{"gene":"DPP6","run_date":"2026-04-28T17:46:03","timeline":{"discoveries":[{"year":2003,"finding":"DPPX (DPP6) was purified as a novel component of neuronal A-type K+ channel complexes from rat brain membranes. It associates with Kv4 pore-forming subunits, facilitates their trafficking and membrane targeting, and reconstitutes native A-type K+ channel properties in heterologous expression systems. It co-localizes with Kv4 subunits in the somatodendritic compartment of CNS neurons.","method":"Biochemical purification of K+ channel complexes from rat brain membranes, co-immunoprecipitation, heterologous expression reconstitution, immunolocalization","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 1–2 — original discovery with multiple orthogonal methods (purification, Co-IP, reconstitution, localization), highly cited foundational paper","pmids":["12575952"],"is_preprint":false},{"year":2004,"finding":"X-ray crystal structure of the extracellular domain of human DPPX at 3.0 Å resolution revealed a dimeric structure homologous to DPP-IV. The active-site serine is absent and the residue arrangement is inconsistent with canonical serine proteases, establishing that DPPX lacks dipeptidyl aminopeptidase catalytic activity. The structure suggests surface electrostatic changes based on histidine protonation state that could modulate Kv4.2 interaction.","method":"X-ray crystallography, active-site structural analysis","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with functional validation of lack of protease activity","pmids":["15476821"],"is_preprint":false},{"year":2001,"finding":"DPPX-S and DPPX-L are brain-specific glycoproteins that are synthesized with high-mannose oligosaccharides and processed to complex-type sugar chains before reaching the cell surface. Despite structural homology to DPP-IV, mutagenesis to introduce the canonical Gly-X-Ser-X-Gly active-site motif failed to confer dipeptidyl aminopeptidase activity, confirming catalytic incompetence.","method":"Cell-free translation, COS-1 cell transfection, immunofluorescence, enzymatic activity assay, site-directed mutagenesis, immunoblot","journal":"Journal of biochemistry","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis plus activity assay, multiple methods confirming lack of enzymatic activity","pmids":["11173531"],"is_preprint":false},{"year":2006,"finding":"Three alternatively spliced DPPX isoforms (DPPX-S, DPPX-L, DPPX-K) all modify the voltage dependence and kinetic properties of Kv4.2 channels expressed in Xenopus oocytes. Deletion of the variable N-terminus showed the N-terminus is not required for Kv4 channel modulation, placing the functional domain in the transmembrane or extracellular region.","method":"Xenopus oocyte expression, electrophysiology, deletion mutagenesis, in situ hybridization","journal":"Brain research","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with mutagenesis in multiple isoforms","pmids":["16764835"],"is_preprint":false},{"year":2008,"finding":"ISA channel complexes contain four subunits each of Kv4.2 and DPP6 (4:4 stoichiometry), established by both biophysical methods using tandem-linked subunits and direct biochemical amino acid analysis of purified complexes.","method":"Tandem-linked subunit constructs (functional), amino acid analysis of purified channel complexes (biochemical)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstitution plus biochemical quantification, two orthogonal methods in one study","pmids":["18364354"],"is_preprint":false},{"year":2008,"finding":"DPP6 (DPPX) localization in brain closely mirrors that of Kv4.2, with both enriched in dendrites of neurons that co-express them. Additionally, DPP6 was found in hippocampal mossy fiber axons that lack Kv4 proteins, suggesting a Kv4-independent function in axons.","method":"Immunohistochemistry with DPP6 and Kv4.2 antibodies, subcellular fractionation, immunofluorescence","journal":"Frontiers in molecular neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization experiment with functional implication, single lab","pmids":["18978958"],"is_preprint":false},{"year":2008,"finding":"siRNA knockdown of DPPX in hippocampal CA1 pyramidal neurons caused depolarizing shifts in steady-state inactivation and activation curves, slowed inactivation, and delayed recovery from inactivation of A-type currents. This resulted in decreased subthreshold excitability (reduced input resistance, delayed AP onset, increased AP threshold) and slowed AP rise and repolarization suprathreshold.","method":"siRNA knockdown in neurons, voltage-clamp and current-clamp electrophysiology, computer simulations","journal":"Journal of neurophysiology","confidence":"High","confidence_rationale":"Tier 2 — clean KD with defined biophysical and physiological phenotypic readouts, supported by computational modeling","pmids":["18667548"],"is_preprint":false},{"year":2009,"finding":"DPP6-S is necessary and sufficient to increase the unitary conductance (gamma) of Kv4.2 channels from ~4 pS to ~7.5 pS (matching native cerebellar granule neuron channels). Charge neutralization of two N-terminal acidic residues in DPP6-S eliminated this conductance increase, implicating electrostatic interactions. DPP6 knockout mouse CGN channels had conductance indistinguishable from Kv4.2 expressed alone.","method":"Single-channel patch clamp in heterologous cells and DPP6-KO mouse neurons, site-directed mutagenesis","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1 — reconstitution, KO confirmation, mutagenesis identifying specific residues, multiple orthogonal approaches","pmids":["19279261"],"is_preprint":false},{"year":2009,"finding":"Co-expression of DPPX-S with Kv4.2 dramatically redistributes Kv4.2 from intracellular retention to plasma membrane expression, alters Kv4.2 phosphorylation pattern (to resemble that in brain), changes detergent solubility and stability. These effects are similar to those of KChIP auxiliary subunits. KChIP4a, which inhibits other KChIPs, also inhibits DPPX-S effects, consistent with formation of a ternary Kv4.2/DPPX-S/KChIP complex early in biosynthesis.","method":"Co-expression in heterologous cells, immunofluorescence, tandem MS phosphorylation analysis, detergent solubility assay","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (imaging, MS, biochemical), reveals mechanism of convergent auxiliary subunit action","pmids":["19441798"],"is_preprint":false},{"year":2011,"finding":"DPP6 knockout mice lacking the Kv4 transmembrane auxiliary subunit DPP6 show a specific loss of A-type K+ current in distal dendrites of CA1 hippocampal pyramidal neurons, accompanied by a depolarizing shift in activation voltage dependence. This results in hyperexcitable dendrites with enhanced dendritic AP back-propagation, calcium electrogenesis, and enhanced LTP induction, without major effects on somatic firing.","method":"Dendritic patch-clamp recordings from DPP6-KO mice, calcium imaging, LTP induction","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with multiple compartment-specific electrophysiological and imaging readouts","pmids":["21943606"],"is_preprint":false},{"year":2013,"finding":"DPP6 knockdown or genetic deletion reduces dendritic filopodia formation and stability during early hippocampal neuronal development, leading to sparser dendritic branching, fewer spines, and fewer functional synapses in adult neurons. This role in dendritic morphogenesis is independent of Kv4.2. DPP6 was found to interact with a filopodia-associated myosin and with fibronectin in the extracellular matrix.","method":"shRNA knockdown, DPP6-KO mice, live imaging, electrophysiology, co-immunoprecipitation with myosin and fibronectin","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — KD and KO with multiple readouts plus binding partners identified; Kv4.2-independence established by epistasis","pmids":["23912628"],"is_preprint":false},{"year":2014,"finding":"The cysteine-rich domain of DPP6 extracellular region is required for ER export and cell surface expression. Disulfide bridges at C349/C356 and C465/C468 are necessary for enhancement of Kv4.2 surface expression but not for physical interaction with Kv4.2. The short intracellular N-terminal and transmembrane domains of DPP6 associate with Kv4.2 and accelerate recovery from inactivation, while the entire extracellular domain is required for Kv4.2 surface expression enhancement and stabilization.","method":"Domain deletion/mutagenesis, disulfide bridge mutagenesis, co-immunoprecipitation, surface biotinylation, electrophysiology","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — systematic mutagenesis with functional validation separating binding from trafficking roles","pmids":["25190807"],"is_preprint":false},{"year":2008,"finding":"A novel DPP6 splice isoform, DPP6-E, produces ternary Kv4 channels with very fast inactivation kinetics when expressed with Kv4.2 and KChIP1. DPP6-E is selectively expressed in cerebellar granule neurons, hippocampal pyramidal cells, and superior colliculus neurons, accounting for past discrepancies between reconstituted and native Kv4 channel kinetics in these cells.","method":"Heterologous expression, electrophysiology, in situ hybridization","journal":"Neuroscience letters","confidence":"Medium","confidence_rationale":"Tier 2 — functional reconstitution matched to native cell expression pattern","pmids":["19007856"],"is_preprint":false},{"year":2008,"finding":"DPPX association with Kv4 channels in rabbit carotid body chemoreceptor cells confers TEA sensitivity (increased block by external TEA) to natively TEA-insensitive Kv4 channels. siRNA knockdown of DPPX reduced K(O2) currents and altered TEA sensitivity, establishing DPPX as an integral component of oxygen-sensitive K+ currents in these cells.","method":"siRNA knockdown in native cells, pharmacological TEA block, heterologous co-expression electrophysiology","journal":"The Journal of general physiology","confidence":"Medium","confidence_rationale":"Tier 2 — siRNA in native cells plus heterologous reconstitution, single lab","pmids":["18411327"],"is_preprint":false},{"year":2017,"finding":"Patient DPPX antibodies (predominantly IgG1 and IgG4) caused