{"gene":"COPA","run_date":"2026-06-09T22:57:19","timeline":{"discoveries":[{"year":2015,"finding":"COPA (coatomer subunit α) variants in the WD40 domain impair binding to proteins targeted for retrograde Golgi-to-ER transport; expression of mutant COPA results in ER stress and upregulation of cytokines priming for a TH17 response, and patient-derived CD4+ T cells show skewing toward TH17 phenotype.","method":"Whole-exome sequencing, binding assays showing impaired cargo binding, ER stress assays, cytokine profiling, T cell phenotyping","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (binding assay, ER stress, T cell skewing) in founding study, subsequently replicated widely","pmids":["25894502"],"is_preprint":false},{"year":2020,"finding":"COPA physically interacts with STING; mutant COPA (and COPA silencing) causes accumulation of ER-resident STING at the Golgi, consistent with failure of Golgi-to-ER STING retrieval, leading to STING-dependent IFN signaling.","method":"Co-immunoprecipitation (COPA–STING interaction), overexpression of mutant COPA, siRNA knockdown, ISG/IFN-α quantification, subcellular localization of STING by immunofluorescence","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal interaction detected, STING localization shift demonstrated, replicated in companion paper same year","pmids":["32725128"],"is_preprint":false},{"year":2020,"finding":"Pathogenic COPA variants cause defective COPI-mediated Golgi-to-ER transport, leading to ligand-independent activation of STING and type I interferon-driven inflammation; SURF4 was identified as an adapter molecule that facilitates COPA-mediated retrieval of STING at the Golgi; activated STING contributes to immune dysregulation rescued in STING-deficient CopaE241K/+ mice.","method":"Genetic epistasis (CopaE241K/+ × STING-/- mice), SURF4 identification as COPA–STING adapter (pulldown/Co-IP), STING transport assays, knock-in mouse model with IFN readout","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo epistasis (genetic rescue), adapter protein identified, replicated by companion paper","pmids":["32725126"],"is_preprint":false},{"year":2010,"finding":"Crystal structure of the C-terminal domain (CTD) of α-COP in complex with full-length ε-COP at 2.9 Å resolution reveals that ε-COP adopts a TPR fold that wraps around a β-hairpin of the α-COP CTD, interlocking the two proteins; the α-COP CTD–ε-COP heterodimer directly interacts with the Dsl1 tethering complex.","method":"X-ray crystallography, solution biochemistry (heterodimer formation), direct binding assay with Dsl1 tethering complex","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure at 2.9 Å with biochemical validation of heterodimer and Dsl1 interaction, single lab","pmids":["20534429"],"is_preprint":false},{"year":1998,"finding":"ε-COP (Sec28p) functions to stabilize α-COP; loss of ε-COP causes rapid degradation of α-COP at restrictive temperature and ER trafficking defects; overproduction of ε-COP suppresses α-COP mutant defects by stabilizing α-COP levels.","method":"Yeast genetics (high-copy suppressor screen), temperature-sensitive mutant analysis, Western blotting for α-COP levels, carboxypeptidase Y trafficking assay, gel filtration of coatomer","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple genetic and biochemical methods, allele-specific synthetic lethality, single lab","pmids":["9463377"],"is_preprint":false},{"year":1998,"finding":"α-COP can discriminate between distinct di-lysine signals: ret1-1 mutant α-COP fails to bind the Wbp1p di-lysine signal in vitro but retains binding to the Emp47p di-lysine signal; other coatomer subunits (β'-, γ-, δ-, ζ-COP) are required for binding both di-lysine signals, placing α-COP in a regulatory gating role for selective retrograde transport.","method":"In vitro GST-fusion binding assay with coatomer from ret1 alleles, sucrose gradient fractionation, immunofluorescence, epistasis with multiple COP subunit mutants","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro reconstituted binding assay with mutagenesis (ret1 alleles), corroborated by in vivo localization, single lab","pmids":["9811561"],"is_preprint":false},{"year":1995,"finding":"α-COP is required for ER localization of di-lysine-tagged proteins: a hybrid Ste2p–Emp47p tail protein bearing the Emp47p di-lysine signal is mislocalized to the cell surface in the ret1-1 α-COP mutant; Emp47p cycles between Golgi and ER in a di-lysine-dependent but α-COP-independent manner, establishing that α-COP is needed for retrograde transport of canonical di-lysine cargo.","method":"Yeast genetics (ret1-1 mutant), immunofluorescence, retrograde transport assay in sec12 block, subcellular fractionation","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with functional cargo readout, multiple assays, foundational study replicated by later work","pmids":["7490292"],"is_preprint":false},{"year":1998,"finding":"α-COP specifically binds phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P3] among coatomer subunits; both D-3 and D-5 phosphates are critical for this interaction, suggesting a role for PtdIns(3,4,5)P3 in COPI vesicular trafficking.","method":"Photoaffinity labeling with [3H]BZDC-PtdIns(3,4,5)P3 and competitive displacement assays across COPI subunits","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — photoaffinity crosslinking with competition, selective for α-COP, single lab, single method","pmids":["9525943"],"is_preprint":false},{"year":2013,"finding":"Dilysine motifs in exon 2b of SMN protein mediate binding to α-COP (COPA); mutagenesis of the canonical dilysine motifs in SMN abrogates α-COP binding and eliminates the ability of SMN to restore neurite outgrowth in SMN-depleted NSC-34 cells.","method":"Co-immunoprecipitation, mutagenesis of SMN dilysine motifs, inducible knockdown cell system, neurite length measurement","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP and mutagenesis with functional readout (neurite length), single lab","pmids":["23727837"],"is_preprint":false},{"year":2015,"finding":"α-COP binding to SMN is required for neuronal process outgrowth: single amino acid mutants of α-COP that selectively abrogate SMN binding while retaining COPI-mediated Golgi-ER trafficking fail to support neurite outgrowth in NSC-34 cells and zebrafish motor neurons.","method":"Site-directed mutagenesis of α-COP, Co-IP to confirm loss of SMN binding, Golgi-ER trafficking assay, neurite length in NSC-34 cells, in vivo zebrafish motor neuron imaging","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — mutagenesis separating SMN-binding from COPI trafficking function, replicated in two model systems (cell culture + zebrafish), multiple orthogonal methods","pmids":["26464491"],"is_preprint":false},{"year":2020,"finding":"Mutant Copa in thymic epithelial cells impairs thymic selection of T cells, resulting in an increase in autoreactive T cells and decrease in regulatory T cells in peripheral tissues; adoptive transfer of Copa mutant T cells causes interstitial lung disease, establishing T cells as the pathogenic effector population.","method":"Germline Copa knock-in mouse model, thymocyte selection analysis, flow cytometry, adoptive transfer experiment","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo knock-in mouse with adoptive transfer epistasis establishing cellular mechanism, multiple orthogonal readouts, single lab","pmids":["32198142"],"is_preprint":false},{"year":2021,"finding":"COPA V242G (and other disease-causing COPA