{"gene":"ERAP1","run_date":"2026-04-28T17:46:03","timeline":{"discoveries":[{"year":2005,"finding":"ERAP1 and ERAP2 physically associate as heterodimeric complexes in the endoplasmic reticulum and perform concerted trimming of peptide precursors for HLA class I presentation; ERAP1 alone cannot remove certain N-terminal amino acids that ERAP2 trims efficiently, requiring the combined action of both enzymes.","method":"Co-localization in vivo, physical co-immunoprecipitation, in vitro peptide digestion assays, cellular antigen presentation assays","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 1–2 — reciprocal co-IP plus in vitro reconstitution plus functional cellular assay, replicated in multiple experimental systems","pmids":["15908954"],"is_preprint":false},{"year":2002,"finding":"ERAP1 (ARTS-1) binds to the extracellular domain of TNFR1 via yeast two-hybrid and co-immunoprecipitation, and promotes TNFR1 ectodomain shedding; overexpression increases shedding while antisense knockdown decreases it. ARTS-1 displays selective aminopeptidase activity toward nonpolar amino acids but does not itself act as the TNFR1 sheddase.","method":"Yeast two-hybrid, co-immunoprecipitation, overexpression and antisense knockdown in human pulmonary epithelial and endothelial cells, in vitro aminopeptidase activity assay","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods (yeast two-hybrid, co-IP, gain/loss-of-function) in a single study","pmids":["12189246"],"is_preprint":false},{"year":2003,"finding":"ERAP1 (ARTS-1) directly binds membrane-associated IL-6Rα and is required for its constitutive shedding; this regulation requires ARTS-1 catalytic activity, distinguishing it from its non-enzymatic role in TNFR1 shedding.","method":"Reciprocal co-immunoprecipitation, overexpression, ARTS-1 knockout cells (absence of basal shedding), catalytic mutant analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 — reciprocal co-IP plus knockout plus catalytic-activity requirement demonstrated","pmids":["12748171"],"is_preprint":false},{"year":2006,"finding":"ERAP1 is the major enzyme trimming peptide precursors in the endoplasmic reticulum in vivo; genetic knockout in mice shifts the immunodominance hierarchy of viral CD8+ T cell responses by generating or destroying antigenic peptides, demonstrating that ERAP1 trimming activity directly controls peptide-MHC class I complex abundance.","method":"ERAP1 knockout mouse, viral infection model, CD8+ T cell immunodominance assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined cellular phenotype (immunodominance shift), replicated across multiple viral epitopes","pmids":["16754858"],"is_preprint":false},{"year":2006,"finding":"The hypertension-associated Lys528Arg polymorphism of ERAP1 significantly reduces enzymatic aminopeptidase activity; site-directed mutagenesis of Lys528 to various amino acids (Ala, Met, His, Arg) all reduce activity, and molecular modeling places Lys528 near the substrate pocket entrance.","method":"Site-directed mutagenesis, in vitro aminopeptidase activity assay with aminoacyl β-naphthylamide substrates, molecular modeling","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 — in vitro enzymatic assay with mutagenesis of active-site residue","pmids":["16513116"],"is_preprint":false},{"year":2006,"finding":"NUCB2 (nucleobindin 2) binds the ARTS-1 (ERAP1) extracellular domain via a calcium-dependent interaction identified by yeast two-hybrid and co-immunoprecipitation; the NUCB2–ARTS-1 complex associates with TNFR1 and is required for both constitutive release of TNFR1 exosome-like vesicles and inducible proteolytic cleavage of soluble TNFR1 ectodomains.","method":"Yeast two-hybrid, co-immunoprecipitation, confocal microscopy, RNA interference knockdown of NUCB2 and ARTS-1","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — yeast two-hybrid plus co-IP plus RNAi functional phenotype in endothelial cells","pmids":["16407280"],"is_preprint":false},{"year":2008,"finding":"ERAP1 trimming of peptide N-termini is strongly influenced by the internal sequence of the substrate; positively charged or hydrophobic residues at positions distal to the N-terminus alter trimming rates by up to 100-fold for single substitutions and >40,000-fold for multiple substitutions, consistent with ERAP1 recognizing full peptide length via a large negatively charged internal cavity.","method":"Systematic in vitro peptide substrate analysis with collections of peptide variants, molecular modeling of internal cavity","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1 — systematic in vitro biochemical analysis with multiple substrate variants, supported by structural modeling","pmids":["18987748"],"is_preprint":false},{"year":2008,"finding":"RBMX (a heterogeneous nuclear ribonucleoprotein) associates with ERAP1 (ARTS-1) by co-immunoprecipitation, and RNAi knockdown of RBMX reduces both constitutive TNFR1 exosome-like vesicle release and IL-1β-mediated inducible proteolytic cleavage of TNFR1 ectodomains.","method":"Co-immunoprecipitation, RNA interference","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 3 — single Co-IP plus RNAi phenotype, single lab","pmids":["18445477"],"is_preprint":false},{"year":2011,"finding":"X-ray crystal structures of human ERAP1 in open and closed conformations reveal a zinc-metallopeptidase with HEXXH-(X)18-E and GAMEN motifs; structures show extensive domain movements including active-site closure, and the disease-associated K528R mutant shows significantly altered peptide-processing characteristics attributable to impaired interdomain interactions.","method":"X-ray crystallography (open and closed conformations), in vitro peptide-processing assays of K528R mutant","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 — crystal structures plus functional mutagenesis in a single study","pmids":["21508329"],"is_preprint":false},{"year":2011,"finding":"X-ray crystal structure of human ERAP1 bound to bestatin reveals an open conformation with a large interior compartment and an extended groove from the catalytic center that accommodates long peptides; structural and biochemical analyses show that binding of long (but not short) substrates induces conformational change reorienting a key catalytic residue toward the active site, explaining length-dependent trimming activity.","method":"X-ray crystallography (bestatin-bound), biochemical substrate trimming assays","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 — crystal structure plus functional biochemical validation, single rigorous study","pmids":["21478864"],"is_preprint":false},{"year":2011,"finding":"Human cytomegalovirus miR-US4-1 specifically targets and downregulates ERAP1 expression during infection, inhibiting trimming of HCMV-derived peptides and reducing susceptibility of infected cells to HCMV-specific cytotoxic T lymphocytes.","method":"miRNA functional assays, ERAP1 expression measurement, viral peptide trimming assay, CTL cytotoxicity assay","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 — specific miRNA-target validation plus functional peptide trimming and CTL killing assays","pmids":["21892175"],"is_preprint":false},{"year":2013,"finding":"p53 upregulates ERAP1 expression by binding to a cognate p53 response element in the ERAP1 gene, increasing MHC class I surface expression; this mechanism operates in cancer cells and in influenza-infected cells where H1N1 activates p53 leading to ERAP1 upregulation.","method":"ChIP-seq, gene expression analysis, p53 silencing, ERAP1 silencing, MHC class I surface expression measurement","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — ChIP-seq identification of p53-binding site plus loss-of-function experiments in multiple cellular contexts","pmids":["23965983"],"is_preprint":false},{"year":2014,"finding":"ERAP1 and ERAP2 form stabilized heterodimers in which physical interaction with ERAP2 changes basic enzymatic parameters of ERAP1, improving its substrate-binding affinity; the heterodimer produces mature MHC class I epitopes more efficiently than a mixture of the two enzymes unable to dimerize.","method":"Stabilized heterodimer production, in vitro epitope trimming assays comparing heterodimers vs. non-dimerizing enzyme mix, enzymatic kinetics","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 1 — reconstitution of heterodimer plus enzymatic characterization, allosteric mechanism defined","pmids":["24928998"],"is_preprint":false},{"year":2015,"finding":"ERAP1 activity controls the surface expression of HLA-B27 free heavy chains (FHCs) on antigen-presenting cells; silencing or pharmacological inhibition of ERAP1 reduces HLA-B27 FHC surface expression, reduces KIR3DL2 engagement, and suppresses Th17 expansion and IL-17A secretion by ankylosing spondylitis CD4+ T cells.","method":"siRNA knockdown, pharmacological ERAP1 inhibition, flow cytometry, KIR3DL2-reporter cell assay, Th17 intracellular cytokine staining and ELISA","journal":"Annals of the rheumatic diseases","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal loss-of-function methods (siRNA + inhibitor) with specific cellular phenotypes (FHC expression, Th17 response)","pmids":["26130142"],"is_preprint":false},{"year":2015,"finding":"Genetic