{"gene":"KCND2","run_date":"2026-04-28T18:06:54","timeline":{"discoveries":[{"year":1991,"finding":"Kv4.2 (RK5) encodes a rapidly inactivating A-type potassium current when expressed in Xenopus oocytes, with kinetics consistent with contribution to cardiac Ito current (activation rise time ~2.8 ms, midpoint ~-1 mV, rapid inactivation with tau 15 and 60 ms, sensitive to 4-AP but not TEA or dendrotoxins).","method":"Xenopus oocyte expression with two-electrode voltage clamp","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 — reconstitution in heterologous system with full biophysical characterization","pmids":["1722463"],"is_preprint":false},{"year":1996,"finding":"4-aminopyridine blocks Kv4.2 exclusively from the closed (resting) state via an intracellular binding site, and channel inactivation and 4-AP binding are mutually exclusive, indicating that the 4-AP binding site is near cytoplasmic domains involved in inactivation.","method":"Two-electrode voltage clamp in Xenopus oocytes with pharmacological analysis","journal":"The Journal of pharmacology and experimental therapeutics","confidence":"High","confidence_rationale":"Tier 1 — rigorous in vitro biophysical dissection with state-dependent analysis","pmids":["8930194"],"is_preprint":false},{"year":1997,"finding":"Kv4.2 is localized to the somatodendritic membrane of neurons and is concentrated postsynaptically at synaptic contacts in rat supraoptic nucleus, as demonstrated by immunoelectron microscopy.","method":"Confocal and immunoelectron microscopy","journal":"Neuroscience","confidence":"High","confidence_rationale":"Tier 2 — direct ultrastructural localization with quantitative immunogold","pmids":["9070739"],"is_preprint":false},{"year":1997,"finding":"A truncated dominant-negative Kv4.2 construct (Kv4.2ST) suppresses A-type currents in cerebellar granule neurons and Ito in ventricular myocytes when delivered by adenoviral gene transfer, establishing that Kv4 family subunits are the primary contributors to these currents.","method":"Dominant-negative adenoviral overexpression in neurons and cardiac myocytes with patch-clamp recording","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — clean loss-of-function with specific electrophysiological readout in native cells","pmids":["9395498"],"is_preprint":false},{"year":1997,"finding":"Kv4.2 electrophysiological and pharmacological properties (including flecainide sensitivity and rapid recovery from inactivation) closely match native cardiac Ito in rat myocytes, supporting Kv4.2 as a major molecular substrate of cardiac transient outward current.","method":"Stable expression in mouse L-cells, whole-cell voltage clamp, pharmacological profiling","journal":"Cardiovascular research","confidence":"High","confidence_rationale":"Tier 1 — direct comparison of recombinant and native currents with pharmacological validation","pmids":["9093524"],"is_preprint":false},{"year":1998,"finding":"Kv4.2 mRNA is co-expressed with Kv4.1 in neostriatal cholinergic interneurons and Kv4.2 protein is present in somatodendritic membranes; A-type current recovery kinetics match Kv4.2/Kv4.1 channels rather than Kv1.4, indicating Kv4.2-containing channels underlie somatodendritic A-current in these neurons.","method":"Single-cell RT-PCR, immunocytochemistry, whole-cell voltage clamp with kinetic analysis","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (electrophysiology, immunocytochemistry, single-cell PCR)","pmids":["9547221"],"is_preprint":false},{"year":2000,"finding":"Kv4.2 mRNA abundance is linearly correlated with A-type K+ current amplitude across four neuron types (neostriatal medium spiny neurons, cholinergic interneurons, globus pallidus neurons, basal forebrain cholinergic neurons), establishing Kv4.2 as the major determinant of somatodendritic A-current in these neurons.","method":"Quantitative single-cell RT-PCR combined with voltage-clamp analysis","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — quantitative correlation validated across multiple cell types with two independent methods","pmids":["10632587"],"is_preprint":false},{"year":2000,"finding":"ERK2 directly phosphorylates Kv4.2 at three C-terminal sites: Thr602, Thr607, and Ser616, as identified by in vitro kinase assay and phosphopeptide mapping; ERK-phosphorylated Kv4.2 was confirmed in rat hippocampus using phospho-site-selective antibodies.","method":"In vitro kinase assay with GST fusion proteins, phosphopeptide mapping, phospho-selective antibodies in native tissue","journal":"Journal of neurochemistry","confidence":"High","confidence_rationale":"Tier 1 — direct in vitro phosphorylation with site identification and validation in vivo","pmids":["11080179"],"is_preprint":false},{"year":2000,"finding":"PKA directly phosphorylates Kv4.2 at Thr38 (N-terminus) and Ser552 (C-terminus), identified by in vitro kinase assay, phosphopeptide mapping, and confirmed in intact COS-7 cells and hippocampal CA1.","method":"In vitro kinase assay with GST-fusion proteins, phosphopeptide mapping, phospho-selective antisera, intact cell PKA stimulation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro with site mutagenesis and in vivo validation","pmids":["10681507"],"is_preprint":false},{"year":2000,"finding":"Kv4.2 interacts directly with the actin-binding protein filamin via yeast two-hybrid and co-immunoprecipitation from brain; this interaction localizes Kv4.2 to filopodial roots and increases whole-cell current density ~2.7-fold in filamin-positive vs. filamin-negative cells.","method":"Yeast two-hybrid, co-immunoprecipitation from brain and in vitro, immunocytochemistry, whole-cell patch clamp in filamin+/- cells","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP from brain plus functional consequence in defined cell system","pmids":["11102480"],"is_preprint":false},{"year":2000,"finding":"Kv4.2 localizes predominantly to the transverse-axial tubular system (T-tubules) in rat ventricular myocytes, as demonstrated by immunofluorescence and immunogold electron microscopy.","method":"Immunofluorescence, immunoelectron microscopy with FluoroNanogold","journal":"Journal of molecular and cellular cardiology","confidence":"High","confidence_rationale":"Tier 2 — direct ultrastructural localization with correlative approaches","pmids":["10860776"],"is_preprint":false},{"year":2001,"finding":"Kv4.2 channel inactivation occurs from both open and pre-open closed states; N-terminal deletion (residues 2-40) slows open-state inactivation components without affecting closed-state inactivation or recovery, indicating the N-terminus contributes to open-state but not closed-state inactivation.","method":"Whole-cell patch clamp in HEK293 cells with N-terminal deletion mutants, kinetic modeling","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis with detailed kinetic analysis and allosteric modeling","pmids":["11507158"],"is_preprint":false},{"year":2001,"finding":"MiRP1 (KCNE2) co-immunoprecipitates with Kv4.2 and modulates its gating (slows activation and inactivation, shifts voltage dependence positive) in a dose-dependent manner in Xenopus oocytes, suggesting MiRP1 serves as a regulatory beta subunit of cardiac Ito channels.","method":"Xenopus oocyte expression, two-electrode voltage clamp, co-immunoprecipitation","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 — co-IP combined with dose-dependent functional analysis","pmids":["11375270"],"is_preprint":false},{"year":2002,"finding":"PSD-95 interacts with Kv4.2 via the C-terminal VSAL motif; co-expression of PSD-95 increases surface expression of Kv4.2 and causes its clustering; palmitoylation of PSD-95 is required for these effects.","method":"Co-immunoprecipitation in mammalian cells, mutation analysis of VSAL motif, deconvolution microscopy, surface biotinylation assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods with defined binding motif and functional consequence","pmids":["11923279"],"is_preprint":false},{"year":2002,"finding":"PKA phosphorylation of Kv4.2 alpha-subunit is necessary but not sufficient for channel modulation; association with the ancillary subunit KChIP3 is additionally required for PKA-dependent regulation of Kv4.2 channel properties.","method":"Electrophysiology in Xenopus oocytes, PKA stimulation, KChIP3 co-expression, site-directed mutagenesis","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1 — epistasis-based functional analysis with mutagenesis showing supramolecular requirement","pmids":["12451113"],"is_preprint":false},{"year":2003,"finding":"KChIP1-3 co-expression with Kv4.2 releases ER retention, promotes surface trafficking, increases steady-state expression, alters phosphorylation, and changes detergent solubility; these effects occur through masking of an N-terminal hydrophobic domain of Kv4.2. KChIP4a does not exert these effects and negatively modulates other KChIPs.","method":"Co-expression in heterologous cells, immunocytochemistry, surface biotinylation, biochemical fractionation, phosphorylation analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal biochemical methods with defined N-terminal mechanism","pmids":["12829703"],"is_preprint":false},{"year":2003,"finding":"Kv4.2 and KChIP2 form octameric complexes with 4:4 stoichiometry (4 Kv4.2 and 4 KChIP2 subunits), as determined by purification of native Ito complexes and direct amino acid analysis.","method":"Protein purification, electron microscopy, amino acid analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — biochemical purification with direct stoichiometric determination","pmids":["14623880"],"is_preprint":false},{"year":2003,"finding":"PSD-95 recruits Kv1.4, but not Kv4.2, to lipid rafts via palmitoylation-dependent mechanism; a fraction of native Kv4.2 is found in lipid rafts in rat brain and hippocampal neurons via an alternative PSD-95-independent mechanism.","method":"Lipid raft fractionation, lipid raft patching, immunostaining, co-expression in heterologous cells, VSAL deletion mutants","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 3 — single lab with biochemical fractionation and cell imaging","pmids":["14559911"],"is_preprint":false},{"year":2004,"finding":"CaMKII directly phosphorylates Kv4.2 at Ser438 and Ser459 in vitro; CaMKII phosphorylation does not alter channel biophysics but increases Kv4.2 protein levels and surface expression, leading to increased A-current amplitude and decreased neuronal excitability in hippocampal neurons.","method":"In vitro kinase assay, site-directed mutagenesis, Xenopus oocyte expression, CaMKII overexpression in hippocampal neurons, whole-cell patch clamp","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1 — in vitro kinase assay with mutagenesis plus functional validation in neurons","pmids":["15071113"],"is_preprint":false},{"year":2004,"finding":"DPP10 co-immunoprecipitates with Kv4.2, enhances surface expression ~5-fold without changing protein levels, and remodels gating kinetics by accelerating inactivation and recovery and shifting conductance-voltage relationship ~19 mV hyperpolarized; the cytoplasmic N-terminal domain of DPP10 determines inactivation acceleration.","method":"Co-immunoprecipitation from Xenopus oocytes, two-electrode voltage clamp, domain deletion analysis","journal":"Biophysical journal","confidence":"High","confidence_rationale":"Tier 2 — co-IP plus detailed biophysical characterization with domain mapping","pmids":["15454437"],"is_preprint":false},{"year":2005,"finding":"Direct ERK/MAPK phosphorylation of Kv4.2 at Thr607 mimics ERK-induced rightward shift in activation and current reduction; this effect requires KChIP3 co-expression. Ser616 phosphorylation produces the opposite gating effect.","method":"Site-directed mutagenesis (phosphomimetic T607D, S616D), Xenopus oocyte electrophysiology, co-expression with KChIP3","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 1 — phosphomimetic mutagenesis with functional electrophysiological validation","pmids":["16251476"],"is_preprint":false},{"year":2005,"finding":"Kv4.2, KChIP3, and DPP10 form ternary macromolecular complexes in rat brain and heterologous cells (confirmed by co-immunoprecipitation); ternary complexes show greatly accelerated recovery from inactivation (~18-26 ms) that matches native ISA, distinct from binary Kv4.2+KChIP3 or Kv4.2+DPP10 channels.","method":"Co-immunoprecipitation