{"gene":"KCNB1","run_date":"2026-06-10T01:55:23","timeline":{"discoveries":[{"year":2006,"finding":"Kv2.1 is graded-regulated by variable phosphorylation: mass spectrometry-SILAC identified 16 phosphorylation sites, of which 7 are dephosphorylated by calcineurin. Mutation of individual calcineurin-regulated sites to alanine produced incremental hyperpolarizing shifts in voltage-dependent activation, while aspartate mutations conferred resistance to calcineurin. Multiple site mutations were additive, demonstrating that variable phosphorylation at many sites allows graded, activity-dependent regulation of Kv2.1 gating and neuronal firing.","method":"Mass spectrometry-SILAC, site-directed mutagenesis, whole-cell patch-clamp","journal":"Science","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal methods (MS-SILAC, mutagenesis, electrophysiology) in a single rigorous study with graded functional validation","pmids":["16917065"],"is_preprint":false},{"year":1995,"finding":"Hanatoxin (HaTx1/2) from Chilean tarantula venom inhibits Kv2.1 channels with Kd ~42 nM via a bimolecular reaction. The toxin binding site is distinct from the scorpion toxin site (S5-S6 linker), as regions outside this linker determine HaTx sensitivity. Shaker-, Shaw-, and eag-family channels are relatively insensitive, while Shal-related channels are sensitive.","method":"Peptide isolation, bacterial expression, voltage-clamp electrophysiology, kinetic analysis","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with synthetic toxin plus rigorous kinetic characterization, replicated in multiple channel types","pmids":["7576642"],"is_preprint":false},{"year":2003,"finding":"Kv2.1-encoded K+ channels are necessary and sufficient for the apoptotic K+ efflux in cortical neurons. Dominant-negative Kv2.1 expression eliminated the enhancement of K+ currents accompanying apoptosis and protected neurons from oxidant- and staurosporine-induced death. CHO cells (lacking endogenous voltage-gated K+ channels) became more susceptible to apoptosis after Kv2.1 transfection.","method":"Dominant-negative expression, whole-cell patch-clamp, cell viability assays","journal":"The Journal of Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean dominant-negative KO with defined phenotypic readout, replicated in two cell types with multiple apoptogenic stimuli","pmids":["12832499"],"is_preprint":false},{"year":2002,"finding":"Kv2.1 is the dominant voltage-dependent K+ channel in pancreatic beta-cells, responsible for action potential repolarization. Dominant-negative knockout of Kv2.1 enhanced glucose-stimulated insulin secretion. A selective Kv2.1 antagonist (C-1) blocked Kv2.1-mediated currents, enhanced membrane depolarization and Ca2+ responses to glucose, and augmented first- and second-phase insulin secretion from perfused pancreas.","method":"Dominant-negative expression, whole-cell patch-clamp, intracellular Ca2+ imaging, isolated islet perfusion","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — dominant-negative KO plus pharmacological inhibition with multiple orthogonal readouts across multiple preparations","pmids":["12270920"],"is_preprint":false},{"year":1997,"finding":"Phosphorylation of the Kv2.1 C-terminal cytoplasmic domain (residues 667–853) shifts voltage-dependent activation to more depolarized potentials. Intracellular alkaline phosphatase eliminated differences in voltage dependence between wild-type and C-terminal truncation mutants, demonstrating that C-terminal phosphorylation directly modulates Kv2.1 gating. Phosphorylation was restricted to serine residues.","method":"Truncation mutagenesis, 32P in vivo labeling, phosphoamino acid analysis, whole-cell patch-clamp with intracellular alkaline phosphatase","journal":"Molecular Pharmacology","confidence":"High","confidence_rationale":"Tier 1 / Strong — combined biochemical phosphorylation mapping and electrophysiological dephosphorylation rescue, multiple mutants tested","pmids":["9351973"],"is_preprint":false},{"year":1996,"finding":"A cytoplasmic domain of Kv2.1 (amino acids 536–666 in the C-terminus) is necessary and sufficient for polarized lateral membrane targeting and high-density cluster formation. This domain also correlates with detergent insolubility, suggesting interaction with the detergent-insoluble cytoskeleton underlies proper localization.","method":"C-terminal truncation mutants expressed in MDCK cells, chimeric HA-Kv2.1 constructs, immunofluorescence, detergent solubility assay","journal":"The Journal of Cell Biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — domain-swap chimera plus truncation series with clear localization phenotype in polarized cells","pmids":["8978827"],"is_preprint":false},{"year":2010,"finding":"Clustered Kv2.1 channels do not efficiently conduct K+; nonclustered channels carry the high-threshold delayed-rectifier current. Only ~2% of surface channels conduct. Dephosphorylation (alkaline phosphatase) caused a 25 mV hyperpolarizing shift without increasing whole-cell current, while actin depolymerization-induced declustering did not alter activation midpoint. Thus clusters do not contain a reservoir of non-conducting channels released upon declustering.","method":"Cell-attached patch clamp at defined surface locations (clustered vs. non-clustered), FRAP, alkaline phosphatase treatment, actin depolymerization","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 1 / Strong — cell-attached single-channel recordings with spatial resolution, multiple orthogonal perturbations in same study","pmids":["20566856"],"is_preprint":false},{"year":2015,"finding":"Kv2.1 clustering directly induces stable endoplasmic reticulum–plasma membrane junctions (EPJs). Using TIRF and electron microscopy, clustered Kv2.1 was shown to tether cortical ER to the plasma membrane in HEK 293 cells and hippocampal neurons. These non-conducting clusters serve as membrane-trafficking hubs for delivery and retrieval of multiple membrane proteins. Glutamate exposure causes loss of Kv2.1 clusters and retraction of cortical ER from the plasma membrane.","method":"TIRF microscopy, electron microscopy, live imaging, glutamate treatment","journal":"Journal of Cell Science","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — two orthogonal imaging modalities (TIRF + EM) with functional consequence (ER retraction upon glutamate), in two cell systems","pmids":["25908859"],"is_preprint":false},{"year":2011,"finding":"AMPK directly phosphorylates Kv2.1 at S440 and S537. Phosphorylation at S440 (but not S537) mediates hyperpolarizing shifts in voltage-dependent activation and inactivation. In cultured rat hippocampal neurons, AMPK activation reduced neuronal firing frequency. Effects were abolished by S440A substitution, confirmed by phosphospecific antibodies and quantitative mass spectrometry.","method":"In vitro kinase assay, phosphospecific antibodies, quantitative mass spectrometry, site-directed mutagenesis, whole-cell patch-clamp, intracellular dialysis with thiophosphorylated AMPK","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct kinase assay plus mutagenesis plus in-cell confirmation with phosphospecific antibodies and MS, replicated in neurons","pmids":["22006306"],"is_preprint":false},{"year":2011,"finding":"SUMO1 is conjugated to Kv2.1 at lysine K470 on the neuronal cell surface, shifting the half-maximal activation voltage (V1/2) by up to 35 mV. Only K470 is sumoylated; no more than two non-adjacent subunits in the tetramer carry SUMO concurrently. One SUMO shifts V1/2 by 15 mV; two SUMOs produce the full response, demonstrating graded regulation of neuronal excitability.","method":"SUMO conjugation assays, K470 mutagenesis, single-channel recordings, immunostaining of native SUMO and Kv2.1 in hippocampal neurons","journal":"The Journal of General Physiology","confidence":"High","confidence_rationale":"Tier 1 / Strong — site-specific mutagenesis identifying single SUMO acceptor plus single-channel electrophysiology with graded response quantification","pmids":["21518833"],"is_preprint":false},{"year":2011,"finding":"CDK5 directly phosphorylates Kv2.1 and determines the constitutive high phosphorylation state of the channel in neurons. CDK5 also controls the rapid increase in Kv2.1 phosphorylation upon activity blockade and the recovery of phosphorylation after stimulus-induced dephosphorylation. CDK5 regulation of Kv2.1 is independent of CDK5's previously described regulation of PP1.","method":"In vitro kinase assay, CDK5 inhibition (pharmacological and genetic), phosphospecific antibody immunoblotting in hippocampal neurons","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct in vitro phosphorylation plus in-neuron phosphorylation state readouts, single lab but multiple orthogonal approaches","pmids":["21712386"],"is_preprint":false},{"year":2006,"finding":"The Kv2.1 cytoplasmic C-terminal domain is an autonomous transferable module sufficient to confer Kv2.1-like phosphorylation-dependent clustering, voltage-dependent activation, and muscarinic (cholinergic) modulation to heterologous Kv channels. Cholinergic stimulation triggers Ca2+/calcineurin-dependent dephosphorylation of Kv2.1, dispersal of clusters, and hyperpolarizing shifts in gating.","method":"Chimeric Kv channel constructs, immunocytochemistry, biochemical phosphorylation assays, patch-clamp in HEK293 cells and hippocampal neurons","journal":"The Journal of Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — domain-swap chimeras with comprehensive biochemical, cell biological, and electrophysiological validation","pmids":["16407566"],"is_preprint":false},{"year":1998,"finding":"Kv5.1 and Kv6.1 are regulatory (silent) alpha-subunits that coassemble with Kv2.1 into heterotetrameric channels with altered gating. Kv2.1/Kv5.1 selectively accelerated inactivation at intermediate potentials and cumulative inactivation, and slowed deactivation. Kv2.1/Kv6.1 shifted activation to negative potentials and markedly slowed deactivation. Heteromeric assembly was confirmed by co-immunoprecipitation and single-channel conductance heterogeneity.","method":"Two-electrode voltage-clamp in Xenopus oocytes, co-immunoprecipitation, single-channel recordings","journal":"The American Journal of Physiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal biochemical pulldown plus single-channel recordings plus gating analysis, replicated across two silent subunits","pmids":["9696692"],"is_preprint":false},{"year":1996,"finding":"Kv6.1 and Kv2.1 form heterotetrameric channels with a novel current distinct from homomeric Kv2.1, including decreased deactivation rates, decreased TEA sensitivity, and a hyperpolarizing shift of half-maximal activation. Protein-protein interaction between Kv2.1 and Kv6.1 N-termini was confirmed by yeast two-hybrid; Kv6.1 amino termini could not form homomultimers but specifically interacted with Kv2.1 N-termini.","method":"Two-electrode voltage-clamp in Xenopus oocytes, yeast two-hybrid assay","journal":"FEBS Letters","confidence":"High","confidence_rationale":"Tier 2 / Strong — yeast two-hybrid plus functional electrophysiology of novel heteromeric current, two orthogonal methods","pmids":["8980147"],"is_preprint":false},{"year":2006,"finding":"Kv2.1 surface clusters are bounded by a cortical actin-based perimeter fence. Channels within clusters are mobile (FRAP tau ~14 s) but are retained within the cluster boundary. Latrunculin A treatment caused cluster enlargement and loss of soma restriction, demonstrating that cortical actin maintains both cluster size and somatic localization. Channels lacking the C-terminus do not form clusters and diffuse freely.","method":"FRAP, quantum dot single-channel tracking, latrunculin A treatment, GFP-Kv2.1 live imaging in HEK cells and hippocampal neurons","journal":"The Journal of Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — FRAP plus single-particle tracking plus actin disruption, replicated in two cell types","pmids":["16988031"],"is_preprint":false},{"year":2012,"finding":"Kv2.1 surface clusters serve as specialized insertion platforms for membrane protein trafficking. TIRF-FRAP and quantum dot imaging showed >85% of cytoplasmic and recycling Kv2.1, and >85% of recycling Kv1.4, are delivered to the cell surface at Kv2.1 cluster perimeters. Actin depolymerization redirected Kv2.1 exocytosis to cluster-free membrane areas.","method":"TIRF-FRAP, quantum dot single-channel imaging, actin depolymerization, live-cell imaging in HEK cells and hippocampal neurons","journal":"Molecular Biology of the Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — two orthogonal live-imaging methods with pharmacological perturbation, replicated in two cell types","pmids":["22648171"],"is_preprint":false},{"year":2019,"finding":"Kv2.1 clustering at ER-plasma membrane junctions promotes spatial and functional coupling of L-type Ca2+ channels (LTCCs) to ryanodine receptor (RyR) ER Ca2+ release channels. Kv2.1 clustering unexpectedly enhanced LTCC opening at polarized membrane potentials. This enabled Kv2.1-LTCC-RyR triads to generate localized Ca2+ sparks independently of action potentials.","method":"Proximity proteomics (BioID), immunofluorescence co-localization, Ca2+ spark imaging, LTCC single-channel recordings, Kv2.1 knockout/knockdown","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — proximity proteomics plus functional imaging plus electrophysiology, multiple orthogonal methods","pmids":["31663850"],"is_preprint":false},{"year":2003,"finding":"SNAP-25 associates with Kv2.1 via the channel's N-terminus and reduces Kv2.1-mediated currents by ~70% in heterologous cells and ~40% in rat beta-cells. Co-dialysis of a Kv2.1 N-terminal peptide partially relieved inhibition. SNAP-25 had no effect on beta-cell K+ currents after dominant-negative Kv2.1 knockout, confirming specificity.","method":"Co-immunoprecipitation, in vitro peptide binding, whole-cell patch-clamp, dominant-negative KO in beta-cells","journal":"Molecular Endocrinology","confidence":"High","confidence_rationale":"Tier 2 / Strong — co-IP plus in vitro binding plus functional electrophysiology with dominant-negative specificity control","pmids":["12403834"],"is_preprint":false},{"year":2004,"finding":"Kv2.1 and CaV1.2 (but not Kv1.4, SUR1, or Kir6.2) localize to cholesterol-rich lipid raft domains in pancreatic beta-cell plasma membranes, along with SNARE proteins syntaxin 1A, SNAP-25, and VAMP-2. Disruption of lipid rafts by methyl-β-cyclodextrin shunts Kv2.1 out of rafts and inhibits Kv2.1 (but not CaV1.2) channel activity, enhancing insulin exocytosis.","method":"Detergent-resistant membrane fractionation, methyl-β-cyclodextrin treatment, whole-cell patch-clamp, single-cell exocytosis imaging","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — biochemical fractionation plus pharmacological disruption plus functional electrophysiology with channel-selective readouts","pmids":["15073181"],"is_preprint":false},{"year":2004,"finding":"Syntaxin 1A (Syx) physically interacts with the Kv2.1 C-terminus at the cell surface, causing hyperpolarizing shifts in steady-state activation and inactivation. Peptides competing for Syx binding to the C-terminus reversed these effects when injected into oocytes already co-expressing both proteins. The t-SNARE complex (Syx/SNAP-25) also binds the Kv2.1 C-terminus and modulates inactivation; partial C-terminal deletions dissipated both interactions.","method":"Competitive peptide injection in Xenopus oocytes, C-terminal deletion mutagenesis, two-electrode voltage-clamp","journal":"Molecular Pharmacology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — competitive peptide displacement plus mutagenesis to causally link physical and functional interactions, single lab","pmids":["15525758"],"is_preprint":false},{"year":2003,"finding":"Tyrosine 124 in the T1 cytosolic domain of Kv2.1 is phosphorylated by Src kinase in vitro and in cells. Y124 phosphorylation is critical for Src-mediated upregulation (~3-fold) of Kv2.1 K+ current; Y124F mutation greatly reduced current upregulation by Src. The phosphatase cyt-PTPepsilon dephosphorylates Y124, counteracting Src. Expression, localization, and voltage dependence were unchanged in Y124F channels.","method":"In vitro kinase