{"gene":"SERPING1","run_date":"2026-04-28T20:42:07","timeline":{"discoveries":[{"year":1973,"finding":"C1-INH (SERPING1 product) directly inhibits activated Hageman factor (Factor XII) fragments, blocking their capacity to initiate kinin generation, fibrinolysis, and coagulation. The inhibition is time-dependent and acts on the fragments themselves rather than on downstream effectors (kallikrein or plasmin).","method":"In vitro functional inhibition assay with purified C1-INH and Hageman factor fragments; dose-response analysis; gel electrophoresis","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 1 — purified protein in vitro assay with dose-response and mechanistic controls, foundational paper with 195 citations","pmids":["4703226"],"is_preprint":false},{"year":1972,"finding":"C1-INH inactivates C1* (the activated C1 complex) and this inactivation is accompanied by loss of C1* activity against C2, TAMe, and ATMe synthetic substrates, without appreciably affecting activity toward C4 or AAMe, indicating that C1-INH-mediated inhibition of C1 involves an allosteric or active-site mechanism selective for certain enzymatic activities.","method":"In vitro enzyme activity assays with synthetic substrates; comparison of heat-inactivated vs. C1INH-inactivated C1*","journal":"Immunology","confidence":"Medium","confidence_rationale":"Tier 1 — in vitro assay with functional readouts, single lab single paper","pmids":["5063623"],"is_preprint":false},{"year":1981,"finding":"Sialic acid residues on C1-INH are required for normal circulatory half-life; removal of sialic acid by neuraminidase causes rapid hepatic clearance via asialoglycoprotein receptors, while subsequent removal of galactose returns survival to near-normal. C1s inhibitory activity of C1-INH is unimpaired by desialylation, showing sialic acid regulates pharmacokinetics not catalytic function.","method":"In vivo rabbit clearance studies; glycosidase treatment; organ distribution of radiolabeled C1-INH; competitive inhibition with asialo-alpha1-acid glycoprotein","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 1-2 — in vivo pharmacokinetics with orthogonal biochemical and competitive inhibition controls","pmids":["7451969"],"is_preprint":false},{"year":1989,"finding":"In acquired C1-INH deficiency type II, anti-C1-INH autoantibodies drive cleavage of C1-INH at its active site by a target protease without formation of a covalent C1-INH–enzyme complex, generating an Mr 96,000 fragment. NH2-terminal sequence analysis confirmed this cleavage product.","method":"NH2-terminal sequence analysis of patient C1-INH fragments; functional assays of C1-INH before and after C1-INH concentrate infusion; SDS-PAGE","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 1 — direct protein sequencing identifying cleavage site mechanism","pmids":["2723058"],"is_preprint":false},{"year":1994,"finding":"A naturally occurring mutant C1-INH (from a kindred with incomplete C4 deficiency) inhibits C1s but not C1r, demonstrating that distinct structural determinants on C1-INH mediate inhibition of these two proteases separately. Approximately 50% of C1-INH molecules from affected members resist trypsin cleavage at Arg444.","method":"Functional binding assays with activated C1s and C1r; trypsin cleavage resistance assay; purification from patient plasma","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 1-2 — functional biochemical dissection of differential protease inhibition, replicated on purified protein from patient samples","pmids":["8144914"],"is_preprint":false},{"year":1996,"finding":"C1INH-Ta, a naturally occurring mutant with deletion of Lys-251, forms no covalent complex with C1s, C1r, or kallikrein (inefficient complex with beta-FXIIa only), and instead undergoes partial substrate cleavage by each protease. The mutation causes a folding abnormality with two populations: one susceptible to multimerization (expressing neoepitopes normally exposed only on protease-complexed C1-INH) and one converted to a substrate with residual inhibitory activity.","method":"In vitro protease complex formation assay with recombinant protein expressed in COS cells; SDS-PAGE; Superose 12 size fractionation; thermal stability analysis; epitope mapping","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstituted recombinant protein, multiple orthogonal assays including size fractionation and mutagenesis-equivalent natural variant","pmids":["8798678"],"is_preprint":false},{"year":1998,"finding":"Anti-C1-INH autoantibodies prevent formation of the stable covalent C1s–C1-INH complex by converting C1-INH to a substrate; in the presence of autoantibodies C1s cleaves C1-INH without forming a covalent bond. Autoantibodies act prior to enzyme-inhibitor complex formation and do not dissociate pre-formed complexes. The epitopes recognized map to C1-INH residues 438-459.","method":"SDS-PAGE; hydrolysis of synthetic ester substrate; affinity-purified autoantibodies from two patients; peptide competition assays","journal":"Molecular medicine","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro mechanistic assay with purified components, peptide mapping, two patient sources","pmids":["9508789"],"is_preprint":false},{"year":1997,"finding":"A C1-INH-like molecule (C1-INH-L) is present on the surface of human sperm, anchored to the plasma membrane (trypsin-sensitive, resistant to PIPLC/EDTA/acid), localizes to head and midpiece, and is present on both uncapacitated and capacitated sperm. Anti-C1-INH antibodies reduce sperm motility and progressive velocity in the absence of complement.","method":"Western blot; ELISA; immunofluorescence; computerized sperm motion analysis with anti-C1-INH IgG treatment","journal":"American journal of reproductive immunology","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct localization with functional consequence (motility reduction), single lab","pmids":["9412721"],"is_preprint":false},{"year":1998,"finding":"C1-INH-like protein on murine spermatozoa (MW ~100 kDa) localizes to sperm head and midpiece. Anti-C1-INH antibody treatment reduces murine sperm motility, in vitro fertilization rates, and embryo development rates, establishing a functional role for this protein in reproduction.","method":"Western blot; immunofluorescence; in vitro fertilization assay with anti-C1-INH antibody; sperm motility assay","journal":"Autoimmunity","confidence":"Medium","confidence_rationale":"Tier 2 — functional in vitro assay with specific antibody, loss-of-function phenotype","pmids":["10607415"],"is_preprint":false},{"year":2003,"finding":"A deletion mutant of C1-INH lacking the N-terminal 1-99 amino acids (delta-1-99AA) is expressed on xenogeneic cell surfaces (unlike other deletion mutants which remain cytoplasmic), and this surface-bound form blocks human complement-mediated cell lysis (~57-90%) by suppressing both C4 and C3 deposition (~40% each), demonstrating that cell-surface C1-INH can inhibit complement through a distinct mechanism from DAF.","method":"Transfection of deletion mutant constructs in CHO cells and pig endothelial cells; flow cytometry for C4 and C3 deposition; complement-mediated lysis assay","journal":"Xenotransplantation","confidence":"Medium","confidence_rationale":"Tier 2 — functional mutagenesis with direct mechanistic readout of complement inhibition","pmids":["12588646"],"is_preprint":false},{"year":2009,"finding":"Polyanions (dextran sulfate, heparin) bind directly to C1s and modulate its proteolytic activity biphasically (enhancement at low concentration, inhibition at higher concentration). Acceleration of the C1s–SERPING1 reaction by polyanions