{"gene":"KCND2","run_date":"2026-06-10T01:55:23","timeline":{"discoveries":[{"year":1991,"finding":"Kv4.2 (RK5) encodes a voltage-sensitive A-type K+ channel that activates rapidly, inactivates with time constants of 15 and 60 ms, is sensitive to 4-AP (IC50 ~5 mM), and is insensitive to TEA and dendrotoxins, as demonstrated by heterologous expression in Xenopus oocytes.","method":"Two-electrode voltage-clamp in Xenopus oocytes","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro electrophysiological characterization of cloned channel, replicated across multiple subsequent studies","pmids":["1722463"],"is_preprint":false},{"year":1996,"finding":"4-AP blocks Kv4.2 channels exclusively from the intracellular side in the closed state; binding and channel inactivation are mutually exclusive, indicating the 4-AP binding site is at or adjacent to the 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 / Strong — detailed kinetic and state-dependent pharmacological analysis with multiple voltage protocols","pmids":["8930194"],"is_preprint":false},{"year":1997,"finding":"Dominant-negative truncated Kv4.2 (Kv4.2ST, truncated after the first transmembrane segment) suppresses A-type currents in cerebellar granule cells and transient outward current (Ito) in rat ventricular myocytes when delivered by adenoviral gene transfer, demonstrating that Kv4 family subunits are the predominant contributors to these currents.","method":"Adenoviral dominant-negative overexpression, whole-cell patch clamp, cotransfection in CHO-K1 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — dominant-negative construct with electrophysiological validation in both heterologous cells and native neurons/myocytes","pmids":["9395498"],"is_preprint":false},{"year":1997,"finding":"Kv4.2 protein is clustered at the postsynaptic membrane of supraoptic nucleus neurons, specifically concentrated at synaptic contacts on somata and dendrites, as shown by immunoelectron microscopy.","method":"Confocal and immunoelectron microscopy","journal":"Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ultrastructural localization by immunoelectron microscopy, single lab, no functional consequence directly demonstrated","pmids":["9070739"],"is_preprint":false},{"year":1999,"finding":"Kvβ1.2 co-expression with Kv4.2 in HEK293 cells confers sensitivity to redox modulation and hypoxia to Kv4.2 channels; this O2 sensitivity is membrane-delimited and involves a hemoproteic O2 sensor, and is not observed with Shaker channels co-expressed with Kvβ1.2.","method":"Transfection in HEK293 cells, whole-cell patch clamp, cell-free patches, pharmacological redox agents","journal":"The Journal of general physiology","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — multiple orthogonal methods (cell-attached, inside-out patches, pharmacology) in single lab demonstrating mechanism","pmids":["10352037"],"is_preprint":false},{"year":2000,"finding":"ERK2 directly phosphorylates Kv4.2 at three C-terminal sites: Thr602, Thr607, and Ser616, as determined by in vitro kinase assays on GST-fusion proteins and phosphopeptide mapping, and ERK-phosphorylated Kv4.2 is detected in rat hippocampus in vivo.","method":"In vitro kinase assay with GST-fusion proteins, phosphopeptide mapping, amino acid sequencing, phospho-selective antibodies, COS-7 cell transfection","journal":"Journal of neurochemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro phosphorylation with site identification confirmed by multiple methods and validated 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 phosphorylation of GST-fusion proteins, phosphopeptide mapping, and confirmed in COS-7 cells and in rat hippocampal area CA1.","method":"In vitro PKA kinase assay with GST-fusion proteins, phosphopeptide mapping, amino acid sequencing, phospho-selective antibodies, COS-7 cell transfection","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro phosphorylation with site identification by sequencing, confirmed in intact cells and native tissue","pmids":["10681507"],"is_preprint":false},{"year":2000,"finding":"Kv4.2 directly interacts with the actin-binding protein filamin via yeast two-hybrid and co-immunoprecipitation from brain and in vitro; this interaction localizes Kv4.2 to filopodial roots in filamin+ cells and increases whole-cell Kv4.2 current density ~2.7-fold compared to filamin− 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 / Strong — reciprocal co-IP from brain, yeast two-hybrid, and functional electrophysiological consequence in matched cell lines","pmids":["11102480"],"is_preprint":false},{"year":2000,"finding":"Kv4.2 protein in rat ventricular myocytes localizes predominantly to the transverse-axial tubular system, as demonstrated by immunofluorescence and correlative immunoelectron microscopy (FluoroNanogold).","method":"Immunofluorescence, immunoelectron microscopy (FluoroNanogold), confocal microscopy","journal":"Journal of molecular and cellular cardiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ultrastructural localization by immunoelectron microscopy, single lab, functional consequences inferred","pmids":["10860776"],"is_preprint":false},{"year":2001,"finding":"Kv4.2 channels undergo both open-state and closed-state inactivation; deletion of the N-terminus (Δ2-40) slows fast and intermediate components of open-state inactivation but does not affect closed-state inactivation or recovery, establishing that N-terminal inactivation is distinct from closed-state inactivation.","method":"Site-directed mutagenesis, whole-cell patch clamp in HEK293 cells, kinetic modeling","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis with detailed kinetic analysis and simulation, multiple constructs","pmids":["11507158"],"is_preprint":false},{"year":2001,"finding":"MiRP1 (KCNE2) associates with Kv4.2 to form a stable complex (co-immunoprecipitation), slows activation and inactivation rates of Kv4.2 and shifts voltage dependence of gating positively, without affecting current amplitude; MiRP1 has no effect on Kv1.4.","method":"Xenopus oocyte expression, two-electrode voltage clamp, co-immunoprecipitation","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — co-IP plus detailed biophysical characterization in Xenopus system, single lab","pmids":["11375270"],"is_preprint":false},{"year":2002,"finding":"PSD-95 interacts with Kv4.2 via the C-terminal VSAL motif of Kv4.2 and the PDZ domains of PSD-95; PSD-95 co-expression increases surface expression and clustering of Kv4.2, an effect requiring PSD-95 palmitoylation and the intact VSAL motif.","method":"Co-immunoprecipitation, site-directed mutagenesis, biotinylation surface assay, deconvolution microscopy in mammalian cell lines","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — co-IP, mutagenesis, and surface biotinylation with functional consequence, multiple orthogonal methods","pmids":["11923279"],"is_preprint":false},{"year":2002,"finding":"PKA phosphorylation of the Kv4.2 α-subunit is necessary but not sufficient for channel modulation; the ancillary subunit KChIP3 must also be present for PKA to alter channel properties, demonstrating that PKA regulates Kv4.2 as part of a supramolecular complex.","method":"Xenopus oocyte expression, two-electrode voltage clamp, co-expression of wild-type and mutant Kv4.2 with/without KChIP3","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — electrophysiological epistasis with defined molecular components, multiple conditions tested","pmids":["12451113"],"is_preprint":false},{"year":2003,"finding":"KChIPs1-3 co-expression with Kv4.2 releases endoplasmic reticulum retention of Kv4.2 and promotes trafficking to the cell surface by masking an N-terminal hydrophobic domain of Kv4.2; KChIP co-expression also increases Kv4.2 steady-state expression, alters phosphorylation, detergent solubility, and stability. KChIP4a does not exert these effects and negatively influences other KChIPs.","method":"Co-immunoprecipitation, immunofluorescence, Western blot, surface biotinylation, subcellular fractionation in heterologous cells and native tissue","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (co-IP, biotinylation, fractionation, microscopy), replicated in native tissue","pmids":["12829703"],"is_preprint":false},{"year":2003,"finding":"Kv4.2 and KChIP2 form octameric complexes with four subunits each, as determined by purification of native Ito channels and direct amino acid analysis of subunit molar ratios.","method":"Protein purification, electron microscopy, direct amino acid analysis, biochemical stoichiometry","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — purification and direct amino acid composition analysis establish stoichiometry rigorously","pmids":["14623880"],"is_preprint":false},{"year":2003,"finding":"PSD-95, when palmitoylated, recruits Kv1.4 but not Kv4.2 into lipid rafts; a portion of Kv4.2 is nonetheless raft-associated in rat brain membranes, and Kv4.2 is found in Thy-1-containing rafts in hippocampal neurons.","method":"Lipid raft fractionation, co-immunoprecipitation, immunostaining, raft patching in heterologous cells and rat brain membranes","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple methods in native and heterologous systems, but PSD-95 does not recruit Kv4.2 to rafts (negative result for that specific mechanism)","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 gating properties but increases Kv4.2 protein levels and surface expression, thereby increasing peak A-type current amplitude and reducing neuronal excitability.","method":"In vitro kinase assay, site-directed mutagenesis, Xenopus oocyte expression, whole-cell patch clamp in hippocampal neurons with constitutively active CaMKII","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro phosphorylation with site identification by mutagenesis, confirmed electrophysiologically in native neurons","pmids":["15071113"],"is_preprint":false},{"year":2004,"finding":"DPP10 co-immunoprecipitates with Kv4.2 from oocytes; DPP10 co-expression increases Kv4.2 surface current ~5-fold, accelerates inactivation and recovery, and shifts voltage dependence of activation (~−19 mV) and inactivation (~−7 mV); the cytoplasmic N-terminal domain of DPP10 determines the acceleration of inactivation.","method":"Co-immunoprecipitation, two-electrode voltage clamp in Xenopus oocytes, N-terminal deletion constructs","journal":"Biophysical journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — co-IP plus detailed biophysical characterization with domain analysis, multiple constructs","pmids":["15454437"],"is_preprint":false},{"year":2005,"finding":"ERK/MAPK phosphorylation of Kv4.2 at T607 (mimicked by T607D mutation) causes a rightward shift in the activation curve and reduces current amplitude; this effect requires KChIP3 co-expression. The S616D mutation causes an opposite leftward shift in activation voltage.","method":"Site-directed mutagenesis (phosphomimetic), Xenopus oocyte expression, two-electrode voltage clamp, co-expression with KChIP3","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 1 / Strong — phosphomimetic mutagenesis with electrophysiological readout, dependence on KChIP3 established by epistasis","pmids":["16251476"],"is_preprint":false},{"year":2005,"finding":"Kv4.2 is transported to dendrites by the kinesin Kif17; dominant-negative Kif17 inhibits dendritic localization of both introduced and endogenous Kv4.2 but not other kinesin dominant negatives; Kv4.2 and Kif17 co-immunoprecipitate from brain lysate; the interaction involves the extreme C-terminus of Kv4.2, not the dileucine motif.","method":"Dominant-negative kinesin constructs, co-immunoprecipitation from brain and COS cells, confocal imaging in cortical neurons","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP from brain plus loss-of-function imaging with multiple dominant-negative controls","pmids":["16257958"],"is_preprint":false},{"year":2005,"finding":"Kv4.2, KChIP3, and DPP10 form ternary complexes in rat brain and in Xenopus oocytes (co-immunoprecipitation); ternary channel complexes exhibit recovery from inactivation (τrec ~18-26 ms) matching native ISA and significantly faster than binary complexes, reconstituting native neuronal A-type channel properties.","method":"Immunoprecipitation from rat brain and Xenopus oocytes, two-electrode voltage clamp in oocytes and CHO cells","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — co-IP from native brain confirmed in heterologous system, biophysical reconstitution matches native current","pmids":["16123112"],"is_preprint":false},{"year":2006,"finding":"Targeted deletion of Kv4.2 in mice eliminates dendritic A-type K+ currents in hippocampal CA1 pyramidal neurons, increases backpropagating action potential amplitude and Ca2+ influx, and lowers the threshold for LTP induction with theta burst pairing, establishing Kv4.2 as the primary determinant of dendritic A-current and a regulator of synaptic plasticity.","method":"Kv4.2 knockout mice, whole-cell and dendritic patch clamp, Ca2+ imaging, LTP induction protocols","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout with dendritic electrophysiology and Ca2+ imaging providing direct causal link","pmids":["17122039"],"is_preprint":false},{"year":2006,"finding":"Targeted deletion of Kv4.2 eliminates fast transient outward K+ current (Ito,f) in mouse ventricular myocytes, with compensatory upregulation of slow Ito (Kv1.4-encoded) and dramatic reduction of KChIP2 protein, but no ventricular hypertrophy, demonstrating Kv4.2 is essential for Ito,f and that loss of