{"gene":"KCNQ2","run_date":"2026-06-10T02:59:49","timeline":{"discoveries":[{"year":2004,"finding":"KCNQ2 channels are functional components of axon initial segments and nodes of Ranvier, colocalizing with ankyrin-G and voltage-dependent Na+ channels throughout the CNS and PNS; ankyrin-G and KCNQ2 can be coimmunoprecipitated from brain. KCNQ channel blockers prolong repolarization of the action potential in neonatal nerves.","method":"Immunohistochemistry, coimmunoprecipitation from brain tissue, pharmacological electrophysiology (retigabine and linopirdine)","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP from brain plus direct localization with functional pharmacological consequence, replicated in multiple CNS/PNS regions","pmids":["14762142"],"is_preprint":false},{"year":2002,"finding":"Calmodulin (CaM) is an auxiliary subunit that binds constitutively to KCNQ2 via two conserved C-terminal motifs (resembling an IQ motif). CaM binding is required for channel function: KCNQ2 mutants deficient in CaM binding fail to generate detectable currents when coexpressed with KCNQ3 even though they reach the membrane and assemble with KCNQ3. CaM coimmunoprecipitates with KCNQ2/3 from mouse brain.","method":"Yeast two-hybrid screen, coimmunoprecipitation from mouse brain, CHO cell electrophysiology, truncation and point mutagenesis of CaM-binding motifs","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (Y2H, co-IP from brain, functional mutagenesis in heterologous cells), single rigorous study","pmids":["12223552"],"is_preprint":false},{"year":2000,"finding":"Co-expression of KCNQ2 and KCNQ3 increases surface expression of both subunits (KCNQ2 ~5-fold, KCNQ3 >10-fold); increased current upon co-expression is primarily due to increased surface expression. A BFNC-associated KCNQ2 truncation mutant lacking the C-terminus fails to reach the surface and fails to stimulate KCNQ3 surface expression. Single-channel conductance for KCNQ2 homomers is ~18 pS.","method":"Noise analysis, single-channel patch recording, surface biotinylation assay in Xenopus oocytes","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — single-channel recordings combined with surface biotinylation and mutagenesis in a single rigorous study","pmids":["10788442"],"is_preprint":false},{"year":2007,"finding":"Calmodulin binding controls KCNQ2 channel trafficking: disruption of CaM binding (including the BFNC mutation R353G) leads to ER retention of KCNQ2, reducing plasma membrane expression. Overexpression of Ca2+-CaM in the R353G mutant partially restores channel distribution; sequestering calmodulin or expressing Ca2+-binding-incompetent CaM retains wild-type channels in the ER.","method":"Live-cell fluorescence imaging, subcellular fractionation, calmodulin overexpression/sequestration in transfected cells","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct live-imaging of ER retention linked to CaM binding, multiple genetic/pharmacological perturbations in single study","pmids":["17993630"],"is_preprint":false},{"year":2004,"finding":"M1 muscarinic receptor-mediated inhibition of KCNQ2/KCNQ3 current proceeds through a Gq-protein cycle: constitutively active Gαq/Gα11 (but not Gα13) causes PIP2 depletion from the plasma membrane and tonic inhibition of KCNQ current; RGS2 blocks PIP2 hydrolysis and current suppression; competitive inhibitors of G-protein nucleotide exchange lengthen and reduce inhibition; the sequence is receptor → Gq activation (Mg2+-dependent) → PLC → PIP2 hydrolysis → channel closure.","method":"Whole-cell patch clamp and confocal microscopy in tsA-201 cells; co-expression of constitutively active and dominant-negative G-protein subunits, RGS2; optical PIP2 probe (GFP-PH domain); kinetic modeling","journal":"The Journal of general physiology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — reconstitution-level mechanistic dissection with multiple genetic manipulations and optical readouts, replicated in subsequent studies","pmids":["15173220"],"is_preprint":false},{"year":2003,"finding":"The C-terminal domain of KCNQ2 and KCNQ3 mediates their heteromeric interaction. Functional interaction requires a conserved ~80 amino acid A-domain plus either the B-domain or the proximal C-terminal region between S6 and the A-domain. There is no functional interaction between KCNQ2/3 and KCNQ1.","method":"Chimeric channel construction, Xenopus oocyte expression, two-microelectrode voltage clamp","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — systematic chimera analysis with electrophysiological readout defining the interaction domain","pmids":["12640002"],"is_preprint":false},{"year":2015,"finding":"Gain-of-function mutations in the voltage-sensing domain of Kv7.2 (R144Q, R201C, R201H) and Kv7.3 (R230C) stabilize the activated state of the channel; the R201 residue forms an intricate network of electrostatic interactions with neighboring negatively charged residues in the resting/intermediate states (confirmed by disulfide trapping). These mutations cause epilepsy through increased M-current activity reducing inhibitory interneuron output rather than intrinsic hyperexcitability.","method":"Electrophysiology in transfected mammalian cells, multistate structural modeling, disulfide trapping experiments, computational hippocampal circuit modeling","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1 / Moderate — electrophysiology combined with structural disulfide-trapping and modeling in one rigorous study","pmids":["25740509"],"is_preprint":false},{"year":2015,"finding":"AnkyrinG (AnkG) anchors KCNQ2 (and KCNQ3) to the axon initial segment and nodes of Ranvier. KCNQ2 and KCNQ3 anchor peptides bind to overlapping but distinct sites near the AnkG N-terminus (ankyrin repeats 1-7). Phosphorylation by protein kinase CK2 augments KCNQ2/3 binding to AnkG. An alternatively spliced AnkG N-terminus selectively gates access to the KCNQ2/3 binding site but not the Nav1.2 binding site, providing a mechanism for the ~40:1 Nav:KCNQ conductance ratio at the distal AIS.","method":"Pulldown assays, co-immunoprecipitation, mutagenesis of AnkG repeat residues, in vitro CK2 phosphorylation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — systematic mutagenesis of binding sites combined with pulldown/co-IP and phosphorylation assays defining distinct binding mechanisms","pmids":["25998125"],"is_preprint":false},{"year":2007,"finding":"Nedd4-2 (but not Nedd4) ubiquitinates KCNQ2/3 channels and reduces K+ current amplitude. The C-terminal region of KCNQ3 is required for Nedd4-2-mediated regulation. Nedd4-2 directly interacts with KCNQ2/3 (demonstrated by GST-fusion pulldown and co-immunoprecipitation) and can ubiquitinate KCNQ2/3 in transfected cells.","method":"Xenopus oocyte expression, electrophysiology, GST-fusion pulldown, co-immunoprecipitation, ubiquitination assay in transfected cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal pulldown and co-IP plus functional ubiquitination assay in single study","pmids":["17322297"],"is_preprint":false},{"year":2014,"finding":"Protein kinase CK2, tethered to KCNQ2 channels, phosphorylates calmodulin, which strengthens calmodulin binding to KCNQ2, confers resistance to PIP2 depletion, and increases KCNQ2 current amplitude. Protein phosphatase 1 (PP1) is also tethered to KCNQ2 via a KVXF motif in the N-terminal tail; mutation of this PP1 binding site augments current density. CK2 inhibition suppresses native M-current in rat sympathetic neurons.","method":"Electrophysiology in HEK cells and rat SCG neurons, co-immunoprecipitation of CK2 and PP1 with KCNQ2, site-directed mutagenesis of PP1 binding motif, CK2 phosphorylation assay on calmodulin","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (co-IP, mutagenesis, in vitro phosphorylation, native neuron recordings) in a single study","pmids":["24627475"],"is_preprint":false},{"year":2006,"finding":"PP2A-Bγ subunit interacts with KCNQ2 (identified by yeast two-hybrid screening of brain cDNA library) and significantly increases KCNQ2 current. GSK3β phosphorylates the KCNQ2 channel, inhibiting it; this phosphorylation is decreased by lithium. Two novel splice variants of KCNQ2 with truncated C-termini are active but exert a dominant-negative effect on wild-type KCNQ2.","method":"Yeast two-hybrid screen, electrophysiology in heterologous cells, GSK3β phosphorylation assay","journal":"The pharmacogenomics journal","confidence":"Medium","confidence_rationale":"Tier 2-3 / Weak — Y2H identification plus functional electrophysiology, single lab, limited biochemical follow-up","pmids":["16733521"],"is_preprint":false},{"year":2000,"finding":"Disruption of the mouse KCNQ2 gene (homozygous knockout) eliminates M-channel function; heterozygous mice have decreased KCNQ2 expression and show hypersensitivity to the convulsant pentylenetetrazole, demonstrating that reduced KCNQ2 expression causes neuronal hyperexcitability.","method":"Gene targeting/knockout in mice, pentylenetetrazole seizure threshold assay, quantitative expression analysis","journal":"Journal of neurochemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean loss-of-function genetic model with defined in vivo phenotypic readout, replicated across multiple lines","pmids":["10854243"],"is_preprint":false},{"year":2008,"finding":"KCNQ2 (with KCNQ3) contributes to the apamin-insensitive medium afterhyperpolarization current (ImAHP) in hippocampal dentate granule cells (~50% reduction in KCNQ2 or KCNQ3 knockout mice); the same KCNQ subunits also contribute to the calcium-activated slow afterhyperpolarization current (IsAHP). Hippocalcin may link calcium signaling to these KCNQ-dependent processes.","method":"Whole-cell patch clamp in hippocampal slices from KCNQ2 and KCNQ3 knockout mice; pharmacological manipulation with KCNQ blockers and openers","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function (knockout) combined with pharmacology and defined electrophysiological phenotype in native neurons","pmids":["19060215"],"is_preprint":false},{"year":2006,"finding":"A naturally occurring Kcnq2 C-terminal deletion mutation (Szt1) in mice reduces M-current amplitude and density in CA1 pyramidal neurons and impairs spike frequency adaptation, demonstrating that KCNQ2 is required for native neuronal M-current and regulation of action potential firing.","method":"Perforated-patch electrophysiology in hippocampal brain slices from Szt1 mutant mice","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Moderate — clean genetic model with direct electrophysiological readout in native neurons","pmids":["16481438"],"is_preprint":false},{"year":2012,"finding":"The Kv7.2/Kv7.3 heterotetramer assembles predominantly as a 2:2 stoichiometry with random (non-fixed) subunit arrangement, as revealed by atomic force microscopy imaging of antibody-decorated isolated channel complexes. Subunit stoichiometry is variable when DNA ratio of the two subunits is varied.","method":"Atomic force microscopy imaging of antibody-decorated isolated channel complexes, co-purification with immunoaffinity beads","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — structural imaging (AFM) with statistical analysis of angle distributions, rigorous in one study","pmids":["22334706"],"is_preprint":false},{"year":2013,"finding":"Calmodulin orchestrates heteromeric assembly of KCNQ2/KCNQ3 and their targeting to the axon initial segment. Abolishing CaM interaction in KCNQ3 (I342A mutation) strongly decreases heteromeric association with KCNQ2 and impairs AIS targeting; exogenous CaM rescues trafficking. Both apoCaM and Ca2+/CaM bind to KCNQ2/3 C-terminal domains and regulate their heteromeric assembly.","method":"Co-immunoprecipitation, immunofluorescence of AIS targeting in neurons, CaM rescue experiments, mutagenesis in KCNQ3 and KCNQ2","journal":"Molecular and cellular neurosciences","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP plus direct AIS localization imaging with genetic and exogenous CaM rescue in neurons","pmids":["24333508"],"is_preprint":false},{"year":2014,"finding":"Dominant-negative KCNQ2 encephalopathy mutations cause loss of function; 3 pore mutations globally reduce current amplitudes and 2 voltage-sensor mutations cause depolarizing shifts of the activation curve at subthreshold potentials, all more severe than typical haploinsufficiency-causing BFNC mutations. Retigabine partially reverses these dominant-negative