or pharmacological inhibition of ERAP1 perturbs tumor cell engagement of inhibitory NK cell receptors (KIR by pMHC-I; CD94-NKG2A by nonclassical pMHC-I), reducing protection from NK cell killing; the protective effect can be restored by adding high-affinity peptides, indicating ERAP1 is required to generate high-affinity natural peptide ligands.","method":"ERAP1 inhibition (genetic and pharmacological), NK cell cytotoxicity assay, inhibitory receptor–ligand interaction measurement, high-affinity peptide add-back","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 — genetic KO and pharmacological inhibition with mechanistic rescue experiment, multiple NK receptor classes tested","pmids":["25592150"],"is_preprint":false},{"year":2016,"finding":"ERAP1-ERAP2 heterodimers can trim MHC I-bound precursor peptides to their correct and final lengths (albeit more slowly than free precursors); trimming of MHC I-bound precursors by the heterodimer increases the conformational stability of MHC I/peptide complexes.","method":"ERAP1/ERAP2 heterodimer production, in vitro trimming assays of free and HLA-B*0801-bound N-terminally extended peptides, conformational stability assessment","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 1 — reconstituted heterodimer with in vitro trimming of MHC-bound substrates and stability measurement","pmids":["27514473"],"is_preprint":false},{"year":2016,"finding":"ERAP1 knockdown in monocytic U937 cells expressing HLA-B27 specifically increases cell surface accumulation of HLA-B27 (including disulfide-linked dimers) but has no effect on HLA-B18 or HLA-B51, indicating that ERAP1 activity selectively controls HLA-B27 surface expression and aberrant heavy-chain dimer formation.","method":"ERAP1 siRNA knockdown, immunoprecipitation, isoelectric focusing, immunoblotting, flow cytometry with subtype-specific antibodies, non-reducing PAGE for disulfide-linked dimers","journal":"Molecular immunology","confidence":"High","confidence_rationale":"Tier 2 — clean knockdown with multiple specific detection methods demonstrating allele-specific effect","pmids":["27107845"],"is_preprint":false},{"year":2017,"finding":"HCMV miR-UL112-5p targets the ERAP1 3′ UTR (A variant), reducing ERAP1 expression at RNA and protein levels and inhibiting processing and presentation of the HCMV pp65495–503 peptide to CTLs; a naturally occurring rs17481334 G variant in the ERAP1 3′ UTR prevents miR-UL112-5p binding, preserving ERAP1 expression and CTL killing.","method":"miRNA–3′UTR binding assay, ERAP1 expression measurement (RNA and protein), CTL cytotoxicity assay, genotype analysis of human fibroblasts","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — direct miRNA-target interaction demonstrated plus functional rescue by G-variant, mechanistically specific","pmids":["28746870"],"is_preprint":false},{"year":2019,"finding":"ERAP1 binds the deubiquitylase USP47, displaces USP47-associated βTrCP (the substrate receptor of SCFβTrCP ubiquitin ligase), and promotes βTrCP degradation; this leads to upregulation of Gli transcription factors and enhancement of Hedgehog signaling pathway activity, and genetic or pharmacological ERAP1 inhibition suppresses Hedgehog-dependent tumor growth in vitro and in vivo.","method":"Co-immunoprecipitation (ERAP1–USP47 and USP47–βTrCP interaction), genetic knockdown/knockout, pharmacological inhibition, Gli reporter assay, in vivo tumor model","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP plus in vivo functional validation plus multiple loss-of-function approaches","pmids":["31341163"],"is_preprint":false},{"year":2019,"finding":"Pharmacological inhibition of ERAP1 in A375 melanoma cells alters the qualitative and quantitative composition of the MHC-I immunopeptidome (affecting ~half of 3204 identified peptides) without reducing surface MHC-I expression; inhibition reduces presentation of suboptimal long peptides and increases presentation of high-affinity 9–12-mers, suggesting baseline ERAP1 activity is destructive for many potential epitopes in this line.","method":"ERAP1 inhibitor treatment, MHC-I peptide isolation, LC-MS/MS mass spectrometry of eluted peptides, MHC-I affinity prediction","journal":"Cancer immunology, immunotherapy","confidence":"High","confidence_rationale":"Tier 1–2 — pharmacological inhibition with large-scale immunopeptidomics and quantitative analysis","pmids":["31222486"],"is_preprint":false},{"year":2019,"finding":"X-ray crystallographic structures of HLA-B*0801 bound to N-terminally extended 10–20-mer precursor peptides show that residue extensions protrude out of the A pocket while the peptide core adopts a canonical conformation; ERAP1-mediated trimming of MHC I-bound peptides requires a minimal length of 14 amino acids, and HLA-B*0801 residue 62 is critical for opening the A pocket to accommodate the extension.","method":"X-ray crystallography (1.40–1.65 Å resolution), thermostability assays, in vitro ERAP1 trimming assay of MHC I-bound peptides","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — high-resolution crystal structures plus biochemical trimming assays with defined minimal-length requirement","pmids":["31601650"],"is_preprint":false},{"year":2021,"finding":"ERAP1 conformational states in solution (open and closed) occur during the catalytic cycle and are promoted by binding of long peptide substrates; allosteric activators shift the enzyme toward closed conformation, inhibitors toward open; structural reconfigurations of the active site are physically linked to domain closure, providing the mechanistic basis for allosteric regulation and explaining the Lys/Arg528 polymorphism disease association.","method":"Small-angle X-ray scattering (SAXS) in solution, X-ray crystallography, chemical crosslinking to localize C-terminal binding sites, enzymatic assays with substrates/allosteric modulators/inhibitors","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 — multiple structural methods (SAXS + crystallography + crosslinking) plus enzymatic validation, mechanistic model validated","pmids":["34489420"],"is_preprint":false},{"year":2021,"finding":"In psoriasis, ERAP1 generates the causative melanocyte autoantigen by trimming N-terminally extended peptide precursors to the length required for presentation by HLA-C*06:02; an ERAP1 risk haplotype produces the autoantigen more efficiently and increases HLA-C expression and stimulation of a psoriatic autoreactive TCR. ERAP1 knockout significantly reduces cell-surface HLA-C expression more than total HLA class I.","method":"Genetically modified cell lines, TCR activation assay with autoreactive psoriatic TCR, ERAP1 knockout, in vitro peptide trimming assays, flow cytometry for HLA-C surface expression","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — multiple genetically defined cell lines with functional TCR activation and ERAP1 KO rescue experiments","pmids":["34580106"],"is_preprint":false},{"year":2022,"finding":"ERAP1 functions as an inflammation-induced hepatokine; hepatically secreted ERAP1 interacts with β2 adrenergic receptor (ADRB2) in skeletal muscle, reduces ADRB2 expression by decreasing USP33-mediated deubiquitination, and thereby impairs ADRB2-stimulated insulin signaling, attenuating skeletal muscle insulin sensitivity.","method":"Hepatic overexpression and knockdown in vivo (HFD mice), serum ERAP1 measurement, co-immunoprecipitation (ERAP1–ADRB2 interaction), ubiquitination assay (USP33-mediated deubiquitination), insulin signaling assays in skeletal muscle","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 — in vivo gain/loss-of-function with mechanistic co-IP and deubiquitination biochemistry","pmids":["35192681"],"is_preprint":false},{"year":2000,"finding":"ERAP1 (PILS-AP) contains the HEXXH(X)18E zinc-binding motif characteristic of M1 family aminopeptidases and a signal sequence directing it to intracellular vesicles; recombinant protein shows leucine-specific (and lesser methionine) aminopeptidase activity inhibited by metal chelators, but insensitive to puromycin.","method":"cDNA cloning, GFP fusion protein localization in COS-7 and BHK cells, recombinant expression in Sf9 insect cells, aminoacyl β-naphthylamide substrate hydrolysis assays, inhibitor profiling","journal":"European journal of biochemistry","confidence":"High","confidence_rationale":"Tier 1 — recombinant protein enzymatic assay plus subcellular localization with GFP fusion","pmids":["10824104"],"is_preprint":false}],"current_model":"ERAP1 is an ER-resident zinc metallopeptidase (M1 family) that acts as a 'molecular ruler,' trimming N-terminally extended peptide precursors to 8–10-mers for loading onto MHC class I molecules via a conformational cycle (open→closed) triggered by long-peptide binding; it forms allosterically enhanced heterodimers with ERAP2, directly controls the immunopeptidome composition and immunodominance hierarchies for CD8+ T and NK cell responses, promotes TNFR1 and IL-6Rα ectodomain shedding through direct receptor binding, participates in Hedgehog signaling by binding USP47 and destabilizing βTrCP, and acts as an inflammation-induced hepatokine that impairs skeletal muscle insulin sensitivity by binding ADRB2 and inhibiting its USP33-mediated deubiquitination."