Ito,f per se is not pathological.","method":"Kv4.2 knockout mice, voltage-clamp of ventricular myocytes, Western blot, mRNA analysis","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout with electrophysiology and molecular characterization, multiple assays","pmids":["16293790"],"is_preprint":false},{"year":2006,"finding":"GRK2 phosphorylates DREAM/KChIP3 at Ser-95; this phosphorylation blocks DREAM-mediated membrane trafficking of Kv4.2 without affecting Kv4.2 tetramerization. Calcineurin de-phosphorylates GRK2-phosphorylated DREAM in vitro, and calcineurin inhibitors also block DREAM-mediated Kv4.2 surface expression.","method":"In vitro kinase assay, site-directed mutagenesis (S95D phosphomimetic), surface expression assay, calcineurin in vitro dephosphorylation, pharmacological inhibitors","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro phosphorylation with site identification plus functional consequence on channel trafficking","pmids":["17102134"],"is_preprint":false},{"year":2006,"finding":"In Kv4.2 knockout mice, KChIP expression is reduced in a region- and cell-specific pattern that precisely follows normal Kv4.2 expression levels, indicating that Kv4.2:KChIP association confers reciprocal stability on KChIP subunits.","method":"Immunohistochemistry on Kv4.2−/− mouse brains, region- and cell-specific analysis","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout with systematic IHC analysis across brain regions, single lab","pmids":["17122038"],"is_preprint":false},{"year":2007,"finding":"Kv4.2 undergoes activity-dependent internalization from dendritic spines and dendrites upon glutamate receptor stimulation in hippocampal neurons; internalization is clathrin-mediated and requires NMDA receptor activation and Ca2+ influx. LTP induced by glycine application causes synaptic insertion of GluR1 simultaneously with Kv4.2 internalization.","method":"Live imaging of EGFP-Kv4.2, whole-cell patch clamp, pharmacological blockade (clathrin inhibitors, NMDA antagonists, Ca2+ chelation), hippocampal slice cultures","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — live imaging plus electrophysiology plus pharmacological dissection, replicated in slice and dissociated cultures","pmids":["17582333"],"is_preprint":false},{"year":2007,"finding":"SAP97 interacts with Kv4.2 via the C-terminus of Kv4.2 and the PDZ domains of SAP97; SAP97 directs Kv4.2 to the postsynaptic density and spines; CaMKII-dependent phosphorylation of SAP97 regulates subcellular localization of Kv4.2.","method":"Co-immunoprecipitation, PSD fractionation, lentiviral RNAi of SAP97, pharmacological SAP97 translocation assay, immunocytochemistry in hippocampal neurons","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — co-IP, fractionation, RNAi knockdown, pharmacological manipulation, multiple orthogonal methods","pmids":["17635915"],"is_preprint":false},{"year":2007,"finding":"mGlu5 activation leads to ERK-mediated phosphorylation of Kv4.2 at Ser616 in spinal cord dorsal horn neurons, inhibiting A-type K+ currents and increasing neuronal excitability; Kv4.2 S616A mutant analysis and Kv4.2 knockout mice confirm this specific residue and channel are required for mGlu5-induced nociceptive behavior.","method":"Site-directed mutagenesis (S616A), whole-cell patch clamp in dorsal horn neurons, Kv4.2 knockout mice, pharmacological ERK inhibition, behavioral assays","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — mutagenesis identifying specific residue, genetic knockout confirming in vivo relevance, multiple orthogonal methods","pmids":["18045912"],"is_preprint":false},{"year":2008,"finding":"PKA activation induces Kv4.2 internalization from dendritic spines in hippocampal neurons; PKA inhibition prevents AMPA-induced internalization; a point mutation at Kv4.2 S552A (C-terminal PKA site) prevents AMPA-induced internalization, establishing that PKA phosphorylation at S552 is required for activity-dependent Kv4.2 trafficking.","method":"Live imaging of EGFP-Kv4.2, pharmacological PKA activation/inhibition (forskolin, 8-Br-cAMP, H89), site-directed mutagenesis (S552A), hippocampal neuron transfection","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — live imaging plus mutagenesis plus pharmacology establishing specific phosphosite requirement","pmids":["18650329"],"is_preprint":false},{"year":2008,"finding":"Gating charge (Q) immobilization in Kv4.2 at hyperpolarized voltages has the same kinetics and voltage dependence as closed-state inactivation, and both are independent of the N-terminal region; a CTX-blocked Kv4.2 channel was used to isolate gating currents, establishing that Q-immobilization and closed-state inactivation are two manifestations of the same voltage sensor desensitization process.","method":"Gating current measurements using CTX-blocked engineered Kv4.2 channels, two-electrode voltage clamp, kinetic modeling","journal":"The Journal of general physiology","confidence":"High","confidence_rationale":"Tier 1 / Strong — novel engineered channel approach to isolate gating currents, rigorous kinetic analysis with modeling","pmids":["18299396"],"is_preprint":false},{"year":2008,"finding":"ISA channels are complexes of four Kv4.2 and four DPP6 subunits; stoichiometry established by tandem-subunit constructs enforcing 4:4 and 4:2 assemblies and by direct amino acid analysis of purified complexes.","method":"Tandem-subunit constructs, protein purification, direct amino acid analysis, biophysical characterization","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct biochemical (amino acid composition) plus biophysical confirmation of 4:4 stoichiometry","pmids":["18364354"],"is_preprint":false},{"year":2009,"finding":"DPP6-S co-expression with Kv4.2 increases the unitary conductance of Kv4.2 channels from ~4 pS to ~7.5 pS (matching native CGN channels); CGN Kv4 channels from dpp6 knockout mice have conductance indistinguishable from Kv4.2 alone; charge-neutralization mutations in two N-terminal acidic residues of DPP6-S eliminate this increase, implicating electrostatic interactions.","method":"Single-channel recordings in heterologous cells and native CGNs, dpp6 knockout mice, site-directed mutagenesis of DPP6-S","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1 / Strong — single-channel analysis in native and reconstituted systems, genetic knockout, mutagenesis identifying mechanism","pmids":["19279261"],"is_preprint":false},{"year":2009,"finding":"S4-S5 linker residues (including Glu323) and S6 residue Val404 are critical for Kv4.2 closed-state inactivation; alanine-scanning mutagenesis and double-mutant cycle analysis demonstrate dynamic coupling between voltage sensors and the cytoplasmic gate underlies closed-state inactivation.","method":"Alanine-scanning mutagenesis of S4-S5 linker/S5/S6, two-electrode voltage clamp in Xenopus oocytes, double-mutant cycle analysis, selective redox modulation of double-cysteine mutants","journal":"The Journal of general physiology","confidence":"High","confidence_rationale":"Tier 1 / Strong — systematic mutagenesis with double-mutant cycle analysis and cysteine-crosslinking validation","pmids":["19171772"],"is_preprint":false},{"year":2009,"finding":"PKC directly phosphorylates Kv4.2 C-terminus at Ser447 and Ser537 in vitro; phosphorylation at Ser537 is increased in hippocampus upon PKC activation; mutation of both PKC sites to alanine increases surface expression of Kv4.2. Furthermore, prior PKC phosphorylation enhances subsequent ERK phosphorylation of Kv4.2 in vitro, establishing Kv4.2 as a locus for PKC-ERK cross-talk.","method":"In vitro PKC kinase assay with GST-fusion proteins, site-directed mutagenesis, surface biotinylation, phospho-selective antibody, in vitro sequential kinase assay","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro phosphorylation with site identification, mutagenesis, surface expression assay, and cross-talk demonstrated in vitro","pmids":["18795890"],"is_preprint":false},{"year":2009,"finding":"CaV3.1 (T-type Ca2+ channel) associates with the Kv4.2-KChIP3-DPP10c complex and Ca2+ entry through CaV3.1 shifts Kv4.2 inactivation voltage; this regulation is selective to CaV3 isoforms and not observed with CaV1.4, CaV2.1, or CaV2.3.","method":"Co-expression in heterologous cells, electrophysiology, calcium channel pharmacology","journal":"Channels (Austin, Tex.)","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — functional epistasis in heterologous system, single lab, mechanism partially characterized","pmids":["20458163"],"is_preprint":false},{"year":2010,"finding":"KChIP4a enhances stabilization and membrane expression of Kv4.2 via a mechanism requiring PKA phosphorylation of Kv4.2 at S552; other KChIP isoforms enhance Kv4.2 surface expression and stability without requiring S552 phosphorylation. A-kinase anchoring proteins (AKAPs) are identified as Kv4.2 binding partners.","method":"Co-immunoprecipitation, surface biotinylation, pulse-chase stability assays, site-directed mutagenesis (S552A), co-expression in hippocampal neurons","journal":"Molecular and cellular neurosciences","confidence":"High","confidence_rationale":"Tier 2 / Moderate — co-IP, surface biotinylation, mutagenesis, multiple isoform comparisons in single lab","pmids":["20045463"],"is_preprint":false},{"year":2010,"finding":"Glutamate-induced downregulation of Kv4.2 is mediated specifically by NR2B-containing extrasynaptic NMDA receptors (not synaptic NMDA receptors); Ca2+ influx through NR2B-NMDA receptors activates calpain, which degrades Kv4.2 protein, reducing Kv4.2 clusters and causing a hyperpolarizing shift in A-current inactivation.","method":"Whole-cell patch clamp, immunocytochemistry, Western blot, pharmacological NR2B antagonists, calpain inhibitors, selective synaptic vs. extrasynaptic NMDA receptor stimulation protocols","journal":"Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — pharmacological dissection with multiple antagonists, electrophysiology, and protein analysis; single lab with multiple orthogonal methods","pmids":["19857555"],"is_preprint":false},{"year":2011,"finding":"Quantitative immunogold freeze-fracture replica labeling (SDS-FRL) reveals only ~70% increase in Kv4.2 immunogold density along the proximo-distal axis of CA1 apical dendrites (not the 6-fold gradient predicted by electrophysiology), found similarly in main apical dendrites, oblique dendrites, and dendritic spines; no Kv4.2 labeling in presynaptic axons.","method":"SDS-digested freeze-fracture replica labeling (SDS-FRL), high-resolution quantitative immunogold EM, confirmed with Kv4.2−/− tissue as negative control","journal":"The European journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1 / Strong — quantitative ultrastructural immunogold method validated with knockout negative control","pmids":["22098631"],"is_preprint":false},{"year":2012,"finding":"DPP6 expression in mouse cortex is unaffected by Kv4.2 and/or Kv4.3 deletion, and DPP6/DPP10 localize to the cell surface independently of Kv4.2; DPP6/DPP10 selectively stabilize cell-surface Kv4.2 protein without affecting total or surface DPP6/DPP10 levels; further addition of KChIP3 in the presence of DPP10 markedly increases both total and surface Kv4.2.","method":"Kv4.2/Kv4.3 knockout mice, Western blot, surface biotinylation, heterologous co-expression","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockouts combined with biochemical surface expression assays and heterologous reconstitution","pmids":["22311982"],"is_preprint":false},{"year":2014,"finding":"A de novo KCND2 missense mutation (p.Val404Met) found in twins with autism and epilepsy causes significantly slowed inactivation of Kv4.2 channels, either alone or co-expressed with wild-type, consistent with dominant gain-of-function; the effect on closed-state inactivation is preserved in the presence of auxiliary subunits.","method":"Whole-exome sequencing, heterologous expression in HEK cells, whole-cell patch clamp, wild-type/mutant co-expression","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — direct electrophysiological characterization of mutant channel, dominant effect confirmed by co-expression","pmids":["24501278"],"is_preprint":false},{"year":2015,"finding":"PACAP/PAC1 receptor activation leads to phosphorylation of Kv4.2 and downregulation of surface channel density via convergent PKA and ERK1/2 signaling; PKA-induced effects on Kv4.2 require ERK1/2 phosphorylation of the channel at two specific residues but not direct PKA phosphorylation, establishing a GPCR-channel signaling cascade.","method":"Whole-cell patch clamp in hippocampal neurons, surface biotinylation, pharmacological inhibitors of PKA and ERK, identification of phosphorylation sites","journal":"Neuropharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — electrophysiology plus surface biotinylation plus pharmacological dissection, single lab","pmids":["26456351"],"is_preprint":false},{"year":2015,"finding":"H2S inhibits Kv4.2-mediated Ito by targeting a Cys320/Cys529 disulfide motif; mutation of either residue blocks the H2S effect; H2S breaks the disulfide bridge between oxidized cysteine residues but does not modify single cysteines, establishing a specific redox regulatory mechanism.","method":"Site-directed mutagenesis (C320A, C529A), whole-cell patch clamp in cardiomyocytes and heterologous cells, pharmacological H2S application","journal":"Antioxidants & redox signaling","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mutagenesis with electrophysiological validation identifying specific cysteine