effects.","method":"Two-microelectrode voltage clamp in Xenopus oocytes, surface biotinylation assay; systematic comparison of 7 encephalopathy mutations","journal":"Annals of neurology","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — systematic electrophysiological analysis with surface expression assay across 7 mutations in a single rigorous study","pmids":["24318194"],"is_preprint":false},{"year":2016,"finding":"The KCNQ2 p.V175L mutation (in the voltage-sensing domain) causes a 25-40 mV hyperpolarizing shift in the conductance-voltage relationship and faster activation kinetics (gain-of-function) without affecting AIS localization, demonstrating that gain-of-function gating changes (not altered localization) can cause early-onset epileptic encephalopathy.","method":"Whole-cell patch clamp in CHO cells, immunofluorescence for AIS localization in neurons, Western blotting","journal":"Epilepsia","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — electrophysiology plus direct localization, single lab, single mutation","pmids":["27030113"],"is_preprint":false},{"year":2015,"finding":"The KCNQ2 p.A294V encephalopathy mutation reduces total KCNQ2 expression to ~20% of WT in CHO cells and produces no measurable current alone; in neurons, it causes mislocalization of heteromeric channels to the somatodendritic compartment rather than AIS. In contrast, the benign p.A294G mutation does not affect AIS targeting, indicating that subcellular mislocalization rather than M-current reduction alone determines disease severity.","method":"Patch clamp in CHO cells, Western blotting, immunofluorescence in neurons comparing AIS vs. somatodendritic distribution","journal":"Neurobiology of disease","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct AIS localization imaging in neurons plus electrophysiology and biochemistry, comparative analysis of two mutations at same residue","pmids":["26007637"],"is_preprint":false},{"year":2016,"finding":"FGF14 positively regulates KCNQ2/3 channels: FGF14 knockdown reduces KCNQ2 at the AIS and reduces whole-cell KCNQ currents. FGF14 interacts with KCNQ2 at a site distinct from the FGF14-Nav channel interaction surface, enabling FGF14 to bridge Nav1.6 and KCNQ2, acting as an organizer of AIS channel localization.","method":"siRNA knockdown, co-immunoprecipitation, immunofluorescence of AIS localization, whole-cell patch clamp","journal":"Proceedings of the National Academy of Sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus knockdown with AIS imaging and electrophysiological readout, single study","pmids":["27994149"],"is_preprint":false},{"year":2016,"finding":"KCNQ2 R198Q is a gain-of-function variant that shifts current activation gating to hyperpolarized potentials; in neurons, Kv7.2 R198Q similarly localizes to the axon initial segment as wild-type, indicating that gating changes rather than altered subcellular distribution are the pathogenic mechanism.","method":"Whole-cell patch clamp in heterologous cells, immunofluorescence of AIS localization in neurons","journal":"Epilepsia","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — electrophysiology plus AIS imaging, single study with four patients, single lab","pmids":["27861786"],"is_preprint":false},{"year":2016,"finding":"Kv7.2/7.3 channels at the AIS exhibit extraordinarily high steady-state stability and very low surface lateral mobility. At high glutamate loads, KCNQ2/3 undergoes rapid irreversible endocytosis requiring activation of NR2B-containing NMDA receptors, Ca2+ influx, and calpain activation (excitotoxic mechanism). This endocytosis is selective for AnkG-bound AIS proteins (Nav1.2 also endocytosed, not AIS GABAA receptors).","method":"Live-cell fluorescence imaging with novel SEP-TAC-Kv7.3 phluorin chimera in dissociated hippocampal neurons; pharmacological dissection of endocytosis mechanism","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct live imaging of channel surface dynamics with mechanistic pharmacological dissection, multiple inhibitors tested","pmids":["26888935"],"is_preprint":false},{"year":2018,"finding":"Epileptic encephalopathy mutations in calmodulin-binding helices A and B of Kv7.2 (R333W, K526N, R532W, M518V) reduce axonal surface expression of heteromeric channels; the M518V mutation additionally reduces CaM binding, induces ubiquitination, and accelerates proteasome-dependent Kv7.2 degradation (rescued by co-expression of Kv7.3). Mutations R333W, K526N, and R532W also alter PIP2 gating modulation revealing novel PIP2 binding residues. M518V expression increases neuronal death.","method":"Surface biotinylation, co-immunoprecipitation of CaM, ubiquitination assay, proteasome inhibitor experiments, whole-cell patch clamp, live-cell imaging in neurons","journal":"Neurobiology of disease","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (surface expression, co-IP, ubiquitination, electrophysiology) in a single study","pmids":["30008368"],"is_preprint":false},{"year":2009,"finding":"The rate-limiting step in M1 muscarinic receptor-mediated suppression of Kv7.2/7.3 M-current is PIP2 hydrolysis (time constant ~6.7 s), not earlier steps (receptor activation <100 ms, M1R/Gβ interaction 200 ms). PLC overexpression accelerates M-current suppression ~3-fold, confirming that PLC availability limits the rate. Channel release of PIP2 and closure are rapid once PLC is active.","method":"Pairwise optical FRET measurements of each signaling step (M1R activation, Gβ interaction, Gαq/Gβ separation, Gαq/PLC interaction, PIP2 hydrolysis) combined with electrophysiology and PLC overexpression","journal":"The Journal of general physiology","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — systematic kinetic dissection using multiple FRET pairs plus electrophysiology in one rigorous study","pmids":["19332618"],"is_preprint":false},{"year":2007,"finding":"In sympathetic neurons, M-current inhibition by bradykinin can use either an IP3/Ca2+-dependent mechanism (product-dependent) or a PIP2 substrate-depletion-dependent mechanism depending on Ca2+ availability and PIP2 synthesis rates, as demonstrated by fluorescent PIP2 sensor (tubby-R332H-cYFP) measurements showing that bradykinin depletes only ~1/3 of the PIP2 depleted by oxotremorine-M under normal conditions, but equally depletes PIP2 when synthesis is blocked by wortmannin.","method":"Live-cell fluorescence imaging with tubby-PIP2 sensor in single sympathetic neurons, pharmacological manipulation (wortmannin, thapsigargin)","journal":"The Journal of physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct PIP2 imaging in native neurons with defined pharmacological perturbations, single lab","pmids":["17395626","17447081"],"is_preprint":false},{"year":2016,"finding":"Phosphorylation of a cluster of five serine residues (S427/S436/S438/S446/S455) within a PIP2-binding domain of Kv7.2 by CDK5, p38 MAPK, CaMKIIα, and PKA is required to maintain the channel's sensitivity to PIP2 depletion. Alanine substitution of all five serines (A5 mutant) reduces sensitivity to PIP2 depletion via Dr-VSP and attenuates M1 muscarinic receptor-mediated channel regulation (but not bradykinin receptor regulation).","method":"LC-MS/MS phosphoproteomics of Kv7.2 immunoprecipitates from rat brain and transfected cells, Dr-VSP PIP2 depletion assay, patch clamp, in vitro kinase assay with purified Kv7.2 C-terminus","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — phosphoproteomics, in vitro kinase assay with purified protein, Dr-VSP functional assay, and mutagenesis combined in one study","pmids":["27621207"],"is_preprint":false},{"year":2018,"finding":"PKC-mediated phosphorylation of Kv7.2 at serine 559 is a key mechanism for neurotransmitter-induced M-current suppression. Kv7.2(S559A) knock-in mice show normal basal M-currents but reduced M-current suppression by muscarinic agonist, resistance to chemoconvulsant seizures, and prevention of status epilepticus-induced neuronal death and epileptogenesis after equivalent SE.","method":"Kv7.2(S559A) knock-in mouse model, primary neuron patch clamp, pilocarpine SE model, histological assessment of neuronal death, long-term EEG recording","journal":"Epilepsia","confidence":"High","confidence_rationale":"Tier 2 / Moderate — clean phospho-site knock-in model with electrophysiology, behavioral seizure assay, and neuropathological readouts","pmids":["30146722"],"is_preprint":false},{"year":2021,"finding":"SUMOylation of Kv7.2 and Kv7.3 inhibits their function: hyper-SUMOylation (in SENP2-deficient mice) reduces binding to PIP2 and reduces CaM1 binding, thereby inhibiting channel assembly and reducing M-currents. SENP2 (a deSUMOylase) is required to maintain normal M-currents; retigabine reduces SUMOylation by decreasing transcription of SUMO-activating enzyme SAE1.","method":"SENP2 knockout mice, co-immunoprecipitation, SUMOylation site mutagenesis, PIP2 binding assays, CaM binding assays, electrophysiology","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic model with biochemical co-IP and mutagenesis, single lab","pmids":["34509475"],"is_preprint":false},{"year":2021,"finding":"Muscarinic M1 receptor activation phosphorylates KCNQ2 at threonine 217 (T217) via PKC in the nucleus accumbens in vivo. PKC directly phosphorylates KCNQ2 at T217 in vitro. Donepezil administration and electric foot shock both induce T217 phosphorylation in the NAc in a PKC/M1R-dependent manner. Conditional deletion of Kcnq2 in the NAc enhances aversive learning.","method":"In vitro kinase assay with purified PKC, phospho-specific antibody detection in brain slices and in vivo, conditional Kcnq2 knockout in NAc, behavioral aversive learning assay","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro kinase assay plus in vivo phosphorylation detection and conditional KO behavioral readout, single lab","pmids":["34878647"],"is_preprint":false},{"year":2022,"finding":"BACE1 recruits KCNQ2/3 channels to lipid-raft membrane microdomains via palmitoylation of BACE1's C-terminal cysteines. BACE1 and KCNQ2/3 form a signaling complex (confirmed by spectral FRET); palmitoylation of BACE1 is required for raft recruitment of KCNQ2/3 but not for the BACE1-KCNQ2/3 complex itself.","method":"Spectral FRET with lipid-raft (L10) and non-raft (S15) membrane probes in HEK cells, BACE1 palmitoylation-deficient (4C/A) mutant, methyl-β-cyclodextrin and anesthetic raft disruption","journal":"The Journal of general physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — FRET-based localization with mutagenesis in heterologous cells, single study, limited biochemical follow-up","pmids":["35201266"],"is_preprint":false},{"year":2022,"finding":"KCNQ2 forms functional heteromeric channels with KCNQ5 independent of KCNQ3, as demonstrated by split-intein-mediated covalent KCNQ2/5 tandem formation and mass spectrometry showing KCNQ2-KCNQ5 association in native brain channels even in the absence of KCNQ3. KCNQ2/3/5 trimers may also form.","method":"Split-intein protein trans-splicing to form KCNQ2/5 tandems, electrophysiology in heterologous cells, mass spectrometry of native brain channels","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — covalent tandem approach plus native brain MS, multiple orthogonal methods in one rigorous study","pmids":["35320039"],"is_preprint":false},{"year":2014,"finding":"Conditional knockout of Kcnq2 in peripheral sensory neurons (Cre-Lox) increases excitability of sensory neurons (increased firing, reduced spike frequency adaptation) and produces thermal hyperalgesia and mechanical allodynia in vivo, without affecting expression of other nodal components including Kv7.3.","method":"Conditional Cre-Lox knockout of Kcnq2 in sensory neurons, whole-cell patch clamp of DRG neurons, behavioral nociception assays (thermal hyperalgesia, mechanical allodynia)","journal":"The Journal of comparative neurology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — cell-type-specific conditional KO with defined electrophysiological and behavioral phenotypes","pmids":["24687876"],"is_preprint":false},{"year":2022,"finding":"Ketamine's sustained antidepressant effects require downregulation of Kcnq2 in glutamatergic neurons of the ventral hippocampus; retigabine (KCNQ activator) augments ketamine's antidepressant-like behavioral effects in mice. These effects are ketamine-specific and do not modulate classical antidepressant (escitalopram) responses.","method":"Transcriptomic