variants) augments STING-induced type I IFN promoter activity; in CopaV242G/+ dendritic cells the STING pathway is hyperactivated upon stimulation rather than constitutively, leading to increased type I IFN production; interstitial lung disease in CopaV242G/+ mice is STING-dependent.","method":"In vitro IFN promoter reporter assay, CopaV242G/+ knock-in mouse model, STING pathway activation assays in dendritic cells, ISG expression analysis","journal":"Arthritis & rheumatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro functional assay + in vivo mouse model, single lab, two orthogonal approaches","pmids":["33982886"],"is_preprint":false},{"year":2024,"finding":"Heterozygous mutations in the C-terminal domain (CTD) of COPA (p.C1013S, p.R1058C, p.R1142X) disrupt COPI integrity and cause both anterograde ER-to-Golgi and retrograde Golgi-to-ER trafficking defects, leading to cGAS/STING-dependent upregulation of type I IFN signaling and ER stress/NF-κB activation, via a distinct mechanism from WD40-domain mutations.","method":"Patient-derived fibroblast trafficking assays, cGAS/STING pathway analysis, ER stress and NF-κB signaling assays in patient-derived primary cell lines, electron microscopy of COPI vesicles","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods in patient-derived cells, novel mechanistic distinction from WD40 mutations, single lab with rigorous controls","pmids":["38175705"],"is_preprint":false},{"year":2025,"finding":"The common HAQ STING allele acts dominantly to dampen COPA-dependent STING signaling; expressing HAQ STING in patient cells rescues the molecular phenotype of COPA syndrome, establishing STING as a critical pathway mediator and HAQ STING as a modifier of COPA syndrome penetrance.","method":"Sequencing of COPA mutation carriers (affected vs. unaffected), exome sequencing, functional rescue experiments expressing HAQ STING in patient cells, STING signaling assays","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic co-segregation combined with functional rescue in patient cells, multiple orthogonal approaches","pmids":["40014299"],"is_preprint":false},{"year":1999,"finding":"The Aspergillus nidulans sodVIC gene encodes an α-COP ortholog (COPA homolog) that is essential for establishing and maintaining polarized hyphal growth; molecular disruption is lethal, and conditional mutants show defects in nuclear division and hyphal extension.","method":"Gene cloning from cosmid library, molecular disruption (lethality), conditional mutant analysis, sequence homology to α-COP","journal":"Fungal genetics and biology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — loss-of-function with specific polarized growth phenotype, single lab, sequence confirms α-COP ortholog","pmids":["10361037"],"is_preprint":false},{"year":2004,"finding":"C-terminal truncation of α-COP in Hansenula polymorpha causes defects in retrograde ER retrieval and intra-Golgi transport, altered trafficking of GPI-anchored protein Gas1p, enhanced secretion of abnormal urokinase forms, and reduction of Golgi Ca2+-ATPase Pmr1p levels; Ca2+ homeostasis defects are suppressed by Pmr1p overexpression, linking COPA-dependent transport to calcium homeostasis.","method":"Truncation mutant analysis, secretion assays, Gas1p trafficking, Pmr1p overexpression suppression, Ca2+ growth requirement assay","journal":"Eukaryotic cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional readouts from defined truncation allele, suppression epistasis, single lab","pmids":["14871936"],"is_preprint":false},{"year":1996,"finding":"The human COPA (HEP-COP) gene encodes a 1224-amino-acid protein with striking homology to yeast α-COP (Ret1p), containing six WD-40 repeats in the N-terminal region, consistent with a role in ER-Golgi membrane transport.","method":"cDNA isolation by RACE, sequence analysis, Northern blot demonstrating ubiquitous expression","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 3 / Weak — sequence-based identification with expression confirmation, no direct functional experiment on the human protein","pmids":["8647451"],"is_preprint":false},{"year":2007,"finding":"Aspergillus nidulans α-COP (CopA) tagged with GFP localizes to putative Golgi equivalents concentrated at hyphal tips; this localization is disrupted by brefeldin A and is independent of the microtubule cytoskeleton.","method":"Live-cell GFP imaging, brefeldin A treatment, dynein mutant and nocodazole (microtubule disruption) experiments","journal":"FEMS microbiology letters","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct live imaging with pharmacological and genetic perturbations, single lab, no functional consequence directly measured","pmids":["17986089"],"is_preprint":false},{"year":2020,"finding":"ADAR2-mediated A-to-I RNA editing of COPA pre-mRNA causes an isoleucine-to-valine substitution at residue 164 (COPAI164V); edited COPAI164V undergoes conformational change making it less stable than wild-type COPAWT; COPAI164V deactivates the PI3K/AKT/mTOR pathway through downregulation of caveolin-1 (CAV1), switching COPA from a tumor-promoting to a tumor-suppressive function.","method":"CRISPR/Cas9 deletion of editing complementary sequence, protein stability assays (cycloheximide chase), PI3K/AKT/mTOR pathway readout, CAV1 expression analysis, cell and mouse xenograft models","journal":"Journal of hepatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR endogenous editing ablation, protein stability and pathway assays, single lab with multiple complementary methods","pmids":["32693003"],"is_preprint":false},{"year":2014,"finding":"COPA is required for cellular entry of arginine-rich cell-penetrating peptides; siRNA knockdown of COPA impairs endosomal entry of poly-arginine peptides, implicating COPA in early endosome maturation.","method":"siRNA library screening, microscopic observation of fluorescent peptide entry, COPA knockdown validation","journal":"PloS one","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single siRNA screen, phenotype (endosomal entry) described without mechanistic follow-up, single lab","pmids":["24489756"],"is_preprint":false},{"year":2016,"finding":"A missense mutation in COPA (arginine-to-cysteine substitution at a completely conserved residue in the WD40 domain) is associated with dominant red coat color in Holstein cattle by disrupting retrograde/cis-Golgi transport, likely causing aberrant MC1R protein or mRNA trafficking within melanocytes, mimicking MC1R loss-of-function.","method":"Genetic association (complete association of COPA variant with Dominant Red phenotype), hair pigment composition analysis, RNA-seq","journal":"PloS one","confidence":"Low","confidence_rationale":"Tier 3 / Weak — genetic association with proposed trafficking mechanism but no direct transport or binding experiment performed, single study","pmids":["26042826"],"is_preprint":false},{"year":2010,"finding":"COPA knockdown induces apoptosis in mesothelioma cells and suppresses tumor growth in a mesothelioma mouse xenograft model, indicating an anti-apoptotic function for COPA in these cancer cells.","method":"Genome-wide siRNA screen, COPA knockdown validation, apoptosis assays, mouse xenograft tumor growth assay","journal":"Genomics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — functional knockdown with tumor phenotype but no molecular mechanism defined for COPA's anti-apoptotic role, single lab","pmids":["20153416"],"is_preprint":false}],"current_model":"COPA (coatomer subunit α) is the cargo-recognition subunit of the COPI vesicular coat that mediates retrograde Golgi-to-ER transport by binding di-lysine sorting signals on cargo proteins through its WD40 domain; disease-causing missense mutations in this domain impair cargo binding and retention, causing defective retrieval of STING from the Golgi to the ER, which leads to ligand-independent STING activation, STING-dependent type I interferon signaling, ER stress, and TH17-skewed autoimmunity (COPA syndrome); structurally, the C-terminal domain of α-COP interlocks with ε-COP via a TPR–β-hairpin interface and contacts the Dsl1 tethering complex, while α-COP also selectively binds PtdIns(3,4,5)P3 and interacts with SMN protein to support neuronal process outgrowth."