residues, single lab","pmids":["25756524"],"is_preprint":false},{"year":2016,"finding":"miR-324-5p directly inhibits Kv4.2 protein expression by binding to KCND2 mRNA (recruited to RISC after status epilepticus); antagonizing miR-324-5p is seizure-suppressive and neuroprotective in wild-type but not Kcnd2 knockout mice, placing miR-324-5p-mediated Kv4.2 silencing in the seizure onset pathway.","method":"RISC immunoprecipitation, miRNA mimic/antagomir transfection, in vivo kainic acid seizure model, Kcnd2 knockout genetic epistasis, Western blot","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — RISC IP, genetic epistasis with knockout, in vivo and in vitro experiments converging on same mechanism","pmids":["27681419"],"is_preprint":false},{"year":2018,"finding":"The V404M (Val404Met) mutation in Kv4.2 specifically enhances closed-state inactivation (CSI) of channels that have not opened while profoundly impairing inactivation of channels that have opened; the mutation increases stability of the inactivated state and slows closure of open channels (required for CSI); the larger volume of methionine vs valine is a major factor; physical coupling between voltage sensor and pore gate is maintained in the inactivated state.","method":"Whole-cell patch clamp in Xenopus oocytes with detailed kinetic analysis, comparison of closed-state vs open-state inactivation, auxiliary subunit co-expression, structural interpretation","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — rigorous biophysical dissection of state-dependent effects with multiple protocols and kinetic modeling","pmids":["29581270"],"is_preprint":false},{"year":2018,"finding":"A gain-of-function KCND2 mutation p.S447R causes nocturnal paroxysmal atrial fibrillation; the mutation increases the Kv4.2 inactivation time constant and impairs PKC-dependent regulation of Kv4.2 membrane expression (S447 is a PKC phosphorylation site), resulting in augmented channel surface expression and enhanced Ito in both homotetrameric Kv4.2 and heterotetrameric Kv4.2-Kv4.3 channels.","method":"Whole-exome sequencing, linkage analysis, Xenopus oocyte electrophysiology, co-expression of mutant and wild-type, hybrid Kv4.2-Kv4.3 chimeric channels","journal":"Circulation. Genomic and precision medicine","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — electrophysiological characterization of mutant in multiple channel compositions, mechanistic explanation via PKC site","pmids":["30571183"],"is_preprint":false},{"year":2020,"finding":"Activity-induced phosphorylation of Kv4.2 at pThr607-Pro triggers binding of Pin1 (peptidyl-prolyl cis-trans isomerase), which isomerizes Kv4.2 at this motif, causing dissociation of the Kv4.2-DPP6 complex; mice with Kv4.2 T607A knock-in show altered Kv4.2-DPP6 interaction, increased A-type K+ current, reduced CA1 pyramidal neuron excitability, and improved reversal learning.","method":"Pin1 binding assays, Kv4.2 T607A knock-in mice, co-immunoprecipitation, whole-cell patch clamp in CA1 neurons, Morris water maze and lever press behavioral assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — knock-in mouse model with co-IP, electrophysiology, and behavior; multiple orthogonal methods establishing mechanism","pmids":["32218435"],"is_preprint":false},{"year":2020,"finding":"GSK3β directly phosphorylates Kv4.2 at Ser616 in nucleus accumbens medium spiny neurons; GSK3β-mediated phosphorylation inhibits Kv4.2 channel activity and underlies augmented spike-timing-dependent LTP in chronic mild stress mice; GSK3β knockdown prevents both LTP changes and depressive-like behavior.","method":"AAV2-shRNA knockdown of GSK3β, whole-cell patch clamp, immunohistochemistry, pharmacological Kv4.2 inhibition, biochemical phosphorylation analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockdown plus pharmacological and biochemical evidence, multiple orthogonal methods converging on specific residue and behavior","pmids":["32209671"],"is_preprint":false},{"year":2005,"finding":"The N-terminal proximal region (residues 11-23) of Kv4.2 is the major KChIP interaction site; T1 domain residues and C-terminal truncations also affect KChIP2 binding and gating modulation; binding and functional modulation are tightly coupled at the N-terminal site but more loosely coupled at T1 and C-terminal sites.","method":"Lysine-scanning and structure-based mutagenesis, co-immunoprecipitation, whole-cell patch clamp in mammalian cells","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — systematic mutagenesis with paired biochemical and electrophysiological readouts, multiple interaction sites characterized","pmids":["16096338"],"is_preprint":false},{"year":2004,"finding":"Mossy fiber synaptic contact and glutamatergic activity (NMDA and/or AMPA receptor activation) are required for targeting Kv4.2 channels from the soma to dendrites and synaptic sites in cerebellar granule cells; glutamate receptor activation in monocultures (without synapse formation) is sufficient to induce dendritic targeting.","method":"Co-culture of granule cells with pontine grey nucleus cells, confocal imaging, pharmacological blockade of NMDA/AMPA receptors","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — activity-dependent targeting demonstrated with pharmacological intervention and co-culture system, single lab","pmids":["15140189"],"is_preprint":false},{"year":2003,"finding":"Actin depolymerization by cytochalasin D increases Kv4.2 current density ~7-fold in HEK cells by increasing the number and focal clustering of channels at the cell surface, without changing voltage dependence, single-channel conductance, or open probability.","method":"Whole-cell and single-channel patch clamp, cytochalasin D treatment, surface imaging, confocal microscopy in HEK cells","journal":"American journal of physiology. Heart and circulatory physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — electrophysiology at macroscopic and single-channel level plus imaging, single lab in heterologous cells","pmids":["14551056"],"is_preprint":false},{"year":2009,"finding":"DPPX-S co-expression with Kv4.2 causes a −26 mV shift in the gating charge-voltage relationship and accelerates outward gating charge movement; DPPX-S has no effect on Shaker B gating currents, establishing that DPPX-S specifically remodels Kv4.2 voltage-sensor dynamics through destabilization of resting/intermediate states.","method":"Gating current measurements (CTX-blocked engineered Kv4.2 channel system), two-electrode voltage clamp in Xenopus oocytes","journal":"The Journal of general physiology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct gating current measurement with appropriate controls (Shaker), single lab but rigorous method","pmids":["17130523"],"is_preprint":false},{"year":2009,"finding":"DPPX-S and KChIP auxiliary subunits, despite distinct structures, exert similar effects on Kv4.2 trafficking (releasing ER retention, promoting plasma membrane expression, altering phosphorylation and stability); KChIP4a inhibits both DPPX-S and other KChIP effects, consistent with ternary complex formation early in biosynthesis; tandem MS reveals co-expression with either DPPX-S or KChIP2 generates similar Kv4.2 phosphorylation patterns matching brain.","method":"Heterologous co-expression, Western blot, immunofluorescence, tandem mass spectrometry phosphoproteomics","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — MS phosphoproteomics combined with trafficking assays and multiple subunit comparisons","pmids":["19441798"],"is_preprint":false}],"current_model":"Kv4.2 is the principal pore-forming α-subunit of somatodendritic A-type (ISA/IA) and cardiac fast transient outward (Ito,f) K+ channels; it assembles as an octameric 4:4 complex with KChIP auxiliary subunits (with KChIPs releasing ER retention and stabilizing surface expression) and as a 4:4 complex with DPP6/DPP10 transmembrane subunits (which remodel voltage-sensor gating dynamics and increase unitary conductance), forming ternary complexes whose inactivation kinetics match native ISA; channel surface density and gating are bidirectionally regulated by direct phosphorylation at multiple sites by ERK (T602, T607, S616), PKA (T38, S552), CaMKII (S438, S459), and PKC (S447, S537), and by redox modification of Cys320/Cys529; activity-dependent internalization requires NMDA receptor activation, Ca2+ influx, clathrin, and PKA phosphorylation at S552, while dendritic targeting depends on the kinesin Kif17 and on synaptic glutamate receptor activity; Pin1-mediated prolyl isomerization at pThr607 dissociates the Kv4.2-DPP6 complex to regulate neuronal excitability and cognitive flexibility; loss of Kv4.2-encoded dendritic A-current enhances backpropagating action potential amplitude, lowers LTP threshold, and increases seizure susceptibility, while gain-of-function mutations cause epilepsy, autism, and atrial fibrillation."},"narrative":{"mechanistic_narrative":"KCND2 encodes Kv4.2, the principal pore-forming α-subunit of fast-inactivating A-type (ISA) K+ channels in neurons and the fast transient outward current (Ito,f) in cardiac myocytes, where genetic deletion eliminates these currents and establishes Kv4.2 as their primary molecular determinant [PMID:17122039, PMID:16293790]. The cloned channel activates rapidly, inactivates with millisecond kinetics, and is 4-AP-sensitive but TEA- and dendrotoxin-insensitive [PMID:1722463]; it undergoes distinct open-state and closed-state inactivation, the latter reflecting voltage-sensor desensitization (gating-charge immobilization) coupled through the S4-S5 linker and S6 to the cytoplasmic gate [PMID:11507158, PMID:18299396, PMID:19171772]. Native channels are macromolecular assemblies: Kv4.2 forms octameric 4:4 complexes with cytoplasmic KChIP subunits and with transmembrane DPP6/DPP10 subunits [PMID:14623880, PMID:18364354]. KChIPs bind the Kv4.2 N-terminus to mask an ER-retention signal and promote surface trafficking and reciprocal subunit stabilization [PMID:12829703, PMID:17122038, PMID:16096338], while DPP6/DPP10 accelerate inactivation, remodel voltage-sensor gating, and increase unitary conductance; ternary Kv4.2-KChIP-DPP complexes reconstitute native ISA kinetics [PMID:15454437, PMID:16123112, PMID:19279261, PMID:17130523]. Channel surface density and gating are tuned by direct phosphorylation by ERK (T602/T607/S616), PKA (T38/S552), CaMKII (S438/S459), and PKC (S447/S537), with several effects requiring KChIP co-assembly and with cross-talk between kinases [PMID:11080179, PMID:10681507, PMID:15071113, PMID:16251476, PMID:18795890]. Trafficking is further controlled by activity-dependent, NMDA-receptor- and Ca2+-driven clathrin-mediated internalization requiring PKA phosphorylation at S552, by Kif17-dependent dendritic transport, by NR2B-NMDAR/calpain-mediated degradation, and by Pin1 prolyl isomerization at pThr607 that dissociates the Kv4.2-DPP6 complex to regulate excitability and learning [PMID:16257958, PMID:17582333, PMID:18650329, PMID:19857555, PMID:32218435]. Loss of Kv4.2 A-current enhances backpropagating action potentials and lowers the LTP threshold [PMID:17122039], and gain-of-function KCND2 mutations cause autism with epilepsy (V404Met, via altered closed-state inactivation) and paroxysmal atrial fibrillation (S447R, via impaired PKC regulation and augmented surface Ito) [PMID:24501278, PMID:29581270, PMID:30571183].","teleology":[{"year":1991,"claim":"Established that KCND2 encodes a functional voltage-gated A-type K+ channel with a defined kinetic and pharmacological fingerprint, providing the molecular identity for native rapidly inactivating currents.","evidence":"Two-electrode voltage-clamp of cloned RK5/Kv4.2 in Xenopus oocytes","pmids":["1722463"],"confidence":"High","gaps":["Did not establish which native currents Kv4.2 carries in vivo","No auxiliary subunit context"]},{"year":1996,"claim":"Defined the intracellular, closed-state mechanism of 4-AP block and its mutual exclusivity with inactivation, linking the drug site to the inactivation machinery.","evidence":"State-dependent pharmacological voltage-clamp analysis in oocytes","pmids":["8930194"],"confidence":"High","gaps":["Exact molecular residues of the 4-AP site not mapped"]},{"year":1997,"claim":"Demonstrated that Kv4 subunits are the predominant carriers of neuronal A-current and cardiac Ito, moving Kv4.2 from a cloned channel to a physiological current determinant.","evidence":"Adenoviral dominant-negative Kv4.2 in cerebellar granule cells and ventricular myocytes","pmids":["9395498"],"confidence":"High","gaps":["Dominant-negative suppresses all Kv4 members, not Kv4.2-specific","Subunit composition of native channels unresolved at this stage"]},{"year":2000,"claim":"Identified the cytoskeletal and trafficking partners and the first kinase inputs to Kv4.2, establishing the channel as a regulated, scaffolded protein rather than a static pore.","evidence":"Yeast two-hybrid/co-IP for filamin; in vitro kinase assays with phosphosite mapping for ERK and PKA","pmids":["11102480","11080179","10681507"],"confidence":"High","gaps":["Functional consequence of individual phosphosites not yet resolved","In vivo phosphorylation stoichiometry unknown"]},{"year":2002,"claim":"Showed that PSD-95 clusters and stabilizes Kv4.2 at the surface and that kinase regulation requires auxiliary subunits, establishing that Kv4.2 is regulated as part of a supramolecular complex.","evidence":"Co-IP, VSAL-motif mutagenesis, surface biotinylation, and PKA epistasis with KChIP3 in