{"gene":"CACNA2D2","run_date":"2026-04-28T17:28:52","timeline":{"discoveries":[{"year":2000,"finding":"CACNA2D2 encodes the α2δ-2 auxiliary subunit of voltage-gated Ca2+ channels; when co-expressed with α1B/β3 in Xenopus oocytes, α2δ-2 increased peak N-type Ca2+ currents 9-fold; co-expression with α1C increased L-type currents 2-fold and with α1G increased T-type currents 1.8-fold, establishing α2δ-2 as a functional channel auxiliary subunit that potentiates current amplitude across multiple channel types.","method":"cRNA co-injection in Xenopus oocytes, electrophysiology","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro across multiple channel combinations, replicated in subsequent studies","pmids":["10766861"],"is_preprint":false},{"year":2000,"finding":"α2δ-2 co-expression with α1C, α1E, and α1A subunits increased current density and shifted voltage dependence of activation and inactivation in a hyperpolarizing direction; co-expression with α1G accelerated decay and shifted steady-state inactivation, demonstrating gating modulation beyond simple current enhancement.","method":"Heterologous co-expression in Xenopus oocytes, electrophysiology","journal":"The European journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1 — in vitro functional reconstitution with multiple α1 subunits","pmids":["10762351"],"is_preprint":false},{"year":2001,"finding":"Loss-of-function mutations in Cacna2d2 (ducky mouse) reduce voltage-gated Ca2+ channel current density in cerebellar Purkinje cells without altering single-channel conductance, identifying α2δ-2 as required for normal calcium channel current amplitude specifically in Purkinje cells.","method":"Patch-clamp electrophysiology on acutely dissociated Purkinje cells from du/du mice; genetic mapping and sequencing","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — clean loss-of-function model with defined cellular electrophysiological phenotype, replicated by multiple ducky alleles","pmids":["11487633"],"is_preprint":false},{"year":2001,"finding":"The truncated ducky α2δ-2 protein (encoded by first 3 exons + 8 novel amino acids due to premature stop) acts as a dominant-negative when co-expressed with CaV2.1/β4 in vitro, reducing current density, whereas wild-type α2δ-2 increases it; du/du Purkinje cells show abnormal dendritic tree morphology.","method":"In vitro co-expression assay (Xenopus oocytes), Western blot detection of truncated protein, Purkinje cell morphology analysis in du/du mice","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstitution in vitro with mutagenesis/truncation plus cellular morphology readout","pmids":["11756448"],"is_preprint":false},{"year":2003,"finding":"The entla allele of Cacna2d2 encodes a full-length protein with a 39-amino-acid duplication near the N-terminus that disrupts the disulfide linkage between the α2 and δ portions; this results in 50% reduction in Ca2+ current density in Purkinje cells and >60% reduction in [3H]gabapentin maximum binding to cerebellar membranes.","method":"Western blot, patch-clamp electrophysiology on Purkinje cells, radioligand binding assay with [3H]gabapentin","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — biochemical, electrophysiological, and pharmacological characterization of a specific structural mutant","pmids":["14660671"],"is_preprint":false},{"year":2004,"finding":"Targeted disruption of Cacna2d2 in mice causes cerebellar granule cell apoptosis followed by Purkinje cell depletion, enhanced seizure susceptibility, and cardiac abnormalities including bradycardia, genetically demonstrating that α2δ-2 functions as an in vivo component of P/Q-type calcium channels essential for CNS and cardiac function.","method":"Knockout mouse phenotyping: histopathology, EEG, cardiac monitoring","journal":"The American journal of pathology","confidence":"High","confidence_rationale":"Tier 2 — clean KO with multiple defined cellular and organismal phenotypes","pmids":["15331424"],"is_preprint":false},{"year":2006,"finding":"α2δ-2 is completely concentrated in cholesterol-rich lipid raft microdomains in cerebellum, where it colocalizes with and co-immunoprecipitates with CaV2.1 and stomatin-family proteins; cholesterol depletion disrupts rafts and enhances CaV2.1/α2δ-2/β4 currents; a point mutation (R282A) reduces gabapentin affinity and reduces functional enhancement of CaV2.1 currents, linking raft association and gabapentin-binding site integrity to α2δ-2 function.","method":"Detergent-resistant membrane fractionation, co-immunoprecipitation, electrophysiology, cholesterol depletion, point mutagenesis","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods in native tissue and cell line with mutagenesis and functional validation","pmids":["16928863"],"is_preprint":false},{"year":2010,"finding":"Gabapentin specifically blocks the recycling of α2δ-2 from Rab11-positive recycling endosomes to the plasma membrane (not internalization); this effect requires gabapentin binding to α2δ-2 (abrogated by R282A mutation) and is prevented by dominant-negative Rab11 S25N, leading to reduced α2δ-2 cell-surface levels and reduced calcium channel currents.","method":"α-bungarotoxin binding site-tagged α2δ-2 surface trafficking assay, dominant-negative Rab11 co-expression, electrophysiology in cell lines and primary neurons","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1-2 — mechanistic dissection of trafficking with orthogonal approaches, mutagenesis, and functional readout","pmids":["20861389"],"is_preprint":false},{"year":2011,"finding":"Pregabalin's anxiolytic-like effect in the Vogel conflict test is mediated through the α2δ-1 subunit, not α2δ-2: α2δ-1 R217A knockin mice are insensitive to pregabalin whereas α2δ-2 R279A knockin mice retain pregabalin response, establishing the binding-site specificity for in vivo pharmacological action.","method":"Point-mutant knockin mouse strains (R217A and R279A), behavioral pharmacology (Vogel conflict test)","journal":"The Journal of pharmacology and experimental therapeutics","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis using point-mutant knockin mice with defined behavioral phenotype","pmids":["21558437"],"is_preprint":false},{"year":2020,"finding":"Loss of α2δ-2 in Purkinje cells alters climbing fiber (CF) synapse structure and function: CF terminals relocate more proximally on dendrites, CF terminals show twice as many vesicle release sites (by EM), multivesicular transmission increases, and CF-evoked EPSC amplitude increases with faster decay due to enhanced glutamate reuptake, collectively degrading complex spike information transfer and contributing to ataxia.","method":"Whole-cell patch-clamp in acute cerebellar slices from Cacna2d2 KO mice, VGLUT2 immunofluorescence, electron microscopy, computational modeling","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods (electrophysiology, EM, modeling) with clean KO and defined mechanistic phenotype","pmids":["32086258"],"is_preprint":false},{"year":2021,"finding":"α2δ-2 is required for functional coupling of postsynaptic voltage-dependent calcium entry to depolarization-induced suppression of excitation (DSE, via retrograde endocannabinoid signaling) and to spike afterhyperpolarization in Purkinje cells; loss of α2δ-2 disrupts these calcium-dependent signaling outputs without affecting total calcium influx.","method":"Whole-cell patch-clamp recordings in Cacna2d2 KO mouse Purkinje cells, pharmacological dissection of DSE and AHP","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined postsynaptic calcium-coupling phenotype using