activation decreases Kv1.5 membrane expression in MDCK cells but not in atrial HL-1 cells, and this AMPK effect requires co-expression of Nedd4-2 in oocytes, demonstrating that both PKC and AMPK regulate Kv1.5 surface expression through distinct mechanisms.","method":"Xenopus oocyte expression, MDCK and HL-1 cell transfection, confocal microscopy, patch clamp, kinase activators and Nedd4-2 co-expression","journal":"Channels (Austin, Tex.)","confidence":"Medium","confidence_rationale":"Tier 2 — multiple cell systems and Nedd4-2 co-expression dependency test, single lab","pmids":["26043299"],"is_preprint":false},{"year":2015,"finding":"Polycomb group (PcG) proteins BMI-1 and EZH2 repress KCNA5 expression in Ewing sarcoma and neuroblastoma cells; the KCNA5 promoter bears H3K27me3 repressive marks that increase under hypoxia; genetic/pharmacological inhibition of BMI-1/EZH2 restores KCNA5 expression; ectopic Kv1.5 channel expression induces apoptotic cell death under hypoxic stress, establishing PcG-mediated epigenetic silencing of KCNA5 as a mechanism promoting cancer cell survival.","method":"Chromatin immunoprecipitation for H3K27me3, pharmacological EZH2 inhibition, genetic BMI-1 inhibition, ectopic KCNA5 overexpression, cell death assays under hypoxia","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 — ChIP plus genetic/pharmacological perturbation with defined phenotypic outcome","pmids":["25435365"],"is_preprint":false},{"year":2015,"finding":"DNA methylation of the KCNA5 CpG island promoter in Ewing sarcoma stably silences Kv1.5 channel expression; treatment with the DNA methylation inhibitor decitabine reverses KCNA5 methylation, restores Kv1.5 channel function, and inhibits Ewing sarcoma cell proliferation, demonstrating that epigenetic KCNA5 silencing contributes functionally to tumor cell proliferation.","method":"Methylation array and bisulfite sequencing, decitabine treatment, flow cytometry/electrophysiology to confirm Kv1.5 restoration, proliferation assays","journal":"Molecular cancer research","confidence":"High","confidence_rationale":"Tier 2 — pharmacological demethylation with functional rescue and proliferation phenotype","pmids":["26573141"],"is_preprint":false},{"year":2018,"finding":"miR-1 directly targets the KCNA5 3'-UTR as confirmed by luciferase reporter assay; miR-1 transfection in pulmonary artery smooth muscle cells reduces Kv1.5 current and induces membrane depolarization; miR-1 is elevated in lungs from a PAH rat model, and Kv1.5 is correspondingly decreased; antagomiR-1 prevents Kv1.5 downregulation and depolarization induced by hypoxia/Su5416.","method":"Luciferase 3'-UTR reporter assay, miR-1 transfection in PASMC, patch clamp (DPO-1-sensitive current), antagomiR-1 treatment in PAH rat model","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 2 — validated direct miRNA target with functional rescue in disease model","pmids":["29717493"],"is_preprint":false},{"year":2020,"finding":"miR-3940-5p promotes granulosa cell proliferation by directly targeting KCNA5; luciferase reporter assay validated KCNA5 as a miR-3940-5p target; functional analysis confirmed that miR-3940-5p-driven proliferation is KCNA5-dependent, identifying KCNA5 as a downstream effector of miR-3940-5p in polycystic ovary syndrome-associated granulosa cell biology.","method":"Luciferase 3'-UTR reporter assay, miR-3940-5p overexpression, KCNA5 knockdown rescue experiment, proliferation assays","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 3 — validated miRNA target with functional rescue, single lab","pmids":["32019676"],"is_preprint":false},{"year":2023,"finding":"KCNA5 variants Arg184Pro and Gly384Arg found in PAH patients produce clear loss-of-function as assessed by patch clamp in HEK293 cells; Arg184Pro also reduces Kv1.5 protein expression; transfection with either variant decreases apoptosis in human PASMC compared to wild-type, demonstrating that loss-of-function KCNA5 variants impair both channel activity and the apoptotic response in vascular smooth muscle cells.","method":"Patch-clamp electrophysiology in HEK293, flow cytometry for apoptosis in human PASMC, Western blot, confocal microscopy, molecular modeling","journal":"American journal of respiratory cell and molecular biology","confidence":"High","confidence_rationale":"Tier 2 — biophysical characterization combined with cell viability phenotype in disease-relevant cell type","pmids":["36917789"],"is_preprint":false}],"current_model":"KCNA5 encodes the voltage-gated K+ channel α-subunit Kv1.5, which forms homo- or heterotetrameric delayed-rectifier channels (IKur) in human atrial myocytes and pulmonary artery smooth muscle cells (PASMC); its surface expression and gating are regulated by post-translational modifications (SUMOylation shifting inactivation, S-acylation for quality-control trafficking, tyrosine phosphorylation by Src suppressing current), by scaffolding proteins (SAP97 retaining channels at the plasma membrane, FHL1 increasing current density and modulating gating, α-actinin-2 linking channels to the actin cytoskeleton), by dynein/Rab-GTPase-dependent endosomal recycling and proteasomal degradation, by cholesterol-rich microdomain targeting via caveolin, and by regulatory Kvβ subunits whose redox-sensitive (pyridine nucleotide-dependent) interaction with the channel C-terminus tunes inactivation; in PASMC, Kv1.5 functions as a hypoxia-sensitive O2 sensor downstream of a mitochondria–ROS–HIF-1α pathway, and its loss (through genetic mutations, epigenetic silencing by Polycomb proteins or DNA methylation, or miR-1/miR-3940-5p-mediated suppression) reduces K+ efflux, depolarizes the membrane, inhibits apoptosis, and promotes the proliferative phenotype underlying pulmonary arterial hypertension and tumor cell survival."},"narrative":{"teleology":[{"year":1991,"claim":"Molecular cloning of KCNA5 from human heart and insulinoma tissue and reconstitution in Xenopus oocytes established that the gene encodes a Shaker-family, 4-AP-sensitive delayed-rectifier K⁺ channel, answering the fundamental question of its molecular identity and basic electrophysiology.","evidence":"cDNA cloning and two-electrode voltage clamp in Xenopus oocytes, two independent groups","pmids":["2001794","1986382"],"confidence":"High","gaps":["Tetrameric stoichiometry and heteromeric partner compatibility not yet determined","Native tissue current identity not established"]},{"year":1995,"claim":"Immunolocalization of Kv1.5 to intercalated disks in human atrial and ventricular myocytes, and to vascular smooth muscle, established the channel's native tissue distribution and suggested distinct functional roles in cardiac conduction and vascular tone.","evidence":"Epitope-specific immunofluorescence with confocal colocalization in explanted human cardiac tissue","pmids":["7615797"],"confidence":"High","gaps":["Functional contribution of Kv1.5 to the native IKur current not yet proven by loss-of-function","Subcellular microdomain localization not resolved"]},{"year":1996,"claim":"Discovery that Src tyrosine kinase directly binds the Kv1.5 N-terminal proline-rich SH3-binding domain and that Kvβ2.1 co-assembles with Kv1.5 to shift gating revealed that the channel operates as a signaling complex rather than an autonomous pore, opening the question of how multiple interactors coordinately regulate IKur.","evidence":"Co-immunoprecipitation from transfected cells and native human myocardium; Kvβ2.1 cloning and co-expression electrophysiology in HEK293 cells","pmids":["8953041","8576199"],"confidence":"High","gaps":["Identity of the tyrosine phosphatase opposing Src not known","In vivo significance of Kvβ modulation untested"]},{"year":2001,"claim":"Identification of SAP97 as a PDZ-domain scaffold that clusters and immobilizes Kv1.5 at the plasma membrane, augmenting IKur, established a membrane-retention mechanism; subsequent work showed the functional effect depends on the Kv1.5 N-terminus and may be partially indirect.","evidence":"Co-immunoprecipitation, C-terminal mutagenesis, oocyte electrophysiology; later FRAP mobility measurements and N-terminal deletion analysis","pmids":["11709425","18245566","12860415"],"confidence":"High","gaps":["Whether the N-terminal dependence reflects an intermediary bridging protein is unknown","SAP97-Kv1.5 stoichiometry and structure unresolved"]},{"year":2004,"claim":"Demonstration that Kv1.5 is the predominant O₂-sensitive Kv channel in resistance PASMCs—and that K⁺ efflux through it promotes apoptotic volume decrease and caspase activation—linked the channel directly to hypoxic pulmonary vasoconstriction and to apoptosis regulation.","evidence":"Intracellular anti-Kv1.5 antibody application in native PASMCs plus KCNA5 overexpression with caspase-3 and apoptosis assays","pmids":["15217912","15140747"],"confidence":"High","gaps":["Molecular identity of the PASMC-specific hypoxia sensor upstream of Kv1.5 not defined","Contribution of Kv1.5 versus Kv2.1 to HPV quantitatively uncertain"]},{"year":2005,"claim":"Characterization of dynein-dependent retrograde trafficking and ubiquitin-proteasomal degradation of Kv1.5 revealed that channel surface density is dynamically controlled by motor-mediated internalization and protein turnover, not solely by biosynthetic delivery.","evidence":"Dominant-negative dynein/dynamin experiments, nocodazole, proteasome inhibitors (MG132/ALLN), pulse-chase with functional electrophysiology","pmids":["16051887","16185660"],"confidence":"High","gaps":["E3 ubiquitin ligase targeting Kv1.5 not identified","Signals triggering accelerated internalization in disease states unknown"]},{"year":2007,"claim":"Three post-translational regulatory axes were defined: SUMOylation selectively shifts Kv1.5 inactivation, S-acylation acts as an ER quality-control checkpoint for surface delivery, and caveolin directs Kv1.5 to cholesterol-rich microdomains that modulate gating—collectively showing that multiple lipid and protein modifications independently tune channel function.","evidence":"In vitro and in vivo SUMOylation assays with mutagenesis and electrophysiology; hydroxylamine sensitivity and acylation inhibitor studies; caveolin co-expression with sucrose fractionation and patch clamp","pmids":["17261810","17344312","18045854","17525113"],"confidence":"High","gaps":["SUMO E3 ligase and stimulus-dependent regulation of channel SUMOylation not identified","Specific palmitoyl acyltransferase for Kv1.5 unknown","Relative contribution of each modification to native IKur regulation untested"]},{"year":2008,"claim":"Mapping the post-endocytic itinerary through Rab5→Rab4 (rapid recycling) and Rab7 (degradation) compartments, and identification of FHL1 as a Kv1.5 C-terminal interactor that enhances current density and modulates gating, completed a picture of both vesicular and scaffolding control of channel availability.","evidence":"Dominant-negative Rab GTPase colocalization and electrophysiology; GST pull-down/mass spectrometry from human atrium with co-IP and patch clamp","pmids":["18755741","18281375"],"confidence":"High","gaps":["Whether FHL1 and SAP97 form a ternary complex at the channel is unknown","Recycling kinetics in native cardiomyocytes not measured"]},{"year":2012,"claim":"Discovery that Kvβ-subunit interaction with the Kv1.5 C-terminus is redox-tuned by NADPH/NADP⁺, and that both gain- and loss-of-function KCNA5 mutations associate with atrial fibrillation, connected channel redox sensing and genetic variation to cardiac arrhythmia.","evidence":"C-terminal deletion mutagenesis with intracellular nucleotide dialysis and GST pull-down; biophysical characterization of AF-associated Kv1.5 mutants","pmids":["22426702","23264583"],"confidence":"High","gaps":["Clinical penetrance and population frequency of AF-associated KCNA5 variants not established","Structural basis for pyridine nucleotide selectivity at the Kvβ–C-terminus interface unresolved"]},{"year":2015,"claim":"In vivo knockout and smooth-muscle-specific rescue showed Kv1.5 is required for redox-dependent coronary metabolic dilation; concurrently, Polycomb- and DNA-methylation-mediated epigenetic silencing of KCNA5 was shown to promote cancer cell survival by disabling apoptosis, broadening the channel's functional roles beyond excitable-cell electrophysiology.","evidence":"Kv1.5-null mice with inducible SM-specific rescue, isolated artery pharmacology; ChIP for H3K27me3, EZH2/BMI-1 inhibition, decitabine demethylation with proliferation assays","pmids":["26224794","25435365","26573141"],"confidence":"High","gaps":["Whether coronary metabolic dilation phenotype relates to PASMC O₂-sensing pathway is unclear","Whether epigenetic silencing of KCNA5 occurs in PAH patient lungs not shown"]},{"year":2018,"claim":"Validation of miR-1 as a direct KCNA5 3′-UTR targeting miRNA that is elevated in PAH lungs and suppresses Kv1.5 expression, with antagomiR rescue, established post-transcriptional repression as another layer of Kv1.5 downregulation in pulmonary vascular disease.","evidence":"Luciferase 3′-UTR reporter, miR-1 transfection in PASMC with patch clamp, antagomiR-1 in PAH rat model","pmids":["29717493"],"confidence":"High","gaps":["Relative contribution of miR-1 versus epigenetic silencing versus transcriptional repression in human PAH not quantified","Upstream signals inducing miR-1 in PAH lungs not defined"]},{"year":2023,"claim":"Functional characterization of PAH-associated KCNA5 variants (Arg184Pro, Gly384Arg) as loss-of-function mutations that impair both channel activity and PASMC apoptosis provided the strongest genetic evidence