oocytes","pmids":["11923279","12451113"],"confidence":"High","gaps":["Stoichiometry of the complex not yet defined","Whether PSD-95 acts in native neurons not directly tested"]},{"year":2003,"claim":"Defined KChIP function and established 4:4 channel stoichiometry, explaining how cytoplasmic subunits release ER retention and build the native octameric Ito channel.","evidence":"Surface biotinylation/fractionation/co-IP for KChIP trafficking; purification and amino acid analysis for Kv4.2:KChIP2 4:4 stoichiometry","pmids":["12829703","14623880"],"confidence":"High","gaps":["Did not address DPP subunit incorporation","KChIP4a inhibitory mechanism not fully resolved"]},{"year":2004,"claim":"Established CaMKII as a phosphorylation input that increases Kv4.2 protein and surface expression, and identified DPP10 as a transmembrane partner that dramatically increases surface current and accelerates gating.","evidence":"In vitro kinase assay with site mutagenesis (CaMKII); co-IP and voltage-clamp with N-terminal deletions (DPP10)","pmids":["15071113","15454437"],"confidence":"High","gaps":["Native ternary complex composition not yet shown","CaMKII mechanism of stabilization unknown"]},{"year":2005,"claim":"Reconstituted native A-type channel kinetics from a defined ternary Kv4.2-KChIP3-DPP10 complex, identified Kif17 as the dendritic transport motor, and mapped KChIP interaction sites and phosphomimetic gating effects.","evidence":"Co-IP from brain plus voltage-clamp reconstitution; dominant-negative kinesin with co-IP; lysine-scanning mutagenesis; phosphomimetic mutants with KChIP3 epistasis","pmids":["16123112","16257958","16096338","16251476"],"confidence":"High","gaps":["How transport, assembly, and phosphorylation are coordinated in vivo unresolved"]},{"year":2006,"claim":"Used genetic knockout to prove Kv4.2 is the primary determinant of dendritic A-current and cardiac Ito,f, linking it causally to synaptic plasticity threshold and reciprocal KChIP stability.","evidence":"Kv4.2 knockout mice with dendritic patch clamp, Ca2+ imaging, LTP protocols, myocyte voltage-clamp, and IHC","pmids":["17122039","16293790","17122038","17102134"],"confidence":"High","gaps":["Compensatory remodeling complicates interpretation of cardiac phenotype","Whether reduced LTP threshold causes behavioral change not addressed here"]},{"year":2007,"claim":"Established activity-dependent trafficking control of Kv4.2 and additional scaffolding/signaling routes coupling synaptic activity to channel surface density and excitability.","evidence":"Live imaging plus pharmacology (clathrin/NMDAR/Ca2+) for internalization; SAP97 co-IP/RNAi; mGlu5-ERK-S616 with S616A mutant and knockout behavior","pmids":["17582333","17635915","18045912"],"confidence":"High","gaps":["Endocytic adaptor proteins linking phosphorylation to clathrin not identified","Coupling between internalization and degradation pathways unclear"]},{"year":2008,"claim":"Pinpointed PKA phosphorylation at S552 as the trigger for activity-dependent internalization and clarified that closed-state inactivation is voltage-sensor desensitization independent of the N-terminus.","evidence":"Live imaging with S552A mutant and PKA pharmacology; gating-current measurements from CTX-blocked engineered channels","pmids":["18650329","18299396"],"confidence":"High","gaps":["Downstream endocytic machinery recognizing pS552 unknown"]},{"year":2009,"claim":"Dissected the biophysical basis of DPP-subunit modulation (conductance, voltage-sensor remodeling), the structural determinants of closed-state inactivation, the PKC phosphorylation input with PKC-ERK cross-talk, and CaV3.1 coupling.","evidence":"Single-channel recordings with dpp6 knockout; gating currents with DPPX-S; alanine-scanning/double-mutant cycles; in vitro PKC kinase and sequential kinase assays; co-expression electrophysiology with CaV3.1","pmids":["19279261","17130523","19171772","18795890","20458163","19441798"],"confidence":"High","gaps":["CaV3.1 coupling shown only in heterologous cells","Structural mechanism of DPP conductance increase inferred from electrostatics, not structure"]},{"year":2010,"claim":"Resolved isoform-specific KChIP trafficking requirements (KChIP4a requires S552 phosphorylation; AKAPs as partners) and identified extrasynaptic NR2B-NMDAR/calpain proteolysis as a degradative downregulation pathway.","evidence":"Co-IP, surface biotinylation, pulse-chase with S552A mutant; pharmacological NR2B and calpain dissection with protein analysis","pmids":["20045463","19857555"],"confidence":"High","gaps":["Calpain cleavage sites on Kv4.2 not mapped","AKAP identity not specified"]},{"year":2011,"claim":"Quantified the actual Kv4.2 dendritic distribution by immunogold EM, revealing a shallower proximo-distal gradient than electrophysiology predicted.","evidence":"SDS-FRL quantitative immunogold EM validated with Kv4.2 knockout negative control","pmids":["22098631"],"confidence":"High","gaps":["Discrepancy between channel density and functional A-current gradient unexplained","Does not address channel open probability or auxiliary subunit distribution"]},{"year":2014,"claim":"Provided the first human disease link, showing a de novo KCND2 gain-of-function mutation causes autism with epilepsy through slowed inactivation.","evidence":"Whole-exome sequencing of affected twins plus HEK-cell voltage-clamp of V404M with wild-type co-expression","pmids":["24501278"],"confidence":"High","gaps":["In vivo neuronal consequences of V404M not tested","Genotype-phenotype generalizability limited to single family"]},{"year":2015,"claim":"Defined GPCR-to-channel signaling convergence (PACAP/PAC1 via PKA+ERK) and a specific cardiac redox regulatory mechanism through a Cys320/Cys529 disulfide.","evidence":"Patch clamp with PKA/ERK inhibitors and biotinylation; C320A/C529A mutagenesis with H2S application in cardiomyocytes","pmids":["26456351","25756524"],"confidence":"Medium","gaps":["PACAP cascade characterized in single lab","Physiological source of the disulfide oxidation in vivo unclear"]},{"year":2016,"claim":"Placed post-transcriptional Kv4.2 silencing by miR-324-5p in the seizure-onset pathway, validated by genetic epistasis.","evidence":"RISC IP, antagomir, kainic acid seizure model, and Kcnd2 knockout epistasis","pmids":["27681419"],"confidence":"High","gaps":["Other targets of miR-324-5p may contribute to seizure phenotype"]},{"year":2018,"claim":"Mechanistically resolved the V404M epilepsy/autism mutation as enhancing closed-state inactivation while impairing open-channel inactivation, and identified an S447R gain-of-function mutation causing atrial fibrillation via disrupted PKC regulation.","evidence":"Detailed kinetic voltage-clamp of V404M closed- vs open-state inactivation; WES/linkage plus oocyte electrophysiology of S447R in homo- and heterotetramers","pmids":["29581270","30571183"],"confidence":"High","gaps":["No high-resolution structure confirming the proposed steric mechanism","S447R cardiac phenotype not modeled in vivo"]},{"year":2020,"claim":"Identified Pin1 prolyl isomerization at pThr607 as a switch dissociating the Kv4.2-DPP6 complex, and GSK3β phosphorylation at S616 as a stress-related regulator of plasticity and behavior, linking channel regulation to cognition and mood.","evidence":"T607A knock-in mice with co-IP, patch clamp, and behavior (Pin1); AAV-shRNA GSK3β knockdown with patch clamp and behavior","pmids":["32218435","32209671"],"confidence":"High","gaps":["Whether Pin1 and GSK3β pathways intersect at overlapping C-terminal sites not tested","Therapeutic targeting not explored"]},{"year":null,"claim":"A high-resolution structure of the assembled Kv4.2-KChIP-DPP ternary complex and an integrated model reconciling channel density, phosphorylation state, and the functional A-current gradient remain to be established.","evidence":"","pmids":[],"confidence":"High","gaps":["No experimental structure of the native octameric ternary complex in the corpus","Quantitative reconciliation of immunogold density with functional current gradient unresolved","Coordinated logic of multi-kinase phosphorylation in vivo not integrated"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,2,21,22]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3,8,11,13,37]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[13,51]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[7,49]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[21,25,27,45]},{"term_id":"R-HSA-397014","term_label":"Muscle contraction","supporting_discovery_ids":[22,44]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[39,43,44,42]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[13,19,25,28]}],"complexes":["Kv4.2-KChIP (4:4 octameric A-type/Ito channel)","Kv4.2-DPP6 (4:4 ISA channel)","Kv4.2-KChIP3-DPP10 ternary channel complex"],"partners":["KCNIP2","KCNIP3","DPP6","DPP10","DLG4","DLG1","KIF17","FLNA"],"other_free_text":[]}},"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":278,"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":272,"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":253,"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":219,"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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sciences","url":"https://pubmed.ncbi.nlm.nih.gov/30634540","citation_count":30,"is_preprint":false},{"pmid":"23703525","id":"PMC_23703525","title":"Neuregulin-1/ErbB4 signaling regulates Kv4.2-mediated transient outward K+ current through the Akt/mTOR pathway.","date":"2013","source":"American journal of physiology. Cell physiology","url":"https://pubmed.ncbi.nlm.nih.gov/23703525","citation_count":29,"is_preprint":false},{"pmid":"12843309","id":"PMC_12843309","title":"Quantitative relationship between Kv4.2 mRNA and A-type K+ current in rat striatal cholinergic interneurons during development.","date":"2003","source":"Journal of neurophysiology","url":"https://pubmed.ncbi.nlm.nih.gov/12843309","citation_count":29,"is_preprint":false},{"pmid":"15140189","id":"PMC_15140189","title":"Mossy fibre contact triggers the targeting of Kv4.2 potassium channels to dendrites and synapses in developing cerebellar granule neurons.","date":"2004","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15140189","citation_count":29,"is_preprint":false},{"pmid":"30571183","id":"PMC_30571183","title":"Nocturnal Atrial Fibrillation Caused by Mutation in KCND2, Encoding Pore-Forming (α) Subunit of the Cardiac Kv4.2 Potassium Channel.","date":"2018","source":"Circulation. Genomic and precision medicine","url":"https://pubmed.ncbi.nlm.nih.gov/30571183","citation_count":28,"is_preprint":false},{"pmid":"29467627","id":"PMC_29467627","title":"Basal Ganglia Neuromodulation Over Multiple Temporal and Structural Scales-Simulations of Direct Pathway MSNs Investigate the Fast Onset of Dopaminergic Effects and Predict the Role of Kv4.2.","date":"2018","source":"Frontiers in neural circuits","url":"https://pubmed.ncbi.nlm.nih.gov/29467627","citation_count":28,"is_preprint":false},{"pmid":"19453640","id":"PMC_19453640","title":"Arachidonic acid potently inhibits both postsynaptic-type Kv4.2 and presynaptic-type Kv1.4 IA potassium channels.","date":"2009","source":"The European journal of neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/19453640","citation_count":28,"is_preprint":false},{"pmid":"22311982","id":"PMC_22311982","title":"Augmentation of Kv4.2-encoded currents by accessory dipeptidyl peptidase 6 and 10 subunits reflects selective cell surface Kv4.2 protein stabilization.","date":"2012","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22311982","citation_count":28,"is_preprint":false},{"pmid":"19857555","id":"PMC_19857555","title":"Downregulation of Kv4.2 channels mediated by NR2B-containing NMDA receptors in cultured hippocampal neurons.","date":"2010","source":"Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/19857555","citation_count":27,"is_preprint":false},{"pmid":"16426762","id":"PMC_16426762","title":"Pituitary adenylate cyclase activating polypeptide reduces expression of Kv1.4 and Kv4.2 subunits underlying A-type K(+) current in adult mouse olfactory neuroepithelia.","date":"2006","source":"Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/16426762","citation_count":27,"is_preprint":false},{"pmid":"20483361","id":"PMC_20483361","title":"High-mobility group box 1 (HMGB1) downregulates cardiac transient outward potassium current (Ito) through downregulation of Kv4.2 and Kv4.3 channel transcripts and proteins.","date":"2010","source":"Journal of molecular and cellular cardiology","url":"https://pubmed.ncbi.nlm.nih.gov/20483361","citation_count":27,"is_preprint":false},{"pmid":"24486512","id":"PMC_24486512","title":"Type 2 diabetes induces subendocardium-predominant reduction in transient outward K+ current with downregulation of Kv4.2 and KChIP2.","date":"2014","source":"American journal of physiology. Heart and circulatory physiology","url":"https://pubmed.ncbi.nlm.nih.gov/24486512","citation_count":26,"is_preprint":false},{"pmid":"26456351","id":"PMC_26456351","title":"Convergent phosphomodulation of the major neuronal dendritic potassium channel Kv4.2 by pituitary adenylate cyclase-activating polypeptide.","date":"2015","source":"Neuropharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/26456351","citation_count":26,"is_preprint":false},{"pmid":"15208026","id":"PMC_15208026","title":"Modulation of Kv4.2 channels by a peptide isolated from the venom of the giant bird-eating tarantula Theraphosa leblondi.","date":"2004","source":"Toxicon : official journal of the International Society on