from rat brain and oocytes, two-electrode voltage clamp in oocytes and CHO cells","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP from native tissue plus functional reconstitution matching native current","pmids":["16123112"],"is_preprint":false},{"year":2005,"finding":"Kv4.2 is transported to dendrites by the kinesin motor Kif17; dominant-negative Kif17 inhibits dendritic localization of endogenous and introduced Kv4.2, while Kv4.2 and Kif17 co-immunoprecipitate from brain and co-localize in cortical neuron dendrites. The interaction occurs through the extreme C-terminus of Kv4.2.","method":"Dominant-negative kinesin expression, co-immunoprecipitation from brain and COS cells, immunofluorescence co-localization in cortical neurons","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — co-IP from brain tissue plus loss-of-function with defined interaction domain","pmids":["16257958"],"is_preprint":false},{"year":2005,"finding":"Targeted deletion of Kv4.2 eliminates fast transient outward current Ito,f in ventricular myocytes; Kv1.4 protein and Ito,s are upregulated compensatorily, while KChIP2 expression is markedly reduced, demonstrating that Kv4.2 is essential for Ito,f generation and that KChIP2 stability depends on Kv4.2.","method":"Kv4.2 knockout mice, voltage-clamp recordings from ventricular myocytes, Western blot","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 — clean genetic KO with defined electrophysiological and molecular phenotype","pmids":["16293790"],"is_preprint":false},{"year":2005,"finding":"KChIP N-terminus residues 11-23 form a primary interaction site with Kv4.2, the T1 domain provides a secondary site, and C-terminal deletions of Kv4.2 also reduce KChIP binding and functional modulation, revealing a C-terminal interaction site.","method":"Lysine-scanning and structure-based mutagenesis of Kv4.2, co-immunoprecipitation, whole-cell patch clamp in mammalian cells","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 1 — systematic mutagenesis defining structural determinants of interaction with parallel biochemical and functional validation","pmids":["16096338"],"is_preprint":false},{"year":2006,"finding":"GRK2 phosphorylates DREAM/KChIP3 at Ser95; the phosphomimetic S95D mutation blocks DREAM-mediated membrane expression of Kv4.2 without affecting channel tetramerization; calcineurin dephosphorylates GRK2-phosphorylated DREAM and its inhibition also blocks Kv4.2 trafficking, establishing a GRK2/calcineurin-dependent regulation of Kv4.2 surface expression via KChIP3.","method":"In vitro kinase assay, site-directed mutagenesis (S95D), calcineurin inhibitor treatment, cell surface expression assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro kinase identification with phosphomimetic mutagenesis and functional surface expression consequence","pmids":["17102134"],"is_preprint":false},{"year":2006,"finding":"Deletion of Kv4.2 eliminates dendritic A-type K+ current in CA1 pyramidal neurons nearly completely, increases backpropagating action potential amplitude and Ca2+ influx, and lowers the threshold for LTP induction with theta burst pairing, establishing Kv4.2 as the molecular substrate of dendritic A-current that regulates synaptic plasticity.","method":"Kv4.2 knockout mice, dendritic patch-clamp recordings, calcium imaging, LTP induction","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — clean genetic KO with multiple electrophysiological and functional phenotypic readouts","pmids":["17122039"],"is_preprint":false},{"year":2006,"finding":"In Kv4.2 knockout mice, KChIP expression is regionally and cell-specifically reduced in proportion to the normal Kv4.2 expression level, demonstrating reciprocal Kv4.2-dependent stabilization of KChIP auxiliary subunits.","method":"Immunohistochemistry in Kv4.2 KO vs. wild-type brains","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — genetic model with systematic protein expression analysis across brain regions","pmids":["17122038"],"is_preprint":false},{"year":2007,"finding":"Kv4.2 undergoes activity-dependent internalization in hippocampal spines and dendrites upon glutamate receptor stimulation; this internalization is clathrin-mediated, requires NMDA receptor activation and Ca2+ influx. LTP induction causes synaptic GluR1-AMPAR insertion concurrent with Kv4.2 internalization.","method":"Live imaging of EGFP-Kv4.2 in hippocampal neurons, electrophysiology (mEPSC recordings), LTP induction in slice cultures","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 — live imaging plus electrophysiology in neurons with defined mechanistic requirements","pmids":["17582333"],"is_preprint":false},{"year":2007,"finding":"SAP97 interacts with Kv4.2 via its PDZ domains and the intact C-terminus of Kv4.2; SAP97 directs Kv4.2 to dendritic spines (PSD fraction); CaMKII-dependent phosphorylation of SAP97 regulates this Kv4.2 targeting to spines.","method":"Co-immunoprecipitation, subcellular fractionation, lentiviral RNAi of SAP97, pharmacological SAP97 translocation in hippocampal neurons","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — co-IP, fractionation, and RNAi with functional localization consequence","pmids":["17635915"],"is_preprint":false},{"year":2007,"finding":"mGlu5 activation leads to ERK-mediated phosphorylation of Kv4.2 at Ser616, inhibiting A-type K+ currents and increasing dorsal horn neuronal excitability; Kv4.2 knockout mice show impaired nociceptive behavior after spinal group I mGluR activation, establishing Kv4.2 as a downstream effector of mGlu5-ERK signaling in nociception.","method":"Electrophysiology in dorsal horn neurons, site-directed mutagenesis of S616, Kv4.2 KO mice, behavioral nociception assays","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — mutagenesis of phosphorylation site plus KO behavioral validation","pmids":["18045912"],"is_preprint":false},{"year":2008,"finding":"PKA activation induces Kv4.2 internalization from dendritic spines; PKA inhibition prevents AMPA-induced internalization; a point mutation at the C-terminal PKA phosphorylation site S552A prevents AMPA-induced internalization of Kv4.2, establishing S552 as required for PKA-dependent activity-driven trafficking.","method":"Live imaging in hippocampal neurons, pharmacological PKA activation/inhibition, point mutation S552A","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — live imaging with site-specific mutagenesis demonstrating mechanistic requirement","pmids":["18650329"],"is_preprint":false},{"year":2008,"finding":"Kv4.2 deletion eliminates IA in cortical pyramidal neurons, accompanied by loss of KChIP3 protein (degraded without Kv4.2) and upregulation of IK and Iss densities (electrical remodeling), but without change in action potential waveform.","method":"Kv4.2 KO mice, whole-cell voltage clamp of cortical neurons, Western blot","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 2 — clean genetic KO with electrophysiological and molecular readouts","pmids":["18187474"],"is_preprint":false},{"year":2008,"finding":"Kv4.2 ISA channels are complexes of four Kv4.2 and four DPP6 subunits (4:4 stoichiometry), established by tandem-linked subunit biophysics and direct amino acid analysis of purified complexes.","method":"Tandem-linked subunit expression, electrophysiology, protein purification and amino acid analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstitution with direct biochemical stoichiometric measurement","pmids":["18364354"],"is_preprint":false},{"year":2008,"finding":"Ternary Kv4.2+KChIP1+DPPX-S channels reconstitute the voltage-dependent slowing of inactivation rate (characteristic of native ISA in cerebellar granule neurons) through a mechanism of preferential closed-state inactivation and weakly voltage-dependent opening, as shown by quantitative kinetic modeling.","method":"Whole-cell patch clamp in heterologous cells, native neuron recordings, global kinetic modeling","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 1 — reconstitution in heterologous cells matching native channel properties with kinetic modeling","pmids":["18276729"],"is_preprint":false},{"year":2008,"finding":"Gating charge (Q) immobilization in Kv4.2 occurs over hyperpolarized voltages that do not open channels, with kinetics and voltage dependence paralleling closed-state inactivation; Q-immobilization and closed-state inactivation are two manifestations of the same process involving desensitization of voltage sensors.","method":"Gating current measurements in CTX-blocked Kv4.2 channels in Xenopus oocytes, coupled state modeling","journal":"The Journal of general physiology","confidence":"High","confidence_rationale":"Tier 1 — direct gating current measurement with mechanistic modeling","pmids":["18299396"],"is_preprint":false},{"year":2009,"finding":"PKC directly phosphorylates Kv4.2 at Ser447 and Ser537 on the C-terminus; mutation of both sites to alanine increases surface expression; PKC phosphorylation at Ser537 (within an ERK docking domain) enhances subsequent ERK phosphorylation of Kv4.2, establishing Kv4.2 as a locus for PKC-ERK cross-talk.","method":"In vitro kinase assay with GST fusion proteins, phospho-site antibody, surface biotinylation, electrophysiology, sequential kinase assay","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 — in vitro kinase assay with site identification, mutagenesis, and cross-kinase signaling validation","pmids":["18795890"],"is_preprint":false},{"year":2009,"finding":"S4-S5 linker and S6 residues Glu323 and Val404 are critical for both voltage-dependent gate opening and closed-state inactivation in Kv4.2 channels; double-mutant cycle analysis and redox modulation of cysteine double mutants confirm dynamic coupling between voltage sensor and cytoplasmic gate underlies closed-state inactivation.","method":"Alanine-scanning mutagenesis, double-mutant cycle analysis, cysteine-substitution redox modulation, two-electrode voltage clamp in Xenopus oocytes","journal":"The Journal of general physiology","confidence":"High","confidence_rationale":"Tier 1 — systematic mutagenesis with thermodynamic cycle analysis and chemical crosslinking","pmids":["19171772"],"is_preprint":false},{"year":2009,"finding":"DPP6-S is necessary and sufficient to increase the unitary conductance of neuronal Kv4.2 channels from ~4 pS to ~7.5 pS (matching native CGN channels); CGN Kv4 channels from dpp6 KO mice show reduced conductance; two N-terminal acidic residues of DPP6-S mediate this effect via electrostatic interactions.","method":"Single-channel recordings from heterologous cells and CGNs, dpp6 KO mice, charge neutralization mutagenesis of DPP6-S","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1 — single-channel reconstitution with KO validation and mutagenesis of mechanism","pmids":["19279261"],"is_preprint":false},{"year":2010,"finding":"KChIP4a requires PKA phosphorylation of Kv4.2 at S552 to produce enhanced stabilization and membrane expression of Kv4.2, while other KChIP isoforms (KChIP1-3) enhance surface expression independently of S552 phosphorylation; A-kinase anchoring proteins (AKAPs) bind Kv4.2, enabling local PKA signaling.","method":"Co-expression in heterologous cells, surface biotinylation, S552A/D mutagenesis, co-immunoprecipitation for AKAP interaction","journal":"Molecular and cellular neurosciences","confidence":"High","confidence_rationale":"Tier 2 — mutagenesis with surface expression assay and new AKAP interaction identification","pmids":["20045463"],"is_preprint":false},{"year":2010,"finding":"CaV3.1 (T-type calcium channel) associates with the Kv4.2 complex (Kv4.2-KChIP3-DPP10c) and mediates calcium-dependent rightward shift in Kv4.2 inactivation voltage; this regulation is selective for CaV3 isoforms and not observed with CaV1.4, CaV2.1, or CaV2.3.","method":"Co-expression in heterologous cells, electrophysiology measuring inactivation voltage shift","journal":"Channels","confidence":"Medium","confidence_rationale":"Tier 3 — functional co-expression without direct physical interaction confirmation","pmids":["20458163"],"is_preprint":false},{"year":2010,"finding":"NR2B-containing (extrasynaptic) NMDA receptors mediate glutamate-induced reduction of total Kv4.2 protein and Kv4.2 clusters; Ca2+ influx is required; calpain proteolysis underlies Kv4.2 protein reduction, as calpain inhibitors prevent this effect.","method":"Pharmacological