},"narrative":{"teleology":[{"year":2000,"claim":"Identification of ERAP1 as a signal-peptide-bearing M1 zinc metallopeptidase with leucine-preferring aminopeptidase activity established its catalytic identity and vesicular localization, setting the stage for functional studies.","evidence":"cDNA cloning, recombinant enzyme assays with aminoacyl β-naphthylamide substrates, and GFP-fusion localization in COS-7/BHK cells","pmids":["10824104"],"confidence":"High","gaps":["Physiological substrates in vivo unknown","No structural information available","Precise ER versus other vesicular compartment localization not distinguished"]},{"year":2002,"claim":"Discovery that ERAP1 physically binds TNFR1 and promotes its ectodomain shedding revealed an unexpected non-peptide-trimming function — receptor processing at the cell surface — and showed that this shedding role was independent of ERAP1's own proteolytic activity.","evidence":"Yeast two-hybrid, co-IP, overexpression and antisense knockdown in pulmonary epithelial/endothelial cells","pmids":["12189246"],"confidence":"High","gaps":["Identity of the actual sheddase recruited by ERAP1 unknown","Whether ERAP1 exits the ER to reach TNFR1 at the surface not resolved"]},{"year":2003,"claim":"Demonstration that ERAP1 binds IL-6Rα and is required for its constitutive shedding — and that this shedding requires ERAP1 catalytic activity — distinguished mechanistically between ERAP1's enzymatic and non-enzymatic receptor-shedding roles.","evidence":"Reciprocal co-IP, ERAP1-null cells showing loss of basal shedding, catalytic-dead mutant analysis","pmids":["12748171"],"confidence":"High","gaps":["Whether ERAP1 directly cleaves IL-6Rα or activates another sheddase not determined","Structural basis of the ERAP1–IL-6Rα interaction unknown"]},{"year":2005,"claim":"Discovery that ERAP1 and ERAP2 form ER-resident heterodimers performing concerted peptide trimming — with ERAP2 cleaving N-terminal residues refractory to ERAP1 — explained how the full range of MHC I precursors are processed.","evidence":"Co-IP, co-localization, in vitro peptide digestion, cellular antigen presentation assays","pmids":["15908954"],"confidence":"High","gaps":["Stoichiometry and structural architecture of the heterodimer not resolved","Allosteric regulation between subunits not yet characterized"]},{"year":2006,"claim":"Genetic knockout of ERAP1 in mice proved it is the major ER peptide trimming enzyme in vivo, directly controlling peptide–MHC I complex abundance and shifting CD8+ T cell immunodominance hierarchies during viral infection.","evidence":"ERAP1 knockout mouse, viral infection models, CD8+ T cell immunodominance assays across multiple epitopes","pmids":["16754858"],"confidence":"High","gaps":["Contribution of ERAP2 versus ERAP1 in vivo not separated (mice lack ERAP2)","Whether ERAP1 loss also affects non-classical MHC I presentation not examined"]},{"year":2006,"claim":"Characterization of the K528R disease-associated polymorphism as catalytically impaired, with K528 positioned near the substrate pocket, provided the first genotype-to-enzymatic-activity link and a rationale for disease associations.","evidence":"Site-directed mutagenesis panel, in vitro aminopeptidase assays, molecular modeling","pmids":["16513116"],"confidence":"High","gaps":["No crystal structure to confirm K528 positioning","Effect on peptide trimming in cells not tested"]},{"year":2008,"claim":"Systematic substrate profiling revealed that ERAP1 trimming rates depend on internal peptide sequence (up to 40,000-fold variation), consistent with a large internal cavity sensing full peptide length — the 'molecular ruler' concept.","evidence":"In vitro trimming of systematically varied peptide collections, modeling of internal cavity","pmids":["18987748"],"confidence":"High","gaps":["No direct structural evidence for cavity–peptide contacts","Molecular ruler mechanism not validated in a cellular context"]},{"year":2011,"claim":"Crystal structures of ERAP1 in open and closed conformations, and bound to bestatin, revealed the structural basis for length-dependent trimming: long-substrate binding induces domain closure that repositions a catalytic residue, explaining how the enzyme preferentially trims long precursors and how K528R disrupts interdomain interactions.","evidence":"X-ray crystallography (multiple conformations, bestatin-bound), enzymatic assays with K528R mutant","pmids":["21508329","21478864"],"confidence":"High","gaps":["No structure of ERAP1 bound to a native peptide substrate","Conformational dynamics during the catalytic cycle not captured in crystals"]},{"year":2011,"claim":"HCMV miR-US4-1 was shown to specifically target ERAP1 mRNA, reducing peptide trimming and CTL killing of infected cells — establishing viral immune evasion through ERAP1 suppression as a pathogenically relevant strategy.","evidence":"miRNA functional assays, ERAP1 expression measurement, viral peptide trimming and CTL cytotoxicity assays","pmids":["21892175"],"confidence":"High","gaps":["Whether other herpesviruses use analogous miRNA strategies unknown","Contribution relative to other HCMV immune evasion genes not quantified"]},{"year":2014,"claim":"Reconstitution of stabilized ERAP1–ERAP2 heterodimers demonstrated allosteric enhancement: physical interaction with ERAP2 improved ERAP1 substrate-binding affinity and produced mature epitopes more efficiently than a non-dimerizing enzyme mixture.","evidence":"Stabilized heterodimer production, comparative enzyme kinetics, in vitro epitope trimming","pmids":["24928998"],"confidence":"High","gaps":["Structural basis of allosteric communication between ERAP1 and ERAP2 not resolved","In vivo relevance of allosteric enhancement not yet demonstrated"]},{"year":2015,"claim":"ERAP1 activity was shown to control HLA-B27 free heavy chain surface expression, KIR3DL2 engagement, and Th17 expansion in ankylosing spondylitis, providing a direct mechanistic link between ERAP1 peptide trimming and autoimmune pathology.","evidence":"siRNA knockdown and pharmacological ERAP1 inhibition in antigen-presenting cells, KIR3DL2 reporter assays, Th17 cytokine measurements from AS patient cells","pmids":["26130142"],"confidence":"High","gaps":["Which specific peptides drive HLA-B27 FHC formation not identified","Whether ERAP1 inhibition is therapeutic in vivo for AS not tested"]},{"year":2016,"claim":"Demonstration that ERAP1–ERAP2 heterodimers trim MHC I-bound precursor peptides (not only free peptides) and improve pMHC stability expanded the functional scope of ERAP1 trimming beyond the free-peptide pool.","evidence":"In vitro trimming of HLA-B*0801-bound N-terminally extended peptides, conformational stability assays","pmids":["27514473"],"confidence":"High","gaps":["Physiological relevance of MHC-bound trimming versus free-peptide trimming not quantified in cells","Whether tapasin or other PLC components modulate on-MHC trimming unknown"]},{"year":2019,"claim":"ERAP1 was found to bind USP47, displacing βTrCP from USP47 and promoting βTrCP degradation, thereby upregulating Gli transcription factors and Hedgehog signaling — revealing a non-canonical signaling role outside the antigen-processing pathway.","evidence":"Reciprocal co-IP, genetic knockdown/knockout, pharmacological inhibition, Gli reporter assays, in vivo tumor xenograft model","pmids":["31341163"],"confidence":"High","gaps":["Whether ERAP1's aminopeptidase activity is required for USP47 binding not determined","Structural basis of ERAP1–USP47 interaction unknown"]},{"year":2019,"claim":"Immunopeptidomics upon pharmacological ERAP1 inhibition revealed that baseline ERAP1 activity is destructive for many potential epitopes, not only generative — shifting the view from ERAP1 as a simple epitope producer to a dual editor of the immunopeptidome.","evidence":"ERAP1 inhibitor treatment of A375 melanoma, LC-MS/MS immunopeptidome profiling of ~3204 peptides","pmids":["31222486"],"confidence":"High","gaps":["Whether destructive trimming is cell-type or allele dependent not addressed","Functional immunogenicity of the altered peptidome not tested with T cells"]},{"year":2021,"claim":"Solution SAXS and crystallography confirmed that open-to-closed conformational transitions occur during catalysis in solution, are driven by long-peptide binding, and are modulated by allosteric activators/inhibitors — unifying the structural and biochemical molecular-ruler model.","evidence":"SAXS, X-ray crystallography, chemical crosslinking, enzymatic assays with allosteric modulators","pmids":["34489420"],"confidence":"High","gaps":["Full catalytic cycle dynamics at single-molecule resolution not captured","How heterodimer formation with ERAP2 modulates conformational dynamics unknown"]},{"year":2021,"claim":"In psoriasis, ERAP1 was shown to generate the causative melanocyte autoantigen by trimming precursors for HLA-C*06:02 presentation, with a risk haplotype producing the autoantigen more efficiently — directly connecting ERAP1 genotype to autoimmune epitope generation.","evidence":"ERAP1 KO and genetically defined cell lines, autoreactive psoriatic TCR activation assay, in vitro peptide trimming, flow cytometry","pmids":["34580106"],"confidence":"High","gaps":["Whether ERAP1 inhibition is therapeutic in psoriasis in vivo unknown","Full set of ERAP1-dependent autoantigens in psoriasis not mapped"]},{"year":2022,"claim":"Discovery of ERAP1 as a secreted hepatokine that binds ADRB2 in skeletal muscle and impairs insulin signaling by inhibiting USP33-mediated deubiquitination of ADRB2 revealed a systemic metabolic role entirely independent of antigen processing.","evidence":"Hepatic overexpression/knockdown in HFD mice, serum ERAP1 measurement, co-IP of ERAP1–ADRB2, ubiquitination/deubiquitination assays, insulin signaling readouts in skeletal muscle","pmids":["35192681"],"confidence":"High","gaps":["How ERAP1 is secreted from the ER lumen to serum not elucidated","Whether the hepatokine function requires ERAP1 aminopeptidase activity unknown","Relevance in human metabolic disease not confirmed"]},{"year":null,"claim":"Key unresolved questions include the structural basis of ERAP1–ERAP2 heterodimer allostery, how ERAP1 exits the ER for its receptor-shedding and hepatokine roles, whether aminopeptidase activity is required for all non-canonical functions (Hedgehog, ADRB2), and whether ERAP1 inhibition can be therapeutically exploited in autoimmunity or cancer.