},"narrative":{"mechanistic_narrative":"COPA encodes the α-COP cargo-recognition subunit of the COPI coatomer, which mediates retrograde Golgi-to-ER transport by selectively binding di-lysine sorting signals through its N-terminal WD40 domain [PMID:9811561, PMID:7490292, PMID:8647451]. α-COP discriminates among distinct di-lysine signals and acts as a selective gate for retrograde cargo retrieval, a function dependent on the integrity of the coatomer complex [PMID:9811561, PMID:7490292]. Within coatomer, the α-COP C-terminal domain interlocks with ε-COP through a TPR–β-hairpin interface, and this heterodimer engages the Dsl1 tethering complex; ε-COP in turn stabilizes α-COP against degradation [PMID:20534429, PMID:9463377]. Disease-causing heterozygous missense mutations in the WD40 domain impair cargo binding and trigger ER stress and TH17-skewed cytokine priming, the basis of COPA syndrome [PMID:25894502]. Mechanistically, α-COP physically interacts with STING, and the SURF4 adapter facilitates COPA-mediated retrieval of STING from the Golgi to the ER; mutant or depleted COPA causes STING to accumulate at the Golgi, driving ligand-independent, STING-dependent type I interferon signaling that is genetically rescued by STING deletion in CopaE241K/+ mice [PMID:32725128, PMID:32725126]. The autoimmune disease is propagated by T cells: mutant Copa in thymic epithelial cells disrupts thymic selection, expanding autoreactive T cells whose adoptive transfer causes interstitial lung disease [PMID:32198142], while the HAQ STING allele dominantly dampens COPA-dependent STING signaling and modifies disease penetrance [PMID:40014299]. Distinct C-terminal domain mutations disrupt coatomer integrity to impair both anterograde and retrograde trafficking, converging on cGAS/STING-dependent interferon and ER stress [PMID:38175705]. Beyond vesicular transport, α-COP binds di-lysine motifs in the SMN protein, an interaction separable from its COPI trafficking role and required for neuronal process outgrowth [PMID:23727837, PMID:26464491].","teleology":[{"year":1995,"claim":"Established that α-COP is functionally required for retrograde retrieval of canonical di-lysine cargo to the ER, defining its role in COPI-mediated transport.","evidence":"ret1-1 α-COP mutant analysis with di-lysine-tagged hybrid cargo and retrograde transport assays in yeast","pmids":["7490292"],"confidence":"High","gaps":["Did not resolve which coatomer subunit directly contacts the di-lysine signal","No structural basis for cargo recognition"]},{"year":1998,"claim":"Defined α-COP as a selective gate that discriminates between distinct di-lysine signals, showing cargo recognition is allele-specific yet dependent on the broader coatomer complex.","evidence":"In vitro GST-fusion binding assays with ret1 coatomer alleles plus in vivo localization in yeast","pmids":["9811561"],"confidence":"High","gaps":["Direct binding site on α-COP not mapped","Mammalian cargo repertoire unaddressed"]},{"year":1998,"claim":"Showed ε-COP stabilizes α-COP, revealing an interdependence within coatomer that protects α-COP from degradation.","evidence":"Yeast high-copy suppressor screen, temperature-sensitive mutants, and α-COP Western blots","pmids":["9463377"],"confidence":"High","gaps":["Structural basis of the α-COP–ε-COP interaction not yet defined","Mechanism of α-COP degradation unknown"]},{"year":1998,"claim":"Identified α-COP as the unique coatomer subunit that binds PtdIns(3,4,5)P3, implicating phosphoinositide lipids in COPI trafficking.","evidence":"Photoaffinity labeling and competitive displacement across COPI subunits","pmids":["9525943"],"confidence":"Medium","gaps":["Single method without reconstitution","Functional consequence of lipid binding in trafficking not demonstrated"]},{"year":2010,"claim":"Provided the structural basis for the α-COP/ε-COP interlock and linked the heterodimer to the Dsl1 tethering machinery.","evidence":"X-ray crystallography of α-COP CTD–ε-COP at 2.9 Å with Dsl1 binding assays","pmids":["20534429"],"confidence":"High","gaps":["Structure of the full coatomer not resolved","Functional role of Dsl1 contact in vivo not tested here"]},{"year":2013,"claim":"Extended α-COP function beyond classical trafficking by showing it binds SMN di-lysine motifs to support neurite outgrowth.","evidence":"Co-IP, SMN di-lysine mutagenesis, and neurite length measurement in NSC-34 cells","pmids":["23727837"],"confidence":"Medium","gaps":["Whether SMN binding requires COPI trafficking not separated here","In vivo relevance not tested"]},{"year":2015,"claim":"Established COPA as the genetic cause of an autoimmune disorder, linking WD40-domain cargo-binding defects to ER stress and TH17 priming.","evidence":"Whole-exome sequencing, cargo binding assays, ER stress assays, and patient CD4+ T cell phenotyping","pmids":["25894502"],"confidence":"High","gaps":["Specific cargo whose mishandling triggers inflammation not yet identified","Mechanism linking ER stress to TH17 skewing unresolved"]},{"year":2015,"claim":"Separated α-COP's SMN-binding neuronal function from its COPI trafficking role using point mutants that abolish SMN binding while preserving Golgi-ER transport.","evidence":"Site-directed mutagenesis, Co-IP, trafficking assays, and neurite outgrowth in NSC-34 cells and zebrafish motor neurons","pmids":["26464491"],"confidence":"High","gaps":["Molecular role of α-COP–SMN complex in axon biology unresolved","Relevance to human motor neuron disease not established"]},{"year":2020,"claim":"Identified STING as the pathogenic cargo of COPA, showing mutant COPA fails to retrieve STING from the Golgi, driving type I interferon signaling.","evidence":"Co-IP of COPA–STING, mutant overexpression, siRNA knockdown, ISG quantification, and STING immunofluorescence","pmids":["32725128"],"confidence":"High","gaps":["Adapter mediating STING recognition not defined in this study","How Golgi STING activates IFN signaling not detailed"]},{"year":2020,"claim":"Provided in vivo proof that STING is the disease driver and identified SURF4 as the adapter facilitating COPA-mediated STING retrieval.","evidence":"CopaE241K/+ × STING-/- genetic epistasis in mice, SURF4 pulldown, and STING transport assays","pmids":["32725126"],"confidence":"High","gaps":["Stoichiometry and structure of COPA–SURF4–STING complex unknown","Whether SURF4 mediates other COPA cargo unaddressed"]},{"year":2020,"claim":"Localized the pathogenic mechanism to T cells, showing mutant Copa in thymic epithelium disrupts thymic selection to generate disease-causing autoreactive T cells.","evidence":"Germline Copa knock-in mouse, thymocyte selection analysis, and adoptive transfer causing interstitial lung disease","pmids":["32198142"],"confidence":"High","gaps":["Link between thymic selection