that KCNA5 deficiency directly contributes to PAH pathogenesis.","evidence":"Patch-clamp electrophysiology in HEK293, apoptosis assays in human PASMC, Western blot, molecular modeling","pmids":["36917789"],"confidence":"High","gaps":["Segregation data in PAH families not provided for these variants","Whether these variants affect heteromeric channel assembly (e.g., with Kv1.3 or Kv2.1) is untested"]},{"year":null,"claim":"Major unresolved questions include the molecular identity of the PASMC-specific O₂ sensor that inhibits Kv1.5, the E3 ubiquitin ligase responsible for proteasomal targeting, the high-resolution structure of human Kv1.5 in complex with regulatory subunits (Kvβ, SAP97, FHL1), and whether KCNA5 loss-of-function mutations are causative for heritable PAH as demonstrated by family segregation and rescue studies.","evidence":"","pmids":[],"confidence":"Low","gaps":["No PASMC-specific O₂ sensor molecularly identified","E3 ligase for Kv1.5 unknown","No cryo-EM or X-ray structure of human Kv1.5 reported in timeline"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,1,12,14]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[2,9,15,22,24,27]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[17,23,31]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[26]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[26,28]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,1,14]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[3,8,21,25,37]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,1,12,14,36]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[13,38,42]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[17,21,23]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[15,26,24]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[25,34,40,42]}],"complexes":["Kv1.5 homotetramer (IKur)","Kv1.3/Kv1.5 heterotetramer","Kv1.5–Kvβ2/Kvβ3 complex"],"partners":["SRC","SAP97","ACTN2","FHL1","KCNAB2","CAV1","UBC9","PTPRE"],"other_free_text":[]},"mechanistic_narrative":"KCNA5 encodes the Kv1.5 voltage-gated potassium channel α-subunit, which forms Shaker-family delayed-rectifier channels (IKur) that regulate membrane potential in human atrial myocytes, pulmonary artery smooth muscle cells (PASMC), macrophages, and coronary vascular smooth muscle. Surface density and gating of Kv1.5 are tuned by a network of post-translational modifications—SUMOylation selectively shifts inactivation [PMID:17261810], S-acylation serves as a quality-control checkpoint for ER-to-surface trafficking [PMID:17344312], Src-mediated tyrosine phosphorylation suppresses current [PMID:8953041], and Kvβ subunit association confers pyridine-nucleotide-dependent inactivation modulation [PMID:22426702]—while scaffolding by SAP97 immobilizes channels at plasma membrane contact sites [PMID:18245566], dynein/Rab-GTPase-dependent endosomal recycling and proteasomal degradation set the channel's half-life [PMID:16185660, PMID:18755741], and cholesterol-rich microdomain targeting via caveolin modulates gating [PMID:18045854]. In PASMC, Kv1.5 acts as the principal O₂-sensitive K⁺ channel mediating hypoxic pulmonary vasoconstriction; its loss—through loss-of-function mutations, Polycomb/DNA-methylation-mediated epigenetic silencing, or miR-1-directed repression—reduces K⁺ efflux, depolarizes the membrane, inhibits apoptosis, and drives the proliferative vascular remodeling of pulmonary arterial hypertension [PMID:15217912, PMID:18083891, PMID:36917789, PMID:25435365, PMID:29717493]. Both gain- and loss-of-function KCNA5 mutations are associated with atrial fibrillation [PMID:23264583]."},"prefetch_data":{"uniprot":{"accession":"P22460","full_name":"Potassium voltage-gated channel subfamily A member 5","aliases":["HPCN1","Voltage-gated potassium channel HK2","Voltage-gated potassium channel subunit Kv1.5"],"length_aa":613,"mass_kda":67.2,"function":"Voltage-gated potassium channel that mediates transmembrane potassium transport in excitable membranes. Forms tetrameric potassium-selective channels through which potassium ions pass in accordance with their electrochemical gradient. The channel alternates between opened and closed conformations in response to the voltage difference across the membrane. Can form functional homotetrameric channels and heterotetrameric channels that contain variable proportions of KCNA1, KCNA2, KCNA4, KCNA5, and possibly other family members as well; channel properties depend on the type of alpha subunits that are part of the channel (PubMed:12130714). Channel properties are modulated by cytoplasmic beta subunits that regulate the subcellular location of the alpha subunits and promote rapid inactivation (PubMed:12130714). Homotetrameric channels display rapid activation and slow inactivation (PubMed:12130714, PubMed:8505626). Required for normal electrical conduction including formation of the infranodal ventricular conduction system and normal action potential configuration, as a result of its interaction with XIRP2 (By similarity). May play a role in regulating the secretion of insulin in normal pancreatic islets Exhibits a faster depolarization rate, reduced voltage-dependent recovery from inactivation and an excessive cumulative inactivation","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/P22460/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KCNA5","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"IPO13","stoichiometry":0.2},{"gene":"POLR3E","stoichiometry":0.2},{"gene":"TMA16","stoichiometry":0.2},{"gene":"TOMM20A","stoichiometry":0.2},{"gene":"VDAC1","stoichiometry":0.2},{"gene":"VDAC3","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/KCNA5","total_profiled":1310},"omim":[{"mim_id":"621295","title":"CEREBRAL ARTERIOPATHY, AUTOSOMAL RECESSIVE, WITH SUBCORTICAL INFARCTS AND LEUKOENCEPHALOPATHY 1; CARASIL1","url":"https://www.omim.org/entry/621295"},{"mim_id":"612240","title":"ATRIAL FIBRILLATION, FAMILIAL, 7; ATFB7","url":"https://www.omim.org/entry/612240"},{"mim_id":"608583","title":"ATRIAL FIBRILLATION, FAMILIAL, 1; ATFB1","url":"https://www.omim.org/entry/608583"},{"mim_id":"604111","title":"POTASSIUM CHANNEL, VOLTAGE-GATED, SHAKER-RELATED SUBFAMILY, BETA MEMBER 3; KCNAB3","url":"https://www.omim.org/entry/604111"},{"mim_id":"601141","title":"POTASSIUM CHANNEL, VOLTAGE-GATED, SHAKER-RELATED SUBFAMILY, BETA MEMBER 1; KCNAB1","url":"https://www.omim.org/entry/601141"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"blood vessel","ntpm":42.2},{"tissue":"choroid plexus","ntpm":57.3},{"tissue":"heart muscle","ntpm":36.5}],"url":"https://www.proteinatlas.org/search/KCNA5"},"hgnc":{"alias_symbol":["Kv1.5","HK2","HPCN1"],"prev_symbol":[]},"alphafold":{"accession":"P22460","domains":[{"cath_id":"3.30.710.10","chopping":"117-218","consensus_level":"high","plddt":94.487,"start":117,"end":218},{"cath_id":"1.20.120.350","chopping":"227-284_320-378_396-417","consensus_level":"medium","plddt":88.3729,"start":227,"end":417},{"cath_id":"1.10.287.70","chopping":"422-529","consensus_level":"high","plddt":94.607,"start":422,"end":529}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P22460","model_url":"https://alphafold.ebi.ac.uk/files/AF-P22460-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P22460-F1-predicted_aligned_error_v6.png","plddt_mean":71.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KCNA5","jax_strain_url":"https://www.jax.org/strain/search?query=KCNA5"},"sequence":{"accession":"P22460","fasta_url":"https://rest.uniprot.org/uniprotkb/P22460.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P22460/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P22460"}},"corpus_meta":[{"pmid":"9759557","id":"PMC_9759557","title":"Human 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orthogonal antibody epitopes, functional context established\",\n      \"pmids\": [\"7615797\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Kv1.5 (KCNA5) channels are blocked by ketoconazole in a mechanism distinct from HERG block; ketoconazole blocks Kv1.5 with an IC50 of ~107 µM when expressed in Xenopus oocytes, and cumulative application with terfenadine produces additive rather than competitive block.\",\n      \"method\": \"Two-microelectrode voltage clamp in Xenopus oocytes heterologously expressing Kv1.5\",\n      \"journal\": \"The Journal of pharmacology and experimental therapeutics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro electrophysiological reconstitution with pharmacological characterization\",\n      \"pmids\": [\"9694927\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Kv1.5 (KCNA5) is expressed in activated microglia in vivo following LPS injection into rat brain cortex; Kv1.5 expression precedes inducible nitric oxide synthase expression and correlates temporally with OX-42 (microglial activation marker).\",\n      \"method\": \"Immunohistochemistry with anti-Kv1.5 and anti-Kv1.3 antibodies, immunoblot analysis of LPS-injected rat brains\",\n      \"journal\": \"Glia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization in vivo with temporal correlation to activation markers, single lab\",\n      \"pmids\": [\"9814821\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Cell-specific expression of the Kv1.5 promoter is regulated by a silencer element (KRE) containing a dinucleotide-repetitive sequence; a 27-kDa KRE binding factor (KBF) was purified from GH3 and cardiac nuclear extracts and specifically binds KRE, suggesting a role in cardiac/GH3-specific repression of Kv1.5.\",\n      \"method\": \"Electromobility gel shift assay (EMSA), magnetic DNA affinity purification, UV cross-linking, reporter silencer assays\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — biochemical purification of binding factor with functional silencer validation, single lab\",\n      \"pmids\": [\"10222341\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"SAP97 physically interacts with Kv1.5 via the C-terminal PDZ-binding motif (T-D-L) of Kv1.5; mutation of these three residues abolishes coimmunoprecipitation. SAP97 coexpression in Xenopus oocytes augments Kv1.5-encoded outward potassium currents. Both proteins colocalize at intercalated disks and lateral membranes of cardiac myocytes.\",\n      \"method\": \"Coimmunoprecipitation in COS-7 cells, immunocytochemistry in cardiac myocytes, Xenopus oocyte electrophysiology, site-directed mutagenesis of C-terminal PDZ motif\",\n      \"journal\": \"American journal of physiology. Heart and circulatory physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — co-IP with mutagenesis validation, functional electrophysiological readout, localization in native cardiac cells\",\n      \"pmids\": [\"11709425\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"SAP97 increases Kv1.5 current through an indirect mechanism dependent on the Kv1.5 N-terminus rather than the C-terminal PDZ-binding motif; deletion of the N-terminus eliminated SAP97-mediated current increase whereas deletion of the C-terminal PDZ motif had no effect. No physical interaction between SAP97 and Kv1.5 could be detected by co-IP or yeast two-hybrid.\",\n      \"method\": \"Xenopus oocyte electrophysiology, N- and C-terminal deletion constructs, co-IP in HEK cells, yeast two-hybrid, immunocytochemistry\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods defining domain requirements, functional electrophysiological readout\",\n      \"pmids\": [\"12860415\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Overexpression of human KCNA5 in COS-7 cells and rat pulmonary artery smooth muscle cells (PASMC) increases Kv channel current 24–34-fold, accelerates apoptotic volume decrease, increases caspase-3 activity, and induces apoptosis; blockade of KCNA5 with 4-aminopyridine inhibits these effects, establishing K+ efflux through KCNA5 as a driver of apoptosis.\",\n      \"method\": \"Transient transfection, whole-cell patch-clamp, caspase-3 activity assay, flow cytometry for apoptosis, pharmacological blockade with 4-AP\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (electrophysiology, biochemical, pharmacological) in two cell types\",\n      \"pmids\": [\"15140747\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Acute hypoxia selectively inhibits Kv1.5 channel activity in pulmonary artery smooth muscle cells (PASMC) but not in mesenteric artery smooth muscle cells, HEK-293, or COS-7 cells; overexpression of human KCNA5 in rat MASMC conferred sensitivity to hypoxia only in PASMC, indicating a PASMC-specific hypoxia-sensing mechanism targets Kv1.5.\",\n      \"method\": \"Overexpression of human KCNA5 in multiple cell types, whole-cell patch-clamp, hypoxia chambers (PO2 reduction from 145 to 35 mmHg)\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific functional comparison with overexpression controls in multiple cell lines\",\n      \"pmids\": [\"16236819\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Kv1.5 undergoes proteasomal degradation with a half-life of ~6.7 h; proteasome inhibitors (MG132, ALLN, lactacystin) prolonged half-life, increased ubiquitinated Kv1.5, and elevated IKur currents by stabilizing channel protein in ER/Golgi; lysosomal inhibitor had no effect.\",\n      \"method\": \"Pulse-chase analysis, proteasome and lysosome inhibitors, ubiquitination assay, immunofluorescence, patch-clamp in COS cells and rat atrial cells\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (pulse-chase, ubiquitination, pharmacology, electrophysiology) in heterologous and native cells\",\n      \"pmids\": [\"16185660\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Retrograde trafficking by the dynein motor complex regulates Kv1.5 surface expression; disruption of dynein-dynactin (p50/dynamitin overexpression), dynamin inhibition, or microtubule depolymerization (nocodazole) doubled Kv1.5 currents by redistributing channels to the plasma membrane. Kv1.5 co-immunoprecipitated with the dynein motor complex in HEK cells and rat cardiac myocytes, requiring an intact SH3-binding domain in the Kv1.5 N-terminus.