electrophysiology","pmids":["34783012"],"is_preprint":false},{"year":2024,"finding":"The DEE-associated p.R593P (mouse R596P) mutation in α2δ-2 drastically decreases membrane expression and synaptic targeting of α2δ-2, alters biophysical properties of postsynaptic CaV1.3 channels, reduces presynaptic CaV2.1 abundance and presynaptic calcium transients in hippocampal neurons, reduces trans-synaptic recruitment of GABAA receptors and presynaptic synapsin clustering at glutamatergic synapses, and decreases amplitudes of glutamatergic miniature PSCs.","method":"Heterologous expression in tsA201 cells (electrophysiology), primary hippocampal neuron culture with lentiviral transduction, immunocytochemistry, calcium imaging, mEPSC recordings","journal":"Journal of neurochemistry","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods including functional electrophysiology, calcium imaging, and synaptic protein localization with disease-linked point mutant","pmids":["39161180"],"is_preprint":false},{"year":2025,"finding":"α2δ-2 forms a direct protein complex with GluK1 (but not GluK2) kainate receptors via its C-terminus, independently of its role as a calcium channel subunit; α2δ-2 co-expression augments GluK1 currents in HEK293 cells and promotes surface expression of GluK1; pregabalin binding to α2δ-2 abrogates this augmentation; conditional Purkinje cell knockdown of Cacna2d2 or Grik1 impairs motor coordination.","method":"Co-immunoprecipitation from cerebellar tissue and HEK293 cells, whole-cell patch-clamp in HEK293 and Purkinje cells, surface expression assay, CRISPR/Cas9 conditional knockdown, rotarod/beam-walking behavioral testing, α2δ-2 C-terminus peptide disruption","journal":"Brain : a journal of neurology","confidence":"High","confidence_rationale":"Tier 1-2 — reciprocal Co-IP from native tissue, functional reconstitution, mutagenesis, peptide disruption, and in vivo behavioral validation","pmids":["39439207"],"is_preprint":false},{"year":2003,"finding":"CACNA2D2 overexpression in 3p21.3-deficient NSCLC cells elevates intracellular free Ca2+, causes mitochondrial membrane depolarization prior to apoptosis, and triggers cytochrome c release, caspase-3 activation, and PARP cleavage, linking α2δ-2 to a Ca2+-dependent mitochondrial apoptosis pathway in cancer cells.","method":"Adenoviral vector-mediated gene transfer, intracellular Ca2+ measurement, mitochondrial membrane potential assay, cytochrome c immunoblot, caspase-3 activity assay","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 — multiple functional assays in cell lines, but single lab and overexpression system","pmids":["12555074"],"is_preprint":false},{"year":2019,"finding":"The lncRNA MIR210HG promotes CACNA2D2 promoter methylation by recruiting DNMT1; MIR210HG knockdown increases CACNA2D2 expression and inhibits NSCLC cell proliferation, an effect reversed by CACNA2D2 knockdown, positioning CACNA2D2 as an epigenetically silenced growth suppressor downstream of MIR210HG-DNMT1.","method":"RNA binding protein immunoprecipitation (RIP), chromatin immunoprecipitation (ChIP), bisulfite sequencing, siRNA knockdown, rescue experiments","journal":"OncoTargets and therapy","confidence":"Medium","confidence_rationale":"Tier 2 — RIP and ChIP establish direct DNMT1-promoter interaction, with functional rescue, but single lab","pmids":["31190878"],"is_preprint":false},{"year":2024,"finding":"circMYLK4 physically interacts with CACNA2D2 protein, inhibiting Ca2+ release from the sarcoplasmic reticulum in skeletal muscle, which decreases cytoplasmic Ca2+, suppresses glycogen breakdown enzymes PHKB and PHKG1, and shifts metabolism from glycolysis to mitochondrial oxidative phosphorylation.","method":"Multi-omics (transcriptomics, proteomics, phosphoproteomics, metabolomics), RNA pulldown/RIP to identify circMYLK4-CACNA2D2 interaction, intracellular Ca2+ measurement","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 — binding interaction demonstrated and functional metabolic readout provided, but mechanistic link between Ca2+ channel inhibition and metabolic switch is partly inferential","pmids":["38823637"],"is_preprint":false},{"year":2017,"finding":"miR-1231 targets Cacna2d2 and suppresses its expression in ischemic hearts; knockdown of miR-1231 ameliorates arrhythmias in rat MI hearts, while Cacna2d2 knockdown alone induces arrhythmias despite miR-1231 inhibition, placing Cacna2d2 downstream of miR-1231 in the regulation of cardiac rhythm.","method":"miRNA target prediction validated by gene expression array, in vivo miR-1231 inhibition/overexpression in rat MI model, Cacna2d2 siRNA knockdown, ECG recording","journal":"American journal of translational research","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis in vivo with defined arrhythmia phenotype, but target validation is indirect","pmids":["28469787"],"is_preprint":false},{"year":2022,"finding":"Following surgical decompression in a rat cervical spondylotic myelopathy model, α2δ-2 expression decreases in the anterior horn while axonal regeneration markers (5HT, GAP43) increase; gabapentin-mediated inhibition of α2δ-2 after decompression further enhances axonal regeneration and functional recovery, identifying α2δ-2 as an inhibitor of axonal regeneration in the injured spinal cord.","method":"Western blot and immunofluorescence for α2δ-2, 5HT, and GAP43 in rat spinal cord; gabapentin pharmacological intervention; behavioral assessment","journal":"BMC neuroscience","confidence":"Low","confidence_rationale":"Tier 3 — pharmacological inhibition with gabapentin (non-specific) and correlative protein expression; no direct mechanistic dissection","pmids":["35778700"],"is_preprint":false}],"current_model":"CACNA2D2 encodes the α2δ-2 auxiliary subunit of voltage-gated calcium channels, which potentiates Ca2+ current amplitude and modulates gating kinetics of multiple CaV channel types (CaV2.1/P-Q, CaV2.2/N, CaV1.2/L, CaV3.1/T) through direct physical association; it is concentrated in lipid rafts with CaV2.1 in cerebellum and traffics to the plasma membrane via Rab11-dependent recycling endosomes (a pathway disrupted by gabapentin/pregabalin); in Purkinje cells, α2δ-2 controls climbing fiber synapse structure and positioning, multivesicular release, postsynaptic calcium coupling to DSE and afterhyperpolarization, and additionally forms a direct complex with GluK1 kainate receptors through its C-terminus to promote their synaptic surface expression and activity independently of calcium channel function; loss-of-function mutations cause epileptic encephalopathy and cerebellar ataxia in mice and humans."