analysis of cell-type-specific signatures, electrophysiology, pharmacology (retigabine augmentation), and behavioral antidepressant assays in mice","journal":"Neuron","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple complementary methods (molecular, electrophysiological, pharmacological, behavioral) but mechanism not fully reconstituted","pmids":["35649415"],"is_preprint":false},{"year":2020,"finding":"KCNQ2 loss-of-function encephalopathy mutations in helix B residues K552T and R553L decrease calmodulin binding and axonal enrichment of Kv7.2 channels in hippocampal neurons; mutations L268F (pore), K552T, and R553L all disrupt PIP2-mediated current potentiation, revealing that these residues are critical for PIP2 interaction.","method":"Statistical mutation mapping, structural modeling, whole-cell patch clamp in hippocampal neurons, surface expression (Western blot), internalization assay, molecular dynamics simulation of PIP2 interaction","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — electrophysiology, MD simulation, and neuronal surface expression combined, single lab","pmids":["32179837"],"is_preprint":false},{"year":2023,"finding":"The KCNQ2 R201C gain-of-function variant has opposite effects on excitability in different neuron types: it causes hyperexcitability in cortical layer 2/3 pyramidal neurons but hypoexcitability in CA1 hippocampal pyramidal neurons. The homologous KCNQ3 R231C variant similarly shows cell-type-specific opposite effects.","method":"Transgenic knock-in mice expressing R201C variant, whole-cell patch clamp in acute brain slices from L2/3 and CA1 neurons, comparison with KCNQ3 R231C knock-in","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic knock-in models with direct electrophysiological readout in native neurons across multiple cell types","pmids":["37607817"],"is_preprint":false}],"current_model":"KCNQ2 encodes the Kv7.2 voltage-gated K+ channel subunit that, as a homomeric or KCNQ3/5 heteromeric tetramer anchored to axon initial segments and nodes of Ranvier via AnkG (CK2-phosphorylation-dependent), conducts the low-threshold, slowly activating M-current that controls neuronal excitability; calmodulin binds constitutively to two C-terminal IQ-like motifs and is essential for ER exit, surface trafficking, and channel function; PIP2 is required to keep the channel open and its depletion via Gq/PLC signaling downstream of muscarinic receptors is the primary mechanism of M-current suppression; additional post-translational regulation includes ubiquitination by Nedd4-2 (counteracted by SGK-1), phosphorylation by PKC (at S559, suppressing M-current), CK2 phosphorylation of calmodulin (enhancing channel activity), GSK3β phosphorylation (inhibiting channel), and SUMOylation (impairing PIP2 and CaM binding); loss-of-function mutations cause haploinsufficiency or dominant-negative channel suppression leading to neonatal epilepsy, while gain-of-function voltage-sensor mutations produce cell-type-specific hyper- or hypoexcitability and also cause epilepsy."},"narrative":{"mechanistic_narrative":"KCNQ2 encodes the Kv7.2 voltage-gated K+ channel subunit that, together with KCNQ3 (and KCNQ5), generates the neuronal M-current controlling excitability and action-potential firing; mouse knockout and the Szt1 C-terminal deletion eliminate or reduce M-current, impair spike-frequency adaptation, and produce convulsant hypersensitivity, establishing KCNQ2 as a brake on neuronal excitability [PMID:10854243, PMID:16481438]. Kv7.2 assembles with Kv7.3 through a C-terminal A-domain interaction into a predominantly 2:2 heterotetramer, and co-assembly markedly increases surface expression of both subunits [PMID:10788442, PMID:12640002, PMID:22334706]; KCNQ2 also forms KCNQ3-independent heteromers with KCNQ5 in native brain [PMID:35320039]. The channel is anchored at axon initial segments and nodes of Ranvier alongside Nav channels via ankyrin-G, an interaction augmented by CK2 phosphorylation, with FGF14 acting as an organizer that bridges Nav1.6 and KCNQ2 at the AIS [PMID:14762142, PMID:25998125, PMID:27994149]. Calmodulin binds constitutively to two C-terminal IQ-like motifs and is required for ER exit, heteromeric assembly, AIS targeting, and current generation; loss of CaM binding causes ER retention [PMID:12223552, PMID:17993630, PMID:24333508]. Channel opening requires membrane PIP2, and M-current is suppressed when Gq-coupled muscarinic receptors activate PLC to hydrolyze PIP2, with PIP2 hydrolysis as the rate-limiting step [PMID:15173220, PMID:19332618]. Activity is further tuned by a tethered CK2/PP1 module (CK2 phosphorylates CaM to strengthen binding and PIP2 resistance), PKC phosphorylation at S559 driving neurotransmitter-induced suppression, a serine cluster phosphorylated by CDK5/p38/CaMKII/PKA that sets PIP2 sensitivity, Nedd4-2 ubiquitination, GSK3β phosphorylation, and SUMOylation that impairs PIP2 and CaM binding [PMID:24627475, PMID:27621207, PMID:30146722, PMID:17322297, PMID:16733521, PMID:34509475]. Loss-of-function mutations cause neonatal epilepsy and encephalopathy through haploinsufficiency, dominant-negative current reduction, or mislocalization away from the AIS, while gain-of-function voltage-sensor mutations that stabilize the activated state also cause epilepsy with cell-type-specific effects on excitability [PMID:10854243, PMID:24318194, PMID:26007637, PMID:25740509, PMID:37607817].","teleology":[{"year":2000,"claim":"Established that KCNQ2 is genetically required for the neuronal M-current in vivo and that reduced dosage causes hyperexcitability, defining its physiological role as an excitability brake.","evidence":"Homozygous and heterozygous Kcnq2 knockout mice with pentylenetetrazole seizure-threshold assay","pmids":["10854243"],"confidence":"High","gaps":["Did not resolve subcellular site of M-current control","Homozygous lethality limited adult analysis"]},{"year":2000,"claim":"Showed that KCNQ2/KCNQ3 co-assembly drives the large M-current chiefly by boosting surface expression, explaining why both subunits are needed for robust current.","evidence":"Single-channel recording and surface biotinylation in Xenopus oocytes, with a BFNC C-terminal truncation mutant","pmids":["10788442"],"confidence":"High","gaps":["Trafficking machinery mediating the surface boost unidentified","Did not define assembly stoichiometry"]},{"year":2002,"claim":"Identified calmodulin as a constitutive auxiliary subunit essential for current generation, linking the channel to Ca2+ signaling.","evidence":"Yeast two-hybrid, co-IP from mouse brain, CHO electrophysiology, CaM-motif mutagenesis","pmids":["12223552"],"confidence":"High","gaps":["Mechanism by which CaM enables current not yet resolved (later shown to be trafficking)","Ca2+ vs apoCaM roles unclear at this stage"]},{"year":2003,"claim":"Mapped the C-terminal A-domain as the determinant of KCNQ2/KCNQ3 heteromeric assembly, defining the molecular basis of subunit selectivity.","evidence":"Chimeric channel construction and two-microelectrode voltage clamp in oocytes","pmids":["12640002"],"confidence":"High","gaps":["No structural model of the interface","Stoichiometry not determined"]},{"year":2004,"claim":"Localized KCNQ2 to axon initial segments and nodes of Ranvier in complex with ankyrin-G and Nav channels, placing M-current control at the spike-initiation zone.","evidence":"Immunohistochemistry, co-IP from brain, pharmacological electrophysiology in nerves","pmids":["14762142"],"confidence":"High","gaps":["AnkG binding site and regulation not defined","Did not establish how channel:Nav ratio is set"]},{"year":2004,"claim":"Reconstituted the Gq-PLC-PIP2 cascade for muscarinic M-current suppression, establishing PIP2 depletion as the primary suppression mechanism.","evidence":"Whole-cell patch and GFP-PH PIP2 probe in tsA-201 cells with G-protein and RGS2 manipulations","pmids":["15173220"],"confidence":"High","gaps":["Rate-limiting step not yet pinpointed","PIP2 binding residues on the channel unmapped"]},{"year":2006,"claim":"Demonstrated in native CA1 neurons that KCNQ2 supplies the M-current regulating spike-frequency adaptation, connecting molecular function to firing control.","evidence":"Perforated-patch electrophysiology in Szt1 mutant mouse hippocampal slices","pmids":["16481438"],"confidence":"High","gaps":["Did not address other afterhyperpolarization currents","Behavioral consequences not tested"]},{"year":2006,"claim":"Identified additional regulatory inputs (PP2A-Bgamma enhancement, GSK3beta inhibition) and dominant-negative truncation variants, broadening the post-translational regulatory landscape.","evidence":"Yeast two-hybrid, heterologous electrophysiology, GSK3beta phosphorylation assay","pmids":["16733521"],"confidence":"Medium","gaps":["Single lab with limited biochemical follow-up","GSK3beta phospho-sites not mapped","Physiological relevance untested"]},{"year":2007,"claim":"Showed CaM binding controls ER export, mechanistically explaining the requirement for CaM in current generation and a BFNC mutation's loss of function.","evidence":"Live-cell imaging, subcellular fractionation, CaM overexpression/sequestration in transfected cells","pmids":["17993630"],"confidence":"High","gaps":["Did not address AIS targeting specifically","Quality-control machinery sensing CaM occupancy unknown"]},{"year":2007,"claim":"Established Nedd4-2 as a direct ubiquitin ligase reducing KCNQ2/3 current, adding degradative control over channel abundance.","evidence":"GST pulldown, co-IP, ubiquitination assay and electrophysiology in oocytes","pmids":["17322297"],"confidence":"High","gaps":["In vivo relevance of Nedd4-2 regulation not shown","Ubiquitination sites not mapped"]},{"year":2007,"claim":"Distinguished receptor-specific M-current suppression mechanisms, showing bradykinin uses Ca2+/IP3 or PIP2 depletion depending on PIP2 supply.","evidence":"Tubby-PIP2 sensor imaging in sympathetic neurons with pharmacological perturbation","pmids":["17395626","17447081"],"confidence":"Medium","gaps":["Single lab","Relative contribution in intact circuits unclear"]},{"year":2008,"claim":"Expanded KCNQ2's contribution to the medium and slow afterhyperpolarization currents in hippocampal neurons, linking it to spike-train regulation.","evidence":"Patch clamp in KCNQ2/3 knockout hippocampal slices with KCNQ pharmacology","pmids":["19060215"],"confidence":"High","gaps":["Hippocalcin link not mechanistically resolved","Did not separate KCNQ2 vs KCNQ3 contributions fully"]},{"year":2009,"claim":"Identified PIP2 hydrolysis as the rate-limiting step of muscarinic suppression, refining the kinetic model of M-current control.","evidence":"Pairwise FRET of each signaling step plus electrophysiology and PLC overexpression","pmids":["19332618"],"confidence":"High","gaps":["Channel PIP2 affinity determinants not mapped here","In vivo kinetics not addressed"]},{"year":2012,"claim":"Determined that Kv7.2/7.3 assembles predominantly as a 2:2 tetramer with non-fixed subunit arrangement, defining channel architecture.","evidence":"Atomic force microscopy of antibody-decorated isolated channel complexes","pmids":["22334706"],"confidence":"High","gaps":["Functional consequence of variable arrangement unresolved","No atomic structure"]},{"year":2013,"claim":"Revealed that calmodulin orchestrates heteromeric assembly and AIS targeting, integrating the trafficking and assembly roles of CaM.","evidence":"Co-IP, AIS immunofluorescence in neurons, CaM rescue and mutagenesis","pmids":["24333508"],"confidence":"High","gaps":["How CaM couples to AIS anchoring machinery unclear","Apo- vs Ca2+-CaM roles not fully separated"]},{"year":2014,"claim":"Showed a tethered CK2/PP1 module sets channel activity, with CK2 phosphorylating CaM to strengthen binding and confer PIP2-depletion resistance.","evidence":"Co-IP of CK2/PP1, PP1-motif mutagenesis, CaM phosphorylation assay, electrophysiology in HEK and SCG neurons","pmids":["24627475"],"confidence":"High","gaps":["Stoichiometry of the tethered module not defined","In vivo role of PP1 tethering untested"]},{"year":2014,"claim":"Defined AnkG-mediated anchoring with CK2-augmented binding and a splice-regulated mechanism setting the Nav:KCNQ ratio at the distal AIS.","evidence":"Pulldowns, co-IP, AnkG repeat mutagenesis, in vitro CK2 phosphorylation","pmids":["25998125"],"confidence":"High","gaps":["Structural basis of distinct KCNQ2 vs KCNQ3 anchor sites