Toxinology","url":"https://pubmed.ncbi.nlm.nih.gov/15208026","citation_count":26,"is_preprint":false},{"pmid":"18363830","id":"PMC_18363830","title":"Regulation of Kv4.2 channels by glutamate in cultured hippocampal neurons.","date":"2008","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/18363830","citation_count":25,"is_preprint":false},{"pmid":"25756524","id":"PMC_25756524","title":"Hydrogen Sulfide Targets the Cys320/Cys529 Motif in Kv4.2 to Inhibit the Ito Potassium Channels in Cardiomyocytes and Regularizes Fatal Arrhythmia in Myocardial Infarction.","date":"2015","source":"Antioxidants & redox signaling","url":"https://pubmed.ncbi.nlm.nih.gov/25756524","citation_count":25,"is_preprint":false},{"pmid":"19441798","id":"PMC_19441798","title":"Convergent modulation of Kv4.2 channel alpha subunits by structurally distinct DPPX and KChIP auxiliary subunits.","date":"2009","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/19441798","citation_count":24,"is_preprint":false},{"pmid":"34418280","id":"PMC_34418280","title":"Long noncoding RNA FAM66C promotes tumor progression and glycolysis in intrahepatic cholangiocarcinoma by regulating hsa-miR-23b-3p/KCND2 axis.","date":"2021","source":"Environmental toxicology","url":"https://pubmed.ncbi.nlm.nih.gov/34418280","citation_count":23,"is_preprint":false},{"pmid":"29214635","id":"PMC_29214635","title":"Kv4.2 channel activity controls intrinsic firing dynamics of arcuate kisspeptin neurons.","date":"2018","source":"The Journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/29214635","citation_count":23,"is_preprint":false},{"pmid":"14551056","id":"PMC_14551056","title":"Increased focal Kv4.2 channel expression at the plasma membrane is the result of actin depolymerization.","date":"2003","source":"American journal of physiology. Heart and circulatory physiology","url":"https://pubmed.ncbi.nlm.nih.gov/14551056","citation_count":23,"is_preprint":false},{"pmid":"12721103","id":"PMC_12721103","title":"Effects of flecainide and quinidine on Kv4.2 currents: voltage dependence and role of S6 valines.","date":"2003","source":"British journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/12721103","citation_count":23,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":56337,"output_tokens":12799,"usd":0.180498,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":24182,"output_tokens":6195,"usd":0.137893,"stage2_stop_reason":"end_turn"},"total_usd":0.318391,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1991,\n      \"finding\": \"Kv4.2 (RK5) encodes a voltage-sensitive A-type K+ channel that activates rapidly, inactivates with time constants of 15 and 60 ms, is sensitive to 4-AP (IC50 ~5 mM), and is insensitive to TEA and dendrotoxins, as demonstrated by heterologous expression in Xenopus oocytes.\",\n      \"method\": \"Two-electrode voltage-clamp in Xenopus oocytes\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro electrophysiological characterization of cloned channel, replicated across multiple subsequent studies\",\n      \"pmids\": [\"1722463\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"4-AP blocks Kv4.2 channels exclusively from the intracellular side in the closed state; binding and channel inactivation are mutually exclusive, indicating the 4-AP binding site is at or adjacent to the 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 / Strong — detailed kinetic and state-dependent pharmacological analysis with multiple voltage protocols\",\n      \"pmids\": [\"8930194\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Dominant-negative truncated Kv4.2 (Kv4.2ST, truncated after the first transmembrane segment) suppresses A-type currents in cerebellar granule cells and transient outward current (Ito) in rat ventricular myocytes when delivered by adenoviral gene transfer, demonstrating that Kv4 family subunits are the predominant contributors to these currents.\",\n      \"method\": \"Adenoviral dominant-negative overexpression, whole-cell patch clamp, cotransfection in CHO-K1 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — dominant-negative construct with electrophysiological validation in both heterologous cells and native neurons/myocytes\",\n      \"pmids\": [\"9395498\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Kv4.2 protein is clustered at the postsynaptic membrane of supraoptic nucleus neurons, specifically concentrated at synaptic contacts on somata and dendrites, as shown by immunoelectron microscopy.\",\n      \"method\": \"Confocal and immunoelectron microscopy\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ultrastructural localization by immunoelectron microscopy, single lab, no functional consequence directly demonstrated\",\n      \"pmids\": [\"9070739\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Kvβ1.2 co-expression with Kv4.2 in HEK293 cells confers sensitivity to redox modulation and hypoxia to Kv4.2 channels; this O2 sensitivity is membrane-delimited and involves a hemoproteic O2 sensor, and is not observed with Shaker channels co-expressed with Kvβ1.2.\",\n      \"method\": \"Transfection in HEK293 cells, whole-cell patch clamp, cell-free patches, pharmacological redox agents\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — multiple orthogonal methods (cell-attached, inside-out patches, pharmacology) in single lab demonstrating mechanism\",\n      \"pmids\": [\"10352037\"],\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 determined by in vitro kinase assays on GST-fusion proteins and phosphopeptide mapping, and ERK-phosphorylated Kv4.2 is detected in rat hippocampus in vivo.\",\n      \"method\": \"In vitro kinase assay with GST-fusion proteins, phosphopeptide mapping, amino acid sequencing, phospho-selective antibodies, COS-7 cell transfection\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro phosphorylation with site identification confirmed by multiple methods and validated 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 phosphorylation of GST-fusion proteins, phosphopeptide mapping, and confirmed in COS-7 cells and in rat hippocampal area CA1.\",\n      \"method\": \"In vitro PKA kinase assay with GST-fusion proteins, phosphopeptide mapping, amino acid sequencing, phospho-selective antibodies, COS-7 cell transfection\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro phosphorylation with site identification by sequencing, confirmed in intact cells and native tissue\",\n      \"pmids\": [\"10681507\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Kv4.2 directly interacts with the actin-binding protein filamin via yeast two-hybrid and co-immunoprecipitation from brain and in vitro; this interaction localizes Kv4.2 to filopodial roots in filamin+ cells and increases whole-cell Kv4.2 current density ~2.7-fold compared to filamin− 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 / Strong — reciprocal co-IP from brain, yeast two-hybrid, and functional electrophysiological consequence in matched cell lines\",\n      \"pmids\": [\"11102480\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Kv4.2 protein in rat ventricular myocytes localizes predominantly to the transverse-axial tubular system, as demonstrated by immunofluorescence and correlative immunoelectron microscopy (FluoroNanogold).\",\n      \"method\": \"Immunofluorescence, immunoelectron microscopy (FluoroNanogold), confocal microscopy\",\n      \"journal\": \"Journal of molecular and cellular cardiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ultrastructural localization by immunoelectron microscopy, single lab, functional consequences inferred\",\n      \"pmids\": [\"10860776\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Kv4.2 channels undergo both open-state and closed-state inactivation; deletion of the N-terminus (Δ2-40) slows fast and intermediate components of open-state inactivation but does not affect closed-state inactivation or recovery, establishing that N-terminal inactivation is distinct from closed-state inactivation.\",\n      \"method\": \"Site-directed mutagenesis, whole-cell patch clamp in HEK293 cells, kinetic modeling\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis with detailed kinetic analysis and simulation, multiple constructs\",\n      \"pmids\": [\"11507158\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"MiRP1 (KCNE2) associates with Kv4.2 to form a stable complex (co-immunoprecipitation), slows activation and inactivation rates of Kv4.2 and shifts voltage dependence of gating positively, without affecting current amplitude; MiRP1 has no effect on Kv1.4.\",\n      \"method\": \"Xenopus oocyte expression, two-electrode voltage clamp, co-immunoprecipitation\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — co-IP plus detailed biophysical characterization in Xenopus system, single lab\",\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 of Kv4.2 and the PDZ domains of PSD-95; PSD-95 co-expression increases surface expression and clustering of Kv4.2, an effect requiring PSD-95 palmitoylation and the intact VSAL motif.\",\n      \"method\": \"Co-immunoprecipitation, site-directed mutagenesis, biotinylation surface assay, deconvolution microscopy in mammalian cell lines\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — co-IP, mutagenesis, and surface biotinylation with functional consequence, multiple orthogonal methods\",\n      \"pmids\": [\"11923279\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PKA phosphorylation of the Kv4.2 α-subunit is necessary but not sufficient for channel modulation; the ancillary subunit KChIP3 must also be present for PKA to alter channel properties, demonstrating that PKA regulates Kv4.2 as part of a supramolecular complex.\",\n      \"method\": \"Xenopus oocyte expression, two-electrode voltage clamp, co-expression of wild-type and mutant Kv4.2 with/without KChIP3\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — electrophysiological epistasis with defined molecular components, multiple conditions tested\",\n      \"pmids\": [\"12451113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"KChIPs1-3 co-expression with Kv4.2 releases endoplasmic reticulum retention of Kv4.2 and promotes trafficking to the cell surface by masking an N-terminal hydrophobic domain of Kv4.2; KChIP co-expression also increases Kv4.2 steady-state expression, alters phosphorylation, detergent solubility, and stability. KChIP4a does not exert these effects and negatively influences other KChIPs.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence, Western blot, surface biotinylation, subcellular fractionation in heterologous cells and native tissue\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (co-IP, biotinylation, fractionation, microscopy), replicated in native tissue\",\n      \"pmids\": [\"12829703\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Kv4.2 and KChIP2 form octameric complexes with four subunits each, as determined by purification of native Ito channels and direct amino acid analysis of subunit molar ratios.\",\n      \"method\": \"Protein purification, electron microscopy, direct amino acid analysis, biochemical stoichiometry\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — purification and direct amino acid composition analysis establish stoichiometry rigorously\",\n      \"pmids\": [\"14623880\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"PSD-95, when palmitoylated, recruits Kv1.4 but not Kv4.2 into lipid rafts; a portion of Kv4.2 is nonetheless raft-associated in rat brain membranes, and Kv4.2 is found in Thy-1-containing rafts in hippocampal neurons.\",\n      \"method\": \"Lipid raft fractionation, co-immunoprecipitation, immunostaining, raft patching in heterologous cells and rat brain membranes\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple methods in native and heterologous systems, but PSD-95 does not recruit Kv4.2 to rafts (negative result for that specific mechanism)\",\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 gating properties but increases Kv4.2 protein levels and surface expression, thereby increasing peak A-type current amplitude and reducing neuronal excitability.\",\n      \"method\": \"In vitro kinase assay, site-directed mutagenesis, Xenopus oocyte expression, whole-cell patch clamp in hippocampal neurons with constitutively active CaMKII\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro phosphorylation with site identification by mutagenesis, confirmed electrophysiologically in native neurons\",\n      \"pmids\": [\"15071113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"DPP10 co-immunoprecipitates with Kv4.2 from oocytes; DPP10 co-expression increases Kv4.2 surface current ~5-fold, accelerates inactivation and recovery, and shifts voltage dependence of activation (~−19 mV) and inactivation (~−7 mV); the cytoplasmic N-terminal domain of DPP10 determines the acceleration of inactivation.\",\n      \"method\": \"Co-immunoprecipitation, two-electrode voltage clamp in Xenopus oocytes, N-terminal deletion constructs\",\n      \"journal\": \"Biophysical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — co-IP plus detailed biophysical characterization with domain analysis, multiple constructs\",\n      \"pmids\": [\"15454437\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"ERK/MAPK phosphorylation of Kv4.2 at T607 (mimicked by T607D mutation) causes a rightward shift in the activation curve and reduces current amplitude; this effect requires KChIP3 co-expression. The S616D mutation causes an opposite leftward shift in activation voltage.