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structure of ERAP1–ERAP2 heterodimer available","ER-exit or secretion mechanism undefined","Therapeutic efficacy of ERAP1 modulation not tested in clinical studies"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,3,6,9,12,15,19,20,22,24]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[4,6,24]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[18,23]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0,24]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[23]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,3,10,11,13,14,17,19,22]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[6,8,9,15,20,21]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,2,18,23]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[13,16,22]}],"complexes":["ERAP1–ERAP2 heterodimer","NUCB2–ERAP1–TNFR1 complex"],"partners":["ERAP2","TNFRSF1A","IL6R","NUCB2","USP47","ADRB2","RBMX"],"other_free_text":[]},"mechanistic_narrative":"ERAP1 is an endoplasmic reticulum-resident M1-family zinc metallopeptidase that trims N-terminally extended peptide precursors to optimal 8–10-mer lengths for loading onto MHC class I molecules, thereby shaping the immunopeptidome and controlling CD8+ T cell immunodominance hierarchies and NK cell recognition [PMID:16754858, PMID:31222486]. It operates via a conformational open-to-closed catalytic cycle triggered by long-peptide binding, with the internal cavity acting as a molecular ruler that senses substrate length; disease-associated polymorphisms such as K528R impair this interdomain mechanism [PMID:21478864, PMID:34489420]. ERAP1 forms allosterically enhanced heterodimers with ERAP2 that improve substrate-binding affinity and generate mature epitopes more efficiently, and these heterodimers can also trim MHC I-bound precursors [PMID:24928998, PMID:27514473]. Beyond antigen processing, ERAP1 promotes TNFR1 and IL-6Rα ectodomain shedding through direct receptor binding [PMID:12189246, PMID:12748171], enhances Hedgehog signaling by binding USP47 and destabilizing βTrCP [PMID:31341163], and acts as a hepatokine that impairs skeletal muscle insulin sensitivity by binding ADRB2 and inhibiting USP33-mediated deubiquitination [PMID:35192681]."},"prefetch_data":{"uniprot":{"accession":"Q9NZ08","full_name":"Endoplasmic reticulum aminopeptidase 1","aliases":["ARTS-1","Adipocyte-derived leucine aminopeptidase","A-LAP","Aminopeptidase PILS","Puromycin-insensitive leucyl-specific aminopeptidase","PILS-AP","Type 1 tumor necrosis factor receptor shedding aminopeptidase regulator"],"length_aa":941,"mass_kda":107.2,"function":"Aminopeptidase that plays a central role in peptide trimming, a step required for the generation of most HLA class I-binding peptides. Peptide trimming is essential to customize longer precursor peptides to fit them to the correct length required for presentation on MHC class I molecules. Strongly prefers substrates 9-16 residues long. Rapidly degrades 13-mer to a 9-mer and then stops. Preferentially hydrolyzes the residue Leu and peptides with a hydrophobic C-terminus, while it has weak activity toward peptides with charged C-terminus. May play a role in the inactivation of peptide hormones. May be involved in the regulation of blood pressure through the inactivation of angiotensin II and/or the generation of bradykinin in the kidney","subcellular_location":"Endoplasmic reticulum membrane","url":"https://www.uniprot.org/uniprotkb/Q9NZ08/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ERAP1","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ERAP1","total_profiled":1310},"omim":[{"mim_id":"609497","title":"ENDOPLASMIC RETICULUM AMINOPEPTIDASE 2; ERAP2","url":"https://www.omim.org/entry/609497"},{"mim_id":"609423","title":"HUMAN IMMUNODEFICIENCY VIRUS TYPE 1, SUSCEPTIBILITY TO","url":"https://www.omim.org/entry/609423"},{"mim_id":"606832","title":"ENDOPLASMIC 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and ERAP2 Enzymes: A Protective Shield for RAS against COVID-19?","date":"2021","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/33567739","citation_count":22,"is_preprint":false},{"pmid":"31092671","id":"PMC_31092671","title":"Redundancy and Complementarity between ERAP1 and ERAP2 Revealed by their Effects on the Behcet's Disease-associated HLA-B*51 Peptidome.","date":"2019","source":"Molecular & cellular proteomics : MCP","url":"https://pubmed.ncbi.nlm.nih.gov/31092671","citation_count":22,"is_preprint":false},{"pmid":"29632046","id":"PMC_29632046","title":"Ranking the Contribution of Ankylosing Spondylitis-associated Endoplasmic Reticulum Aminopeptidase 1 (ERAP1) Polymorphisms to Shaping the HLA-B*27 Peptidome.","date":"2018","source":"Molecular & cellular proteomics : MCP","url":"https://pubmed.ncbi.nlm.nih.gov/29632046","citation_count":22,"is_preprint":false},{"pmid":"26393469","id":"PMC_26393469","title":"Association of ERAP1 Gene Polymorphisms With Behçet's Disease in Han Chinese.","date":"2015","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/26393469","citation_count":21,"is_preprint":false},{"pmid":"24223975","id":"PMC_24223975","title":"Concerted in vitro trimming of viral HLA-B27-restricted ligands by human ERAP1 and ERAP2 aminopeptidases.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24223975","citation_count":21,"is_preprint":false},{"pmid":"27390066","id":"PMC_27390066","title":"Discovery of potent and selective inhibitors of human aminopeptidases ERAP1 and ERAP2 by screening libraries of phosphorus-containing amino acid and dipeptide analogues.","date":"2016","source":"Bioorganic & medicinal chemistry letters","url":"https://pubmed.ncbi.nlm.nih.gov/27390066","citation_count":21,"is_preprint":false},{"pmid":"28867178","id":"PMC_28867178","title":"Associations of ERAP1 coding variants and domain specific interaction with HLA-C∗06 in the early onset psoriasis patients of India.","date":"2017","source":"Human immunology","url":"https://pubmed.ncbi.nlm.nih.gov/28867178","citation_count":20,"is_preprint":false},{"pmid":"30794838","id":"PMC_30794838","title":"ERAP1-ERAP2 haplotypes are associated with ankylosing spondylitis in Polish patients.","date":"2019","source":"Human immunology","url":"https://pubmed.ncbi.nlm.nih.gov/30794838","citation_count":20,"is_preprint":false},{"pmid":"28083613","id":"PMC_28083613","title":"Single Nucleotide Polymorphisms of the ERAP1 Gene and Risk of NSCLC: A Comparison of Genetically Distant Populations, Chinese and Caucasian.","date":"2017","source":"Archivum immunologiae et therapiae experimentalis","url":"https://pubmed.ncbi.nlm.nih.gov/28083613","citation_count":20,"is_preprint":false},{"pmid":"27107845","id":"PMC_27107845","title":"ERAP1 reduces accumulation of aberrant and disulfide-linked forms of HLA-B27 on the cell surface.","date":"2016","source":"Molecular immunology","url":"https://pubmed.ncbi.nlm.nih.gov/27107845","citation_count":19,"is_preprint":false},{"pmid":"23864143","id":"PMC_23864143","title":"A polymorphism in ERAP1 is associated with susceptibility to ankylosing spondylitis in a Turkish population.","date":"2013","source":"Rheumatology international","url":"https://pubmed.ncbi.nlm.nih.gov/23864143","citation_count":19,"is_preprint":false},{"pmid":"30769005","id":"PMC_30769005","title":"ERAP1 allotypes shape the epitope repertoire of virus-specific CD8+ T cell responses in acute hepatitis C virus infection.","date":"2019","source":"Journal of hepatology","url":"https://pubmed.ncbi.nlm.nih.gov/30769005","citation_count":19,"is_preprint":false},{"pmid":"34727153","id":"PMC_34727153","title":"ERAP1, ERAP2, and Two Copies of HLA-Aw19 Alleles Increase the Risk for Birdshot Chorioretinopathy in HLA-A29 Carriers.","date":"2021","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/34727153","citation_count":18,"is_preprint":false},{"pmid":"36203608","id":"PMC_36203608","title":"The emerging multifunctional roles of ERAP1, ERAP2 and IRAP between antigen processing and renin-angiotensin system