incomplete","Regulation of splice choice in vivo unknown"]},{"year":2014,"claim":"Demonstrated a peripheral sensory role: conditional Kcnq2 deletion increases sensory neuron excitability and produces hyperalgesia and allodynia.","evidence":"Cre-Lox conditional knockout, DRG patch clamp, nociception behavior","pmids":["24687876"],"confidence":"High","gaps":["Molecular trigger of pain phenotype not dissected","Did not test M-current modulators in vivo"]},{"year":2015,"claim":"Showed gain-of-function voltage-sensor mutations stabilize the activated state and cause epilepsy by reducing interneuron output, complicating the loss-of-function paradigm.","evidence":"Electrophysiology, disulfide trapping, structural and circuit modeling","pmids":["25740509"],"confidence":"High","gaps":["Circuit prediction not validated in native tissue at this stage","No high-resolution structure of the activated state"]},{"year":2014,"claim":"Distinguished dominant-negative encephalopathy mutations from haploinsufficient BFNC mutations and showed retigabine partial rescue, informing genotype-phenotype severity.","evidence":"Two-microelectrode voltage clamp and surface biotinylation across 7 mutations","pmids":["24318194"],"confidence":"High","gaps":["Native neuronal consequences not assessed","Mechanism of dominant-negative suppression not structurally defined"]},{"year":2015,"claim":"Established subcellular mislocalization (somatodendritic vs AIS) as a determinant of disease severity, beyond simple current reduction.","evidence":"Patch clamp, Western blot, AIS immunofluorescence comparing A294V and A294G in neurons","pmids":["26007637"],"confidence":"High","gaps":["Trafficking step disrupted by A294V not identified","Single residue comparison"]},{"year":2016,"claim":"Mapped a serine cluster phosphorylated by CDK5/p38/CaMKII/PKA that tunes channel PIP2 sensitivity and receptor-specific suppression.","evidence":"Phosphoproteomics, in vitro kinase assay with purified C-terminus, Dr-VSP PIP2 assay, mutagenesis","pmids":["27621207"],"confidence":"High","gaps":["Which kinase dominates in vivo unclear","Did not test cluster phospho-state in disease"]},{"year":2016,"claim":"Showed gain-of-function gating mutations (V175L, R198Q) cause encephalopathy without altering AIS localization, establishing gating change as a sufficient pathogenic mechanism.","evidence":"Patch clamp in CHO cells and AIS immunofluorescence in neurons","pmids":["27030113","27861786"],"confidence":"Medium","gaps":["Single mutations per study","Circuit-level excitability not tested"]},{"year":2016,"claim":"Defined channel surface dynamics: AIS Kv7.2/7.3 is highly stable but undergoes calpain-dependent excitotoxic endocytosis under glutamate load, linking M-channels to excitotoxicity.","evidence":"Live imaging with SEP-TAC-Kv7.3 phluorin chimera and pharmacological dissection in hippocampal neurons","pmids":["26888935"],"confidence":"High","gaps":["In vivo relevance to seizure-induced injury not directly shown here","Endocytic adaptor machinery undefined"]},{"year":2016,"claim":"Identified FGF14 as a positive regulator and AIS organizer that bridges Nav1.6 and KCNQ2, coordinating co-localization of the two channel classes.","evidence":"siRNA knockdown, co-IP, AIS immunofluorescence, patch clamp","pmids":["27994149"],"confidence":"Medium","gaps":["Single study","Structural basis of the bridging not resolved"]},{"year":2018,"claim":"Linked CaM-binding-helix encephalopathy mutations to reduced surface expression, with M518V driving CaM loss, ubiquitination, and proteasomal degradation, and exposing novel PIP2 residues.","evidence":"Surface biotinylation, CaM co-IP, ubiquitination/proteasome assays, patch clamp, neuronal imaging","pmids":["30008368"],"confidence":"High","gaps":["Ligase responsible for M518V ubiquitination not identified","Did not test rescue in vivo"]},{"year":2018,"claim":"Established PKC phosphorylation at S559 as a key driver of neurotransmitter-induced M-current suppression with direct seizure and neuroprotection consequences in vivo.","evidence":"Kv7.2(S559A) knock-in mice, patch clamp, pilocarpine SE, histology, EEG","pmids":["30146722"],"confidence":"High","gaps":["Upstream receptor specificity for S559 not fully resolved","Structural impact of phosphorylation unknown"]},{"year":2020,"claim":"Mapped helix B and pore residues (K552T, R553L, L268F) critical for CaM binding, axonal enrichment, and PIP2 potentiation, refining the structural map of regulatory residues.","evidence":"Mutation mapping, structural modeling, MD simulation, patch clamp and surface/internalization assays in neurons","pmids":["32179837"],"confidence":"Medium","gaps":["Single lab","MD-predicted PIP2 contacts not experimentally confirmed structurally"]},{"year":2021,"claim":"Showed SUMOylation negatively regulates the channel by impairing PIP2 and CaM binding and that SENP2 deSUMOylation maintains M-current, adding a SUMO-based regulatory layer.","evidence":"SENP2 knockout mice, co-IP, SUMO-site mutagenesis, binding and electrophysiology assays","pmids":["34509475"],"confidence":"Medium","gaps":["Single lab","SUMO-acceptor sites and physiological triggers incompletely defined"]},{"year":2021,"claim":"Identified M1R/PKC phosphorylation at T217 in nucleus accumbens regulating aversive learning, extending KCNQ2 function to reward-circuit behavior.","evidence":"In vitro PKC kinase assay, phospho-specific detection in vivo, conditional NAc knockout, behavior","pmids":["34878647"],"confidence":"Medium","gaps":["Single lab","How T217 phosphorylation alters channel gating not defined"]},{"year":2022,"claim":"Demonstrated KCNQ2 forms KCNQ3-independent heteromers with KCNQ5 in native brain, expanding the repertoire of M-channel compositions.","evidence":"Split-intein covalent tandems, electrophysiology, native-brain mass spectrometry","pmids":["35320039"],"confidence":"High","gaps":["Functional distinction of KCNQ2/5 vs KCNQ2/3 channels in vivo unclear","Stoichiometry of trimeric assemblies undefined"]},{"year":2022,"claim":"Identified BACE1 as a partner that recruits KCNQ2/3 to lipid rafts via BACE1 palmitoylation, adding membrane-microdomain control of channel localization.","evidence":"Spectral FRET with raft/non-raft probes and palmitoylation-deficient BACE1 in HEK cells","pmids":["35201266"],"confidence":"Medium","gaps":["Heterologous system only","Functional impact on M-current not quantified"]},{"year":2022,"claim":"Linked Kcnq2 downregulation in ventral hippocampal glutamatergic neurons to ketamine's sustained antidepressant action, implicating M-channels in mood regulation.","evidence":"Cell-type transcriptomics, electrophysiology, retigabine augmentation, behavior in mice","pmids":["35649415"],"confidence":"Medium","gaps":["Mechanism connecting ketamine to Kcnq2 downregulation not reconstituted","Causality of downregulation vs marker unclear"]},{"year":2023,"claim":"Showed that a single gain-of-function variant (R201C) produces opposite excitability effects in different neuron types, resolving why GOF mutations cause epilepsy.","evidence":"Transgenic R201C knock-in mice with patch clamp in L2/3 and CA1 neurons, compared to KCNQ3 R231C","pmids":["37607817"],"confidence":"High","gaps":["Circuit-level consequence of opposing cell-type effects not fully resolved","Behavioral phenotype not detailed here"]},{"year":null,"claim":"How the many post-translational modifications, accessory partners, and channel compositions are integrated to set M-current in specific neuron types in vivo remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified in vivo model of combined CaM/PIP2/phospho/SUMO regulation","Functional roles of KCNQ2/5 and trimeric channels in distinct circuits undefined","No high-resolution structure of the human Kv7.2 channel in the corpus"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[2,11,13]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,2,7,21]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,11,13]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[4,23]}],"complexes":["Kv7.2/Kv7.3 heterotetramer","Kv7.2/Kv7.5 heteromeric channel","axon initial segment ankyrin-G complex"],"partners":["KCNQ3","KCNQ5","CALM1","ANK3","NEDD4L","FGF14","BACE1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O43526","full_name":"Potassium voltage-gated channel subfamily KQT member 2","aliases":["KQT-like 2","Neuroblastoma-specific potassium channel subunit alpha KvLQT2","Voltage-gated potassium channel subunit Kv7.2"],"length_aa":872,"mass_kda":95.8,"function":"Pore-forming subunit of the voltage-gated potassium (Kv) M-channel which is responsible for the M-current, a key controller of neuronal excitability (PubMed:24277843, PubMed:28793216, PubMed:9836639). M-channel is composed of pore-forming subunits KCNQ2 and KCNQ3 assembled as heterotetramers (PubMed:10781098, PubMed:14534157, PubMed:32884139, PubMed:37857637, PubMed:9836639). The native M-current has a slowly activating and deactivating potassium conductance which plays a critical role in determining the subthreshold electrical excitability of neurons as well as the responsiveness to synaptic inputs (PubMed:14534157, PubMed:28793216, PubMed:9836639). KCNQ2-KCNQ3 M-channel is selectively permeable in vitro to other cations besides potassium, in decreasing order of affinity K(+) > Rb(+) > Cs(+) > Na(+) (PubMed:28793216). M-channel association with SLC5A3/SMIT1 alters channel ion selectivity, increasing Na(+) and Cs(+) permeation relative to K(+) (PubMed:28793216). Suppressed by activation of the muscarinic acetylcholine receptor CHRM1 (PubMed:10684873, PubMed:10713961)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/O43526/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KCNQ2","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/KCNQ2","total_profiled":1310},"omim":[{"mim_id":"613720","title":"DEVELOPMENTAL AND EPILEPTIC ENCEPHALOPATHY 7; DEE7","url":"https://www.omim.org/entry/613720"},{"mim_id":"607357","title":"POTASSIUM CHANNEL, VOLTAGE-GATED, KQT-LIKE SUBFAMILY, MEMBER 5; KCNQ5","url":"https://www.omim.org/entry/607357"},{"mim_id":"604688","title":"A-KINASE ANCHOR PROTEIN 5; AKAP5","url":"https://www.omim.org/entry/604688"},{"mim_id":"603537","title":"POTASSIUM CHANNEL, VOLTAGE-GATED, KQT-LIKE SUBFAMILY, MEMBER 4; KCNQ4","url":"https://www.omim.org/entry/603537"},{"mim_id":"602235","title":"POTASSIUM CHANNEL, VOLTAGE-GATED, KQT-LIKE SUBFAMILY, MEMBER 2; KCNQ2","url":"https://www.omim.org/entry/602235"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Endoplasmic reticulum","reliability":"Approved"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"brain","ntpm":135.5}],"url":"https://www.proteinatlas.org/search/KCNQ2"},"hgnc":{"alias_symbol":["Kv7.2","ENB1","BFNC","KCNA11","HNSPC"],"prev_symbol":["EBN","EBN1"]},"alphafold":{"accession":"O43526","domains":[{"cath_id":"-","chopping":"70-215","consensus_level":"high","plddt":85.2255,"start":70,"end":215},{"cath_id":"1.10.287.70","chopping":"219-368_531-563","consensus_level":"medium","plddt":88.4401,"start":219,"end":563},{"cath_id":"1.20.5","chopping":"620-649","consensus_level":"medium","plddt":76.6523,"start":620,"end":649}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O43526","model_url":"https://alphafold.ebi.ac.uk/files/AF-O43526-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O43526-F1-predicted_aligned_error_v6.png","plddt_mean":58.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KCNQ2","jax_strain_url":"https://www.jax.org/strain/search?query=KCNQ2"},"sequence":{"accession":"O43526","fasta_url":"https://rest.uniprot.org/uniprotkb/O43526.