a reversible decrease of DPPX clusters and Kv4.2 protein at the surface of cultured neurons when applied, with recovery upon antibody removal. In hippocampal neurons, anti-DPPX-IgG decreased membrane expression of both DPPX and Kv4.2, and increased enteric nervous system neuron excitability.","method":"Immunocytochemistry on cultured neurons, immunoblot of neuronal membrane fractions, voltage-sensitive dye imaging of enteric neurons","journal":"Neurology","confidence":"Medium","confidence_rationale":"Tier 2 — direct antibody application experiments with quantified protein level and functional readouts","pmids":["28258082"],"is_preprint":false},{"year":2013,"finding":"Dnmt3b epigenetically silences Dpp6 expression through promoter DNA methylation. Depletion of Dnmt3b increases Dpp6 mRNA and protein. Ectopic DPP6 overexpression in P19 cells inhibits retinoic acid-induced neuronal differentiation, indicating DPP6 functions as a negative regulator of this differentiation process.","method":"ChIP, bisulfite sequencing, COBRA, methylation-specific PCR, Dnmt3b knockdown, DPP6 overexpression differentiation assay","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — multiple epigenetic methods plus functional overexpression phenotype, single lab","pmids":["23409053"],"is_preprint":false},{"year":2019,"finding":"A missense variant DPP6-L747P identified in families with early repolarization syndrome causes gain-of-function of transient outward K+ current (Ito) when co-expressed with Kv4.3 and KChIP2 in HEK293 cells: increased macroscopic current density, altered activation and inactivation slopes, and reduced recovery time constant.","method":"Whole-cell patch clamp, western blot, immunofluorescence in HEK293 cells","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 — functional electrophysiology with mutant vs WT comparison, single lab","pmids":["31476289"],"is_preprint":false},{"year":2020,"finding":"Increased DPP6 expression in iPSC-derived cortical neurons from schizophrenia patients causes neuronal hypoexcitability. Lentiviral shRNA knockdown of DPP6 or pharmacological block of Kv4.2 with AmmTx3 both reversed the hypoexcitability, establishing a causal link between elevated DPP6/Kv4.2 activity and decreased neuronal firing in this model.","method":"iPSC differentiation, RNA sequencing, multielectrode array recordings, calcium imaging, lentiviral shRNA, pharmacological block","journal":"Stem cells and development","confidence":"Medium","confidence_rationale":"Tier 2 — causal rescue experiments with shRNA and pharmacology, multiple readouts","pmids":["33143549"],"is_preprint":false},{"year":2019,"finding":"Missense variants in DPP6 found in early-onset Alzheimer's disease and frontotemporal dementia patients destabilize DPP6 protein and reduce its membrane expression in vitro, and reduced DPP6 and Kv4.2 expression was confirmed in brain tissue of missense variant carriers.","method":"In vitro expression assay of patient variants, western blot, immunofluorescence, brain tissue immunoblot","journal":"Acta neuropathologica","confidence":"Medium","confidence_rationale":"Tier 2–3 — in vitro functional assay plus human brain tissue confirmation, single lab","pmids":["30874922"],"is_preprint":false},{"year":2015,"finding":"Patient anti-DPPX IgG applied to hippocampal neurons decreased membrane expression of both DPPX and Kv4.2, as measured by immunoblot of purified neuronal membranes. Application to enteric nervous system preparations increased neuronal action potential frequency, demonstrating direct pathogenic antibody effects on both brain and gut neurons.","method":"Purified patient IgG application, immunoblot of neuronal membranes, voltage-sensitive dye imaging of enteric neurons","journal":"Neurology","confidence":"Medium","confidence_rationale":"Tier 2 — purified antibody experiments with quantified membrane protein and functional electrophysiological readouts","pmids":["26291285"],"is_preprint":false},{"year":2009,"finding":"DPP6 overexpression in the myocardium of familial idiopathic ventricular fibrillation risk-haplotype carriers shows ~20-fold increased DPP6 mRNA compared to controls, implicating increased DPP6 expression as the pathogenetic mechanism in this cardiac arrhythmia syndrome. DPP6 was proposed as a component of the transient outward current in the heart.","method":"Haplotype-sharing genome-wide analysis, qRT-PCR of myocardial DPP6 mRNA","journal":"American journal of human genetics","confidence":"Low","confidence_rationale":"Tier 3 — expression quantification without direct functional electrophysiological validation in cardiac tissue","pmids":["19285295"],"is_preprint":false}],"current_model":"DPP6 is a single-pass transmembrane auxiliary subunit of neuronal Kv4-family A-type K+ channels: it physically associates with Kv4 pore-forming subunits in a 4:4 stoichiometry, promotes their trafficking out of the ER and to the plasma membrane via disulfide-bonded extracellular cysteine-rich domains, shifts channel voltage dependence, accelerates inactivation and recovery kinetics through its intracellular/transmembrane domains, and increases unitary conductance via electrostatic interactions of N-terminal acidic residues; beyond its role as a Kv4 auxiliary subunit, DPP6 independently regulates dendritic filopodia formation and synaptic development through interactions with myosin and extracellular fibronectin, and loss of DPP6 in mice produces dendritic hyperexcitability, synaptic loss, and progressive Alzheimer's-like neurodegeneration."},"narrative":{"teleology":[{"year":2001,"claim":"Establishing that DPP6, despite structural homology to DPP-IV, is catalytically inactive resolved a key question about whether this protein functions as a peptidase or has a non-enzymatic role.","evidence":"Mutagenesis introducing the canonical active-site motif failed to confer dipeptidyl aminopeptidase activity in COS-1 cells","pmids":["11173531"],"confidence":"High","gaps":["Biological function remained unknown at this point","Mechanism of glycosylation processing and its functional significance not explored"]},{"year":2003,"claim":"Identifying DPP6 as a native component of neuronal Kv4 A-type K+ channel complexes established its primary physiological role and explained how native ISA channel properties differ from reconstituted Kv4 alone.","evidence":"Biochemical purification from rat brain, co-immunoprecipitation with Kv4, heterologous reconstitution of native-like A-type currents, and somatodendritic co-localization","pmids":["12575952"],"confidence":"High","gaps":["Stoichiometry of the complex unknown","Which DPP6 domains mediate Kv4 interaction and modulation unresolved"]},{"year":2004,"claim":"The crystal structure of the DPP6 extracellular domain confirmed the structural basis for its catalytic incompetence and suggested pH-dependent electrostatic modulation of Kv4 interaction.","evidence":"X-ray crystallography at 3.0 Å resolution of human DPPX extracellular domain","pmids":["15476821"],"confidence":"High","gaps":["No structure of the DPP6–Kv4 complex to reveal interaction interface","Histidine protonation-dependent modulation not functionally tested"]},{"year":2006,"claim":"Demonstrating that all three splice isoforms modulate Kv4.2 and that the variable N-terminus is dispensable for channel modulation localized the core modulatory function to the transmembrane/extracellular region.","evidence":"Deletion mutagenesis and electrophysiology of DPPX-S, -L, -K isoforms in Xenopus oocytes","pmids":["16764835"],"confidence":"High","gaps":["Specific transmembrane or extracellular residues mediating gating modulation not identified","Isoform-specific functional differences in native neurons unclear"]},{"year":2008,"claim":"Determining the 4:4 stoichiometry of DPP6:Kv4.2 in ISA complexes defined the quaternary architecture and constrained models of auxiliary subunit–pore interaction.","evidence":"Tandem-linked subunit constructs and amino acid analysis of purified complexes","pmids":["18364354"],"confidence":"High","gaps":["Arrangement of DPP6 subunits around the Kv4 tetramer not resolved","Whether KChIPs simultaneously associate in the same 4:4 complex not quantified"]},{"year":2008,"claim":"Knockdown of DPP6 in native CA1 neurons demonstrated its necessity for normal A-type current gating and revealed compartment-specific effects on neuronal excitability, while DPP6 localization in Kv4-lacking mossy fiber axons suggested Kv4-independent roles.","evidence":"siRNA knockdown with dendritic and somatic patch-clamp in hippocampal neurons; immunohistochemistry showing DPP6 in mossy fibers","pmids":["18667548","18978958"],"confidence":"High","gaps":["Nature of Kv4-independent function in axons unknown","Whether DPP6 loss affects synaptic transmission not tested"]},{"year":2008,"claim":"Discovery of the DPP6-E splice isoform explained discrepancies between reconstituted and native channel kinetics in cerebellar granule neurons and hippocampal pyramidal cells, establishing isoform-specific tuning of Kv4 gating.","evidence":"Heterologous expression electrophysiology with DPP6-E/Kv4.2/KChIP1, matched to in situ hybridization expression pattern","pmids":["19007856"],"confidence":"Medium","gaps":["Structural basis for DPP6-E's faster inactivation not determined","Whether DPP6-E and other isoforms co-assemble in native complexes unknown"]},{"year":2009,"claim":"Identifying that DPP6-S increases Kv4.2 unitary conductance via two N-terminal acidic residues revealed a distinct electrostatic mechanism of channel modulation separate from gating effects.","evidence":"Single-channel recording in heterologous cells and DPP6-KO mouse cerebellar granule neurons, charge-neutralization mutagenesis","pmids":["19279261"],"confidence":"High","gaps":["How intracellular acidic residues influence the extracellular conduction pathway not structurally explained","Whether other isoforms share this conductance effect untested"]},{"year":2009,"claim":"Demonstrating that DPP6 promotes Kv4.2 ER-to-surface trafficking, alters its phosphorylation to brain-like patterns, and converges with KChIP action revealed the biosynthetic mechanism underlying auxiliary subunit regulation of channel