requires both protease-polyanion and serpin-polyanion interactions; a chimeric alpha1-antitrypsin with SERPING1 RCL residues that inhibits C1s but cannot bind polyanions showed that the DXS-mediated acceleration correlates with DXS effects on C1s activity, demonstrating that polyanion-C1s interaction contributes to the acceleration mechanism.","method":"In vitro association rate assay with chimeric serpin mutant; protease activity assays with synthetic substrates; binding studies with DXS and heparin","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro system, chimeric mutant as mechanistic probe, multiple substrates","pmids":["19522701"],"is_preprint":false},{"year":2017,"finding":"Knockdown or knockout of Serping1 in mice impairs neuronal stem cell proliferation and delays radial neuronal migration in the developing cortex, with both cell-autonomous and non-cell-autonomous effects. The migration defect is rescued by expression of cleaved C3 protein components or a dual C3aR/C5aR agonist, placing Serping1 upstream of complement C3 activation and C5a receptor signaling in cortical development.","method":"In utero electroporation knockdown; Serping1 knockout mice; neuronal migration assays; rescue with cleaved C3 protein or C3aR/C5aR agonist","journal":"Frontiers in cellular neuroscience","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis in vivo with multiple rescue experiments placing SERPING1 upstream of complement signaling in cortical migration","pmids":["28670268"],"is_preprint":false},{"year":2018,"finding":"A subset of HAE-causing SERPING1 variants encoded by mutant alleles exert a dominant-negative effect on wild-type C1-INH secretion by triggering protein-protein interactions between normal and mutant C1-INH, leading to intracellular aggregation and retention in the endoplasmic reticulum (ER). This ER trapping was observed in fibroblasts from a heterozygous carrier and was ameliorated by viral delivery of the SERPING1 gene.","method":"Cell transfection; co-immunoprecipitation; immunofluorescence localization; fibroblast cultures from patient; AAV gene delivery rescue experiment","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (co-IP, localization, patient cells, gene rescue), Strong evidence for dominant-negative ER retention mechanism","pmids":["30398465"],"is_preprint":false},{"year":2020,"finding":"Serping1/C1-INH is secreted by renal tubular cells through a mitophagy-dependent mechanism; high-dose ascorbate stimulates tubular secretion of SerpinG1 via NRF2 transactivation. Secreted SerpinG1 promotes anti-inflammatory M2 macrophage polarization and prevents septic acute kidney injury. Kidney-specific SerpinG1 knockdown (AAV9-shRNA) abolishes these protective effects.","method":"FACS; RNA-sequencing; GSEA; luciferase reporter; ChIP assay; AAV9 gene knockdown in kidney-specific manner; co-culture systems; Atg7 conditional knockout mice","journal":"International journal of biological sciences","confidence":"Medium","confidence_rationale":"Tier 2 — multiple mechanistic methods including in vivo KO and ChIP, single lab","pmids":["35982894"],"is_preprint":false},{"year":2022,"finding":"SERPING1-encoded C1-INH forms covalent complexes with C1s (classical pathway) and MASP-1 (lectin pathway); measurement of C1s/C1-INH and MASP-1/C1-INH complexes by sandwich ELISA distinguishes early classical from early lectin pathway complement activation. Both complex levels are elevated in COVID-19 patients.","method":"Sandwich ELISA development and validation; zymosan activation of complement; clinical sample measurement in 414 COVID-19 patients and 96 healthy controls","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 2 — validated immunoassay with functional activation control, identifies specific covalent complexes, single lab","pmids":["36420270"],"is_preprint":false},{"year":2023,"finding":"For a large set of HAE-causing SERPING1 variants (28 tested), coexpression of mutant and normal C1INH negatively affects the overall capacity to target proteases (dominant-negative trans-inhibition). A subset of variants drive intracellular C1INH foci formation only in heterozygous configurations (requiring simultaneous expression of normal and mutant C1INH), identifying distinct molecular disease mechanisms including serpinopathy-type aggregation.","method":"Transfection of HeLa cells with 28 SERPING1 variant constructs; comparative studies of C1INH expression, secretion, functionality, and intracellular localization; co-expression of wild-type and mutant constructs","journal":"The Journal of allergy and clinical immunology","confidence":"High","confidence_rationale":"Tier 2 — systematic functional characterization of 28 variants with orthogonal assays (expression, secretion, function, localization), provides mechanistic classification","pmids":["37301409"],"is_preprint":false},{"year":2021,"finding":"A missense SERPING1 mutation p.S150F produces a C1INH protein that is stably expressed intracellularly but not secreted, and when coexpressed with wild-type C1INH it prevents secretion of wild-type C1INH and promotes intracellular degradation of the wild-type protein through protein-protein interaction, demonstrating dominant-negative disease mechanism.","method":"In vitro cell transfection with mutant and wild-type constructs; secretion assay; co-expression experiments; intracellular degradation assay","journal":"The Journal of dermatology","confidence":"Medium","confidence_rationale":"Tier 2 — mechanistic in vitro co-expression experiments demonstrating dominant-negative effect, single lab","pmids":["33914953"],"is_preprint":false},{"year":2020,"finding":"Homozygous SERPING1 variant S438F (in the reactive center loop) renders C1INH predominantly in the cleaved/inactive 96-kDa isoform and severely reduces C1INH interaction with target proteases C1s and FXIIa (to 4-8% of controls for FXIIa in homozygotes), while the homozygous I379T variant (in the gate region) shows near-normal heterozygous function but fails to inhibit C1s and FXIIa as a homozygote, demonstrating region-specific mechanisms of C1INH dysfunction.","method":"Functional protease binding assays measuring C1INH-C1s and C1INH-FXIIa complex formation; SDS-PAGE for isoform analysis; patient plasma studies","journal":"Immunology and cell biology","confidence":"Medium","confidence_rationale":"Tier 2 — functional biochemical characterization of natural variants in specific structural domains, patient plasma validation","pmids":["32445210"],"is_preprint":false},{"year":2024,"finding":"A novel SERPING1 variant c.708T>G leads to accumulation of C1-INH in the endoplasmic reticulum, upregulation of GRP75, calcium (Ca2+) overload, mitochondrial structural and functional disruption, and apoptosis. siRNA knockdown of GRP75 mitigates the calcium overload and mitochondrial damage, placing GRP75 downstream of mutant C1-INH ER retention.","method":"Cell transfection with variant construct; ER localization assay; GRP75 Western blot; Ca2+ measurement; mitochondrial assays; siRNA knockdown of GRP75","journal":"Orphanet journal of rare diseases","confidence":"Medium","confidence_rationale":"Tier 2 — mechanistic pathway dissection with siRNA rescue, single lab","pmids":["39272138"],"is_preprint":false},{"year":2006,"finding":"SERPING1 splice site mutations c.51+3A>G and c.51+5G>A cause exon 2 skipping in cell transfection assays using minigene constructs. A polymorphic variant c.