\",\n      \"method\": \"Coimmunoprecipitation, confocal imaging, Proteinase K surface accessibility assay, patch-clamp, dominant-negative p50/dynamitin overexpression, pharmacological dynamin inhibition, nocodazole treatment\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods, co-IP in heterologous and native cells, functional electrophysiological validation\",\n      \"pmids\": [\"16051887\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Two KCNA5 coding region polymorphisms (P532L and R578K) in the C-terminus display near-normal gating but striking resistance to quinidine block (IC50 increased from 8.4 µM to 133 µM and 54 µM respectively), identifying the C-terminus as a determinant of drug sensitivity.\",\n      \"method\": \"Patch-clamp in transfected CHO cells, pharmacological block with quinidine\",\n      \"journal\": \"Clinical pharmacology and therapeutics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro electrophysiology with mutagenesis/natural variant functional characterization\",\n      \"pmids\": [\"15735608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Kv1.3 and Kv1.5 form heteromeric channels in macrophages; different Kv1.3/Kv1.5 stoichiometries create biophysically and pharmacologically distinct channels, and the presence of Kv1.5 renders the channels resistant to Kv1.3-selective drugs, impairing proposed Kv1.3-targeted therapies.\",\n      \"method\": \"Patch-clamp electrophysiology, pharmacological profiling in mononuclear phagocytes expressing different Kv1.3/Kv1.5 ratios\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — electrophysiological characterization of heteromeric channels in native cells, single lab\",\n      \"pmids\": [\"17157812\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Kv1.5 does not associate with caveolin-3 or localize to caveolae in rat and canine cardiac myocytes; co-IP showed no Kv1.5–caveolin-3 interaction, and immunoelectron microscopy confirmed minimal overlap, while Kv1.5 fractionates with non-raft membranes in HEK293 cells.\",\n      \"method\": \"Coimmunoprecipitation, wide-field microscopy with deconvolution, immunoelectron microscopy, sucrose gradient fractionation\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal localization methods in native cardiac tissue and heterologous cells\",\n      \"pmids\": [\"17054951\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Membrane cholesterol depletion by methyl-beta-cyclodextrin (MCD) increases Kv1.5-based IKur current and redistributes Kv1.5 subunits from concentrated clusters into larger clusters throughout the plasma membrane in rat atrial myocytes and neonatal cardiomyocytes transfected with GFP-Kv1.5; Kv1.5 is concentrated in cholesterol-enriched microdomains distinct from caveolae.\",\n      \"method\": \"Patch-clamp in isolated rat atrial myocytes, confocal live imaging of GFP-Kv1.5 in transfected neonatal cardiomyocytes, sucrose gradient fractionation, cholesterol depletion/repletion\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — electrophysiology correlated with live-cell imaging and biochemical fractionation, multiple orthogonal methods\",\n      \"pmids\": [\"17525113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"S-acylation (palmitoylation) of Kv1.5 on both NH2 and COOH termini via hydroxylamine-sensitive thioester bonds regulates channel surface expression; pharmacological inhibition of S-acylation decreased surface Kv1.5 and targeted it for proteasomal degradation; COOH-terminal cysteines govern this process, and their mutation paradoxically increases surface expression.\",\n      \"method\": \"Biochemical S-acylation assay (hydroxylamine sensitivity), pharmacological inhibitors of palmitoylation, proteasome inhibitors, immunofluorescence, time-course experiments with nascent vs. surface channel\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — biochemical identification of PTM site, functional surface expression readout, mutagenesis of COOH cysteines\",\n      \"pmids\": [\"17344312\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Caveolin is required for trafficking of Kv1.5 to lipid raft/low-density membrane microdomains; in cells lacking caveolin-1 or -3, Kv1.5 raft association requires caveolin coexpression forming channel-caveolin complexes. Caveolin trafficking mutants sequester Kv1.5 in intracellular compartments, reducing surface channel. Wild-type caveolin coexpression induces depolarizing shifts in Kv1.5 activation and inactivation analogous to cholesterol elevation.\",\n      \"method\": \"Sucrose gradient fractionation, coimmunoprecipitation, electrophysiology, caveolin trafficking mutants, cells with/without endogenous caveolin\",\n      \"journal\": \"Molecular pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods linking caveolin to Kv1.5 trafficking and function\",\n      \"pmids\": [\"18045854\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"After internalization, Kv1.5 traffics via Rab5-dependent early endosomes and is rapidly targeted for recycling via Rab4-positive endosomes; a fraction is directed for degradation via Rab7. Dominant-negative Rab5, Rab4, and Rab7 constructs significantly increased Kv1.5 functional expression, while Rab7 overexpression decreased it.\",\n      \"method\": \"Colocalization with Rab-GFP constructs, dominant-negative Rab expression, patch-clamp in H9c2 myoblasts and HEK293 cells, surface labeling and time-course trafficking assays\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple Rab GTPase dominant-negative constructs with functional electrophysiological readout in two cell lines\",\n      \"pmids\": [\"18755741\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Four and a half LIM protein 1 (FHL1) is a binding partner of KCNA5 in human atrium; identified by GST-KCNA5 C-terminal pulldown and mass spectrometry, confirmed by co-IP in human atrial tissue and transfected CHO cells. FHL1 coexpression markedly increased Kv1.5 current density, shifted voltage dependence of activation to more positive potentials, and increased slow inactivation.\",\n      \"method\": \"GST pulldown with mass spectrometry, co-IP in human atrium and CHO cells, confocal colocalization, whole-cell patch-clamp in CHO cells\",\n      \"journal\": \"Cardiovascular research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — unbiased proteomics identification confirmed by reciprocal co-IP in native tissue, with functional electrophysiological characterization\",\n      \"pmids\": [\"18281375\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Kv1.5 targeting to lipid raft microdomains is context-dependent and regulated by partner proteins: in transfected HEK-293 cells homo- and heterotetrameric Kv1.5 channels target to rafts, but in macrophages Kv1.5 localizes to non-raft domains. LPS activation redirects Kv1.5 to rafts by increasing Kv1.3/Kv1.5 ratio and caveolin. Kv1.3/Kv1.5 hybrid channels are mostly in non-raft domains. Kvβ2.1 coexpression impairs Kv1.5 targeting to rafts.\",\n      \"method\": \"Sucrose density gradient fractionation, coexpression of dominant-negative caveolin mutants and Kvβ2.1, macrophage LPS activation, multiple cell types\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — biochemical fractionation in multiple cell contexts with partner protein manipulation, single lab\",\n      \"pmids\": [\"18668522\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"A homology model of Kv1.5 based on the Kv1.2 crystal structure was used with molecular docking to identify key residues in the channel's active site that determine blocker binding; pharmacophore analysis identified structural features required for channel blockade.\",\n      \"method\": \"Homology modeling (MODELLER 9v2 on Kv1.2 PDB:2A79), molecular docking, pharmacophore modeling (HipHop), cross-validated with published mutagenesis data\",\n      \"journal\": \"Journal of molecular graphics & modelling\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 — computational modeling only, validated against existing mutagenesis but no new experimental data\",\n      \"pmids\": [\"18485768\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Hypoxia suppresses Kv1.5 (KCNA5) channel expression in pulmonary artery smooth muscle cells via the 15-lipoxygenase/15-HETE pathway; blocking 15-LOX prevented hypoxia-induced Kv1.5 mRNA/protein downregulation and partly rescued IKV currents, while exogenous 15-HETE mimicked hypoxia-induced Kv1.5 downregulation.\",\n      \"method\": \"15-LOX pharmacological inhibitors, 15-HETE exogenous application, RT-PCR, western blot, patch-clamp in PASMC and pulmonary artery rings\",\n      \"journal\": \"Prostaglandins & other lipid mediators\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological pathway dissection with multiple readouts in native cells, single lab\",\n      \"pmids\": [\"18984061\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"SAP97 retains Kv1.5 subunits in the plasma membrane of cardiac myocytes; adenovirus-mediated SAP97 overexpression in neonatal rat cardiomyocytes increased IKur, clustered endogenous Kv1.5 at cell-cell contacts, and reduced GFP-Kv1.5 lateral mobility as measured by FRAP.\",\n      \"method\": \"Adenoviral overexpression, immunocytochemistry, FRAP, patch-clamp in neonatal rat cardiomyocytes and CHO cells\",\n      \"journal\": \"American journal of physiology. Heart and circulatory physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (FRAP, electrophysiology, immunocytochemistry) in native cardiomyocytes\",\n      \"pmids\": [\"18245566\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"T1 domain mutations (G182R and E211D) in KCNA5 found in idiopathic PAH patients cause accelerated inactivation at more hyperpolarized potentials, reduced channel protein expression (immature glycosylated form predominates), and intracellular retention of channel protein rather than plasma membrane localization.\",\n      \"method\": \"Transient transfection of HEK-293 and COS-1 cells, whole-cell patch-clamp, western blot (glycosylation forms), immunostaining for subcellular distribution\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — electrophysiology plus protein biochemistry plus localization in parallel, disease-relevant mutations\",\n      \"pmids\": [\"20018952\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"A novel KCNA5 N-terminal deletion (11 amino acids including a proline-rich SH3-binding site) causes ~60% reduction in IKur and dominant-negative suppression of wild-type current; Src inhibitor PP2 prevented v-Src tyrosine kinase from suppressing wild-type Kv1.5 by ~90%, but the mutant channel lacking the SH3 motif showed no response to v-Src, implicating tyrosine kinase signaling via the N-terminal SH3-binding domain in KCNA5 regulation.\",\n      \"method\": \"Site-directed mutagenesis, whole-cell patch-clamp in transfected cells, pharmacological Src inhibition with PP2, v-Src coexpression\",\n      \"journal\": \"Heart rhythm\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — mutagenesis of defined domain combined with pharmacological and molecular kinase manipulation, functional electrophysiological readout\",\n      \"pmids\": [\"20638934\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The C-terminal domain of Kv1.5 interacts with Kvβ subunits in a pyridine nucleotide-dependent manner; a specific region (Arg543-Val583) in the C-terminus binds Kvβ2:NADPH with higher affinity than Kvβ2:NADP+. Deletion of the C-terminus abolished pyridine nucleotide-dependent modulation of Kv1.5-Kvβ3 and Kv1.5-Kvβ2 currents. GST-C-terminal fusion protein precipitated Kvβ from mouse brain lysates.\",\n      \"method\": \"C-terminal deletion constructs, whole-cell patch-clamp with intracellular NADPH/NADP+ in pipette, GST pulldown from brain lysates, structural analysis\",\n      \"journal\": \"Pflugers Archiv : European journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — biochemical pulldown, domain deletion mutagenesis, and electrophysiology with defined nucleotide conditions\",\n      \"pmids\": [\"22426702\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"KCNA5 loss-of-function mutations (Y155C, D469E, P488S) decrease Kv1.5 surface expression and reduce IKur, while gain-of-function mutations (E48G, A305T, D322H) preserve surface expression and increase current; both types are found in patients with early-onset lone atrial fibrillation, showing that both increased and decreased KCNA5 current can promote AF.\",\n      \"method\": \"Direct sequencing of KCNA5 in patients and controls, confocal microscopy for surface expression, whole-cell patch-clamp in transfected cells\",\n      \"journal\": \"European heart journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — electrophysiology and localization experiments for multiple defined mutations in a large clinical cohort\",\n      \"pmids\": [\"23264583\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Kv1.5 channels in vascular smooth muscle are required for coronary metabolic dilation; Kv1.5 null mice show impaired myocardial blood flow response to increased cardiac work, reduced H2O2-mediated vascular relaxation, and cardiac dysfunction/tissue hypoxia under stress. Smooth muscle-specific re-expression of Kv1.5 in null mice rescues the phenotype.