density.","evidence":"Co-expression in heterologous cells with immunofluorescence, tandem MS phosphorylation, detergent solubility, and KChIP4a epistasis","pmids":["19441798"],"confidence":"High","gaps":["Identity of kinases/phosphatases responsible for DPP6-dependent Kv4.2 phosphorylation changes unknown","Whether ternary complex forms co-translationally or post-translationally unresolved"]},{"year":2011,"claim":"DPP6 knockout mice revealed that DPP6 is the dominant determinant of distal dendritic A-type current, and its loss causes dendritic hyperexcitability and enhanced LTP without affecting somatic firing, establishing compartment-specific physiology.","evidence":"Dendritic and somatic patch-clamp recordings, calcium imaging, and LTP induction protocols in DPP6-KO mice","pmids":["21943606"],"confidence":"High","gaps":["Whether behavioral or cognitive phenotypes accompany dendritic hyperexcitability not assessed","Compensatory changes in other auxiliary subunits not examined"]},{"year":2013,"claim":"Demonstrating that DPP6 promotes dendritic filopodia formation and synaptogenesis independently of Kv4.2, via interactions with myosin and fibronectin, established a second, non-channel function in neural development.","evidence":"shRNA knockdown and DPP6-KO mice with live imaging, electrophysiology, co-immunoprecipitation with myosin and fibronectin","pmids":["23912628"],"confidence":"High","gaps":["Which myosin isoform mediates the interaction not specified","How DPP6–fibronectin interaction signals to the cytoskeleton mechanistically unclear","Whether this developmental role extends to non-hippocampal brain regions untested"]},{"year":2014,"claim":"Systematic domain dissection separated DPP6's binding, gating, and trafficking functions: the transmembrane/N-terminal domains bind Kv4.2 and accelerate recovery, while the extracellular cysteine-rich domain with specific disulfide bonds drives ER export and surface expression.","evidence":"Domain deletions, cysteine mutagenesis, co-immunoprecipitation, surface biotinylation, electrophysiology","pmids":["25190807"],"confidence":"High","gaps":["Atomic-resolution structure of DPP6–Kv4 interface still lacking","Whether additional extracellular domain functions exist beyond trafficking unresolved"]},{"year":2015,"claim":"Pathogenic anti-DPPX autoantibodies from patients directly reduce surface DPP6 and Kv4.2, increasing neuronal excitability in both brain and enteric neurons, establishing a molecular mechanism for autoimmune DPPX encephalitis.","evidence":"Purified patient IgG applied to hippocampal neurons and enteric nervous system preparations with membrane immunoblot and voltage-sensitive dye recording","pmids":["26291285","28258082"],"confidence":"Medium","gaps":["Whether antibody-mediated internalization or cross-linking is the primary mechanism of surface loss unclear","Long-term in vivo pathogenic effects not modeled"]},{"year":2019,"claim":"DPP6 missense variants identified in early-onset Alzheimer's disease and frontotemporal dementia patients destabilize the protein and reduce membrane expression, linking DPP6 loss-of-function to neurodegeneration, while a gain-of-function variant (L747P) in early repolarization syndrome enhances Ito current, linking DPP6 to cardiac arrhythmia.","evidence":"In vitro expression assays of patient variants, brain tissue immunoblot; whole-cell patch clamp of L747P with Kv4.3/KChIP2 in HEK293 cells","pmids":["30874922","31476289"],"confidence":"Medium","gaps":["Causal role of DPP6 variants in neurodegeneration not proven by rescue or animal models","Mechanism by which L747P enhances current (trafficking vs gating) not distinguished","Whether cardiac DPP6 functions with Kv4.3 in native cardiomyocytes not directly shown"]},{"year":2020,"claim":"Elevated DPP6 expression in schizophrenia patient iPSC-derived neurons causally drives hypoexcitability, reversible by DPP6 knockdown or Kv4 block, linking DPP6 dosage to disease-relevant excitability changes.","evidence":"iPSC cortical neurons, RNA-seq, MEA recordings, calcium imaging, lentiviral shRNA rescue, AmmTx3 pharmacology","pmids":["33143549"],"confidence":"Medium","gaps":["Whether DPP6 upregulation is a primary genetic effect or secondary in schizophrenia not resolved","Circuit-level consequences of neuronal hypoexcitability not modeled"]},{"year":null,"claim":"No high-resolution structure of the DPP6–Kv4 complex exists, the molecular basis of how the transmembrane domain accelerates gating transitions remains unresolved, and the signaling pathway linking DPP6's extracellular fibronectin interaction to cytoskeletal remodeling during synaptogenesis is unknown.","evidence":"","pmids":[],"confidence":"High","gaps":["Cryo-EM or crystal structure of the full DPP6–Kv4–KChIP ternary complex needed","Mechanism of DPP6-mediated filopodia signaling uncharacterized","In vivo validation of DPP6 variants as causative for neurodegeneration lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,3,6,7,9,11]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[4,8,11]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,5,8,11,14]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[8,11]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,6,7,9,10]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,8,11]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[10,15]}],"complexes":["Kv4.2/DPP6/KChIP ternary channel complex"],"partners":["KCND2","KCND3","KCNIP1","KCNIP2","KCNIP4","FN1"],"other_free_text":[]},"mechanistic_narrative":"DPP6 is a catalytically inactive single-pass transmembrane auxiliary subunit of neuronal Kv4-family voltage-gated potassium channels that shapes A-type K+ current properties and regulates dendritic development. DPP6 assembles with Kv4 pore-forming subunits in a 4:4 stoichiometry, promotes their ER export and plasma membrane trafficking via disulfide-bonded cysteine-rich extracellular domains, shifts channel voltage dependence, accelerates inactivation and recovery kinetics through its transmembrane/intracellular domains, and increases unitary conductance through electrostatic interactions of N-terminal acidic residues [PMID:12575952, PMID:18364354, PMID:25190807, PMID:19279261]. Loss of DPP6 in knockout mice produces dendritic hyperexcitability with enhanced back-propagating action potentials and augmented LTP in hippocampal CA1 neurons [PMID:21943606], and independently of Kv4.2, DPP6 promotes dendritic filopodia formation and synaptogenesis through interactions with myosin and fibronectin [PMID:23912628]. Missense variants in DPP6 that destabilize the protein and reduce its membrane expression have been identified in early-onset Alzheimer's disease and frontotemporal dementia patients, while a gain-of-function variant (L747P) causes early repolarization syndrome through enhanced transient outward K+ current [PMID:30874922, PMID:31476289]."},"prefetch_data":{"uniprot":{"accession":"P42658","full_name":"A-type potassium channel modulatory protein DPP6","aliases":["DPPX","Dipeptidyl aminopeptidase-like protein 6","Dipeptidyl aminopeptidase-related protein","Dipeptidyl peptidase 6","Dipeptidyl peptidase IV-like protein","Dipeptidyl peptidase VI","DPP VI"],"length_aa":865,"mass_kda":97.6,"function":"Promotes cell surface expression of the potassium channel KCND2 (PubMed:15454437, PubMed:19441798). Modulates the activity and gating characteristics of the potassium channel KCND2 (PubMed:18364354). Has no dipeptidyl aminopeptidase activity (PubMed:15476821, PubMed:8103397)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/P42658/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/DPP6","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":77,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/DPP6","total_profiled":1310},"omim":[{"mim_id":"616311","title":"INTELLECTUAL DEVELOPMENTAL DISORDER, AUTOSOMAL DOMINANT 33; MRD33","url":"https://www.omim.org/entry/616311"},{"mim_id":"612956","title":"VENTRICULAR FIBRILLATION, PAROXYSMAL FAMILIAL, 2; VF2","url":"https://www.omim.org/entry/612956"},{"mim_id":"608209","title":"DIPEPTIDYL PEPTIDASE X; DPP10","url":"https://www.omim.org/entry/608209"},{"mim_id":"603829","title":"VENTRICULAR FIBRILLATION, PAROXYSMAL FAMILIAL, 1; VF1","url":"https://www.omim.org/entry/603829"},{"mim_id":"126141","title":"DIPEPTIDYL PEPTIDASE VI; DPP6","url":"https://www.omim.org/entry/126141"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":55.9},{"tissue":"endometrium 1","ntpm":51.4}],"url":"https://www.proteinatlas.org/search/DPP6"},"hgnc":{"alias_symbol":["DPPX","DPL1"],"prev_symbol":[]},"alphafold":{"accession":"P42658","domains":[{"cath_id":"2.140.10.30","chopping":"279-435","consensus_level":"medium","plddt":95.6719,"start":279,"end":435},{"cath_id":"3.40.50.1820","chopping":"590-848","consensus_level":"medium","plddt":94.4529,"start":590,"end":848},{"cath_id":"2.40.128","chopping":"445-527","consensus_level":"medium","plddt":91.7689,"start":445,"end":527}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P42658","model_url":"https://alphafold.ebi.ac.uk/files/AF-P42658-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P42658-F1-predicted_aligned_error_v6.png","plddt_mean":86.69},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=DPP6","jax_strain_url":"https://www.jax.org/strain/search?query=DPP6"},"sequence":{"accession":"P42658","fasta_url":"https://rest.uniprot.org/uniprotkb/P42658.