},"narrative":{"teleology":[{"year":2000,"claim":"Establishing α2δ-2 as a functional calcium channel auxiliary subunit resolved whether the newly cloned CACNA2D2 gene product modulates channel activity: co-expression potentiated current amplitude across N-type, L-type, and T-type channels and shifted voltage-dependent gating.","evidence":"Heterologous co-expression with multiple α1 subunits in Xenopus oocytes, two-electrode voltage clamp","pmids":["10766861","10762351"],"confidence":"High","gaps":["No native tissue validation at this stage","Trafficking mechanism for current enhancement unknown","Stoichiometry of α2δ-2 in channel complexes not defined"]},{"year":2001,"claim":"The ducky mouse demonstrated that α2δ-2 is required in vivo for normal calcium channel current density in Purkinje cells and that a truncated α2δ-2 acts as a dominant-negative, linking loss of function to cerebellar pathology.","evidence":"Patch-clamp on acutely dissociated Purkinje cells from du/du mice; in vitro dominant-negative assay with truncated protein","pmids":["11487633","11756448"],"confidence":"High","gaps":["Mechanism by which α2δ-2 controls current density (trafficking vs. channel open probability) unresolved","Purkinje cell dendritic morphology defects not mechanistically linked to channel function"]},{"year":2003,"claim":"The entla allele revealed that the α2-δ disulfide linkage is structurally critical: disruption halved Purkinje cell Ca2+ currents and drastically reduced gabapentin binding, linking protein structural integrity to both channel function and drug pharmacology.","evidence":"Biochemical and electrophysiological characterization of entla mice carrying a 39-amino-acid duplication; radioligand binding","pmids":["14660671"],"confidence":"High","gaps":["Atomic-level structural basis for disulfide linkage requirement unknown","Whether gabapentin binding loss is cause or consequence of misfolding not distinguished"]},{"year":2004,"claim":"Targeted Cacna2d2 knockout confirmed organismal requirements for α2δ-2: cerebellar granule cell apoptosis, Purkinje cell loss, enhanced seizure susceptibility, and cardiac bradycardia established α2δ-2 as essential for CNS and cardiac physiology.","evidence":"Knockout mouse phenotyping with histopathology, EEG, and cardiac monitoring","pmids":["15331424"],"confidence":"High","gaps":["Cell-autonomous vs. circuit-level contributions to seizures not separated","Cardiac mechanism (channel subtype involved) not defined"]},{"year":2006,"claim":"Discovery that α2δ-2 and CaV2.1 are concentrated in lipid raft microdomains in cerebellum, and that the R282A mutation reduces both gabapentin affinity and functional channel enhancement, established raft localization as a feature of native α2δ-2 complexes.","evidence":"Detergent-resistant membrane fractionation, co-immunoprecipitation from cerebellum, electrophysiology with R282A mutant, cholesterol depletion","pmids":["16928863"],"confidence":"High","gaps":["Functional consequence of raft disruption in neurons not tested","Identity of raft-associated binding partners beyond stomatin-family not explored"]},{"year":2010,"claim":"Mechanistic dissection of gabapentin action revealed that the drug blocks α2δ-2 recycling from Rab11-positive endosomes to the plasma membrane rather than promoting internalization, identifying the specific trafficking step regulated by the drug.","evidence":"Surface trafficking assay with BBS-tagged α2δ-2, dominant-negative Rab11 co-expression, R282A mutagenesis, electrophysiology in cell lines and neurons","pmids":["20861389"],"confidence":"High","gaps":["Whether Rab11-dependent recycling is the primary steady-state trafficking route for α2δ-2 in vivo not established","Molecular intermediates between gabapentin binding and Rab11 pathway blockade unknown"]},{"year":2011,"claim":"In vivo pharmacogenetic dissection using R279A knockin mice showed that pregabalin's anxiolytic effect operates through α2δ-1 rather than α2δ-2, delineating subunit-specific pharmacological roles despite shared drug binding.","evidence":"Point-mutant knockin mice (α2δ-1 R217A and α2δ-2 R279A), Vogel conflict behavioral test with pregabalin","pmids":["21558437"],"confidence":"High","gaps":["Whether other gabapentinoid effects (analgesic, anticonvulsant) are similarly subunit-specific not addressed","Mechanism by which α2δ-1 vs. α2δ-2 differentially regulate anxiety circuits unknown"]},{"year":2020,"claim":"Loss of α2δ-2 was shown to reorganize climbing fiber synapse architecture — terminals relocate proximally, double their release sites, and increase multivesicular release — revealing a trans-synaptic structural role for the auxiliary subunit beyond biophysical channel modulation.","evidence":"Whole-cell patch-clamp, VGLUT2 immunofluorescence, electron microscopy, and computational modeling in Cacna2d2 KO cerebellar slices","pmids":["32086258"],"confidence":"High","gaps":["Molecular pathway linking postsynaptic α2δ-2 loss to presynaptic structural remodeling not identified","Whether this trans-synaptic effect depends on calcium channel function or an independent role unresolved"]},{"year":2021,"claim":"α2δ-2 was found to be specifically required for coupling postsynaptic calcium entry to depolarization-induced suppression of excitation (DSE) and afterhyperpolarization in Purkinje cells, without affecting total calcium influx, revealing a role in calcium microdomain signaling.","evidence":"Whole-cell electrophysiology in Cacna2d2 KO Purkinje cells with pharmacological dissection of DSE and AHP","pmids":["34783012"],"confidence":"High","gaps":["Whether α2δ-2 scaffolds endocannabinoid synthesis machinery or positions channels near specific effectors not determined","Calcium sensor identity for the α2δ-2-dependent coupling not identified"]},{"year":2024,"claim":"A human DEE-associated R593P mutation was shown to drastically reduce α2δ-2 membrane expression and synaptic targeting, impair presynaptic CaV2.1 abundance and calcium transients, and reduce trans-synaptic GABAA receptor recruitment, providing a mechanistic basis for the human disease mutation.","evidence":"Electrophysiology in tsA201 cells, lentiviral expression in primary hippocampal neurons, immunocytochemistry, calcium imaging, mEPSC recordings","pmids":["39161180"],"confidence":"High","gaps":["Whether R593P represents a trafficking-deficient or folding-deficient class of mutation not resolved","In vivo knockin confirmation of R593P phenotype lacking"]},{"year":2025,"claim":"Discovery of a direct α2δ-2–GluK1 kainate receptor complex, mediated by the α2δ-2 C-terminus and independent of calcium channel function, fundamentally expanded the functional scope of α2δ-2 beyond voltage-gated calcium channel biology.","evidence":"Reciprocal co-immunoprecipitation from cerebellum and HEK293 cells, electrophysiology, surface expression assay, C-terminus peptide disruption, conditional CRISPR knockdown with behavioral validation","pmids":["39439207"],"confidence":"High","gaps":["Structural basis of α2δ-2–GluK1 interaction not resolved","Whether other α2δ subunits interact with kainate receptors not tested","Synaptic consequences of GluK1 loss of surface expression via α2δ-2 mechanism in Purkinje cells not fully characterized"]},{"year":null,"claim":"Key unresolved questions include the structural basis for α2δ-2's dual roles as a calcium channel subunit and GluK1 receptor partner, the molecular identity of the trans-synaptic signaling pathway through which postsynaptic α2δ-2 controls presynaptic climbing fiber morphology, and the contribution of α2δ-2 to cardiac channel complexes.