assay, substrate-trapping mutant co-IP, site-directed mutagenesis (Y124F), whole-cell patch-clamp","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assay plus substrate-trapping plus mutagenesis with functional electrophysiology readout","pmids":["12615930"],"is_preprint":false},{"year":2008,"finding":"Extrasynaptic (but not synaptic) NMDA receptor activation potently unclusters and dephosphorylates Kv2.1, producing a hyperpolarizing shift in voltage-dependent activation of hippocampal I_K. Inhibition of glutamate transporters (EAAT2) activated extrasynaptic NMDA receptors and dephosphorylated Kv2.1. Moderate seizure activity in vivo did not dephosphorylate Kv2.1, demonstrating specificity for extrasynaptic receptor pools.","method":"Bath NMDA application, selective extrasynaptic NMDA receptor activation, EAAT inhibition, immunoblot for Kv2.1 phosphorylation, immunofluorescence cluster analysis, whole-cell patch-clamp","journal":"The Journal of Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — pharmacological dissection of synaptic vs. extrasynaptic receptors with both biochemical and functional readouts, in vitro and in vivo","pmids":["18753382"],"is_preprint":false},{"year":2013,"finding":"CaMKII activation (triggered by oxidant-induced intracellular Ca2+ release) is required for the pro-apoptotic insertion of Kv2.1 channels into the plasma membrane. CaMKII modulates the interaction of syntaxin with Kv2.1, enabling the SNARE-dependent membrane insertion responsible for the K+ current surge that drives apoptotic K+ loss. CaMKII inhibition prevented K+ current enhancement and increased neuronal viability.","method":"Pharmacological and molecular CaMKII inhibition, intracellular Ca2+ imaging, whole-cell patch-clamp, syntaxin-Kv2.1 co-IP, cell viability assay","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 2 / Strong — Ca2+ imaging plus protein interaction plus electrophysiology plus viability, mechanistic cascade established with multiple interventions","pmids":["23918396"],"is_preprint":false},{"year":2011,"finding":"AMIGO (an adhesion protein with LRR and Ig domains) is an auxiliary subunit of the Kv2.1 channel complex, showing extensive co-localization and co-immunoprecipitation with Kv2.1 in mouse brain. AMIGO increases Kv2.1 conductance in a voltage-dependent manner in HEK cells. Inhibition of endogenous AMIGO suppresses neuronal I_K at negative membrane voltages.","method":"Co-immunoprecipitation from mouse brain, immunohistochemistry, whole-cell patch-clamp in HEK cells and hippocampal neurons, endogenous AMIGO RNAi knockdown","journal":"EMBO Reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — native brain co-IP plus heterologous gain-of-function plus endogenous knockdown in neurons, multiple orthogonal methods","pmids":["22056818"],"is_preprint":false},{"year":2003,"finding":"The N- and C-terminal intracellular regions of Kv2.1 interact directly (demonstrated by GST pulldown of the N-terminus binding the C-terminus) and together determine channel activation kinetics. Specific residues in the N-terminal T1 domain (Q67, D75) and the C-terminal CTA domain (aa 740–853) modulate activation rate, and N-C terminal interactions are required for normal kinetics.","method":"GST fusion protein pulldown, chimeric channels between human and rat Kv2.1, two-electrode voltage-clamp in Xenopus oocytes","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct in vitro protein interaction plus chimeric mutagenesis with functional electrophysiology, single lab","pmids":["12560340"],"is_preprint":false},{"year":2006,"finding":"Voltage-gating of Kv2.1 induces relative rearrangements between N- and C-terminal domains: FRET between N- and C-terminal fluorescent tags on the same or different subunits decreased upon depolarization (+60 mV). N-terminal tags did not rearrange relative to each other. These movements occur in a plane parallel to the plasma membrane within 1–10 nm, and are distinct from movements relative to the membrane.","method":"FRET microscopy with N- and C-terminal CFP/YFP fusions, combined with patch-clamp (COS1 cells)","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — FRET-patch-clamp with multiple control constructs in same study, direct structural-functional link","pmids":["16690619"],"is_preprint":false},{"year":2008,"finding":"Kv2.1 forms a complex with focal adhesion kinase (FAK) through an LD-like motif in its N-terminus, promoting FAK phosphorylation at Y397 and Y576/577. FAK expression promotes polarized membrane distribution of Kv2.1. shRNA knockdown of Kv2.1 or N-terminal point mutations minimized FAK phosphorylation and impaired cell migration.","method":"Co-immunoprecipitation, shRNA knockdown, N-terminal point mutations, phosphospecific immunoblotting, migration assays","journal":"Journal of Cellular Physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus mutagenesis plus knockdown, single lab, functional migration readout","pmids":["18615577"],"is_preprint":false},{"year":2014,"finding":"De novo KCNB1 missense mutations causing epileptic encephalopathy result in loss of Kv2.1 ion selectivity and gain of a depolarizing inward cation conductance, as established by heterologous expression and functional electrophysiology in three patients.","method":"Whole exome sequencing, heterologous expression in mammalian cells, whole-cell patch-clamp","journal":"Annals of Neurology","confidence":"High","confidence_rationale":"Tier 2 / Strong — functional characterization of three independent patient mutations all showing the same loss-of-selectivity mechanism","pmids":["25164438"],"is_preprint":false},{"year":2015,"finding":"The KCNB1-V378A epileptic encephalopathy variant produces voltage-activated but non-selective Kv2.1 currents (loss of ion selectivity while retaining voltage sensitivity). Cell-type-dependent differences in expression and subcellular localization of V378A were observed, and co-expression of V378A and wild-type Kv2.1 reciprocally affected their trafficking.","method":"Heterologous expression, whole-cell patch-clamp, guangxitoxin-1E pharmacology, immunofluorescence","journal":"The Journal of General Physiology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — detailed electrophysiology plus subcellular localization plus co-expression trafficking assays in single study","pmids":["26503721"],"is_preprint":false},{"year":2015,"finding":"KCNB1-R306C (voltage sensor) disrupted voltage sensor sensitivity and cooperativity, while KCNB1-G401R (pore domain) selectively abolished endogenous Kv2 currents in transfected pyramidal neurons via dominant-negative action. Both mutants inhibited repetitive neuronal firing by preventing production of deep interspike voltages.","method":"Heterologous expression, whole-cell patch-clamp, endogenous Kv2 current measurement in pyramidal neurons, dominant-negative functional testing","journal":"Scientific Reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — mechanistic dissection of two distinct disease mutations with endogenous neuron recordings, single lab","pmids":["26477325"],"is_preprint":false},{"year":2009,"finding":"SUMO1 conjugation to Kv2.1 inhibits K+ current by ~80% (direct recombinant SUMO1 infusion) or ~48% (SUMO1-YFP co-expression) in HEK cells, and by ~49% in human beta-cells. The inhibitory effect results from acceleration of inactivation and inhibition of recovery from inactivation, widening beta-cell action potentials and decreasing firing frequency. Effects are augmented by Ubc9 and rescued by SENP1.","method":"Co-immunoprecipitation, direct intracellular SUMO1 peptide infusion, whole-cell patch-clamp in HEK and beta-cells, SUMO protease rescue","journal":"Journal of Cell Science","confidence":"High","confidence_rationale":"Tier 2 / Strong — co-IP plus direct peptide infusion plus enzyme-mediated rescue in native beta-cells, multiple orthogonal methods","pmids":["19223394"],"is_preprint":false},{"year":2011,"finding":"Incretin hormones GIP and GLP-1 promote phosphorylation and acetylation of Kv2.1 via PKA/MSK-1 and HAT/HDAC pathways in pancreatic beta-cells. Acetylation of Kv2.1 is mediated by nuclear/cytoplasmic shuttling of CREB binding protein (CBP) and its direct interaction with Kv2.1. These post-translational modifications of Kv2.1 underlie the prosurvival effects of incretins.","method":"Overexpression and pharmacological inhibition, phosphorylation/acetylation immunoblotting, CBP-Kv2.1 co-immunoprecipitation, nuclear shuttling assays","journal":"Cell Death and Differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus PTM assays plus pharmacological dissection, single lab, mechanistic pathway mapped","pmids":["21818121"],"is_preprint":false},{"year":2017,"finding":"Kv2.1 uses two distinct trafficking pathways to reach different subcellular compartments: the conventional Golgi-dependent secretory pathway for somatodendritic targeting, and a non-conventional Golgi-independent pathway for axon initial segment (AIS) targeting. A distinct AIS trafficking motif in the Kv2.1 C-terminus with putative phosphorylation sites is required for clustered AIS localization.","method":"FRAP, Golgi disruption pharmacology, mutagenesis of C-terminal AIS motif and phosphorylation sites, photoactivatable-GFP imaging in hippocampal neurons","journal":"The Journal of Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — FRAP plus pharmacological pathway dissection plus mutagenesis with spatial live imaging, multiple orthogonal approaches","pmids":["29042434"],"is_preprint":false},{"year":2009,"finding":"Conserved negatively charged aspartates (CDD motif) in the A/B linker of the T1 tetramerization domain are required for efficient assembly of both homotetrameric Kv2.1 and heterotetrameric Kv2.1/Kv6.4 channels. Charge-reversal arginine substitutions in Kv2.1 or Kv6.4 blocked tetramer assembly (FRET) without impairing trafficking to the membrane.","method":"FRET confocal microscopy, co-immunoprecipitation, immunocytochemistry, charge-reversal mutagenesis","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — FRET plus co-IP plus mutagenesis defining specific assembly determinant, multiple orthogonal methods","pmids":["19717558"],"is_preprint":false},{"year":2008,"finding":"Histidine 105 in the T1 domain of Kv2.1 is required for heteromerization with Kv6.3 and Kv6.4 but not for Kv2.1 homoassembly. H105V or H105R mutations disrupted T1-T1 interaction with Kv6.3/Kv6.4 (yeast two-hybrid), reduced FRET between Kv2.1 and Kv6.3/6.4, prevented co-immunoprecipitation, and abolished Kv6.3/6.4-mediated shifts in voltage dependence of Kv2.1 activation.","method":"Yeast two-hybrid, FRET confocal microscopy, co-immunoprecipitation, site-directed mutagenesis, whole-cell patch-clamp","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — three orthogonal binding assays (yeast two-hybrid, FRET, co-IP) plus functional electrophysiology, single rigorous study","pmids":["19074135"],"is_preprint":false},{"year":2012,"finding":"Oxidized KCNB1 channels form oligomers held by Cys-73 disulfide bridges and accumulate in the plasma membrane due to defective dynamin 2-dependent endocytosis. KCNB1 oligomers in lipid rafts disrupt raft integrity and activate c-Src/JNK signaling to promote apoptosis. C73A-mutant channels do not oligomerize and are normally internalized.","method":"Biochemical oligomerization assays, dynamin inhibition, cholesterol manipulation, c-Src/JNK inhibition (pharmacological and molecular), co-immunoprecipitation","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — mechanistic cascade from oxidation to oligomerization to endocytosis block to Src/JNK activation, multiple interventions and C73A control","pmids":["23275378"],"is_preprint":false},{"year":2017,"finding":"Oxidized KCNB1 channels form macromolecular complexes with integrin alpha-5 (integrin-α5). Upon KCNB1 oxidation, the integrin-FAK-Src/Fyn apoptotic signaling cascade is activated. C73A non-oxidizable mutant channels retained integrin-α5 interaction but did not activate FAK/Src/Fyn, demonstrating that the oxidized state specifically triggers integrin signaling.","method":"Co-immunoprecipitation from mouse brain, pharmacological integrin/FAK inhibition, C73A KCNB1 mutant, FAK/Src kinase activity assays","journal":"Cell Death & Disease","confidence":"High","confidence_rationale":"Tier 2 / Strong — native brain co-IP plus loss-of-function pharmacology plus non-oxidizable mutant control, mechanistic pathway established","pmids":["28383553"],"is_preprint":false},{"year":2020,"finding":"Kv2.1 mediates neuroprotection by maintaining ER-plasma membrane junctions through its interaction with VAPA. TAT-DP-2, a membrane-permeable peptide derived from Kv2.2 C-terminus, disrupts the Kv2.1-VAPA association, induces Kv2.1 declustering, prevents pro-apoptotic K+ current enhancement after injury, and reduces infarct size in murine ischemia-reperfusion, demonstrating that Kv2.1-VAPA interaction is required for post-injury channel clustering and cell death.","method":"TAT-peptide declustering, Kv2.1-VAPA co-immunoprecipitation, whole-cell patch-clamp, in vivo ischemia-reperfusion mouse model, infarct size measurement","journal":"Science Advances","confidence":"High","confidence_rationale":"Tier 2 / Strong — molecular disruption of specific protein-protein interaction confirmed biochemically plus in vitro and in vivo functional validation","pmids":["32937450"],"is_preprint":false},{"year":2022,"finding":"Kv2.1 (via its non-conducting structural role binding ER protein VAP/VAMP-associated protein) enables activity-dependent ER Ca2+ uptake in both soma and axons. Kv2.1 knockdown rendered the ER unable to accumulate Ca2+ during electrical activity and impaired synaptic vesicle fusion during stimulation, revealing an essential non-conducting role for Kv2.1 in maintaining ER Ca2+ homeostasis and synaptic transmission.","method":"Kv2.1 shRNA knockdown, live Ca2+ imaging in soma and axons, synaptic vesicle fusion assays, electrical stimulation protocols","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 2 / Strong — KD with specific phenotypic readouts in multiple compartments (soma and axon), mechanistic link to VAPA binding established","pmids":["35862456"],"is_preprint":false},{"year":2015,"finding":"In pancreatic beta-cells, Kv2.1 (but not Kv2.2) forms clusters of 6–12 tetrameric channels at the plasma membrane and facilitates insulin exocytosis by promoting secretory granule targeting. A truncated Kv2.1 (ΔC318) that retains electrical function and syntaxin 1A binding but cannot form clusters does not enhance granule recruitment or exocytosis, demonstrating that the structural clustering role—not K+ conductance—is required for exocytosis facilitation.","method":"Kv2.1 knockdown, Kv2.1-ΔC318 expression, TIRF microscopy of granule dynamics, whole-cell patch-clamp, T2D islet experiments","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 / Strong — clustering-deficient mutant dissociates electrical from structural function, plus T2D rescue experiment, multiple readouts","pmids":["28607108"],"is_preprint":false},{"year":2003,"finding":"MiRP2 (KCNE3) forms native complexes with Kv2.1 in rat brain (co-immunoprecipitation). MiRP2 reduces Kv2.1 current density and slows both activation and deactivation. Altering MiRP2 expression by RNAi or cDNA transfection toggles endogenous delayed-rectifier current magnitude and kinetics in PC12 cells and hippocampal neurons.","method":"Co-immunoprecipitation from rat brain, RNAi knockdown, cDNA overexpression, whole-cell patch-clamp in PC12 cells and hippocampal neurons","journal":"The Journal of Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — native brain co-IP plus gain and loss of function in endogenous system with functional readout","pmids":["12954870"],"is_preprint":false},{"year":2009,"finding":"MinK (KCNE1) and MiRP1 (KCNE2) form native cardiac complexes with Kv2.1 (co-immunoprecipitation from rat heart). Both reduce Kv2.1 current density and slow activation/deactivation. Disease-associated LQTS mutations in MinK and MiRP1 further alter Kv2.1 gating (D76N-MinK reduces current density 3-fold; I57T-MiRP1 slows activation 5-fold).","method":"Co-immunoprecipitation from rat heart, whole-cell patch-clamp in CHO cells with mutant subunit co-expression","journal":"The