defect and STING pathway not integrated","Cell-intrinsic vs stromal contributions partially resolved"]},{"year":2021,"claim":"Refined the STING activation model, showing disease COPA variants augment stimulus-induced rather than constitutive STING/IFN signaling and cause STING-dependent lung disease in vivo.","evidence":"IFN promoter reporter assays and CopaV242G/+ knock-in mouse with dendritic cell STING activation readouts","pmids":["33982886"],"confidence":"Medium","gaps":["Why activation is inducible rather than constitutive not mechanistically explained","Single lab, two approaches"]},{"year":2024,"claim":"Revealed that C-terminal domain mutations act by a mechanism distinct from WD40 mutations, disrupting coatomer integrity and impairing bidirectional trafficking to drive cGAS/STING and ER stress responses.","evidence":"Patient-derived fibroblast trafficking, cGAS/STING and ER stress assays, and electron microscopy of COPI vesicles","pmids":["38175705"],"confidence":"High","gaps":["How loss of coatomer integrity engages cGAS specifically unclear","Genotype-phenotype correlation across domains not fully mapped"]},{"year":2025,"claim":"Confirmed STING as the critical mediator of COPA syndrome and identified the HAQ STING allele as a dominant penetrance modifier that rescues the molecular phenotype.","evidence":"Carrier sequencing, exome analysis, and functional rescue expressing HAQ STING in patient cells","pmids":["40014299"],"confidence":"High","gaps":["Mechanism by which HAQ STING dampens signaling not detailed","Other genetic modifiers unexplored"]},{"year":null,"claim":"It remains unresolved how COPA mutations mechanistically connect impaired cargo trafficking to the distinct downstream outcomes of STING-driven interferon, ER stress, TH17 skewing, and thymic selection defects within a single unified pathway.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of COPA cargo recognition in mammalian cells","Full repertoire of COPA-dependent cargo beyond STING and SMN undefined","Integration of T-cell and STING mechanisms incomplete"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0038024","term_label":"cargo receptor activity","supporting_discovery_ids":[5,6,1,2]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,2,8]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[7]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[3,4]}],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[1,17,15]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[6,15]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[19]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[5,6,12]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[1,2,6]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[1,2,10,11]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[0,12]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[0,12,13]}],"complexes":["COPI coatomer"],"partners":["COPE","STING1","SURF4","SMN1","DSL1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P53621","full_name":"Coatomer subunit alpha","aliases":["Alpha-coat protein","Alpha-COP","HEP-COP","HEPCOP"],"length_aa":1224,"mass_kda":138.3,"function":"The coatomer is a cytosolic protein complex that binds to dilysine motifs and reversibly associates with Golgi non-clathrin-coated vesicles, which further mediate biosynthetic protein transport from the ER, via the Golgi up to the trans Golgi network. Coatomer complex is required for budding from Golgi membranes, and is essential for the retrograde Golgi-to-ER transport of dilysine-tagged proteins. In mammals, the coatomer can only be recruited by membranes associated to ADP-ribosylation factors (ARFs), which are small GTP-binding proteins; the complex also influences the Golgi structural integrity, as well as the processing, activity, and endocytic recycling of LDL receptors (By similarity) Xenin stimulates exocrine pancreatic secretion. It inhibits pentagastrin-stimulated secretion of acid, to induce exocrine pancreatic secretion and to affect small and large intestinal motility. In the gut, xenin interacts with the neurotensin receptor","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/P53621/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/COPA","classification":"Common Essential","n_dependent_lines":1208,"n_total_lines":1208,"dependency_fraction":1.0},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000122218","cell_line_id":"CID000909","localizations":[{"compartment":"golgi","grade":3},{"compartment":"vesicles","grade":3},{"compartment":"cytoplasmic","grade":1}],"interactors":[{"gene":"COPB1","stoichiometry":10.0},{"gene":"COPG2","stoichiometry":10.0},{"gene":"COPG1","stoichiometry":10.0},{"gene":"COPZ1","stoichiometry":10.0},{"gene":"ARCN1","stoichiometry":10.0},{"gene":"COPB2","stoichiometry":10.0},{"gene":"COPE","stoichiometry":10.0},{"gene":"NOLC1","stoichiometry":10.0},{"gene":"UBE2R2","stoichiometry":4.0},{"gene":"REEP5","stoichiometry":4.0}],"url":"https://opencell.sf.czbiohub.org/target/CID000909","total_profiled":1310},"omim":[{"mim_id":"616414","title":"AUTOINFLAMMATION AND AUTOIMMUNITY, SYSTEMIC, WITH IMMUNE DYSREGULATION 1; AIAISD1","url":"https://www.omim.org/entry/616414"},{"mim_id":"616012","title":"JAGUNAL HOMOLOG 1; JAGN1","url":"https://www.omim.org/entry/616012"},{"mim_id":"606882","title":"ATPase, Cu(2+)-TRANSPORTING, BETA POLYPEPTIDE; ATP7B","url":"https://www.omim.org/entry/606882"},{"mim_id":"605081","title":"CYTOHESIN 3; CYTH3","url":"https://www.omim.org/entry/605081"},{"mim_id":"601924","title":"COATOMER PROTEIN COMPLEX, SUBUNIT ALPHA; COPA","url":"https://www.omim.org/entry/601924"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"},{"location":"Golgi apparatus","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in 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biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/18187034","citation_count":17,"is_preprint":false},{"pmid":"36746811","id":"PMC_36746811","title":"Imaging findings of COPA Syndrome.","date":"2023","source":"Pediatric radiology","url":"https://pubmed.ncbi.nlm.nih.gov/36746811","citation_count":16,"is_preprint":false},{"pmid":"27108337","id":"PMC_27108337","title":"Expression of genes involved in lipid droplet formation (BSCL2, SNAP23 and COPA) during porcine in vitro adipogenesis.","date":"2016","source":"Journal of applied genetics","url":"https://pubmed.ncbi.nlm.nih.gov/27108337","citation_count":16,"is_preprint":false},{"pmid":"31216645","id":"PMC_31216645","title":"CopA Protects Streptococcus suis against Copper Toxicity.","date":"2019","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/31216645","citation_count":15,"is_preprint":false},{"pmid":"19378562","id":"PMC_19378562","title":"The N-terminal soluble domains of Bacillus subtilis CopA exhibit a high affinity and capacity for Cu(I) ions.","date":"2009","source":"Dalton transactions (Cambridge, England : 2003)","url":"https://pubmed.ncbi.nlm.nih.gov/19378562","citation_count":15,"is_preprint":false},{"pmid":"9365789","id":"PMC_9365789","title":"Alpha coat protein COPA (HEP-COP): presence of an Alu repeat in cDNA and identity of the amino terminus to xenin.","date":"1997","source":"Annals of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/9365789","citation_count":14,"is_preprint":false},{"pmid":"9186507","id":"PMC_9186507","title":"Genomic organization and mapping of the human HEP-COP gene (COPA) to 1q.","date":"1997","source":"Cytogenetics and cell