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O43526/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O43526"}},"corpus_meta":[{"pmid":"22275249","id":"PMC_22275249","title":"KCNQ2 encephalopathy: emerging phenotype of a neonatal epileptic encephalopathy.","date":"2012","source":"Annals of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/22275249","citation_count":406,"is_preprint":false},{"pmid":"14762142","id":"PMC_14762142","title":"KCNQ2 is a nodal K+ channel.","date":"2004","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/14762142","citation_count":354,"is_preprint":false},{"pmid":"14534157","id":"PMC_14534157","title":"KCNQ2 and KCNQ3 potassium channel genes in benign familial neonatal convulsions: expansion of the functional and mutation spectrum.","date":"2003","source":"Brain : a journal of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/14534157","citation_count":230,"is_preprint":false},{"pmid":"25880994","id":"PMC_25880994","title":"Early and effective treatment of KCNQ2 encephalopathy.","date":"2015","source":"Epilepsia","url":"https://pubmed.ncbi.nlm.nih.gov/25880994","citation_count":204,"is_preprint":false},{"pmid":"24318194","id":"PMC_24318194","title":"Dominant-negative effects of KCNQ2 mutations are associated with epileptic encephalopathy.","date":"2014","source":"Annals of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/24318194","citation_count":188,"is_preprint":false},{"pmid":"24107868","id":"PMC_24107868","title":"Extending the KCNQ2 encephalopathy spectrum: clinical and neuroimaging findings in 17 patients.","date":"2013","source":"Neurology","url":"https://pubmed.ncbi.nlm.nih.gov/24107868","citation_count":187,"is_preprint":false},{"pmid":"27602407","id":"PMC_27602407","title":"KCNQ2 encephalopathy: Features, mutational hot spots, and ezogabine treatment of 11 patients.","date":"2016","source":"Neurology. 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channels are functional components of axon initial segments and nodes of Ranvier, colocalizing with ankyrin-G and voltage-dependent Na+ channels throughout the CNS and PNS; ankyrin-G and KCNQ2 can be coimmunoprecipitated from brain. KCNQ channel blockers prolong repolarization of the action potential in neonatal nerves.\",\n      \"method\": \"Immunohistochemistry, coimmunoprecipitation from brain tissue, pharmacological electrophysiology (retigabine and linopirdine)\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP from brain plus direct localization with functional pharmacological consequence, replicated in multiple CNS/PNS regions\",\n      \"pmids\": [\"14762142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Calmodulin (CaM) is an auxiliary subunit that binds constitutively to KCNQ2 via two conserved C-terminal motifs (resembling an IQ motif). CaM binding is required for channel function: KCNQ2 mutants deficient in CaM binding fail to generate detectable currents when coexpressed with KCNQ3 even though they reach the membrane and assemble with KCNQ3. CaM coimmunoprecipitates with KCNQ2/3 from mouse brain.\",\n      \"method\": \"Yeast two-hybrid screen, coimmunoprecipitation from mouse brain, CHO cell electrophysiology, truncation and point mutagenesis of CaM-binding motifs\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (Y2H, co-IP from brain, functional mutagenesis in heterologous cells), single rigorous study\",\n      \"pmids\": [\"12223552\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Co-expression of KCNQ2 and KCNQ3 increases surface expression of both subunits (KCNQ2 ~5-fold, KCNQ3 >10-fold); increased current upon co-expression is primarily due to increased surface expression. A BFNC-associated KCNQ2 truncation mutant lacking the C-terminus fails to reach the surface and fails to stimulate KCNQ3 surface expression. Single-channel conductance for KCNQ2 homomers is ~18 pS.\",\n      \"method\": \"Noise analysis, single-channel patch recording, surface biotinylation assay in Xenopus oocytes\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — single-channel recordings combined with surface biotinylation and mutagenesis in a single rigorous study\",\n      \"pmids\": [\"10788442\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Calmodulin binding controls KCNQ2 channel trafficking: disruption of CaM binding (including the BFNC mutation R353G) leads to ER retention of KCNQ2, reducing plasma membrane expression. Overexpression of Ca2+-CaM in the R353G mutant partially restores channel distribution; sequestering calmodulin or expressing Ca2+-binding-incompetent CaM retains wild-type channels in the ER.\",\n      \"method\": \"Live-cell fluorescence imaging, subcellular fractionation, calmodulin overexpression/sequestration in transfected cells\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct live-imaging of ER retention linked to CaM binding, multiple genetic/pharmacological perturbations in single study\",\n      \"pmids\": [\"17993630\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"M1 muscarinic receptor-mediated inhibition of KCNQ2/KCNQ3 current proceeds through a Gq-protein cycle: constitutively active Gαq/Gα11 (but not Gα13) causes PIP2 depletion from the plasma membrane and tonic inhibition of KCNQ current; RGS2 blocks PIP2 hydrolysis and current suppression; competitive inhibitors of G-protein nucleotide exchange lengthen and reduce inhibition; the sequence is receptor → Gq activation (Mg2+-dependent) → PLC → PIP2 hydrolysis → channel closure.\",\n      \"method\": \"Whole-cell patch clamp and confocal microscopy in tsA-201 cells; co-expression of constitutively active and dominant-negative G-protein subunits, RGS2; optical PIP2 probe (GFP-PH domain); kinetic modeling\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — reconstitution-level mechanistic dissection with multiple genetic manipulations and optical readouts, replicated in subsequent studies\",\n      \"pmids\": [\"15173220\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The C-terminal domain of KCNQ2 and KCNQ3 mediates their heteromeric interaction. Functional interaction requires a conserved ~80 amino acid A-domain plus either the B-domain or the proximal C-terminal region between S6 and the A-domain. There is no functional interaction between KCNQ2/3 and KCNQ1.\",\n      \"method\": \"Chimeric channel construction, Xenopus oocyte expression, two-microelectrode voltage clamp\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — systematic chimera analysis with electrophysiological readout defining the interaction domain\",\n      \"pmids\": [\"12640002\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Gain-of-function mutations in the voltage-sensing domain of Kv7.2 (R144Q, R201C, R201H) and Kv7.3 (R230C) stabilize the activated state of the channel; the R201 residue forms an intricate network of electrostatic interactions with neighboring negatively charged residues in the resting/intermediate states (confirmed by disulfide trapping). These mutations cause epilepsy through increased M-current activity reducing inhibitory interneuron output rather than intrinsic hyperexcitability.\",\n      \"method\": \"Electrophysiology in transfected mammalian cells, multistate structural modeling, disulfide trapping experiments, computational hippocampal circuit modeling\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — electrophysiology combined with structural disulfide-trapping and modeling in one rigorous study\",\n      \"pmids\": [\"25740509\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"AnkyrinG (AnkG) anchors KCNQ2 (and KCNQ3) to the axon initial segment and nodes of Ranvier. KCNQ2 and KCNQ3 anchor peptides bind to overlapping but distinct sites near the AnkG N-terminus (ankyrin repeats 1-7). Phosphorylation by protein kinase CK2 augments KCNQ2/3 binding to AnkG. An alternatively spliced AnkG N-terminus selectively gates access to the KCNQ2/3 binding site but not the Nav1.2 binding site, providing a mechanism for the ~40:1 Nav:KCNQ conductance ratio at the distal AIS.\",\n      \"method\": \"Pulldown assays, co-immunoprecipitation, mutagenesis of AnkG repeat residues, in vitro CK2 phosphorylation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — systematic mutagenesis of binding sites combined with pulldown/co-IP and phosphorylation assays defining distinct binding mechanisms\",\n      \"pmids\": [\"25998125\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Nedd4-2 (but not Nedd4) ubiquitinates KCNQ2/3 channels and reduces K+ current amplitude. The C-terminal region of KCNQ3 is required for Nedd4-2-mediated regulation. Nedd4-2 directly interacts with KCNQ2/3 (demonstrated by GST-fusion pulldown and co-immunoprecipitation) and can ubiquitinate KCNQ2/3 in transfected cells.\",\n      \"method\": \"Xenopus oocyte expression, electrophysiology, GST-fusion pulldown, co-immunoprecipitation, ubiquitination assay in transfected cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal pulldown and co-IP plus functional ubiquitination assay in single study\",\n      \"pmids\": [\"17322297\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Protein kinase CK2, tethered to KCNQ2 channels, phosphorylates calmodulin, which strengthens calmodulin binding to KCNQ2, confers resistance to PIP2 depletion, and increases KCNQ2 current amplitude. Protein phosphatase 1 (PP1) is also tethered to KCNQ2 via a KVXF motif in the N-terminal tail; mutation of this PP1 binding site augments current density. CK2 inhibition suppresses native M-current in rat sympathetic neurons.\",\n      \"method\": \"Electrophysiology in HEK cells and rat SCG neurons, co-immunoprecipitation of CK2 and PP1 with KCNQ2, site-directed mutagenesis of PP1 binding motif, CK2 phosphorylation assay on calmodulin\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (co-IP, mutagenesis, in vitro phosphorylation, native neuron recordings) in a single study\",\n      \"pmids\": [\"24627475\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"PP2A-Bγ subunit interacts with KCNQ2 (identified by yeast two-hybrid screening of brain cDNA library) and significantly increases KCNQ2 current. GSK3β phosphorylates the KCNQ2 channel, inhibiting it; this phosphorylation is decreased by lithium. Two novel splice variants of KCNQ2 with truncated C-termini are active but exert a dominant-negative effect on wild-type KCNQ2.\",\n      \"method\": \"Yeast two-hybrid screen, electrophysiology in heterologous cells, GSK3β phosphorylation assay\",\n      \"journal\": \"The pharmacogenomics journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Weak — Y2H identification plus functional electrophysiology, single lab, limited biochemical follow-up\",\n      \"pmids\": [\"16733521\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Disruption of the mouse KCNQ2 gene (homozygous knockout) eliminates M-channel function; heterozygous mice have decreased KCNQ2 expression and show hypersensitivity to the convulsant pentylenetetrazole, demonstrating that reduced KCNQ2 expression causes neuronal hyperexcitability.\",\n      \"method\": \"Gene targeting/knockout in mice, pentylenetetrazole seizure threshold assay, quantitative expression analysis\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean loss-of-function genetic model with defined in vivo phenotypic readout, replicated across multiple lines\",\n      \"pmids\": [\"10854243\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"KCNQ2 (with KCNQ3) contributes to the apamin-insensitive medium afterhyperpolarization current (ImAHP) in hippocampal dentate granule cells (~50% reduction in KCNQ2 or KCNQ3 knockout mice); the same KCNQ subunits also contribute to the calcium-activated slow afterhyperpolarization current (IsAHP). Hippocalcin may link calcium signaling to these KCNQ-dependent processes.\",\n      \"method\": \"Whole-cell patch clamp in hippocampal slices from KCNQ2 and KCNQ3 knockout mice; pharmacological manipulation with KCNQ blockers and openers\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function (knockout) combined with pharmacology and defined electrophysiological phenotype in native neurons\",\n      \"pmids\": [\"19060215\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"A naturally occurring Kcnq2 C-terminal deletion mutation (Szt1) in mice reduces M-current amplitude and density in CA1 pyramidal neurons and impairs spike frequency adaptation, demonstrating that KCNQ2 is required for native neuronal M-current and regulation of action potential firing.\",\n      \"method\": \"Perforated-patch electrophysiology in hippocampal brain slices from Szt1 mutant mice\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean genetic model with direct electrophysiological readout in native neurons\",\n      \"pmids\": [\"16481438\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The Kv7.2/Kv7.3 heterotetramer assembles predominantly as a 2:2 stoichiometry with random (non-fixed) subunit arrangement, as revealed by atomic force microscopy imaging of antibody-decorated isolated channel complexes. Subunit stoichiometry is variable when DNA ratio of the two subunits is varied.