dissection with NR2B-selective antagonists and calpain inhibitors, immunocytochemistry, patch-clamp in cultured hippocampal neurons","journal":"Neuroscience","confidence":"High","confidence_rationale":"Tier 2 — defined pharmacological mechanism with multiple inhibitors and imaging","pmids":["19857555"],"is_preprint":false},{"year":2012,"finding":"DPP6 and DPP10 independently stabilize surface Kv4.2 protein without affecting DPP protein levels themselves; KChIP3 addition to DPP10+Kv4.2 further increases total and surface Kv4.2; DPP6/10 expression and localization are independent of Kv4 alpha-subunits.","method":"Heterologous co-expression, surface biotinylation, Kv4.2/Kv4.3 KO mouse brain Western blot, cell surface immunostaining","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — genetic KO validation combined with heterologous reconstitution and biochemical quantification","pmids":["22311982"],"is_preprint":false},{"year":2014,"finding":"A de novo missense mutation V404M (Val404Met) in KCND2 causes significantly slowed Kv4.2 inactivation (dominant effect) and impairs closed-state inactivation in the presence of auxiliary subunits, consistent with gain-of-function causing epilepsy and autism in affected twins.","method":"Whole-exome sequencing, heterologous expression electrophysiology of WT and mutant Kv4.2 in Xenopus oocytes, co-expression with auxiliary subunits","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 1 — functional characterization of disease mutation with auxiliary subunit co-expression","pmids":["24501278"],"is_preprint":false},{"year":2015,"finding":"H2S inhibits Ito by targeting the Cys320/Cys529 disulfide bridge in Kv4.2; mutation of either cysteine blocks H2S-mediated inhibition; H2S breaks an existing disulfide bond without modifying single free cysteines.","method":"Mutagenesis of Cys320 and Cys529, whole-cell patch clamp in cardiomyocytes, H2S pharmacology","journal":"Antioxidants & redox signaling","confidence":"High","confidence_rationale":"Tier 1 — site-specific mutagenesis defining the molecular target of H2S modulation","pmids":["25756524"],"is_preprint":false},{"year":2016,"finding":"miR-324-5p directly binds KCND2 mRNA and inhibits Kv4.2 protein expression; antagonizing miR-324-5p is neuroprotective, seizure-suppressive, and blocks kainic-acid-induced Kv4.2 reduction in vitro and in vivo; these effects are absent in Kcnd2 KO mice, confirming specificity.","method":"RNA-induced silencing complex pulldown, miRNA mimic/antagonist transfection, luciferase reporter assay, in vivo miRNA antagonist injection, Kcnd2 KO mice","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — direct RISC pulldown, luciferase validation, and KO confirmation","pmids":["27681419"],"is_preprint":false},{"year":2018,"finding":"The autism/epilepsy mutation V404M (Kv4.2) enhances closed-state inactivation (increases inactivated state stability) while dramatically impairing open-state inactivation by slowing channel closure; larger methionine volume is a key mechanistic factor; this reveals that channel closure is required for closed-state inactivation.","method":"Whole-cell patch clamp of WT and V404M Kv4.2 in heterologous cells, detailed kinetic analysis of CSI and OSI","journal":"PNAS","confidence":"High","confidence_rationale":"Tier 1 — detailed mechanistic mutagenesis with biophysical dissection of inactivation states","pmids":["29581270"],"is_preprint":false},{"year":2018,"finding":"A gain-of-function mutation S447R in KCND2 causes nocturnal paroxysmal atrial fibrillation; S447 is a PKC phosphorylation site that normally attenuates Kv4.2 membrane expression; the S447R mutant shows impaired response to PKC and augmented membrane expression; the mutation also exerts gain-of-function in Kv4.2-Kv4.3 heterotetramers.","method":"Xenopus oocyte electrophysiology, Kv4.2-Kv4.3 hybrid channel expression, linkage analysis, whole-exome sequencing","journal":"Circulation. Genomic and precision medicine","confidence":"High","confidence_rationale":"Tier 2 — functional characterization of disease mutation with hybrid channel experiments and defined PKC site mechanism","pmids":["30571183"],"is_preprint":false},{"year":2020,"finding":"Activity-induced ERK phosphorylation of Kv4.2 at pThr607-Pro triggers Pin1 binding and isomerization of Kv4.2, causing dissociation of the Kv4.2-DPP6 complex; Kv4.2-TA (T607A knock-in) mice show altered Kv4.2-DPP6 interaction, increased A-type K+ current, reduced hippocampal neuronal excitability, and improved reversal learning.","method":"Kv4.2-T607A knock-in mouse model, co-immunoprecipitation for Pin1 and DPP6 interaction, whole-cell patch clamp in CA1 neurons, behavioral testing","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — knock-in mouse with defined molecular mechanism and multiple orthogonal functional readouts","pmids":["32218435"],"is_preprint":false},{"year":2020,"finding":"GSK3β directly phosphorylates Kv4.2 at Ser616 in nucleus accumbens medium spiny neurons, inhibiting A-type K+ channel function and driving tLTP changes in a chronic stress depression model; GSK3β knockdown or Kv4.2-S616 phosphorylation blockade prevents maladaptive plasticity.","method":"In vivo AAV-RNAi knockdown of GSK3β, electrophysiology, immunohistochemistry, biochemistry, pharmacological Kv4.2 channel inhibition in mouse NAc","journal":"PNAS","confidence":"High","confidence_rationale":"Tier 2 — in vivo genetic silencing with multiple orthogonal electrophysiological and biochemical readouts","pmids":["32209671"],"is_preprint":false},{"year":2006,"finding":"DPPX-S (DPP6) remodels gating charge dynamics in Kv4.2 channels by causing a -26 mV parallel shift in the Q-V relationship and accelerating both outward and return gating charge movements; this effect is absent in Shaker B channels, indicating DPPX-S specifically destabilizes resting and intermediate activation states in Kv4.2.","method":"Gating current measurements in CTX-blocked Kv4.2 channels in Xenopus oocytes, co-expression with DPPX-S","journal":"The Journal of general physiology","confidence":"High","confidence_rationale":"Tier 1 — direct gating current measurement with appropriate controls","pmids":["17130523"],"is_preprint":false},{"year":1999,"finding":"Kvbeta1.2 co-expression with Kv4.2 in HEK293 cells confers oxygen/redox sensitivity to Kv4.2 channels (but not to Shaker), enabling inhibition by hypoxia, DTT, and DTDP; the O2 sensitivity is membrane-delimited and involves a hemoprotein O2 sensor.","method":"Heterologous co-expression in HEK293 cells, whole-cell patch clamp under hypoxia and redox agents, excised patch recordings","journal":"The Journal of general physiology","confidence":"High","confidence_rationale":"Tier 2 — defined co-expression requirement with cell-free patch confirmation of membrane-delimited mechanism","pmids":["10352037"],"is_preprint":false}],"current_model":"Kv4.2 (KCND2) is the principal pore-forming alpha-subunit of somatodendritic A-type (ISA/Ito) potassium channels in neurons and cardiac myocytes; it forms octameric macromolecular complexes (4:4 stoichiometry) with cytoplasmic KChIP auxiliary subunits and transmembrane DPP6/DPP10 subunits, which together promote ER exit, surface trafficking, and confer native gating kinetics (including rapid recovery and voltage-dependent inactivation); channel availability is dynamically regulated by phosphorylation at multiple sites (ERK at T602/T607/S616, PKA at T38/S552, CaMKII at S438/S459, PKC at S447/S537), by activity-dependent clathrin-mediated internalization requiring NMDA-R activation, Ca2+, and PKA-S552 phosphorylation, by Pin1-mediated isomerization at pT607-Pro that dissociates the DPP6 complex, and by miRNA-mediated (miR-324-5p) translational silencing, with dendritic targeting dependent on Kif17 motor and SAP97/PSD-95 scaffolding interactions."},"narrative":{"teleology":[{"year":1991,"claim":"Establishing the basic identity of KCND2 as an A-type K+ channel gene resolved which molecular entity produces rapidly inactivating, 4-AP-sensitive currents with cardiac Ito-like properties.","evidence":"Heterologous expression in Xenopus oocytes with two-electrode voltage clamp","pmids":["1722463"],"confidence":"High","gaps":["Native subunit composition unknown","Physiological role in neurons vs. heart not yet distinguished","Inactivation mechanism (open vs. closed state) not resolved"]},{"year":1997,"claim":"Demonstration that Kv4.2 localizes to somatodendritic membranes and that dominant-negative Kv4.2 suppresses neuronal A-current and cardiac Ito established Kv4.2 as the molecular basis of these native currents in both tissues.","evidence":"Immunoelectron microscopy in neurons, adenoviral dominant-negative expression with patch-clamp in cerebellar granule neurons and ventricular myocytes","pmids":["9070739","9395498","9093524"],"confidence":"High","gaps":["Auxiliary subunits not yet identified","Phosphorylation-dependent regulation unknown","Trafficking mechanisms undefined"]},{"year":2000,"claim":"Identification of ERK (T602/T607/S616) and PKA (T38/S552) phosphorylation sites, the filamin interaction, and quantitative mRNA–current correlation across neuron types established that Kv4.2 is a convergent signaling target whose expression level directly determines A-current amplitude.","evidence":"In vitro kinase assays, phosphopeptide mapping, phospho-selective antibodies, yeast two-hybrid, co-IP from brain, quantitative single-cell RT-PCR with voltage clamp","pmids":["11080179","10681507","11102480","10632587"],"confidence":"High","gaps":["Functional consequences of each phosphorylation site on channel gating not yet resolved","Auxiliary subunit requirement for kinase modulation unknown","ER-to-surface trafficking mechanism undefined"]},{"year":2001,"claim":"Distinguishing N-terminal-dependent open-state inactivation from a separate closed-state inactivation pathway, and identifying KCNE2/MiRP1 as a modulatory β-subunit, revealed that Kv4.2 uses dual inactivation mechanisms and engages multiple types of auxiliary subunits.","evidence":"N-terminal deletion mutagenesis with kinetic modeling in HEK293 cells; co-IP and dose-dependent gating modulation by KCNE2 in oocytes","pmids":["11507158","11375270"],"confidence":"High","gaps":["Structural basis of closed-state inactivation not defined","Relative contribution of KCNE2 vs. other β-subunits in native tissue unclear"]},{"year":2003,"claim":"Discovery that KChIPs form 4:4 octameric complexes with Kv4.2, mask an N-terminal ER-retention signal, and promote surface trafficking resolved how auxiliary subunits control channel biogenesis and established the native channel stoichiometry.","evidence":"Protein purification with amino acid analysis, electron microscopy, surface biotinylation with KChIP1-3 co-expression, N-terminal domain mapping","pmids":["14623880","12829703"],"confidence":"High","gaps":["DPP stoichiometry and ternary complex architecture not yet determined","KChIP4a inhibitory mechanism not fully resolved"]},{"year":2005,"claim":"Reconstitution of ternary Kv4.2–KChIP–DPP complexes and genetic knockout studies demonstrated that DPP6/10 contributes the rapid recovery kinetics of native ISA, that Kv4.2 is essential for cardiac Ito,f, and that KChIP stability depends on Kv4.2 expression.","evidence":"Co-IP from brain, ternary co-expression electrophysiology matching native ISA, Kv4.2 KO mouse cardiac and neuronal recordings, KChIP protein quantification in KO","pmids":["16123112","16293790","16251476"],"confidence":"High","gaps":["DPP6 stoichiometry in ternary complex not directly measured","Mechanism by which DPP accelerates recovery not structurally resolved"]},{"year":2006,"claim":"Kv4.2 KO elimination of dendritic A-current in CA1 neurons—with enhanced back-propagating action potentials, increased Ca2+ influx, and lowered LTP threshold—established Kv4.2 as the molecular gatekeeper of dendritic excitability and synaptic plasticity.","evidence":"Kv4.2 KO mice, dendritic patch-clamp, calcium imaging, theta-burst LTP in hippocampal slices","pmids":["17122039"],"confidence":"High","gaps":["Compensatory mechanisms in KO not fully catalogued","Spine-specific vs. dendritic shaft contributions not separated"]},{"year":2007,"claim":"Discovery of activity-dependent, NMDA-receptor- and clathrin-dependent Kv4.2 internalization from spines during LTP, and