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of α2δ-2 in complex with CaV or GluK1","Trans-synaptic signaling mechanism for climbing fiber remodeling unknown","Cardiac α2δ-2 channel complex identity and function uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,2,3,10]},{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,1,4]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[9,11]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,6,7,11]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[7]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[7]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[2,9,10,12]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,1,4]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[10,12]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[7,11]}],"complexes":["CaV2.1/P-Q-type calcium channel complex","α2δ-2–GluK1 kainate receptor complex"],"partners":["CACNA1A","CACNA1C","CACNA1G","CACNA1E","GRIK1","RAB11A","DNMT1"],"other_free_text":[]},"mechanistic_narrative":"CACNA2D2 encodes the α2δ-2 auxiliary subunit of voltage-gated calcium channels, serving as a critical modulator of calcium channel trafficking, current amplitude, and gating across multiple CaV subtypes (CaV1.2, CaV2.1, CaV2.2, CaV3.1) in the nervous system and heart [PMID:10766861, PMID:10762351]. In cerebellar Purkinje cells, α2δ-2 resides in lipid raft microdomains with CaV2.1, traffics to the plasma membrane via Rab11-dependent recycling endosomes — a pathway blocked by gabapentin/pregabalin — and is required for proper climbing fiber synapse structure, multivesicular release, and postsynaptic calcium coupling to retrograde endocannabinoid signaling and afterhyperpolarization [PMID:16928863, PMID:20861389, PMID:32086258, PMID:34783012]. Beyond its canonical calcium channel role, α2δ-2 forms a direct complex with GluK1 kainate receptors via its C-terminus to promote their synaptic surface expression and current independently of calcium channel function [PMID:39439207]. Loss-of-function mutations in CACNA2D2 cause epileptic encephalopathy, cerebellar ataxia, and cardiac abnormalities in mice and humans [PMID:11487633, PMID:15331424, PMID:39161180]."},"prefetch_data":{"uniprot":{"accession":"Q9NY47","full_name":"Voltage-dependent calcium channel subunit alpha-2/delta-2","aliases":["Voltage-gated calcium channel subunit alpha-2/delta-2"],"length_aa":1150,"mass_kda":129.8,"function":"The alpha-2/delta subunit of voltage-dependent calcium channels regulates calcium current density and activation/inactivation kinetics of the calcium channel. Acts as a regulatory subunit for P/Q-type calcium channel (CACNA1A), N-type (CACNA1B), L-type (CACNA1C OR CACNA1D) and possibly T-type (CACNA1G) (PubMed:15111129, PubMed:23339110). Overexpression induces apoptosis","subcellular_location":"Membrane","url":"https://www.uniprot.org/uniprotkb/Q9NY47/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CACNA2D2","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CANX","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/CACNA2D2","total_profiled":1310},"omim":[{"mim_id":"618501","title":"CEREBELLAR ATROPHY WITH SEIZURES AND VARIABLE DEVELOPMENTAL DELAY; CASVDD","url":"https://www.omim.org/entry/618501"},{"mim_id":"611608","title":"MICRO RNA 183; MIR183","url":"https://www.omim.org/entry/611608"},{"mim_id":"608171","title":"CALCIUM CHANNEL, VOLTAGE-DEPENDENT, ALPHA-2/DELTA SUBUNIT 4; CACNA2D4","url":"https://www.omim.org/entry/608171"},{"mim_id":"607082","title":"CALCIUM CHANNEL, VOLTAGE-DEPENDENT, ALPHA-2/DELTA SUBUNIT 2; CACNA2D2","url":"https://www.omim.org/entry/607082"},{"mim_id":"606399","title":"CALCIUM CHANNEL, VOLTAGE-DEPENDENT, ALPHA-2/DELTA SUBUNIT 3; CACNA2D3","url":"https://www.omim.org/entry/606399"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"},{"location":"Plasma membrane","reliability":"Additional"},{"location":"Flagellar centriole","reliability":"Additional"},{"location":"Mid piece","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"lung","ntpm":46.3}],"url":"https://www.proteinatlas.org/search/CACNA2D2"},"hgnc":{"alias_symbol":["KIAA0558","alpha2delta-2"],"prev_symbol":[]},"alphafold":{"accession":"Q9NY47","domains":[{"cath_id":"-","chopping":"80-108_678-809_816-849","consensus_level":"high","plddt":89.5812,"start":80,"end":849},{"cath_id":"-","chopping":"119-171_184-280_493-531","consensus_level":"high","plddt":87.4551,"start":119,"end":531},{"cath_id":"3.40.50.410","chopping":"289-463","consensus_level":"high","plddt":90.6753,"start":289,"end":463},{"cath_id":"3.30.450.20","chopping":"539-646","consensus_level":"high","plddt":90.7272,"start":539,"end":646},{"cath_id":"3.30.450","chopping":"889-943_1014-1083","consensus_level":"high","plddt":87.2234,"start":889,"end":1083}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NY47","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NY47-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NY47-F1-predicted_aligned_error_v6.png","plddt_mean":80.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CACNA2D2","jax_strain_url":"https://www.jax.org/strain/search?query=CACNA2D2"},"sequence":{"accession":"Q9NY47","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NY47.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NY47/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NY47"}},"corpus_meta":[{"pmid":"11487633","id":"PMC_11487633","title":"Ducky mouse phenotype of epilepsy and ataxia is associated with mutations in the Cacna2d2 gene and decreased calcium channel current in cerebellar Purkinje cells.","date":"2001","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/11487633","citation_count":243,"is_preprint":false},{"pmid":"10766861","id":"PMC_10766861","title":"Functional properties of a new voltage-dependent calcium channel alpha(2)delta auxiliary subunit gene (CACNA2D2).","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10766861","citation_count":145,"is_preprint":false},{"pmid":"16928863","id":"PMC_16928863","title":"The calcium channel alpha2delta-2 subunit partitions with CaV2.1 into lipid rafts in cerebellum: implications for localization and function.","date":"2006","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/16928863","citation_count":125,"is_preprint":false},{"pmid":"11756448","id":"PMC_11756448","title":"The ducky mutation in Cacna2d2 results in altered Purkinje cell morphology and is associated with the expression of a truncated alpha 2 delta-2 protein with abnormal function.","date":"2001","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11756448","citation_count":120,"is_preprint":false},{"pmid":"20861389","id":"PMC_20861389","title":"The alpha2delta ligand gabapentin inhibits the Rab11-dependent recycling of the calcium channel subunit alpha2delta-2.","date":"2010","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/20861389","citation_count":114,"is_preprint":false},{"pmid":"10762351","id":"PMC_10762351","title":"Neuronal distribution and functional characterization of the calcium channel alpha2delta-2 subunit.","date":"2000","source":"The European journal of neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/10762351","citation_count":99,"is_preprint":false},{"pmid":"15331424","id":"PMC_15331424","title":"Cerebellar ataxia, seizures, premature death, and cardiac abnormalities in mice with targeted disruption of the Cacna2d2 gene.","date":"2004","source":"The American journal of pathology","url":"https://pubmed.ncbi.nlm.nih.gov/15331424","citation_count":78,"is_preprint":false},{"pmid":"24358150","id":"PMC_24358150","title":"A novel null homozygous mutation confirms CACNA2D2 as a gene mutated in epileptic encephalopathy.