\",\n      \"method\": \"Kv1.5 knockout mice, inducible smooth muscle-specific Kv1.5 transgenic rescue, myocardial blood flow measurement, tissue oxygen tension, isolated vessel pharmacology (H2O2, adenosine, acetylcholine)\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — knockout plus cell-type-specific rescue establishes pathway role; multiple physiological readouts\",\n      \"pmids\": [\"26224794\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PKC activation reduces Kv1.5 surface expression and current in Xenopus oocytes, MDCK cells, and HL-1 atrial cells. AMPK activation decreases Kv1.5 membrane expression in MDCK cells (but not HL-1 cells) in a Nedd4-2-dependent manner in oocytes, indicating that two kinases regulate Kv1.5 surface expression through distinct mechanisms.\",\n      \"method\": \"Confocal microscopy, whole-cell electrophysiology, PKC and AMPK activators, Nedd4-2 coexpression in Xenopus oocytes, MDCK cells, HL-1 atrial cells\",\n      \"journal\": \"Channels (Austin, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — electrophysiology correlated with imaging across multiple cell systems, single lab\",\n      \"pmids\": [\"26043299\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Polycomb group proteins BMI-1 and EZH2 repress KCNA5 promoter via H3K27me3 chromatin modifications in Ewing sarcoma; repression increases under hypoxia. Genetic/pharmacological inhibition of BMI-1/EZH2 restores KCNA5 expression and sensitizes cells to stress-induced death. Ectopic Kv1.5 expression induces apoptosis under hypoxia.\",\n      \"method\": \"Promoter methylation analysis, ChIP for H3K27me3, decitabine treatment, BMI-1/EZH2 inhibitors, ectopic KCNA5 expression, cell viability assays under hypoxia\",\n      \"journal\": \"Molecular cancer research : MCR\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — chromatin analysis plus gain-of-function plus pharmacological reversal, multiple orthogonal approaches\",\n      \"pmids\": [\"26573141\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"DNA methylation of the KCNA5 promoter CpG island contributes to stable epigenetic silencing of Kv1.5 in Ewing sarcoma; promoter methylation is reversed by decitabine, which inhibits Ewing sarcoma cell proliferation through mechanisms including restoration of Kv1.5 channel function.\",\n      \"method\": \"Genome-wide methylation arrays, bisulfite sequencing, decitabine treatment with proliferation assays and channel function readout\",\n      \"journal\": \"Molecular cancer research : MCR\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — epigenetic mechanism linked to functional channel restoration and cell proliferation phenotype\",\n      \"pmids\": [\"26573141\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Sertraline blocks Kv1.5 channels as an open-channel blocker; it reduces whole-cell Kv1.5 currents (IC50 0.71 µM), accelerates inactivation decay, shows use-dependence, slows deactivation causing tail current crossover, and displays weak voltage dependence (electrical distance δ=0.16) consistent with an open-channel blocking mechanism.\",\n      \"method\": \"Whole-cell patch-clamp of cloned rat Kv1.5 stably expressed in CHO cells, concentration-response, voltage-dependence, use-dependence, deactivation kinetics\",\n      \"journal\": \"The Korean journal of physiology & pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — detailed in vitro electrophysiological characterization of blocking mechanism with multiple pharmacological parameters\",\n      \"pmids\": [\"26937216\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"miR-1 directly targets KCNA5 (confirmed by luciferase reporter assay), reduces Kv1.5 currents, and induces membrane depolarization in isolated pulmonary artery smooth muscle cells; miR-1 is upregulated in a rat PAH model and its inhibition by antagomiR-1 prevents Kv1.5 channel downregulation and depolarization.\",\n      \"method\": \"Luciferase 3'-UTR reporter assay, patch-clamp (whole-cell), antagomiR transfection, qPCR and protein quantification in rat PAH model\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct target validation by reporter assay combined with functional electrophysiology and in vivo disease model\",\n      \"pmids\": [\"29717493\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"miR-3940-5p promotes granulosa cell proliferation by targeting KCNA5; the targeting was validated by luciferase reporter assay and functional studies showed miR-3940-5p overexpression promotes proliferation in a KCNA5-dependent manner.\",\n      \"method\": \"Luciferase reporter assay, miR-3940-5p overexpression, KCNA5 knockdown, cell proliferation assays\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct 3'-UTR validation plus epistasis (KCNA5-dependent proliferation effect), single lab\",\n      \"pmids\": [\"32019676\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Two KCNA5 variants (Arg184Pro, Gly384Arg) found in PAH patients result in loss of potassium channel function by electrophysiology and molecular modeling; Arg184Pro additionally reduces Kv1.5 protein expression. Both variants decrease apoptosis in human pulmonary artery smooth muscle cells compared to wild-type, demonstrating that loss of KCNA5 function impairs apoptosis relevant to PAH pathology.\",\n      \"method\": \"Patch-clamp in HEK293 cells transfected with wild-type or mutant Kv1.5, flow cytometry for apoptosis, western blot for expression, confocal microscopy, molecular modeling\",\n      \"journal\": \"American journal of respiratory cell and molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — electrophysiology plus molecular modeling plus cell biology in disease-relevant cells, multiple orthogonal methods\",\n      \"pmids\": [\"36917789\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Kv1.5 mediates K+ efflux that promotes endothelial apoptosis in response to palmitate; silencing Kv1.5 with siRNA reduced palmitate-induced apoptosis, mitochondrial and intracellular ROS, loss of mitochondrial membrane potential, and caspase-3 cleavage while increasing Bcl-2/Bax ratio in HUVECs. Kv1.5 protein expression is also elevated in endothelial cells of thoracic aorta in type 2 diabetic mice.\",\n      \"method\": \"siRNA knockdown, flow cytometry for apoptosis, fluorescent probes for ROS and mitochondrial membrane potential, western blot, vessel ring functional assays in diabetic mice\",\n      \"journal\": \"Life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — siRNA knockdown with multiple mechanistic readouts in HUVECs and in vivo disease model, single lab\",\n      \"pmids\": [\"26764232\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KCNA5 encodes Kv1.5, a voltage-gated potassium channel alpha-subunit forming the ultrarapid delayed rectifier current (IKur) in human atrial myocytes; the channel is regulated at the plasma membrane by SAP97/FHL1 scaffolding interactions, dynein/dynactin-mediated retrograde trafficking via Rab5/Rab4/Rab7 endosomal pathways, proteasomal degradation, S-acylation at C-terminal cysteines, and cholesterol/caveolin-dependent targeting to membrane microdomains; its gating and pharmacological sensitivity are modulated by Kvβ subunits through a C-terminal domain (Arg543-Val583) in a pyridine nucleotide-redox-dependent manner, while its activity is regulated by Src-family tyrosine kinases via an N-terminal SH3-binding domain, by PKC and AMPK reducing surface expression, and by miR-1 targeting the 3'-UTR; in pulmonary artery smooth muscle cells Kv1.5 is selectively inhibited by acute hypoxia through a PASMC-specific mechanism involving the 15-LOX/15-HETE pathway, and loss-of-function reduces apoptosis promoting vascular remodeling, while in coronary smooth muscle Kv1.5 is required to couple myocardial blood flow to metabolic demand; epigenetic silencing of KCNA5 by polycomb-mediated H3K27me3 and promoter CpG methylation suppresses apoptosis and promotes cancer cell survival under stress.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1991,\n      \"finding\": \"KCNA5 (HK2/hPCN1) was molecularly cloned from human ventricle and insulinoma/islet tissue, and functional expression in Xenopus oocytes demonstrated a voltage-dependent, slowly inactivating outward K+ current sensitive to low concentrations of 4-aminopyridine, establishing it as a Shaker-family delayed rectifier potassium channel.\",\n      \"method\": \"cDNA cloning, Northern blot, functional expression in Xenopus oocytes with two-electrode voltage clamp\",\n      \"journal\": \"FASEB journal / Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — original molecular cloning with functional reconstitution in two independent studies\",\n      \"pmids\": [\"2001794\", \"1986382\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Stable mammalian cell expression of Kv1.5 (HK2) revealed a rapidly activating, slowly inactivating delayed rectifier current with well-defined gating kinetics (activation midpoint ~−14 mV, slow biexponential inactivation with voltage-independent time constants ~240 ms and ~2,700 ms), K+ selectivity, and 4-AP sensitivity, establishing the channel's intrinsic biophysical properties.\",\n      \"method\": \"Stable transfection in mouse L-cells, whole-cell patch-clamp electrophysiology\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — rigorous in vitro reconstitution with comprehensive biophysical characterization\",\n      \"pmids\": [\"8505626\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Kv1.5 protein is highly localized at intercalated disk regions in human atrial and ventricular myocytes, as determined by colocalization with connexin and N-cadherin; NH2-terminal antibodies additionally stained vascular smooth muscle, suggesting epitope accessibility and possibly different channel structure in cardiac versus vascular myocytes.\",\n      \"method\": \"Immunofluorescence with epitope-specific antibodies in explanted human cardiac tissue, confocal colocalization\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct localization experiment in native tissue with two distinct antibodies and colocalization controls\",\n      \"pmids\": [\"7615797\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Kv1.5 (hKv1.5) directly associates with Src tyrosine kinase via the channel's proline-rich N-terminal sequences and the SH3 domain of Src; this interaction results in tyrosine phosphorylation of hKv1.5 and suppression of channel current in cells co-expressing v-Src, establishing a signaling complex between a potassium channel and a protein tyrosine kinase.\",\n      \"method\": \"Co-immunoprecipitation from transfected cells and human myocardium, SH3 domain pull-down, whole-cell patch clamp in v-Src co-expressing cells\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — reciprocal co-IP in native tissue plus functional electrophysiology, replicated in heterologous system\",\n      \"pmids\": [\"8953041\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Endogenous Kvβ2.1 co-assembles with transfected hKv1.5 α-subunit and shifts the midpoints of activation and inactivation by ~14 mV and ~12 mV toward hyperpolarized potentials, respectively, and increases the extent of slow inactivation, explaining cell-line-dependent differences in Kv1.5 current kinetics.\",\n      \"method\": \"Molecular cloning, immunopurification, Western blot detection of endogenous Kvβ2.1; functional co-expression in HEK293 cells with patch clamp\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — biochemical identification of endogenous subunit assembly combined with functional rescue reconstitution\",\n      \"pmids\": [\"8576199\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Ketoconazole directly blocks both HERG and Kv1.5 channels heterologously expressed in Xenopus oocytes, with IC50 values of ~49 µM and ~107 µM, respectively; the mechanism of block differs between the two channels, and combined application with terfenadine at IC50 concentrations produces additive rather than competitive block.\",\n      \"method\": \"Heterologous expression in Xenopus oocytes, two-microelectrode voltage-clamp pharmacology\",\n      \"journal\": \"The Journal of pharmacology and experimental therapeutics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct pharmacological characterization in reconstituted system with mechanistic analysis\",\n      \"pmids\": [\"9694927\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"A 27-kDa Kv1.5 repressor element binding factor (KBF) was identified in GH3 and cardiac nuclear extracts that specifically binds a 52-bp dinucleotide-repetitive silencer element (KRE) in the Kv1.5 promoter; this KBF–KRE interaction may regulate the cardiac- and GH3-specific expression of the Kv1.5 gene.\",\n      \"method\": \"Electromobility gel shift assay (EMSA), magnetic DNA affinity purification, UV cross-linking\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct biochemical identification of DNA-binding protein, single lab\",\n      \"pmids\": [\"10222341\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"α-actinin-2 physically interacts with Kv1.5 via the channel's N-terminus/core region, as shown by in vitro co-immunoprecipitation and co-expression in HEK cells; co-localization at the membrane was observed, and disruption of the actin cytoskeleton or antisense knockdown of α-actinin-2 modulated Kv1.5 ion and gating current density.