SAP97/Kif17-dependent dendritic targeting, revealed that Kv4.2 surface levels are bidirectionally regulated to tune synaptic strength.","evidence":"Live EGFP-Kv4.2 imaging, mEPSC recordings, dominant-negative Kif17, co-IP for SAP97 and Kif17 from brain","pmids":["17582333","17635915","16257958"],"confidence":"High","gaps":["Endocytic adaptor proteins linking Kv4.2 to clathrin not identified","Ubiquitination or degradation fate of internalized channels not determined"]},{"year":2008,"claim":"Identification of PKA-S552 as the required phosphorylation event for activity-driven internalization, determination of 4:4 Kv4.2:DPP6 stoichiometry, and gating-charge immobilization studies linked phosphorylation-controlled trafficking to a defined voltage-sensor desensitization mechanism for closed-state inactivation.","evidence":"S552A mutagenesis with live imaging, tandem-linked subunit electrophysiology and protein purification, gating current measurements in CTX-blocked channels","pmids":["18650329","18364354","18299396"],"confidence":"High","gaps":["Structural rearrangement of voltage sensor during CSI not directly observed","Interplay between PKA-S552 and KChIP/DPP in internalization not dissected"]},{"year":2009,"claim":"PKC phosphorylation sites (S447, S537) were mapped and shown to regulate surface expression and prime ERK phosphorylation, while structure–function analysis of S4-S5 linker and S6 residues defined the electromechanical coupling underlying closed-state inactivation.","evidence":"In vitro kinase assays, sequential kinase cross-talk experiments, alanine-scanning mutagenesis with double-mutant thermodynamic cycles in oocytes, single-channel recordings in DPP6 KO neurons","pmids":["18795890","19171772","19279261"],"confidence":"High","gaps":["Atomic-resolution structure of the inactivated state not available","PKC-ERK cross-talk not validated in native neurons"]},{"year":2014,"claim":"Identification of a de novo V404M mutation causing epilepsy and autism, with gain-of-function slowed inactivation, linked channel gating mechanisms to human neurodevelopmental disease.","evidence":"Whole-exome sequencing in affected twins, heterologous expression electrophysiology of V404M with auxiliary subunits","pmids":["24501278"],"confidence":"High","gaps":["In vivo consequences of V404M in animal models not tested","Genotype–phenotype spectrum of KCND2 variants not established"]},{"year":2018,"claim":"The S447R gain-of-function mutation causing familial atrial fibrillation disrupts PKC-mediated attenuation of Kv4.2 surface expression, and detailed biophysical analysis of V404M revealed that channel closure is prerequisite for closed-state inactivation, unifying gating and disease mechanisms.","evidence":"Linkage analysis and whole-exome sequencing, oocyte electrophysiology with Kv4.2-Kv4.3 heteromers, detailed kinetic dissection of V404M CSI/OSI","pmids":["30571183","29581270"],"confidence":"High","gaps":["Structural basis of V404M-induced gate obstruction not resolved at atomic level","Penetrance and expressivity of KCND2 cardiac variants in larger cohorts unknown"]},{"year":2020,"claim":"Pin1 prolyl isomerase was identified as a signal-dependent disassembly switch for the Kv4.2–DPP6 complex via ERK-phosphorylated T607, and GSK3β was shown to phosphorylate S616 to drive maladaptive plasticity in depression models, revealing kinase-specific channel modulation in behavioral circuits.","evidence":"Kv4.2-T607A knock-in mice with co-IP, electrophysiology, and behavioral testing; AAV-RNAi of GSK3β in nucleus accumbens with electrophysiology and biochemistry","pmids":["32218435","32209671"],"confidence":"High","gaps":["Pin1-dependent complex disassembly not reconstituted in vitro with purified components","How GSK3β accesses Kv4.2 at the membrane is unclear","Whether Pin1 and GSK3β pathways interact on the same channel complex is untested"]},{"year":null,"claim":"High-resolution structural determination of the full Kv4.2–KChIP–DPP ternary complex, the conformational basis of closed-state inactivation, and genotype-phenotype relationships across the expanding spectrum of KCND2 disease variants remain unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No cryo-EM or crystal structure of ternary Kv4.2–KChIP–DPP complex","Mechanism of clathrin adaptor recruitment to internalized Kv4.2 unknown","Full spectrum of KCND2 pathogenic variants and disease mechanisms incomplete"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,3,4,23,26]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[2,10,13,15,28]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[15]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[28,31]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[2,5,6,26]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[7,8,36,48,49]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,3,4,23]}],"complexes":["Kv4.2-KChIP octamer (4:4)","Kv4.2-DPP6 octamer (4:4)","Kv4.2-KChIP-DPP ternary complex"],"partners":["KCNIP2","KCNIP3","DPP6","DPP10","DLG1","DLG4","KIF17","FLNA"],"other_free_text":[]},"mechanistic_narrative":"KCND2 (Kv4.2) is the principal pore-forming α-subunit of rapidly inactivating, somatodendritic A-type potassium channels in neurons and the fast transient outward current (Ito,f) channel in ventricular cardiomyocytes, serving as a major regulator of dendritic excitability, action potential back-propagation, synaptic plasticity, and cardiac repolarization. Kv4.2 assembles into octameric macromolecular complexes with cytoplasmic KChIP (4:4 stoichiometry) and transmembrane DPP6/DPP10 auxiliary subunits, which together promote ER exit, surface trafficking, unitary conductance, and rapid recovery from inactivation that recapitulates native ISA gating [PMID:14623880, PMID:18364354, PMID:16123112, PMID:12829703]. Channel availability is dynamically tuned by phosphorylation at multiple C-terminal sites—ERK (T602/T607/S616), PKA (T38/S552), PKC (S447/S537), CaMKII (S438/S459), and GSK3β (S616)—and by activity-dependent clathrin-mediated internalization requiring NMDA receptor activation and PKA phosphorylation at S552, as well as Pin1-catalyzed prolyl isomerization at pT607 that dissociates the DPP6 complex [PMID:11080179, PMID:10681507, PMID:18650329, PMID:32218435, PMID:32209671]. De novo gain-of-function mutations in KCND2 (V404M, S447R) cause epilepsy with autism spectrum features and familial nocturnal paroxysmal atrial fibrillation, respectively [PMID:24501278, PMID:30571183]."},"prefetch_data":{"uniprot":{"accession":"Q9NZV8","full_name":"A-type voltage-gated potassium channel KCND2","aliases":["Potassium voltage-gated channel subfamily D member 2","Voltage-gated potassium channel subunit Kv4.2"],"length_aa":630,"mass_kda":70.5,"function":"Voltage-gated potassium channel that mediates transmembrane potassium transport in excitable membranes, primarily in the brain. Mediates the major part of the dendritic A-type current I(SA) in brain neurons (By similarity). This current is activated at membrane potentials that are below the threshold for action potentials. It regulates neuronal excitability, prolongs the latency before the first spike in a series of action potentials, regulates the frequency of repetitive action potential firing, shortens the duration of action potentials and regulates the back-propagation of action potentials from the neuronal cell body to the dendrites. Contributes to the regulation of the circadian rhythm of action potential firing in suprachiasmatic nucleus neurons, which regulates the circadian rhythm of locomotor activity (By similarity). Functions downstream of the metabotropic glutamate receptor GRM5 and plays a role in neuronal excitability and in nociception mediated by activation of GRM5 (By similarity). Mediates the transient outward current I(to) in rodent heart left ventricle apex cells, but not in human heart, where this current is mediated by another family member. Forms tetrameric potassium-selective channels through which potassium ions pass in accordance with their electrochemical gradient (PubMed:10551270, PubMed:11507158, PubMed:14623880, PubMed:14695263, PubMed:14980201, PubMed:15454437, PubMed:16934482, PubMed:19171772, PubMed:24501278, PubMed:24811166, PubMed:34552243, PubMed:35597238). The channel alternates between opened and closed conformations in response to the voltage difference across the membrane (PubMed:11507158). Can form functional homotetrameric channels and heterotetrameric channels that contain variable proportions of KCND2 and KCND3; channel properties depend on the type of pore-forming alpha subunits that are part of the channel. In vivo, membranes probably contain a mixture of heteromeric potassium channel complexes. Interaction with specific isoforms of the regulatory subunits KCNIP1, KCNIP2, KCNIP3 or KCNIP4 strongly increases expression at the cell surface and thereby increases channel activity; it modulates the kinetics of channel activation and inactivation, shifts the threshold for channel activation to more negative voltage values, shifts the threshold for inactivation to less negative voltages and accelerates recovery after inactivation (PubMed:14623880, PubMed:14980201, PubMed:15454437, PubMed:19171772, PubMed:24501278, PubMed:24811166). Likewise, interaction with DPP6 or DPP10 promotes expression at the cell membrane and regulates both channel characteristics and activity (By similarity). Upon depolarization, the channel goes from a resting closed state (C state) to an activated but non-conducting state (C* state), from there, the channel may either inactivate (I state) or open (O state) (PubMed:35597238)","subcellular_location":"Cell membrane; Cell projection, dendrite; Synapse; Perikaryon; Postsynaptic cell membrane; Cell projection, dendritic spine; Cell junction","url":"https://www.uniprot.org/uniprotkb/Q9NZV8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KCND2","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/KCND2","total_profiled":1310},"omim":[{"mim_id":"614316","title":"VESICLE TRANSPORT THROUGH INTERACTION WITH T-SNARES 1A; VTI1A","url":"https://www.omim.org/entry/614316"},{"mim_id":"610252","title":"MICRO RNA 1-2; MIR1-2","url":"https://www.omim.org/entry/610252"},{"mim_id":"609772","title":"CORTACTIN-BINDING PROTEIN 2; CTTNBP2","url":"https://www.omim.org/entry/609772"},{"mim_id":"608182","title":"POTASSIUM CHANNEL-INTERACTING PROTEIN 4","url":"https://www.omim.org/entry/608182"},{"mim_id":"606195","title":"IROQUOIS HOMEOBOX PROTEIN 5; IRX5","url":"https://www.omim.org/entry/606195"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"brain","ntpm":32.3}],"url":"https://www.proteinatlas.org/search/KCND2"},"hgnc":{"alias_symbol":["Kv4.2","RK5","KIAA1044"],"prev_symbol":[]},"alphafold":{"accession":"Q9NZV8","domains":[{"cath_id":"3.30.710.10","chopping":"40-155","consensus_level":"medium","plddt":91.4342,"start":40,"end":155},{"cath_id":"1.20.120.350","chopping":"177-306","consensus_level":"high","plddt":87.7568,"start":177,"end":306},{"cath_id":"1.10.287.70","chopping":"313-430","consensus_level":"high","plddt":91.9695,"start":313,"end":430}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NZV8","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NZV8-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NZV8-F1-predicted_aligned_error_v6.png","plddt_mean":71.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KCND2","jax_strain_url":"https://www.jax.org/strain/search?query=KCND2"},"sequence":{"accession":"Q9NZV8","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NZV8.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NZV8/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NZV8"}},"corpus_meta":[{"pmid":"17582333","id":"PMC_17582333","title":"Regulation of dendritic excitability by activity-dependent trafficking of the A-type K+ channel subunit Kv4.2 in hippocampal neurons.","date":"2007","source":"Neuron","url":"https://pubmed.ncbi.nlm.nih.gov/17582333","citation_count":276,"is_preprint":false},{"pmid":"17122039","id":"PMC_17122039","title":"Deletion of Kv4.2 gene eliminates dendritic A-type K+ current and enhances induction of long-term potentiation in hippocampal CA1 pyramidal neurons.","date":"2006","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/17122039","citation_count":270,"is_preprint":false},{"pmid":"23225603","id":"PMC_23225603","title":"Encephalitis and antibodies to dipeptidyl-peptidase-like protein-6, a subunit of Kv4.2 potassium channels.","date":"2012","source":"Annals of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/23225603","citation_count":251,"is_preprint":false},{"pmid":"12829703","id":"PMC_12829703","title":"A fundamental role for KChIPs in determining the molecular properties and trafficking of Kv4.2 potassium channels.