-21C at the second base of exon 2 also causes low but significant exon 2 skipping in transfected hepatoma cells, potentially contributing to more severe angioedema. A tissue-specific alternative splicing of exon 3 was observed in monocytes but not liver/hepatoma cells.","method":"Minigene transfection assays in HepG2 and Hep 3B cells; RT-PCR analysis; co-segregation analysis in patient family","journal":"Human mutation","confidence":"High","confidence_rationale":"Tier 1-2 — functional splicing assay with minigene constructs and tissue-specific verification","pmids":["16470590"],"is_preprint":false},{"year":2024,"finding":"Glycogenolysis in postnatal astrocytes drives upregulation of Serping1 expression through reactive oxygen species (ROS)-NF-κB signaling pathway. LPS-induced astrocytic Serping1 upregulation is governed by glycogen degradation, and glycogenolysis mediates neurotoxic astrocyte phenotypes including impaired neuronal synaptogenesis.","method":"LPS treatment of postnatal hippocampal cells; glycogenolysis activation/inhibition; ROS measurement; NF-κB pathway analysis; neuronal synaptogenesis assays","journal":"Molecular neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 — mechanistic pathway dissection with specific inhibitors, single lab","pmids":["38985256"],"is_preprint":false},{"year":2023,"finding":"High levels of C1INH secreted by IL-1β/TNF-α/IFN-γ-reprogrammed mesenchymal stem cells (ITI-hUC-MSCs) prevent inflammation-induced profibrotic CD301+ macrophage polarization by downregulating the JAK-STAT signaling pathway, thereby reducing endometrial fibrosis.","method":"FACS for macrophage polarization; RNA-seq; functional co-culture assays; ITI-hUC-MSC secretome analysis; IUA mouse model","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2 — functional in vivo and in vitro experiments with mechanistic pathway identification (JAK-STAT), single lab","pmids":["37456855"],"is_preprint":false},{"year":2018,"finding":"Retinal pigment epithelium (RPE) cells upregulate C1INH expression in co-cultured bone marrow-derived macrophages, suggesting a paracrine mechanism by which RPE modulates complement regulatory expression at the retina-choroidal interface. Under inflammatory conditions (TNF-α-treated RPE), C1INH expression in macrophages is further enhanced.","method":"Co-culture of BMDMs with RPE cells/eyecups; real-time RT-PCR of complement gene expression","journal":"Aging","confidence":"Low","confidence_rationale":"Tier 3 — gene expression in co-culture without direct protein-level or pathway mechanistic validation","pmids":["29905533"],"is_preprint":false},{"year":2025,"finding":"SP5 (WNT inhibitor/transcription factor) facilitates SERPING1 transcription by binding to the SERPING1 gene promoter. SERPING1 suppresses lung adenocarcinoma cell proliferation, migration, and invasion via the TSC2/mTOR pathway.","method":"Luciferase reporter assay; ChIP assay; in vivo and in vitro LUAD cell assays; Mendelian randomization; multi-omics","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP and luciferase reporter for promoter binding, in vivo functional assays for pathway placement, single lab","pmids":["39962118"],"is_preprint":false}],"current_model":"SERPING1 encodes C1 inhibitor (C1-INH), a serine protease inhibitor (serpin) that forms irreversible covalent complexes with and inactivates multiple proteases including C1r, C1s, MASP-1, activated Factor XII (Hageman factor), and plasma kallikrein, thereby controlling the classical and lectin complement pathways and the contact/kallikrein-kinin system; sialic acid residues regulate its circulatory half-life via hepatic asialoglycoprotein receptors; polyanions (heparin, dextran sulfate) accelerate C1s inhibition through dual interactions with both C1s and the serpin RCL; disease-causing SERPING1 variants cause C1-INH deficiency either through haploinsufficiency, dominant-negative intracellular aggregation and ER retention, or conversion of C1-INH from an inhibitor to a substrate; and beyond complement regulation, C1-INH plays roles in cortical neuronal migration (upstream of C3/C5aR signaling), macrophage polarization (via JAK-STAT suppression), renal tubular immune modulation (via NRF2/mitophagy-dependent secretion), and sperm surface function."},"narrative":{"teleology":[{"year":1972,"claim":"Establishing that C1-INH directly inactivates the activated C1 complex resolved the identity of the principal inhibitor of classical pathway initiation and showed the inhibition is selective for certain enzymatic activities of C1*.","evidence":"In vitro enzyme activity assays with synthetic substrates comparing heat-inactivated vs. C1-INH-inactivated C1*","pmids":["5063623"],"confidence":"Medium","gaps":["Mechanism of selectivity for C2-cleaving but not C4-cleaving activity was not resolved","Stoichiometry of the C1-INH–C1 interaction was not determined"]},{"year":1973,"claim":"Demonstrating that C1-INH directly inhibits activated Factor XII fragments established that a single serpin controls both complement and contact/kinin pathways, explaining the dual phenotype (complement consumption and bradykinin generation) in C1-INH deficiency.","evidence":"In vitro functional inhibition assay with purified C1-INH and Hageman factor fragments, dose-response analysis","pmids":["4703226"],"confidence":"High","gaps":["Relative physiological contribution of C1-INH vs. other Factor XII inhibitors not quantified","Kinetic parameters for Factor XII inhibition were not determined"]},{"year":1981,"claim":"Revealing that sialic acid residues govern C1-INH circulatory half-life via hepatic asialoglycoprotein receptors, without affecting inhibitory activity, separated the pharmacokinetic from catalytic determinants of C1-INH function.","evidence":"In vivo rabbit clearance studies with glycosidase-treated radiolabeled C1-INH; competitive inhibition with asialo-alpha1-acid glycoprotein","pmids":["7451969"],"confidence":"High","gaps":["Role of other glycan modifications (e.g., O-glycans on the N-terminal domain) not addressed","Human in vivo validation not performed"]},{"year":1989,"claim":"Identifying that autoantibodies in acquired C1-INH deficiency convert C1-INH from an inhibitor to a substrate (cleavage without covalent complex formation) revealed a pathogenic mechanism distinct from genetic deficiency.","evidence":"NH2-terminal sequence analysis of patient C1-INH cleavage fragments; SDS-PAGE; functional assays","pmids":["2723058"],"confidence":"High","gaps":["Structural basis for autoantibody-mediated substrate conversion was unknown"]},{"year":1994,"claim":"A natural C1-INH mutant that inhibits C1s but not C1r demonstrated that distinct structural determinants on C1-INH mediate inhibition of different target proteases, establishing that the serpin is not a generic inhibitor but has protease-specific recognition elements.","evidence":"Functional binding assays with activated C1s and C1r using purified patient-derived C1-INH; trypsin cleavage resistance at Arg444","pmids":["8144914"],"confidence":"High","gaps":["Structural basis for differential C1r vs. C1s recognition not determined","Whether exosite interactions beyond the RCL contribute was not tested"]},{"year":1996,"claim":"Characterization of the C1INH-Ta mutant (ΔLys-251) showed that a single residue deletion converts C1-INH into a substrate for multiple proteases and causes folding abnormalities with multimerization, providing a mechanistic template for serpinopathy-type disease.","evidence":"Recombinant protein expressed in COS cells; protease complex formation assays; size fractionation; thermal stability; epitope mapping","pmids":["8798678"],"confidence":"High","gaps":["Crystal structure of mutant conformer was not obtained","Whether ER quality control eliminates these misfolded species in vivo was not tested"]},{"year":1998,"claim":"Mapping