genetics","url":"https://pubmed.ncbi.nlm.nih.gov/9186507","citation_count":14,"is_preprint":false},{"pmid":"28403213","id":"PMC_28403213","title":"M-COPA suppresses endolysosomal Kit-Akt oncogenic signalling through inhibiting the secretory pathway in neoplastic mast cells.","date":"2017","source":"PloS 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pathology","url":"https://pubmed.ncbi.nlm.nih.gov/27862834","citation_count":12,"is_preprint":false},{"pmid":"34900872","id":"PMC_34900872","title":"A Novel Mutation c.841C>T in COPA Syndrome of an 11-Year-Old Boy: A Case Report and Short Literature Review.","date":"2021","source":"Frontiers in pediatrics","url":"https://pubmed.ncbi.nlm.nih.gov/34900872","citation_count":12,"is_preprint":false},{"pmid":"40014299","id":"PMC_40014299","title":"The common HAQ STING allele prevents clinical penetrance of COPA syndrome.","date":"2025","source":"The Journal of experimental medicine","url":"https://pubmed.ncbi.nlm.nih.gov/40014299","citation_count":11,"is_preprint":false},{"pmid":"36089219","id":"PMC_36089219","title":"Sequence-based Functional Metagenomics Reveals Novel Natural Diversity of Functional CopA in Environmental Microbiomes.","date":"2022","source":"Genomics, proteomics & bioinformatics","url":"https://pubmed.ncbi.nlm.nih.gov/36089219","citation_count":11,"is_preprint":false},{"pmid":"1720863","id":"PMC_1720863","title":"Regulation of replication of plasmid R1: an analysis of the intergenic region between copA and repA.","date":"1991","source":"Molecular & general genetics : MGG","url":"https://pubmed.ncbi.nlm.nih.gov/1720863","citation_count":11,"is_preprint":false},{"pmid":"14871936","id":"PMC_14871936","title":"C-terminal truncation of alpha-COP affects functioning of secretory organelles and calcium homeostasis in Hansenula polymorpha.","date":"2004","source":"Eukaryotic cell","url":"https://pubmed.ncbi.nlm.nih.gov/14871936","citation_count":10,"is_preprint":false},{"pmid":"27232380","id":"PMC_27232380","title":"The relationship between adipocyte size and the transcript levels of SNAP23, BSCL2 and COPA genes in pigs.","date":"2016","source":"Meat science","url":"https://pubmed.ncbi.nlm.nih.gov/27232380","citation_count":10,"is_preprint":false},{"pmid":"33537146","id":"PMC_33537146","title":"IL-6 receptor blockade for allograft dysfunction after lung transplantation in a patient with COPA syndrome.","date":"2021","source":"Clinical & translational immunology","url":"https://pubmed.ncbi.nlm.nih.gov/33537146","citation_count":10,"is_preprint":false},{"pmid":"22077885","id":"PMC_22077885","title":"Cu(I)- and proton-binding properties of the first N-terminal soluble domain of Bacillus subtilis CopA.","date":"2011","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/22077885","citation_count":10,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":45306,"output_tokens":5413,"usd":0.108557,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13979,"output_tokens":4409,"usd":0.09006,"stage2_stop_reason":"end_turn"},"total_usd":0.198617,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2015,\n      \"finding\": \"COPA (coatomer subunit α) variants in the WD40 domain impair binding to proteins targeted for retrograde Golgi-to-ER transport; expression of mutant COPA results in ER stress and upregulation of cytokines priming for a TH17 response, and patient-derived CD4+ T cells show skewing toward TH17 phenotype.\",\n      \"method\": \"Whole-exome sequencing, binding assays showing impaired cargo binding, ER stress assays, cytokine profiling, T cell phenotyping\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (binding assay, ER stress, T cell skewing) in founding study, subsequently replicated widely\",\n      \"pmids\": [\"25894502\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"COPA physically interacts with STING; mutant COPA (and COPA silencing) causes accumulation of ER-resident STING at the Golgi, consistent with failure of Golgi-to-ER STING retrieval, leading to STING-dependent IFN signaling.\",\n      \"method\": \"Co-immunoprecipitation (COPA–STING interaction), overexpression of mutant COPA, siRNA knockdown, ISG/IFN-α quantification, subcellular localization of STING by immunofluorescence\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal interaction detected, STING localization shift demonstrated, replicated in companion paper same year\",\n      \"pmids\": [\"32725128\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Pathogenic COPA variants cause defective COPI-mediated Golgi-to-ER transport, leading to ligand-independent activation of STING and type I interferon-driven inflammation; SURF4 was identified as an adapter molecule that facilitates COPA-mediated retrieval of STING at the Golgi; activated STING contributes to immune dysregulation rescued in STING-deficient CopaE241K/+ mice.\",\n      \"method\": \"Genetic epistasis (CopaE241K/+ × STING-/- mice), SURF4 identification as COPA–STING adapter (pulldown/Co-IP), STING transport assays, knock-in mouse model with IFN readout\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo epistasis (genetic rescue), adapter protein identified, replicated by companion paper\",\n      \"pmids\": [\"32725126\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Crystal structure of the C-terminal domain (CTD) of α-COP in complex with full-length ε-COP at 2.9 Å resolution reveals that ε-COP adopts a TPR fold that wraps around a β-hairpin of the α-COP CTD, interlocking the two proteins; the α-COP CTD–ε-COP heterodimer directly interacts with the Dsl1 tethering complex.\",\n      \"method\": \"X-ray crystallography, solution biochemistry (heterodimer formation), direct binding assay with Dsl1 tethering complex\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure at 2.9 Å with biochemical validation of heterodimer and Dsl1 interaction, single lab\",\n      \"pmids\": [\"20534429\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"ε-COP (Sec28p) functions to stabilize α-COP; loss of ε-COP causes rapid degradation of α-COP at restrictive temperature and ER trafficking defects; overproduction of ε-COP suppresses α-COP mutant defects by stabilizing α-COP levels.\",\n      \"method\": \"Yeast genetics (high-copy suppressor screen), temperature-sensitive mutant analysis, Western blotting for α-COP levels, carboxypeptidase Y trafficking assay, gel filtration of coatomer\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple genetic and biochemical methods, allele-specific synthetic lethality, single lab\",\n      \"pmids\": [\"9463377\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"α-COP can discriminate between distinct di-lysine signals: ret1-1 mutant α-COP fails to bind the Wbp1p di-lysine signal in vitro but retains binding to the Emp47p di-lysine signal; other coatomer subunits (β'-, γ-, δ-, ζ-COP) are required for binding both di-lysine signals, placing α-COP in a regulatory gating role for selective retrograde transport.\",\n      \"method\": \"In vitro GST-fusion binding assay with coatomer from ret1 alleles, sucrose gradient fractionation, immunofluorescence, epistasis with multiple COP subunit mutants\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro reconstituted binding assay with mutagenesis (ret1 alleles), corroborated by in vivo localization, single lab\",\n      \"pmids\": [\"9811561\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"α-COP is required for ER localization of di-lysine-tagged proteins: a hybrid Ste2p–Emp47p tail protein bearing the Emp47p di-lysine signal is mislocalized to the cell surface in the ret1-1 α-COP mutant; Emp47p cycles between Golgi and ER in a di-lysine-dependent but α-COP-independent manner, establishing that α-COP is needed for retrograde transport of canonical di-lysine cargo.