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12829703","citation_count":217,"is_preprint":false},{"pmid":"11080179","id":"PMC_11080179","title":"The A-type potassium channel Kv4.2 is a substrate for the mitogen-activated protein kinase ERK.","date":"2000","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11080179","citation_count":214,"is_preprint":false},{"pmid":"9547221","id":"PMC_9547221","title":"Somatodendritic depolarization-activated potassium currents in rat neostriatal cholinergic interneurons are predominantly of the A type and attributable to coexpression of Kv4.2 and Kv4.1 subunits.","date":"1998","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/9547221","citation_count":187,"is_preprint":false},{"pmid":"16251476","id":"PMC_16251476","title":"ERK/MAPK regulates the Kv4.2 potassium channel by direct phosphorylation of the pore-forming subunit.","date":"2005","source":"American journal of physiology. 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hypertrophy or myocardial dysfunction.","date":"2005","source":"Circulation research","url":"https://pubmed.ncbi.nlm.nih.gov/16293790","citation_count":128,"is_preprint":false},{"pmid":"15454437","id":"PMC_15454437","title":"Modulation of Kv4.2 channel expression and gating by dipeptidyl peptidase 10 (DPP10).","date":"2004","source":"Biophysical journal","url":"https://pubmed.ncbi.nlm.nih.gov/15454437","citation_count":117,"is_preprint":false},{"pmid":"16123112","id":"PMC_16123112","title":"Multiprotein assembly of Kv4.2, KChIP3 and DPP10 produces ternary channel complexes with ISA-like properties.","date":"2005","source":"The Journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/16123112","citation_count":115,"is_preprint":false},{"pmid":"11102480","id":"PMC_11102480","title":"Localization and enhanced current density of the Kv4.2 potassium channel by interaction with the actin-binding protein filamin.","date":"2000","source":"The Journal of neuroscience : the official journal 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Heart and circulatory physiology","url":"https://pubmed.ncbi.nlm.nih.gov/14551056","citation_count":23,"is_preprint":false},{"pmid":"30254424","id":"PMC_30254424","title":"Saikosaponin A modulates remodeling of Kv4.2-mediated A-type voltage-gated potassium currents in rat chronic temporal lobe epilepsy.","date":"2018","source":"Drug design, development and therapy","url":"https://pubmed.ncbi.nlm.nih.gov/30254424","citation_count":23,"is_preprint":false},{"pmid":"17981906","id":"PMC_17981906","title":"Role of N-terminal domain and accessory subunits in controlling deactivation-inactivation coupling of Kv4.2 channels.","date":"2007","source":"Biophysical journal","url":"https://pubmed.ncbi.nlm.nih.gov/17981906","citation_count":23,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":55531,"output_tokens":11522,"usd":0.169711},"stage2":{"model":"claude-opus-4-6","input_tokens":15600,"output_tokens":3819,"usd":0.260213},"total_usd":0.429924,"stage1_batch_id":"msgbatch_01DzrsgVgYngY1hvM3DU1yF2","stage2_batch_id":"msgbatch_01KA9b7iRzKFdhoBUT7vCvSe","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1991,\n      \"finding\": \"Kv4.2 (RK5) encodes a rapidly inactivating A-type potassium current when expressed in Xenopus oocytes, with kinetics consistent with contribution to cardiac Ito current (activation rise time ~2.8 ms, midpoint ~-1 mV, rapid inactivation with tau 15 and 60 ms, sensitive to 4-AP but not TEA or dendrotoxins).\",\n      \"method\": \"Xenopus oocyte expression with two-electrode voltage clamp\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution in heterologous system with full biophysical characterization\",\n      \"pmids\": [\"1722463\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"4-aminopyridine blocks Kv4.2 exclusively from the closed (resting) state via an intracellular binding site, and channel inactivation and 4-AP binding are mutually exclusive, indicating that the 4-AP binding site is near cytoplasmic domains involved in inactivation.\",\n      \"method\": \"Two-electrode voltage clamp in Xenopus oocytes with pharmacological analysis\",\n      \"journal\": \"The Journal of pharmacology and experimental therapeutics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — rigorous in vitro biophysical dissection with state-dependent analysis\",\n      \"pmids\": [\"8930194\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Kv4.2 is localized to the somatodendritic membrane of neurons and is concentrated postsynaptically at synaptic contacts in rat supraoptic nucleus, as demonstrated by immunoelectron microscopy.\",\n      \"method\": \"Confocal and immunoelectron microscopy\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct ultrastructural localization with quantitative immunogold\",\n      \"pmids\": [\"9070739\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"A truncated dominant-negative Kv4.2 construct (Kv4.2ST) suppresses A-type currents in cerebellar granule neurons and Ito in ventricular myocytes when delivered by adenoviral gene transfer, establishing that Kv4 family subunits are the primary contributors to these currents.\",\n      \"method\": \"Dominant-negative adenoviral overexpression in neurons and cardiac myocytes with patch-clamp recording\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean loss-of-function with specific electrophysiological readout in native cells\",\n      \"pmids\": [\"9395498\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Kv4.2 electrophysiological and pharmacological properties (including flecainide sensitivity and rapid recovery from inactivation) closely match native cardiac Ito in rat myocytes, supporting Kv4.2 as a major molecular substrate of cardiac transient outward current.\",\n      \"method\": \"Stable expression in mouse L-cells, whole-cell voltage clamp, pharmacological profiling\",\n      \"journal\": \"Cardiovascular research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct comparison of recombinant and native currents with pharmacological validation\",\n      \"pmids\": [\"9093524\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Kv4.2 mRNA is co-expressed with Kv4.1 in neostriatal cholinergic interneurons and Kv4.2 protein is present in somatodendritic membranes; A-type current recovery kinetics match Kv4.2/Kv4.1 channels rather than Kv1.4, indicating Kv4.2-containing channels underlie somatodendritic A-current in these neurons.\",\n      \"method\": \"Single-cell RT-PCR, immunocytochemistry, whole-cell voltage clamp with kinetic analysis\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (electrophysiology, immunocytochemistry, single-cell PCR)\",\n      \"pmids\": [\"9547221\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Kv4.2 mRNA abundance is linearly correlated with A-type K+ current amplitude across four neuron types (neostriatal medium spiny neurons, cholinergic interneurons, globus pallidus neurons, basal forebrain cholinergic neurons), establishing Kv4.2 as the major determinant of somatodendritic A-current in these neurons.\",\n      \"method\": \"Quantitative single-cell RT-PCR combined with voltage-clamp analysis\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — quantitative correlation validated across multiple cell types with two independent methods\",\n      \"pmids\": [\"10632587\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"ERK2 directly phosphorylates Kv4.2 at three C-terminal sites: Thr602, Thr607, and Ser616, as identified by in vitro kinase assay and phosphopeptide mapping; ERK-phosphorylated Kv4.2 was confirmed in rat hippocampus using phospho-site-selective antibodies.\",\n      \"method\": \"In vitro kinase assay with GST fusion proteins, phosphopeptide mapping, phospho-selective antibodies in native tissue\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro phosphorylation with site identification and validation in vivo\",\n      \"pmids\": [\"11080179\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"PKA directly phosphorylates Kv4.2 at Thr38 (N-terminus) and Ser552 (C-terminus), identified by in vitro kinase assay, phosphopeptide mapping, and confirmed in intact COS-7 cells and hippocampal CA1.\",\n      \"method\": \"In vitro kinase assay with GST-fusion proteins, phosphopeptide mapping, phospho-selective antisera, intact cell PKA stimulation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro with site mutagenesis and in vivo validation\",\n      \"pmids\": [\"10681507\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Kv4.2 interacts directly with the actin-binding protein filamin via yeast two-hybrid and co-immunoprecipitation from brain; this interaction localizes Kv4.2 to filopodial roots and increases whole-cell current density ~2.7-fold in filamin-positive vs. filamin-negative cells.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation from brain and in vitro, immunocytochemistry, whole-cell patch clamp in filamin+/- cells\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP from brain plus functional consequence in defined cell system\",\n      \"pmids\": [\"11102480\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Kv4.2 localizes predominantly to the transverse-axial tubular system (T-tubules) in rat ventricular myocytes, as demonstrated by immunofluorescence and immunogold electron microscopy.\",\n      \"method\": \"Immunofluorescence, immunoelectron microscopy with FluoroNanogold\",\n      \"journal\": \"Journal of molecular and cellular cardiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct ultrastructural localization with correlative approaches\",\n      \"pmids\": [\"10860776\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Kv4.2 channel inactivation occurs from both open and pre-open closed states; N-terminal deletion (residues 2-40) slows open-state inactivation components without affecting closed-state inactivation or recovery, indicating the N-terminus contributes to open-state but not closed-state inactivation.\",\n      \"method\": \"Whole-cell patch clamp in HEK293 cells with N-terminal deletion mutants, kinetic modeling\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis with detailed kinetic analysis and allosteric modeling\",\n      \"pmids\": [\"11507158\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"MiRP1 (KCNE2) co-immunoprecipitates with Kv4.2 and modulates its gating (slows activation and inactivation, shifts voltage dependence positive) in a dose-dependent manner in Xenopus oocytes, suggesting MiRP1 serves as a regulatory beta subunit of cardiac Ito channels.\",\n      \"method\": \"Xenopus oocyte expression, two-electrode voltage clamp, co-immunoprecipitation\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — co-IP combined with dose-dependent functional analysis\",\n      \"pmids\": [\"11375270\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PSD-95 interacts with Kv4.2 via the C-terminal VSAL motif; co-expression of PSD-95 increases surface expression of Kv4.2 and causes its clustering; palmitoylation of PSD-95 is required for these effects.\",\n      \"method\": \"Co-immunoprecipitation in mammalian cells, mutation analysis of VSAL motif, deconvolution microscopy, surface biotinylation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods with defined binding motif and functional consequence\",\n      \"pmids\": [\"11923279\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PKA phosphorylation of Kv4.2 alpha-subunit is necessary but not sufficient for channel modulation; association with the ancillary subunit KChIP3 is additionally required for PKA-dependent regulation of Kv4.2 channel properties.