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24358150","citation_count":72,"is_preprint":false},{"pmid":"14660671","id":"PMC_14660671","title":"entla, a novel epileptic and ataxic Cacna2d2 mutant of the mouse.","date":"2003","source":"The Journal of biological 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Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/32086258","citation_count":26,"is_preprint":false},{"pmid":"30410802","id":"PMC_30410802","title":"Epileptic Encephalopathy and Cerebellar Atrophy Resulting from Compound Heterozygous CACNA2D2 Variants.","date":"2018","source":"Case reports in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30410802","citation_count":20,"is_preprint":false},{"pmid":"27379157","id":"PMC_27379157","title":"Do Copy Number Changes in CACNA2D2, CACNA2D3, and CACNA1D Constitute a Predisposing Risk Factor for Alzheimer's Disease?","date":"2016","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/27379157","citation_count":17,"is_preprint":false},{"pmid":"28469787","id":"PMC_28469787","title":"miR-1231 exacerbates arrhythmia by targeting calciumchannel gene CACNA2D2 in myocardial infarction.","date":"2017","source":"American journal of translational research","url":"https://pubmed.ncbi.nlm.nih.gov/28469787","citation_count":15,"is_preprint":false},{"pmid":"34783012","id":"PMC_34783012","title":"α2δ-2 is required for depolarization-induced suppression of excitation in Purkinje cells.","date":"2021","source":"The Journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/34783012","citation_count":8,"is_preprint":false},{"pmid":"39161180","id":"PMC_39161180","title":"A biallelic mutation in CACNA2D2 associated with developmental and epileptic encephalopathy affects calcium channel-dependent as well as synaptic functions of α2δ-2.","date":"2024","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/39161180","citation_count":7,"is_preprint":false},{"pmid":"28850479","id":"PMC_28850479","title":"Genetic susceptibility to postherniotomy pain. The influence of polymorphisms in the Mu opioid receptor, TNF-α, GRIK3, GCH1, BDNF and CACNA2D2 genes.","date":"2016","source":"Scandinavian journal of pain","url":"https://pubmed.ncbi.nlm.nih.gov/28850479","citation_count":5,"is_preprint":false},{"pmid":"32071821","id":"PMC_32071821","title":"Association of the CACNA2D2 gene with schizophrenia in Chinese Han population.","date":"2020","source":"PeerJ","url":"https://pubmed.ncbi.nlm.nih.gov/32071821","citation_count":4,"is_preprint":false},{"pmid":"37047559","id":"PMC_37047559","title":"MicroRNA-423-5p Mediates Cocaine-Induced Smooth Muscle Cell Contraction by Targeting Cacna2d2.","date":"2023","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/37047559","citation_count":4,"is_preprint":false},{"pmid":"39439207","id":"PMC_39439207","title":"α2δ-2 regulates synaptic GluK1 kainate receptors in Purkinje cells and motor coordination.","date":"2025","source":"Brain : a journal of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/39439207","citation_count":3,"is_preprint":false},{"pmid":"38823637","id":"PMC_38823637","title":"Circular RNA circMYLK4 shifts energy metabolism from glycolysis to OXPHOS by binding to the calcium channel auxiliary subunit CACNA2D2.","date":"2024","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/38823637","citation_count":3,"is_preprint":false},{"pmid":"40158290","id":"PMC_40158290","title":"iPSC screening identifies CACNA2D2 as a potential therapeutic target for FTLD-Tau.","date":"2025","source":"European journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/40158290","citation_count":2,"is_preprint":false},{"pmid":"37986872","id":"PMC_37986872","title":"Altered hippocampal activation in seizure-prone CACNA2D2 knockout mice.","date":"2023","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/37986872","citation_count":1,"is_preprint":false},{"pmid":"38749701","id":"PMC_38749701","title":"Altered Hippocampal Activation in Seizure-Prone CACNA2D2 Knock-out Mice.","date":"2024","source":"eNeuro","url":"https://pubmed.ncbi.nlm.nih.gov/38749701","citation_count":1,"is_preprint":false},{"pmid":"35778700","id":"PMC_35778700","title":"Cacna2d2 inhibits axonal regeneration following surgical decompression in a rat model of cervical spondylotic myelopathy.","date":"2022","source":"BMC neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/35778700","citation_count":1,"is_preprint":false},{"pmid":"41961764","id":"PMC_41961764","title":"CACNA2D2 rs56287038:G&gt;T and SCN1A rs2298771:C&gt;T Variants Are Associated with Antiseizure Medication Response in Turkish Epilepsy Patients : A Pilot Study.","date":"2026","source":"Neuropsychobiology","url":"https://pubmed.ncbi.nlm.nih.gov/41961764","citation_count":0,"is_preprint":false},{"pmid":"41873845","id":"PMC_41873845","title":"A CACNA2D2-Related Recessive Form of Cerebellar Abiotrophy in Angus Cattle.","date":"2026","source":"Animal genetics","url":"https://pubmed.ncbi.nlm.nih.gov/41873845","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.08.28.25334625","title":"Identification of potential changes in protein abundance associated with post-traumatic stress disorder through brain proteome-wide association study","date":"2025-09-02","source":"bioRxiv","url":"https://doi.org/10.1101/2025.08.28.25334625","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.07.17.603708","title":"Super-enhancer-driven<i>CACNA2D2</i>is an EWSR1::WT1 signature gene encoding a diagnostic marker for desmoplastic small round cell tumor (DSRCT)","date":"2024-07-21","source":"bioRxiv","url":"https://doi.org/10.1101/2024.07.17.603708","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":19189,"output_tokens":4768,"usd":0.064544},"stage2":{"model":"claude-opus-4-6","input_tokens":8470,"output_tokens":3291,"usd":0.186938},"total_usd":0.251482,"stage1_batch_id":"msgbatch_011kfMfE81o6CTcyhVUqumuW","stage2_batch_id":"msgbatch_01DTputS6WNkH745x1nVSoBo","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2000,\n      \"finding\": \"CACNA2D2 encodes the α2δ-2 auxiliary subunit of voltage-gated Ca2+ channels; when co-expressed with α1B/β3 in Xenopus oocytes, α2δ-2 increased peak N-type Ca2+ currents 9-fold; co-expression with α1C increased L-type currents 2-fold and with α1G increased T-type currents 1.8-fold, establishing α2δ-2 as a functional channel auxiliary subunit that potentiates current amplitude across multiple channel types.\",\n      \"method\": \"cRNA co-injection in Xenopus oocytes, electrophysiology\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro across multiple channel combinations, replicated in subsequent studies\",\n      \"pmids\": [\"10766861\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"α2δ-2 co-expression with α1C, α1E, and α1A subunits increased current density and shifted voltage dependence of activation and inactivation in a hyperpolarizing direction; co-expression with α1G accelerated decay and shifted steady-state inactivation, demonstrating gating modulation beyond simple current enhancement.\",\n      \"method\": \"Heterologous co-expression in Xenopus oocytes, electrophysiology\",\n      \"journal\": \"The European journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro functional reconstitution with multiple α1 subunits\",\n      \"pmids\": [\"10762351\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Loss-of-function mutations in Cacna2d2 (ducky mouse) reduce voltage-gated Ca2+ channel current density in cerebellar Purkinje cells without altering single-channel conductance, identifying α2δ-2 as required for normal calcium channel current amplitude specifically in Purkinje cells.\",\n      \"method\": \"Patch-clamp electrophysiology on acutely dissociated Purkinje cells from du/du mice; genetic mapping and sequencing\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean loss-of-function model with defined cellular electrophysiological phenotype, replicated by multiple ducky alleles\",\n      \"pmids\": [\"11487633\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The truncated ducky α2δ-2 protein (encoded by first 3 exons + 8 novel amino acids due to premature stop) acts as a dominant-negative when co-expressed with CaV2.1/β4 in vitro, reducing current density, whereas wild-type α2δ-2 increases it; du/du Purkinje cells show abnormal dendritic tree morphology.