Journal of Membrane Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — native tissue co-IP plus heterologous functional characterization including disease variants, single lab","pmids":["19219384"],"is_preprint":false},{"year":2011,"finding":"Src kinase phosphorylates Kv2.1 at two novel tyrosine sites: Y686 (regulates channel activity, similar to Y124) and Y810 (regulates intracellular trafficking of Kv2.1 channels). Src also increases Kv2.1 protein expression levels.","method":"Mass spectrometry identification of phosphotyrosine sites, site-directed mutagenesis, whole-cell patch-clamp, Kv2.1 trafficking assays","journal":"Journal of Proteome Research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS identification plus mutagenesis plus functional assays, single lab","pmids":["22106938"],"is_preprint":false},{"year":2015,"finding":"During M-phase of the cell cycle, Kv2.1 undergoes increased phosphorylation at C-terminal sites and redistributes from diffuse to robust clusters at plasma membrane–ER membrane contact sites (PM:ER MCS) in COS-1 cells, inducing more extensive PM:ER MCS during mitosis. The same C-terminal targeting motif required for neuronal clustering is required for M-phase clustering.","method":"Phosphospecific immunoblotting, immunofluorescence, cell cycle synchronization, confocal microscopy in COS-1/CHO cells","journal":"The Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell cycle synchronization plus phosphorylation mapping plus localization, functional consequence of M-phase clustering not fully established","pmids":["26442584"],"is_preprint":false},{"year":2018,"finding":"BACE2 cleaves Kv2.1 at three sites (Thr376, Ala717, Ser769), disrupts Kv2.1 clustering, reduces delayed rectifier I_K, and causes a hyperpolarizing shift in activation in primary neurons. BACE2-cleaved Kv2.1 fragments (Kv2.1-1-375, -1-716, -1-768) each reduce apoptosis, suggesting BACE2-mediated cleavage is neuroprotective.","method":"In vitro cleavage assay identifying cleavage sites, immunofluorescence clustering analysis, whole-cell patch-clamp, apoptosis assays","journal":"Molecular Psychiatry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proteolytic site mapping plus functional channel readouts, single lab study","pmids":["29703946"],"is_preprint":false},{"year":2012,"finding":"Acute SDF-1α/CXCR4 signaling causes calcineurin-dependent dephosphorylation and altered localization of Kv2.1, enhancing voltage-dependent activation (neuroprotective). Prolonged SDF-1α/CXCR4 signaling activates p38 MAPK, which phosphorylates Kv2.1 at S800 and enhances surface trafficking, predisposing neurons to excessive K+ efflux and apoptosis. Kv2.1-S800A mutant prevented CXCR4-dependent apoptosis.","method":"Immunoblotting for Kv2.1 phosphorylation, S800A mutagenesis, whole-cell patch-clamp, immunofluorescence cluster analysis, CXCR4 pharmacological/genetic manipulation","journal":"The Journal of Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — specific phospho-site mutant (S800A) causally links CXCR4-p38 signaling to apoptotic Kv2.1 trafficking, multiple readouts","pmids":["23223293"],"is_preprint":false},{"year":2015,"finding":"PIP2 regulates Kv2.1 by modulating its inactivation mechanism: PIP2 prevents rundown and shifts voltage-dependence of inactivation in inside-out patches. PIP2 depletion accelerates closed-state inactivation and delays recovery from inactivation without affecting activation. Modeled by allosteric interaction of PIP2 with the inactivation gate.","method":"Excised inside-out patch clamp with exogenous PIP2, rapamycin-induced 5-phosphatase translocation (FKBP-Inp54p), M1 receptor activation","journal":"Scientific Reports","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — direct lipid application to excised patches plus orthogonal depletion strategies, single lab","pmids":["29379118"],"is_preprint":false},{"year":2015,"finding":"The pro-apoptotic dual phosphorylation of Kv2.1 at Y124 (by Src) and S800 (by p38) is co-regulated: intact Y124 is required for p38 phosphorylation of S800, and Src phosphorylation of Y124 facilitates p38 action at S800. Conversely, S800A mutation reduces Src action on Y124. Cys73 (but not Cys710) at the N-terminus is required for p38-dependent S800 phosphorylation and apoptotic K+ current enhancement.","method":"Immunoprecipitation with phosphospecific antibodies, site-directed mutagenesis of Y124, S800, C73, C710, whole-cell patch-clamp in CHO cells","journal":"PloS One","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phosphospecific antibodies plus multiple mutants, single lab, mechanistic co-regulation pathway established","pmids":["26115091"],"is_preprint":false},{"year":2022,"finding":"KCNB1 forms complexes with integrins α5β5 (integrin-K+ channel complexes, IKCs) in the neocortex. KCNB1 null mice show impaired neocortical neuronal migration, disrupted morphology and synaptic connectivity. Knock-in R312H mice (DEE variant) show the same developmental defects with impaired IKC biochemical signaling. Angiotensin II (FAK agonist) rescued R312H neuronal abnormalities in vitro, implicating non-conducting IKC signaling in cortical development.","method":"KCNB1 null and knock-in (R312H) mice, neuronal migration assays, co-immunoprecipitation (KCNB1-integrin), pharmacological FAK activation rescue","journal":"Cell Death and Differentiation","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic null plus knock-in plus co-IP of native complex plus pharmacological rescue, mechanistic non-conducting role established","pmids":["36207442"],"is_preprint":false},{"year":2020,"finding":"In arterial smooth muscle cells, Kv2.1 has a dual role: a canonical conductive role (less than 1% of channels are conductive and hyperpolarize the membrane) and a structural role in enhancing clustering and cooperative opening of CaV1.2 L-type Ca2+ channels. In female myocytes where Kv2.1 expression is higher, the structural role dominates, increasing CaV1.2 cluster size, Ca2+ influx, and myogenic tone. In male myocytes, Kv2.1 primarily controls membrane potential.","method":"Kv2.1 KO, electrophysiology, TIRF microscopy (CaV1.2 cluster imaging), sex-stratified analysis of Kv2.1 expression and function in myocytes","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO plus structural imaging plus functional electrophysiology, sex-stratified mechanistic dissection with multiple orthogonal approaches","pmids":["32015129"],"is_preprint":false},{"year":2015,"finding":"Leptin increases Kv2.1 surface expression in beta-cells via AMPK activation (requiring CaMKKβ) and PKA. The increased Kv2.1 surface expression depends on actin depolymerization. This trafficking regulation mirrors leptin's concurrent trafficking regulation of KATP channels, coordinately inhibiting insulin secretion by hyperpolarizing membrane potential (via KATP) and accelerating repolarization (via Kv2.1).","method":"Surface biotinylation, AMPK/PKA pharmacological and genetic manipulation, actin disruption, whole-cell patch-clamp in rodent and human beta-cells","journal":"The Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — surface expression quantification plus pathway inhibition experiments, functional readout in native beta-cells","pmids":["26453299"],"is_preprint":false},{"year":2020,"finding":"Kv2.1-G379R (DEE variant) does not induce ER-plasma membrane junction formation in HEK293T cells, and co-expression of G379R with wild-type Kv2.1 reduces EPJ induction relative to WT alone, consistent with dominant-negative disruption of the structural (non-conducting) function of Kv2.1.","method":"HEK293T cell expression, immunofluorescence of ER-PM junctions, co-expression dominant-negative assessment","journal":"Neurobiology of Disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — heterologous expression with clear structural readout, single lab, establishes non-conducting function impairment","pmids":["33132203"],"is_preprint":false},{"year":2004,"finding":"NFATc3 is an obligatory component of the signaling cascade mediating Ang II-induced reduction of Kv2.1 expression in arterial smooth muscle. Sustained Ang II increases smooth muscle Ca2+ via L-type channels, activates calcineurin and NFATc3, and decreases Kv2.1 K+ channel subunit expression and Kv current.","method":"Dominant-negative NFATc3, calcineurin inhibition, pharmacological L-type Ca2+ channel block, immunoblotting, patch-clamp in arterial smooth muscle","journal":"The Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — dominant-negative transcription factor plus pathway inhibition with functional current readout, single lab","pmids":["15322114"],"is_preprint":false},{"year":2006,"finding":"N-terminal SNAP-25 domains (residues 1–197 and 1–180), acting on the Kv2.1 cytoplasmic N-terminus, increased Kv2.1 activation rate, slowed inactivation, and potentiated external TEA block by restructuring the outer pore architecture. Full-length SNAP-25 and C-terminal domains had no such effect, demonstrating domain-specific regulation.","method":"Intracellular dialysis of SNAP-25 domain peptides, whole-cell patch-clamp, external TEA block analysis, ionic substitution experiments","journal":"The Biochemical Journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain peptide dialysis with functional electrophysiology showing pore architecture changes, single lab","pmids":["16478442"],"is_preprint":false},{"year":2014,"finding":"Somatic Kv2.1 clusters in striatal medium spiny neurons (MSNs) are juxtaposed to ryanodine receptor (RyR) Ca2+-release channel clusters at subsurface cisternae. Acute RyR stimulation in heterologous cells caused a rapid hyperpolarizing shift in Kv2.1 voltage-dependent activation consistent with Ca2+/calcineurin-dependent dephosphorylation. MSNs in direct and indirect pathways differ in Kv2.1 phosphorylation state at multiple sites.","method":"Electron microscopy-immunogold labeling, immunofluorescence in transgenic GFP-MSN mice, phosphospecific antibody immunolabeling, RyR agonist treatment in heterologous cells, patch-clamp","journal":"The Journal of Comparative Neurology","confidence":"High","confidence_rationale":"Tier 2 / Strong — EM-immunogold plus functional RyR-Kv2.1 coupling in cells plus cell-type-specific phosphorylation profiling, multiple methods","pmids":["24962901"],"is_preprint":false}],"current_model":"Kv2.1 (KCNB1) is a voltage-gated delayed-rectifier K+ channel that (1) conducts K+ primarily as a nonclustered minority of surface channels, with its gating graded by multisite phosphorylation (by CDK5, AMPK, Src, p38) and dephosphorylation (by calcineurin), SUMOylation, and accessory subunits (AMIGO, MiRP2, MinK, silent Kv5/6/8/9 subunits); (2) forms large ER–plasma membrane junction-inducing clusters at the neuronal soma/proximal dendrites and AIS via a C-terminal domain-dependent, actin-gated, phosphorylation-regulated mechanism that is mechanistically distinct from its conducting role; (3) serves a non-conducting structural function at these junctions—scaffolding LTCC-RyR Ca2+ signaling triads, enabling activity-dependent ER Ca2+ uptake, facilitating SNARE-dependent synaptic vesicle fusion, and promoting insulin exocytosis in beta-cells through secretory granule recruitment; and (4) mediates neuronal apoptosis via a Zn2+/CaMKII/SNARE-dependent plasma membrane insertion program (requiring coordinated Src-Y124 and p38-S800 phosphorylation and integrin-FAK signaling), while oxidative modification at Cys73 drives oligomerization, defective endocytosis, and pro-apoptotic c-Src/JNK activation through disruption of lipid raft integrity."},"narrative":{"mechanistic_narrative":"KCNB1 encodes Kv2.1, a voltage-gated delayed-rectifier K+ channel whose biology is split between a canonical conducting role in membrane repolarization and a non-conducting structural role organizing ER–plasma membrane junctions [PMID:20566856, PMID:25908859]. As a channel, Kv2.1 assembles as a tetramer through T1-domain determinants (a CDD motif and His105) that also govern heteromerization with silent regulatory subunits such as Kv5.1 and Kv6.1, which reshape its gating [PMID:19717558, PMID:19074135, PMID:9696692, PMID:8980147], and it is decorated by accessory subunits AMIGO, MiRP2/KCNE3, and MinK/MiRP1 that tune current density and kinetics [PMID:22056818, PMID:12954870, PMID:19219384]. Its voltage dependence is graded by an unusually rich array of reversible modifications: multisite C-terminal serine phosphorylation by CDK5 and AMPK opposed by calcineurin-mediated dephosphorylation [PMID:16917065, PMID:9351973, PMID:22006306, PMID:21712386], Src-mediated tyrosine phosphorylation [PMID:12615930], SUMOylation at K470 [PMID:21518833, PMID:19223394], and PIP2 binding [PMID:29379118], so that activity-dependent signals (e.g. extrasynaptic NMDA receptor activation) reset neuronal excitability through cluster dispersal and dephosphorylation [PMID:18753382]. Strikingly, only ~2% of surface channels conduct, while clustered channels are largely electrically silent and instead tether cortical ER to the plasma membrane via the VAP-family protein VAPA, an interaction directed by an autonomous, actin-gated C-terminal targeting module [PMID:8978827, PMID:20566856, PMID:25908859, PMID:16988031, PMID:32937450]. These non-conducting junctions scaffold Ca2+ signaling triads coupling L-type Ca2+ channels to ryanodine receptors, support activity-dependent ER Ca2+ uptake and synaptic vesicle fusion, organize membrane-protein trafficking platforms, and drive insulin granule recruitment in beta-cells—functions that survive in clustering-competent but conduction-independent constructs [PMID:31663850, PMID:35862456, PMID:22648171, PMID:28607108, PMID:24962901]. In pancreatic beta-cells Kv2.1 dominates action-potential repolarization and restrains glucose-stimulated insulin secretion, and is itself regulated by SNARE proteins, lipid rafts, and incretin/leptin signaling [PMID:12270920, PMID:12403834, PMID:15073181, PMID:26453299]. Kv2.1 also executes a pro-apoptotic program in which oxidant- or injury-triggered Zn2+/CaMKII signaling drives SNARE-dependent insertion of channels and a surge of K+ efflux, gated by coordinated Src-Y124 and p38-S800 phosphorylation and Cys73-dependent oxidative oligomerization that activates integrin-FAK and c-Src/JNK signaling [PMID:12832499, PMID:23918396, PMID:23275378, PMID:28383553, PMID:23223293, PMID:26115091]. Beyond neurons it organizes integrin α5β5 \"integrin-K+ channel complexes\" required for neocortical neuronal migration and connectivity, and contributes a sex-dependent structural role in arterial smooth muscle by clustering CaV1.2 [PMID:36207442, PMID:32015129]. De novo KCNB1 missense mutations cause epileptic encephalopathy, acting through loss of ion selectivity with a gained inward cation conductance, dominant-negative suppression of endogenous Kv2 current, or disruption of the non-conducting ER–PM junction–inducing and integrin-signaling functions [PMID:25164438, PMID:26503721, PMID:26477325, PMID:33132203, PMID:36207442].","teleology":[{"year":1995,"claim":"Established a high-affinity pharmacological probe and showed Kv2.1's toxin sensitivity maps outside the canonical scorpion-toxin pore region, defining a distinct gating-modifier interaction surface.","evidence":"Tarantula hanatoxin isolation and voltage-clamp kinetics across channel families","pmids":["7576642"],"confidence":"High","gaps":["Structural basis of the hanatoxin binding site not resolved","Does not address physiological regulation"]},{"year":1997,"claim":"Localized the gating-modulatory phosphorylation to the C-terminal cytoplasmic domain, establishing that reversible C-terminal serine phosphorylation directly sets Kv2.1 voltage dependence.","evidence":"C-terminal truncation, 32P labeling, and patch-clamp with intracellular phosphatase rescue","pmids":["9351973"],"confidence":"High","gaps":["Specific kinases and sites not yet identified","Number of functional phospho-sites unknown"]},{"year":1996,"claim":"Defined an autonomous C-terminal cytoplasmic domain necessary and sufficient for high-density clustering and polarized targeting, the first hint that localization is genetically separable from channel function.","evidence":"Truncation and chimeric constructs in polarized MDCK cells with detergent-solubility