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P42658/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P42658"}},"corpus_meta":[{"pmid":"12575952","id":"PMC_12575952","title":"The CD26-related dipeptidyl aminopeptidase-like protein DPPX is a critical component of neuronal A-type K+ channels.","date":"2003","source":"Neuron","url":"https://pubmed.ncbi.nlm.nih.gov/12575952","citation_count":300,"is_preprint":false},{"pmid":"25320100","id":"PMC_25320100","title":"DPPX potassium channel antibody: frequency, clinical accompaniments, and outcomes in 20 patients.","date":"2014","source":"Neurology","url":"https://pubmed.ncbi.nlm.nih.gov/25320100","citation_count":209,"is_preprint":false},{"pmid":"18084291","id":"PMC_18084291","title":"Genetic variation in DPP6 is associated with susceptibility to amyotrophic lateral sclerosis.","date":"2007","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/18084291","citation_count":183,"is_preprint":false},{"pmid":"28258082","id":"PMC_28258082","title":"DPPX antibody-associated encephalitis: Main syndrome and antibody effects.","date":"2017","source":"Neurology","url":"https://pubmed.ncbi.nlm.nih.gov/28258082","citation_count":157,"is_preprint":false},{"pmid":"11463372","id":"PMC_11463372","title":"dpl-1 DP and efl-1 E2F act with lin-35 Rb to antagonize Ras signaling in C. elegans vulval development.","date":"2001","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/11463372","citation_count":150,"is_preprint":false},{"pmid":"24696508","id":"PMC_24696508","title":"Progressive encephalomyelitis with rigidity and myoclonus: a new variant with DPPX antibodies.","date":"2014","source":"Neurology","url":"https://pubmed.ncbi.nlm.nih.gov/24696508","citation_count":138,"is_preprint":false},{"pmid":"19285295","id":"PMC_19285295","title":"Haplotype-sharing analysis implicates chromosome 7q36 harboring DPP6 in familial idiopathic ventricular fibrillation.","date":"2009","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/19285295","citation_count":128,"is_preprint":false},{"pmid":"26291285","id":"PMC_26291285","title":"Anti-DPPX encephalitis: pathogenic effects of antibodies on gut and brain neurons.","date":"2015","source":"Neurology","url":"https://pubmed.ncbi.nlm.nih.gov/26291285","citation_count":95,"is_preprint":false},{"pmid":"21943606","id":"PMC_21943606","title":"DPP6 establishes the A-type K(+) current gradient critical for the regulation of dendritic excitability in CA1 hippocampal neurons.","date":"2011","source":"Neuron","url":"https://pubmed.ncbi.nlm.nih.gov/21943606","citation_count":91,"is_preprint":false},{"pmid":"15476821","id":"PMC_15476821","title":"Structure of a human A-type potassium channel interacting protein DPPX, a member of the dipeptidyl aminopeptidase family.","date":"2004","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/15476821","citation_count":81,"is_preprint":false},{"pmid":"18667548","id":"PMC_18667548","title":"Kv4 accessory protein DPPX (DPP6) is a critical regulator of membrane excitability in hippocampal CA1 pyramidal neurons.","date":"2008","source":"Journal of neurophysiology","url":"https://pubmed.ncbi.nlm.nih.gov/18667548","citation_count":62,"is_preprint":false},{"pmid":"10329480","id":"PMC_10329480","title":"The DPL1 gene is involved in mediating the response to nutrient deprivation in Saccharomyces cerevisiae.","date":"1999","source":"Molecular cell biology research communications : MCBRC","url":"https://pubmed.ncbi.nlm.nih.gov/10329480","citation_count":58,"is_preprint":false},{"pmid":"18978958","id":"PMC_18978958","title":"DPP6 Localization in Brain Supports Function as a Kv4 Channel Associated Protein.","date":"2008","source":"Frontiers in molecular neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/18978958","citation_count":57,"is_preprint":false},{"pmid":"11173531","id":"PMC_11173531","title":"Biosynthesis and characterization of the brain-specific membrane protein DPPX, a dipeptidyl peptidase IV-related protein.","date":"2001","source":"Journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11173531","citation_count":47,"is_preprint":false},{"pmid":"19279261","id":"PMC_19279261","title":"The dipeptidyl-peptidase-like protein DPP6 determines the unitary conductance of neuronal Kv4.2 channels.","date":"2009","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/19279261","citation_count":44,"is_preprint":false},{"pmid":"16764835","id":"PMC_16764835","title":"Differential characterization of three alternative spliced isoforms of DPPX.","date":"2006","source":"Brain research","url":"https://pubmed.ncbi.nlm.nih.gov/16764835","citation_count":43,"is_preprint":false},{"pmid":"26681609","id":"PMC_26681609","title":"Detailed characterization of familial idiopathic ventricular fibrillation linked to the DPP6 locus.","date":"2015","source":"Heart rhythm","url":"https://pubmed.ncbi.nlm.nih.gov/26681609","citation_count":43,"is_preprint":false},{"pmid":"30874922","id":"PMC_30874922","title":"Loss of DPP6 in neurodegenerative dementia: a genetic player in the dysfunction of neuronal excitability.","date":"2019","source":"Acta neuropathologica","url":"https://pubmed.ncbi.nlm.nih.gov/30874922","citation_count":41,"is_preprint":false},{"pmid":"29123178","id":"PMC_29123178","title":"A nanobody-based tracer targeting DPP6 for non-invasive imaging of human pancreatic endocrine cells.","date":"2017","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/29123178","citation_count":41,"is_preprint":false},{"pmid":"21512816","id":"PMC_21512816","title":"Founder mutations in the Netherlands: familial idiopathic ventricular fibrillation and DPP6.","date":"2011","source":"Netherlands heart journal : monthly journal of the Netherlands Society of Cardiology and the Netherlands Heart Foundation","url":"https://pubmed.ncbi.nlm.nih.gov/21512816","citation_count":39,"is_preprint":false},{"pmid":"27759917","id":"PMC_27759917","title":"Implication of LRRC4C and DPP6 in neurodevelopmental disorders.","date":"2016","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/27759917","citation_count":38,"is_preprint":false},{"pmid":"17237514","id":"PMC_17237514","title":"DPL-1 DP, LIN-35 Rb and EFL-1 E2F act with the MCD-1 zinc-finger protein to promote programmed cell death in Caenorhabditis elegans.","date":"2007","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/17237514","citation_count":37,"is_preprint":false},{"pmid":"23912628","id":"PMC_23912628","title":"DPP6 regulation of dendritic morphogenesis impacts hippocampal synaptic development.","date":"2013","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/23912628","citation_count":37,"is_preprint":false},{"pmid":"25190807","id":"PMC_25190807","title":"DPP6 domains responsible for its localization and function.","date":"2014","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/25190807","citation_count":34,"is_preprint":false},{"pmid":"18364354","id":"PMC_18364354","title":"I SA channel complexes include four subunits each of DPP6 and Kv4.2.","date":"2008","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/18364354","citation_count":32,"is_preprint":false},{"pmid":"21826085","id":"PMC_21826085","title":"DPP6 as a candidate gene for neuroleptic-induced tardive dyskinesia.","date":"2011","source":"The pharmacogenomics journal","url":"https://pubmed.ncbi.nlm.nih.gov/21826085","citation_count":31,"is_preprint":false},{"pmid":"23832105","id":"PMC_23832105","title":"Loss-of-function variation in the DPP6 gene is associated with autosomal dominant microcephaly and mental retardation.","date":"2013","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/23832105","citation_count":31,"is_preprint":false},{"pmid":"19525032","id":"PMC_19525032","title":"No association of DPP6 with amyotrophic lateral sclerosis in an Italian population.","date":"2009","source":"Neurobiology of aging","url":"https://pubmed.ncbi.nlm.nih.gov/19525032","citation_count":26,"is_preprint":false},{"pmid":"19441798","id":"PMC_19441798","title":"Convergent modulation of Kv4.2 channel alpha subunits by structurally distinct DPPX and KChIP auxiliary subunits.","date":"2009","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/19441798","citation_count":24,"is_preprint":false},{"pmid":"18536731","id":"PMC_18536731","title":"Effects of MiRP1 and DPP6 beta-subunits on the blockade induced by flecainide of Kv4.3/KChIP2 channels.","date":"2008","source":"British journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/18536731","citation_count":23,"is_preprint":false},{"pmid":"25129042","id":"PMC_25129042","title":"DPP6 gene disruption in a family with Gilles de la Tourette syndrome.","date":"2014","source":"Neurogenetics","url":"https://pubmed.ncbi.nlm.nih.gov/25129042","citation_count":22,"is_preprint":false},{"pmid":"35382765","id":"PMC_35382765","title":"Clinical and imaging analysis to evaluate the response of patients with anti-DPPX encephalitis to immunotherapy.","date":"2022","source":"BMC neurology","url":"https://pubmed.ncbi.nlm.nih.gov/35382765","citation_count":19,"is_preprint":false},{"pmid":"20137488","id":"PMC_20137488","title":"Association between DPP6 polymorphism and the risk of sporadic amyotrophic lateral sclerosis in Chinese patients.","date":"2009","source":"Chinese medical journal","url":"https://pubmed.ncbi.nlm.nih.gov/20137488","citation_count":19,"is_preprint":false},{"pmid":"19007856","id":"PMC_19007856","title":"A novel DPP6 isoform (DPP6-E) can account for differences between neuronal and reconstituted A-type K(+) channels.","date":"2008","source":"Neuroscience letters","url":"https://pubmed.ncbi.nlm.nih.gov/19007856","citation_count":17,"is_preprint":false},{"pmid":"23409053","id":"PMC_23409053","title":"Epigenetic regulation of Dpp6 expression by Dnmt3b and its novel role in the inhibition of RA induced neuronal differentiation of P19 cells.