\",\n      \"method\": \"Atomic force microscopy imaging of antibody-decorated isolated channel complexes, co-purification with immunoaffinity beads\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — structural imaging (AFM) with statistical analysis of angle distributions, rigorous in one study\",\n      \"pmids\": [\"22334706\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Calmodulin orchestrates heteromeric assembly of KCNQ2/KCNQ3 and their targeting to the axon initial segment. Abolishing CaM interaction in KCNQ3 (I342A mutation) strongly decreases heteromeric association with KCNQ2 and impairs AIS targeting; exogenous CaM rescues trafficking. Both apoCaM and Ca2+/CaM bind to KCNQ2/3 C-terminal domains and regulate their heteromeric assembly.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence of AIS targeting in neurons, CaM rescue experiments, mutagenesis in KCNQ3 and KCNQ2\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP plus direct AIS localization imaging with genetic and exogenous CaM rescue in neurons\",\n      \"pmids\": [\"24333508\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Dominant-negative KCNQ2 encephalopathy mutations cause loss of function; 3 pore mutations globally reduce current amplitudes and 2 voltage-sensor mutations cause depolarizing shifts of the activation curve at subthreshold potentials, all more severe than typical haploinsufficiency-causing BFNC mutations. Retigabine partially reverses these dominant-negative effects.\",\n      \"method\": \"Two-microelectrode voltage clamp in Xenopus oocytes, surface biotinylation assay; systematic comparison of 7 encephalopathy mutations\",\n      \"journal\": \"Annals of neurology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — systematic electrophysiological analysis with surface expression assay across 7 mutations in a single rigorous study\",\n      \"pmids\": [\"24318194\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The KCNQ2 p.V175L mutation (in the voltage-sensing domain) causes a 25-40 mV hyperpolarizing shift in the conductance-voltage relationship and faster activation kinetics (gain-of-function) without affecting AIS localization, demonstrating that gain-of-function gating changes (not altered localization) can cause early-onset epileptic encephalopathy.\",\n      \"method\": \"Whole-cell patch clamp in CHO cells, immunofluorescence for AIS localization in neurons, Western blotting\",\n      \"journal\": \"Epilepsia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — electrophysiology plus direct localization, single lab, single mutation\",\n      \"pmids\": [\"27030113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The KCNQ2 p.A294V encephalopathy mutation reduces total KCNQ2 expression to ~20% of WT in CHO cells and produces no measurable current alone; in neurons, it causes mislocalization of heteromeric channels to the somatodendritic compartment rather than AIS. In contrast, the benign p.A294G mutation does not affect AIS targeting, indicating that subcellular mislocalization rather than M-current reduction alone determines disease severity.\",\n      \"method\": \"Patch clamp in CHO cells, Western blotting, immunofluorescence in neurons comparing AIS vs. somatodendritic distribution\",\n      \"journal\": \"Neurobiology of disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct AIS localization imaging in neurons plus electrophysiology and biochemistry, comparative analysis of two mutations at same residue\",\n      \"pmids\": [\"26007637\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"FGF14 positively regulates KCNQ2/3 channels: FGF14 knockdown reduces KCNQ2 at the AIS and reduces whole-cell KCNQ currents. FGF14 interacts with KCNQ2 at a site distinct from the FGF14-Nav channel interaction surface, enabling FGF14 to bridge Nav1.6 and KCNQ2, acting as an organizer of AIS channel localization.\",\n      \"method\": \"siRNA knockdown, co-immunoprecipitation, immunofluorescence of AIS localization, whole-cell patch clamp\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus knockdown with AIS imaging and electrophysiological readout, single study\",\n      \"pmids\": [\"27994149\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"KCNQ2 R198Q is a gain-of-function variant that shifts current activation gating to hyperpolarized potentials; in neurons, Kv7.2 R198Q similarly localizes to the axon initial segment as wild-type, indicating that gating changes rather than altered subcellular distribution are the pathogenic mechanism.\",\n      \"method\": \"Whole-cell patch clamp in heterologous cells, immunofluorescence of AIS localization in neurons\",\n      \"journal\": \"Epilepsia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — electrophysiology plus AIS imaging, single study with four patients, single lab\",\n      \"pmids\": [\"27861786\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Kv7.2/7.3 channels at the AIS exhibit extraordinarily high steady-state stability and very low surface lateral mobility. At high glutamate loads, KCNQ2/3 undergoes rapid irreversible endocytosis requiring activation of NR2B-containing NMDA receptors, Ca2+ influx, and calpain activation (excitotoxic mechanism). This endocytosis is selective for AnkG-bound AIS proteins (Nav1.2 also endocytosed, not AIS GABAA receptors).\",\n      \"method\": \"Live-cell fluorescence imaging with novel SEP-TAC-Kv7.3 phluorin chimera in dissociated hippocampal neurons; pharmacological dissection of endocytosis mechanism\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct live imaging of channel surface dynamics with mechanistic pharmacological dissection, multiple inhibitors tested\",\n      \"pmids\": [\"26888935\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Epileptic encephalopathy mutations in calmodulin-binding helices A and B of Kv7.2 (R333W, K526N, R532W, M518V) reduce axonal surface expression of heteromeric channels; the M518V mutation additionally reduces CaM binding, induces ubiquitination, and accelerates proteasome-dependent Kv7.2 degradation (rescued by co-expression of Kv7.3). Mutations R333W, K526N, and R532W also alter PIP2 gating modulation revealing novel PIP2 binding residues. M518V expression increases neuronal death.\",\n      \"method\": \"Surface biotinylation, co-immunoprecipitation of CaM, ubiquitination assay, proteasome inhibitor experiments, whole-cell patch clamp, live-cell imaging in neurons\",\n      \"journal\": \"Neurobiology of disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (surface expression, co-IP, ubiquitination, electrophysiology) in a single study\",\n      \"pmids\": [\"30008368\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"The rate-limiting step in M1 muscarinic receptor-mediated suppression of Kv7.2/7.3 M-current is PIP2 hydrolysis (time constant ~6.7 s), not earlier steps (receptor activation <100 ms, M1R/Gβ interaction 200 ms). PLC overexpression accelerates M-current suppression ~3-fold, confirming that PLC availability limits the rate. Channel release of PIP2 and closure are rapid once PLC is active.\",\n      \"method\": \"Pairwise optical FRET measurements of each signaling step (M1R activation, Gβ interaction, Gαq/Gβ separation, Gαq/PLC interaction, PIP2 hydrolysis) combined with electrophysiology and PLC overexpression\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — systematic kinetic dissection using multiple FRET pairs plus electrophysiology in one rigorous study\",\n      \"pmids\": [\"19332618\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"In sympathetic neurons, M-current inhibition by bradykinin can use either an IP3/Ca2+-dependent mechanism (product-dependent) or a PIP2 substrate-depletion-dependent mechanism depending on Ca2+ availability and PIP2 synthesis rates, as demonstrated by fluorescent PIP2 sensor (tubby-R332H-cYFP) measurements showing that bradykinin depletes only ~1/3 of the PIP2 depleted by oxotremorine-M under normal conditions, but equally depletes PIP2 when synthesis is blocked by wortmannin.\",\n      \"method\": \"Live-cell fluorescence imaging with tubby-PIP2 sensor in single sympathetic neurons, pharmacological manipulation (wortmannin, thapsigargin)\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct PIP2 imaging in native neurons with defined pharmacological perturbations, single lab\",\n      \"pmids\": [\"17395626\", \"17447081\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Phosphorylation of a cluster of five serine residues (S427/S436/S438/S446/S455) within a PIP2-binding domain of Kv7.2 by CDK5, p38 MAPK, CaMKIIα, and PKA is required to maintain the channel's sensitivity to PIP2 depletion. Alanine substitution of all five serines (A5 mutant) reduces sensitivity to PIP2 depletion via Dr-VSP and attenuates M1 muscarinic receptor-mediated channel regulation (but not bradykinin receptor regulation).\",\n      \"method\": \"LC-MS/MS phosphoproteomics of Kv7.2 immunoprecipitates from rat brain and transfected cells, Dr-VSP PIP2 depletion assay, patch clamp, in vitro kinase assay with purified Kv7.2 C-terminus\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — phosphoproteomics, in vitro kinase assay with purified protein, Dr-VSP functional assay, and mutagenesis combined in one study\",\n      \"pmids\": [\"27621207\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PKC-mediated phosphorylation of Kv7.2 at serine 559 is a key mechanism for neurotransmitter-induced M-current suppression. Kv7.2(S559A) knock-in mice show normal basal M-currents but reduced M-current suppression by muscarinic agonist, resistance to chemoconvulsant seizures, and prevention of status epilepticus-induced neuronal death and epileptogenesis after equivalent SE.\",\n      \"method\": \"Kv7.2(S559A) knock-in mouse model, primary neuron patch clamp, pilocarpine SE model, histological assessment of neuronal death, long-term EEG recording\",\n      \"journal\": \"Epilepsia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean phospho-site knock-in model with electrophysiology, behavioral seizure assay, and neuropathological readouts\",\n      \"pmids\": [\"30146722\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SUMOylation of Kv7.2 and Kv7.3 inhibits their function: hyper-SUMOylation (in SENP2-deficient mice) reduces binding to PIP2 and reduces CaM1 binding, thereby inhibiting channel assembly and reducing M-currents. SENP2 (a deSUMOylase) is required to maintain normal M-currents; retigabine reduces SUMOylation by decreasing transcription of SUMO-activating enzyme SAE1.\",\n      \"method\": \"SENP2 knockout mice, co-immunoprecipitation, SUMOylation site mutagenesis, PIP2 binding assays, CaM binding assays, electrophysiology\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic model with biochemical co-IP and mutagenesis, single lab\",\n      \"pmids\": [\"34509475\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Muscarinic M1 receptor activation phosphorylates KCNQ2 at threonine 217 (T217) via PKC in the nucleus accumbens in vivo. PKC directly phosphorylates KCNQ2 at T217 in vitro. Donepezil administration and electric foot shock both induce T217 phosphorylation in the NAc in a PKC/M1R-dependent manner. Conditional deletion of Kcnq2 in the NAc enhances aversive learning.\",\n      \"method\": \"In vitro kinase assay with purified PKC, phospho-specific antibody detection in brain slices and in vivo, conditional Kcnq2 knockout in NAc, behavioral aversive learning assay\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro kinase assay plus in vivo phosphorylation detection and conditional KO behavioral readout, single lab\",\n      \"pmids\": [\"34878647\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"BACE1 recruits KCNQ2/3 channels to lipid-raft membrane microdomains via palmitoylation of BACE1's C-terminal cysteines. BACE1 and KCNQ2/3 form a signaling complex (confirmed by spectral FRET); palmitoylation of BACE1 is required for raft recruitment of KCNQ2/3 but not for the BACE1-KCNQ2/3 complex itself.\",\n      \"method\": \"Spectral FRET with lipid-raft (L10) and non-raft (S15) membrane probes in HEK cells, BACE1 palmitoylation-deficient (4C/A) mutant, methyl-β-cyclodextrin and anesthetic raft disruption\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — FRET-based localization with mutagenesis in heterologous cells, single study, limited biochemical follow-up\",\n      \"pmids\": [\"35201266\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"KCNQ2 forms functional heteromeric channels with KCNQ5 independent of KCNQ3, as demonstrated by split-intein-mediated covalent KCNQ2/5 tandem formation and mass spectrometry showing KCNQ2-KCNQ5 association in native brain channels even in the absence of KCNQ3. KCNQ2/3/5 trimers may also form.