autoantibody epitopes to C1-INH residues 438–459 and showing they block covalent complex formation prior to the enzyme–inhibitor encounter refined understanding of how acquired deficiency mimics the substrate-conversion mechanism seen in certain genetic mutants.","evidence":"SDS-PAGE; peptide competition assays with affinity-purified autoantibodies from two patients","pmids":["9508789"],"confidence":"High","gaps":["Whether all acquired C1-INH deficiency autoantibodies share this epitope was not established"]},{"year":1997,"claim":"Detection of a C1-INH-like molecule on human and murine sperm surfaces, with antibody-mediated reduction in motility and fertilization, suggested a complement-independent reproductive function for C1-INH.","evidence":"Western blot, immunofluorescence, and ELISA on human sperm; computerized motility analysis; murine in vitro fertilization with anti-C1-INH antibody","pmids":["9412721","10607415"],"confidence":"Medium","gaps":["Identity confirmation by mass spectrometry was not performed","Mechanism by which sperm-surface C1-INH affects motility is unknown","Whether this is the SERPING1 gene product or a cross-reactive protein was not genetically confirmed"]},{"year":2006,"claim":"Functional splicing assays demonstrated that specific SERPING1 splice-site mutations cause exon 2 skipping, and a common polymorphism at the exon 2 boundary contributes low-level aberrant splicing, providing a molecular explanation for variable expressivity in HAE families.","evidence":"Minigene transfection assays in HepG2/Hep3B cells; RT-PCR; family co-segregation analysis","pmids":["16470590"],"confidence":"High","gaps":["Quantitative contribution of aberrant splicing to circulating C1-INH levels in vivo not measured"]},{"year":2009,"claim":"Using chimeric serpins, polyanion-mediated acceleration of C1s inhibition was shown to require dual interactions with both C1s and the C1-INH RCL, establishing that glycosaminoglycans serve as a template to bridge protease and inhibitor.","evidence":"In vitro association rate assays with chimeric alpha1-antitrypsin/C1-INH RCL; protease activity assays; dextran sulfate and heparin binding studies","pmids":["19522701"],"confidence":"High","gaps":["Physiological polyanion identity in vivo (heparan sulfate vs. others) not determined","Structural model of the ternary complex lacking"]},{"year":2017,"claim":"In vivo knockout and knockdown of Serping1 impaired cortical neuronal migration, rescued by C3 cleavage products or C3aR/C5aR agonists, placing C1-INH upstream of complement-mediated signaling in brain development — a function unrelated to protease inhibition per se.","evidence":"In utero electroporation knockdown; Serping1 knockout mice; rescue with cleaved C3 protein or C3aR/C5aR agonist","pmids":["28670268"],"confidence":"High","gaps":["Whether C1-INH acts by regulating complement activation or through a separate mechanism in the developing brain was not fully resolved","Cell-autonomous vs. non-cell-autonomous contributions not dissected at the molecular level"]},{"year":2018,"claim":"Discovery that certain HAE-causing SERPING1 mutants exert dominant-negative effects by physically interacting with wild-type C1-INH and trapping it in the ER explained why some patients have more severe disease than predicted by haploinsufficiency alone.","evidence":"Co-immunoprecipitation; immunofluorescence in patient fibroblasts; AAV gene delivery rescue","pmids":["30398465"],"confidence":"High","gaps":["ER stress pathway involvement (UPR activation) not characterized","Proportion of HAE variants acting through this mechanism was unknown"]},{"year":2020,"claim":"Structure-function analysis of homozygous SERPING1 variants in the reactive center loop (S438F) and gate region (I379T) demonstrated region-specific mechanisms of dysfunction — substrate conversion vs. loss of protease interaction — refining genotype-phenotype correlations.","evidence":"Functional protease binding assays (C1s, FXIIa); SDS-PAGE isoform analysis; patient plasma studies","pmids":["32445210"],"confidence":"Medium","gaps":["Crystal structures of gate region mutants not available","Only two variants characterized in detail"]},{"year":2023,"claim":"Systematic testing of 28 HAE-causing SERPING1 variants established that dominant-negative trans-inhibition of wild-type C1-INH and serpinopathy-type intracellular aggregation occur specifically in heterozygous configurations, providing a mechanistic classification framework for HAE variants.","evidence":"Transfection of HeLa cells with 28 SERPING1 variant constructs; co-expression studies measuring expression, secretion, function, and localization","pmids":["37301409"],"confidence":"High","gaps":["In vivo validation of variant classification not performed","Whether therapeutic chaperones could rescue ER-retained variants not tested"]},{"year":2023,"claim":"Identification that C1-INH suppresses profibrotic macrophage polarization via JAK-STAT pathway downregulation extended C1-INH function beyond protease inhibition to immune cell reprogramming.","evidence":"FACS; RNA-seq; co-culture and in vivo mouse model of intrauterine adhesion","pmids":["37456855"],"confidence":"Medium","gaps":["Direct molecular target of C1-INH in JAK-STAT suppression not identified","Whether this is protease-inhibition-dependent or independent is unknown"]},{"year":2024,"claim":"A novel SERPING1 variant was shown to cause ER retention that triggers GRP75-mediated calcium overload, mitochondrial damage, and apoptosis, linking C1-INH misfolding to mitochondrial pathology beyond simple loss of secretion.","evidence":"ER localization assay; GRP75 Western blot; calcium measurement; mitochondrial assays; siRNA knockdown rescue","pmids":["39272138"],"confidence":"Medium","gaps":["Whether GRP75-mediated mitochondrial damage is a general feature of ER-retained C1-INH variants or specific to this mutation is unknown","In vivo relevance of apoptosis pathway in HAE pathology not established"]},{"year":null,"claim":"Key unresolved questions include the structural basis of C1-INH's differential protease specificity, the molecular mechanism by which C1-INH modulates JAK-STAT and mTOR signaling independent of protease inhibition, and whether therapeutic chaperones or gene therapy can rescue dominant-negative SERPING1 variants in vivo.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of C1-INH in complex with C1r, C1s, or MASP-1","Protease-independent signaling mechanisms not molecularly defined","In vivo rescue of dominant-negative variants not demonstrated in animal models"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,4,5,10,14,17]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,5,6,17]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[2,9,13,14]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[12,15,16,18]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[7,8,9]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,1,4,10,11,14]},{"term_id":"R-HSA-109582","term_label":"Hemostasis","supporting_discovery_ids":[0,17]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[3,5,6,12,15,17,18]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[11]}],"complexes":["C1-INH–C1s covalent complex","C1-INH–MASP-1 covalent complex","C1-INH–FXIIa covalent complex"],"partners":["C1S","C1R","MASP1","F12","KLKB1","GRP75","SP5"],"other_free_text":[]},"mechanistic_narrative":"SERPING1 encodes C1 inhibitor (C1-INH), a serine protease inhibitor (serpin) that controls the classical and lectin complement pathways and the contact/kallikrein-kinin system by forming irreversible covalent complexes with activated C1r, C1s, MASP-1, Factor XII, and plasma kallikrein [PMID:4703226, PMID:5063623, PMID:8144914, PMID:36420270]. Polyanions such as heparin and dextran sulfate accelerate C1-INH inhibition of C1s through dual interactions with both the protease and the serpin reactive center loop, while sialic acid residues on C1-INH regulate its circulatory half-life via hepatic asialoglycoprotein receptor-mediated clearance without affecting inhibitory function [PMID:19522701, PMID:7451969]. Loss-of-function SERPING1 mutations cause hereditary angioedema (HAE) through distinct mechanisms including haploinsufficiency, reactive center loop cleavage converting C1-INH from inhibitor to substrate, and dominant-negative intracellular aggregation wherein mutant C1-INH traps wild-type protein in the endoplasmic reticulum [PMID:8798678, PMID:30398465, PMID:37301409, PMID:32445210]. Beyond complement regulation, C1-INH promotes cortical neuronal migration upstream of C3/C5aR signaling and modulates macrophage polarization through JAK-STAT pathway suppression [PMID:28670268, PMID:37456855]."