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23409053","citation_count":16,"is_preprint":false},{"pmid":"23069673","id":"PMC_23069673","title":"Association between DPP6 polymorphism and the risk of progressive multiple sclerosis in Northern and Southern Europeans.","date":"2012","source":"Neuroscience letters","url":"https://pubmed.ncbi.nlm.nih.gov/23069673","citation_count":16,"is_preprint":false},{"pmid":"24937803","id":"PMC_24937803","title":"Mapping breakpoints of a familial chromosome insertion (18,7) (q22.1; q36.2q21.11) to DPP6 and CACNA2D1 genes in an azoospermic male.","date":"2014","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/24937803","citation_count":16,"is_preprint":false},{"pmid":"33143549","id":"PMC_33143549","title":"Neuronal Differentiation of Induced Pluripotent Stem Cells from Schizophrenia Patients in Two-Dimensional and in Three-Dimensional Cultures Reveals Increased Expression of the Kv4.2 Subunit DPP6 That Contributes to Decreased Neuronal Activity.","date":"2020","source":"Stem cells and development","url":"https://pubmed.ncbi.nlm.nih.gov/33143549","citation_count":15,"is_preprint":false},{"pmid":"36209950","id":"PMC_36209950","title":"Alzheimer's disease/dementia-associated brain pathology in aging DPP6-KO mice.","date":"2022","source":"Neurobiology of disease","url":"https://pubmed.ncbi.nlm.nih.gov/36209950","citation_count":14,"is_preprint":false},{"pmid":"36012450","id":"PMC_36012450","title":"Neuronal Roles of the Multifunctional Protein Dipeptidyl Peptidase-like 6 (DPP6).","date":"2022","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/36012450","citation_count":13,"is_preprint":false},{"pmid":"19368797","id":"PMC_19368797","title":"DPL-1 (DP) acts in the germ line to coordinate ovulation and fertilization in C. elegans.","date":"2009","source":"Mechanisms of development","url":"https://pubmed.ncbi.nlm.nih.gov/19368797","citation_count":13,"is_preprint":false},{"pmid":"19153714","id":"PMC_19153714","title":"The transmembrane beta-subunits KCNE1, KCNE2, and DPP6 modify pharmacological effects of the antiarrhythmic agent tedisamil on the transient outward current Ito.","date":"2009","source":"Naunyn-Schmiedeberg's archives of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/19153714","citation_count":12,"is_preprint":false},{"pmid":"18304523","id":"PMC_18304523","title":"The candidate MAP kinase phosphorylation substrate DPL-1 (DP) promotes expression of the MAP kinase phosphatase LIP-1 in C. elegans germ cells.","date":"2008","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/18304523","citation_count":10,"is_preprint":false},{"pmid":"37024733","id":"PMC_37024733","title":"Sleep disturbances associated with DPPX autoantibodies: a case series.","date":"2023","source":"Journal of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/37024733","citation_count":9,"is_preprint":false},{"pmid":"37806046","id":"PMC_37806046","title":"Long term outcomes in patients with anti-DPPX autoimmunity.","date":"2023","source":"Journal of neuroimmunology","url":"https://pubmed.ncbi.nlm.nih.gov/37806046","citation_count":9,"is_preprint":false},{"pmid":"33225987","id":"PMC_33225987","title":"A novel structure associated with aging is augmented in the DPP6-KO mouse brain.","date":"2020","source":"Acta neuropathologica communications","url":"https://pubmed.ncbi.nlm.nih.gov/33225987","citation_count":8,"is_preprint":false},{"pmid":"33458536","id":"PMC_33458536","title":"Ratiometric Fluorescence Detection of DNA Based on the Inner Filter Effect of Ru(bpy)2(dppx)2+ toward Silicon Nanodots.","date":"2020","source":"ACS omega","url":"https://pubmed.ncbi.nlm.nih.gov/33458536","citation_count":8,"is_preprint":false},{"pmid":"29378180","id":"PMC_29378180","title":"Regulation of Kv4.3 and hERG potassium channels by KChIP2 isoforms and DPP6 and response to the dual K+ channel activator NS3623.","date":"2018","source":"Biochemical pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/29378180","citation_count":8,"is_preprint":false},{"pmid":"18411327","id":"PMC_18411327","title":"A role for DPPX modulating external TEA sensitivity of Kv4 channels.","date":"2008","source":"The Journal of general physiology","url":"https://pubmed.ncbi.nlm.nih.gov/18411327","citation_count":6,"is_preprint":false},{"pmid":"10384734","id":"PMC_10384734","title":"Spectral studies on the interaction of DNA and Ru(bipy)2(dppx)2+.","date":"1999","source":"Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy","url":"https://pubmed.ncbi.nlm.nih.gov/10384734","citation_count":6,"is_preprint":false},{"pmid":"20817268","id":"PMC_20817268","title":"Expression of Dpp6 in mouse embryonic craniofacial development.","date":"2010","source":"Acta histochemica","url":"https://pubmed.ncbi.nlm.nih.gov/20817268","citation_count":6,"is_preprint":false},{"pmid":"36588910","id":"PMC_36588910","title":"Case report: Pain in anti-DPPX encephalitis.","date":"2022","source":"Frontiers in neurology","url":"https://pubmed.ncbi.nlm.nih.gov/36588910","citation_count":5,"is_preprint":false},{"pmid":"38449607","id":"PMC_38449607","title":"DPPX antibody-mediated autoimmune encephalitis：the first case with breast cancer and review of the literature.","date":"2024","source":"Heliyon","url":"https://pubmed.ncbi.nlm.nih.gov/38449607","citation_count":5,"is_preprint":false},{"pmid":"38875006","id":"PMC_38875006","title":"GWAS Identifies DPP6 as Risk Gene of Cognitive Decline in Parkinson's Disease.","date":"2024","source":"The journals of gerontology. Series A, Biological sciences and medical sciences","url":"https://pubmed.ncbi.nlm.nih.gov/38875006","citation_count":4,"is_preprint":false},{"pmid":"39007139","id":"PMC_39007139","title":"Case report: Ofatumumab treatment in anti-DPPX autoimmune encephalitis.","date":"2024","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/39007139","citation_count":4,"is_preprint":false},{"pmid":"38756408","id":"PMC_38756408","title":"Expanding the clinical spectrum of anti-DPPX encephalitis: a multicenter retrospective study.","date":"2024","source":"Frontiers in neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/38756408","citation_count":4,"is_preprint":false},{"pmid":"31476289","id":"PMC_31476289","title":"A novel DPP6 variant in Chinese families causes early repolarization syndrome.","date":"2019","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/31476289","citation_count":3,"is_preprint":false},{"pmid":"23750656","id":"PMC_23750656","title":"Expression of DPP6 in Meckel's cartilage and tooth germs during mouse facial development.","date":"2013","source":"Biotechnic & histochemistry : official publication of the Biological Stain Commission","url":"https://pubmed.ncbi.nlm.nih.gov/23750656","citation_count":3,"is_preprint":false},{"pmid":"38469308","id":"PMC_38469308","title":"Case report: Successful treatment of an anti-D2R and DPPX antibody-associated autoimmune encephalitis patient with high-dose methylprednisolone and intravenous immunoglobulin.","date":"2024","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/38469308","citation_count":3,"is_preprint":false},{"pmid":"38274926","id":"PMC_38274926","title":"A Devastating Neurological Disorder: Anti-Dipeptidyl-Peptidase-Like Protein 6 (DPPX) Encephalitis Causing Rapidly Progressive Dementia.","date":"2023","source":"Cureus","url":"https://pubmed.ncbi.nlm.nih.gov/38274926","citation_count":3,"is_preprint":false},{"pmid":"37917556","id":"PMC_37917556","title":"Polymorphism of ADAM12, DPP6 and PRKN genes and their associations with milk production traits in Holstein.","date":"2023","source":"Reproduction in domestic animals = Zuchthygiene","url":"https://pubmed.ncbi.nlm.nih.gov/37917556","citation_count":2,"is_preprint":false},{"pmid":"36012438","id":"PMC_36012438","title":"Modulation of KV4.3-KChIP2 Channels by IQM-266: Role of DPP6 and KCNE2.","date":"2022","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/36012438","citation_count":2,"is_preprint":false},{"pmid":"38243162","id":"PMC_38243162","title":"A rare case of anti-DPPX encephalitis combined with neuroleptospirosis.","date":"2024","source":"BMC neurology","url":"https://pubmed.ncbi.nlm.nih.gov/38243162","citation_count":2,"is_preprint":false},{"pmid":"37452869","id":"PMC_37452869","title":"Binding and stabilizating effect of RNA triplex poly(U)⋅poly(A)*poly(U) by enantiomers of ruthenium(II) polypyridyl complex [Ru(bpy)2(dppx)]2.","date":"2023","source":"Journal of biological inorganic chemistry : JBIC : a publication of the Society of Biological Inorganic Chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/37452869","citation_count":1,"is_preprint":false},{"pmid":"34639784","id":"PMC_34639784","title":"The Mediation Effects of Aluminum in Plasma and Dipeptidyl Peptidase Like Protein 6 (DPP6) Polymorphism on Renal Function via Genome-Wide Typing Association.","date":"2021","source":"International journal of environmental research and public health","url":"https://pubmed.ncbi.nlm.nih.gov/34639784","citation_count":1,"is_preprint":false},{"pmid":"38272106","id":"PMC_38272106","title":"Correction of Ito in human induced pluripotent stem Cell-derived cardiomyocyte carrying DPP6 mutation in early repolarization syndrome by CRISPR/Cas9 genome editing.","date":"2024","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/38272106","citation_count":1,"is_preprint":false},{"pmid":"38252428","id":"PMC_38252428","title":"Diffusely Enhancing Lesions on MRI in DPPX Antibody-Associated Encephalitis.","date":"2024","source":"JAMA neurology","url":"https://pubmed.ncbi.nlm.nih.gov/38252428","citation_count":1,"is_preprint":false},{"pmid":"40109277","id":"PMC_40109277","title":"The role of DPP6 dysregulation in neuropathology: from synaptic regulation to disease mechanisms.","date":"2025","source":"Frontiers in cellular neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/40109277","citation_count":0,"is_preprint":false},{"pmid":"38381392","id":"PMC_38381392","title":"Association between DPP6 gene rs10260404 polymorphism and increased risk of sporadic amyotrophic lateral sclerosis (sALS): a meta-analysis.","date":"2024","source":"Neurological sciences : official journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology","url":"https://pubmed.ncbi.nlm.nih.gov/38381392","citation_count":0,"is_preprint":false},{"pmid":"40241920","id":"PMC_40241920","title":"Anti-dipeptidyl-peptidase-like protein-6 (DPPX) autoimmune encephalitis associated with severe multifocal dystonia.","date":"2025","source":"Clinical parkinsonism & related disorders","url":"https://pubmed.ncbi.nlm.nih.gov/40241920","citation_count":0,"is_preprint":false},{"pmid":"40937361","id":"PMC_40937361","title":"Changes in DPPX autoantibody levels in autoimmune encephalitis: a case report and brief review.","date":"2025","source":"Brain disorders (Amsterdam, Netherlands)","url":"https://pubmed.ncbi.nlm.nih.gov/40937361","citation_count":0,"is_preprint":false},{"pmid":"41977406","id":"PMC_41977406","title":"DPP6 Loss Causes Age-Dependent Sleep Dysregulation and Depression-like Phenotypes Linked to Neurodegeneration.","date":"2026","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/41977406","citation_count":0,"is_preprint":false},{"pmid":"41935344","id":"PMC_41935344","title":"Dpp6 knockout mice exhibit increased ethanol conditioned place preference and acute ethanol-induced anxiolytic behavior.","date":"2026","source":"Alcohol, clinical & experimental research","url":"https://pubmed.ncbi.nlm.nih.gov/41935344","citation_count":0,"is_preprint":false},{"pmid":"40894538","id":"PMC_40894538","title":"Dpp6 Homozygous Knockout Mice Exhibit Increased Ethanol Conditioned Place Preference and Acute Ethanol-Induced Anxiolytic Behavior.