\",\n      \"method\": \"Electrophysiology in Xenopus oocytes, PKA stimulation, KChIP3 co-expression, site-directed mutagenesis\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — epistasis-based functional analysis with mutagenesis showing supramolecular requirement\",\n      \"pmids\": [\"12451113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"KChIP1-3 co-expression with Kv4.2 releases ER retention, promotes surface trafficking, increases steady-state expression, alters phosphorylation, and changes detergent solubility; these effects occur through masking of an N-terminal hydrophobic domain of Kv4.2. KChIP4a does not exert these effects and negatively modulates other KChIPs.\",\n      \"method\": \"Co-expression in heterologous cells, immunocytochemistry, surface biotinylation, biochemical fractionation, phosphorylation analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal biochemical methods with defined N-terminal mechanism\",\n      \"pmids\": [\"12829703\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Kv4.2 and KChIP2 form octameric complexes with 4:4 stoichiometry (4 Kv4.2 and 4 KChIP2 subunits), as determined by purification of native Ito complexes and direct amino acid analysis.\",\n      \"method\": \"Protein purification, electron microscopy, amino acid analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — biochemical purification with direct stoichiometric determination\",\n      \"pmids\": [\"14623880\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"PSD-95 recruits Kv1.4, but not Kv4.2, to lipid rafts via palmitoylation-dependent mechanism; a fraction of native Kv4.2 is found in lipid rafts in rat brain and hippocampal neurons via an alternative PSD-95-independent mechanism.\",\n      \"method\": \"Lipid raft fractionation, lipid raft patching, immunostaining, co-expression in heterologous cells, VSAL deletion mutants\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab with biochemical fractionation and cell imaging\",\n      \"pmids\": [\"14559911\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"CaMKII directly phosphorylates Kv4.2 at Ser438 and Ser459 in vitro; CaMKII phosphorylation does not alter channel biophysics but increases Kv4.2 protein levels and surface expression, leading to increased A-current amplitude and decreased neuronal excitability in hippocampal neurons.\",\n      \"method\": \"In vitro kinase assay, site-directed mutagenesis, Xenopus oocyte expression, CaMKII overexpression in hippocampal neurons, whole-cell patch clamp\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro kinase assay with mutagenesis plus functional validation in neurons\",\n      \"pmids\": [\"15071113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"DPP10 co-immunoprecipitates with Kv4.2, enhances surface expression ~5-fold without changing protein levels, and remodels gating kinetics by accelerating inactivation and recovery and shifting conductance-voltage relationship ~19 mV hyperpolarized; the cytoplasmic N-terminal domain of DPP10 determines inactivation acceleration.\",\n      \"method\": \"Co-immunoprecipitation from Xenopus oocytes, two-electrode voltage clamp, domain deletion analysis\",\n      \"journal\": \"Biophysical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — co-IP plus detailed biophysical characterization with domain mapping\",\n      \"pmids\": [\"15454437\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Direct ERK/MAPK phosphorylation of Kv4.2 at Thr607 mimics ERK-induced rightward shift in activation and current reduction; this effect requires KChIP3 co-expression. Ser616 phosphorylation produces the opposite gating effect.\",\n      \"method\": \"Site-directed mutagenesis (phosphomimetic T607D, S616D), Xenopus oocyte electrophysiology, co-expression with KChIP3\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — phosphomimetic mutagenesis with functional electrophysiological validation\",\n      \"pmids\": [\"16251476\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Kv4.2, KChIP3, and DPP10 form ternary macromolecular complexes in rat brain and heterologous cells (confirmed by co-immunoprecipitation); ternary complexes show greatly accelerated recovery from inactivation (~18-26 ms) that matches native ISA, distinct from binary Kv4.2+KChIP3 or Kv4.2+DPP10 channels.\",\n      \"method\": \"Co-immunoprecipitation from rat brain and oocytes, two-electrode voltage clamp in oocytes and CHO cells\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP from native tissue plus functional reconstitution matching native current\",\n      \"pmids\": [\"16123112\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Kv4.2 is transported to dendrites by the kinesin motor Kif17; dominant-negative Kif17 inhibits dendritic localization of endogenous and introduced Kv4.2, while Kv4.2 and Kif17 co-immunoprecipitate from brain and co-localize in cortical neuron dendrites. The interaction occurs through the extreme C-terminus of Kv4.2.\",\n      \"method\": \"Dominant-negative kinesin expression, co-immunoprecipitation from brain and COS cells, immunofluorescence co-localization in cortical neurons\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — co-IP from brain tissue plus loss-of-function with defined interaction domain\",\n      \"pmids\": [\"16257958\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Targeted deletion of Kv4.2 eliminates fast transient outward current Ito,f in ventricular myocytes; Kv1.4 protein and Ito,s are upregulated compensatorily, while KChIP2 expression is markedly reduced, demonstrating that Kv4.2 is essential for Ito,f generation and that KChIP2 stability depends on Kv4.2.\",\n      \"method\": \"Kv4.2 knockout mice, voltage-clamp recordings from ventricular myocytes, Western blot\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic KO with defined electrophysiological and molecular phenotype\",\n      \"pmids\": [\"16293790\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"KChIP N-terminus residues 11-23 form a primary interaction site with Kv4.2, the T1 domain provides a secondary site, and C-terminal deletions of Kv4.2 also reduce KChIP binding and functional modulation, revealing a C-terminal interaction site.\",\n      \"method\": \"Lysine-scanning and structure-based mutagenesis of Kv4.2, co-immunoprecipitation, whole-cell patch clamp in mammalian cells\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic mutagenesis defining structural determinants of interaction with parallel biochemical and functional validation\",\n      \"pmids\": [\"16096338\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"GRK2 phosphorylates DREAM/KChIP3 at Ser95; the phosphomimetic S95D mutation blocks DREAM-mediated membrane expression of Kv4.2 without affecting channel tetramerization; calcineurin dephosphorylates GRK2-phosphorylated DREAM and its inhibition also blocks Kv4.2 trafficking, establishing a GRK2/calcineurin-dependent regulation of Kv4.2 surface expression via KChIP3.\",\n      \"method\": \"In vitro kinase assay, site-directed mutagenesis (S95D), calcineurin inhibitor treatment, cell surface expression assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro kinase identification with phosphomimetic mutagenesis and functional surface expression consequence\",\n      \"pmids\": [\"17102134\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Deletion of Kv4.2 eliminates dendritic A-type K+ current in CA1 pyramidal neurons nearly completely, increases backpropagating action potential amplitude and Ca2+ influx, and lowers the threshold for LTP induction with theta burst pairing, establishing Kv4.2 as the molecular substrate of dendritic A-current that regulates synaptic plasticity.\",\n      \"method\": \"Kv4.2 knockout mice, dendritic patch-clamp recordings, calcium imaging, LTP induction\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic KO with multiple electrophysiological and functional phenotypic readouts\",\n      \"pmids\": [\"17122039\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"In Kv4.2 knockout mice, KChIP expression is regionally and cell-specifically reduced in proportion to the normal Kv4.2 expression level, demonstrating reciprocal Kv4.2-dependent stabilization of KChIP auxiliary subunits.\",\n      \"method\": \"Immunohistochemistry in Kv4.2 KO vs. wild-type brains\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic model with systematic protein expression analysis across brain regions\",\n      \"pmids\": [\"17122038\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Kv4.2 undergoes activity-dependent internalization in hippocampal spines and dendrites upon glutamate receptor stimulation; this internalization is clathrin-mediated, requires NMDA receptor activation and Ca2+ influx. LTP induction causes synaptic GluR1-AMPAR insertion concurrent with Kv4.2 internalization.\",\n      \"method\": \"Live imaging of EGFP-Kv4.2 in hippocampal neurons, electrophysiology (mEPSC recordings), LTP induction in slice cultures\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — live imaging plus electrophysiology in neurons with defined mechanistic requirements\",\n      \"pmids\": [\"17582333\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"SAP97 interacts with Kv4.2 via its PDZ domains and the intact C-terminus of Kv4.2; SAP97 directs Kv4.2 to dendritic spines (PSD fraction); CaMKII-dependent phosphorylation of SAP97 regulates this Kv4.2 targeting to spines.\",\n      \"method\": \"Co-immunoprecipitation, subcellular fractionation, lentiviral RNAi of SAP97, pharmacological SAP97 translocation in hippocampal neurons\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — co-IP, fractionation, and RNAi with functional localization consequence\",\n      \"pmids\": [\"17635915\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"mGlu5 activation leads to ERK-mediated phosphorylation of Kv4.2 at Ser616, inhibiting A-type K+ currents and increasing dorsal horn neuronal excitability; Kv4.2 knockout mice show impaired nociceptive behavior after spinal group I mGluR activation, establishing Kv4.2 as a downstream effector of mGlu5-ERK signaling in nociception.\",\n      \"method\": \"Electrophysiology in dorsal horn neurons, site-directed mutagenesis of S616, Kv4.2 KO mice, behavioral nociception assays\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — mutagenesis of phosphorylation site plus KO behavioral validation\",\n      \"pmids\": [\"18045912\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PKA activation induces Kv4.2 internalization from dendritic spines; PKA inhibition prevents AMPA-induced internalization; a point mutation at the C-terminal PKA phosphorylation site S552A prevents AMPA-induced internalization of Kv4.2, establishing S552 as required for PKA-dependent activity-driven trafficking.\",\n      \"method\": \"Live imaging in hippocampal neurons, pharmacological PKA activation/inhibition, point mutation S552A\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — live imaging with site-specific mutagenesis demonstrating mechanistic requirement\",\n      \"pmids\": [\"18650329\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Kv4.2 deletion eliminates IA in cortical pyramidal neurons, accompanied by loss of KChIP3 protein (degraded without Kv4.2) and upregulation of IK and Iss densities (electrical remodeling), but without change in action potential waveform.\",\n      \"method\": \"Kv4.2 KO mice, whole-cell voltage clamp of cortical neurons, Western blot\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic KO with electrophysiological and molecular readouts\",\n      \"pmids\": [\"18187474\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Kv4.2 ISA channels are complexes of four Kv4.2 and four DPP6 subunits (4:4 stoichiometry), established by tandem-linked subunit biophysics and direct amino acid analysis of purified complexes.\",\n      \"method\": \"Tandem-linked subunit expression, electrophysiology, protein purification and amino acid analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution with direct biochemical stoichiometric measurement\",\n      \"pmids\": [\"18364354\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Ternary Kv4.2+KChIP1+DPPX-S channels reconstitute the voltage-dependent slowing of inactivation rate (characteristic of native ISA in cerebellar granule neurons) through a mechanism of preferential closed-state inactivation and weakly voltage-dependent opening, as shown by quantitative kinetic modeling.