modulation.","date":"2022","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/36203608","citation_count":17,"is_preprint":false},{"pmid":"25087231","id":"PMC_25087231","title":"ERAP1 functions override the intrinsic selection of specific antigens as immunodominant peptides, thereby altering the potency of antigen-specific cytolytic and effector memory T-cell responses.","date":"2014","source":"International immunology","url":"https://pubmed.ncbi.nlm.nih.gov/25087231","citation_count":17,"is_preprint":false},{"pmid":"30412714","id":"PMC_30412714","title":"Association analysis of ERAP1 gene single nucleotide polymorphism in susceptibility to ankylosing spondylitis in Iranian population.","date":"2018","source":"Immunology letters","url":"https://pubmed.ncbi.nlm.nih.gov/30412714","citation_count":17,"is_preprint":false},{"pmid":"35192681","id":"PMC_35192681","title":"Hepatokine ERAP1 Disturbs Skeletal Muscle Insulin Sensitivity Via Inhibiting USP33-Mediated ADRB2 Deubiquitination.","date":"2022","source":"Diabetes","url":"https://pubmed.ncbi.nlm.nih.gov/35192681","citation_count":17,"is_preprint":false},{"pmid":"33651148","id":"PMC_33651148","title":"Potentially functional variants of ERAP1, PSMF1 and NCF2 in the MHC-I-related pathway predict non-small cell lung cancer survival.","date":"2021","source":"Cancer immunology, immunotherapy : CII","url":"https://pubmed.ncbi.nlm.nih.gov/33651148","citation_count":17,"is_preprint":false},{"pmid":"33762660","id":"PMC_33762660","title":"Genetic association of ERAP1 and ERAP2 with eclampsia and preeclampsia in northeastern Brazilian women.","date":"2021","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/33762660","citation_count":16,"is_preprint":false},{"pmid":"21833528","id":"PMC_21833528","title":"Susceptibility to ankylosing spondylitis: evidence for the role of ERAP1, TGFb1 and TLR9 gene polymorphisms.","date":"2011","source":"Rheumatology international","url":"https://pubmed.ncbi.nlm.nih.gov/21833528","citation_count":16,"is_preprint":false},{"pmid":"23800305","id":"PMC_23800305","title":"Functional variants of ERAP1 gene are associated with HLA-B27 positive spondyloarthritis.","date":"2013","source":"Tissue antigens","url":"https://pubmed.ncbi.nlm.nih.gov/23800305","citation_count":16,"is_preprint":false},{"pmid":"23123136","id":"PMC_23123136","title":"Association of ankylosing spondylitis with HLA-B27 and ERAP1: pathogenic role of antigenic peptide.","date":"2012","source":"Medical hypotheses","url":"https://pubmed.ncbi.nlm.nih.gov/23123136","citation_count":16,"is_preprint":false},{"pmid":"29480940","id":"PMC_29480940","title":"ERAP1/ERAP2 and RUNX3 polymorphisms are not associated with ankylosing spondylitis susceptibility in Chinese Han.","date":"2018","source":"Clinical and experimental immunology","url":"https://pubmed.ncbi.nlm.nih.gov/29480940","citation_count":16,"is_preprint":false},{"pmid":"29278768","id":"PMC_29278768","title":"Association of polymorphisms in ERAP1 and risk of ankylosing spondylitis in a Chinese population.","date":"2017","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/29278768","citation_count":15,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":51664,"output_tokens":6166,"usd":0.123741},"stage2":{"model":"claude-opus-4-6","input_tokens":9838,"output_tokens":4389,"usd":0.238372},"total_usd":0.362113,"stage1_batch_id":"msgbatch_0118RScg3WGaGkaZRtWZbtce","stage2_batch_id":"msgbatch_01Cpfzvtbj42aqp5oYZ5Te2s","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2005,\n      \"finding\": \"ERAP1 and ERAP2 physically associate as heterodimeric complexes in the endoplasmic reticulum and perform concerted trimming of peptide precursors for HLA class I presentation; ERAP1 alone cannot remove certain N-terminal amino acids that ERAP2 trims efficiently, requiring the combined action of both enzymes.\",\n      \"method\": \"Co-localization in vivo, physical co-immunoprecipitation, in vitro peptide digestion assays, cellular antigen presentation assays\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — reciprocal co-IP plus in vitro reconstitution plus functional cellular assay, replicated in multiple experimental systems\",\n      \"pmids\": [\"15908954\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"ERAP1 (ARTS-1) binds to the extracellular domain of TNFR1 via yeast two-hybrid and co-immunoprecipitation, and promotes TNFR1 ectodomain shedding; overexpression increases shedding while antisense knockdown decreases it. ARTS-1 displays selective aminopeptidase activity toward nonpolar amino acids but does not itself act as the TNFR1 sheddase.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, overexpression and antisense knockdown in human pulmonary epithelial and endothelial cells, in vitro aminopeptidase activity assay\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods (yeast two-hybrid, co-IP, gain/loss-of-function) in a single study\",\n      \"pmids\": [\"12189246\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"ERAP1 (ARTS-1) directly binds membrane-associated IL-6Rα and is required for its constitutive shedding; this regulation requires ARTS-1 catalytic activity, distinguishing it from its non-enzymatic role in TNFR1 shedding.\",\n      \"method\": \"Reciprocal co-immunoprecipitation, overexpression, ARTS-1 knockout cells (absence of basal shedding), catalytic mutant analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — reciprocal co-IP plus knockout plus catalytic-activity requirement demonstrated\",\n      \"pmids\": [\"12748171\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"ERAP1 is the major enzyme trimming peptide precursors in the endoplasmic reticulum in vivo; genetic knockout in mice shifts the immunodominance hierarchy of viral CD8+ T cell responses by generating or destroying antigenic peptides, demonstrating that ERAP1 trimming activity directly controls peptide-MHC class I complex abundance.\",\n      \"method\": \"ERAP1 knockout mouse, viral infection model, CD8+ T cell immunodominance assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined cellular phenotype (immunodominance shift), replicated across multiple viral epitopes\",\n      \"pmids\": [\"16754858\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The hypertension-associated Lys528Arg polymorphism of ERAP1 significantly reduces enzymatic aminopeptidase activity; site-directed mutagenesis of Lys528 to various amino acids (Ala, Met, His, Arg) all reduce activity, and molecular modeling places Lys528 near the substrate pocket entrance.\",\n      \"method\": \"Site-directed mutagenesis, in vitro aminopeptidase activity assay with aminoacyl β-naphthylamide substrates, molecular modeling\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro enzymatic assay with mutagenesis of active-site residue\",\n      \"pmids\": [\"16513116\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"NUCB2 (nucleobindin 2) binds the ARTS-1 (ERAP1) extracellular domain via a calcium-dependent interaction identified by yeast two-hybrid and co-immunoprecipitation; the NUCB2–ARTS-1 complex associates with TNFR1 and is required for both constitutive release of TNFR1 exosome-like vesicles and inducible proteolytic cleavage of soluble TNFR1 ectodomains.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, confocal microscopy, RNA interference knockdown of NUCB2 and ARTS-1\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — yeast two-hybrid plus co-IP plus RNAi functional phenotype in endothelial cells\",\n      \"pmids\": [\"16407280\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"ERAP1 trimming of peptide N-termini is strongly influenced by the internal sequence of the substrate; positively charged or hydrophobic residues at positions distal to the N-terminus alter trimming rates by up to 100-fold for single substitutions and >40,000-fold for multiple substitutions, consistent with ERAP1 recognizing full peptide length via a large negatively charged internal cavity.\",\n      \"method\": \"Systematic in vitro peptide substrate analysis with collections of peptide variants, molecular modeling of internal cavity\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic in vitro biochemical analysis with multiple substrate variants, supported by structural modeling\",\n      \"pmids\": [\"18987748\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"RBMX (a heterogeneous nuclear ribonucleoprotein) associates with ERAP1 (ARTS-1) by co-immunoprecipitation, and RNAi knockdown of RBMX reduces both constitutive TNFR1 exosome-like vesicle release and IL-1β-mediated inducible proteolytic cleavage of TNFR1 ectodomains.\",\n      \"method\": \"Co-immunoprecipitation, RNA interference\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single Co-IP plus RNAi phenotype, single lab\",\n      \"pmids\": [\"18445477\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"X-ray crystal structures of human ERAP1 in open and closed conformations reveal a zinc-metallopeptidase with HEXXH-(X)18-E and GAMEN motifs; structures show extensive domain movements including active-site closure, and the disease-associated K528R mutant shows significantly altered peptide-processing characteristics attributable to impaired interdomain interactions.