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/40894538","citation_count":0,"is_preprint":false},{"pmid":"40808961","id":"PMC_40808961","title":"Case Report: Treatment of delayed tremor episodes in a patient with DPPX antibody encephalitis.","date":"2025","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/40808961","citation_count":0,"is_preprint":false},{"pmid":"39753277","id":"PMC_39753277","title":"DPPX antibody-mediated disease mimicking Wernicke's encephalopathy.","date":"2025","source":"BMJ case reports","url":"https://pubmed.ncbi.nlm.nih.gov/39753277","citation_count":0,"is_preprint":false},{"pmid":"19536467","id":"PMC_19536467","title":"DPPX modifies TEA sensitivity of the Kv4 channels in rabbit carotid body chemoreceptor cells.","date":"2009","source":"Advances in experimental medicine and biology","url":"https://pubmed.ncbi.nlm.nih.gov/19536467","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":39297,"output_tokens":5102,"usd":0.097211},"stage2":{"model":"claude-opus-4-6","input_tokens":8615,"output_tokens":3816,"usd":0.207712},"total_usd":0.304923,"stage1_batch_id":"msgbatch_0118RScg3WGaGkaZRtWZbtce","stage2_batch_id":"msgbatch_01Cpfzvtbj42aqp5oYZ5Te2s","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2003,\n      \"finding\": \"DPPX (DPP6) was purified as a novel component of neuronal A-type K+ channel complexes from rat brain membranes. It associates with Kv4 pore-forming subunits, facilitates their trafficking and membrane targeting, and reconstitutes native A-type K+ channel properties in heterologous expression systems. It co-localizes with Kv4 subunits in the somatodendritic compartment of CNS neurons.\",\n      \"method\": \"Biochemical purification of K+ channel complexes from rat brain membranes, co-immunoprecipitation, heterologous expression reconstitution, immunolocalization\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — original discovery with multiple orthogonal methods (purification, Co-IP, reconstitution, localization), highly cited foundational paper\",\n      \"pmids\": [\"12575952\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"X-ray crystal structure of the extracellular domain of human DPPX at 3.0 Å resolution revealed a dimeric structure homologous to DPP-IV. The active-site serine is absent and the residue arrangement is inconsistent with canonical serine proteases, establishing that DPPX lacks dipeptidyl aminopeptidase catalytic activity. The structure suggests surface electrostatic changes based on histidine protonation state that could modulate Kv4.2 interaction.\",\n      \"method\": \"X-ray crystallography, active-site structural analysis\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with functional validation of lack of protease activity\",\n      \"pmids\": [\"15476821\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"DPPX-S and DPPX-L are brain-specific glycoproteins that are synthesized with high-mannose oligosaccharides and processed to complex-type sugar chains before reaching the cell surface. Despite structural homology to DPP-IV, mutagenesis to introduce the canonical Gly-X-Ser-X-Gly active-site motif failed to confer dipeptidyl aminopeptidase activity, confirming catalytic incompetence.\",\n      \"method\": \"Cell-free translation, COS-1 cell transfection, immunofluorescence, enzymatic activity assay, site-directed mutagenesis, immunoblot\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis plus activity assay, multiple methods confirming lack of enzymatic activity\",\n      \"pmids\": [\"11173531\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Three alternatively spliced DPPX isoforms (DPPX-S, DPPX-L, DPPX-K) all modify the voltage dependence and kinetic properties of Kv4.2 channels expressed in Xenopus oocytes. Deletion of the variable N-terminus showed the N-terminus is not required for Kv4 channel modulation, placing the functional domain in the transmembrane or extracellular region.\",\n      \"method\": \"Xenopus oocyte expression, electrophysiology, deletion mutagenesis, in situ hybridization\",\n      \"journal\": \"Brain research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with mutagenesis in multiple isoforms\",\n      \"pmids\": [\"16764835\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"ISA channel complexes contain four subunits each of Kv4.2 and DPP6 (4:4 stoichiometry), established by both biophysical methods using tandem-linked subunits and direct biochemical amino acid analysis of purified complexes.\",\n      \"method\": \"Tandem-linked subunit constructs (functional), amino acid analysis of purified channel complexes (biochemical)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution plus biochemical quantification, two orthogonal methods in one study\",\n      \"pmids\": [\"18364354\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"DPP6 (DPPX) localization in brain closely mirrors that of Kv4.2, with both enriched in dendrites of neurons that co-express them. Additionally, DPP6 was found in hippocampal mossy fiber axons that lack Kv4 proteins, suggesting a Kv4-independent function in axons.\",\n      \"method\": \"Immunohistochemistry with DPP6 and Kv4.2 antibodies, subcellular fractionation, immunofluorescence\",\n      \"journal\": \"Frontiers in molecular neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization experiment with functional implication, single lab\",\n      \"pmids\": [\"18978958\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"siRNA knockdown of DPPX in hippocampal CA1 pyramidal neurons caused depolarizing shifts in steady-state inactivation and activation curves, slowed inactivation, and delayed recovery from inactivation of A-type currents. This resulted in decreased subthreshold excitability (reduced input resistance, delayed AP onset, increased AP threshold) and slowed AP rise and repolarization suprathreshold.\",\n      \"method\": \"siRNA knockdown in neurons, voltage-clamp and current-clamp electrophysiology, computer simulations\",\n      \"journal\": \"Journal of neurophysiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KD with defined biophysical and physiological phenotypic readouts, supported by computational modeling\",\n      \"pmids\": [\"18667548\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"DPP6-S is necessary and sufficient to increase the unitary conductance (gamma) of Kv4.2 channels from ~4 pS to ~7.5 pS (matching native cerebellar granule neuron channels). Charge neutralization of two N-terminal acidic residues in DPP6-S eliminated this conductance increase, implicating electrostatic interactions. DPP6 knockout mouse CGN channels had conductance indistinguishable from Kv4.2 expressed alone.\",\n      \"method\": \"Single-channel patch clamp in heterologous cells and DPP6-KO mouse neurons, site-directed mutagenesis\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution, KO confirmation, mutagenesis identifying specific residues, multiple orthogonal approaches\",\n      \"pmids\": [\"19279261\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Co-expression of DPPX-S with Kv4.2 dramatically redistributes Kv4.2 from intracellular retention to plasma membrane expression, alters Kv4.2 phosphorylation pattern (to resemble that in brain), changes detergent solubility and stability. These effects are similar to those of KChIP auxiliary subunits. KChIP4a, which inhibits other KChIPs, also inhibits DPPX-S effects, consistent with formation of a ternary Kv4.2/DPPX-S/KChIP complex early in biosynthesis.\",\n      \"method\": \"Co-expression in heterologous cells, immunofluorescence, tandem MS phosphorylation analysis, detergent solubility assay\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (imaging, MS, biochemical), reveals mechanism of convergent auxiliary subunit action\",\n      \"pmids\": [\"19441798\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"DPP6 knockout mice lacking the Kv4 transmembrane auxiliary subunit DPP6 show a specific loss of A-type K+ current in distal dendrites of CA1 hippocampal pyramidal neurons, accompanied by a depolarizing shift in activation voltage dependence. This results in hyperexcitable dendrites with enhanced dendritic AP back-propagation, calcium electrogenesis, and enhanced LTP induction, without major effects on somatic firing.\",\n      \"method\": \"Dendritic patch-clamp recordings from DPP6-KO mice, calcium imaging, LTP induction\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with multiple compartment-specific electrophysiological and imaging readouts\",\n      \"pmids\": [\"21943606\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"DPP6 knockdown or genetic deletion reduces dendritic filopodia formation and stability during early hippocampal neuronal development, leading to sparser dendritic branching, fewer spines, and fewer functional synapses in adult neurons. This role in dendritic morphogenesis is independent of Kv4.2. DPP6 was found to interact with a filopodia-associated myosin and with fibronectin in the extracellular matrix.\",\n      \"method\": \"shRNA knockdown, DPP6-KO mice, live imaging, electrophysiology, co-immunoprecipitation with myosin and fibronectin\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KD and KO with multiple readouts plus binding partners identified; Kv4.2-independence established by epistasis\",\n      \"pmids\": [\"23912628\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The cysteine-rich domain of DPP6 extracellular region is required for ER export and cell surface expression. Disulfide bridges at C349/C356 and C465/C468 are necessary for enhancement of Kv4.2 surface expression but not for physical interaction with Kv4.2. The short intracellular N-terminal and transmembrane domains of DPP6 associate with Kv4.2 and accelerate recovery from inactivation, while the entire extracellular domain is required for Kv4.2 surface expression enhancement and stabilization.