\",\n      \"method\": \"In vitro co-expression assay (Xenopus oocytes), Western blot detection of truncated protein, Purkinje cell morphology analysis in du/du mice\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution in vitro with mutagenesis/truncation plus cellular morphology readout\",\n      \"pmids\": [\"11756448\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The entla allele of Cacna2d2 encodes a full-length protein with a 39-amino-acid duplication near the N-terminus that disrupts the disulfide linkage between the α2 and δ portions; this results in 50% reduction in Ca2+ current density in Purkinje cells and >60% reduction in [3H]gabapentin maximum binding to cerebellar membranes.\",\n      \"method\": \"Western blot, patch-clamp electrophysiology on Purkinje cells, radioligand binding assay with [3H]gabapentin\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — biochemical, electrophysiological, and pharmacological characterization of a specific structural mutant\",\n      \"pmids\": [\"14660671\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Targeted disruption of Cacna2d2 in mice causes cerebellar granule cell apoptosis followed by Purkinje cell depletion, enhanced seizure susceptibility, and cardiac abnormalities including bradycardia, genetically demonstrating that α2δ-2 functions as an in vivo component of P/Q-type calcium channels essential for CNS and cardiac function.\",\n      \"method\": \"Knockout mouse phenotyping: histopathology, EEG, cardiac monitoring\",\n      \"journal\": \"The American journal of pathology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with multiple defined cellular and organismal phenotypes\",\n      \"pmids\": [\"15331424\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"α2δ-2 is completely concentrated in cholesterol-rich lipid raft microdomains in cerebellum, where it colocalizes with and co-immunoprecipitates with CaV2.1 and stomatin-family proteins; cholesterol depletion disrupts rafts and enhances CaV2.1/α2δ-2/β4 currents; a point mutation (R282A) reduces gabapentin affinity and reduces functional enhancement of CaV2.1 currents, linking raft association and gabapentin-binding site integrity to α2δ-2 function.\",\n      \"method\": \"Detergent-resistant membrane fractionation, co-immunoprecipitation, electrophysiology, cholesterol depletion, point mutagenesis\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods in native tissue and cell line with mutagenesis and functional validation\",\n      \"pmids\": [\"16928863\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Gabapentin specifically blocks the recycling of α2δ-2 from Rab11-positive recycling endosomes to the plasma membrane (not internalization); this effect requires gabapentin binding to α2δ-2 (abrogated by R282A mutation) and is prevented by dominant-negative Rab11 S25N, leading to reduced α2δ-2 cell-surface levels and reduced calcium channel currents.\",\n      \"method\": \"α-bungarotoxin binding site-tagged α2δ-2 surface trafficking assay, dominant-negative Rab11 co-expression, electrophysiology in cell lines and primary neurons\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — mechanistic dissection of trafficking with orthogonal approaches, mutagenesis, and functional readout\",\n      \"pmids\": [\"20861389\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Pregabalin's anxiolytic-like effect in the Vogel conflict test is mediated through the α2δ-1 subunit, not α2δ-2: α2δ-1 R217A knockin mice are insensitive to pregabalin whereas α2δ-2 R279A knockin mice retain pregabalin response, establishing the binding-site specificity for in vivo pharmacological action.\",\n      \"method\": \"Point-mutant knockin mouse strains (R217A and R279A), behavioral pharmacology (Vogel conflict test)\",\n      \"journal\": \"The Journal of pharmacology and experimental therapeutics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis using point-mutant knockin mice with defined behavioral phenotype\",\n      \"pmids\": [\"21558437\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Loss of α2δ-2 in Purkinje cells alters climbing fiber (CF) synapse structure and function: CF terminals relocate more proximally on dendrites, CF terminals show twice as many vesicle release sites (by EM), multivesicular transmission increases, and CF-evoked EPSC amplitude increases with faster decay due to enhanced glutamate reuptake, collectively degrading complex spike information transfer and contributing to ataxia.\",\n      \"method\": \"Whole-cell patch-clamp in acute cerebellar slices from Cacna2d2 KO mice, VGLUT2 immunofluorescence, electron microscopy, computational modeling\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (electrophysiology, EM, modeling) with clean KO and defined mechanistic phenotype\",\n      \"pmids\": [\"32086258\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"α2δ-2 is required for functional coupling of postsynaptic voltage-dependent calcium entry to depolarization-induced suppression of excitation (DSE, via retrograde endocannabinoid signaling) and to spike afterhyperpolarization in Purkinje cells; loss of α2δ-2 disrupts these calcium-dependent signaling outputs without affecting total calcium influx.\",\n      \"method\": \"Whole-cell patch-clamp recordings in Cacna2d2 KO mouse Purkinje cells, pharmacological dissection of DSE and AHP\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined postsynaptic calcium-coupling phenotype using electrophysiology\",\n      \"pmids\": [\"34783012\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The DEE-associated p.R593P (mouse R596P) mutation in α2δ-2 drastically decreases membrane expression and synaptic targeting of α2δ-2, alters biophysical properties of postsynaptic CaV1.3 channels, reduces presynaptic CaV2.1 abundance and presynaptic calcium transients in hippocampal neurons, reduces trans-synaptic recruitment of GABAA receptors and presynaptic synapsin clustering at glutamatergic synapses, and decreases amplitudes of glutamatergic miniature PSCs.\",\n      \"method\": \"Heterologous expression in tsA201 cells (electrophysiology), primary hippocampal neuron culture with lentiviral transduction, immunocytochemistry, calcium imaging, mEPSC recordings\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods including functional electrophysiology, calcium imaging, and synaptic protein localization with disease-linked point mutant\",\n      \"pmids\": [\"39161180\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"α2δ-2 forms a direct protein complex with GluK1 (but not GluK2) kainate receptors via its C-terminus, independently of its role as a calcium channel subunit; α2δ-2 co-expression augments GluK1 currents in HEK293 cells and promotes surface expression of GluK1; pregabalin binding to α2δ-2 abrogates this augmentation; conditional Purkinje cell knockdown of Cacna2d2 or Grik1 impairs motor coordination.\",\n      \"method\": \"Co-immunoprecipitation from cerebellar tissue and HEK293 cells, whole-cell patch-clamp in HEK293 and Purkinje cells, surface expression assay, CRISPR/Cas9 conditional knockdown, rotarod/beam-walking behavioral testing, α2δ-2 C-terminus peptide disruption\",\n      \"journal\": \"Brain : a journal of neurology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — reciprocal Co-IP from native tissue, functional reconstitution, mutagenesis, peptide disruption, and in vivo behavioral validation\",\n      \"pmids\": [\"39439207\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"CACNA2D2 overexpression in 3p21.3-deficient NSCLC cells elevates intracellular free Ca2+, causes mitochondrial membrane depolarization prior to apoptosis, and triggers cytochrome c release, caspase-3 activation, and PARP cleavage, linking α2δ-2 to a Ca2+-dependent mitochondrial apoptosis pathway in cancer cells.