\",\n      \"method\": \"In vitro translation co-immunoprecipitation, co-expression in HEK cells, confocal colocalization, actin cytoskeleton disruption, antisense knockdown with patch clamp\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (biochemical interaction + functional consequence)\",\n      \"pmids\": [\"10812072\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Protein tyrosine phosphatase epsilon (PTP epsilon) dephosphorylates Kv1.5 in sciatic nerve tissue and Schwann cells; loss of PTP epsilon leads to hyperphosphorylation of Kv1.5 (and Kv2.1) and increased delayed-rectifier K+ channel activity, accompanied by hypomyelination, establishing PTP epsilon as a negative regulator of Kv1.5 channel activity in vivo.\",\n      \"method\": \"PTP epsilon knockout mice, Western blot for tyrosine phosphorylation, Xenopus oocyte co-expression electrophysiology, substrate-trapping co-IP with Kv2.1\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — genetic knockout with biochemical and functional validation in native tissue\",\n      \"pmids\": [\"10921884\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"SAP97 co-immunoprecipitates with Kv1.5 in COS-7 cells and co-localizes with Kv1.5 at intercalated disks and lateral membranes in cardiac myocytes; SAP97–Kv1.5 interaction requires the three C-terminal residues (TDL) of Kv1.5; co-expression with SAP97 augments Kv1.5-encoded outward K+ currents in Xenopus oocytes.\",\n      \"method\": \"Co-immunoprecipitation from transfected COS-7 cells, immunocytochemistry in cardiac myocytes, C-terminal mutagenesis, Xenopus oocyte functional expression\",\n      \"journal\": \"American journal of physiology. Heart and circulatory physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal biochemical interaction with mutagenesis confirmation and functional readout\",\n      \"pmids\": [\"11709425\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Mutagenesis of residues Thr-479, Thr-480, Val-505, Ile-508, and Val-512 in the pore helix and S6 segment of Kv1.5 drastically reduced affinity for the channel blocker S0100176 (e.g., T480A increased IC50 362-fold), identifying these inner-cavity residues as the drug-binding site and providing a molecular basis for open-channel block of Kv1.5.\",\n      \"method\": \"Ala-scanning mutagenesis, heterologous expression in Xenopus oocytes, voltage-clamp pharmacology, homology modeling based on KcsA crystal structure\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic mutagenesis with structural modeling, multiple mutants tested\",\n      \"pmids\": [\"14578345\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"SAP97 increases hKv1.5 currents through an indirect mechanism dependent on the Kv1.5 N-terminus; deletion of the N-terminus abolished SAP97-mediated current increase, whereas deletion of the C-terminal PDZ-binding motif had no effect; no direct physical interaction between SAP97 and Kv1.5 was detected in cardiac myocytes or transfected HEK cells.\",\n      \"method\": \"N- and C-terminal deletion mutants, transfection in HEK cells, co-immunoprecipitation, yeast two-hybrid, confocal microscopy, patch clamp\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple methods but indirect mechanism without identified intermediary\",\n      \"pmids\": [\"12860415\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Overexpressed human Kv1.5 in pulmonary artery smooth muscle cells (PASMC) generates a 15-pS single-channel current and large whole-cell K+ current; ET-1, nicotine, bepridil, and correolide each significantly and reversibly reduced Kv1.5 currents, and nicotine/bepridil accelerated inactivation kinetics, identifying specific modulators of the channel.\",\n      \"method\": \"Heterologous overexpression (KCNA5) in PASMC and cell lines, single-channel and whole-cell patch clamp, pharmacology\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — single-channel and whole-cell recordings with pharmacological characterization\",\n      \"pmids\": [\"17267549\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Overexpression of KCNA5 in COS-7 cells and rat PASMC significantly increases Kv current (IKV) and enhances staurosporine-induced caspase-3 activation and apoptosis; apoptotic volume decrease (AVD) is accelerated, and 4-AP blockade of KCNA5 channels inhibits staurosporine-induced apoptosis, demonstrating that K+ efflux through Kv1.5 channels promotes apoptotic cell shrinkage and apoptosis.\",\n      \"method\": \"Transient transfection of KCNA5, whole-cell patch clamp, caspase-3 activity assay, flow cytometry for apoptosis, pharmacological blockade with 4-AP\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple cell types, pharmacological rescue, defined cellular phenotype\",\n      \"pmids\": [\"15140747\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Kv1.5 (along with Kv2.1) accounts for virtually all O2-sensitive current in resistance pulmonary artery smooth muscle cells; intracellular anti-Kv1.5 antibodies inhibit correolide-sensitive IK, and anti-Kv1.5 plus anti-Kv2.1 additively depolarize resistance PASMCs and inhibit hypoxic depolarization, establishing Kv1.5 as the predominant O2-sensitive Kv channel mediating hypoxic pulmonary vasoconstriction.\",\n      \"method\": \"Intracellular antibody application, patch clamp in isolated resistance PASMCs, selective pharmacology (correolide), immunohistochemistry\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — intracellular antibody experiments plus pharmacological dissection in native cells\",\n      \"pmids\": [\"15217912\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Kv1.5 surface expression is regulated by retrograde trafficking via the dynein motor complex: disruption of dynein-dynactin (p50/dynamitin overexpression), inhibition of endocytosis (dynamin inhibitory peptide), or microtubule depolymerization (nocodazole) all increase Kv1.5 current density and plasma membrane localization; co-immunoprecipitation demonstrated direct Kv1.5–dynein interaction requiring an intact SH3-binding domain in the Kv1.5 N-terminus.\",\n      \"method\": \"Dominant-negative dynein overexpression, dynamin inhibitory peptide, nocodazole treatment, co-immunoprecipitation, Proteinase K surface accessibility assay, confocal imaging, patch clamp\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods, direct biochemical interaction, functional consequence\",\n      \"pmids\": [\"16051887\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Acute hypoxia selectively inhibits Kv1.5 (KCNA5) channel activity in PASMC but not in mesenteric artery smooth muscle cells (MASMC), HEK-293, or COS-7 cells; overexpression of KCNA5 in rat MASMC did not confer hypoxia sensitivity, whereas overexpression in PASMC did, demonstrating that a PASMC-specific hypoxia-sensitive mechanism is required for Kv1.5 inhibition.\",\n      \"method\": \"Heterologous KCNA5 overexpression in multiple cell types, whole-cell patch clamp under varying PO2\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific transfer-of-function experiment with multiple controls\",\n      \"pmids\": [\"16236819\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Kv1.5 protein is degraded by the ubiquitin-proteasome pathway with a half-life of ~6.7 h; proteasome inhibitors (MG132, ALLN) prolong the half-life, increase Kv1.5 protein levels and ubiquitinated forms, accumulate channel in the ER/Golgi, and increase IKur currents; lysosomal inhibitors have no effect, and this proteasomal degradation pathway was confirmed in rat atrial cells for endogenous Kv1.5.\",\n      \"method\": \"Pulse-chase analysis, immunofluorescence, proteasome/lysosomal inhibitor pharmacology, patch clamp, Western blot for ubiquitinated forms\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple inhibitors and pulse-chase kinetics, confirmed in native cells\",\n      \"pmids\": [\"16185660\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"C-terminal polymorphisms P532L and R578K in KCNA5 produce near-normal channel gating but confer striking resistance to quinidine block (IC50 increased from 8.4 µM to 133 µM and 54 µM, respectively), identifying the C-terminus as a region modulating drug sensitivity.\",\n      \"method\": \"SSCP/direct sequencing for variant identification, patch-clamp pharmacology in transfected CHO cells\",\n      \"journal\": \"Clinical pharmacology and therapeutics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — functional mutagenesis with quantitative IC50 determination\",\n      \"pmids\": [\"15735608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Kv1.5 does not co-localize with caveolin-3 in rat and canine atrial or ventricular myocytes (co-localization <12%) and does not associate with low-density raft fractions in HEK293 cells, while co-immunoprecipitation shows Kv1.5 associates with α-actinin but not caveolin-3, demonstrating that Kv1.5 resides outside caveolae in cardiac myocytes.\",\n      \"method\": \"Co-immunoprecipitation, sucrose-gradient fractionation, wide-field deconvolution microscopy, immunoelectron microscopy\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal localization methods in native cardiac tissue\",\n      \"pmids\": [\"17054951\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Kv1.3/Kv1.5 heterotetrameric channels are expressed in macrophages with variable Kv1.3/Kv1.5 stoichiometry across mononuclear phagocyte subtypes; the presence of Kv1.5 in the complex confers resistance to Kv1.3-specific pharmacological agents, compromising the efficacy of Kv1.3-targeted treatments for immune modulation.\",\n      \"method\": \"Patch-clamp electrophysiology, pharmacological profiling of heterotetrameric channels in macrophage subsets\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional pharmacological characterization, single lab\",\n      \"pmids\": [\"17157812\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"SUMO-1, -2, and -3 modify Kv1.5 at two membrane-proximal cytoplasmic consensus sites; Kv1.5 interacts with the SUMO-conjugating enzyme Ubc9 in vivo; purified recombinant Kv1.5 is SUMOylated in a minimal in vitro reaction; SUMO-specific proteases SENP2 and Ulp1 deconjugate SUMO from Kv1.5; loss of SUMOylation (site mutations or SENP2 co-expression) causes a ~15 mV hyperpolarizing shift in steady-state inactivation without altering activation, establishing SUMOylation as a post-translational modifier that selectively tunes Kv1.5 inactivation gating.\",\n      \"method\": \"In vivo SUMOylation assays, in vitro reconstituted SUMOylation, co-IP with Ubc9, site-directed mutagenesis of SUMO consensus sites, SENP2 co-expression, whole-cell patch clamp\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution plus mutagenesis plus functional electrophysiology, multiple SUMO isoforms tested\",\n      \"pmids\": [\"17261810\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Membrane cholesterol depletion by methyl-β-cyclodextrin (MCD) causes redistribution of Kv1.5 from cholesterol-enriched clusters into larger clusters dispersed across the plasma membrane, increasing IKur current density; Kv1.5 subunits co-fractionate with low-density sucrose gradient fractions distinct from caveolae, indicating that Kv1.5 localizes to non-caveolar cholesterol-rich microdomains whose disruption augments channel activity.\",\n      \"method\": \"Methyl-β-cyclodextrin cholesterol depletion, sucrose-gradient fractionation, live-cell confocal imaging of GFP-Kv1.5, whole-cell patch clamp in atrial myocytes and neonatal cardiomyocytes\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct live-cell imaging of redistribution correlated with functional current change, multiple techniques\",\n      \"pmids\": [\"17525113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"S-acylation (palmitoylation) of Kv1.5 via hydroxylamine-sensitive thioester bonds on both N- and C-terminal cysteines is required for normal channel surface expression; pharmacological inhibition of S-acylation reduces surface expression, accumulates channel in intracellular compartments, and targets it for proteasomal degradation; C-terminal cysteines govern S-acylation, and mutation of intracellular cysteines paradoxically increases surface expression, suggesting that fatty acylation acts as a quality-control step.\",\n      \"method\": \"Hydroxylamine sensitivity assay for thioester bonds, pharmacological S-acylation inhibition, proteasome inhibitor rescue, time-course surface expression analysis, confocal imaging\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple pharmacological approaches with defined mechanistic readouts\",\n      \"pmids\": [\"17344312\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Caveolin-1 and -3 are required for targeting Kv1.5 to low-density detergent-resistant lipid raft fractions; in cells lacking endogenous caveolin, Kv1.5 association with rafts requires exogenous caveolin co-expression; caveolin-trafficking mutants sequester Kv1.5 in intracellular compartments; wild-type caveolin-1 co-expression induces depolarizing shifts in Kv1.5 activation and inactivation analogous to high membrane cholesterol, indicating caveolin modulates Kv1.5 function by regulating its trafficking to cholesterol-rich microdomains.\",\n      \"method\": \"Sucrose density gradient fractionation, co-immunoprecipitation (channel-caveolin complex), dominant-negative caveolin trafficking mutants, patch-clamp electrophysiology\",\n      \"journal\": \"Molecular pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — biochemical interaction plus trafficking mutant phenotype plus functional gating changes\",\n      \"pmids\": [\"18045854\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The mitochondria-ROS-HIF-1α-Kv1.5 pathway constitutes an O2-sensing mechanism in PASMCs; decreased mitochondrial ROS in PAH creates a pseudohypoxic state that activates HIF-1α and down-regulates Kv1.5 expression, contributing to PASMC depolarization, Ca2+ influx, and the proliferative/apoptosis-resistant phenotype; dichloroacetate (PDK inhibitor) corrects mitochondrial abnormalities and restores Kv1.5 expression in experimental PAH.