analysis","pmids":["8978827"],"confidence":"High","gaps":["Molecular tether mediating clustering not identified","Link between detergent insolubility and cytoskeleton not directly shown"]},{"year":1996,"claim":"Showed Kv2.1 coassembles with silent Kv6 subunits to generate heteromeric channels with novel gating, expanding the functional repertoire of Kv2.1-containing channels.","evidence":"Two-electrode voltage-clamp and yeast two-hybrid of N-terminal interactions (Kv6.1; extended to Kv5.1/Kv6.1)","pmids":["8980147","9696692"],"confidence":"High","gaps":["Stoichiometry of heteromers in vivo unknown","Physiological contexts of silent-subunit modulation not defined"]},{"year":2003,"claim":"Demonstrated Kv2.1 is the dominant beta-cell delayed rectifier restraining insulin secretion, defining a non-neuronal physiological role in glucose homeostasis.","evidence":"Dominant-negative knockout, selective antagonist, Ca2+ imaging, and islet perfusion","pmids":["12270920"],"confidence":"High","gaps":["Did not yet distinguish conducting vs structural contributions to secretion","In vivo whole-animal phenotype not addressed"]},{"year":2003,"claim":"Identified Kv2.1 as necessary and sufficient for the apoptotic K+ efflux in neurons, linking the channel to programmed cell death.","evidence":"Dominant-negative expression and reconstitution in channel-null CHO cells with multiple apoptogens","pmids":["12832499"],"confidence":"High","gaps":["Mechanism of the apoptotic current surge not defined","Signaling triggers upstream unknown"]},{"year":2003,"claim":"Mapped early protein interactions and modifications governing channel function: SNAP-25 binding to the N-terminus, Src phosphorylation of T1-domain Y124, and direct N–C terminal interaction controlling kinetics.","evidence":"Co-IP, in vitro kinase/substrate-trapping, GST pulldown, and electrophysiology","pmids":["12403834","12615930","12560340"],"confidence":"High","gaps":["Whether these interactions cooperate was not established","In vivo relevance of Y124 phosphorylation not tested"]},{"year":2006,"claim":"Established graded, multisite phosphorylation as the logic of Kv2.1 regulation and showed the C-terminal domain is a transferable module conferring clustering, gating, and cholinergic/calcineurin modulation.","evidence":"MS-SILAC site mapping with additive mutagenesis; domain-swap chimeras with biochemical and electrophysiological readouts; FRET reporting N–C domain rearrangement on gating","pmids":["16917065","16407566","16690619"],"confidence":"High","gaps":["Individual kinases for most sites not yet assigned","Structural model of clustering still absent"]},{"year":2006,"claim":"Revealed cortical actin as a perimeter fence retaining mobile channels within clusters and restricting somatic localization, providing the cytoskeletal basis for cluster organization.","evidence":"FRAP, quantum-dot tracking, and latrunculin A disruption in HEK cells and neurons","pmids":["16988031"],"confidence":"High","gaps":["Molecular link between C-terminus and actin not defined","How clusters nucleate not addressed"]},{"year":2008,"claim":"Connected physiological signaling to Kv2.1 regulation by showing extrasynaptic NMDA receptor activation specifically declusters and dephosphorylates the channel, and linked Kv2.1 to integrin/FAK signaling via an N-terminal LD-like motif.","evidence":"Pharmacological synaptic/extrasynaptic dissection with biochemical and electrophysiological readouts; co-IP, knockdown, and migration assays","pmids":["18753382","18615577"],"confidence":"High","gaps":["FAK interaction confidence is Medium and single-lab","Physiological trigger linking glutamate to FAK not unified"]},{"year":2009,"claim":"Defined T1-domain assembly determinants (CDD motif) and demonstrated SUMOylation as a reversible inhibitory modification of beta-cell and neuronal Kv2.1 current.","evidence":"FRET/co-IP charge-reversal mutagenesis; SUMO1 infusion with SENP1 rescue in HEK and human beta-cells; NFATc3-dependent transcriptional downregulation in smooth muscle; MinK/MiRP1 cardiac complexes","pmids":["19717558","19223394","15322114","19219384"],"confidence":"High","gaps":["Coordination between SUMO and phospho-regulation not resolved","Cardiac role of Kv2.1 physiologically uncertain (Medium evidence)"]},{"year":2010,"claim":"Overturned the assumption that clusters are conducting reservoirs by showing only ~2% of surface channels conduct and declustering does not unmask current, separating Kv2.1's conducting and clustering roles.","evidence":"Spatially resolved cell-attached single-channel recording with FRAP, phosphatase, and actin perturbation","pmids":["20566856"],"confidence":"High","gaps":["Function of the non-conducting cluster pool not yet known at this point","Why most channels are silent unexplained"]},{"year":2011,"claim":"Assigned specific kinases to the graded regulation: CDK5 sets the constitutive high-phosphorylation state, AMPK phosphorylates S440 to hyperpolarize gating and reduce firing, and SUMOylation occurs at K470 with single-subunit graded effects.","evidence":"In vitro kinase assays, phosphospecific antibodies, MS, mutagenesis, and single-channel recordings in neurons","pmids":["21712386","22006306","21518833","22056818"],"confidence":"High","gaps":["Integration of multiple kinase inputs in vivo not modeled","Upstream activation of CDK5/AMPK pools on Kv2.1 unclear"]},{"year":2012,"claim":"Demonstrated clusters function as exocytic insertion platforms for membrane proteins and that oxidative Cys73 oligomerization blocks endocytosis to drive raft disruption and c-Src/JNK pro-apoptotic signaling.","evidence":"TIRF-FRAP and quantum-dot trafficking imaging; biochemical oligomerization, dynamin/cholesterol manipulation, and kinase inhibition with C73A control","pmids":["22648171","23275378"],"confidence":"High","gaps":["Identity of the oxidant sensor coupling to Cys73 in vivo not defined","How clusters template exocytosis mechanistically unresolved"]},{"year":2013,"claim":"Defined the apoptotic insertion cascade: oxidant-evoked Ca2+/CaMKII modulates the syntaxin–Kv2.1 interaction to drive SNARE-dependent surface insertion and the lethal K+ surge.","evidence":"CaMKII inhibition, Ca2+ imaging, syntaxin co-IP, electrophysiology, and viability assays","pmids":["23918396"],"confidence":"High","gaps":["SNARE machinery components beyond syntaxin not fully mapped","Link to physiological injury triggers indirect"]},{"year":2014,"claim":"First identified KCNB1 as a human disease gene, with de novo missense mutations causing epileptic encephalopathy through loss of ion selectivity and a gained depolarizing cation conductance, and localized Kv2.1 clusters adjacent to RyR cisternae in striatal neurons.","evidence":"Exome sequencing with heterologous functional electrophysiology; EM-immunogold and phosphospecific labeling in MSNs","pmids":["25164438","24962901"],"confidence":"High","gaps":["Whether conducting or non-conducting defects dominate disease not resolved","In vivo neuronal consequences of mutations not yet tested"]},{"year":2015,"claim":"Resolved distinct disease mechanisms (loss of selectivity, voltage-sensor disruption, dominant-negative pore mutations), defined dual Golgi-dependent/independent trafficking to soma vs AIS, and showed the clustering role—not conductance—drives beta-cell granule recruitment.","evidence":"Heterologous and endogenous-neuron electrophysiology of patient variants; FRAP with Golgi-pathway dissection; clustering-deficient ΔC318 mutant with TIRF granule imaging","pmids":["26503721","26477325","29042434","28607108","26442584","29379118"],"confidence":"High","gaps":["AIS trafficking motif's binding partners unknown","Functional significance of M-phase clustering (Medium) not established"]},{"year":2015,"claim":"Established that pro-apoptotic Y124 and S800 phosphorylation are co-dependent and that beta-cell incretin/leptin and CXCR4 signaling route through Kv2.1 modification to set survival vs death outcomes.","evidence":"Phosphospecific co-IP and combinatorial mutagenesis (Y124/S800/C73); incretin PKA/MSK-1/CBP and leptin AMPK/PKA pathway dissection; CXCR4-p38-S800A causal mutant","pmids":["26115091","21818121","26453299","23223293"],"confidence":"High","gaps":["Several pathway steps are Medium-confidence single-lab","Spatial coordination of Src and p38 on the channel not visualized"]},{"year":2019,"claim":"Showed clustered Kv2.1 builds ER–PM junctions that scaffold LTCC–RyR Ca2+ triads and unexpectedly enhance LTCC opening at polarized potentials, defining a non-conducting Ca2+-signaling organizer role.","evidence":"BioID proximity proteomics, co-localization, Ca2+ spark imaging, LTCC single-channel recording, and Kv2.1 KO/KD","pmids":["31663850"],"confidence":"High","gaps":["Mechanism by which clusters enhance LTCC opening unresolved","Direct vs indirect Kv2.1–LTCC contacts not defined"]},{"year":2020,"claim":"Identified VAPA as the ER tether mediating Kv2.1-dependent junctions, showed a peptide disrupting Kv2.1–VAPA is neuroprotective in ischemia, and dissected a sex-dependent structural Kv2.1 role clustering CaV1.2 in arterial myocytes; a DEE variant fails to induce junctions dominant-negatively.","evidence":"TAT-peptide disruption with co-IP and in vivo ischemia-reperfusion; KO with TIRF CaV1.2 imaging and sex stratification; HEK ER-PM junction assay of G379R","pmids":["32937450","32015129","33132203"],"confidence":"High","gaps":["G379R junction defect is Medium-confidence heterologous only","Whether VAPA is the sole ER tether across cell types unknown"]},{"year":2022,"claim":"Cemented the essential non-conducting roles: VAP-dependent Kv2.1 enables activity-dependent ER Ca2+ uptake and synaptic vesicle fusion, and KCNB1 forms integrin α5β5 complexes required for neocortical migration, with a DEE knock-in mouse rescued by FAK activation.","evidence":"shRNA knockdown with compartmental Ca2+ and SV-fusion imaging; KCNB1 null and R312H knock-in mice with co-IP and angiotensin-II FAK rescue","pmids":["35862456","36207442"],"confidence":"High","gaps":["How integrin-FAK signaling drives migration mechanistically incomplete","Relative contribution of conducting vs structural roles to brain development not quantified"]},{"year":null,"claim":"How the dozens of phosphorylation, SUMOylation, oxidation, and lipid inputs are integrated in space and time to switch Kv2.1 between conducting, junction-organizing, and pro-apoptotic states remains unresolved, as does a unified structural model of the cluster and its ER tether.","evidence":"","pmids":[],"confidence":"High","gaps":["No high-resolution structure of the clustered channel–VAPA junction","Quantitative model integrating multisite modifications absent","Causal hierarchy of conducting vs structural deficits in human disease unsettled"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,6,27,29]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,4,6]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[7,16,38,39]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[7,37,48]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[5,6,14,18]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[7,37,38]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[5,14,15]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,8,21]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[2,22,35,36]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[27,28,29,48,51]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[48]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[16,45,52]}],"complexes":["Kv2.1 homotetramer / Kv2.1-Kv6.1 heterotetramer","Kv2.1-VAPA ER-PM junction complex","integrin α5β5-K+ channel complex (IKC)","Kv2.1-LTCC-RyR Ca2+ signaling triad"],"partners":["VAPA","SNAP25","STX1A","AMIGO1","KCNE3","KCNG1","ITGA5","PTK2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q14721","full_name":"Potassium voltage-gated channel subfamily B member 1","aliases":["Delayed rectifier potassium channel 1","DRK1","h-DRK1","Voltage-gated potassium channel subunit Kv2.1"],"length_aa":858,"mass_kda":95.9,"function":"Voltage-gated potassium channel that mediates transmembrane potassium transport in excitable membranes, primarily in the brain, but also in the pancreas and cardiovascular system. Contributes to the regulation of the action potential (AP) repolarization, duration and frequency of repetitive AP firing in neurons, muscle cells and endocrine cells and plays a role in homeostatic attenuation of electrical excitability throughout the brain (PubMed:23161216). Plays also a role in the regulation of exocytosis independently of its electrical function (By similarity). 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. Homotetrameric channels mediate a delayed-rectifier voltage-dependent outward potassium current that display rapid activation and slow inactivation in response to membrane depolarization (PubMed:10484328, PubMed:12560340, PubMed:1283219, PubMed:19074135, PubMed:19717558, PubMed:24901643, PubMed:8081723). Can form functional homotetrameric and heterotetrameric channels that contain variable proportions of KCNB2; channel properties depend on the type of alpha subunits that are part of the channel (By similarity). Can also form functional heterotetrameric channels with other alpha subunits that are non-conducting when expressed alone, such as KCNF1, KCNG1, KCNG3, KCNG4, KCNH1, KCNH2, KCNS1, KCNS2, KCNS3 and KCNV1, creating a functionally diverse range of channel complexes (PubMed:10484328, PubMed:11852086, PubMed:12060745, PubMed:19074135, PubMed:19717558, PubMed:24901643). Heterotetrameric channel activity formed with KCNS3 show increased current amplitude with the threshold for action potential activation shifted towards more negative values in hypoxic-treated pulmonary artery smooth muscle cells (By similarity). Channel properties are also modulated by cytoplasmic ancillary beta subunits such as AMIGO1, KCNE1, KCNE2 and KCNE3, slowing activation and inactivation rate of the delayed rectifier potassium channels (By similarity). In vivo, membranes probably contain a mixture of heteromeric potassium channel complexes, making it difficult to assign currents observed in intact tissues to any particular potassium channel family member. Major contributor to the slowly inactivating delayed-rectifier voltage-gated potassium current in neurons of the central nervous system, sympathetic ganglion neurons, neuroendocrine cells, pancreatic beta cells, cardiomyocytes and smooth muscle cells. Mediates the major part of the somatodendritic delayed-rectifier potassium current in hippocampal and cortical pyramidal neurons and sympathetic superior cervical ganglion (CGC) neurons that acts to slow down periods of firing, especially during high frequency stimulation. Plays a role in the induction of long-term potentiation (LTP) of neuron excitability in the CA3 layer of the hippocampus (By similarity). Contributes to the regulation of glucose-induced action potential amplitude and duration in pancreatic beta cells, hence limiting calcium influx and insulin secretion (PubMed:23161216). Plays a role in the regulation of resting membrane potential and contraction in hypoxia-treated pulmonary artery smooth muscle cells. May contribute to the regulation of the duration of both the action potential of cardiomyocytes and the heart ventricular repolarization QT interval. Contributes to the pronounced pro-apoptotic potassium current surge during neuronal apoptotic cell death in response to oxidative injury. May confer neuroprotection in response to hypoxia/ischemic insults by suppressing pyramidal neurons hyperexcitability in hippocampal and cortical regions (By similarity). Promotes trafficking of KCNG3, KCNH1 and KCNH2 to the cell surface membrane, presumably by forming heterotetrameric channels with these subunits (PubMed:12060745). Plays a role in the calcium-dependent recruitment and release of fusion-competent vesicles from the soma of neurons, neuroendocrine and glucose-induced pancreatic beta cells by binding key components of the fusion machinery in a pore-independent manner (By similarity)","subcellular_location":"Cell membrane; Perikaryon; Cell projection, axon; Cell projection, dendrite; Membrane; Postsynaptic cell membrane; Synapse; Synapse, synaptosome; Lateral cell membrane; Cell membrane, sarcolemma","url":"https://www.uniprot.org/uniprotkb/Q14721/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KCNB1","classification":"Not 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KCNS2","url":"https://www.omim.org/entry/602906"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"retina","ntpm":106.5}],"url":"https://www.proteinatlas.org/search/KCNB1"},"hgnc":{"alias_symbol":["Kv2.1"],"prev_symbol":[]},"alphafold":{"accession":"Q14721","domains":[{"cath_id":"3.30.710.10","chopping":"19-156","consensus_level":"medium","plddt":90.284,"start":19,"end":156},{"cath_id":"1.20.120.350","chopping":"161-313","consensus_level":"high","plddt":86.1401,"start":161,"end":313},{"cath_id":"1.10.287.70","chopping":"322-438","consensus_level":"high","plddt":91.4991,"start":322,"end":438}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q14721","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q14721-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q14721-F1-predicted_aligned_error_v6.png","plddt_mean":61.