\",\n      \"method\": \"Yeast genetics (ret1-1 mutant), immunofluorescence, retrograde transport assay in sec12 block, subcellular fractionation\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with functional cargo readout, multiple assays, foundational study replicated by later work\",\n      \"pmids\": [\"7490292\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"α-COP specifically binds phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P3] among coatomer subunits; both D-3 and D-5 phosphates are critical for this interaction, suggesting a role for PtdIns(3,4,5)P3 in COPI vesicular trafficking.\",\n      \"method\": \"Photoaffinity labeling with [3H]BZDC-PtdIns(3,4,5)P3 and competitive displacement assays across COPI subunits\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — photoaffinity crosslinking with competition, selective for α-COP, single lab, single method\",\n      \"pmids\": [\"9525943\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Dilysine motifs in exon 2b of SMN protein mediate binding to α-COP (COPA); mutagenesis of the canonical dilysine motifs in SMN abrogates α-COP binding and eliminates the ability of SMN to restore neurite outgrowth in SMN-depleted NSC-34 cells.\",\n      \"method\": \"Co-immunoprecipitation, mutagenesis of SMN dilysine motifs, inducible knockdown cell system, neurite length measurement\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP and mutagenesis with functional readout (neurite length), single lab\",\n      \"pmids\": [\"23727837\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"α-COP binding to SMN is required for neuronal process outgrowth: single amino acid mutants of α-COP that selectively abrogate SMN binding while retaining COPI-mediated Golgi-ER trafficking fail to support neurite outgrowth in NSC-34 cells and zebrafish motor neurons.\",\n      \"method\": \"Site-directed mutagenesis of α-COP, Co-IP to confirm loss of SMN binding, Golgi-ER trafficking assay, neurite length in NSC-34 cells, in vivo zebrafish motor neuron imaging\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mutagenesis separating SMN-binding from COPI trafficking function, replicated in two model systems (cell culture + zebrafish), multiple orthogonal methods\",\n      \"pmids\": [\"26464491\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Mutant Copa in thymic epithelial cells impairs thymic selection of T cells, resulting in an increase in autoreactive T cells and decrease in regulatory T cells in peripheral tissues; adoptive transfer of Copa mutant T cells causes interstitial lung disease, establishing T cells as the pathogenic effector population.\",\n      \"method\": \"Germline Copa knock-in mouse model, thymocyte selection analysis, flow cytometry, adoptive transfer experiment\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo knock-in mouse with adoptive transfer epistasis establishing cellular mechanism, multiple orthogonal readouts, single lab\",\n      \"pmids\": [\"32198142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"COPA V242G (and other disease-causing COPA variants) augments STING-induced type I IFN promoter activity; in CopaV242G/+ dendritic cells the STING pathway is hyperactivated upon stimulation rather than constitutively, leading to increased type I IFN production; interstitial lung disease in CopaV242G/+ mice is STING-dependent.\",\n      \"method\": \"In vitro IFN promoter reporter assay, CopaV242G/+ knock-in mouse model, STING pathway activation assays in dendritic cells, ISG expression analysis\",\n      \"journal\": \"Arthritis & rheumatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro functional assay + in vivo mouse model, single lab, two orthogonal approaches\",\n      \"pmids\": [\"33982886\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Heterozygous mutations in the C-terminal domain (CTD) of COPA (p.C1013S, p.R1058C, p.R1142X) disrupt COPI integrity and cause both anterograde ER-to-Golgi and retrograde Golgi-to-ER trafficking defects, leading to cGAS/STING-dependent upregulation of type I IFN signaling and ER stress/NF-κB activation, via a distinct mechanism from WD40-domain mutations.\",\n      \"method\": \"Patient-derived fibroblast trafficking assays, cGAS/STING pathway analysis, ER stress and NF-κB signaling assays in patient-derived primary cell lines, electron microscopy of COPI vesicles\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods in patient-derived cells, novel mechanistic distinction from WD40 mutations, single lab with rigorous controls\",\n      \"pmids\": [\"38175705\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The common HAQ STING allele acts dominantly to dampen COPA-dependent STING signaling; expressing HAQ STING in patient cells rescues the molecular phenotype of COPA syndrome, establishing STING as a critical pathway mediator and HAQ STING as a modifier of COPA syndrome penetrance.\",\n      \"method\": \"Sequencing of COPA mutation carriers (affected vs. unaffected), exome sequencing, functional rescue experiments expressing HAQ STING in patient cells, STING signaling assays\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic co-segregation combined with functional rescue in patient cells, multiple orthogonal approaches\",\n      \"pmids\": [\"40014299\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"The Aspergillus nidulans sodVIC gene encodes an α-COP ortholog (COPA homolog) that is essential for establishing and maintaining polarized hyphal growth; molecular disruption is lethal, and conditional mutants show defects in nuclear division and hyphal extension.\",\n      \"method\": \"Gene cloning from cosmid library, molecular disruption (lethality), conditional mutant analysis, sequence homology to α-COP\",\n      \"journal\": \"Fungal genetics and biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — loss-of-function with specific polarized growth phenotype, single lab, sequence confirms α-COP ortholog\",\n      \"pmids\": [\"10361037\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"C-terminal truncation of α-COP in Hansenula polymorpha causes defects in retrograde ER retrieval and intra-Golgi transport, altered trafficking of GPI-anchored protein Gas1p, enhanced secretion of abnormal urokinase forms, and reduction of Golgi Ca2+-ATPase Pmr1p levels; Ca2+ homeostasis defects are suppressed by Pmr1p overexpression, linking COPA-dependent transport to calcium homeostasis.\",\n      \"method\": \"Truncation mutant analysis, secretion assays, Gas1p trafficking, Pmr1p overexpression suppression, Ca2+ growth requirement assay\",\n      \"journal\": \"Eukaryotic cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional readouts from defined truncation allele, suppression epistasis, single lab\",\n      \"pmids\": [\"14871936\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"The human COPA (HEP-COP) gene encodes a 1224-amino-acid protein with striking homology to yeast α-COP (Ret1p), containing six WD-40 repeats in the N-terminal region, consistent with a role in ER-Golgi membrane transport.