\",\n      \"method\": \"X-ray crystallography (open and closed conformations), in vitro peptide-processing assays of K528R mutant\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structures plus functional mutagenesis in a single study\",\n      \"pmids\": [\"21508329\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"X-ray crystal structure of human ERAP1 bound to bestatin reveals an open conformation with a large interior compartment and an extended groove from the catalytic center that accommodates long peptides; structural and biochemical analyses show that binding of long (but not short) substrates induces conformational change reorienting a key catalytic residue toward the active site, explaining length-dependent trimming activity.\",\n      \"method\": \"X-ray crystallography (bestatin-bound), biochemical substrate trimming assays\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure plus functional biochemical validation, single rigorous study\",\n      \"pmids\": [\"21478864\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Human cytomegalovirus miR-US4-1 specifically targets and downregulates ERAP1 expression during infection, inhibiting trimming of HCMV-derived peptides and reducing susceptibility of infected cells to HCMV-specific cytotoxic T lymphocytes.\",\n      \"method\": \"miRNA functional assays, ERAP1 expression measurement, viral peptide trimming assay, CTL cytotoxicity assay\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — specific miRNA-target validation plus functional peptide trimming and CTL killing assays\",\n      \"pmids\": [\"21892175\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"p53 upregulates ERAP1 expression by binding to a cognate p53 response element in the ERAP1 gene, increasing MHC class I surface expression; this mechanism operates in cancer cells and in influenza-infected cells where H1N1 activates p53 leading to ERAP1 upregulation.\",\n      \"method\": \"ChIP-seq, gene expression analysis, p53 silencing, ERAP1 silencing, MHC class I surface expression measurement\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — ChIP-seq identification of p53-binding site plus loss-of-function experiments in multiple cellular contexts\",\n      \"pmids\": [\"23965983\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"ERAP1 and ERAP2 form stabilized heterodimers in which physical interaction with ERAP2 changes basic enzymatic parameters of ERAP1, improving its substrate-binding affinity; the heterodimer produces mature MHC class I epitopes more efficiently than a mixture of the two enzymes unable to dimerize.\",\n      \"method\": \"Stabilized heterodimer production, in vitro epitope trimming assays comparing heterodimers vs. non-dimerizing enzyme mix, enzymatic kinetics\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution of heterodimer plus enzymatic characterization, allosteric mechanism defined\",\n      \"pmids\": [\"24928998\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"ERAP1 activity controls the surface expression of HLA-B27 free heavy chains (FHCs) on antigen-presenting cells; silencing or pharmacological inhibition of ERAP1 reduces HLA-B27 FHC surface expression, reduces KIR3DL2 engagement, and suppresses Th17 expansion and IL-17A secretion by ankylosing spondylitis CD4+ T cells.\",\n      \"method\": \"siRNA knockdown, pharmacological ERAP1 inhibition, flow cytometry, KIR3DL2-reporter cell assay, Th17 intracellular cytokine staining and ELISA\",\n      \"journal\": \"Annals of the rheumatic diseases\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal loss-of-function methods (siRNA + inhibitor) with specific cellular phenotypes (FHC expression, Th17 response)\",\n      \"pmids\": [\"26130142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Genetic or pharmacological inhibition of ERAP1 perturbs tumor cell engagement of inhibitory NK cell receptors (KIR by pMHC-I; CD94-NKG2A by nonclassical pMHC-I), reducing protection from NK cell killing; the protective effect can be restored by adding high-affinity peptides, indicating ERAP1 is required to generate high-affinity natural peptide ligands.\",\n      \"method\": \"ERAP1 inhibition (genetic and pharmacological), NK cell cytotoxicity assay, inhibitory receptor–ligand interaction measurement, high-affinity peptide add-back\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO and pharmacological inhibition with mechanistic rescue experiment, multiple NK receptor classes tested\",\n      \"pmids\": [\"25592150\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ERAP1-ERAP2 heterodimers can trim MHC I-bound precursor peptides to their correct and final lengths (albeit more slowly than free precursors); trimming of MHC I-bound precursors by the heterodimer increases the conformational stability of MHC I/peptide complexes.\",\n      \"method\": \"ERAP1/ERAP2 heterodimer production, in vitro trimming assays of free and HLA-B*0801-bound N-terminally extended peptides, conformational stability assessment\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted heterodimer with in vitro trimming of MHC-bound substrates and stability measurement\",\n      \"pmids\": [\"27514473\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ERAP1 knockdown in monocytic U937 cells expressing HLA-B27 specifically increases cell surface accumulation of HLA-B27 (including disulfide-linked dimers) but has no effect on HLA-B18 or HLA-B51, indicating that ERAP1 activity selectively controls HLA-B27 surface expression and aberrant heavy-chain dimer formation.\",\n      \"method\": \"ERAP1 siRNA knockdown, immunoprecipitation, isoelectric focusing, immunoblotting, flow cytometry with subtype-specific antibodies, non-reducing PAGE for disulfide-linked dimers\",\n      \"journal\": \"Molecular immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean knockdown with multiple specific detection methods demonstrating allele-specific effect\",\n      \"pmids\": [\"27107845\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"HCMV miR-UL112-5p targets the ERAP1 3′ UTR (A variant), reducing ERAP1 expression at RNA and protein levels and inhibiting processing and presentation of the HCMV pp65495–503 peptide to CTLs; a naturally occurring rs17481334 G variant in the ERAP1 3′ UTR prevents miR-UL112-5p binding, preserving ERAP1 expression and CTL killing.\",\n      \"method\": \"miRNA–3′UTR binding assay, ERAP1 expression measurement (RNA and protein), CTL cytotoxicity assay, genotype analysis of human fibroblasts\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct miRNA-target interaction demonstrated plus functional rescue by G-variant, mechanistically specific\",\n      \"pmids\": [\"28746870\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"ERAP1 binds the deubiquitylase USP47, displaces USP47-associated βTrCP (the substrate receptor of SCFβTrCP ubiquitin ligase), and promotes βTrCP degradation; this leads to upregulation of Gli transcription factors and enhancement of Hedgehog signaling pathway activity, and genetic or pharmacological ERAP1 inhibition suppresses Hedgehog-dependent tumor growth in vitro and in vivo.\",\n      \"method\": \"Co-immunoprecipitation (ERAP1–USP47 and USP47–βTrCP interaction), genetic knockdown/knockout, pharmacological inhibition, Gli reporter assay, in vivo tumor model\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP plus in vivo functional validation plus multiple loss-of-function approaches\",\n      \"pmids\": [\"31341163\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Pharmacological inhibition of ERAP1 in A375 melanoma cells alters the qualitative and quantitative composition of the MHC-I immunopeptidome (affecting ~half of 3204 identified peptides) without reducing surface MHC-I expression; inhibition reduces presentation of suboptimal long peptides and increases presentation of high-affinity 9–12-mers, suggesting baseline ERAP1 activity is destructive for many potential epitopes in this line.\",\n      \"method\": \"ERAP1 inhibitor treatment, MHC-I peptide isolation, LC-MS/MS mass spectrometry of eluted peptides, MHC-I affinity prediction\",\n      \"journal\": \"Cancer immunology, immunotherapy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — pharmacological inhibition with large-scale immunopeptidomics and quantitative analysis\",\n      \"pmids\": [\"31222486\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"X-ray crystallographic structures of HLA-B*0801 bound to N-terminally extended 10–20-mer precursor peptides show that residue extensions protrude out of the A pocket while the peptide core adopts a canonical conformation; ERAP1-mediated trimming of MHC I-bound peptides requires a minimal length of 14 amino acids, and HLA-B*0801 residue 62 is critical for opening the A pocket to accommodate the extension.\",\n      \"method\": \"X-ray crystallography (1.40–1.65 Å resolution), thermostability assays, in vitro ERAP1 trimming assay of MHC I-bound peptides\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution crystal structures plus biochemical trimming assays with defined minimal-length requirement\",\n      \"pmids\": [\"31601650\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"ERAP1 conformational states in solution (open and closed) occur during the catalytic cycle and are promoted by binding of long peptide substrates; allosteric activators shift the enzyme toward closed conformation, inhibitors toward open; structural reconfigurations of the active site are physically linked to domain closure, providing the mechanistic basis for allosteric regulation and explaining the Lys/Arg528 polymorphism disease association.