},"prefetch_data":{"uniprot":{"accession":"P05155","full_name":"Plasma protease C1 inhibitor","aliases":["C1 esterase inhibitor","C1-inhibiting factor","Serpin G1"],"length_aa":500,"mass_kda":55.2,"function":"Serine protease inhibitor, which acrs as a regulator of the classical complement pathway (PubMed:10946292, PubMed:11527969, PubMed:3458172, PubMed:6416294). Forms a proteolytically inactive stoichiometric complex with the C1r or C1s proteases (PubMed:10946292, PubMed:3458172, PubMed:6416294). May also regulate blood coagulation, fibrinolysis and the generation of kinins (PubMed:8495195). Very efficient inhibitor of FXIIa. 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SERPING1 gene causing hereditary angioedema in Brazilian families.","date":"2018","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/30389558","citation_count":8,"is_preprint":false},{"pmid":"12187480","id":"PMC_12187480","title":"C1r-C1s-C1inhibitor (C1rs-C1inh) complex measurements in tears of patients before and after penetrating keratoplasty.","date":"2002","source":"Current eye research","url":"https://pubmed.ncbi.nlm.nih.gov/12187480","citation_count":8,"is_preprint":false},{"pmid":"23583915","id":"PMC_23583915","title":"Identification of a novel and recurrent mutation in the SERPING1 gene in patients with hereditary angioedema.","date":"2013","source":"Clinical immunology (Orlando, Fla.)","url":"https://pubmed.ncbi.nlm.nih.gov/23583915","citation_count":8,"is_preprint":false},{"pmid":"37716525","id":"PMC_37716525","title":"Acquired Angioedema Due to C1-Inhibitor Deficiency (AAE-C1-INH)-A Bicenter Retrospective Study on Diagnosis, Course, and Therapy.","date":"2023","source":"The journal of allergy and clinical immunology. In practice","url":"https://pubmed.ncbi.nlm.nih.gov/37716525","citation_count":8,"is_preprint":false},{"pmid":"33437182","id":"PMC_33437182","title":"Genetic variants of SERPING1 gene in Polish patients with hereditary angioedema due to C1 inhibitor deficiency.","date":"2020","source":"Central-European journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/33437182","citation_count":7,"is_preprint":false},{"pmid":"9412721","id":"PMC_9412721","title":"The presence of a C1-inhibitor-like molecule (C1-INH-L) on human sperm: its involvement in sperm motility.","date":"1997","source":"American journal of reproductive immunology (New York, N.Y. : 1989)","url":"https://pubmed.ncbi.nlm.nih.gov/9412721","citation_count":7,"is_preprint":false},{"pmid":"16617246","id":"PMC_16617246","title":"Haploinsufficiency due to deletion within the 3'-UTR of C1-INH-gene associated with hereditary angioedema.","date":"2006","source":"Genetics in medicine : official journal of the American College of Medical Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/16617246","citation_count":7,"is_preprint":false},{"pmid":"25477154","id":"PMC_25477154","title":"Stability of murine bradykinin type 2 receptor despite treatment with NO, bradykinin, icatibant, or C1-INH.","date":"2014","source":"Allergy","url":"https://pubmed.ncbi.nlm.nih.gov/25477154","citation_count":7,"is_preprint":false},{"pmid":"1864632","id":"PMC_1864632","title":"C1-INH defect as an example of deficiency disease.","date":"1991","source":"Immunological investigations","url":"https://pubmed.ncbi.nlm.nih.gov/1864632","citation_count":7,"is_preprint":false},{"pmid":"39272138","id":"PMC_39272138","title":"Uncovering a novel SERPING1 pathogenic variant: insights into the aggregation of C1-INH in hereditary angioedema.","date":"2024","source":"Orphanet journal of rare diseases","url":"https://pubmed.ncbi.nlm.nih.gov/39272138","citation_count":6,"is_preprint":false},{"pmid":"35873600","id":"PMC_35873600","title":"Searching for Genetic Biomarkers for Hereditary Angioedema Due to C1-Inhibitor Deficiency (C1-INH-HAE).","date":"2022","source":"Frontiers in allergy","url":"https://pubmed.ncbi.nlm.nih.gov/35873600","citation_count":6,"is_preprint":false},{"pmid":"33914953","id":"PMC_33914953","title":"Evidence for a dominant-negative effect of a missense mutation in the SERPING1 gene responsible for hereditary angioedema type I.","date":"2021","source":"The Journal of dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/33914953","citation_count":6,"is_preprint":false},{"pmid":"30923640","id":"PMC_30923640","title":"Identification and Mapping of a 2,009-bp DNA Deletion in SERPING1 of a Hereditary Angioedema Patient.","date":"2019","source":"Case reports in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30923640","citation_count":6,"is_preprint":false},{"pmid":"27826968","id":"PMC_27826968","title":"A Case of Type 2 Hereditary Angioedema With SERPING1 Mutation.","date":"2017","source":"Allergy, asthma & immunology research","url":"https://pubmed.ncbi.nlm.nih.gov/27826968","citation_count":6,"is_preprint":false},{"pmid":"38371394","id":"PMC_38371394","title":"HME, NFE, and HAE-1 efflux pumps in Gram-negative bacteria: a comprehensive phylogenetic and ecological approach.","date":"2024","source":"ISME communications","url":"https://pubmed.ncbi.nlm.nih.gov/38371394","citation_count":5,"is_preprint":false},{"pmid":"37509591","id":"PMC_37509591","title":"The Effects of Serping1 siRNA in α-Synuclein Regulation in MPTP-Induced Parkinson's Disease.","date":"2023","source":"Biomedicines","url":"https://pubmed.ncbi.nlm.nih.gov/37509591","citation_count":5,"is_preprint":false},{"pmid":"33292549","id":"PMC_33292549","title":"Hereditary angioedema caused by a premature stop codon mutation in the SERPING1 gene.","date":"2020","source":"Clinical and translational allergy","url":"https://pubmed.ncbi.nlm.nih.gov/33292549","citation_count":5,"is_preprint":false},{"pmid":"32445210","id":"PMC_32445210","title":"Novel homozygous variants in the SERPING1 gene in two Turkish families with hereditary angioedema of recessive inheritance.","date":"2020","source":"Immunology and cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/32445210","citation_count":5,"is_preprint":false},{"pmid":"38486718","id":"PMC_38486718","title":"Complex analysis of the national Hereditary angioedema cohort in Slovakia - Identification of 12 novel variants in SERPING1 gene.","date":"2024","source":"The World Allergy Organization journal","url":"https://pubmed.ncbi.nlm.nih.gov/38486718","citation_count":5,"is_preprint":false},{"pmid":"31616213","id":"PMC_31616213","title":"A hereditary angioedema screening in two villages, based on an index case, and identification of a novel mutation, \"1033G>T\", at the SERPING1 gene.","date":"2019","source":"Postepy dermatologii i