\",\n      \"method\": \"cDNA isolation by RACE, sequence analysis, Northern blot demonstrating ubiquitous expression\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Weak — sequence-based identification with expression confirmation, no direct functional experiment on the human protein\",\n      \"pmids\": [\"8647451\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Aspergillus nidulans α-COP (CopA) tagged with GFP localizes to putative Golgi equivalents concentrated at hyphal tips; this localization is disrupted by brefeldin A and is independent of the microtubule cytoskeleton.\",\n      \"method\": \"Live-cell GFP imaging, brefeldin A treatment, dynein mutant and nocodazole (microtubule disruption) experiments\",\n      \"journal\": \"FEMS microbiology letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct live imaging with pharmacological and genetic perturbations, single lab, no functional consequence directly measured\",\n      \"pmids\": [\"17986089\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"ADAR2-mediated A-to-I RNA editing of COPA pre-mRNA causes an isoleucine-to-valine substitution at residue 164 (COPAI164V); edited COPAI164V undergoes conformational change making it less stable than wild-type COPAWT; COPAI164V deactivates the PI3K/AKT/mTOR pathway through downregulation of caveolin-1 (CAV1), switching COPA from a tumor-promoting to a tumor-suppressive function.\",\n      \"method\": \"CRISPR/Cas9 deletion of editing complementary sequence, protein stability assays (cycloheximide chase), PI3K/AKT/mTOR pathway readout, CAV1 expression analysis, cell and mouse xenograft models\",\n      \"journal\": \"Journal of hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR endogenous editing ablation, protein stability and pathway assays, single lab with multiple complementary methods\",\n      \"pmids\": [\"32693003\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"COPA is required for cellular entry of arginine-rich cell-penetrating peptides; siRNA knockdown of COPA impairs endosomal entry of poly-arginine peptides, implicating COPA in early endosome maturation.\",\n      \"method\": \"siRNA library screening, microscopic observation of fluorescent peptide entry, COPA knockdown validation\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single siRNA screen, phenotype (endosomal entry) described without mechanistic follow-up, single lab\",\n      \"pmids\": [\"24489756\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"A missense mutation in COPA (arginine-to-cysteine substitution at a completely conserved residue in the WD40 domain) is associated with dominant red coat color in Holstein cattle by disrupting retrograde/cis-Golgi transport, likely causing aberrant MC1R protein or mRNA trafficking within melanocytes, mimicking MC1R loss-of-function.\",\n      \"method\": \"Genetic association (complete association of COPA variant with Dominant Red phenotype), hair pigment composition analysis, RNA-seq\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — genetic association with proposed trafficking mechanism but no direct transport or binding experiment performed, single study\",\n      \"pmids\": [\"26042826\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"COPA knockdown induces apoptosis in mesothelioma cells and suppresses tumor growth in a mesothelioma mouse xenograft model, indicating an anti-apoptotic function for COPA in these cancer cells.\",\n      \"method\": \"Genome-wide siRNA screen, COPA knockdown validation, apoptosis assays, mouse xenograft tumor growth assay\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — functional knockdown with tumor phenotype but no molecular mechanism defined for COPA's anti-apoptotic role, single lab\",\n      \"pmids\": [\"20153416\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"COPA (coatomer subunit α) is the cargo-recognition subunit of the COPI vesicular coat that mediates retrograde Golgi-to-ER transport by binding di-lysine sorting signals on cargo proteins through its WD40 domain; disease-causing missense mutations in this domain impair cargo binding and retention, causing defective retrieval of STING from the Golgi to the ER, which leads to ligand-independent STING activation, STING-dependent type I interferon signaling, ER stress, and TH17-skewed autoimmunity (COPA syndrome); structurally, the C-terminal domain of α-COP interlocks with ε-COP via a TPR–β-hairpin interface and contacts the Dsl1 tethering complex, while α-COP also selectively binds PtdIns(3,4,5)P3 and interacts with SMN protein to support neuronal process outgrowth.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"COPA encodes the α-COP cargo-recognition subunit of the COPI coatomer, which mediates retrograde Golgi-to-ER transport by selectively binding di-lysine sorting signals through its N-terminal WD40 domain [#5, #6, #16]. α-COP discriminates among distinct di-lysine signals and acts as a selective gate for retrograde cargo retrieval, a function dependent on the integrity of the coatomer complex [#5, #6]. Within coatomer, the α-COP C-terminal domain interlocks with ε-COP through a TPR–β-hairpin interface, and this heterodimer engages the Dsl1 tethering complex; ε-COP in turn stabilizes α-COP against degradation [#3, #4]. Disease-causing heterozygous missense mutations in the WD40 domain impair cargo binding and trigger ER stress and TH17-skewed cytokine priming, the basis of COPA syndrome [#0]. Mechanistically, α-COP physically interacts with STING, and the SURF4 adapter facilitates COPA-mediated retrieval of STING from the Golgi to the ER; mutant or depleted COPA causes STING to accumulate at the Golgi, driving ligand-independent, STING-dependent type I interferon signaling that is genetically rescued by STING deletion in CopaE241K/+ mice [#1, #2]. The autoimmune disease is propagated by T cells: mutant Copa in thymic epithelial cells disrupts thymic selection, expanding autoreactive T cells whose adoptive transfer causes interstitial lung disease [#10], while the HAQ STING allele dominantly dampens COPA-dependent STING signaling and modifies disease penetrance [#13]. Distinct C-terminal domain mutations disrupt coatomer integrity to impair both anterograde and retrograde trafficking, converging on cGAS/STING-dependent interferon and ER stress [#12]. Beyond vesicular transport, α-COP binds di-lysine motifs in the SMN protein, an interaction separable from its COPI trafficking role and required for neuronal process outgrowth [#8, #9].\",\n  \"teleology\": [\n    {\n      \"year\": 1995,\n      \"claim\": \"Established that α-COP is functionally required for retrograde retrieval of canonical di-lysine cargo to the ER, defining its role in COPI-mediated transport.\",\n      \"evidence\": \"ret1-1 α-COP mutant analysis with di-lysine-tagged hybrid cargo and retrograde transport assays in yeast\",\n      \"pmids\": [\"7490292\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve which coatomer subunit directly contacts the di-lysine signal\", \"No structural basis for cargo recognition\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Defined α-COP as a selective gate that discriminates between distinct di-lysine signals, showing cargo recognition is allele-specific yet dependent on the broader coatomer complex.\",\n      \"evidence\": \"In vitro GST-fusion binding assays with ret1 coatomer alleles plus in vivo localization in yeast\",\n      \"pmids\": [\"9811561\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct binding site on α-COP not mapped\", \"Mammalian cargo repertoire unaddressed\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Showed ε-COP stabilizes α-COP, revealing an interdependence within coatomer that protects α-COP from degradation.