\",\n      \"method\": \"Adenoviral vector-mediated gene transfer, intracellular Ca2+ measurement, mitochondrial membrane potential assay, cytochrome c immunoblot, caspase-3 activity assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple functional assays in cell lines, but single lab and overexpression system\",\n      \"pmids\": [\"12555074\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The lncRNA MIR210HG promotes CACNA2D2 promoter methylation by recruiting DNMT1; MIR210HG knockdown increases CACNA2D2 expression and inhibits NSCLC cell proliferation, an effect reversed by CACNA2D2 knockdown, positioning CACNA2D2 as an epigenetically silenced growth suppressor downstream of MIR210HG-DNMT1.\",\n      \"method\": \"RNA binding protein immunoprecipitation (RIP), chromatin immunoprecipitation (ChIP), bisulfite sequencing, siRNA knockdown, rescue experiments\",\n      \"journal\": \"OncoTargets and therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — RIP and ChIP establish direct DNMT1-promoter interaction, with functional rescue, but single lab\",\n      \"pmids\": [\"31190878\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"circMYLK4 physically interacts with CACNA2D2 protein, inhibiting Ca2+ release from the sarcoplasmic reticulum in skeletal muscle, which decreases cytoplasmic Ca2+, suppresses glycogen breakdown enzymes PHKB and PHKG1, and shifts metabolism from glycolysis to mitochondrial oxidative phosphorylation.\",\n      \"method\": \"Multi-omics (transcriptomics, proteomics, phosphoproteomics, metabolomics), RNA pulldown/RIP to identify circMYLK4-CACNA2D2 interaction, intracellular Ca2+ measurement\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — binding interaction demonstrated and functional metabolic readout provided, but mechanistic link between Ca2+ channel inhibition and metabolic switch is partly inferential\",\n      \"pmids\": [\"38823637\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"miR-1231 targets Cacna2d2 and suppresses its expression in ischemic hearts; knockdown of miR-1231 ameliorates arrhythmias in rat MI hearts, while Cacna2d2 knockdown alone induces arrhythmias despite miR-1231 inhibition, placing Cacna2d2 downstream of miR-1231 in the regulation of cardiac rhythm.\",\n      \"method\": \"miRNA target prediction validated by gene expression array, in vivo miR-1231 inhibition/overexpression in rat MI model, Cacna2d2 siRNA knockdown, ECG recording\",\n      \"journal\": \"American journal of translational research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in vivo with defined arrhythmia phenotype, but target validation is indirect\",\n      \"pmids\": [\"28469787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Following surgical decompression in a rat cervical spondylotic myelopathy model, α2δ-2 expression decreases in the anterior horn while axonal regeneration markers (5HT, GAP43) increase; gabapentin-mediated inhibition of α2δ-2 after decompression further enhances axonal regeneration and functional recovery, identifying α2δ-2 as an inhibitor of axonal regeneration in the injured spinal cord.\",\n      \"method\": \"Western blot and immunofluorescence for α2δ-2, 5HT, and GAP43 in rat spinal cord; gabapentin pharmacological intervention; behavioral assessment\",\n      \"journal\": \"BMC neuroscience\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — pharmacological inhibition with gabapentin (non-specific) and correlative protein expression; no direct mechanistic dissection\",\n      \"pmids\": [\"35778700\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CACNA2D2 encodes the α2δ-2 auxiliary subunit of voltage-gated calcium channels, which potentiates Ca2+ current amplitude and modulates gating kinetics of multiple CaV channel types (CaV2.1/P-Q, CaV2.2/N, CaV1.2/L, CaV3.1/T) through direct physical association; it is concentrated in lipid rafts with CaV2.1 in cerebellum and traffics to the plasma membrane via Rab11-dependent recycling endosomes (a pathway disrupted by gabapentin/pregabalin); in Purkinje cells, α2δ-2 controls climbing fiber synapse structure and positioning, multivesicular release, postsynaptic calcium coupling to DSE and afterhyperpolarization, and additionally forms a direct complex with GluK1 kainate receptors through its C-terminus to promote their synaptic surface expression and activity independently of calcium channel function; loss-of-function mutations cause epileptic encephalopathy and cerebellar ataxia in mice and humans.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CACNA2D2 encodes the α2δ-2 auxiliary subunit of voltage-gated calcium channels, serving as a critical modulator of calcium channel trafficking, current amplitude, and gating across multiple CaV subtypes (CaV1.2, CaV2.1, CaV2.2, CaV3.1) in the nervous system and heart [PMID:10766861, PMID:10762351]. In cerebellar Purkinje cells, α2δ-2 resides in lipid raft microdomains with CaV2.1, traffics to the plasma membrane via Rab11-dependent recycling endosomes — a pathway blocked by gabapentin/pregabalin — and is required for proper climbing fiber synapse structure, multivesicular release, and postsynaptic calcium coupling to retrograde endocannabinoid signaling and afterhyperpolarization [PMID:16928863, PMID:20861389, PMID:32086258, PMID:34783012]. Beyond its canonical calcium channel role, α2δ-2 forms a direct complex with GluK1 kainate receptors via its C-terminus to promote their synaptic surface expression and current independently of calcium channel function [PMID:39439207]. Loss-of-function mutations in CACNA2D2 cause epileptic encephalopathy, cerebellar ataxia, and cardiac abnormalities in mice and humans [PMID:11487633, PMID:15331424, PMID:39161180].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Establishing α2δ-2 as a functional calcium channel auxiliary subunit resolved whether the newly cloned CACNA2D2 gene product modulates channel activity: co-expression potentiated current amplitude across N-type, L-type, and T-type channels and shifted voltage-dependent gating.\",\n      \"evidence\": \"Heterologous co-expression with multiple α1 subunits in Xenopus oocytes, two-electrode voltage clamp\",\n      \"pmids\": [\"10766861\", \"10762351\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No native tissue validation at this stage\", \"Trafficking mechanism for current enhancement unknown\", \"Stoichiometry of α2δ-2 in channel complexes not defined\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"The ducky mouse demonstrated that α2δ-2 is required in vivo for normal calcium channel current density in Purkinje cells and that a truncated α2δ-2 acts as a dominant-negative, linking loss of function to cerebellar pathology.\",\n      \"evidence\": \"Patch-clamp on acutely dissociated Purkinje cells from du/du mice; in vitro dominant-negative assay with truncated protein\",\n      \"pmids\": [\"11487633\", \"11756448\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which α2δ-2 controls current density (trafficking vs. channel open probability) unresolved\", \"Purkinje cell dendritic morphology defects not mechanistically linked to channel function\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"The entla allele revealed that the α2-δ disulfide linkage is structurally critical: disruption halved Purkinje cell Ca2+ currents and drastically reduced gabapentin binding, linking protein structural integrity to both channel function and drug pharmacology.