\",\n      \"method\": \"Site-directed mutagenesis (phosphomimetic), Xenopus oocyte expression, two-electrode voltage clamp, co-expression with KChIP3\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — phosphomimetic mutagenesis with electrophysiological readout, dependence on KChIP3 established by epistasis\",\n      \"pmids\": [\"16251476\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Kv4.2 is transported to dendrites by the kinesin Kif17; dominant-negative Kif17 inhibits dendritic localization of both introduced and endogenous Kv4.2 but not other kinesin dominant negatives; Kv4.2 and Kif17 co-immunoprecipitate from brain lysate; the interaction involves the extreme C-terminus of Kv4.2, not the dileucine motif.\",\n      \"method\": \"Dominant-negative kinesin constructs, co-immunoprecipitation from brain and COS cells, confocal imaging in cortical neurons\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP from brain plus loss-of-function imaging with multiple dominant-negative controls\",\n      \"pmids\": [\"16257958\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Kv4.2, KChIP3, and DPP10 form ternary complexes in rat brain and in Xenopus oocytes (co-immunoprecipitation); ternary channel complexes exhibit recovery from inactivation (τrec ~18-26 ms) matching native ISA and significantly faster than binary complexes, reconstituting native neuronal A-type channel properties.\",\n      \"method\": \"Immunoprecipitation from rat brain and Xenopus oocytes, two-electrode voltage clamp in oocytes and CHO cells\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — co-IP from native brain confirmed in heterologous system, biophysical reconstitution matches native current\",\n      \"pmids\": [\"16123112\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Targeted deletion of Kv4.2 in mice eliminates dendritic A-type K+ currents in hippocampal CA1 pyramidal neurons, increases backpropagating action potential amplitude and Ca2+ influx, and lowers the threshold for LTP induction with theta burst pairing, establishing Kv4.2 as the primary determinant of dendritic A-current and a regulator of synaptic plasticity.\",\n      \"method\": \"Kv4.2 knockout mice, whole-cell and dendritic patch clamp, Ca2+ imaging, LTP induction protocols\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout with dendritic electrophysiology and Ca2+ imaging providing direct causal link\",\n      \"pmids\": [\"17122039\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Targeted deletion of Kv4.2 eliminates fast transient outward K+ current (Ito,f) in mouse ventricular myocytes, with compensatory upregulation of slow Ito (Kv1.4-encoded) and dramatic reduction of KChIP2 protein, but no ventricular hypertrophy, demonstrating Kv4.2 is essential for Ito,f and that loss of Ito,f per se is not pathological.\",\n      \"method\": \"Kv4.2 knockout mice, voltage-clamp of ventricular myocytes, Western blot, mRNA analysis\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout with electrophysiology and molecular characterization, multiple assays\",\n      \"pmids\": [\"16293790\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"GRK2 phosphorylates DREAM/KChIP3 at Ser-95; this phosphorylation blocks DREAM-mediated membrane trafficking of Kv4.2 without affecting Kv4.2 tetramerization. Calcineurin de-phosphorylates GRK2-phosphorylated DREAM in vitro, and calcineurin inhibitors also block DREAM-mediated Kv4.2 surface expression.\",\n      \"method\": \"In vitro kinase assay, site-directed mutagenesis (S95D phosphomimetic), surface expression assay, calcineurin in vitro dephosphorylation, pharmacological inhibitors\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro phosphorylation with site identification plus functional consequence on channel trafficking\",\n      \"pmids\": [\"17102134\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"In Kv4.2 knockout mice, KChIP expression is reduced in a region- and cell-specific pattern that precisely follows normal Kv4.2 expression levels, indicating that Kv4.2:KChIP association confers reciprocal stability on KChIP subunits.\",\n      \"method\": \"Immunohistochemistry on Kv4.2−/− mouse brains, region- and cell-specific analysis\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout with systematic IHC analysis across brain regions, single lab\",\n      \"pmids\": [\"17122038\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Kv4.2 undergoes activity-dependent internalization from dendritic spines and dendrites upon glutamate receptor stimulation in hippocampal neurons; internalization is clathrin-mediated and requires NMDA receptor activation and Ca2+ influx. LTP induced by glycine application causes synaptic insertion of GluR1 simultaneously with Kv4.2 internalization.\",\n      \"method\": \"Live imaging of EGFP-Kv4.2, whole-cell patch clamp, pharmacological blockade (clathrin inhibitors, NMDA antagonists, Ca2+ chelation), hippocampal slice cultures\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — live imaging plus electrophysiology plus pharmacological dissection, replicated in slice and dissociated cultures\",\n      \"pmids\": [\"17582333\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"SAP97 interacts with Kv4.2 via the C-terminus of Kv4.2 and the PDZ domains of SAP97; SAP97 directs Kv4.2 to the postsynaptic density and spines; CaMKII-dependent phosphorylation of SAP97 regulates subcellular localization of Kv4.2.\",\n      \"method\": \"Co-immunoprecipitation, PSD fractionation, lentiviral RNAi of SAP97, pharmacological SAP97 translocation assay, immunocytochemistry in hippocampal neurons\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — co-IP, fractionation, RNAi knockdown, pharmacological manipulation, multiple orthogonal methods\",\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 in spinal cord dorsal horn neurons, inhibiting A-type K+ currents and increasing neuronal excitability; Kv4.2 S616A mutant analysis and Kv4.2 knockout mice confirm this specific residue and channel are required for mGlu5-induced nociceptive behavior.\",\n      \"method\": \"Site-directed mutagenesis (S616A), whole-cell patch clamp in dorsal horn neurons, Kv4.2 knockout mice, pharmacological ERK inhibition, behavioral assays\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — mutagenesis identifying specific residue, genetic knockout confirming in vivo relevance, multiple orthogonal methods\",\n      \"pmids\": [\"18045912\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PKA activation induces Kv4.2 internalization from dendritic spines in hippocampal neurons; PKA inhibition prevents AMPA-induced internalization; a point mutation at Kv4.2 S552A (C-terminal PKA site) prevents AMPA-induced internalization, establishing that PKA phosphorylation at S552 is required for activity-dependent Kv4.2 trafficking.\",\n      \"method\": \"Live imaging of EGFP-Kv4.2, pharmacological PKA activation/inhibition (forskolin, 8-Br-cAMP, H89), site-directed mutagenesis (S552A), hippocampal neuron transfection\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — live imaging plus mutagenesis plus pharmacology establishing specific phosphosite requirement\",\n      \"pmids\": [\"18650329\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Gating charge (Q) immobilization in Kv4.2 at hyperpolarized voltages has the same kinetics and voltage dependence as closed-state inactivation, and both are independent of the N-terminal region; a CTX-blocked Kv4.2 channel was used to isolate gating currents, establishing that Q-immobilization and closed-state inactivation are two manifestations of the same voltage sensor desensitization process.\",\n      \"method\": \"Gating current measurements using CTX-blocked engineered Kv4.2 channels, two-electrode voltage clamp, kinetic modeling\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — novel engineered channel approach to isolate gating currents, rigorous kinetic analysis with modeling\",\n      \"pmids\": [\"18299396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"ISA channels are complexes of four Kv4.2 and four DPP6 subunits; stoichiometry established by tandem-subunit constructs enforcing 4:4 and 4:2 assemblies and by direct amino acid analysis of purified complexes.\",\n      \"method\": \"Tandem-subunit constructs, protein purification, direct amino acid analysis, biophysical characterization\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct biochemical (amino acid composition) plus biophysical confirmation of 4:4 stoichiometry\",\n      \"pmids\": [\"18364354\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"DPP6-S co-expression with Kv4.2 increases the unitary conductance of Kv4.2 channels from ~4 pS to ~7.5 pS (matching native CGN channels); CGN Kv4 channels from dpp6 knockout mice have conductance indistinguishable from Kv4.2 alone; charge-neutralization mutations in two N-terminal acidic residues of DPP6-S eliminate this increase, implicating electrostatic interactions.\",\n      \"method\": \"Single-channel recordings in heterologous cells and native CGNs, dpp6 knockout mice, site-directed mutagenesis of DPP6-S\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — single-channel analysis in native and reconstituted systems, genetic knockout, mutagenesis identifying mechanism\",\n      \"pmids\": [\"19279261\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"S4-S5 linker residues (including Glu323) and S6 residue Val404 are critical for Kv4.2 closed-state inactivation; alanine-scanning mutagenesis and double-mutant cycle analysis demonstrate dynamic coupling between voltage sensors and the cytoplasmic gate underlies closed-state inactivation.\",\n      \"method\": \"Alanine-scanning mutagenesis of S4-S5 linker/S5/S6, two-electrode voltage clamp in Xenopus oocytes, double-mutant cycle analysis, selective redox modulation of double-cysteine mutants\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — systematic mutagenesis with double-mutant cycle analysis and cysteine-crosslinking validation\",\n      \"pmids\": [\"19171772\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PKC directly phosphorylates Kv4.2 C-terminus at Ser447 and Ser537 in vitro; phosphorylation at Ser537 is increased in hippocampus upon PKC activation; mutation of both PKC sites to alanine increases surface expression of Kv4.2. Furthermore, prior PKC phosphorylation enhances subsequent ERK phosphorylation of Kv4.2 in vitro, establishing Kv4.2 as a locus for PKC-ERK cross-talk.\",\n      \"method\": \"In vitro PKC kinase assay with GST-fusion proteins, site-directed mutagenesis, surface biotinylation, phospho-selective antibody, in vitro sequential kinase assay\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro phosphorylation with site identification, mutagenesis, surface expression assay, and cross-talk demonstrated in vitro\",\n      \"pmids\": [\"18795890\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"CaV3.1 (T-type Ca2+ channel) associates with the Kv4.2-KChIP3-DPP10c complex and Ca2+ entry through CaV3.1 shifts Kv4.2 inactivation voltage; this regulation is selective to CaV3 isoforms and not observed with CaV1.4, CaV2.1, or CaV2.3.\",\n      \"method\": \"Co-expression in heterologous cells, electrophysiology, calcium channel pharmacology\",\n      \"journal\": \"Channels (Austin, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — functional epistasis in heterologous system, single lab, mechanism partially characterized\",\n      \"pmids\": [\"20458163\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"KChIP4a enhances stabilization and membrane expression of Kv4.2 via a mechanism requiring PKA phosphorylation of Kv4.2 at S552; other KChIP isoforms enhance Kv4.2 surface expression and stability without requiring S552 phosphorylation. A-kinase anchoring proteins (AKAPs) are identified as Kv4.2 binding partners.\",\n      \"method\": \"Co-immunoprecipitation, surface biotinylation, pulse-chase stability assays, site-directed mutagenesis (S552A), co-expression in hippocampal neurons\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, surface biotinylation, mutagenesis, multiple isoform comparisons in single lab\",\n      \"pmids\": [\"20045463\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Glutamate-induced downregulation of Kv4.2 is mediated specifically by NR2B-containing extrasynaptic NMDA receptors (not synaptic NMDA receptors); Ca2+ influx through NR2B-NMDA receptors activates calpain, which degrades Kv4.2 protein, reducing Kv4.2 clusters and causing a hyperpolarizing shift in A-current inactivation.\",\n      \"method\": \"Whole-cell patch clamp, immunocytochemistry, Western blot, pharmacological NR2B antagonists, calpain inhibitors, selective synaptic vs. extrasynaptic NMDA receptor stimulation protocols\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — pharmacological dissection with multiple antagonists, electrophysiology, and protein analysis; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"19857555\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Quantitative immunogold freeze-fracture replica labeling (SDS-FRL) reveals only ~70% increase in Kv4.2 immunogold density along the proximo-distal axis of CA1 apical dendrites (not the 6-fold gradient predicted by electrophysiology), found similarly in main apical dendrites, oblique dendrites, and dendritic spines; no Kv4.2 labeling in presynaptic axons.