\",\n      \"method\": \"Whole-cell patch clamp in heterologous cells, native neuron recordings, global kinetic modeling\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution in heterologous cells matching native channel properties with kinetic modeling\",\n      \"pmids\": [\"18276729\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Gating charge (Q) immobilization in Kv4.2 occurs over hyperpolarized voltages that do not open channels, with kinetics and voltage dependence paralleling closed-state inactivation; Q-immobilization and closed-state inactivation are two manifestations of the same process involving desensitization of voltage sensors.\",\n      \"method\": \"Gating current measurements in CTX-blocked Kv4.2 channels in Xenopus oocytes, coupled state modeling\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct gating current measurement with mechanistic modeling\",\n      \"pmids\": [\"18299396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PKC directly phosphorylates Kv4.2 at Ser447 and Ser537 on the C-terminus; mutation of both sites to alanine increases surface expression; PKC phosphorylation at Ser537 (within an ERK docking domain) enhances subsequent ERK phosphorylation of Kv4.2, establishing Kv4.2 as a locus for PKC-ERK cross-talk.\",\n      \"method\": \"In vitro kinase assay with GST fusion proteins, phospho-site antibody, surface biotinylation, electrophysiology, sequential kinase assay\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro kinase assay with site identification, mutagenesis, and cross-kinase signaling validation\",\n      \"pmids\": [\"18795890\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"S4-S5 linker and S6 residues Glu323 and Val404 are critical for both voltage-dependent gate opening and closed-state inactivation in Kv4.2 channels; double-mutant cycle analysis and redox modulation of cysteine double mutants confirm dynamic coupling between voltage sensor and cytoplasmic gate underlies closed-state inactivation.\",\n      \"method\": \"Alanine-scanning mutagenesis, double-mutant cycle analysis, cysteine-substitution redox modulation, two-electrode voltage clamp in Xenopus oocytes\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic mutagenesis with thermodynamic cycle analysis and chemical crosslinking\",\n      \"pmids\": [\"19171772\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"DPP6-S is necessary and sufficient to increase the unitary conductance of neuronal Kv4.2 channels from ~4 pS to ~7.5 pS (matching native CGN channels); CGN Kv4 channels from dpp6 KO mice show reduced conductance; two N-terminal acidic residues of DPP6-S mediate this effect via electrostatic interactions.\",\n      \"method\": \"Single-channel recordings from heterologous cells and CGNs, dpp6 KO mice, charge neutralization mutagenesis of DPP6-S\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — single-channel reconstitution with KO validation and mutagenesis of mechanism\",\n      \"pmids\": [\"19279261\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"KChIP4a requires PKA phosphorylation of Kv4.2 at S552 to produce enhanced stabilization and membrane expression of Kv4.2, while other KChIP isoforms (KChIP1-3) enhance surface expression independently of S552 phosphorylation; A-kinase anchoring proteins (AKAPs) bind Kv4.2, enabling local PKA signaling.\",\n      \"method\": \"Co-expression in heterologous cells, surface biotinylation, S552A/D mutagenesis, co-immunoprecipitation for AKAP interaction\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — mutagenesis with surface expression assay and new AKAP interaction identification\",\n      \"pmids\": [\"20045463\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CaV3.1 (T-type calcium channel) associates with the Kv4.2 complex (Kv4.2-KChIP3-DPP10c) and mediates calcium-dependent rightward shift in Kv4.2 inactivation voltage; this regulation is selective for CaV3 isoforms and not observed with CaV1.4, CaV2.1, or CaV2.3.\",\n      \"method\": \"Co-expression in heterologous cells, electrophysiology measuring inactivation voltage shift\",\n      \"journal\": \"Channels\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — functional co-expression without direct physical interaction confirmation\",\n      \"pmids\": [\"20458163\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"NR2B-containing (extrasynaptic) NMDA receptors mediate glutamate-induced reduction of total Kv4.2 protein and Kv4.2 clusters; Ca2+ influx is required; calpain proteolysis underlies Kv4.2 protein reduction, as calpain inhibitors prevent this effect.\",\n      \"method\": \"Pharmacological dissection with NR2B-selective antagonists and calpain inhibitors, immunocytochemistry, patch-clamp in cultured hippocampal neurons\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — defined pharmacological mechanism with multiple inhibitors and imaging\",\n      \"pmids\": [\"19857555\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"DPP6 and DPP10 independently stabilize surface Kv4.2 protein without affecting DPP protein levels themselves; KChIP3 addition to DPP10+Kv4.2 further increases total and surface Kv4.2; DPP6/10 expression and localization are independent of Kv4 alpha-subunits.\",\n      \"method\": \"Heterologous co-expression, surface biotinylation, Kv4.2/Kv4.3 KO mouse brain Western blot, cell surface immunostaining\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO validation combined with heterologous reconstitution and biochemical quantification\",\n      \"pmids\": [\"22311982\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"A de novo missense mutation V404M (Val404Met) in KCND2 causes significantly slowed Kv4.2 inactivation (dominant effect) and impairs closed-state inactivation in the presence of auxiliary subunits, consistent with gain-of-function causing epilepsy and autism in affected twins.\",\n      \"method\": \"Whole-exome sequencing, heterologous expression electrophysiology of WT and mutant Kv4.2 in Xenopus oocytes, co-expression with auxiliary subunits\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — functional characterization of disease mutation with auxiliary subunit co-expression\",\n      \"pmids\": [\"24501278\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"H2S inhibits Ito by targeting the Cys320/Cys529 disulfide bridge in Kv4.2; mutation of either cysteine blocks H2S-mediated inhibition; H2S breaks an existing disulfide bond without modifying single free cysteines.\",\n      \"method\": \"Mutagenesis of Cys320 and Cys529, whole-cell patch clamp in cardiomyocytes, H2S pharmacology\",\n      \"journal\": \"Antioxidants & redox signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — site-specific mutagenesis defining the molecular target of H2S modulation\",\n      \"pmids\": [\"25756524\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"miR-324-5p directly binds KCND2 mRNA and inhibits Kv4.2 protein expression; antagonizing miR-324-5p is neuroprotective, seizure-suppressive, and blocks kainic-acid-induced Kv4.2 reduction in vitro and in vivo; these effects are absent in Kcnd2 KO mice, confirming specificity.\",\n      \"method\": \"RNA-induced silencing complex pulldown, miRNA mimic/antagonist transfection, luciferase reporter assay, in vivo miRNA antagonist injection, Kcnd2 KO mice\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct RISC pulldown, luciferase validation, and KO confirmation\",\n      \"pmids\": [\"27681419\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The autism/epilepsy mutation V404M (Kv4.2) enhances closed-state inactivation (increases inactivated state stability) while dramatically impairing open-state inactivation by slowing channel closure; larger methionine volume is a key mechanistic factor; this reveals that channel closure is required for closed-state inactivation.\",\n      \"method\": \"Whole-cell patch clamp of WT and V404M Kv4.2 in heterologous cells, detailed kinetic analysis of CSI and OSI\",\n      \"journal\": \"PNAS\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — detailed mechanistic mutagenesis with biophysical dissection of inactivation states\",\n      \"pmids\": [\"29581270\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"A gain-of-function mutation S447R in KCND2 causes nocturnal paroxysmal atrial fibrillation; S447 is a PKC phosphorylation site that normally attenuates Kv4.2 membrane expression; the S447R mutant shows impaired response to PKC and augmented membrane expression; the mutation also exerts gain-of-function in Kv4.2-Kv4.3 heterotetramers.\",\n      \"method\": \"Xenopus oocyte electrophysiology, Kv4.2-Kv4.3 hybrid channel expression, linkage analysis, whole-exome sequencing\",\n      \"journal\": \"Circulation. Genomic and precision medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — functional characterization of disease mutation with hybrid channel experiments and defined PKC site mechanism\",\n      \"pmids\": [\"30571183\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Activity-induced ERK phosphorylation of Kv4.2 at pThr607-Pro triggers Pin1 binding and isomerization of Kv4.2, causing dissociation of the Kv4.2-DPP6 complex; Kv4.2-TA (T607A knock-in) mice show altered Kv4.2-DPP6 interaction, increased A-type K+ current, reduced hippocampal neuronal excitability, and improved reversal learning.\",\n      \"method\": \"Kv4.2-T607A knock-in mouse model, co-immunoprecipitation for Pin1 and DPP6 interaction, whole-cell patch clamp in CA1 neurons, behavioral testing\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — knock-in mouse with defined molecular mechanism and multiple orthogonal functional readouts\",\n      \"pmids\": [\"32218435\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"GSK3β directly phosphorylates Kv4.2 at Ser616 in nucleus accumbens medium spiny neurons, inhibiting A-type K+ channel function and driving tLTP changes in a chronic stress depression model; GSK3β knockdown or Kv4.2-S616 phosphorylation blockade prevents maladaptive plasticity.\",\n      \"method\": \"In vivo AAV-RNAi knockdown of GSK3β, electrophysiology, immunohistochemistry, biochemistry, pharmacological Kv4.2 channel inhibition in mouse NAc\",\n      \"journal\": \"PNAS\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo genetic silencing with multiple orthogonal electrophysiological and biochemical readouts\",\n      \"pmids\": [\"32209671\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"DPPX-S (DPP6) remodels gating charge dynamics in Kv4.2 channels by causing a -26 mV parallel shift in the Q-V relationship and accelerating both outward and return gating charge movements; this effect is absent in Shaker B channels, indicating DPPX-S specifically destabilizes resting and intermediate activation states in Kv4.2.\",\n      \"method\": \"Gating current measurements in CTX-blocked Kv4.2 channels in Xenopus oocytes, co-expression with DPPX-S\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct gating current measurement with appropriate controls\",\n      \"pmids\": [\"17130523\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Kvbeta1.2 co-expression with Kv4.2 in HEK293 cells confers oxygen/redox sensitivity to Kv4.2 channels (but not to Shaker), enabling inhibition by hypoxia, DTT, and DTDP; the O2 sensitivity is membrane-delimited and involves a hemoprotein O2 sensor.\",\n      \"method\": \"Heterologous co-expression in HEK293 cells, whole-cell patch clamp under hypoxia and redox agents, excised patch recordings\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — defined co-expression requirement with cell-free patch confirmation of membrane-delimited mechanism\",\n      \"pmids\": [\"10352037\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Kv4.2 (KCND2) is the principal pore-forming alpha-subunit of somatodendritic A-type (ISA/Ito) potassium channels in neurons and cardiac myocytes; it forms octameric macromolecular complexes (4:4 stoichiometry) with cytoplasmic KChIP auxiliary subunits and transmembrane DPP6/DPP10 subunits, which together promote ER exit, surface trafficking, and confer native gating kinetics (including rapid recovery and voltage-dependent inactivation); channel availability is dynamically regulated by phosphorylation at multiple sites (ERK at T602/T607/S616, PKA at T38/S552, CaMKII at S438/S459, PKC at S447/S537), by activity-dependent clathrin-mediated internalization requiring NMDA-R activation, Ca2+, and PKA-S552 phosphorylation, by Pin1-mediated isomerization at pT607-Pro that dissociates the DPP6 complex, and by miRNA-mediated (miR-324-5p) translational silencing, with dendritic targeting dependent on Kif17 motor and SAP97/PSD-95 scaffolding interactions.