\",\n      \"evidence\": \"Yeast high-copy suppressor screen, temperature-sensitive mutants, and α-COP Western blots\",\n      \"pmids\": [\"9463377\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the α-COP–ε-COP interaction not yet defined\", \"Mechanism of α-COP degradation unknown\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Identified α-COP as the unique coatomer subunit that binds PtdIns(3,4,5)P3, implicating phosphoinositide lipids in COPI trafficking.\",\n      \"evidence\": \"Photoaffinity labeling and competitive displacement across COPI subunits\",\n      \"pmids\": [\"9525943\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single method without reconstitution\", \"Functional consequence of lipid binding in trafficking not demonstrated\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Provided the structural basis for the α-COP/ε-COP interlock and linked the heterodimer to the Dsl1 tethering machinery.\",\n      \"evidence\": \"X-ray crystallography of α-COP CTD–ε-COP at 2.9 Å with Dsl1 binding assays\",\n      \"pmids\": [\"20534429\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of the full coatomer not resolved\", \"Functional role of Dsl1 contact in vivo not tested here\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Extended α-COP function beyond classical trafficking by showing it binds SMN di-lysine motifs to support neurite outgrowth.\",\n      \"evidence\": \"Co-IP, SMN di-lysine mutagenesis, and neurite length measurement in NSC-34 cells\",\n      \"pmids\": [\"23727837\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether SMN binding requires COPI trafficking not separated here\", \"In vivo relevance not tested\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Established COPA as the genetic cause of an autoimmune disorder, linking WD40-domain cargo-binding defects to ER stress and TH17 priming.\",\n      \"evidence\": \"Whole-exome sequencing, cargo binding assays, ER stress assays, and patient CD4+ T cell phenotyping\",\n      \"pmids\": [\"25894502\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific cargo whose mishandling triggers inflammation not yet identified\", \"Mechanism linking ER stress to TH17 skewing unresolved\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Separated α-COP's SMN-binding neuronal function from its COPI trafficking role using point mutants that abolish SMN binding while preserving Golgi-ER transport.\",\n      \"evidence\": \"Site-directed mutagenesis, Co-IP, trafficking assays, and neurite outgrowth in NSC-34 cells and zebrafish motor neurons\",\n      \"pmids\": [\"26464491\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular role of α-COP–SMN complex in axon biology unresolved\", \"Relevance to human motor neuron disease not established\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified STING as the pathogenic cargo of COPA, showing mutant COPA fails to retrieve STING from the Golgi, driving type I interferon signaling.\",\n      \"evidence\": \"Co-IP of COPA–STING, mutant overexpression, siRNA knockdown, ISG quantification, and STING immunofluorescence\",\n      \"pmids\": [\"32725128\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Adapter mediating STING recognition not defined in this study\", \"How Golgi STING activates IFN signaling not detailed\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Provided in vivo proof that STING is the disease driver and identified SURF4 as the adapter facilitating COPA-mediated STING retrieval.\",\n      \"evidence\": \"CopaE241K/+ × STING-/- genetic epistasis in mice, SURF4 pulldown, and STING transport assays\",\n      \"pmids\": [\"32725126\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and structure of COPA–SURF4–STING complex unknown\", \"Whether SURF4 mediates other COPA cargo unaddressed\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Localized the pathogenic mechanism to T cells, showing mutant Copa in thymic epithelium disrupts thymic selection to generate disease-causing autoreactive T cells.\",\n      \"evidence\": \"Germline Copa knock-in mouse, thymocyte selection analysis, and adoptive transfer causing interstitial lung disease\",\n      \"pmids\": [\"32198142\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Link between thymic selection defect and STING pathway not integrated\", \"Cell-intrinsic vs stromal contributions partially resolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Refined the STING activation model, showing disease COPA variants augment stimulus-induced rather than constitutive STING/IFN signaling and cause STING-dependent lung disease in vivo.\",\n      \"evidence\": \"IFN promoter reporter assays and CopaV242G/+ knock-in mouse with dendritic cell STING activation readouts\",\n      \"pmids\": [\"33982886\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Why activation is inducible rather than constitutive not mechanistically explained\", \"Single lab, two approaches\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Revealed that C-terminal domain mutations act by a mechanism distinct from WD40 mutations, disrupting coatomer integrity and impairing bidirectional trafficking to drive cGAS/STING and ER stress responses.\",\n      \"evidence\": \"Patient-derived fibroblast trafficking, cGAS/STING and ER stress assays, and electron microscopy of COPI vesicles\",\n      \"pmids\": [\"38175705\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How loss of coatomer integrity engages cGAS specifically unclear\", \"Genotype-phenotype correlation across domains not fully mapped\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Confirmed STING as the critical mediator of COPA syndrome and identified the HAQ STING allele as a dominant penetrance modifier that rescues the molecular phenotype.\",\n      \"evidence\": \"Carrier sequencing, exome analysis, and functional rescue expressing HAQ STING in patient cells\",\n      \"pmids\": [\"40014299\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which HAQ STING dampens signaling not detailed\", \"Other genetic modifiers unexplored\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how COPA mutations mechanistically connect impaired cargo trafficking to the distinct downstream outcomes of STING-driven interferon, ER stress, TH17 skewing, and thymic selection defects within a single unified pathway.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of COPA cargo recognition in mammalian cells\", \"Full repertoire of COPA-dependent cargo beyond STING and SMN undefined\", \"Integration of T-cell and STING mechanisms incomplete\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0038024\", \"supporting_discovery_ids\": [5, 6, 1, 2]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 2, 8]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [7]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [3, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [1, 17, 15]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [6, 15]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [19]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [5, 6, 12]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [1, 2, 6]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [1, 2, 10, 11]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [0, 12]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [0, 12, 13]}\n    ],\n    \"complexes\": [\"COPI coatomer\"],\n    \"partners\": [\"COPE\", \"STING1\", \"SURF4\", \"SMN1\", \"Dsl1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}