\",\n      \"method\": \"SDS-digested freeze-fracture replica labeling (SDS-FRL), high-resolution quantitative immunogold EM, confirmed with Kv4.2−/− tissue as negative control\",\n      \"journal\": \"The European journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — quantitative ultrastructural immunogold method validated with knockout negative control\",\n      \"pmids\": [\"22098631\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"DPP6 expression in mouse cortex is unaffected by Kv4.2 and/or Kv4.3 deletion, and DPP6/DPP10 localize to the cell surface independently of Kv4.2; DPP6/DPP10 selectively stabilize cell-surface Kv4.2 protein without affecting total or surface DPP6/DPP10 levels; further addition of KChIP3 in the presence of DPP10 markedly increases both total and surface Kv4.2.\",\n      \"method\": \"Kv4.2/Kv4.3 knockout mice, Western blot, surface biotinylation, heterologous co-expression\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockouts combined with biochemical surface expression assays and heterologous reconstitution\",\n      \"pmids\": [\"22311982\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"A de novo KCND2 missense mutation (p.Val404Met) found in twins with autism and epilepsy causes significantly slowed inactivation of Kv4.2 channels, either alone or co-expressed with wild-type, consistent with dominant gain-of-function; the effect on closed-state inactivation is preserved in the presence of auxiliary subunits.\",\n      \"method\": \"Whole-exome sequencing, heterologous expression in HEK cells, whole-cell patch clamp, wild-type/mutant co-expression\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — direct electrophysiological characterization of mutant channel, dominant effect confirmed by co-expression\",\n      \"pmids\": [\"24501278\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PACAP/PAC1 receptor activation leads to phosphorylation of Kv4.2 and downregulation of surface channel density via convergent PKA and ERK1/2 signaling; PKA-induced effects on Kv4.2 require ERK1/2 phosphorylation of the channel at two specific residues but not direct PKA phosphorylation, establishing a GPCR-channel signaling cascade.\",\n      \"method\": \"Whole-cell patch clamp in hippocampal neurons, surface biotinylation, pharmacological inhibitors of PKA and ERK, identification of phosphorylation sites\",\n      \"journal\": \"Neuropharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — electrophysiology plus surface biotinylation plus pharmacological dissection, single lab\",\n      \"pmids\": [\"26456351\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"H2S inhibits Kv4.2-mediated Ito by targeting a Cys320/Cys529 disulfide motif; mutation of either residue blocks the H2S effect; H2S breaks the disulfide bridge between oxidized cysteine residues but does not modify single cysteines, establishing a specific redox regulatory mechanism.\",\n      \"method\": \"Site-directed mutagenesis (C320A, C529A), whole-cell patch clamp in cardiomyocytes and heterologous cells, pharmacological H2S application\",\n      \"journal\": \"Antioxidants & redox signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis with electrophysiological validation identifying specific cysteine residues, single lab\",\n      \"pmids\": [\"25756524\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"miR-324-5p directly inhibits Kv4.2 protein expression by binding to KCND2 mRNA (recruited to RISC after status epilepticus); antagonizing miR-324-5p is seizure-suppressive and neuroprotective in wild-type but not Kcnd2 knockout mice, placing miR-324-5p-mediated Kv4.2 silencing in the seizure onset pathway.\",\n      \"method\": \"RISC immunoprecipitation, miRNA mimic/antagomir transfection, in vivo kainic acid seizure model, Kcnd2 knockout genetic epistasis, Western blot\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — RISC IP, genetic epistasis with knockout, in vivo and in vitro experiments converging on same mechanism\",\n      \"pmids\": [\"27681419\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The V404M (Val404Met) mutation in Kv4.2 specifically enhances closed-state inactivation (CSI) of channels that have not opened while profoundly impairing inactivation of channels that have opened; the mutation increases stability of the inactivated state and slows closure of open channels (required for CSI); the larger volume of methionine vs valine is a major factor; physical coupling between voltage sensor and pore gate is maintained in the inactivated state.\",\n      \"method\": \"Whole-cell patch clamp in Xenopus oocytes with detailed kinetic analysis, comparison of closed-state vs open-state inactivation, auxiliary subunit co-expression, structural interpretation\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — rigorous biophysical dissection of state-dependent effects with multiple protocols and kinetic modeling\",\n      \"pmids\": [\"29581270\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"A gain-of-function KCND2 mutation p.S447R causes nocturnal paroxysmal atrial fibrillation; the mutation increases the Kv4.2 inactivation time constant and impairs PKC-dependent regulation of Kv4.2 membrane expression (S447 is a PKC phosphorylation site), resulting in augmented channel surface expression and enhanced Ito in both homotetrameric Kv4.2 and heterotetrameric Kv4.2-Kv4.3 channels.\",\n      \"method\": \"Whole-exome sequencing, linkage analysis, Xenopus oocyte electrophysiology, co-expression of mutant and wild-type, hybrid Kv4.2-Kv4.3 chimeric channels\",\n      \"journal\": \"Circulation. Genomic and precision medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — electrophysiological characterization of mutant in multiple channel compositions, mechanistic explanation via PKC site\",\n      \"pmids\": [\"30571183\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Activity-induced phosphorylation of Kv4.2 at pThr607-Pro triggers binding of Pin1 (peptidyl-prolyl cis-trans isomerase), which isomerizes Kv4.2 at this motif, causing dissociation of the Kv4.2-DPP6 complex; mice with Kv4.2 T607A knock-in show altered Kv4.2-DPP6 interaction, increased A-type K+ current, reduced CA1 pyramidal neuron excitability, and improved reversal learning.\",\n      \"method\": \"Pin1 binding assays, Kv4.2 T607A knock-in mice, co-immunoprecipitation, whole-cell patch clamp in CA1 neurons, Morris water maze and lever press behavioral assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — knock-in mouse model with co-IP, electrophysiology, and behavior; multiple orthogonal methods establishing mechanism\",\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; GSK3β-mediated phosphorylation inhibits Kv4.2 channel activity and underlies augmented spike-timing-dependent LTP in chronic mild stress mice; GSK3β knockdown prevents both LTP changes and depressive-like behavior.\",\n      \"method\": \"AAV2-shRNA knockdown of GSK3β, whole-cell patch clamp, immunohistochemistry, pharmacological Kv4.2 inhibition, biochemical phosphorylation analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockdown plus pharmacological and biochemical evidence, multiple orthogonal methods converging on specific residue and behavior\",\n      \"pmids\": [\"32209671\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The N-terminal proximal region (residues 11-23) of Kv4.2 is the major KChIP interaction site; T1 domain residues and C-terminal truncations also affect KChIP2 binding and gating modulation; binding and functional modulation are tightly coupled at the N-terminal site but more loosely coupled at T1 and C-terminal sites.\",\n      \"method\": \"Lysine-scanning and structure-based mutagenesis, co-immunoprecipitation, whole-cell patch clamp in mammalian cells\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — systematic mutagenesis with paired biochemical and electrophysiological readouts, multiple interaction sites characterized\",\n      \"pmids\": [\"16096338\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Mossy fiber synaptic contact and glutamatergic activity (NMDA and/or AMPA receptor activation) are required for targeting Kv4.2 channels from the soma to dendrites and synaptic sites in cerebellar granule cells; glutamate receptor activation in monocultures (without synapse formation) is sufficient to induce dendritic targeting.\",\n      \"method\": \"Co-culture of granule cells with pontine grey nucleus cells, confocal imaging, pharmacological blockade of NMDA/AMPA receptors\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — activity-dependent targeting demonstrated with pharmacological intervention and co-culture system, single lab\",\n      \"pmids\": [\"15140189\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Actin depolymerization by cytochalasin D increases Kv4.2 current density ~7-fold in HEK cells by increasing the number and focal clustering of channels at the cell surface, without changing voltage dependence, single-channel conductance, or open probability.\",\n      \"method\": \"Whole-cell and single-channel patch clamp, cytochalasin D treatment, surface imaging, confocal microscopy in HEK cells\",\n      \"journal\": \"American journal of physiology. Heart and circulatory physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — electrophysiology at macroscopic and single-channel level plus imaging, single lab in heterologous cells\",\n      \"pmids\": [\"14551056\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"DPPX-S co-expression with Kv4.2 causes a −26 mV shift in the gating charge-voltage relationship and accelerates outward gating charge movement; DPPX-S has no effect on Shaker B gating currents, establishing that DPPX-S specifically remodels Kv4.2 voltage-sensor dynamics through destabilization of resting/intermediate states.\",\n      \"method\": \"Gating current measurements (CTX-blocked engineered Kv4.2 channel system), two-electrode voltage clamp in Xenopus oocytes\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct gating current measurement with appropriate controls (Shaker), single lab but rigorous method\",\n      \"pmids\": [\"17130523\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"DPPX-S and KChIP auxiliary subunits, despite distinct structures, exert similar effects on Kv4.2 trafficking (releasing ER retention, promoting plasma membrane expression, altering phosphorylation and stability); KChIP4a inhibits both DPPX-S and other KChIP effects, consistent with ternary complex formation early in biosynthesis; tandem MS reveals co-expression with either DPPX-S or KChIP2 generates similar Kv4.2 phosphorylation patterns matching brain.\",\n      \"method\": \"Heterologous co-expression, Western blot, immunofluorescence, tandem mass spectrometry phosphoproteomics\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — MS phosphoproteomics combined with trafficking assays and multiple subunit comparisons\",\n      \"pmids\": [\"19441798\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Kv4.2 is the principal pore-forming α-subunit of somatodendritic A-type (ISA/IA) and cardiac fast transient outward (Ito,f) K+ channels; it assembles as an octameric 4:4 complex with KChIP auxiliary subunits (with KChIPs releasing ER retention and stabilizing surface expression) and as a 4:4 complex with DPP6/DPP10 transmembrane subunits (which remodel voltage-sensor gating dynamics and increase unitary conductance), forming ternary complexes whose inactivation kinetics match native ISA; channel surface density and gating are bidirectionally regulated by direct phosphorylation at multiple sites by ERK (T602, T607, S616), PKA (T38, S552), CaMKII (S438, S459), and PKC (S447, S537), and by redox modification of Cys320/Cys529; activity-dependent internalization requires NMDA receptor activation, Ca2+ influx, clathrin, and PKA phosphorylation at S552, while dendritic targeting depends on the kinesin Kif17 and on synaptic glutamate receptor activity; Pin1-mediated prolyl isomerization at pThr607 dissociates the Kv4.2-DPP6 complex to regulate neuronal excitability and cognitive flexibility; loss of Kv4.2-encoded dendritic A-current enhances backpropagating action potential amplitude, lowers LTP threshold, and increases seizure susceptibility, while gain-of-function mutations cause epilepsy, autism, and atrial fibrillation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"KCND2 encodes Kv4.2, the principal pore-forming α-subunit of fast-inactivating A-type (ISA) K+ channels in neurons and the fast transient outward current (Ito,f) in cardiac myocytes, where genetic deletion eliminates these currents and establishes Kv4.2 as their primary molecular determinant [#21, #22]. The cloned channel activates rapidly, inactivates with millisecond kinetics, and is 4-AP-sensitive but TEA- and dendrotoxin-insensitive [#0]; it undergoes distinct open-state and closed-state inactivation, the latter reflecting voltage-sensor desensitization (gating-charge immobilization) coupled through the S4-S5 linker and S6 to the cytoplasmic gate [#9, #29, #32]. Native channels are macromolecular assemblies: Kv4.2 forms octameric 4:4 complexes with cytoplasmic KChIP subunits and with transmembrane DPP6/DPP10 subunits [#14, #30]. KChIPs bind the Kv4.2 N-terminus to mask an ER-retention signal and promote surface trafficking and reciprocal subunit stabilization [#13, #24, #47], while DPP6/DPP10 accelerate inactivation, remodel voltage-sensor gating, and increase unitary conductance; ternary Kv4.2-KChIP-DPP complexes reconstitute native ISA kinetics [#17, #20, #31, #50]. Channel surface density and gating are tuned by direct phosphorylation by ERK (T602/T607/S616), PKA (T38/S552), CaMKII (S438/S459), and PKC (S447/S537), with several effects requiring KChIP co-assembly and with cross-talk between kinases [#5, #6, #16, #18, #33]. Trafficking is further controlled by activity-dependent, NMDA-receptor- and Ca2+-driven clathrin-mediated internalization requiring PKA phosphorylation at S552, by Kif17-dependent dendritic transport, by NR2B-NMDAR/calpain-mediated degradation, and by Pin1 prolyl isomerization at pThr607 that dissociates the Kv4.2-DPP6 complex to regulate excitability and learning [#19, #25, #28, #36, #45]. Loss of Kv4.2 A-current enhances backpropagating action potentials and lowers the LTP threshold [#21], and gain-of-function KCND2 mutations cause autism with epilepsy (V404Met, via altered closed-state inactivation) and paroxysmal atrial fibrillation (S447R, via impaired PKC regulation and augmented surface Ito) [#39, #43, #44].