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"KCND2 (Kv4.2) is the principal pore-forming α-subunit of rapidly inactivating, somatodendritic A-type potassium channels in neurons and the fast transient outward current (Ito,f) channel in ventricular cardiomyocytes, serving as a major regulator of dendritic excitability, action potential back-propagation, synaptic plasticity, and cardiac repolarization. Kv4.2 assembles into octameric macromolecular complexes with cytoplasmic KChIP (4:4 stoichiometry) and transmembrane DPP6/DPP10 auxiliary subunits, which together promote ER exit, surface trafficking, unitary conductance, and rapid recovery from inactivation that recapitulates native ISA gating [PMID:14623880, PMID:18364354, PMID:16123112, PMID:12829703]. Channel availability is dynamically tuned by phosphorylation at multiple C-terminal sites—ERK (T602/T607/S616), PKA (T38/S552), PKC (S447/S537), CaMKII (S438/S459), and GSK3β (S616)—and by activity-dependent clathrin-mediated internalization requiring NMDA receptor activation and PKA phosphorylation at S552, as well as Pin1-catalyzed prolyl isomerization at pT607 that dissociates the DPP6 complex [PMID:11080179, PMID:10681507, PMID:18650329, PMID:32218435, PMID:32209671]. De novo gain-of-function mutations in KCND2 (V404M, S447R) cause epilepsy with autism spectrum features and familial nocturnal paroxysmal atrial fibrillation, respectively [PMID:24501278, PMID:30571183].\",\n  \"teleology\": [\n    {\n      \"year\": 1991,\n      \"claim\": \"Establishing the basic identity of KCND2 as an A-type K+ channel gene resolved which molecular entity produces rapidly inactivating, 4-AP-sensitive currents with cardiac Ito-like properties.\",\n      \"evidence\": \"Heterologous expression in Xenopus oocytes with two-electrode voltage clamp\",\n      \"pmids\": [\"1722463\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Native subunit composition unknown\", \"Physiological role in neurons vs. heart not yet distinguished\", \"Inactivation mechanism (open vs. closed state) not resolved\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Demonstration that Kv4.2 localizes to somatodendritic membranes and that dominant-negative Kv4.2 suppresses neuronal A-current and cardiac Ito established Kv4.2 as the molecular basis of these native currents in both tissues.\",\n      \"evidence\": \"Immunoelectron microscopy in neurons, adenoviral dominant-negative expression with patch-clamp in cerebellar granule neurons and ventricular myocytes\",\n      \"pmids\": [\"9070739\", \"9395498\", \"9093524\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Auxiliary subunits not yet identified\", \"Phosphorylation-dependent regulation unknown\", \"Trafficking mechanisms undefined\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Identification of ERK (T602/T607/S616) and PKA (T38/S552) phosphorylation sites, the filamin interaction, and quantitative mRNA–current correlation across neuron types established that Kv4.2 is a convergent signaling target whose expression level directly determines A-current amplitude.\",\n      \"evidence\": \"In vitro kinase assays, phosphopeptide mapping, phospho-selective antibodies, yeast two-hybrid, co-IP from brain, quantitative single-cell RT-PCR with voltage clamp\",\n      \"pmids\": [\"11080179\", \"10681507\", \"11102480\", \"10632587\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequences of each phosphorylation site on channel gating not yet resolved\", \"Auxiliary subunit requirement for kinase modulation unknown\", \"ER-to-surface trafficking mechanism undefined\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Distinguishing N-terminal-dependent open-state inactivation from a separate closed-state inactivation pathway, and identifying KCNE2/MiRP1 as a modulatory β-subunit, revealed that Kv4.2 uses dual inactivation mechanisms and engages multiple types of auxiliary subunits.\",\n      \"evidence\": \"N-terminal deletion mutagenesis with kinetic modeling in HEK293 cells; co-IP and dose-dependent gating modulation by KCNE2 in oocytes\",\n      \"pmids\": [\"11507158\", \"11375270\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of closed-state inactivation not defined\", \"Relative contribution of KCNE2 vs. other β-subunits in native tissue unclear\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Discovery that KChIPs form 4:4 octameric complexes with Kv4.2, mask an N-terminal ER-retention signal, and promote surface trafficking resolved how auxiliary subunits control channel biogenesis and established the native channel stoichiometry.\",\n      \"evidence\": \"Protein purification with amino acid analysis, electron microscopy, surface biotinylation with KChIP1-3 co-expression, N-terminal domain mapping\",\n      \"pmids\": [\"14623880\", \"12829703\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"DPP stoichiometry and ternary complex architecture not yet determined\", \"KChIP4a inhibitory mechanism not fully resolved\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Reconstitution of ternary Kv4.2–KChIP–DPP complexes and genetic knockout studies demonstrated that DPP6/10 contributes the rapid recovery kinetics of native ISA, that Kv4.2 is essential for cardiac Ito,f, and that KChIP stability depends on Kv4.2 expression.\",\n      \"evidence\": \"Co-IP from brain, ternary co-expression electrophysiology matching native ISA, Kv4.2 KO mouse cardiac and neuronal recordings, KChIP protein quantification in KO\",\n      \"pmids\": [\"16123112\", \"16293790\", \"16251476\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"DPP6 stoichiometry in ternary complex not directly measured\", \"Mechanism by which DPP accelerates recovery not structurally resolved\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Kv4.2 KO elimination of dendritic A-current in CA1 neurons—with enhanced back-propagating action potentials, increased Ca2+ influx, and lowered LTP threshold—established Kv4.2 as the molecular gatekeeper of dendritic excitability and synaptic plasticity.\",\n      \"evidence\": \"Kv4.2 KO mice, dendritic patch-clamp, calcium imaging, theta-burst LTP in hippocampal slices\",\n      \"pmids\": [\"17122039\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Compensatory mechanisms in KO not fully catalogued\", \"Spine-specific vs. dendritic shaft contributions not separated\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Discovery of activity-dependent, NMDA-receptor- and clathrin-dependent Kv4.2 internalization from spines during LTP, and SAP97/Kif17-dependent dendritic targeting, revealed that Kv4.2 surface levels are bidirectionally regulated to tune synaptic strength.\",\n      \"evidence\": \"Live EGFP-Kv4.2 imaging, mEPSC recordings, dominant-negative Kif17, co-IP for SAP97 and Kif17 from brain\",\n      \"pmids\": [\"17582333\", \"17635915\", \"16257958\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endocytic adaptor proteins linking Kv4.2 to clathrin not identified\", \"Ubiquitination or degradation fate of internalized channels not determined\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Identification of PKA-S552 as the required phosphorylation event for activity-driven internalization, determination of 4:4 Kv4.2:DPP6 stoichiometry, and gating-charge immobilization studies linked phosphorylation-controlled trafficking to a defined voltage-sensor desensitization mechanism for closed-state inactivation.\",\n      \"evidence\": \"S552A mutagenesis with live imaging, tandem-linked subunit electrophysiology and protein purification, gating current measurements in CTX-blocked channels\",\n      \"pmids\": [\"18650329\", \"18364354\", \"18299396\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural rearrangement of voltage sensor during CSI not directly observed\", \"Interplay between PKA-S552 and KChIP/DPP in internalization not dissected\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"PKC phosphorylation sites (S447, S537) were mapped and shown to regulate surface expression and prime ERK phosphorylation, while structure–function analysis of S4-S5 linker and S6 residues defined the electromechanical coupling underlying closed-state inactivation.\",\n      \"evidence\": \"In vitro kinase assays, sequential kinase cross-talk experiments, alanine-scanning mutagenesis with double-mutant thermodynamic cycles in oocytes, single-channel recordings in DPP6 KO neurons\",\n      \"pmids\": [\"18795890\", \"19171772\", \"19279261\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic-resolution structure of the inactivated state not available\", \"PKC-ERK cross-talk not validated in native neurons\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identification of a de novo V404M mutation causing epilepsy and autism, with gain-of-function slowed inactivation, linked channel gating mechanisms to human neurodevelopmental disease.\",\n      \"evidence\": \"Whole-exome sequencing in affected twins, heterologous expression electrophysiology of V404M with auxiliary subunits\",\n      \"pmids\": [\"24501278\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo consequences of V404M in animal models not tested\", \"Genotype–phenotype spectrum of KCND2 variants not established\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"The S447R gain-of-function mutation causing familial atrial fibrillation disrupts PKC-mediated attenuation of Kv4.2 surface expression, and detailed biophysical analysis of V404M revealed that channel closure is prerequisite for closed-state inactivation, unifying gating and disease mechanisms.\",\n      \"evidence\": \"Linkage analysis and whole-exome sequencing, oocyte electrophysiology with Kv4.2-Kv4.3 heteromers, detailed kinetic dissection of V404M CSI/OSI\",\n      \"pmids\": [\"30571183\", \"29581270\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of V404M-induced gate obstruction not resolved at atomic level\", \"Penetrance and expressivity of KCND2 cardiac variants in larger cohorts unknown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Pin1 prolyl isomerase was identified as a signal-dependent disassembly switch for the Kv4.2–DPP6 complex via ERK-phosphorylated T607, and GSK3β was shown to phosphorylate S616 to drive maladaptive plasticity in depression models, revealing kinase-specific channel modulation in behavioral circuits.\",\n      \"evidence\": \"Kv4.2-T607A knock-in mice with co-IP, electrophysiology, and behavioral testing; AAV-RNAi of GSK3β in nucleus accumbens with electrophysiology and biochemistry\",\n      \"pmids\": [\"32218435\", \"32209671\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Pin1-dependent complex disassembly not reconstituted in vitro with purified components\", \"How GSK3β accesses Kv4.2 at the membrane is unclear\", \"Whether Pin1 and GSK3β pathways interact on the same channel complex is untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"High-resolution structural determination of the full Kv4.2–KChIP–DPP ternary complex, the conformational basis of closed-state inactivation, and genotype-phenotype relationships across the expanding spectrum of KCND2 disease variants remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No cryo-EM or crystal structure of ternary Kv4.2–KChIP–DPP complex\", \"Mechanism of clathrin adaptor recruitment to internalized Kv4.2 unknown\", \"Full spectrum of KCND2 pathogenic variants and disease mechanisms incomplete\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 3, 4, 23, 26]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [2, 10, 13, 15, 28]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [15]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [28, 31]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [2, 5, 6, 26]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [7, 8, 36, 48, 49]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 3, 4, 23]}\n    ],\n    \"complexes\": [\n      \"Kv4.2-KChIP octamer (4:4)\",\n      \"Kv4.2-DPP6 octamer (4:4)\",\n      \"Kv4.2-KChIP-DPP ternary complex\"\n    ],\n    \"partners\": [\n      \"KCNIP2\",\n      \"KCNIP3\",\n      \"DPP6\",\n      \"DPP10\",\n      \"DLG1\",\n      \"DLG4\",\n      \"KIF17\",\n      \"FLNA\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}