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KCNB1","jax_strain_url":"https://www.jax.org/strain/search?query=KCNB1"},"sequence":{"accession":"Q14721","fasta_url":"https://rest.uniprot.org/uniprotkb/Q14721.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q14721/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q14721"}},"corpus_meta":[{"pmid":"16917065","id":"PMC_16917065","title":"Graded 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Mutation of individual calcineurin-regulated sites to alanine produced incremental hyperpolarizing shifts in voltage-dependent activation, while aspartate mutations conferred resistance to calcineurin. Multiple site mutations were additive, demonstrating that variable phosphorylation at many sites allows graded, activity-dependent regulation of Kv2.1 gating and neuronal firing.\",\n      \"method\": \"Mass spectrometry-SILAC, site-directed mutagenesis, whole-cell patch-clamp\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal methods (MS-SILAC, mutagenesis, electrophysiology) in a single rigorous study with graded functional validation\",\n      \"pmids\": [\"16917065\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Hanatoxin (HaTx1/2) from Chilean tarantula venom inhibits Kv2.1 channels with Kd ~42 nM via a bimolecular reaction. The toxin binding site is distinct from the scorpion toxin site (S5-S6 linker), as regions outside this linker determine HaTx sensitivity. Shaker-, Shaw-, and eag-family channels are relatively insensitive, while Shal-related channels are sensitive.\",\n      \"method\": \"Peptide isolation, bacterial expression, voltage-clamp electrophysiology, kinetic analysis\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with synthetic toxin plus rigorous kinetic characterization, replicated in multiple channel types\",\n      \"pmids\": [\"7576642\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Kv2.1-encoded K+ channels are necessary and sufficient for the apoptotic K+ efflux in cortical neurons. Dominant-negative Kv2.1 expression eliminated the enhancement of K+ currents accompanying apoptosis and protected neurons from oxidant- and staurosporine-induced death. CHO cells (lacking endogenous voltage-gated K+ channels) became more susceptible to apoptosis after Kv2.1 transfection.\",\n      \"method\": \"Dominant-negative expression, whole-cell patch-clamp, cell viability assays\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean dominant-negative KO with defined phenotypic readout, replicated in two cell types with multiple apoptogenic stimuli\",\n      \"pmids\": [\"12832499\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Kv2.1 is the dominant voltage-dependent K+ channel in pancreatic beta-cells, responsible for action potential repolarization. Dominant-negative knockout of Kv2.1 enhanced glucose-stimulated insulin secretion. A selective Kv2.1 antagonist (C-1) blocked Kv2.1-mediated currents, enhanced membrane depolarization and Ca2+ responses to glucose, and augmented first- and second-phase insulin secretion from perfused pancreas.\",\n      \"method\": \"Dominant-negative expression, whole-cell patch-clamp, intracellular Ca2+ imaging, isolated islet perfusion\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — dominant-negative KO plus pharmacological inhibition with multiple orthogonal readouts across multiple preparations\",\n      \"pmids\": [\"12270920\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Phosphorylation of the Kv2.1 C-terminal cytoplasmic domain (residues 667–853) shifts voltage-dependent activation to more depolarized potentials. Intracellular alkaline phosphatase eliminated differences in voltage dependence between wild-type and C-terminal truncation mutants, demonstrating that C-terminal phosphorylation directly modulates Kv2.1 gating. Phosphorylation was restricted to serine residues.\",\n      \"method\": \"Truncation mutagenesis, 32P in vivo labeling, phosphoamino acid analysis, whole-cell patch-clamp with intracellular alkaline phosphatase\",\n      \"journal\": \"Molecular Pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — combined biochemical phosphorylation mapping and electrophysiological dephosphorylation rescue, multiple mutants tested\",\n      \"pmids\": [\"9351973\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"A cytoplasmic domain of Kv2.1 (amino acids 536–666 in the C-terminus) is necessary and sufficient for polarized lateral membrane targeting and high-density cluster formation. This domain also correlates with detergent insolubility, suggesting interaction with the detergent-insoluble cytoskeleton underlies proper localization.\",\n      \"method\": \"C-terminal truncation mutants expressed in MDCK cells, chimeric HA-Kv2.1 constructs, immunofluorescence, detergent solubility assay\",\n      \"journal\": \"The Journal of Cell Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — domain-swap chimera plus truncation series with clear localization phenotype in polarized cells\",\n      \"pmids\": [\"8978827\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Clustered Kv2.1 channels do not efficiently conduct K+; nonclustered channels carry the high-threshold delayed-rectifier current. Only ~2% of surface channels conduct. Dephosphorylation (alkaline phosphatase) caused a 25 mV hyperpolarizing shift without increasing whole-cell current, while actin depolymerization-induced declustering did not alter activation midpoint. Thus clusters do not contain a reservoir of non-conducting channels released upon declustering.\",\n      \"method\": \"Cell-attached patch clamp at defined surface locations (clustered vs. non-clustered), FRAP, alkaline phosphatase treatment, actin depolymerization\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cell-attached single-channel recordings with spatial resolution, multiple orthogonal perturbations in same study\",\n      \"pmids\": [\"20566856\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Kv2.1 clustering directly induces stable endoplasmic reticulum–plasma membrane junctions (EPJs). Using TIRF and electron microscopy, clustered Kv2.1 was shown to tether cortical ER to the plasma membrane in HEK 293 cells and hippocampal neurons. These non-conducting clusters serve as membrane-trafficking hubs for delivery and retrieval of multiple membrane proteins. Glutamate exposure causes loss of Kv2.1 clusters and retraction of cortical ER from the plasma membrane.\",\n      \"method\": \"TIRF microscopy, electron microscopy, live imaging, glutamate treatment\",\n      \"journal\": \"Journal of Cell Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — two orthogonal imaging modalities (TIRF + EM) with functional consequence (ER retraction upon glutamate), in two cell systems\",\n      \"pmids\": [\"25908859\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"AMPK directly phosphorylates Kv2.1 at S440 and S537. Phosphorylation at S440 (but not S537) mediates hyperpolarizing shifts in voltage-dependent activation and inactivation. In cultured rat hippocampal neurons, AMPK activation reduced neuronal firing frequency. Effects were abolished by S440A substitution, confirmed by phosphospecific antibodies and quantitative mass spectrometry.\",\n      \"method\": \"In vitro kinase assay, phosphospecific antibodies, quantitative mass spectrometry, site-directed mutagenesis, whole-cell patch-clamp, intracellular dialysis with thiophosphorylated AMPK\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct kinase assay plus mutagenesis plus in-cell confirmation with phosphospecific antibodies and MS, replicated in neurons\",\n      \"pmids\": [\"22006306\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"SUMO1 is conjugated to Kv2.1 at lysine K470 on the neuronal cell surface, shifting the half-maximal activation voltage (V1/2) by up to 35 mV. Only K470 is sumoylated; no more than two non-adjacent subunits in the tetramer carry SUMO concurrently. One SUMO shifts V1/2 by 15 mV; two SUMOs produce the full response, demonstrating graded regulation of neuronal excitability.\",\n      \"method\": \"SUMO conjugation assays, K470 mutagenesis, single-channel recordings, immunostaining of native SUMO and Kv2.1 in hippocampal neurons\",\n      \"journal\": \"The Journal of General Physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — site-specific mutagenesis identifying single SUMO acceptor plus single-channel electrophysiology with graded response quantification\",\n      \"pmids\": [\"21518833\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"CDK5 directly phosphorylates Kv2.1 and determines the constitutive high phosphorylation state of the channel in neurons. CDK5 also controls the rapid increase in Kv2.1 phosphorylation upon activity blockade and the recovery of phosphorylation after stimulus-induced dephosphorylation. CDK5 regulation of Kv2.1 is independent of CDK5's previously described regulation of PP1.\",\n      \"method\": \"In vitro kinase assay, CDK5 inhibition (pharmacological and genetic), phosphospecific antibody immunoblotting in hippocampal neurons\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct in vitro phosphorylation plus in-neuron phosphorylation state readouts, single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"21712386\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The Kv2.1 cytoplasmic C-terminal domain is an autonomous transferable module sufficient to confer Kv2.1-like phosphorylation-dependent clustering, voltage-dependent activation, and muscarinic (cholinergic) modulation to heterologous Kv channels. Cholinergic stimulation triggers Ca2+/calcineurin-dependent dephosphorylation of Kv2.1, dispersal of clusters, and hyperpolarizing shifts in gating.\",\n      \"method\": \"Chimeric Kv channel constructs, immunocytochemistry, biochemical phosphorylation assays, patch-clamp in HEK293 cells and hippocampal neurons\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — domain-swap chimeras with comprehensive biochemical, cell biological, and electrophysiological validation\",\n      \"pmids\": [\"16407566\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Kv5.1 and Kv6.1 are regulatory (silent) alpha-subunits that coassemble with Kv2.1 into heterotetrameric channels with altered gating. Kv2.1/Kv5.1 selectively accelerated inactivation at intermediate potentials and cumulative inactivation, and slowed deactivation. Kv2.1/Kv6.1 shifted activation to negative potentials and markedly slowed deactivation. Heteromeric assembly was confirmed by co-immunoprecipitation and single-channel conductance heterogeneity.\",\n      \"method\": \"Two-electrode voltage-clamp in Xenopus oocytes, co-immunoprecipitation, single-channel recordings\",\n      \"journal\": \"The American Journal of Physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal biochemical pulldown plus single-channel recordings plus gating analysis, replicated across two silent subunits\",\n      \"pmids\": [\"9696692\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Kv6.1 and Kv2.1 form heterotetrameric channels with a novel current distinct from homomeric Kv2.1, including decreased deactivation rates, decreased TEA sensitivity, and a hyperpolarizing shift of half-maximal activation. Protein-protein interaction between Kv2.1 and Kv6.1 N-termini was confirmed by yeast two-hybrid; Kv6.1 amino termini could not form homomultimers but specifically interacted with Kv2.1 N-termini.\",\n      \"method\": \"Two-electrode voltage-clamp in Xenopus oocytes, yeast two-hybrid assay\",\n      \"journal\": \"FEBS Letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — yeast two-hybrid plus functional electrophysiology of novel heteromeric current, two orthogonal methods\",\n      \"pmids\": [\"8980147\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Kv2.1 surface clusters are bounded by a cortical actin-based perimeter fence. Channels within clusters are mobile (FRAP tau ~14 s) but are retained within the cluster boundary. Latrunculin A treatment caused cluster enlargement and loss of soma restriction, demonstrating that cortical actin maintains both cluster size and somatic localization. Channels lacking the C-terminus do not form clusters and diffuse freely.\",\n      \"method\": \"FRAP, quantum dot single-channel tracking, latrunculin A treatment, GFP-Kv2.1 live imaging in HEK cells and hippocampal neurons\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — FRAP plus single-particle tracking plus actin disruption, replicated in two cell types\",\n      \"pmids\": [\"16988031\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Kv2.1 surface clusters serve as specialized insertion platforms for membrane protein trafficking. TIRF-FRAP and quantum dot imaging showed >85% of cytoplasmic and recycling Kv2.1, and >85% of recycling Kv1.4, are delivered to the cell surface at Kv2.1 cluster perimeters. Actin depolymerization redirected Kv2.1 exocytosis to cluster-free membrane areas.\",\n      \"method\": \"TIRF-FRAP, quantum dot single-channel imaging, actin depolymerization, live-cell imaging in HEK cells and hippocampal neurons\",\n      \"journal\": \"Molecular Biology of the Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two orthogonal live-imaging methods with pharmacological perturbation, replicated in two cell types\",\n      \"pmids\": [\"22648171\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Kv2.1 clustering at ER-plasma membrane junctions promotes spatial and functional coupling of L-type Ca2+ channels (LTCCs) to ryanodine receptor (RyR) ER Ca2+ release channels. Kv2.1 clustering unexpectedly enhanced LTCC opening at polarized membrane potentials. This enabled Kv2.1-LTCC-RyR triads to generate localized Ca2+ sparks independently of action potentials.\",\n      \"method\": \"Proximity proteomics (BioID), immunofluorescence co-localization, Ca2+ spark imaging, LTCC single-channel recordings, Kv2.1 knockout/knockdown\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — proximity proteomics plus functional imaging plus electrophysiology, multiple orthogonal methods\",\n      \"pmids\": [\"31663850\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"SNAP-25 associates with Kv2.1 via the channel's N-terminus and reduces Kv2.1-mediated currents by ~70% in heterologous cells and ~40% in rat beta-cells. Co-dialysis of a Kv2.1 N-terminal peptide partially relieved inhibition. SNAP-25 had no effect on beta-cell K+ currents after dominant-negative Kv2.1 knockout, confirming specificity.\",\n      \"method\": \"Co-immunoprecipitation, in vitro peptide binding, whole-cell patch-clamp, dominant-negative KO in beta-cells\",\n      \"journal\": \"Molecular Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — co-IP plus in vitro binding plus functional electrophysiology with dominant-negative specificity control\",\n      \"pmids\": [\"12403834\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Kv2.1 and CaV1.2 (but not Kv1.4, SUR1, or Kir6.2) localize to cholesterol-rich lipid raft domains in pancreatic beta-cell plasma membranes, along with SNARE proteins syntaxin 1A, SNAP-25, and VAMP-2. Disruption of lipid rafts by methyl-β-cyclodextrin shunts Kv2.1 out of rafts and inhibits Kv2.1 (but not CaV1.2) channel activity, enhancing insulin exocytosis.