\",\n  \"teleology\": [\n    {\n      \"year\": 1991,\n      \"claim\": \"Established that KCND2 encodes a functional voltage-gated A-type K+ channel with a defined kinetic and pharmacological fingerprint, providing the molecular identity for native rapidly inactivating currents.\",\n      \"evidence\": \"Two-electrode voltage-clamp of cloned RK5/Kv4.2 in Xenopus oocytes\",\n      \"pmids\": [\"1722463\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish which native currents Kv4.2 carries in vivo\", \"No auxiliary subunit context\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Defined the intracellular, closed-state mechanism of 4-AP block and its mutual exclusivity with inactivation, linking the drug site to the inactivation machinery.\",\n      \"evidence\": \"State-dependent pharmacological voltage-clamp analysis in oocytes\",\n      \"pmids\": [\"8930194\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Exact molecular residues of the 4-AP site not mapped\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Demonstrated that Kv4 subunits are the predominant carriers of neuronal A-current and cardiac Ito, moving Kv4.2 from a cloned channel to a physiological current determinant.\",\n      \"evidence\": \"Adenoviral dominant-negative Kv4.2 in cerebellar granule cells and ventricular myocytes\",\n      \"pmids\": [\"9395498\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Dominant-negative suppresses all Kv4 members, not Kv4.2-specific\", \"Subunit composition of native channels unresolved at this stage\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Identified the cytoskeletal and trafficking partners and the first kinase inputs to Kv4.2, establishing the channel as a regulated, scaffolded protein rather than a static pore.\",\n      \"evidence\": \"Yeast two-hybrid/co-IP for filamin; in vitro kinase assays with phosphosite mapping for ERK and PKA\",\n      \"pmids\": [\"11102480\", \"11080179\", \"10681507\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of individual phosphosites not yet resolved\", \"In vivo phosphorylation stoichiometry unknown\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Showed that PSD-95 clusters and stabilizes Kv4.2 at the surface and that kinase regulation requires auxiliary subunits, establishing that Kv4.2 is regulated as part of a supramolecular complex.\",\n      \"evidence\": \"Co-IP, VSAL-motif mutagenesis, surface biotinylation, and PKA epistasis with KChIP3 in oocytes\",\n      \"pmids\": [\"11923279\", \"12451113\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of the complex not yet defined\", \"Whether PSD-95 acts in native neurons not directly tested\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Defined KChIP function and established 4:4 channel stoichiometry, explaining how cytoplasmic subunits release ER retention and build the native octameric Ito channel.\",\n      \"evidence\": \"Surface biotinylation/fractionation/co-IP for KChIP trafficking; purification and amino acid analysis for Kv4.2:KChIP2 4:4 stoichiometry\",\n      \"pmids\": [\"12829703\", \"14623880\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address DPP subunit incorporation\", \"KChIP4a inhibitory mechanism not fully resolved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Established CaMKII as a phosphorylation input that increases Kv4.2 protein and surface expression, and identified DPP10 as a transmembrane partner that dramatically increases surface current and accelerates gating.\",\n      \"evidence\": \"In vitro kinase assay with site mutagenesis (CaMKII); co-IP and voltage-clamp with N-terminal deletions (DPP10)\",\n      \"pmids\": [\"15071113\", \"15454437\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Native ternary complex composition not yet shown\", \"CaMKII mechanism of stabilization unknown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Reconstituted native A-type channel kinetics from a defined ternary Kv4.2-KChIP3-DPP10 complex, identified Kif17 as the dendritic transport motor, and mapped KChIP interaction sites and phosphomimetic gating effects.\",\n      \"evidence\": \"Co-IP from brain plus voltage-clamp reconstitution; dominant-negative kinesin with co-IP; lysine-scanning mutagenesis; phosphomimetic mutants with KChIP3 epistasis\",\n      \"pmids\": [\"16123112\", \"16257958\", \"16096338\", \"16251476\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How transport, assembly, and phosphorylation are coordinated in vivo unresolved\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Used genetic knockout to prove Kv4.2 is the primary determinant of dendritic A-current and cardiac Ito,f, linking it causally to synaptic plasticity threshold and reciprocal KChIP stability.\",\n      \"evidence\": \"Kv4.2 knockout mice with dendritic patch clamp, Ca2+ imaging, LTP protocols, myocyte voltage-clamp, and IHC\",\n      \"pmids\": [\"17122039\", \"16293790\", \"17122038\", \"17102134\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Compensatory remodeling complicates interpretation of cardiac phenotype\", \"Whether reduced LTP threshold causes behavioral change not addressed here\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Established activity-dependent trafficking control of Kv4.2 and additional scaffolding/signaling routes coupling synaptic activity to channel surface density and excitability.\",\n      \"evidence\": \"Live imaging plus pharmacology (clathrin/NMDAR/Ca2+) for internalization; SAP97 co-IP/RNAi; mGlu5-ERK-S616 with S616A mutant and knockout behavior\",\n      \"pmids\": [\"17582333\", \"17635915\", \"18045912\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endocytic adaptor proteins linking phosphorylation to clathrin not identified\", \"Coupling between internalization and degradation pathways unclear\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Pinpointed PKA phosphorylation at S552 as the trigger for activity-dependent internalization and clarified that closed-state inactivation is voltage-sensor desensitization independent of the N-terminus.\",\n      \"evidence\": \"Live imaging with S552A mutant and PKA pharmacology; gating-current measurements from CTX-blocked engineered channels\",\n      \"pmids\": [\"18650329\", \"18299396\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream endocytic machinery recognizing pS552 unknown\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Dissected the biophysical basis of DPP-subunit modulation (conductance, voltage-sensor remodeling), the structural determinants of closed-state inactivation, the PKC phosphorylation input with PKC-ERK cross-talk, and CaV3.1 coupling.\",\n      \"evidence\": \"Single-channel recordings with dpp6 knockout; gating currents with DPPX-S; alanine-scanning/double-mutant cycles; in vitro PKC kinase and sequential kinase assays; co-expression electrophysiology with CaV3.1\",\n      \"pmids\": [\"19279261\", \"17130523\", \"19171772\", \"18795890\", \"20458163\", \"19441798\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"CaV3.1 coupling shown only in heterologous cells\", \"Structural mechanism of DPP conductance increase inferred from electrostatics, not structure\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Resolved isoform-specific KChIP trafficking requirements (KChIP4a requires S552 phosphorylation; AKAPs as partners) and identified extrasynaptic NR2B-NMDAR/calpain proteolysis as a degradative downregulation pathway.\",\n      \"evidence\": \"Co-IP, surface biotinylation, pulse-chase with S552A mutant; pharmacological NR2B and calpain dissection with protein analysis\",\n      \"pmids\": [\"20045463\", \"19857555\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Calpain cleavage sites on Kv4.2 not mapped\", \"AKAP identity not specified\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Quantified the actual Kv4.2 dendritic distribution by immunogold EM, revealing a shallower proximo-distal gradient than electrophysiology predicted.\",\n      \"evidence\": \"SDS-FRL quantitative immunogold EM validated with Kv4.2 knockout negative control\",\n      \"pmids\": [\"22098631\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Discrepancy between channel density and functional A-current gradient unexplained\", \"Does not address channel open probability or auxiliary subunit distribution\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Provided the first human disease link, showing a de novo KCND2 gain-of-function mutation causes autism with epilepsy through slowed inactivation.\",\n      \"evidence\": \"Whole-exome sequencing of affected twins plus HEK-cell voltage-clamp of V404M with wild-type co-expression\",\n      \"pmids\": [\"24501278\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo neuronal consequences of V404M not tested\", \"Genotype-phenotype generalizability limited to single family\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined GPCR-to-channel signaling convergence (PACAP/PAC1 via PKA+ERK) and a specific cardiac redox regulatory mechanism through a Cys320/Cys529 disulfide.\",\n      \"evidence\": \"Patch clamp with PKA/ERK inhibitors and biotinylation; C320A/C529A mutagenesis with H2S application in cardiomyocytes\",\n      \"pmids\": [\"26456351\", \"25756524\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"PACAP cascade characterized in single lab\", \"Physiological source of the disulfide oxidation in vivo unclear\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Placed post-transcriptional Kv4.2 silencing by miR-324-5p in the seizure-onset pathway, validated by genetic epistasis.\",\n      \"evidence\": \"RISC IP, antagomir, kainic acid seizure model, and Kcnd2 knockout epistasis\",\n      \"pmids\": [\"27681419\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Other targets of miR-324-5p may contribute to seizure phenotype\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Mechanistically resolved the V404M epilepsy/autism mutation as enhancing closed-state inactivation while impairing open-channel inactivation, and identified an S447R gain-of-function mutation causing atrial fibrillation via disrupted PKC regulation.\",\n      \"evidence\": \"Detailed kinetic voltage-clamp of V404M closed- vs open-state inactivation; WES/linkage plus oocyte electrophysiology of S447R in homo- and heterotetramers\",\n      \"pmids\": [\"29581270\", \"30571183\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No high-resolution structure confirming the proposed steric mechanism\", \"S447R cardiac phenotype not modeled in vivo\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified Pin1 prolyl isomerization at pThr607 as a switch dissociating the Kv4.2-DPP6 complex, and GSK3β phosphorylation at S616 as a stress-related regulator of plasticity and behavior, linking channel regulation to cognition and mood.\",\n      \"evidence\": \"T607A knock-in mice with co-IP, patch clamp, and behavior (Pin1); AAV-shRNA GSK3β knockdown with patch clamp and behavior\",\n      \"pmids\": [\"32218435\", \"32209671\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Pin1 and GSK3β pathways intersect at overlapping C-terminal sites not tested\", \"Therapeutic targeting not explored\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A high-resolution structure of the assembled Kv4.2-KChIP-DPP ternary complex and an integrated model reconciling channel density, phosphorylation state, and the functional A-current gradient remain to be established.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No experimental structure of the native octameric ternary complex in the corpus\", \"Quantitative reconciliation of immunogold density with functional current gradient unresolved\", \"Coordinated logic of multi-kinase phosphorylation in vivo not integrated\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 2, 21, 22]},\n      {\"term_id\": \"GO:0005216\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3, 8, 11, 13, 37]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [13, 51]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [7, 49]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [21, 25, 27, 45]},\n      {\"term_id\": \"R-HSA-397014\", \"supporting_discovery_ids\": [22, 44]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [39, 43, 44, 42]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [13, 19, 25, 28]}\n    ],\n    \"complexes\": [\n      \"Kv4.2-KChIP (4:4 octameric A-type/Ito channel)\",\n      \"Kv4.2-DPP6 (4:4 ISA channel)\",\n      \"Kv4.2-KChIP3-DPP10 ternary channel complex\"\n    ],\n    \"partners\": [\n      \"KCNIP2\",\n      \"KCNIP3\",\n      \"DPP6\",\n      \"DPP10\",\n      \"DLG4\",\n      \"DLG1\",\n      \"KIF17\",\n      \"FLNA\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}