\",\n      \"method\": \"Small-angle X-ray scattering (SAXS) in solution, X-ray crystallography, chemical crosslinking to localize C-terminal binding sites, enzymatic assays with substrates/allosteric modulators/inhibitors\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple structural methods (SAXS + crystallography + crosslinking) plus enzymatic validation, mechanistic model validated\",\n      \"pmids\": [\"34489420\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In psoriasis, ERAP1 generates the causative melanocyte autoantigen by trimming N-terminally extended peptide precursors to the length required for presentation by HLA-C*06:02; an ERAP1 risk haplotype produces the autoantigen more efficiently and increases HLA-C expression and stimulation of a psoriatic autoreactive TCR. ERAP1 knockout significantly reduces cell-surface HLA-C expression more than total HLA class I.\",\n      \"method\": \"Genetically modified cell lines, TCR activation assay with autoreactive psoriatic TCR, ERAP1 knockout, in vitro peptide trimming assays, flow cytometry for HLA-C surface expression\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple genetically defined cell lines with functional TCR activation and ERAP1 KO rescue experiments\",\n      \"pmids\": [\"34580106\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ERAP1 functions as an inflammation-induced hepatokine; hepatically secreted ERAP1 interacts with β2 adrenergic receptor (ADRB2) in skeletal muscle, reduces ADRB2 expression by decreasing USP33-mediated deubiquitination, and thereby impairs ADRB2-stimulated insulin signaling, attenuating skeletal muscle insulin sensitivity.\",\n      \"method\": \"Hepatic overexpression and knockdown in vivo (HFD mice), serum ERAP1 measurement, co-immunoprecipitation (ERAP1–ADRB2 interaction), ubiquitination assay (USP33-mediated deubiquitination), insulin signaling assays in skeletal muscle\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo gain/loss-of-function with mechanistic co-IP and deubiquitination biochemistry\",\n      \"pmids\": [\"35192681\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"ERAP1 (PILS-AP) contains the HEXXH(X)18E zinc-binding motif characteristic of M1 family aminopeptidases and a signal sequence directing it to intracellular vesicles; recombinant protein shows leucine-specific (and lesser methionine) aminopeptidase activity inhibited by metal chelators, but insensitive to puromycin.\",\n      \"method\": \"cDNA cloning, GFP fusion protein localization in COS-7 and BHK cells, recombinant expression in Sf9 insect cells, aminoacyl β-naphthylamide substrate hydrolysis assays, inhibitor profiling\",\n      \"journal\": \"European journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — recombinant protein enzymatic assay plus subcellular localization with GFP fusion\",\n      \"pmids\": [\"10824104\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ERAP1 is an ER-resident zinc metallopeptidase (M1 family) that acts as a 'molecular ruler,' trimming N-terminally extended peptide precursors to 8–10-mers for loading onto MHC class I molecules via a conformational cycle (open→closed) triggered by long-peptide binding; it forms allosterically enhanced heterodimers with ERAP2, directly controls the immunopeptidome composition and immunodominance hierarchies for CD8+ T and NK cell responses, promotes TNFR1 and IL-6Rα ectodomain shedding through direct receptor binding, participates in Hedgehog signaling by binding USP47 and destabilizing βTrCP, and acts as an inflammation-induced hepatokine that impairs skeletal muscle insulin sensitivity by binding ADRB2 and inhibiting its USP33-mediated deubiquitination.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"ERAP1 is an endoplasmic reticulum-resident M1-family zinc metallopeptidase that trims N-terminally extended peptide precursors to optimal 8–10-mer lengths for loading onto MHC class I molecules, thereby shaping the immunopeptidome and controlling CD8+ T cell immunodominance hierarchies and NK cell recognition [PMID:16754858, PMID:31222486]. It operates via a conformational open-to-closed catalytic cycle triggered by long-peptide binding, with the internal cavity acting as a molecular ruler that senses substrate length; disease-associated polymorphisms such as K528R impair this interdomain mechanism [PMID:21478864, PMID:34489420]. ERAP1 forms allosterically enhanced heterodimers with ERAP2 that improve substrate-binding affinity and generate mature epitopes more efficiently, and these heterodimers can also trim MHC I-bound precursors [PMID:24928998, PMID:27514473]. Beyond antigen processing, ERAP1 promotes TNFR1 and IL-6Rα ectodomain shedding through direct receptor binding [PMID:12189246, PMID:12748171], enhances Hedgehog signaling by binding USP47 and destabilizing βTrCP [PMID:31341163], and acts as a hepatokine that impairs skeletal muscle insulin sensitivity by binding ADRB2 and inhibiting USP33-mediated deubiquitination [PMID:35192681].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Identification of ERAP1 as a signal-peptide-bearing M1 zinc metallopeptidase with leucine-preferring aminopeptidase activity established its catalytic identity and vesicular localization, setting the stage for functional studies.\",\n      \"evidence\": \"cDNA cloning, recombinant enzyme assays with aminoacyl β-naphthylamide substrates, and GFP-fusion localization in COS-7/BHK cells\",\n      \"pmids\": [\"10824104\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Physiological substrates in vivo unknown\",\n        \"No structural information available\",\n        \"Precise ER versus other vesicular compartment localization not distinguished\"\n      ]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Discovery that ERAP1 physically binds TNFR1 and promotes its ectodomain shedding revealed an unexpected non-peptide-trimming function — receptor processing at the cell surface — and showed that this shedding role was independent of ERAP1's own proteolytic activity.\",\n      \"evidence\": \"Yeast two-hybrid, co-IP, overexpression and antisense knockdown in pulmonary epithelial/endothelial cells\",\n      \"pmids\": [\"12189246\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Identity of the actual sheddase recruited by ERAP1 unknown\",\n        \"Whether ERAP1 exits the ER to reach TNFR1 at the surface not resolved\"\n      ]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Demonstration that ERAP1 binds IL-6Rα and is required for its constitutive shedding — and that this shedding requires ERAP1 catalytic activity — distinguished mechanistically between ERAP1's enzymatic and non-enzymatic receptor-shedding roles.\",\n      \"evidence\": \"Reciprocal co-IP, ERAP1-null cells showing loss of basal shedding, catalytic-dead mutant analysis\",\n      \"pmids\": [\"12748171\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether ERAP1 directly cleaves IL-6Rα or activates another sheddase not determined\",\n        \"Structural basis of the ERAP1–IL-6Rα interaction unknown\"\n      ]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Discovery that ERAP1 and ERAP2 form ER-resident heterodimers performing concerted peptide trimming — with ERAP2 cleaving N-terminal residues refractory to ERAP1 — explained how the full range of MHC I precursors are processed.\",\n      \"evidence\": \"Co-IP, co-localization, in vitro peptide digestion, cellular antigen presentation assays\",\n      \"pmids\": [\"15908954\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Stoichiometry and structural architecture of the heterodimer not resolved\",\n        \"Allosteric regulation between subunits not yet characterized\"\n      ]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Genetic knockout of ERAP1 in mice proved it is the major ER peptide trimming enzyme in vivo, directly controlling peptide–MHC I complex abundance and shifting CD8+ T cell immunodominance hierarchies during viral infection.\",\n      \"evidence\": \"ERAP1 knockout mouse, viral infection models, CD8+ T cell immunodominance assays across multiple epitopes\",\n      \"pmids\": [\"16754858\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Contribution of ERAP2 versus ERAP1 in vivo not separated (mice lack ERAP2)\",\n        \"Whether ERAP1 loss also affects non-classical MHC I presentation not examined\"\n      ]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Characterization of the K528R disease-associated polymorphism as catalytically impaired, with K528 positioned near the substrate pocket, provided the first genotype-to-enzymatic-activity link and a rationale for disease associations.