alergologii","url":"https://pubmed.ncbi.nlm.nih.gov/31616213","citation_count":5,"is_preprint":false},{"pmid":"25053016","id":"PMC_25053016","title":"Expression of the SERPING1 gene is not regulated by promoter hypermethylation in peripheral blood mononuclear cells from patients with hereditary angioedema due to C1-inhibitor deficiency.","date":"2014","source":"Orphanet journal of rare diseases","url":"https://pubmed.ncbi.nlm.nih.gov/25053016","citation_count":5,"is_preprint":false},{"pmid":"36941878","id":"PMC_36941878","title":"Effects of C1-INH Treatment on Neurobehavioral Sequelae and Late Seizures After Traumatic Brain Injury in a Mouse Model of Controlled Cortical Impact.","date":"2023","source":"Neurotrauma reports","url":"https://pubmed.ncbi.nlm.nih.gov/36941878","citation_count":4,"is_preprint":false},{"pmid":"38985256","id":"PMC_38985256","title":"Glycogenolysis-Induced Astrocytic Serping1 Expression Regulates Neuroinflammatory Effects on Hippocampal neuron.","date":"2024","source":"Molecular neurobiology","url":"https://pubmed.ncbi.nlm.nih.gov/38985256","citation_count":4,"is_preprint":false},{"pmid":"29623547","id":"PMC_29623547","title":"First Analysis of SERPING1 Gene in Patients with Hereditary Angioedema in Colombia Reveals Two Genotypic Variants in a Highly Symptomatic Individual.","date":"2018","source":"Journal of clinical immunology","url":"https://pubmed.ncbi.nlm.nih.gov/29623547","citation_count":4,"is_preprint":false},{"pmid":"10607415","id":"PMC_10607415","title":"Complement component 1 inhibitor (C1-INH) like protein on murine spermatozoa: anti-C1-INH inhibits in vitro fertilization.","date":"1998","source":"Autoimmunity","url":"https://pubmed.ncbi.nlm.nih.gov/10607415","citation_count":4,"is_preprint":false},{"pmid":"39962118","id":"PMC_39962118","title":"WNT inhibitor SP5-mediated SERPING1 suppresses lung adenocarcinoma progression via TSC2/mTOR pathway.","date":"2025","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/39962118","citation_count":3,"is_preprint":false},{"pmid":"39255718","id":"PMC_39255718","title":"Elevated C1s/C1-INH in serum and plasma of myasthenia gravis patients.","date":"2024","source":"Journal of neuroimmunology","url":"https://pubmed.ncbi.nlm.nih.gov/39255718","citation_count":3,"is_preprint":false},{"pmid":"27187751","id":"PMC_27187751","title":"Frequent life-threatening laryngeal attacks in two Croatian families with hereditary angioedema due to C1 inhibitor deficiency harbouring a novel frameshift mutation in SERPING1.","date":"2016","source":"Annals of medicine","url":"https://pubmed.ncbi.nlm.nih.gov/27187751","citation_count":3,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":52389,"output_tokens":6161,"usd":0.124791},"stage2":{"model":"claude-opus-4-6","input_tokens":9750,"output_tokens":3959,"usd":0.221587},"total_usd":0.346378,"stage1_batch_id":"msgbatch_011rkcQdVV1RaFq9XhcG6df6","stage2_batch_id":"msgbatch_01RzgrJafdF4EWHhj5mNi6dh","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1973,\n      \"finding\": \"C1-INH (SERPING1 product) directly inhibits activated Hageman factor (Factor XII) fragments, blocking their capacity to initiate kinin generation, fibrinolysis, and coagulation. The inhibition is time-dependent and acts on the fragments themselves rather than on downstream effectors (kallikrein or plasmin).\",\n      \"method\": \"In vitro functional inhibition assay with purified C1-INH and Hageman factor fragments; dose-response analysis; gel electrophoresis\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — purified protein in vitro assay with dose-response and mechanistic controls, foundational paper with 195 citations\",\n      \"pmids\": [\"4703226\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1972,\n      \"finding\": \"C1-INH inactivates C1* (the activated C1 complex) and this inactivation is accompanied by loss of C1* activity against C2, TAMe, and ATMe synthetic substrates, without appreciably affecting activity toward C4 or AAMe, indicating that C1-INH-mediated inhibition of C1 involves an allosteric or active-site mechanism selective for certain enzymatic activities.\",\n      \"method\": \"In vitro enzyme activity assays with synthetic substrates; comparison of heat-inactivated vs. C1INH-inactivated C1*\",\n      \"journal\": \"Immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — in vitro assay with functional readouts, single lab single paper\",\n      \"pmids\": [\"5063623\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1981,\n      \"finding\": \"Sialic acid residues on C1-INH are required for normal circulatory half-life; removal of sialic acid by neuraminidase causes rapid hepatic clearance via asialoglycoprotein receptors, while subsequent removal of galactose returns survival to near-normal. C1s inhibitory activity of C1-INH is unimpaired by desialylation, showing sialic acid regulates pharmacokinetics not catalytic function.\",\n      \"method\": \"In vivo rabbit clearance studies; glycosidase treatment; organ distribution of radiolabeled C1-INH; competitive inhibition with asialo-alpha1-acid glycoprotein\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vivo pharmacokinetics with orthogonal biochemical and competitive inhibition controls\",\n      \"pmids\": [\"7451969\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1989,\n      \"finding\": \"In acquired C1-INH deficiency type II, anti-C1-INH autoantibodies drive cleavage of C1-INH at its active site by a target protease without formation of a covalent C1-INH–enzyme complex, generating an Mr 96,000 fragment. NH2-terminal sequence analysis confirmed this cleavage product.\",\n      \"method\": \"NH2-terminal sequence analysis of patient C1-INH fragments; functional assays of C1-INH before and after C1-INH concentrate infusion; SDS-PAGE\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct protein sequencing identifying cleavage site mechanism\",\n      \"pmids\": [\"2723058\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"A naturally occurring mutant C1-INH (from a kindred with incomplete C4 deficiency) inhibits C1s but not C1r, demonstrating that distinct structural determinants on C1-INH mediate inhibition of these two proteases separately. Approximately 50% of C1-INH molecules from affected members resist trypsin cleavage at Arg444.\",\n      \"method\": \"Functional binding assays with activated C1s and C1r; trypsin cleavage resistance assay; purification from patient plasma\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — functional biochemical dissection of differential protease inhibition, replicated on purified protein from patient samples\",\n      \"pmids\": [\"8144914\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"C1INH-Ta, a naturally occurring mutant with deletion of Lys-251, forms no covalent complex with C1s, C1r, or kallikrein (inefficient complex with beta-FXIIa only), and instead undergoes partial substrate cleavage by each protease. The mutation causes a folding abnormality with two populations: one susceptible to multimerization (expressing neoepitopes normally exposed only on protease-complexed C1-INH) and one converted to a substrate with residual inhibitory activity.\",\n      \"method\": \"In vitro protease complex formation assay with recombinant protein expressed in COS cells; SDS-PAGE; Superose 12 size fractionation; thermal stability analysis; epitope mapping\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted recombinant protein, multiple orthogonal assays including size fractionation and mutagenesis-equivalent natural variant\",\n      \"pmids\": [\"8798678\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Anti-C1-INH autoantibodies prevent formation of the stable covalent C1s–C1-INH complex by converting C1-INH to a substrate; in the presence of autoantibodies C1s cleaves C1-INH without forming a covalent bond. Autoantibodies act prior to enzyme-inhibitor complex formation and do not dissociate pre-formed complexes. The epitopes recognized map to C1-INH residues 438-459.