\",\n      \"method\": \"Detergent-resistant membrane fractionation, methyl-β-cyclodextrin treatment, whole-cell patch-clamp, single-cell exocytosis imaging\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — biochemical fractionation plus pharmacological disruption plus functional electrophysiology with channel-selective readouts\",\n      \"pmids\": [\"15073181\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Syntaxin 1A (Syx) physically interacts with the Kv2.1 C-terminus at the cell surface, causing hyperpolarizing shifts in steady-state activation and inactivation. Peptides competing for Syx binding to the C-terminus reversed these effects when injected into oocytes already co-expressing both proteins. The t-SNARE complex (Syx/SNAP-25) also binds the Kv2.1 C-terminus and modulates inactivation; partial C-terminal deletions dissipated both interactions.\",\n      \"method\": \"Competitive peptide injection in Xenopus oocytes, C-terminal deletion mutagenesis, two-electrode voltage-clamp\",\n      \"journal\": \"Molecular Pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — competitive peptide displacement plus mutagenesis to causally link physical and functional interactions, single lab\",\n      \"pmids\": [\"15525758\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Tyrosine 124 in the T1 cytosolic domain of Kv2.1 is phosphorylated by Src kinase in vitro and in cells. Y124 phosphorylation is critical for Src-mediated upregulation (~3-fold) of Kv2.1 K+ current; Y124F mutation greatly reduced current upregulation by Src. The phosphatase cyt-PTPepsilon dephosphorylates Y124, counteracting Src. Expression, localization, and voltage dependence were unchanged in Y124F channels.\",\n      \"method\": \"In vitro kinase assay, substrate-trapping mutant co-IP, site-directed mutagenesis (Y124F), whole-cell patch-clamp\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assay plus substrate-trapping plus mutagenesis with functional electrophysiology readout\",\n      \"pmids\": [\"12615930\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Extrasynaptic (but not synaptic) NMDA receptor activation potently unclusters and dephosphorylates Kv2.1, producing a hyperpolarizing shift in voltage-dependent activation of hippocampal I_K. Inhibition of glutamate transporters (EAAT2) activated extrasynaptic NMDA receptors and dephosphorylated Kv2.1. Moderate seizure activity in vivo did not dephosphorylate Kv2.1, demonstrating specificity for extrasynaptic receptor pools.\",\n      \"method\": \"Bath NMDA application, selective extrasynaptic NMDA receptor activation, EAAT inhibition, immunoblot for Kv2.1 phosphorylation, immunofluorescence cluster analysis, whole-cell patch-clamp\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — pharmacological dissection of synaptic vs. extrasynaptic receptors with both biochemical and functional readouts, in vitro and in vivo\",\n      \"pmids\": [\"18753382\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CaMKII activation (triggered by oxidant-induced intracellular Ca2+ release) is required for the pro-apoptotic insertion of Kv2.1 channels into the plasma membrane. CaMKII modulates the interaction of syntaxin with Kv2.1, enabling the SNARE-dependent membrane insertion responsible for the K+ current surge that drives apoptotic K+ loss. CaMKII inhibition prevented K+ current enhancement and increased neuronal viability.\",\n      \"method\": \"Pharmacological and molecular CaMKII inhibition, intracellular Ca2+ imaging, whole-cell patch-clamp, syntaxin-Kv2.1 co-IP, cell viability assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Ca2+ imaging plus protein interaction plus electrophysiology plus viability, mechanistic cascade established with multiple interventions\",\n      \"pmids\": [\"23918396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"AMIGO (an adhesion protein with LRR and Ig domains) is an auxiliary subunit of the Kv2.1 channel complex, showing extensive co-localization and co-immunoprecipitation with Kv2.1 in mouse brain. AMIGO increases Kv2.1 conductance in a voltage-dependent manner in HEK cells. Inhibition of endogenous AMIGO suppresses neuronal I_K at negative membrane voltages.\",\n      \"method\": \"Co-immunoprecipitation from mouse brain, immunohistochemistry, whole-cell patch-clamp in HEK cells and hippocampal neurons, endogenous AMIGO RNAi knockdown\",\n      \"journal\": \"EMBO Reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — native brain co-IP plus heterologous gain-of-function plus endogenous knockdown in neurons, multiple orthogonal methods\",\n      \"pmids\": [\"22056818\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The N- and C-terminal intracellular regions of Kv2.1 interact directly (demonstrated by GST pulldown of the N-terminus binding the C-terminus) and together determine channel activation kinetics. Specific residues in the N-terminal T1 domain (Q67, D75) and the C-terminal CTA domain (aa 740–853) modulate activation rate, and N-C terminal interactions are required for normal kinetics.\",\n      \"method\": \"GST fusion protein pulldown, chimeric channels between human and rat Kv2.1, two-electrode voltage-clamp in Xenopus oocytes\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct in vitro protein interaction plus chimeric mutagenesis with functional electrophysiology, single lab\",\n      \"pmids\": [\"12560340\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Voltage-gating of Kv2.1 induces relative rearrangements between N- and C-terminal domains: FRET between N- and C-terminal fluorescent tags on the same or different subunits decreased upon depolarization (+60 mV). N-terminal tags did not rearrange relative to each other. These movements occur in a plane parallel to the plasma membrane within 1–10 nm, and are distinct from movements relative to the membrane.\",\n      \"method\": \"FRET microscopy with N- and C-terminal CFP/YFP fusions, combined with patch-clamp (COS1 cells)\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — FRET-patch-clamp with multiple control constructs in same study, direct structural-functional link\",\n      \"pmids\": [\"16690619\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Kv2.1 forms a complex with focal adhesion kinase (FAK) through an LD-like motif in its N-terminus, promoting FAK phosphorylation at Y397 and Y576/577. FAK expression promotes polarized membrane distribution of Kv2.1. shRNA knockdown of Kv2.1 or N-terminal point mutations minimized FAK phosphorylation and impaired cell migration.\",\n      \"method\": \"Co-immunoprecipitation, shRNA knockdown, N-terminal point mutations, phosphospecific immunoblotting, migration assays\",\n      \"journal\": \"Journal of Cellular Physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus mutagenesis plus knockdown, single lab, functional migration readout\",\n      \"pmids\": [\"18615577\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"De novo KCNB1 missense mutations causing epileptic encephalopathy result in loss of Kv2.1 ion selectivity and gain of a depolarizing inward cation conductance, as established by heterologous expression and functional electrophysiology in three patients.\",\n      \"method\": \"Whole exome sequencing, heterologous expression in mammalian cells, whole-cell patch-clamp\",\n      \"journal\": \"Annals of Neurology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — functional characterization of three independent patient mutations all showing the same loss-of-selectivity mechanism\",\n      \"pmids\": [\"25164438\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The KCNB1-V378A epileptic encephalopathy variant produces voltage-activated but non-selective Kv2.1 currents (loss of ion selectivity while retaining voltage sensitivity). Cell-type-dependent differences in expression and subcellular localization of V378A were observed, and co-expression of V378A and wild-type Kv2.1 reciprocally affected their trafficking.\",\n      \"method\": \"Heterologous expression, whole-cell patch-clamp, guangxitoxin-1E pharmacology, immunofluorescence\",\n      \"journal\": \"The Journal of General Physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — detailed electrophysiology plus subcellular localization plus co-expression trafficking assays in single study\",\n      \"pmids\": [\"26503721\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"KCNB1-R306C (voltage sensor) disrupted voltage sensor sensitivity and cooperativity, while KCNB1-G401R (pore domain) selectively abolished endogenous Kv2 currents in transfected pyramidal neurons via dominant-negative action. Both mutants inhibited repetitive neuronal firing by preventing production of deep interspike voltages.\",\n      \"method\": \"Heterologous expression, whole-cell patch-clamp, endogenous Kv2 current measurement in pyramidal neurons, dominant-negative functional testing\",\n      \"journal\": \"Scientific Reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mechanistic dissection of two distinct disease mutations with endogenous neuron recordings, single lab\",\n      \"pmids\": [\"26477325\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"SUMO1 conjugation to Kv2.1 inhibits K+ current by ~80% (direct recombinant SUMO1 infusion) or ~48% (SUMO1-YFP co-expression) in HEK cells, and by ~49% in human beta-cells. The inhibitory effect results from acceleration of inactivation and inhibition of recovery from inactivation, widening beta-cell action potentials and decreasing firing frequency. Effects are augmented by Ubc9 and rescued by SENP1.\",\n      \"method\": \"Co-immunoprecipitation, direct intracellular SUMO1 peptide infusion, whole-cell patch-clamp in HEK and beta-cells, SUMO protease rescue\",\n      \"journal\": \"Journal of Cell Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — co-IP plus direct peptide infusion plus enzyme-mediated rescue in native beta-cells, multiple orthogonal methods\",\n      \"pmids\": [\"19223394\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Incretin hormones GIP and GLP-1 promote phosphorylation and acetylation of Kv2.1 via PKA/MSK-1 and HAT/HDAC pathways in pancreatic beta-cells. Acetylation of Kv2.1 is mediated by nuclear/cytoplasmic shuttling of CREB binding protein (CBP) and its direct interaction with Kv2.1. These post-translational modifications of Kv2.1 underlie the prosurvival effects of incretins.\",\n      \"method\": \"Overexpression and pharmacological inhibition, phosphorylation/acetylation immunoblotting, CBP-Kv2.1 co-immunoprecipitation, nuclear shuttling assays\",\n      \"journal\": \"Cell Death and Differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus PTM assays plus pharmacological dissection, single lab, mechanistic pathway mapped\",\n      \"pmids\": [\"21818121\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Kv2.1 uses two distinct trafficking pathways to reach different subcellular compartments: the conventional Golgi-dependent secretory pathway for somatodendritic targeting, and a non-conventional Golgi-independent pathway for axon initial segment (AIS) targeting. A distinct AIS trafficking motif in the Kv2.1 C-terminus with putative phosphorylation sites is required for clustered AIS localization.\",\n      \"method\": \"FRAP, Golgi disruption pharmacology, mutagenesis of C-terminal AIS motif and phosphorylation sites, photoactivatable-GFP imaging in hippocampal neurons\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — FRAP plus pharmacological pathway dissection plus mutagenesis with spatial live imaging, multiple orthogonal approaches\",\n      \"pmids\": [\"29042434\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Conserved negatively charged aspartates (CDD motif) in the A/B linker of the T1 tetramerization domain are required for efficient assembly of both homotetrameric Kv2.1 and heterotetrameric Kv2.1/Kv6.4 channels. Charge-reversal arginine substitutions in Kv2.1 or Kv6.4 blocked tetramer assembly (FRET) without impairing trafficking to the membrane.\",\n      \"method\": \"FRET confocal microscopy, co-immunoprecipitation, immunocytochemistry, charge-reversal mutagenesis\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — FRET plus co-IP plus mutagenesis defining specific assembly determinant, multiple orthogonal methods\",\n      \"pmids\": [\"19717558\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Histidine 105 in the T1 domain of Kv2.1 is required for heteromerization with Kv6.3 and Kv6.4 but not for Kv2.1 homoassembly. H105V or H105R mutations disrupted T1-T1 interaction with Kv6.3/Kv6.4 (yeast two-hybrid), reduced FRET between Kv2.1 and Kv6.3/6.4, prevented co-immunoprecipitation, and abolished Kv6.3/6.4-mediated shifts in voltage dependence of Kv2.1 activation.\",\n      \"method\": \"Yeast two-hybrid, FRET confocal microscopy, co-immunoprecipitation, site-directed mutagenesis, whole-cell patch-clamp\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — three orthogonal binding assays (yeast two-hybrid, FRET, co-IP) plus functional electrophysiology, single rigorous study\",\n      \"pmids\": [\"19074135\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Oxidized KCNB1 channels form oligomers held by Cys-73 disulfide bridges and accumulate in the plasma membrane due to defective dynamin 2-dependent endocytosis. KCNB1 oligomers in lipid rafts disrupt raft integrity and activate c-Src/JNK signaling to promote apoptosis. C73A-mutant channels do not oligomerize and are normally internalized.\",\n      \"method\": \"Biochemical oligomerization assays, dynamin inhibition, cholesterol manipulation, c-Src/JNK inhibition (pharmacological and molecular), co-immunoprecipitation\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mechanistic cascade from oxidation to oligomerization to endocytosis block to Src/JNK activation, multiple interventions and C73A control\",\n      \"pmids\": [\"23275378\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Oxidized KCNB1 channels form macromolecular complexes with integrin alpha-5 (integrin-α5). Upon KCNB1 oxidation, the integrin-FAK-Src/Fyn apoptotic signaling cascade is activated. C73A non-oxidizable mutant channels retained integrin-α5 interaction but did not activate FAK/Src/Fyn, demonstrating that the oxidized state specifically triggers integrin signaling.\",\n      \"method\": \"Co-immunoprecipitation from mouse brain, pharmacological integrin/FAK inhibition, C73A KCNB1 mutant, FAK/Src kinase activity assays\",\n      \"journal\": \"Cell Death & Disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — native brain co-IP plus loss-of-function pharmacology plus non-oxidizable mutant control, mechanistic pathway established\",\n      \"pmids\": [\"28383553\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Kv2.1 mediates neuroprotection by maintaining ER-plasma membrane junctions through its interaction with VAPA. TAT-DP-2, a membrane-permeable peptide derived from Kv2.2 C-terminus, disrupts the Kv2.1-VAPA association, induces Kv2.1 declustering, prevents pro-apoptotic K+ current enhancement after injury, and reduces infarct size in murine ischemia-reperfusion, demonstrating that Kv2.1-VAPA interaction is required for post-injury channel clustering and cell death.\",\n      \"method\": \"TAT-peptide declustering, Kv2.1-VAPA co-immunoprecipitation, whole-cell patch-clamp, in vivo ischemia-reperfusion mouse model, infarct size measurement\",\n      \"journal\": \"Science Advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — molecular disruption of specific protein-protein interaction confirmed biochemically plus in vitro and in vivo functional validation\",\n      \"pmids\": [\"32937450\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Kv2.1 (via its non-conducting structural role binding ER protein VAP/VAMP-associated protein) enables activity-dependent ER Ca2+ uptake in both soma and axons. Kv2.1 knockdown rendered the ER unable to accumulate Ca2+ during electrical activity and impaired synaptic vesicle fusion during stimulation, revealing an essential non-conducting role for Kv2.1 in maintaining ER Ca2+ homeostasis and synaptic transmission.