\",\n      \"method\": \"Split-intein protein trans-splicing to form KCNQ2/5 tandems, electrophysiology in heterologous cells, mass spectrometry of native brain channels\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — covalent tandem approach plus native brain MS, multiple orthogonal methods in one rigorous study\",\n      \"pmids\": [\"35320039\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Conditional knockout of Kcnq2 in peripheral sensory neurons (Cre-Lox) increases excitability of sensory neurons (increased firing, reduced spike frequency adaptation) and produces thermal hyperalgesia and mechanical allodynia in vivo, without affecting expression of other nodal components including Kv7.3.\",\n      \"method\": \"Conditional Cre-Lox knockout of Kcnq2 in sensory neurons, whole-cell patch clamp of DRG neurons, behavioral nociception assays (thermal hyperalgesia, mechanical allodynia)\",\n      \"journal\": \"The Journal of comparative neurology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-type-specific conditional KO with defined electrophysiological and behavioral phenotypes\",\n      \"pmids\": [\"24687876\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Ketamine's sustained antidepressant effects require downregulation of Kcnq2 in glutamatergic neurons of the ventral hippocampus; retigabine (KCNQ activator) augments ketamine's antidepressant-like behavioral effects in mice. These effects are ketamine-specific and do not modulate classical antidepressant (escitalopram) responses.\",\n      \"method\": \"Transcriptomic analysis of cell-type-specific signatures, electrophysiology, pharmacology (retigabine augmentation), and behavioral antidepressant assays in mice\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple complementary methods (molecular, electrophysiological, pharmacological, behavioral) but mechanism not fully reconstituted\",\n      \"pmids\": [\"35649415\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"KCNQ2 loss-of-function encephalopathy mutations in helix B residues K552T and R553L decrease calmodulin binding and axonal enrichment of Kv7.2 channels in hippocampal neurons; mutations L268F (pore), K552T, and R553L all disrupt PIP2-mediated current potentiation, revealing that these residues are critical for PIP2 interaction.\",\n      \"method\": \"Statistical mutation mapping, structural modeling, whole-cell patch clamp in hippocampal neurons, surface expression (Western blot), internalization assay, molecular dynamics simulation of PIP2 interaction\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — electrophysiology, MD simulation, and neuronal surface expression combined, single lab\",\n      \"pmids\": [\"32179837\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The KCNQ2 R201C gain-of-function variant has opposite effects on excitability in different neuron types: it causes hyperexcitability in cortical layer 2/3 pyramidal neurons but hypoexcitability in CA1 hippocampal pyramidal neurons. The homologous KCNQ3 R231C variant similarly shows cell-type-specific opposite effects.\",\n      \"method\": \"Transgenic knock-in mice expressing R201C variant, whole-cell patch clamp in acute brain slices from L2/3 and CA1 neurons, comparison with KCNQ3 R231C knock-in\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knock-in models with direct electrophysiological readout in native neurons across multiple cell types\",\n      \"pmids\": [\"37607817\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KCNQ2 encodes the Kv7.2 voltage-gated K+ channel subunit that, as a homomeric or KCNQ3/5 heteromeric tetramer anchored to axon initial segments and nodes of Ranvier via AnkG (CK2-phosphorylation-dependent), conducts the low-threshold, slowly activating M-current that controls neuronal excitability; calmodulin binds constitutively to two C-terminal IQ-like motifs and is essential for ER exit, surface trafficking, and channel function; PIP2 is required to keep the channel open and its depletion via Gq/PLC signaling downstream of muscarinic receptors is the primary mechanism of M-current suppression; additional post-translational regulation includes ubiquitination by Nedd4-2 (counteracted by SGK-1), phosphorylation by PKC (at S559, suppressing M-current), CK2 phosphorylation of calmodulin (enhancing channel activity), GSK3β phosphorylation (inhibiting channel), and SUMOylation (impairing PIP2 and CaM binding); loss-of-function mutations cause haploinsufficiency or dominant-negative channel suppression leading to neonatal epilepsy, while gain-of-function voltage-sensor mutations produce cell-type-specific hyper- or hypoexcitability and also cause epilepsy.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"KCNQ2 encodes the Kv7.2 voltage-gated K+ channel subunit that, together with KCNQ3 (and KCNQ5), generates the neuronal M-current controlling excitability and action-potential firing; mouse knockout and the Szt1 C-terminal deletion eliminate or reduce M-current, impair spike-frequency adaptation, and produce convulsant hypersensitivity, establishing KCNQ2 as a brake on neuronal excitability [#11, #13]. Kv7.2 assembles with Kv7.3 through a C-terminal A-domain interaction into a predominantly 2:2 heterotetramer, and co-assembly markedly increases surface expression of both subunits [#2, #5, #14]; KCNQ2 also forms KCNQ3-independent heteromers with KCNQ5 in native brain [#30]. The channel is anchored at axon initial segments and nodes of Ranvier alongside Nav channels via ankyrin-G, an interaction augmented by CK2 phosphorylation, with FGF14 acting as an organizer that bridges Nav1.6 and KCNQ2 at the AIS [#0, #7, #19]. Calmodulin binds constitutively to two C-terminal IQ-like motifs and is required for ER exit, heteromeric assembly, AIS targeting, and current generation; loss of CaM binding causes ER retention [#1, #3, #15]. Channel opening requires membrane PIP2, and M-current is suppressed when Gq-coupled muscarinic receptors activate PLC to hydrolyze PIP2, with PIP2 hydrolysis as the rate-limiting step [#4, #23]. Activity is further tuned by a tethered CK2/PP1 module (CK2 phosphorylates CaM to strengthen binding and PIP2 resistance), PKC phosphorylation at S559 driving neurotransmitter-induced suppression, a serine cluster phosphorylated by CDK5/p38/CaMKII/PKA that sets PIP2 sensitivity, Nedd4-2 ubiquitination, GSK3\\u03b2 phosphorylation, and SUMOylation that impairs PIP2 and CaM binding [#9, #25, #26, #8, #10, #27]. Loss-of-function mutations cause neonatal epilepsy and encephalopathy through haploinsufficiency, dominant-negative current reduction, or mislocalization away from the AIS, while gain-of-function voltage-sensor mutations that stabilize the activated state also cause epilepsy with cell-type-specific effects on excitability [#11, #16, #18, #6, #34].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Established that KCNQ2 is genetically required for the neuronal M-current in vivo and that reduced dosage causes hyperexcitability, defining its physiological role as an excitability brake.\",\n      \"evidence\": \"Homozygous and heterozygous Kcnq2 knockout mice with pentylenetetrazole seizure-threshold assay\",\n      \"pmids\": [\"10854243\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve subcellular site of M-current control\", \"Homozygous lethality limited adult analysis\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Showed that KCNQ2/KCNQ3 co-assembly drives the large M-current chiefly by boosting surface expression, explaining why both subunits are needed for robust current.\",\n      \"evidence\": \"Single-channel recording and surface biotinylation in Xenopus oocytes, with a BFNC C-terminal truncation mutant\",\n      \"pmids\": [\"10788442\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trafficking machinery mediating the surface boost unidentified\", \"Did not define assembly stoichiometry\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Identified calmodulin as a constitutive auxiliary subunit essential for current generation, linking the channel to Ca2+ signaling.\",\n      \"evidence\": \"Yeast two-hybrid, co-IP from mouse brain, CHO electrophysiology, CaM-motif mutagenesis\",\n      \"pmids\": [\"12223552\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which CaM enables current not yet resolved (later shown to be trafficking)\", \"Ca2+ vs apoCaM roles unclear at this stage\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Mapped the C-terminal A-domain as the determinant of KCNQ2/KCNQ3 heteromeric assembly, defining the molecular basis of subunit selectivity.\",\n      \"evidence\": \"Chimeric channel construction and two-microelectrode voltage clamp in oocytes\",\n      \"pmids\": [\"12640002\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural model of the interface\", \"Stoichiometry not determined\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Localized KCNQ2 to axon initial segments and nodes of Ranvier in complex with ankyrin-G and Nav channels, placing M-current control at the spike-initiation zone.\",\n      \"evidence\": \"Immunohistochemistry, co-IP from brain, pharmacological electrophysiology in nerves\",\n      \"pmids\": [\"14762142\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"AnkG binding site and regulation not defined\", \"Did not establish how channel:Nav ratio is set\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Reconstituted the Gq-PLC-PIP2 cascade for muscarinic M-current suppression, establishing PIP2 depletion as the primary suppression mechanism.\",\n      \"evidence\": \"Whole-cell patch and GFP-PH PIP2 probe in tsA-201 cells with G-protein and RGS2 manipulations\",\n      \"pmids\": [\"15173220\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Rate-limiting step not yet pinpointed\", \"PIP2 binding residues on the channel unmapped\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrated in native CA1 neurons that KCNQ2 supplies the M-current regulating spike-frequency adaptation, connecting molecular function to firing control.\",\n      \"evidence\": \"Perforated-patch electrophysiology in Szt1 mutant mouse hippocampal slices\",\n      \"pmids\": [\"16481438\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address other afterhyperpolarization currents\", \"Behavioral consequences not tested\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Identified additional regulatory inputs (PP2A-Bgamma enhancement, GSK3beta inhibition) and dominant-negative truncation variants, broadening the post-translational regulatory landscape.\",\n      \"evidence\": \"Yeast two-hybrid, heterologous electrophysiology, GSK3beta phosphorylation assay\",\n      \"pmids\": [\"16733521\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab with limited biochemical follow-up\", \"GSK3beta phospho-sites not mapped\", \"Physiological relevance untested\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Showed CaM binding controls ER export, mechanistically explaining the requirement for CaM in current generation and a BFNC mutation's loss of function.\",\n      \"evidence\": \"Live-cell imaging, subcellular fractionation, CaM overexpression/sequestration in transfected cells\",\n      \"pmids\": [\"17993630\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address AIS targeting specifically\", \"Quality-control machinery sensing CaM occupancy unknown\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Established Nedd4-2 as a direct ubiquitin ligase reducing KCNQ2/3 current, adding degradative control over channel abundance.\",\n      \"evidence\": \"GST pulldown, co-IP, ubiquitination assay and electrophysiology in oocytes\",\n      \"pmids\": [\"17322297\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance of Nedd4-2 regulation not shown\", \"Ubiquitination sites not mapped\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Distinguished receptor-specific M-current suppression mechanisms, showing bradykinin uses Ca2+/IP3 or PIP2 depletion depending on PIP2 supply.\",\n      \"evidence\": \"Tubby-PIP2 sensor imaging in sympathetic neurons with pharmacological perturbation\",\n      \"pmids\": [\"17395626\", \"17447081\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Relative contribution in intact circuits unclear\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Expanded KCNQ2's contribution to the medium and slow afterhyperpolarization currents in hippocampal neurons, linking it to spike-train regulation.