\",\n      \"method\": \"SDS-PAGE; hydrolysis of synthetic ester substrate; affinity-purified autoantibodies from two patients; peptide competition assays\",\n      \"journal\": \"Molecular medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro mechanistic assay with purified components, peptide mapping, two patient sources\",\n      \"pmids\": [\"9508789\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"A C1-INH-like molecule (C1-INH-L) is present on the surface of human sperm, anchored to the plasma membrane (trypsin-sensitive, resistant to PIPLC/EDTA/acid), localizes to head and midpiece, and is present on both uncapacitated and capacitated sperm. Anti-C1-INH antibodies reduce sperm motility and progressive velocity in the absence of complement.\",\n      \"method\": \"Western blot; ELISA; immunofluorescence; computerized sperm motion analysis with anti-C1-INH IgG treatment\",\n      \"journal\": \"American journal of reproductive immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct localization with functional consequence (motility reduction), single lab\",\n      \"pmids\": [\"9412721\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"C1-INH-like protein on murine spermatozoa (MW ~100 kDa) localizes to sperm head and midpiece. Anti-C1-INH antibody treatment reduces murine sperm motility, in vitro fertilization rates, and embryo development rates, establishing a functional role for this protein in reproduction.\",\n      \"method\": \"Western blot; immunofluorescence; in vitro fertilization assay with anti-C1-INH antibody; sperm motility assay\",\n      \"journal\": \"Autoimmunity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional in vitro assay with specific antibody, loss-of-function phenotype\",\n      \"pmids\": [\"10607415\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"A deletion mutant of C1-INH lacking the N-terminal 1-99 amino acids (delta-1-99AA) is expressed on xenogeneic cell surfaces (unlike other deletion mutants which remain cytoplasmic), and this surface-bound form blocks human complement-mediated cell lysis (~57-90%) by suppressing both C4 and C3 deposition (~40% each), demonstrating that cell-surface C1-INH can inhibit complement through a distinct mechanism from DAF.\",\n      \"method\": \"Transfection of deletion mutant constructs in CHO cells and pig endothelial cells; flow cytometry for C4 and C3 deposition; complement-mediated lysis assay\",\n      \"journal\": \"Xenotransplantation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional mutagenesis with direct mechanistic readout of complement inhibition\",\n      \"pmids\": [\"12588646\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Polyanions (dextran sulfate, heparin) bind directly to C1s and modulate its proteolytic activity biphasically (enhancement at low concentration, inhibition at higher concentration). Acceleration of the C1s–SERPING1 reaction by polyanions requires both protease-polyanion and serpin-polyanion interactions; a chimeric alpha1-antitrypsin with SERPING1 RCL residues that inhibits C1s but cannot bind polyanions showed that the DXS-mediated acceleration correlates with DXS effects on C1s activity, demonstrating that polyanion-C1s interaction contributes to the acceleration mechanism.\",\n      \"method\": \"In vitro association rate assay with chimeric serpin mutant; protease activity assays with synthetic substrates; binding studies with DXS and heparin\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro system, chimeric mutant as mechanistic probe, multiple substrates\",\n      \"pmids\": [\"19522701\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Knockdown or knockout of Serping1 in mice impairs neuronal stem cell proliferation and delays radial neuronal migration in the developing cortex, with both cell-autonomous and non-cell-autonomous effects. The migration defect is rescued by expression of cleaved C3 protein components or a dual C3aR/C5aR agonist, placing Serping1 upstream of complement C3 activation and C5a receptor signaling in cortical development.\",\n      \"method\": \"In utero electroporation knockdown; Serping1 knockout mice; neuronal migration assays; rescue with cleaved C3 protein or C3aR/C5aR agonist\",\n      \"journal\": \"Frontiers in cellular neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in vivo with multiple rescue experiments placing SERPING1 upstream of complement signaling in cortical migration\",\n      \"pmids\": [\"28670268\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"A subset of HAE-causing SERPING1 variants encoded by mutant alleles exert a dominant-negative effect on wild-type C1-INH secretion by triggering protein-protein interactions between normal and mutant C1-INH, leading to intracellular aggregation and retention in the endoplasmic reticulum (ER). This ER trapping was observed in fibroblasts from a heterozygous carrier and was ameliorated by viral delivery of the SERPING1 gene.\",\n      \"method\": \"Cell transfection; co-immunoprecipitation; immunofluorescence localization; fibroblast cultures from patient; AAV gene delivery rescue experiment\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (co-IP, localization, patient cells, gene rescue), Strong evidence for dominant-negative ER retention mechanism\",\n      \"pmids\": [\"30398465\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Serping1/C1-INH is secreted by renal tubular cells through a mitophagy-dependent mechanism; high-dose ascorbate stimulates tubular secretion of SerpinG1 via NRF2 transactivation. Secreted SerpinG1 promotes anti-inflammatory M2 macrophage polarization and prevents septic acute kidney injury. Kidney-specific SerpinG1 knockdown (AAV9-shRNA) abolishes these protective effects.\",\n      \"method\": \"FACS; RNA-sequencing; GSEA; luciferase reporter; ChIP assay; AAV9 gene knockdown in kidney-specific manner; co-culture systems; Atg7 conditional knockout mice\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple mechanistic methods including in vivo KO and ChIP, single lab\",\n      \"pmids\": [\"35982894\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SERPING1-encoded C1-INH forms covalent complexes with C1s (classical pathway) and MASP-1 (lectin pathway); measurement of C1s/C1-INH and MASP-1/C1-INH complexes by sandwich ELISA distinguishes early classical from early lectin pathway complement activation. Both complex levels are elevated in COVID-19 patients.\",\n      \"method\": \"Sandwich ELISA development and validation; zymosan activation of complement; clinical sample measurement in 414 COVID-19 patients and 96 healthy controls\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — validated immunoassay with functional activation control, identifies specific covalent complexes, single lab\",\n      \"pmids\": [\"36420270\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"For a large set of HAE-causing SERPING1 variants (28 tested), coexpression of mutant and normal C1INH negatively affects the overall capacity to target proteases (dominant-negative trans-inhibition). A subset of variants drive intracellular C1INH foci formation only in heterozygous configurations (requiring simultaneous expression of normal and mutant C1INH), identifying distinct molecular disease mechanisms including serpinopathy-type aggregation.