\",\n      \"method\": \"Fawn-hooded rat model of PAH, dichloroacetate treatment, ROS measurement, HIF-1α manipulation, Kv1.5 expression analysis, patch clamp\",\n      \"journal\": \"American journal of physiology. Heart and circulatory physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic animal model plus pharmacological rescue with pathway validation\",\n      \"pmids\": [\"18083891\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"After internalization, Kv1.5 is rapidly trafficked through Rab5-positive early endosomes and Rab4-positive recycling endosomes; dominant-negative Rab5, Rab4, Rab7, and Rab11 constructs all increase Kv1.5 current density; a fraction of internalized channels traffics to Rab7-positive late endosomes for degradation; Rab4 mediates rapid recycling back to the plasma membrane, establishing a post-internalization trafficking itinerary for the channel.\",\n      \"method\": \"Dominant-negative Rab GTPase expression, colocalization with Rab-positive endosome markers, whole-cell patch clamp\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic dominant-negative approach across four Rab GTPases with functional readout\",\n      \"pmids\": [\"18755741\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"SAP97 overexpression in cardiac myocytes clusters endogenous Kv1.5 subunits at myocyte–myocyte contacts, reduces lateral mobility of GFP-Kv1.5 as measured by FRAP, and increases IKur current density (~74% increase) and single-channel number; in CHO cells, SAP97 organizes freely mobile Kv1.5 into poorly mobile plaque-like clusters, establishing that SAP97 retains and immobilizes Kv1.5 in the plasma membrane to increase functional channel expression.\",\n      \"method\": \"Adenovirus-mediated SAP97 overexpression in neonatal cardiomyocytes, FRAP of GFP-Kv1.5, cell-attached patch clamp, whole-cell patch clamp, immunocytochemistry\",\n      \"journal\": \"American journal of physiology. Heart and circulatory physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — FRAP mobility measurements plus functional current analysis, multiple cell types\",\n      \"pmids\": [\"18245566\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Kv1.5 in macrophages does not target to lipid rafts, whereas Kv1.3/Kv1.5 heteromers in transfected HEK-293 cells do associate with rafts; LPS-induced macrophage activation increases the Kv1.3/Kv1.5 ratio and caveolin expression, redirecting Kv1.5 to lipid rafts; Kvβ2.1 co-expression impairs Kv1.5 raft targeting, and a Cav3(DGV) mutant sequesters Kv1.5 in intracellular vesicles, demonstrating that Kv1.5 membrane microdomain targeting is regulated by partner protein stoichiometry.\",\n      \"method\": \"Sucrose density gradient fractionation, cholesterol-depletion experiments, confocal microscopy, dominant-negative caveolin-3 mutant expression, LPS macrophage activation\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple methods but complex system with cell-type-dependent outcomes\",\n      \"pmids\": [\"18668522\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"FHL1 (four-and-a-half LIM protein 1) was identified as a Kv1.5 binding partner by GST-KCNA5 C-terminal pull-down from human atrium followed by mass spectrometry; co-immunoprecipitation confirmed the interaction in human atrium and CHO cells; FHL1 co-expression markedly increased Kv1.5 current density, shifted activation to more positive potentials, and enhanced slow inactivation extent and speed, identifying FHL1 as a key regulatory component of the IKur complex.\",\n      \"method\": \"GST pull-down from human atrium, mass spectrometry identification, co-immunoprecipitation, confocal colocalization, whole-cell patch clamp in CHO cells\",\n      \"journal\": \"Cardiovascular research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — proteomic discovery confirmed by reciprocal co-IP in native tissue and functional electrophysiology\",\n      \"pmids\": [\"18281375\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Hypoxia suppresses Kv1.5 channel expression in rat pulmonary artery smooth muscle cells via the 15-lipoxygenase/15-HETE pathway; pharmacological inhibition of 15-LOX rescued Kv1.5 mRNA and protein expression under hypoxia and partially restored IKV; exogenous 15-HETE mimicked hypoxia-induced Kv1.5 downregulation and current inhibition, establishing a lipid-mediated mechanism for hypoxic Kv1.5 suppression.\",\n      \"method\": \"15-LOX inhibitor pharmacology, Kv1.5 mRNA/protein expression analysis, whole-cell patch clamp in PASMC, exogenous 15-HETE application\",\n      \"journal\": \"Prostaglandins & other lipid mediators\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological pathway dissection with expression and functional data, single lab\",\n      \"pmids\": [\"18984061\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"T1 domain mutations G182R and E211D in KCNA5 (found in IPAH patients) produce functional channels with accelerated inactivation at more hyperpolarized potentials; mutant channel protein is present predominantly in immature glycosylated form, reduced in expression, and retained intracellularly rather than trafficked to the plasma membrane, demonstrating that the T1 domain regulates both Kv1.5 inactivation kinetics and subcellular localization.\",\n      \"method\": \"Site-directed mutagenesis, whole-cell patch clamp in HEK-293 and COS-1 cells, Western blot for glycosylation state, immunofluorescence for subcellular localization\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — mutagenesis combined with biophysical and biochemical characterization\",\n      \"pmids\": [\"20018952\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Acute hypoxia selectively inhibits Kv1.5 (KCNA5) current in PASMC but not MASMC; KCNA5 overexpression in PASMC confers hypoxia sensitivity to the overexpressed current, whereas overexpression in MASMC, HEK, or COS cells does not, confirming that a PASMC-specific hypoxia-sensing mechanism is required and contributes to intracellular Ca2+ homeostasis regulation during hypoxia.\",\n      \"method\": \"KCNA5 overexpression, whole-cell patch clamp at varying PO2, comparison across cell types\",\n      \"journal\": \"Annals of the New York Academy of Sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — replication of cell-type specificity across multiple cell types, single group\",\n      \"pmids\": [\"19845612\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"A novel KCNA5 mutation deleting 11 amino acids in the N-terminal proline-rich SH3-binding domain causes ~60% loss-of-function in IKur and exerts dominant-negative effects on wild-type Kv1.5 current; pretreatment with the Src inhibitor PP2 prevented v-Src tyrosine kinase from suppressing wild-type Kv1.5 current by ~90%, whereas the mutant channel was unresponsive to v-Src, implicating tyrosine kinase signaling through the SH3-binding domain as a regulatory mechanism.\",\n      \"method\": \"Site-directed mutagenesis, whole-cell patch clamp in transfected cells, Src kinase inhibitor (PP2) pharmacology, dominant-negative analysis\",\n      \"journal\": \"Heart rhythm\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — loss-of-function mutagenesis with mechanistic pathway dissection using kinase inhibitor\",\n      \"pmids\": [\"20638934\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Mutations E48G, A305T, and D322H in Kv1.5 (found in lone AF patients) display preserved surface expression and gain-of-function in patch-clamp studies; mutations Y155C, D469E, and P488S display decreased surface expression and loss-of-function; establishing that both gain- and loss-of-function mutations in KCNA5 are associated with atrial fibrillation.\",\n      \"method\": \"Confocal microscopy for surface expression, whole-cell patch-clamp electrophysiology in transfected cells\",\n      \"journal\": \"European heart journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct biophysical characterization of multiple mutations with localization analysis\",\n      \"pmids\": [\"23264583\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The C-terminal domain of Kv1.5 (residues Arg543–Val583) is required for interaction with Kvβ-subunits in a pyridine nucleotide-dependent manner: NADPH accelerates Kv1.5-Kvβ3-mediated inactivation while NADP+ decreases inactivation and reverses the Kvβ2 activation shift; deletion of the C-terminus abolishes these nucleotide-dependent effects; a GST-C-terminal fusion protein binds Kvβ2:NADPH with higher affinity than Kvβ2:NADP+.\",\n      \"method\": \"C-terminal deletion mutagenesis, co-expression with Kvβ2/Kvβ3, whole-cell patch clamp with intracellular NADPH/NADP+ in pipette solution, GST pull-down from mouse brain lysates, structural analysis\",\n      \"journal\": \"Pflugers Archiv\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — mutagenesis combined with biochemical pull-down and functional electrophysiology\",\n      \"pmids\": [\"22426702\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Kv1.5 channel function is required for coronary metabolic dilation: Kv1.5-null mice show impaired myocardial blood flow increase during cardiac stress despite higher cardiac work, and isolated arteries from null mice have impaired relaxation to H2O2 (a reactive oxygen species involved in redox-dependent vasodilation) but normal responses to adenosine and acetylcholine; smooth-muscle-specific rescue of Kv1.5 in null mice restores metabolic dilation, directly linking Kv1.5 in vascular smooth muscle to redox-sensitive coronary flow regulation.\",\n      \"method\": \"Kv1.5 knockout mice, inducible smooth-muscle-specific Kv1.5 re-expression, in vivo myocardial blood flow measurement, tissue O2 tension, isolated artery pharmacology\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic null + tissue-specific rescue establishes cell-type-specific mechanism\",\n      \"pmids\": [\"26224794\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PKC activation reduces Kv1.5 membrane expression and current in Xenopus oocytes and MDCK cells; AMPK activation decreases Kv1.5 membrane expression in MDCK cells but not in atrial HL-1 cells, and this AMPK effect requires co-expression of Nedd4-2 in oocytes, demonstrating that both PKC and AMPK regulate Kv1.5 surface expression through distinct mechanisms.\",\n      \"method\": \"Xenopus oocyte expression, MDCK and HL-1 cell transfection, confocal microscopy, patch clamp, kinase activators and Nedd4-2 co-expression\",\n      \"journal\": \"Channels (Austin, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple cell systems and Nedd4-2 co-expression dependency test, single lab\",\n      \"pmids\": [\"26043299\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Polycomb group (PcG) proteins BMI-1 and EZH2 repress KCNA5 expression in Ewing sarcoma and neuroblastoma cells; the KCNA5 promoter bears H3K27me3 repressive marks that increase under hypoxia; genetic/pharmacological inhibition of BMI-1/EZH2 restores KCNA5 expression; ectopic Kv1.5 channel expression induces apoptotic cell death under hypoxic stress, establishing PcG-mediated epigenetic silencing of KCNA5 as a mechanism promoting cancer cell survival.\",\n      \"method\": \"Chromatin immunoprecipitation for H3K27me3, pharmacological EZH2 inhibition, genetic BMI-1 inhibition, ectopic KCNA5 overexpression, cell death assays under hypoxia\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — ChIP plus genetic/pharmacological perturbation with defined phenotypic outcome\",\n      \"pmids\": [\"25435365\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"DNA methylation of the KCNA5 CpG island promoter in Ewing sarcoma stably silences Kv1.5 channel expression; treatment with the DNA methylation inhibitor decitabine reverses KCNA5 methylation, restores Kv1.5 channel function, and inhibits Ewing sarcoma cell proliferation, demonstrating that epigenetic KCNA5 silencing contributes functionally to tumor cell proliferation.\",\n      \"method\": \"Methylation array and bisulfite sequencing, decitabine treatment, flow cytometry/electrophysiology to confirm Kv1.5 restoration, proliferation assays\",\n      \"journal\": \"Molecular cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological demethylation with functional rescue and proliferation phenotype\",\n      \"pmids\": [\"26573141\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"miR-1 directly targets the KCNA5 3'-UTR as confirmed by luciferase reporter assay; miR-1 transfection in pulmonary artery smooth muscle cells reduces Kv1.5 current and induces membrane depolarization; miR-1 is elevated in lungs from a PAH rat model, and Kv1.5 is correspondingly decreased; antagomiR-1 prevents Kv1.5 downregulation and depolarization induced by hypoxia/Su5416.\",\n      \"method\": \"Luciferase 3'-UTR reporter assay, miR-1 transfection in PASMC, patch clamp (DPO-1-sensitive current), antagomiR-1 treatment in PAH rat model\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — validated direct miRNA target with functional rescue in disease model\",\n      \"pmids\": [\"29717493\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"miR-3940-5p promotes granulosa cell proliferation by directly targeting KCNA5; luciferase reporter assay validated KCNA5 as a miR-3940-5p target; functional analysis confirmed that miR-3940-5p-driven proliferation is KCNA5-dependent, identifying KCNA5 as a downstream effector of miR-3940-5p in polycystic ovary syndrome-associated granulosa cell biology.