\",\n      \"method\": \"Kv2.1 shRNA knockdown, live Ca2+ imaging in soma and axons, synaptic vesicle fusion assays, electrical stimulation protocols\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KD with specific phenotypic readouts in multiple compartments (soma and axon), mechanistic link to VAPA binding established\",\n      \"pmids\": [\"35862456\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"In pancreatic beta-cells, Kv2.1 (but not Kv2.2) forms clusters of 6–12 tetrameric channels at the plasma membrane and facilitates insulin exocytosis by promoting secretory granule targeting. A truncated Kv2.1 (ΔC318) that retains electrical function and syntaxin 1A binding but cannot form clusters does not enhance granule recruitment or exocytosis, demonstrating that the structural clustering role—not K+ conductance—is required for exocytosis facilitation.\",\n      \"method\": \"Kv2.1 knockdown, Kv2.1-ΔC318 expression, TIRF microscopy of granule dynamics, whole-cell patch-clamp, T2D islet experiments\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clustering-deficient mutant dissociates electrical from structural function, plus T2D rescue experiment, multiple readouts\",\n      \"pmids\": [\"28607108\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"MiRP2 (KCNE3) forms native complexes with Kv2.1 in rat brain (co-immunoprecipitation). MiRP2 reduces Kv2.1 current density and slows both activation and deactivation. Altering MiRP2 expression by RNAi or cDNA transfection toggles endogenous delayed-rectifier current magnitude and kinetics in PC12 cells and hippocampal neurons.\",\n      \"method\": \"Co-immunoprecipitation from rat brain, RNAi knockdown, cDNA overexpression, whole-cell patch-clamp in PC12 cells and hippocampal neurons\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — native brain co-IP plus gain and loss of function in endogenous system with functional readout\",\n      \"pmids\": [\"12954870\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"MinK (KCNE1) and MiRP1 (KCNE2) form native cardiac complexes with Kv2.1 (co-immunoprecipitation from rat heart). Both reduce Kv2.1 current density and slow activation/deactivation. Disease-associated LQTS mutations in MinK and MiRP1 further alter Kv2.1 gating (D76N-MinK reduces current density 3-fold; I57T-MiRP1 slows activation 5-fold).\",\n      \"method\": \"Co-immunoprecipitation from rat heart, whole-cell patch-clamp in CHO cells with mutant subunit co-expression\",\n      \"journal\": \"The Journal of Membrane Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — native tissue co-IP plus heterologous functional characterization including disease variants, single lab\",\n      \"pmids\": [\"19219384\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Src kinase phosphorylates Kv2.1 at two novel tyrosine sites: Y686 (regulates channel activity, similar to Y124) and Y810 (regulates intracellular trafficking of Kv2.1 channels). Src also increases Kv2.1 protein expression levels.\",\n      \"method\": \"Mass spectrometry identification of phosphotyrosine sites, site-directed mutagenesis, whole-cell patch-clamp, Kv2.1 trafficking assays\",\n      \"journal\": \"Journal of Proteome Research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS identification plus mutagenesis plus functional assays, single lab\",\n      \"pmids\": [\"22106938\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"During M-phase of the cell cycle, Kv2.1 undergoes increased phosphorylation at C-terminal sites and redistributes from diffuse to robust clusters at plasma membrane–ER membrane contact sites (PM:ER MCS) in COS-1 cells, inducing more extensive PM:ER MCS during mitosis. The same C-terminal targeting motif required for neuronal clustering is required for M-phase clustering.\",\n      \"method\": \"Phosphospecific immunoblotting, immunofluorescence, cell cycle synchronization, confocal microscopy in COS-1/CHO cells\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell cycle synchronization plus phosphorylation mapping plus localization, functional consequence of M-phase clustering not fully established\",\n      \"pmids\": [\"26442584\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"BACE2 cleaves Kv2.1 at three sites (Thr376, Ala717, Ser769), disrupts Kv2.1 clustering, reduces delayed rectifier I_K, and causes a hyperpolarizing shift in activation in primary neurons. BACE2-cleaved Kv2.1 fragments (Kv2.1-1-375, -1-716, -1-768) each reduce apoptosis, suggesting BACE2-mediated cleavage is neuroprotective.\",\n      \"method\": \"In vitro cleavage assay identifying cleavage sites, immunofluorescence clustering analysis, whole-cell patch-clamp, apoptosis assays\",\n      \"journal\": \"Molecular Psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proteolytic site mapping plus functional channel readouts, single lab study\",\n      \"pmids\": [\"29703946\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Acute SDF-1α/CXCR4 signaling causes calcineurin-dependent dephosphorylation and altered localization of Kv2.1, enhancing voltage-dependent activation (neuroprotective). Prolonged SDF-1α/CXCR4 signaling activates p38 MAPK, which phosphorylates Kv2.1 at S800 and enhances surface trafficking, predisposing neurons to excessive K+ efflux and apoptosis. Kv2.1-S800A mutant prevented CXCR4-dependent apoptosis.\",\n      \"method\": \"Immunoblotting for Kv2.1 phosphorylation, S800A mutagenesis, whole-cell patch-clamp, immunofluorescence cluster analysis, CXCR4 pharmacological/genetic manipulation\",\n      \"journal\": \"The Journal of Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — specific phospho-site mutant (S800A) causally links CXCR4-p38 signaling to apoptotic Kv2.1 trafficking, multiple readouts\",\n      \"pmids\": [\"23223293\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PIP2 regulates Kv2.1 by modulating its inactivation mechanism: PIP2 prevents rundown and shifts voltage-dependence of inactivation in inside-out patches. PIP2 depletion accelerates closed-state inactivation and delays recovery from inactivation without affecting activation. Modeled by allosteric interaction of PIP2 with the inactivation gate.\",\n      \"method\": \"Excised inside-out patch clamp with exogenous PIP2, rapamycin-induced 5-phosphatase translocation (FKBP-Inp54p), M1 receptor activation\",\n      \"journal\": \"Scientific Reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct lipid application to excised patches plus orthogonal depletion strategies, single lab\",\n      \"pmids\": [\"29379118\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The pro-apoptotic dual phosphorylation of Kv2.1 at Y124 (by Src) and S800 (by p38) is co-regulated: intact Y124 is required for p38 phosphorylation of S800, and Src phosphorylation of Y124 facilitates p38 action at S800. Conversely, S800A mutation reduces Src action on Y124. Cys73 (but not Cys710) at the N-terminus is required for p38-dependent S800 phosphorylation and apoptotic K+ current enhancement.\",\n      \"method\": \"Immunoprecipitation with phosphospecific antibodies, site-directed mutagenesis of Y124, S800, C73, C710, whole-cell patch-clamp in CHO cells\",\n      \"journal\": \"PloS One\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phosphospecific antibodies plus multiple mutants, single lab, mechanistic co-regulation pathway established\",\n      \"pmids\": [\"26115091\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"KCNB1 forms complexes with integrins α5β5 (integrin-K+ channel complexes, IKCs) in the neocortex. KCNB1 null mice show impaired neocortical neuronal migration, disrupted morphology and synaptic connectivity. Knock-in R312H mice (DEE variant) show the same developmental defects with impaired IKC biochemical signaling. Angiotensin II (FAK agonist) rescued R312H neuronal abnormalities in vitro, implicating non-conducting IKC signaling in cortical development.\",\n      \"method\": \"KCNB1 null and knock-in (R312H) mice, neuronal migration assays, co-immunoprecipitation (KCNB1-integrin), pharmacological FAK activation rescue\",\n      \"journal\": \"Cell Death and Differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic null plus knock-in plus co-IP of native complex plus pharmacological rescue, mechanistic non-conducting role established\",\n      \"pmids\": [\"36207442\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In arterial smooth muscle cells, Kv2.1 has a dual role: a canonical conductive role (less than 1% of channels are conductive and hyperpolarize the membrane) and a structural role in enhancing clustering and cooperative opening of CaV1.2 L-type Ca2+ channels. In female myocytes where Kv2.1 expression is higher, the structural role dominates, increasing CaV1.2 cluster size, Ca2+ influx, and myogenic tone. In male myocytes, Kv2.1 primarily controls membrane potential.\",\n      \"method\": \"Kv2.1 KO, electrophysiology, TIRF microscopy (CaV1.2 cluster imaging), sex-stratified analysis of Kv2.1 expression and function in myocytes\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO plus structural imaging plus functional electrophysiology, sex-stratified mechanistic dissection with multiple orthogonal approaches\",\n      \"pmids\": [\"32015129\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Leptin increases Kv2.1 surface expression in beta-cells via AMPK activation (requiring CaMKKβ) and PKA. The increased Kv2.1 surface expression depends on actin depolymerization. This trafficking regulation mirrors leptin's concurrent trafficking regulation of KATP channels, coordinately inhibiting insulin secretion by hyperpolarizing membrane potential (via KATP) and accelerating repolarization (via Kv2.1).\",\n      \"method\": \"Surface biotinylation, AMPK/PKA pharmacological and genetic manipulation, actin disruption, whole-cell patch-clamp in rodent and human beta-cells\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — surface expression quantification plus pathway inhibition experiments, functional readout in native beta-cells\",\n      \"pmids\": [\"26453299\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Kv2.1-G379R (DEE variant) does not induce ER-plasma membrane junction formation in HEK293T cells, and co-expression of G379R with wild-type Kv2.1 reduces EPJ induction relative to WT alone, consistent with dominant-negative disruption of the structural (non-conducting) function of Kv2.1.\",\n      \"method\": \"HEK293T cell expression, immunofluorescence of ER-PM junctions, co-expression dominant-negative assessment\",\n      \"journal\": \"Neurobiology of Disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — heterologous expression with clear structural readout, single lab, establishes non-conducting function impairment\",\n      \"pmids\": [\"33132203\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"NFATc3 is an obligatory component of the signaling cascade mediating Ang II-induced reduction of Kv2.1 expression in arterial smooth muscle. Sustained Ang II increases smooth muscle Ca2+ via L-type channels, activates calcineurin and NFATc3, and decreases Kv2.1 K+ channel subunit expression and Kv current.\",\n      \"method\": \"Dominant-negative NFATc3, calcineurin inhibition, pharmacological L-type Ca2+ channel block, immunoblotting, patch-clamp in arterial smooth muscle\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — dominant-negative transcription factor plus pathway inhibition with functional current readout, single lab\",\n      \"pmids\": [\"15322114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"N-terminal SNAP-25 domains (residues 1–197 and 1–180), acting on the Kv2.1 cytoplasmic N-terminus, increased Kv2.1 activation rate, slowed inactivation, and potentiated external TEA block by restructuring the outer pore architecture. Full-length SNAP-25 and C-terminal domains had no such effect, demonstrating domain-specific regulation.\",\n      \"method\": \"Intracellular dialysis of SNAP-25 domain peptides, whole-cell patch-clamp, external TEA block analysis, ionic substitution experiments\",\n      \"journal\": \"The Biochemical Journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain peptide dialysis with functional electrophysiology showing pore architecture changes, single lab\",\n      \"pmids\": [\"16478442\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Somatic Kv2.1 clusters in striatal medium spiny neurons (MSNs) are juxtaposed to ryanodine receptor (RyR) Ca2+-release channel clusters at subsurface cisternae. Acute RyR stimulation in heterologous cells caused a rapid hyperpolarizing shift in Kv2.1 voltage-dependent activation consistent with Ca2+/calcineurin-dependent dephosphorylation. MSNs in direct and indirect pathways differ in Kv2.1 phosphorylation state at multiple sites.\",\n      \"method\": \"Electron microscopy-immunogold labeling, immunofluorescence in transgenic GFP-MSN mice, phosphospecific antibody immunolabeling, RyR agonist treatment in heterologous cells, patch-clamp\",\n      \"journal\": \"The Journal of Comparative Neurology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — EM-immunogold plus functional RyR-Kv2.1 coupling in cells plus cell-type-specific phosphorylation profiling, multiple methods\",\n      \"pmids\": [\"24962901\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Kv2.1 (KCNB1) is a voltage-gated delayed-rectifier K+ channel that (1) conducts K+ primarily as a nonclustered minority of surface channels, with its gating graded by multisite phosphorylation (by CDK5, AMPK, Src, p38) and dephosphorylation (by calcineurin), SUMOylation, and accessory subunits (AMIGO, MiRP2, MinK, silent Kv5/6/8/9 subunits); (2) forms large ER–plasma membrane junction-inducing clusters at the neuronal soma/proximal dendrites and AIS via a C-terminal domain-dependent, actin-gated, phosphorylation-regulated mechanism that is mechanistically distinct from its conducting role; (3) serves a non-conducting structural function at these junctions—scaffolding LTCC-RyR Ca2+ signaling triads, enabling activity-dependent ER Ca2+ uptake, facilitating SNARE-dependent synaptic vesicle fusion, and promoting insulin exocytosis in beta-cells through secretory granule recruitment; and (4) mediates neuronal apoptosis via a Zn2+/CaMKII/SNARE-dependent plasma membrane insertion program (requiring coordinated Src-Y124 and p38-S800 phosphorylation and integrin-FAK signaling), while oxidative modification at Cys73 drives oligomerization, defective endocytosis, and pro-apoptotic c-Src/JNK activation through disruption of lipid raft integrity.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"KCNB1 encodes Kv2.1, a voltage-gated delayed-rectifier K+ channel whose biology is split between a canonical conducting role in membrane repolarization and a non-conducting structural role organizing ER\\u2013plasma membrane junctions [#6, #7]. As a channel, Kv2.1 assembles as a tetramer through T1-domain determinants (a CDD motif and His105) that also govern heteromerization with silent regulatory subunits such as Kv5.1 and Kv6.1, which reshape its gating [#33, #34, #12, #13], and it is decorated by accessory subunits AMIGO, MiRP2/KCNE3, and MinK/MiRP1 that tune current density and kinetics [#23, #40, #41]. Its voltage dependence is graded by an unusually rich array of reversible modifications: multisite C-terminal serine phosphorylation by CDK5 and AMPK opposed by calcineurin-mediated dephosphorylation [#0, #4, #8, #10], Src-mediated tyrosine phosphorylation [#20], SUMOylation at K470 [#9, #30], and PIP2 binding [#46], so that activity-dependent signals (e.g. extrasynaptic NMDA receptor activation) reset neuronal excitability through cluster dispersal and dephosphorylation [#21]. Strikingly, only ~2% of surface channels conduct, while clustered channels are largely electrically silent and instead tether cortical ER to the plasma membrane via the VAP-family protein VAPA, an interaction directed by an autonomous, actin-gated C-terminal targeting module [#5, #6, #7, #14, #37]. These non-conducting junctions scaffold Ca2+ signaling triads coupling L-type Ca2+ channels to ryanodine receptors, support activity-dependent ER Ca2+ uptake and synaptic vesicle fusion, organize membrane-protein trafficking platforms, and drive insulin granule recruitment in beta-cells\\u2014functions that survive in clustering-competent but conduction-independent constructs [#16, #38, #15, #39, #54]. In pancreatic beta-cells Kv2.1 dominates action-potential repolarization and restrains glucose-stimulated insulin secretion, and is itself regulated by SNARE proteins, lipid rafts, and incretin/leptin signaling [#3, #17, #18, #50]. Kv2.1 also executes a pro-apoptotic program in which oxidant- or injury-triggered Zn2+/CaMKII signaling drives SNARE-dependent insertion of channels and a surge of K+ efflux, gated by coordinated Src-Y124 and p38-S800 phosphorylation and Cys73-dependent oxidative oligomerization that activates integrin-FAK and c-Src/JNK signaling [#2, #22, #35, #36, #45, #47]. Beyond neurons it organizes integrin \\u03b15\\u03b25 \\\"integrin-K+ channel complexes\\\" required for neocortical neuronal migration and connectivity, and contributes a sex-dependent structural role in arterial smooth muscle by clustering CaV1.2 [#48, #49]. De novo KCNB1 missense mutations cause epileptic encephalopathy, acting through loss of ion selectivity with a gained inward cation conductance, dominant-negative suppression of endogenous Kv2 current, or disruption of the non-conducting ER\\u2013PM junction\\u2013inducing and integrin-signaling functions [#27, #28, #29, #51, #48].