\",\n      \"method\": \"Domain deletion/mutagenesis, disulfide bridge mutagenesis, co-immunoprecipitation, surface biotinylation, electrophysiology\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic mutagenesis with functional validation separating binding from trafficking roles\",\n      \"pmids\": [\"25190807\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"A novel DPP6 splice isoform, DPP6-E, produces ternary Kv4 channels with very fast inactivation kinetics when expressed with Kv4.2 and KChIP1. DPP6-E is selectively expressed in cerebellar granule neurons, hippocampal pyramidal cells, and superior colliculus neurons, accounting for past discrepancies between reconstituted and native Kv4 channel kinetics in these cells.\",\n      \"method\": \"Heterologous expression, electrophysiology, in situ hybridization\",\n      \"journal\": \"Neuroscience letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional reconstitution matched to native cell expression pattern\",\n      \"pmids\": [\"19007856\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"DPPX association with Kv4 channels in rabbit carotid body chemoreceptor cells confers TEA sensitivity (increased block by external TEA) to natively TEA-insensitive Kv4 channels. siRNA knockdown of DPPX reduced K(O2) currents and altered TEA sensitivity, establishing DPPX as an integral component of oxygen-sensitive K+ currents in these cells.\",\n      \"method\": \"siRNA knockdown in native cells, pharmacological TEA block, heterologous co-expression electrophysiology\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — siRNA in native cells plus heterologous reconstitution, single lab\",\n      \"pmids\": [\"18411327\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Patient DPPX antibodies (predominantly IgG1 and IgG4) caused a reversible decrease of DPPX clusters and Kv4.2 protein at the surface of cultured neurons when applied, with recovery upon antibody removal. In hippocampal neurons, anti-DPPX-IgG decreased membrane expression of both DPPX and Kv4.2, and increased enteric nervous system neuron excitability.\",\n      \"method\": \"Immunocytochemistry on cultured neurons, immunoblot of neuronal membrane fractions, voltage-sensitive dye imaging of enteric neurons\",\n      \"journal\": \"Neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct antibody application experiments with quantified protein level and functional readouts\",\n      \"pmids\": [\"28258082\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Dnmt3b epigenetically silences Dpp6 expression through promoter DNA methylation. Depletion of Dnmt3b increases Dpp6 mRNA and protein. Ectopic DPP6 overexpression in P19 cells inhibits retinoic acid-induced neuronal differentiation, indicating DPP6 functions as a negative regulator of this differentiation process.\",\n      \"method\": \"ChIP, bisulfite sequencing, COBRA, methylation-specific PCR, Dnmt3b knockdown, DPP6 overexpression differentiation assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple epigenetic methods plus functional overexpression phenotype, single lab\",\n      \"pmids\": [\"23409053\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"A missense variant DPP6-L747P identified in families with early repolarization syndrome causes gain-of-function of transient outward K+ current (Ito) when co-expressed with Kv4.3 and KChIP2 in HEK293 cells: increased macroscopic current density, altered activation and inactivation slopes, and reduced recovery time constant.\",\n      \"method\": \"Whole-cell patch clamp, western blot, immunofluorescence in HEK293 cells\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional electrophysiology with mutant vs WT comparison, single lab\",\n      \"pmids\": [\"31476289\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Increased DPP6 expression in iPSC-derived cortical neurons from schizophrenia patients causes neuronal hypoexcitability. Lentiviral shRNA knockdown of DPP6 or pharmacological block of Kv4.2 with AmmTx3 both reversed the hypoexcitability, establishing a causal link between elevated DPP6/Kv4.2 activity and decreased neuronal firing in this model.\",\n      \"method\": \"iPSC differentiation, RNA sequencing, multielectrode array recordings, calcium imaging, lentiviral shRNA, pharmacological block\",\n      \"journal\": \"Stem cells and development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — causal rescue experiments with shRNA and pharmacology, multiple readouts\",\n      \"pmids\": [\"33143549\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Missense variants in DPP6 found in early-onset Alzheimer's disease and frontotemporal dementia patients destabilize DPP6 protein and reduce its membrane expression in vitro, and reduced DPP6 and Kv4.2 expression was confirmed in brain tissue of missense variant carriers.\",\n      \"method\": \"In vitro expression assay of patient variants, western blot, immunofluorescence, brain tissue immunoblot\",\n      \"journal\": \"Acta neuropathologica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — in vitro functional assay plus human brain tissue confirmation, single lab\",\n      \"pmids\": [\"30874922\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Patient anti-DPPX IgG applied to hippocampal neurons decreased membrane expression of both DPPX and Kv4.2, as measured by immunoblot of purified neuronal membranes. Application to enteric nervous system preparations increased neuronal action potential frequency, demonstrating direct pathogenic antibody effects on both brain and gut neurons.\",\n      \"method\": \"Purified patient IgG application, immunoblot of neuronal membranes, voltage-sensitive dye imaging of enteric neurons\",\n      \"journal\": \"Neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — purified antibody experiments with quantified membrane protein and functional electrophysiological readouts\",\n      \"pmids\": [\"26291285\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"DPP6 overexpression in the myocardium of familial idiopathic ventricular fibrillation risk-haplotype carriers shows ~20-fold increased DPP6 mRNA compared to controls, implicating increased DPP6 expression as the pathogenetic mechanism in this cardiac arrhythmia syndrome. DPP6 was proposed as a component of the transient outward current in the heart.\",\n      \"method\": \"Haplotype-sharing genome-wide analysis, qRT-PCR of myocardial DPP6 mRNA\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — expression quantification without direct functional electrophysiological validation in cardiac tissue\",\n      \"pmids\": [\"19285295\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"DPP6 is a single-pass transmembrane auxiliary subunit of neuronal Kv4-family A-type K+ channels: it physically associates with Kv4 pore-forming subunits in a 4:4 stoichiometry, promotes their trafficking out of the ER and to the plasma membrane via disulfide-bonded extracellular cysteine-rich domains, shifts channel voltage dependence, accelerates inactivation and recovery kinetics through its intracellular/transmembrane domains, and increases unitary conductance via electrostatic interactions of N-terminal acidic residues; beyond its role as a Kv4 auxiliary subunit, DPP6 independently regulates dendritic filopodia formation and synaptic development through interactions with myosin and extracellular fibronectin, and loss of DPP6 in mice produces dendritic hyperexcitability, synaptic loss, and progressive Alzheimer's-like neurodegeneration.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"DPP6 is a catalytically inactive single-pass transmembrane auxiliary subunit of neuronal Kv4-family voltage-gated potassium channels that shapes A-type K+ current properties and regulates dendritic development. DPP6 assembles with Kv4 pore-forming subunits in a 4:4 stoichiometry, promotes their ER export and plasma membrane trafficking via disulfide-bonded cysteine-rich extracellular domains, shifts channel voltage dependence, accelerates inactivation and recovery kinetics through its transmembrane/intracellular domains, and increases unitary conductance through electrostatic interactions of N-terminal acidic residues [PMID:12575952, PMID:18364354, PMID:25190807, PMID:19279261]. Loss of DPP6 in knockout mice produces dendritic hyperexcitability with enhanced back-propagating action potentials and augmented LTP in hippocampal CA1 neurons [PMID:21943606], and independently of Kv4.2, DPP6 promotes dendritic filopodia formation and synaptogenesis through interactions with myosin and fibronectin [PMID:23912628]. Missense variants in DPP6 that destabilize the protein and reduce its membrane expression have been identified in early-onset Alzheimer's disease and frontotemporal dementia patients, while a gain-of-function variant (L747P) causes early repolarization syndrome through enhanced transient outward K+ current [PMID:30874922, PMID:31476289].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Establishing that DPP6, despite structural homology to DPP-IV, is catalytically inactive resolved a key question about whether this protein functions as a peptidase or has a non-enzymatic role.\",\n      \"evidence\": \"Mutagenesis introducing the canonical active-site motif failed to confer dipeptidyl aminopeptidase activity in COS-1 cells\",\n      \"pmids\": [\"11173531\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Biological function remained unknown at this point\", \"Mechanism of glycosylation processing and its functional significance not explored\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identifying DPP6 as a native component of neuronal Kv4 A-type K+ channel complexes established its primary physiological role and explained how native ISA channel properties differ from reconstituted Kv4 alone.\",\n      \"evidence\": \"Biochemical purification from rat brain, co-immunoprecipitation with Kv4, heterologous reconstitution of native-like A-type currents, and somatodendritic co-localization\",\n      \"pmids\": [\"12575952\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of the complex unknown\", \"Which DPP6 domains mediate Kv4 interaction and modulation unresolved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"The crystal structure of the DPP6 extracellular domain confirmed the structural basis for its catalytic incompetence and suggested pH-dependent electrostatic modulation of Kv4 interaction.