\",\n      \"method\": \"Luciferase 3'-UTR reporter assay, miR-3940-5p overexpression, KCNA5 knockdown rescue experiment, proliferation assays\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — validated miRNA target with functional rescue, single lab\",\n      \"pmids\": [\"32019676\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"KCNA5 variants Arg184Pro and Gly384Arg found in PAH patients produce clear loss-of-function as assessed by patch clamp in HEK293 cells; Arg184Pro also reduces Kv1.5 protein expression; transfection with either variant decreases apoptosis in human PASMC compared to wild-type, demonstrating that loss-of-function KCNA5 variants impair both channel activity and the apoptotic response in vascular smooth muscle cells.\",\n      \"method\": \"Patch-clamp electrophysiology in HEK293, flow cytometry for apoptosis in human PASMC, Western blot, confocal microscopy, molecular modeling\",\n      \"journal\": \"American journal of respiratory cell and molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — biophysical characterization combined with cell viability phenotype in disease-relevant cell type\",\n      \"pmids\": [\"36917789\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KCNA5 encodes the voltage-gated K+ channel α-subunit Kv1.5, which forms homo- or heterotetrameric delayed-rectifier channels (IKur) in human atrial myocytes and pulmonary artery smooth muscle cells (PASMC); its surface expression and gating are regulated by post-translational modifications (SUMOylation shifting inactivation, S-acylation for quality-control trafficking, tyrosine phosphorylation by Src suppressing current), by scaffolding proteins (SAP97 retaining channels at the plasma membrane, FHL1 increasing current density and modulating gating, α-actinin-2 linking channels to the actin cytoskeleton), by dynein/Rab-GTPase-dependent endosomal recycling and proteasomal degradation, by cholesterol-rich microdomain targeting via caveolin, and by regulatory Kvβ subunits whose redox-sensitive (pyridine nucleotide-dependent) interaction with the channel C-terminus tunes inactivation; in PASMC, Kv1.5 functions as a hypoxia-sensitive O2 sensor downstream of a mitochondria–ROS–HIF-1α pathway, and its loss (through genetic mutations, epigenetic silencing by Polycomb proteins or DNA methylation, or miR-1/miR-3940-5p-mediated suppression) reduces K+ efflux, depolarizes the membrane, inhibits apoptosis, and promotes the proliferative phenotype underlying pulmonary arterial hypertension and tumor cell survival.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"KCNA5 encodes Kv1.5, a voltage-gated potassium channel α-subunit that conducts the ultrarapid delayed rectifier current (IKur) in human atrial myocytes and regulates membrane potential in pulmonary and coronary vascular smooth muscle cells. Kv1.5 surface expression is controlled by SAP97-mediated scaffolding at intercalated disks, dynein/dynactin-dependent retrograde trafficking, Rab5/Rab4/Rab7 endosomal sorting, caveolin-dependent targeting to cholesterol-enriched microdomains, S-acylation of C-terminal cysteines, and proteasomal degradation [PMID:11709425, PMID:16051887, PMID:18755741, PMID:18045854, PMID:17344312, PMID:16185660]. Channel gating is modulated by Kvβ subunits through a C-terminal domain (Arg543–Val583) in a pyridine nucleotide–redox-dependent manner and by Src-family tyrosine kinases via an N-terminal SH3-binding domain, while PKC and AMPK reduce surface expression through distinct mechanisms [PMID:22426702, PMID:20638934, PMID:26043299]. Kv1.5-mediated K⁺ efflux is a determinant of apoptosis in pulmonary artery smooth muscle cells and endothelial cells, and loss-of-function KCNA5 variants found in pulmonary arterial hypertension patients impair apoptosis and promote vascular remodeling, while both gain- and loss-of-function mutations are associated with early-onset atrial fibrillation [PMID:15140747, PMID:36917789, PMID:23264583, PMID:26573141].\",\n  \"teleology\": [\n    {\n      \"year\": 1995,\n      \"claim\": \"Establishing where Kv1.5 resides in native cardiac tissue resolved whether this cloned channel operates at specific membrane domains: Kv1.5 concentrates at intercalated disks of atrial and ventricular myocytes, colocalizing with connexin and N-cadherin.\",\n      \"evidence\": \"Immunofluorescence with two distinct anti-Kv1.5 antibodies and colocalization with junctional markers in human cardiac tissue\",\n      \"pmids\": [\"7615797\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of intercalated disk targeting unknown\", \"Functional significance of polarized localization not tested electrophysiologically\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Identifying the molecular scaffold that anchors Kv1.5 at intercalated disks revealed that SAP97 binds the Kv1.5 C-terminal PDZ motif (T-D-L) and augments IKur, though subsequent work showed SAP97-mediated current enhancement depends on the N-terminus rather than the PDZ motif.\",\n      \"evidence\": \"Co-IP with PDZ motif mutagenesis in COS-7 cells, electrophysiology in oocytes, FRAP and adenoviral overexpression in neonatal cardiomyocytes\",\n      \"pmids\": [\"11709425\", \"12860415\", \"18245566\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contributions of PDZ-dependent anchoring versus N-terminal-dependent current augmentation unresolved\", \"Native cardiac SAP97 knockdown not performed\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Demonstrating that Kv1.5-mediated K⁺ efflux drives apoptotic volume decrease and caspase-3 activation established the channel as a direct regulator of programmed cell death in vascular smooth muscle.\",\n      \"evidence\": \"Kv1.5 overexpression in COS-7 and rat PASMC with patch-clamp, caspase-3 assay, flow cytometry, and 4-AP pharmacological blockade\",\n      \"pmids\": [\"15140747\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream signaling between K⁺ efflux and caspase activation not defined\", \"Whether endogenous Kv1.5 levels are sufficient to trigger apoptosis in vivo unclear\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Defining the trafficking machinery that removes Kv1.5 from the plasma membrane showed that dynein/dynactin-mediated retrograde transport constitutively internalizes channels, and that proteasomal (not lysosomal) degradation sets the ~6.7 h half-life of Kv1.5 protein.\",\n      \"evidence\": \"Dominant-negative p50/dynamitin, nocodazole, dynamin inhibition, pulse-chase with proteasome/lysosome inhibitors, co-IP of dynein complex in HEK and rat cardiac myocytes\",\n      \"pmids\": [\"16051887\", \"16185660\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"E3 ubiquitin ligase responsible for Kv1.5 ubiquitination not identified\", \"Whether dynein interaction is direct or via adaptor proteins unclear\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Showing that acute hypoxia selectively inhibits Kv1.5 in PASMC but not in other cell types expressing the same channel established that a PASMC-intrinsic oxygen-sensing mechanism converges on Kv1.5, later linked to the 15-LOX/15-HETE pathway.\",\n      \"evidence\": \"Heterologous Kv1.5 expression in PASMC vs. MASMC/HEK/COS-7 with hypoxia, patch-clamp; 15-LOX inhibitors and exogenous 15-HETE in PASMC\",\n      \"pmids\": [\"16236819\", \"18984061\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the direct oxygen sensor upstream of 15-LOX not determined\", \"Whether other Kv channels share this selectivity mechanism unknown\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Resolving how lipid environment regulates Kv1.5 showed that cholesterol-enriched microdomains (distinct from caveolae) concentrate the channel, and that caveolin is required for trafficking Kv1.5 to these raft domains, while S-acylation at C-terminal cysteines independently regulates surface stability.\",\n      \"evidence\": \"Cholesterol depletion/repletion with patch-clamp and live imaging; sucrose gradient fractionation in caveolin-null/reconstituted cells; hydroxylamine-sensitive palmitoylation assay with cysteine mutagenesis\",\n      \"pmids\": [\"17525113\", \"18045854\", \"17344312\", \"17054951\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific palmitoyl acyltransferase catalyzing Kv1.5 S-acylation not identified\", \"Relationship between S-acylation and caveolin-dependent raft targeting not tested\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Mapping the post-endocytic itinerary of Kv1.5 through Rab GTPase compartments showed rapid Rab5-to-Rab4 recycling as the dominant pathway, with a fraction diverted to Rab7-dependent degradation, while FHL1 was identified as a new binding partner that increases current density.\",\n      \"evidence\": \"Dominant-negative Rab5/4/7 constructs with patch-clamp in H9c2 and HEK cells; GST pulldown/mass spectrometry from human atrial tissue with co-IP and electrophysiology in CHO cells\",\n      \"pmids\": [\"18755741\", \"18281375\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How FHL1 increases Kv1.5 current (trafficking vs. gating) not dissected\", \"Rab-mediated sorting signals on Kv1.5 not mapped\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identifying the N-terminal SH3-binding domain as the target for Src-family tyrosine kinase suppression of Kv1.5 established a signaling axis distinct from C-terminal regulatory mechanisms.\",\n      \"evidence\": \"N-terminal deletion mutant lacking proline-rich SH3 motif, v-Src coexpression, PP2 inhibitor, patch-clamp in transfected cells\",\n      \"pmids\": [\"20638934\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct phosphorylation site on Kv1.5 by Src not mapped\", \"Physiological triggers activating Src-mediated Kv1.5 suppression in cardiomyocytes unknown\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstrating that Kvβ subunits interact with the Kv1.5 C-terminus (Arg543–Val583) in a pyridine nucleotide–dependent manner established metabolic redox sensing as a gating modulator, while identification of both gain- and loss-of-function KCNA5 mutations in atrial fibrillation patients linked altered IKur in either direction to AF susceptibility.\",\n      \"evidence\": \"C-terminal deletion constructs with intracellular NADPH/NADP⁺ dialysis and patch-clamp; GST pulldown from brain; sequencing of KCNA5 in AF cohort with electrophysiology of each variant\",\n      \"pmids\": [\"22426702\", \"23264583\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of nucleotide-dependent Kvβ–C-terminus interaction not resolved at atomic level\", \"Whether redox modulation is relevant to AF pathophysiology not tested in vivo\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Knockout and smooth-muscle-specific rescue of Kv1.5 in mice demonstrated that the channel is essential for coupling coronary blood flow to metabolic demand via H₂O₂-mediated vasodilation, establishing an in vivo physiological role beyond electrophysiology.\",\n      \"evidence\": \"Kv1.5 null mice, inducible smooth-muscle-specific Kv1.5 transgenic rescue, myocardial blood flow and tissue oxygenation measurements, isolated vessel pharmacology\",\n      \"pmids\": [\"26224794\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism linking H₂O₂ to Kv1.5 activation not defined\", \"Whether Kv1.5 cooperates with other Kv channels in metabolic dilation unknown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Revealing that Polycomb-mediated H3K27me3 and CpG methylation silence KCNA5 in Ewing sarcoma—and that epigenetic reactivation restores Kv1.5-dependent apoptosis—established a cancer-relevant mechanism of channel silencing.\",\n      \"evidence\": \"ChIP for H3K27me3, bisulfite sequencing, BMI-1/EZH2 inhibitors, decitabine treatment, ectopic KCNA5 expression with hypoxia-induced apoptosis assays\",\n      \"pmids\": [\"26573141\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Generalizability of epigenetic silencing beyond Ewing sarcoma not established\", \"Whether Kv1.5-driven apoptosis is the primary effector of decitabine's antiproliferative effect unclear\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Functional characterization of PAH-associated KCNA5 variants (Arg184Pro, Gly384Arg) confirmed that loss of Kv1.5 channel function directly impairs apoptosis in human PASMC, reinforcing the mechanistic link between KCNA5 loss-of-function and pulmonary vascular remodeling.\",\n      \"evidence\": \"Patch-clamp of mutant channels in HEK293 cells, flow cytometry for apoptosis in human PASMC, western blot, confocal microscopy\",\n      \"pmids\": [\"36917789\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether KCNA5 variants are causative or contributory to PAH not resolved by family segregation\", \"In vivo PAH model with these specific variants not generated\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the identity of the E3 ubiquitin ligase for Kv1.5, the direct oxygen/redox sensor in PASMC, the structural basis of the Kvβ–C-terminus nucleotide-dependent interaction, and whether KCNA5 loss-of-function variants are sufficient to cause PAH in segregation studies.