\",\n      \"evidence\": \"Patch clamp in KCNQ2/3 knockout hippocampal slices with KCNQ pharmacology\",\n      \"pmids\": [\"19060215\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Hippocalcin link not mechanistically resolved\", \"Did not separate KCNQ2 vs KCNQ3 contributions fully\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identified PIP2 hydrolysis as the rate-limiting step of muscarinic suppression, refining the kinetic model of M-current control.\",\n      \"evidence\": \"Pairwise FRET of each signaling step plus electrophysiology and PLC overexpression\",\n      \"pmids\": [\"19332618\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Channel PIP2 affinity determinants not mapped here\", \"In vivo kinetics not addressed\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Determined that Kv7.2/7.3 assembles predominantly as a 2:2 tetramer with non-fixed subunit arrangement, defining channel architecture.\",\n      \"evidence\": \"Atomic force microscopy of antibody-decorated isolated channel complexes\",\n      \"pmids\": [\"22334706\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of variable arrangement unresolved\", \"No atomic structure\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Revealed that calmodulin orchestrates heteromeric assembly and AIS targeting, integrating the trafficking and assembly roles of CaM.\",\n      \"evidence\": \"Co-IP, AIS immunofluorescence in neurons, CaM rescue and mutagenesis\",\n      \"pmids\": [\"24333508\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How CaM couples to AIS anchoring machinery unclear\", \"Apo- vs Ca2+-CaM roles not fully separated\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showed a tethered CK2/PP1 module sets channel activity, with CK2 phosphorylating CaM to strengthen binding and confer PIP2-depletion resistance.\",\n      \"evidence\": \"Co-IP of CK2/PP1, PP1-motif mutagenesis, CaM phosphorylation assay, electrophysiology in HEK and SCG neurons\",\n      \"pmids\": [\"24627475\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of the tethered module not defined\", \"In vivo role of PP1 tethering untested\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined AnkG-mediated anchoring with CK2-augmented binding and a splice-regulated mechanism setting the Nav:KCNQ ratio at the distal AIS.\",\n      \"evidence\": \"Pulldowns, co-IP, AnkG repeat mutagenesis, in vitro CK2 phosphorylation\",\n      \"pmids\": [\"25998125\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of distinct KCNQ2 vs KCNQ3 anchor sites incomplete\", \"Regulation of splice choice in vivo unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstrated a peripheral sensory role: conditional Kcnq2 deletion increases sensory neuron excitability and produces hyperalgesia and allodynia.\",\n      \"evidence\": \"Cre-Lox conditional knockout, DRG patch clamp, nociception behavior\",\n      \"pmids\": [\"24687876\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular trigger of pain phenotype not dissected\", \"Did not test M-current modulators in vivo\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Showed gain-of-function voltage-sensor mutations stabilize the activated state and cause epilepsy by reducing interneuron output, complicating the loss-of-function paradigm.\",\n      \"evidence\": \"Electrophysiology, disulfide trapping, structural and circuit modeling\",\n      \"pmids\": [\"25740509\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Circuit prediction not validated in native tissue at this stage\", \"No high-resolution structure of the activated state\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Distinguished dominant-negative encephalopathy mutations from haploinsufficient BFNC mutations and showed retigabine partial rescue, informing genotype-phenotype severity.\",\n      \"evidence\": \"Two-microelectrode voltage clamp and surface biotinylation across 7 mutations\",\n      \"pmids\": [\"24318194\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Native neuronal consequences not assessed\", \"Mechanism of dominant-negative suppression not structurally defined\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Established subcellular mislocalization (somatodendritic vs AIS) as a determinant of disease severity, beyond simple current reduction.\",\n      \"evidence\": \"Patch clamp, Western blot, AIS immunofluorescence comparing A294V and A294G in neurons\",\n      \"pmids\": [\"26007637\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trafficking step disrupted by A294V not identified\", \"Single residue comparison\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Mapped a serine cluster phosphorylated by CDK5/p38/CaMKII/PKA that tunes channel PIP2 sensitivity and receptor-specific suppression.\",\n      \"evidence\": \"Phosphoproteomics, in vitro kinase assay with purified C-terminus, Dr-VSP PIP2 assay, mutagenesis\",\n      \"pmids\": [\"27621207\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which kinase dominates in vivo unclear\", \"Did not test cluster phospho-state in disease\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Showed gain-of-function gating mutations (V175L, R198Q) cause encephalopathy without altering AIS localization, establishing gating change as a sufficient pathogenic mechanism.\",\n      \"evidence\": \"Patch clamp in CHO cells and AIS immunofluorescence in neurons\",\n      \"pmids\": [\"27030113\", \"27861786\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single mutations per study\", \"Circuit-level excitability not tested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined channel surface dynamics: AIS Kv7.2/7.3 is highly stable but undergoes calpain-dependent excitotoxic endocytosis under glutamate load, linking M-channels to excitotoxicity.\",\n      \"evidence\": \"Live imaging with SEP-TAC-Kv7.3 phluorin chimera and pharmacological dissection in hippocampal neurons\",\n      \"pmids\": [\"26888935\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance to seizure-induced injury not directly shown here\", \"Endocytic adaptor machinery undefined\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identified FGF14 as a positive regulator and AIS organizer that bridges Nav1.6 and KCNQ2, coordinating co-localization of the two channel classes.\",\n      \"evidence\": \"siRNA knockdown, co-IP, AIS immunofluorescence, patch clamp\",\n      \"pmids\": [\"27994149\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single study\", \"Structural basis of the bridging not resolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Linked CaM-binding-helix encephalopathy mutations to reduced surface expression, with M518V driving CaM loss, ubiquitination, and proteasomal degradation, and exposing novel PIP2 residues.\",\n      \"evidence\": \"Surface biotinylation, CaM co-IP, ubiquitination/proteasome assays, patch clamp, neuronal imaging\",\n      \"pmids\": [\"30008368\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Ligase responsible for M518V ubiquitination not identified\", \"Did not test rescue in vivo\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Established PKC phosphorylation at S559 as a key driver of neurotransmitter-induced M-current suppression with direct seizure and neuroprotection consequences in vivo.\",\n      \"evidence\": \"Kv7.2(S559A) knock-in mice, patch clamp, pilocarpine SE, histology, EEG\",\n      \"pmids\": [\"30146722\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Upstream receptor specificity for S559 not fully resolved\", \"Structural impact of phosphorylation unknown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Mapped helix B and pore residues (K552T, R553L, L268F) critical for CaM binding, axonal enrichment, and PIP2 potentiation, refining the structural map of regulatory residues.\",\n      \"evidence\": \"Mutation mapping, structural modeling, MD simulation, patch clamp and surface/internalization assays in neurons\",\n      \"pmids\": [\"32179837\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"MD-predicted PIP2 contacts not experimentally confirmed structurally\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Showed SUMOylation negatively regulates the channel by impairing PIP2 and CaM binding and that SENP2 deSUMOylation maintains M-current, adding a SUMO-based regulatory layer.\",\n      \"evidence\": \"SENP2 knockout mice, co-IP, SUMO-site mutagenesis, binding and electrophysiology assays\",\n      \"pmids\": [\"34509475\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"SUMO-acceptor sites and physiological triggers incompletely defined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified M1R/PKC phosphorylation at T217 in nucleus accumbens regulating aversive learning, extending KCNQ2 function to reward-circuit behavior.\",\n      \"evidence\": \"In vitro PKC kinase assay, phospho-specific detection in vivo, conditional NAc knockout, behavior\",\n      \"pmids\": [\"34878647\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"How T217 phosphorylation alters channel gating not defined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrated KCNQ2 forms KCNQ3-independent heteromers with KCNQ5 in native brain, expanding the repertoire of M-channel compositions.\",\n      \"evidence\": \"Split-intein covalent tandems, electrophysiology, native-brain mass spectrometry\",\n      \"pmids\": [\"35320039\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional distinction of KCNQ2/5 vs KCNQ2/3 channels in vivo unclear\", \"Stoichiometry of trimeric assemblies undefined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified BACE1 as a partner that recruits KCNQ2/3 to lipid rafts via BACE1 palmitoylation, adding membrane-microdomain control of channel localization.\",\n      \"evidence\": \"Spectral FRET with raft/non-raft probes and palmitoylation-deficient BACE1 in HEK cells\",\n      \"pmids\": [\"35201266\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Heterologous system only\", \"Functional impact on M-current not quantified\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Linked Kcnq2 downregulation in ventral hippocampal glutamatergic neurons to ketamine's sustained antidepressant action, implicating M-channels in mood regulation.\",\n      \"evidence\": \"Cell-type transcriptomics, electrophysiology, retigabine augmentation, behavior in mice\",\n      \"pmids\": [\"35649415\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism connecting ketamine to Kcnq2 downregulation not reconstituted\", \"Causality of downregulation vs marker unclear\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showed that a single gain-of-function variant (R201C) produces opposite excitability effects in different neuron types, resolving why GOF mutations cause epilepsy.\",\n      \"evidence\": \"Transgenic R201C knock-in mice with patch clamp in L2/3 and CA1 neurons, compared to KCNQ3 R231C\",\n      \"pmids\": [\"37607817\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Circuit-level consequence of opposing cell-type effects not fully resolved\", \"Behavioral phenotype not detailed here\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the many post-translational modifications, accessory partners, and channel compositions are integrated to set M-current in specific neuron types in vivo remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified in vivo model of combined CaM/PIP2/phospho/SUMO regulation\", \"Functional roles of KCNQ2/5 and trimeric channels in distinct circuits undefined\", \"No high-resolution structure of the human Kv7.2 channel in the corpus\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [2, 11, 13]},\n      {\"term_id\": \"GO:0005216\", \"supporting_discovery_ids\": [2, 11]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 2, 7, 21]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 11, 13]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4, 23]}\n    ],\n    \"complexes\": [\n      \"Kv7.2/Kv7.3 heterotetramer\",\n      \"Kv7.2/Kv7.5 heteromeric channel\",\n      \"axon initial segment ankyrin-G complex\"\n    ],\n    \"partners\": [\n      \"KCNQ3\",\n      \"KCNQ5\",\n      \"CALM1\",\n      \"ANK3\",\n      \"NEDD4L\",\n      \"FGF14\",\n      \"BACE1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}