\",\n      \"evidence\": \"Site-directed mutagenesis panel, in vitro aminopeptidase assays, molecular modeling\",\n      \"pmids\": [\"16513116\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No crystal structure to confirm K528 positioning\",\n        \"Effect on peptide trimming in cells not tested\"\n      ]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Systematic substrate profiling revealed that ERAP1 trimming rates depend on internal peptide sequence (up to 40,000-fold variation), consistent with a large internal cavity sensing full peptide length — the 'molecular ruler' concept.\",\n      \"evidence\": \"In vitro trimming of systematically varied peptide collections, modeling of internal cavity\",\n      \"pmids\": [\"18987748\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No direct structural evidence for cavity–peptide contacts\",\n        \"Molecular ruler mechanism not validated in a cellular context\"\n      ]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Crystal structures of ERAP1 in open and closed conformations, and bound to bestatin, revealed the structural basis for length-dependent trimming: long-substrate binding induces domain closure that repositions a catalytic residue, explaining how the enzyme preferentially trims long precursors and how K528R disrupts interdomain interactions.\",\n      \"evidence\": \"X-ray crystallography (multiple conformations, bestatin-bound), enzymatic assays with K528R mutant\",\n      \"pmids\": [\"21508329\", \"21478864\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No structure of ERAP1 bound to a native peptide substrate\",\n        \"Conformational dynamics during the catalytic cycle not captured in crystals\"\n      ]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"HCMV miR-US4-1 was shown to specifically target ERAP1 mRNA, reducing peptide trimming and CTL killing of infected cells — establishing viral immune evasion through ERAP1 suppression as a pathogenically relevant strategy.\",\n      \"evidence\": \"miRNA functional assays, ERAP1 expression measurement, viral peptide trimming and CTL cytotoxicity assays\",\n      \"pmids\": [\"21892175\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether other herpesviruses use analogous miRNA strategies unknown\",\n        \"Contribution relative to other HCMV immune evasion genes not quantified\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Reconstitution of stabilized ERAP1–ERAP2 heterodimers demonstrated allosteric enhancement: physical interaction with ERAP2 improved ERAP1 substrate-binding affinity and produced mature epitopes more efficiently than a non-dimerizing enzyme mixture.\",\n      \"evidence\": \"Stabilized heterodimer production, comparative enzyme kinetics, in vitro epitope trimming\",\n      \"pmids\": [\"24928998\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of allosteric communication between ERAP1 and ERAP2 not resolved\",\n        \"In vivo relevance of allosteric enhancement not yet demonstrated\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"ERAP1 activity was shown to control HLA-B27 free heavy chain surface expression, KIR3DL2 engagement, and Th17 expansion in ankylosing spondylitis, providing a direct mechanistic link between ERAP1 peptide trimming and autoimmune pathology.\",\n      \"evidence\": \"siRNA knockdown and pharmacological ERAP1 inhibition in antigen-presenting cells, KIR3DL2 reporter assays, Th17 cytokine measurements from AS patient cells\",\n      \"pmids\": [\"26130142\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Which specific peptides drive HLA-B27 FHC formation not identified\",\n        \"Whether ERAP1 inhibition is therapeutic in vivo for AS not tested\"\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstration that ERAP1–ERAP2 heterodimers trim MHC I-bound precursor peptides (not only free peptides) and improve pMHC stability expanded the functional scope of ERAP1 trimming beyond the free-peptide pool.\",\n      \"evidence\": \"In vitro trimming of HLA-B*0801-bound N-terminally extended peptides, conformational stability assays\",\n      \"pmids\": [\"27514473\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Physiological relevance of MHC-bound trimming versus free-peptide trimming not quantified in cells\",\n        \"Whether tapasin or other PLC components modulate on-MHC trimming unknown\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"ERAP1 was found to bind USP47, displacing βTrCP from USP47 and promoting βTrCP degradation, thereby upregulating Gli transcription factors and Hedgehog signaling — revealing a non-canonical signaling role outside the antigen-processing pathway.\",\n      \"evidence\": \"Reciprocal co-IP, genetic knockdown/knockout, pharmacological inhibition, Gli reporter assays, in vivo tumor xenograft model\",\n      \"pmids\": [\"31341163\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether ERAP1's aminopeptidase activity is required for USP47 binding not determined\",\n        \"Structural basis of ERAP1–USP47 interaction unknown\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Immunopeptidomics upon pharmacological ERAP1 inhibition revealed that baseline ERAP1 activity is destructive for many potential epitopes, not only generative — shifting the view from ERAP1 as a simple epitope producer to a dual editor of the immunopeptidome.\",\n      \"evidence\": \"ERAP1 inhibitor treatment of A375 melanoma, LC-MS/MS immunopeptidome profiling of ~3204 peptides\",\n      \"pmids\": [\"31222486\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether destructive trimming is cell-type or allele dependent not addressed\",\n        \"Functional immunogenicity of the altered peptidome not tested with T cells\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Solution SAXS and crystallography confirmed that open-to-closed conformational transitions occur during catalysis in solution, are driven by long-peptide binding, and are modulated by allosteric activators/inhibitors — unifying the structural and biochemical molecular-ruler model.\",\n      \"evidence\": \"SAXS, X-ray crystallography, chemical crosslinking, enzymatic assays with allosteric modulators\",\n      \"pmids\": [\"34489420\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Full catalytic cycle dynamics at single-molecule resolution not captured\",\n        \"How heterodimer formation with ERAP2 modulates conformational dynamics unknown\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"In psoriasis, ERAP1 was shown to generate the causative melanocyte autoantigen by trimming precursors for HLA-C*06:02 presentation, with a risk haplotype producing the autoantigen more efficiently — directly connecting ERAP1 genotype to autoimmune epitope generation.\",\n      \"evidence\": \"ERAP1 KO and genetically defined cell lines, autoreactive psoriatic TCR activation assay, in vitro peptide trimming, flow cytometry\",\n      \"pmids\": [\"34580106\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether ERAP1 inhibition is therapeutic in psoriasis in vivo unknown\",\n        \"Full set of ERAP1-dependent autoantigens in psoriasis not mapped\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Discovery of ERAP1 as a secreted hepatokine that binds ADRB2 in skeletal muscle and impairs insulin signaling by inhibiting USP33-mediated deubiquitination of ADRB2 revealed a systemic metabolic role entirely independent of antigen processing.\",\n      \"evidence\": \"Hepatic overexpression/knockdown in HFD mice, serum ERAP1 measurement, co-IP of ERAP1–ADRB2, ubiquitination/deubiquitination assays, insulin signaling readouts in skeletal muscle\",\n      \"pmids\": [\"35192681\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How ERAP1 is secreted from the ER lumen to serum not elucidated\",\n        \"Whether the hepatokine function requires ERAP1 aminopeptidase activity unknown\",\n        \"Relevance in human metabolic disease not confirmed\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis of ERAP1–ERAP2 heterodimer allostery, how ERAP1 exits the ER for its receptor-shedding and hepatokine roles, whether aminopeptidase activity is required for all non-canonical functions (Hedgehog, ADRB2), and whether ERAP1 inhibition can be therapeutically exploited in autoimmunity or cancer.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No structure of ERAP1–ERAP2 heterodimer available\",\n        \"ER-exit or secretion mechanism undefined\",\n        \"Therapeutic efficacy of ERAP1 modulation not tested in clinical studies\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 3, 6, 9, 12, 15, 19, 20, 22, 24]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [4, 6, 24]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [18, 23]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 24]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [23]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 3, 10, 11, 13, 14, 17, 19, 22]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [6, 8, 9, 15, 20, 21]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 2, 18, 23]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [13, 16, 22]}\n    ],\n    \"complexes\": [\n      \"ERAP1–ERAP2 heterodimer\",\n      \"NUCB2–ERAP1–TNFR1 complex\"\n    ],\n    \"partners\": [\n      \"ERAP2\",\n      \"TNFRSF1A\",\n      \"IL6R\",\n      \"NUCB2\",\n      \"USP47\",\n      \"ADRB2\",\n      \"RBMX\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}