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"E3 ligase identity unknown\", \"PASMC-specific oxygen sensor not identified\", \"No high-resolution structure of Kv1.5 with Kvβ and nucleotide\", \"Causality of KCNA5 variants in PAH not established by family genetics\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [1, 6, 7, 10, 25, 26, 30, 33]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 4, 13, 14, 21, 22, 25]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [16]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [16]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [6, 28, 33, 34]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [1, 7, 10, 25, 26, 30]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [23, 27]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [9, 14, 15, 16]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [28, 29]}\n    ],\n    \"complexes\": [\n      \"Kv1.5 homotetramer\",\n      \"Kv1.3/Kv1.5 heterotetramer\",\n      \"Kv1.5/Kvβ complex\"\n    ],\n    \"partners\": [\n      \"DLG1\",\n      \"FHL1\",\n      \"DYNC1H1\",\n      \"DCTN2\",\n      \"CAV1\",\n      \"KCNAB2\",\n      \"KCNA3\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"KCNA5 encodes the Kv1.5 voltage-gated potassium channel α-subunit, which forms Shaker-family delayed-rectifier channels (IKur) that regulate membrane potential in human atrial myocytes, pulmonary artery smooth muscle cells (PASMC), macrophages, and coronary vascular smooth muscle. Surface density and gating of Kv1.5 are tuned by a network of post-translational modifications—SUMOylation selectively shifts inactivation [PMID:17261810], S-acylation serves as a quality-control checkpoint for ER-to-surface trafficking [PMID:17344312], Src-mediated tyrosine phosphorylation suppresses current [PMID:8953041], and Kvβ subunit association confers pyridine-nucleotide-dependent inactivation modulation [PMID:22426702]—while scaffolding by SAP97 immobilizes channels at plasma membrane contact sites [PMID:18245566], dynein/Rab-GTPase-dependent endosomal recycling and proteasomal degradation set the channel's half-life [PMID:16185660, PMID:18755741], and cholesterol-rich microdomain targeting via caveolin modulates gating [PMID:18045854]. In PASMC, Kv1.5 acts as the principal O₂-sensitive K⁺ channel mediating hypoxic pulmonary vasoconstriction; its loss—through loss-of-function mutations, Polycomb/DNA-methylation-mediated epigenetic silencing, or miR-1-directed repression—reduces K⁺ efflux, depolarizes the membrane, inhibits apoptosis, and drives the proliferative vascular remodeling of pulmonary arterial hypertension [PMID:15217912, PMID:18083891, PMID:36917789, PMID:25435365, PMID:29717493]. Both gain- and loss-of-function KCNA5 mutations are associated with atrial fibrillation [PMID:23264583].\",\n  \"teleology\": [\n    {\n      \"year\": 1991,\n      \"claim\": \"Molecular cloning of KCNA5 from human heart and insulinoma tissue and reconstitution in Xenopus oocytes established that the gene encodes a Shaker-family, 4-AP-sensitive delayed-rectifier K⁺ channel, answering the fundamental question of its molecular identity and basic electrophysiology.\",\n      \"evidence\": \"cDNA cloning and two-electrode voltage clamp in Xenopus oocytes, two independent groups\",\n      \"pmids\": [\"2001794\", \"1986382\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Tetrameric stoichiometry and heteromeric partner compatibility not yet determined\", \"Native tissue current identity not established\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Immunolocalization of Kv1.5 to intercalated disks in human atrial and ventricular myocytes, and to vascular smooth muscle, established the channel's native tissue distribution and suggested distinct functional roles in cardiac conduction and vascular tone.\",\n      \"evidence\": \"Epitope-specific immunofluorescence with confocal colocalization in explanted human cardiac tissue\",\n      \"pmids\": [\"7615797\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional contribution of Kv1.5 to the native IKur current not yet proven by loss-of-function\", \"Subcellular microdomain localization not resolved\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Discovery that Src tyrosine kinase directly binds the Kv1.5 N-terminal proline-rich SH3-binding domain and that Kvβ2.1 co-assembles with Kv1.5 to shift gating revealed that the channel operates as a signaling complex rather than an autonomous pore, opening the question of how multiple interactors coordinately regulate IKur.\",\n      \"evidence\": \"Co-immunoprecipitation from transfected cells and native human myocardium; Kvβ2.1 cloning and co-expression electrophysiology in HEK293 cells\",\n      \"pmids\": [\"8953041\", \"8576199\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the tyrosine phosphatase opposing Src not known\", \"In vivo significance of Kvβ modulation untested\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Identification of SAP97 as a PDZ-domain scaffold that clusters and immobilizes Kv1.5 at the plasma membrane, augmenting IKur, established a membrane-retention mechanism; subsequent work showed the functional effect depends on the Kv1.5 N-terminus and may be partially indirect.\",\n      \"evidence\": \"Co-immunoprecipitation, C-terminal mutagenesis, oocyte electrophysiology; later FRAP mobility measurements and N-terminal deletion analysis\",\n      \"pmids\": [\"11709425\", \"18245566\", \"12860415\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the N-terminal dependence reflects an intermediary bridging protein is unknown\", \"SAP97-Kv1.5 stoichiometry and structure unresolved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Demonstration that Kv1.5 is the predominant O₂-sensitive Kv channel in resistance PASMCs—and that K⁺ efflux through it promotes apoptotic volume decrease and caspase activation—linked the channel directly to hypoxic pulmonary vasoconstriction and to apoptosis regulation.\",\n      \"evidence\": \"Intracellular anti-Kv1.5 antibody application in native PASMCs plus KCNA5 overexpression with caspase-3 and apoptosis assays\",\n      \"pmids\": [\"15217912\", \"15140747\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular identity of the PASMC-specific hypoxia sensor upstream of Kv1.5 not defined\", \"Contribution of Kv1.5 versus Kv2.1 to HPV quantitatively uncertain\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Characterization of dynein-dependent retrograde trafficking and ubiquitin-proteasomal degradation of Kv1.5 revealed that channel surface density is dynamically controlled by motor-mediated internalization and protein turnover, not solely by biosynthetic delivery.\",\n      \"evidence\": \"Dominant-negative dynein/dynamin experiments, nocodazole, proteasome inhibitors (MG132/ALLN), pulse-chase with functional electrophysiology\",\n      \"pmids\": [\"16051887\", \"16185660\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"E3 ubiquitin ligase targeting Kv1.5 not identified\", \"Signals triggering accelerated internalization in disease states unknown\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Three post-translational regulatory axes were defined: SUMOylation selectively shifts Kv1.5 inactivation, S-acylation acts as an ER quality-control checkpoint for surface delivery, and caveolin directs Kv1.5 to cholesterol-rich microdomains that modulate gating—collectively showing that multiple lipid and protein modifications independently tune channel function.\",\n      \"evidence\": \"In vitro and in vivo SUMOylation assays with mutagenesis and electrophysiology; hydroxylamine sensitivity and acylation inhibitor studies; caveolin co-expression with sucrose fractionation and patch clamp\",\n      \"pmids\": [\"17261810\", \"17344312\", \"18045854\", \"17525113\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"SUMO E3 ligase and stimulus-dependent regulation of channel SUMOylation not identified\", \"Specific palmitoyl acyltransferase for Kv1.5 unknown\", \"Relative contribution of each modification to native IKur regulation untested\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Mapping the post-endocytic itinerary through Rab5→Rab4 (rapid recycling) and Rab7 (degradation) compartments, and identification of FHL1 as a Kv1.5 C-terminal interactor that enhances current density and modulates gating, completed a picture of both vesicular and scaffolding control of channel availability.\",\n      \"evidence\": \"Dominant-negative Rab GTPase colocalization and electrophysiology; GST pull-down/mass spectrometry from human atrium with co-IP and patch clamp\",\n      \"pmids\": [\"18755741\", \"18281375\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether FHL1 and SAP97 form a ternary complex at the channel is unknown\", \"Recycling kinetics in native cardiomyocytes not measured\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Discovery that Kvβ-subunit interaction with the Kv1.5 C-terminus is redox-tuned by NADPH/NADP⁺, and that both gain- and loss-of-function KCNA5 mutations associate with atrial fibrillation, connected channel redox sensing and genetic variation to cardiac arrhythmia.\",\n      \"evidence\": \"C-terminal deletion mutagenesis with intracellular nucleotide dialysis and GST pull-down; biophysical characterization of AF-associated Kv1.5 mutants\",\n      \"pmids\": [\"22426702\", \"23264583\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Clinical penetrance and population frequency of AF-associated KCNA5 variants not established\", \"Structural basis for pyridine nucleotide selectivity at the Kvβ–C-terminus interface unresolved\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"In vivo knockout and smooth-muscle-specific rescue showed Kv1.5 is required for redox-dependent coronary metabolic dilation; concurrently, Polycomb- and DNA-methylation-mediated epigenetic silencing of KCNA5 was shown to promote cancer cell survival by disabling apoptosis, broadening the channel's functional roles beyond excitable-cell electrophysiology.\",\n      \"evidence\": \"Kv1.5-null mice with inducible SM-specific rescue, isolated artery pharmacology; ChIP for H3K27me3, EZH2/BMI-1 inhibition, decitabine demethylation with proliferation assays\",\n      \"pmids\": [\"26224794\", \"25435365\", \"26573141\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether coronary metabolic dilation phenotype relates to PASMC O₂-sensing pathway is unclear\", \"Whether epigenetic silencing of KCNA5 occurs in PAH patient lungs not shown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Validation of miR-1 as a direct KCNA5 3′-UTR targeting miRNA that is elevated in PAH lungs and suppresses Kv1.5 expression, with antagomiR rescue, established post-transcriptional repression as another layer of Kv1.5 downregulation in pulmonary vascular disease.\",\n      \"evidence\": \"Luciferase 3′-UTR reporter, miR-1 transfection in PASMC with patch clamp, antagomiR-1 in PAH rat model\",\n      \"pmids\": [\"29717493\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contribution of miR-1 versus epigenetic silencing versus transcriptional repression in human PAH not quantified\", \"Upstream signals inducing miR-1 in PAH lungs not defined\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Functional characterization of PAH-associated KCNA5 variants (Arg184Pro, Gly384Arg) as loss-of-function mutations that impair both channel activity and PASMC apoptosis provided the strongest genetic evidence that KCNA5 deficiency directly contributes to PAH pathogenesis.\",\n      \"evidence\": \"Patch-clamp electrophysiology in HEK293, apoptosis assays in human PASMC, Western blot, molecular modeling\",\n      \"pmids\": [\"36917789\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Segregation data in PAH families not provided for these variants\", \"Whether these variants affect heteromeric channel assembly (e.g., with Kv1.3 or Kv2.1) is untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Major unresolved questions include the molecular identity of the PASMC-specific O₂ sensor that inhibits Kv1.5, the E3 ubiquitin ligase responsible for proteasomal targeting, the high-resolution structure of human Kv1.5 in complex with regulatory subunits (Kvβ, SAP97, FHL1), and whether KCNA5 loss-of-function mutations are causative for heritable PAH as demonstrated by family segregation and rescue studies.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No PASMC-specific O₂ sensor molecularly identified\", \"E3 ligase for Kv1.5 unknown\", \"No cryo-EM or X-ray structure of human Kv1.5 reported in timeline\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 1, 12, 14]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [2, 9, 15, 22, 24, 27]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [17, 23, 31]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [26]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [26, 28]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 1, 14]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 8, 21, 25, 37]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 1, 12, 14, 36]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [13, 38, 42]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [17, 21, 23]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [15, 26, 24]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [25, 34, 40, 42]}\n    ],\n    \"complexes\": [\n      \"Kv1.5 homotetramer (IKur)\",\n      \"Kv1.3/Kv1.5 heterotetramer\",\n      \"Kv1.5–Kvβ2/Kvβ3 complex\"\n    ],\n    \"partners\": [\n      \"SRC\",\n      \"SAP97\",\n      \"ACTN2\",\n      \"FHL1\",\n      \"KCNAB2\",\n      \"CAV1\",\n      \"UBC9\",\n      \"PTPRE\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}