\",\n      \"evidence\": \"X-ray crystallography at 3.0 Å resolution of human DPPX extracellular domain\",\n      \"pmids\": [\"15476821\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structure of the DPP6–Kv4 complex to reveal interaction interface\", \"Histidine protonation-dependent modulation not functionally tested\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrating that all three splice isoforms modulate Kv4.2 and that the variable N-terminus is dispensable for channel modulation localized the core modulatory function to the transmembrane/extracellular region.\",\n      \"evidence\": \"Deletion mutagenesis and electrophysiology of DPPX-S, -L, -K isoforms in Xenopus oocytes\",\n      \"pmids\": [\"16764835\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific transmembrane or extracellular residues mediating gating modulation not identified\", \"Isoform-specific functional differences in native neurons unclear\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Determining the 4:4 stoichiometry of DPP6:Kv4.2 in ISA complexes defined the quaternary architecture and constrained models of auxiliary subunit–pore interaction.\",\n      \"evidence\": \"Tandem-linked subunit constructs and amino acid analysis of purified complexes\",\n      \"pmids\": [\"18364354\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Arrangement of DPP6 subunits around the Kv4 tetramer not resolved\", \"Whether KChIPs simultaneously associate in the same 4:4 complex not quantified\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Knockdown of DPP6 in native CA1 neurons demonstrated its necessity for normal A-type current gating and revealed compartment-specific effects on neuronal excitability, while DPP6 localization in Kv4-lacking mossy fiber axons suggested Kv4-independent roles.\",\n      \"evidence\": \"siRNA knockdown with dendritic and somatic patch-clamp in hippocampal neurons; immunohistochemistry showing DPP6 in mossy fibers\",\n      \"pmids\": [\"18667548\", \"18978958\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Nature of Kv4-independent function in axons unknown\", \"Whether DPP6 loss affects synaptic transmission not tested\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Discovery of the DPP6-E splice isoform explained discrepancies between reconstituted and native channel kinetics in cerebellar granule neurons and hippocampal pyramidal cells, establishing isoform-specific tuning of Kv4 gating.\",\n      \"evidence\": \"Heterologous expression electrophysiology with DPP6-E/Kv4.2/KChIP1, matched to in situ hybridization expression pattern\",\n      \"pmids\": [\"19007856\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis for DPP6-E's faster inactivation not determined\", \"Whether DPP6-E and other isoforms co-assemble in native complexes unknown\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identifying that DPP6-S increases Kv4.2 unitary conductance via two N-terminal acidic residues revealed a distinct electrostatic mechanism of channel modulation separate from gating effects.\",\n      \"evidence\": \"Single-channel recording in heterologous cells and DPP6-KO mouse cerebellar granule neurons, charge-neutralization mutagenesis\",\n      \"pmids\": [\"19279261\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How intracellular acidic residues influence the extracellular conduction pathway not structurally explained\", \"Whether other isoforms share this conductance effect untested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Demonstrating that DPP6 promotes Kv4.2 ER-to-surface trafficking, alters its phosphorylation to brain-like patterns, and converges with KChIP action revealed the biosynthetic mechanism underlying auxiliary subunit regulation of channel density.\",\n      \"evidence\": \"Co-expression in heterologous cells with immunofluorescence, tandem MS phosphorylation, detergent solubility, and KChIP4a epistasis\",\n      \"pmids\": [\"19441798\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of kinases/phosphatases responsible for DPP6-dependent Kv4.2 phosphorylation changes unknown\", \"Whether ternary complex forms co-translationally or post-translationally unresolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"DPP6 knockout mice revealed that DPP6 is the dominant determinant of distal dendritic A-type current, and its loss causes dendritic hyperexcitability and enhanced LTP without affecting somatic firing, establishing compartment-specific physiology.\",\n      \"evidence\": \"Dendritic and somatic patch-clamp recordings, calcium imaging, and LTP induction protocols in DPP6-KO mice\",\n      \"pmids\": [\"21943606\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether behavioral or cognitive phenotypes accompany dendritic hyperexcitability not assessed\", \"Compensatory changes in other auxiliary subunits not examined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Demonstrating that DPP6 promotes dendritic filopodia formation and synaptogenesis independently of Kv4.2, via interactions with myosin and fibronectin, established a second, non-channel function in neural development.\",\n      \"evidence\": \"shRNA knockdown and DPP6-KO mice with live imaging, electrophysiology, co-immunoprecipitation with myosin and fibronectin\",\n      \"pmids\": [\"23912628\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which myosin isoform mediates the interaction not specified\", \"How DPP6–fibronectin interaction signals to the cytoskeleton mechanistically unclear\", \"Whether this developmental role extends to non-hippocampal brain regions untested\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Systematic domain dissection separated DPP6's binding, gating, and trafficking functions: the transmembrane/N-terminal domains bind Kv4.2 and accelerate recovery, while the extracellular cysteine-rich domain with specific disulfide bonds drives ER export and surface expression.\",\n      \"evidence\": \"Domain deletions, cysteine mutagenesis, co-immunoprecipitation, surface biotinylation, electrophysiology\",\n      \"pmids\": [\"25190807\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic-resolution structure of DPP6–Kv4 interface still lacking\", \"Whether additional extracellular domain functions exist beyond trafficking unresolved\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Pathogenic anti-DPPX autoantibodies from patients directly reduce surface DPP6 and Kv4.2, increasing neuronal excitability in both brain and enteric neurons, establishing a molecular mechanism for autoimmune DPPX encephalitis.\",\n      \"evidence\": \"Purified patient IgG applied to hippocampal neurons and enteric nervous system preparations with membrane immunoblot and voltage-sensitive dye recording\",\n      \"pmids\": [\"26291285\", \"28258082\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether antibody-mediated internalization or cross-linking is the primary mechanism of surface loss unclear\", \"Long-term in vivo pathogenic effects not modeled\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"DPP6 missense variants identified in early-onset Alzheimer's disease and frontotemporal dementia patients destabilize the protein and reduce membrane expression, linking DPP6 loss-of-function to neurodegeneration, while a gain-of-function variant (L747P) in early repolarization syndrome enhances Ito current, linking DPP6 to cardiac arrhythmia.\",\n      \"evidence\": \"In vitro expression assays of patient variants, brain tissue immunoblot; whole-cell patch clamp of L747P with Kv4.3/KChIP2 in HEK293 cells\",\n      \"pmids\": [\"30874922\", \"31476289\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal role of DPP6 variants in neurodegeneration not proven by rescue or animal models\", \"Mechanism by which L747P enhances current (trafficking vs gating) not distinguished\", \"Whether cardiac DPP6 functions with Kv4.3 in native cardiomyocytes not directly shown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Elevated DPP6 expression in schizophrenia patient iPSC-derived neurons causally drives hypoexcitability, reversible by DPP6 knockdown or Kv4 block, linking DPP6 dosage to disease-relevant excitability changes.\",\n      \"evidence\": \"iPSC cortical neurons, RNA-seq, MEA recordings, calcium imaging, lentiviral shRNA rescue, AmmTx3 pharmacology\",\n      \"pmids\": [\"33143549\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether DPP6 upregulation is a primary genetic effect or secondary in schizophrenia not resolved\", \"Circuit-level consequences of neuronal hypoexcitability not modeled\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"No high-resolution structure of the DPP6–Kv4 complex exists, the molecular basis of how the transmembrane domain accelerates gating transitions remains unresolved, and the signaling pathway linking DPP6's extracellular fibronectin interaction to cytoskeletal remodeling during synaptogenesis is unknown.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cryo-EM or crystal structure of the full DPP6–Kv4–KChIP ternary complex needed\", \"Mechanism of DPP6-mediated filopodia signaling uncharacterized\", \"In vivo validation of DPP6 variants as causative for neurodegeneration lacking\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 3, 6, 7, 9, 11]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [4, 8, 11]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 5, 8, 11, 14]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [8, 11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 6, 7, 9, 10]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 8, 11]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [10, 15]}\n    ],\n    \"complexes\": [\n      \"Kv4.2/DPP6/KChIP ternary channel complex\"\n    ],\n    \"partners\": [\n      \"KCND2\",\n      \"KCND3\",\n      \"KCNIP1\",\n      \"KCNIP2\",\n      \"KCNIP4\",\n      \"FN1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}