\",\n      \"evidence\": \"Biochemical and electrophysiological characterization of entla mice carrying a 39-amino-acid duplication; radioligand binding\",\n      \"pmids\": [\"14660671\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic-level structural basis for disulfide linkage requirement unknown\", \"Whether gabapentin binding loss is cause or consequence of misfolding not distinguished\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Targeted Cacna2d2 knockout confirmed organismal requirements for α2δ-2: cerebellar granule cell apoptosis, Purkinje cell loss, enhanced seizure susceptibility, and cardiac bradycardia established α2δ-2 as essential for CNS and cardiac physiology.\",\n      \"evidence\": \"Knockout mouse phenotyping with histopathology, EEG, and cardiac monitoring\",\n      \"pmids\": [\"15331424\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cell-autonomous vs. circuit-level contributions to seizures not separated\", \"Cardiac mechanism (channel subtype involved) not defined\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Discovery that α2δ-2 and CaV2.1 are concentrated in lipid raft microdomains in cerebellum, and that the R282A mutation reduces both gabapentin affinity and functional channel enhancement, established raft localization as a feature of native α2δ-2 complexes.\",\n      \"evidence\": \"Detergent-resistant membrane fractionation, co-immunoprecipitation from cerebellum, electrophysiology with R282A mutant, cholesterol depletion\",\n      \"pmids\": [\"16928863\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of raft disruption in neurons not tested\", \"Identity of raft-associated binding partners beyond stomatin-family not explored\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Mechanistic dissection of gabapentin action revealed that the drug blocks α2δ-2 recycling from Rab11-positive endosomes to the plasma membrane rather than promoting internalization, identifying the specific trafficking step regulated by the drug.\",\n      \"evidence\": \"Surface trafficking assay with BBS-tagged α2δ-2, dominant-negative Rab11 co-expression, R282A mutagenesis, electrophysiology in cell lines and neurons\",\n      \"pmids\": [\"20861389\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Rab11-dependent recycling is the primary steady-state trafficking route for α2δ-2 in vivo not established\", \"Molecular intermediates between gabapentin binding and Rab11 pathway blockade unknown\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"In vivo pharmacogenetic dissection using R279A knockin mice showed that pregabalin's anxiolytic effect operates through α2δ-1 rather than α2δ-2, delineating subunit-specific pharmacological roles despite shared drug binding.\",\n      \"evidence\": \"Point-mutant knockin mice (α2δ-1 R217A and α2δ-2 R279A), Vogel conflict behavioral test with pregabalin\",\n      \"pmids\": [\"21558437\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether other gabapentinoid effects (analgesic, anticonvulsant) are similarly subunit-specific not addressed\", \"Mechanism by which α2δ-1 vs. α2δ-2 differentially regulate anxiety circuits unknown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Loss of α2δ-2 was shown to reorganize climbing fiber synapse architecture — terminals relocate proximally, double their release sites, and increase multivesicular release — revealing a trans-synaptic structural role for the auxiliary subunit beyond biophysical channel modulation.\",\n      \"evidence\": \"Whole-cell patch-clamp, VGLUT2 immunofluorescence, electron microscopy, and computational modeling in Cacna2d2 KO cerebellar slices\",\n      \"pmids\": [\"32086258\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular pathway linking postsynaptic α2δ-2 loss to presynaptic structural remodeling not identified\", \"Whether this trans-synaptic effect depends on calcium channel function or an independent role unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"α2δ-2 was found to be specifically required for coupling postsynaptic calcium entry to depolarization-induced suppression of excitation (DSE) and afterhyperpolarization in Purkinje cells, without affecting total calcium influx, revealing a role in calcium microdomain signaling.\",\n      \"evidence\": \"Whole-cell electrophysiology in Cacna2d2 KO Purkinje cells with pharmacological dissection of DSE and AHP\",\n      \"pmids\": [\"34783012\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether α2δ-2 scaffolds endocannabinoid synthesis machinery or positions channels near specific effectors not determined\", \"Calcium sensor identity for the α2δ-2-dependent coupling not identified\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"A human DEE-associated R593P mutation was shown to drastically reduce α2δ-2 membrane expression and synaptic targeting, impair presynaptic CaV2.1 abundance and calcium transients, and reduce trans-synaptic GABAA receptor recruitment, providing a mechanistic basis for the human disease mutation.\",\n      \"evidence\": \"Electrophysiology in tsA201 cells, lentiviral expression in primary hippocampal neurons, immunocytochemistry, calcium imaging, mEPSC recordings\",\n      \"pmids\": [\"39161180\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether R593P represents a trafficking-deficient or folding-deficient class of mutation not resolved\", \"In vivo knockin confirmation of R593P phenotype lacking\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Discovery of a direct α2δ-2–GluK1 kainate receptor complex, mediated by the α2δ-2 C-terminus and independent of calcium channel function, fundamentally expanded the functional scope of α2δ-2 beyond voltage-gated calcium channel biology.\",\n      \"evidence\": \"Reciprocal co-immunoprecipitation from cerebellum and HEK293 cells, electrophysiology, surface expression assay, C-terminus peptide disruption, conditional CRISPR knockdown with behavioral validation\",\n      \"pmids\": [\"39439207\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of α2δ-2–GluK1 interaction not resolved\", \"Whether other α2δ subunits interact with kainate receptors not tested\", \"Synaptic consequences of GluK1 loss of surface expression via α2δ-2 mechanism in Purkinje cells not fully characterized\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis for α2δ-2's dual roles as a calcium channel subunit and GluK1 receptor partner, the molecular identity of the trans-synaptic signaling pathway through which postsynaptic α2δ-2 controls presynaptic climbing fiber morphology, and the contribution of α2δ-2 to cardiac channel complexes.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No high-resolution structure of α2δ-2 in complex with CaV or GluK1\", \"Trans-synaptic signaling mechanism for climbing fiber remodeling unknown\", \"Cardiac α2δ-2 channel complex identity and function uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 2, 3, 10]},\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 1, 4]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [9, 11]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 6, 7, 11]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [7]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [2, 9, 10, 12]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 1, 4]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [10, 12]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [7, 11]}\n    ],\n    \"complexes\": [\n      \"CaV2.1/P-Q-type calcium channel complex\",\n      \"α2δ-2–GluK1 kainate receptor complex\"\n    ],\n    \"partners\": [\n      \"CACNA1A\",\n      \"CACNA1C\",\n      \"CACNA1G\",\n      \"CACNA1E\",\n      \"GRIK1\",\n      \"RAB11A\",\n      \"DNMT1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}