\",\n  \"teleology\": [\n    {\n      \"year\": 1995,\n      \"claim\": \"Established a high-affinity pharmacological probe and showed Kv2.1's toxin sensitivity maps outside the canonical scorpion-toxin pore region, defining a distinct gating-modifier interaction surface.\",\n      \"evidence\": \"Tarantula hanatoxin isolation and voltage-clamp kinetics across channel families\",\n      \"pmids\": [\"7576642\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the hanatoxin binding site not resolved\", \"Does not address physiological regulation\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Localized the gating-modulatory phosphorylation to the C-terminal cytoplasmic domain, establishing that reversible C-terminal serine phosphorylation directly sets Kv2.1 voltage dependence.\",\n      \"evidence\": \"C-terminal truncation, 32P labeling, and patch-clamp with intracellular phosphatase rescue\",\n      \"pmids\": [\"9351973\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific kinases and sites not yet identified\", \"Number of functional phospho-sites unknown\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Defined an autonomous C-terminal cytoplasmic domain necessary and sufficient for high-density clustering and polarized targeting, the first hint that localization is genetically separable from channel function.\",\n      \"evidence\": \"Truncation and chimeric constructs in polarized MDCK cells with detergent-solubility analysis\",\n      \"pmids\": [\"8978827\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular tether mediating clustering not identified\", \"Link between detergent insolubility and cytoskeleton not directly shown\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Showed Kv2.1 coassembles with silent Kv6 subunits to generate heteromeric channels with novel gating, expanding the functional repertoire of Kv2.1-containing channels.\",\n      \"evidence\": \"Two-electrode voltage-clamp and yeast two-hybrid of N-terminal interactions (Kv6.1; extended to Kv5.1/Kv6.1)\",\n      \"pmids\": [\"8980147\", \"9696692\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of heteromers in vivo unknown\", \"Physiological contexts of silent-subunit modulation not defined\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Demonstrated Kv2.1 is the dominant beta-cell delayed rectifier restraining insulin secretion, defining a non-neuronal physiological role in glucose homeostasis.\",\n      \"evidence\": \"Dominant-negative knockout, selective antagonist, Ca2+ imaging, and islet perfusion\",\n      \"pmids\": [\"12270920\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not yet distinguish conducting vs structural contributions to secretion\", \"In vivo whole-animal phenotype not addressed\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identified Kv2.1 as necessary and sufficient for the apoptotic K+ efflux in neurons, linking the channel to programmed cell death.\",\n      \"evidence\": \"Dominant-negative expression and reconstitution in channel-null CHO cells with multiple apoptogens\",\n      \"pmids\": [\"12832499\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of the apoptotic current surge not defined\", \"Signaling triggers upstream unknown\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Mapped early protein interactions and modifications governing channel function: SNAP-25 binding to the N-terminus, Src phosphorylation of T1-domain Y124, and direct N\\u2013C terminal interaction controlling kinetics.\",\n      \"evidence\": \"Co-IP, in vitro kinase/substrate-trapping, GST pulldown, and electrophysiology\",\n      \"pmids\": [\"12403834\", \"12615930\", \"12560340\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether these interactions cooperate was not established\", \"In vivo relevance of Y124 phosphorylation not tested\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Established graded, multisite phosphorylation as the logic of Kv2.1 regulation and showed the C-terminal domain is a transferable module conferring clustering, gating, and cholinergic/calcineurin modulation.\",\n      \"evidence\": \"MS-SILAC site mapping with additive mutagenesis; domain-swap chimeras with biochemical and electrophysiological readouts; FRET reporting N\\u2013C domain rearrangement on gating\",\n      \"pmids\": [\"16917065\", \"16407566\", \"16690619\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Individual kinases for most sites not yet assigned\", \"Structural model of clustering still absent\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Revealed cortical actin as a perimeter fence retaining mobile channels within clusters and restricting somatic localization, providing the cytoskeletal basis for cluster organization.\",\n      \"evidence\": \"FRAP, quantum-dot tracking, and latrunculin A disruption in HEK cells and neurons\",\n      \"pmids\": [\"16988031\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link between C-terminus and actin not defined\", \"How clusters nucleate not addressed\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Connected physiological signaling to Kv2.1 regulation by showing extrasynaptic NMDA receptor activation specifically declusters and dephosphorylates the channel, and linked Kv2.1 to integrin/FAK signaling via an N-terminal LD-like motif.\",\n      \"evidence\": \"Pharmacological synaptic/extrasynaptic dissection with biochemical and electrophysiological readouts; co-IP, knockdown, and migration assays\",\n      \"pmids\": [\"18753382\", \"18615577\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"FAK interaction confidence is Medium and single-lab\", \"Physiological trigger linking glutamate to FAK not unified\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Defined T1-domain assembly determinants (CDD motif) and demonstrated SUMOylation as a reversible inhibitory modification of beta-cell and neuronal Kv2.1 current.\",\n      \"evidence\": \"FRET/co-IP charge-reversal mutagenesis; SUMO1 infusion with SENP1 rescue in HEK and human beta-cells; NFATc3-dependent transcriptional downregulation in smooth muscle; MinK/MiRP1 cardiac complexes\",\n      \"pmids\": [\"19717558\", \"19223394\", \"15322114\", \"19219384\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Coordination between SUMO and phospho-regulation not resolved\", \"Cardiac role of Kv2.1 physiologically uncertain (Medium evidence)\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Overturned the assumption that clusters are conducting reservoirs by showing only ~2% of surface channels conduct and declustering does not unmask current, separating Kv2.1's conducting and clustering roles.\",\n      \"evidence\": \"Spatially resolved cell-attached single-channel recording with FRAP, phosphatase, and actin perturbation\",\n      \"pmids\": [\"20566856\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Function of the non-conducting cluster pool not yet known at this point\", \"Why most channels are silent unexplained\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Assigned specific kinases to the graded regulation: CDK5 sets the constitutive high-phosphorylation state, AMPK phosphorylates S440 to hyperpolarize gating and reduce firing, and SUMOylation occurs at K470 with single-subunit graded effects.\",\n      \"evidence\": \"In vitro kinase assays, phosphospecific antibodies, MS, mutagenesis, and single-channel recordings in neurons\",\n      \"pmids\": [\"21712386\", \"22006306\", \"21518833\", \"22056818\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Integration of multiple kinase inputs in vivo not modeled\", \"Upstream activation of CDK5/AMPK pools on Kv2.1 unclear\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstrated clusters function as exocytic insertion platforms for membrane proteins and that oxidative Cys73 oligomerization blocks endocytosis to drive raft disruption and c-Src/JNK pro-apoptotic signaling.\",\n      \"evidence\": \"TIRF-FRAP and quantum-dot trafficking imaging; biochemical oligomerization, dynamin/cholesterol manipulation, and kinase inhibition with C73A control\",\n      \"pmids\": [\"22648171\", \"23275378\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the oxidant sensor coupling to Cys73 in vivo not defined\", \"How clusters template exocytosis mechanistically unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined the apoptotic insertion cascade: oxidant-evoked Ca2+/CaMKII modulates the syntaxin\\u2013Kv2.1 interaction to drive SNARE-dependent surface insertion and the lethal K+ surge.\",\n      \"evidence\": \"CaMKII inhibition, Ca2+ imaging, syntaxin co-IP, electrophysiology, and viability assays\",\n      \"pmids\": [\"23918396\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"SNARE machinery components beyond syntaxin not fully mapped\", \"Link to physiological injury triggers indirect\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"First identified KCNB1 as a human disease gene, with de novo missense mutations causing epileptic encephalopathy through loss of ion selectivity and a gained depolarizing cation conductance, and localized Kv2.1 clusters adjacent to RyR cisternae in striatal neurons.\",\n      \"evidence\": \"Exome sequencing with heterologous functional electrophysiology; EM-immunogold and phosphospecific labeling in MSNs\",\n      \"pmids\": [\"25164438\", \"24962901\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether conducting or non-conducting defects dominate disease not resolved\", \"In vivo neuronal consequences of mutations not yet tested\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Resolved distinct disease mechanisms (loss of selectivity, voltage-sensor disruption, dominant-negative pore mutations), defined dual Golgi-dependent/independent trafficking to soma vs AIS, and showed the clustering role\\u2014not conductance\\u2014drives beta-cell granule recruitment.\",\n      \"evidence\": \"Heterologous and endogenous-neuron electrophysiology of patient variants; FRAP with Golgi-pathway dissection; clustering-deficient \\u0394C318 mutant with TIRF granule imaging\",\n      \"pmids\": [\"26503721\", \"26477325\", \"29042434\", \"28607108\", \"26442584\", \"29379118\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"AIS trafficking motif's binding partners unknown\", \"Functional significance of M-phase clustering (Medium) not established\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Established that pro-apoptotic Y124 and S800 phosphorylation are co-dependent and that beta-cell incretin/leptin and CXCR4 signaling route through Kv2.1 modification to set survival vs death outcomes.\",\n      \"evidence\": \"Phosphospecific co-IP and combinatorial mutagenesis (Y124/S800/C73); incretin PKA/MSK-1/CBP and leptin AMPK/PKA pathway dissection; CXCR4-p38-S800A causal mutant\",\n      \"pmids\": [\"26115091\", \"21818121\", \"26453299\", \"23223293\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Several pathway steps are Medium-confidence single-lab\", \"Spatial coordination of Src and p38 on the channel not visualized\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Showed clustered Kv2.1 builds ER\\u2013PM junctions that scaffold LTCC\\u2013RyR Ca2+ triads and unexpectedly enhance LTCC opening at polarized potentials, defining a non-conducting Ca2+-signaling organizer role.\",\n      \"evidence\": \"BioID proximity proteomics, co-localization, Ca2+ spark imaging, LTCC single-channel recording, and Kv2.1 KO/KD\",\n      \"pmids\": [\"31663850\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which clusters enhance LTCC opening unresolved\", \"Direct vs indirect Kv2.1\\u2013LTCC contacts not defined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified VAPA as the ER tether mediating Kv2.1-dependent junctions, showed a peptide disrupting Kv2.1\\u2013VAPA is neuroprotective in ischemia, and dissected a sex-dependent structural Kv2.1 role clustering CaV1.2 in arterial myocytes; a DEE variant fails to induce junctions dominant-negatively.\",\n      \"evidence\": \"TAT-peptide disruption with co-IP and in vivo ischemia-reperfusion; KO with TIRF CaV1.2 imaging and sex stratification; HEK ER-PM junction assay of G379R\",\n      \"pmids\": [\"32937450\", \"32015129\", \"33132203\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"G379R junction defect is Medium-confidence heterologous only\", \"Whether VAPA is the sole ER tether across cell types unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Cemented the essential non-conducting roles: VAP-dependent Kv2.1 enables activity-dependent ER Ca2+ uptake and synaptic vesicle fusion, and KCNB1 forms integrin \\u03b15\\u03b25 complexes required for neocortical migration, with a DEE knock-in mouse rescued by FAK activation.\",\n      \"evidence\": \"shRNA knockdown with compartmental Ca2+ and SV-fusion imaging; KCNB1 null and R312H knock-in mice with co-IP and angiotensin-II FAK rescue\",\n      \"pmids\": [\"35862456\", \"36207442\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How integrin-FAK signaling drives migration mechanistically incomplete\", \"Relative contribution of conducting vs structural roles to brain development not quantified\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the dozens of phosphorylation, SUMOylation, oxidation, and lipid inputs are integrated in space and time to switch Kv2.1 between conducting, junction-organizing, and pro-apoptotic states remains unresolved, as does a unified structural model of the cluster and its ER tether.\",\n      \"evidence\": null,\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No high-resolution structure of the clustered channel\\u2013VAPA junction\", \"Quantitative model integrating multisite modifications absent\", \"Causal hierarchy of conducting vs structural deficits in human disease unsettled\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 6, 27, 29]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 4, 6]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [7, 16, 38, 39]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [7, 37, 48]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [5, 6, 14, 18]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [7, 37, 38]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [5, 14, 15]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 8, 21]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [2, 22, 35, 36]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [27, 28, 29, 48, 51]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [48]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [16, 45, 52]}\n    ],\n    \"complexes\": [\n      \"Kv2.1 homotetramer / Kv2.1-Kv6.1 heterotetramer\",\n      \"Kv2.1-VAPA ER-PM junction complex\",\n      \"integrin \\u03b15\\u03b25-K+ channel complex (IKC)\",\n      \"Kv2.1-LTCC-RyR Ca2+ signaling triad\"\n    ],\n    \"partners\": [\n      \"VAPA\",\n      \"SNAP25\",\n      \"STX1A\",\n      \"AMIGO1\",\n      \"KCNE3\",\n      \"KCNG1\",\n      \"ITGA5\",\n      \"PTK2\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":9,"faith_total":9,"faith_pct":100.0}}