\",\n      \"method\": \"Transfection of HeLa cells with 28 SERPING1 variant constructs; comparative studies of C1INH expression, secretion, functionality, and intracellular localization; co-expression of wild-type and mutant constructs\",\n      \"journal\": \"The Journal of allergy and clinical immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic functional characterization of 28 variants with orthogonal assays (expression, secretion, function, localization), provides mechanistic classification\",\n      \"pmids\": [\"37301409\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A missense SERPING1 mutation p.S150F produces a C1INH protein that is stably expressed intracellularly but not secreted, and when coexpressed with wild-type C1INH it prevents secretion of wild-type C1INH and promotes intracellular degradation of the wild-type protein through protein-protein interaction, demonstrating dominant-negative disease mechanism.\",\n      \"method\": \"In vitro cell transfection with mutant and wild-type constructs; secretion assay; co-expression experiments; intracellular degradation assay\",\n      \"journal\": \"The Journal of dermatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mechanistic in vitro co-expression experiments demonstrating dominant-negative effect, single lab\",\n      \"pmids\": [\"33914953\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Homozygous SERPING1 variant S438F (in the reactive center loop) renders C1INH predominantly in the cleaved/inactive 96-kDa isoform and severely reduces C1INH interaction with target proteases C1s and FXIIa (to 4-8% of controls for FXIIa in homozygotes), while the homozygous I379T variant (in the gate region) shows near-normal heterozygous function but fails to inhibit C1s and FXIIa as a homozygote, demonstrating region-specific mechanisms of C1INH dysfunction.\",\n      \"method\": \"Functional protease binding assays measuring C1INH-C1s and C1INH-FXIIa complex formation; SDS-PAGE for isoform analysis; patient plasma studies\",\n      \"journal\": \"Immunology and cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional biochemical characterization of natural variants in specific structural domains, patient plasma validation\",\n      \"pmids\": [\"32445210\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"A novel SERPING1 variant c.708T>G leads to accumulation of C1-INH in the endoplasmic reticulum, upregulation of GRP75, calcium (Ca2+) overload, mitochondrial structural and functional disruption, and apoptosis. siRNA knockdown of GRP75 mitigates the calcium overload and mitochondrial damage, placing GRP75 downstream of mutant C1-INH ER retention.\",\n      \"method\": \"Cell transfection with variant construct; ER localization assay; GRP75 Western blot; Ca2+ measurement; mitochondrial assays; siRNA knockdown of GRP75\",\n      \"journal\": \"Orphanet journal of rare diseases\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mechanistic pathway dissection with siRNA rescue, single lab\",\n      \"pmids\": [\"39272138\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"SERPING1 splice site mutations c.51+3A>G and c.51+5G>A cause exon 2 skipping in cell transfection assays using minigene constructs. A polymorphic variant c.-21C at the second base of exon 2 also causes low but significant exon 2 skipping in transfected hepatoma cells, potentially contributing to more severe angioedema. A tissue-specific alternative splicing of exon 3 was observed in monocytes but not liver/hepatoma cells.\",\n      \"method\": \"Minigene transfection assays in HepG2 and Hep 3B cells; RT-PCR analysis; co-segregation analysis in patient family\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — functional splicing assay with minigene constructs and tissue-specific verification\",\n      \"pmids\": [\"16470590\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Glycogenolysis in postnatal astrocytes drives upregulation of Serping1 expression through reactive oxygen species (ROS)-NF-κB signaling pathway. LPS-induced astrocytic Serping1 upregulation is governed by glycogen degradation, and glycogenolysis mediates neurotoxic astrocyte phenotypes including impaired neuronal synaptogenesis.\",\n      \"method\": \"LPS treatment of postnatal hippocampal cells; glycogenolysis activation/inhibition; ROS measurement; NF-κB pathway analysis; neuronal synaptogenesis assays\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mechanistic pathway dissection with specific inhibitors, single lab\",\n      \"pmids\": [\"38985256\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"High levels of C1INH secreted by IL-1β/TNF-α/IFN-γ-reprogrammed mesenchymal stem cells (ITI-hUC-MSCs) prevent inflammation-induced profibrotic CD301+ macrophage polarization by downregulating the JAK-STAT signaling pathway, thereby reducing endometrial fibrosis.\",\n      \"method\": \"FACS for macrophage polarization; RNA-seq; functional co-culture assays; ITI-hUC-MSC secretome analysis; IUA mouse model\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional in vivo and in vitro experiments with mechanistic pathway identification (JAK-STAT), single lab\",\n      \"pmids\": [\"37456855\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Retinal pigment epithelium (RPE) cells upregulate C1INH expression in co-cultured bone marrow-derived macrophages, suggesting a paracrine mechanism by which RPE modulates complement regulatory expression at the retina-choroidal interface. Under inflammatory conditions (TNF-α-treated RPE), C1INH expression in macrophages is further enhanced.\",\n      \"method\": \"Co-culture of BMDMs with RPE cells/eyecups; real-time RT-PCR of complement gene expression\",\n      \"journal\": \"Aging\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — gene expression in co-culture without direct protein-level or pathway mechanistic validation\",\n      \"pmids\": [\"29905533\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SP5 (WNT inhibitor/transcription factor) facilitates SERPING1 transcription by binding to the SERPING1 gene promoter. SERPING1 suppresses lung adenocarcinoma cell proliferation, migration, and invasion via the TSC2/mTOR pathway.\",\n      \"method\": \"Luciferase reporter assay; ChIP assay; in vivo and in vitro LUAD cell assays; Mendelian randomization; multi-omics\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP and luciferase reporter for promoter binding, in vivo functional assays for pathway placement, single lab\",\n      \"pmids\": [\"39962118\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SERPING1 encodes C1 inhibitor (C1-INH), a serine protease inhibitor (serpin) that forms irreversible covalent complexes with and inactivates multiple proteases including C1r, C1s, MASP-1, activated Factor XII (Hageman factor), and plasma kallikrein, thereby controlling the classical and lectin complement pathways and the contact/kallikrein-kinin system; sialic acid residues regulate its circulatory half-life via hepatic asialoglycoprotein receptors; polyanions (heparin, dextran sulfate) accelerate C1s inhibition through dual interactions with both C1s and the serpin RCL; disease-causing SERPING1 variants cause C1-INH deficiency either through haploinsufficiency, dominant-negative intracellular aggregation and ER retention, or conversion of C1-INH from an inhibitor to a substrate; and beyond complement regulation, C1-INH plays roles in cortical neuronal migration (upstream of C3/C5aR signaling), macrophage polarization (via JAK-STAT suppression), renal tubular immune modulation (via NRF2/mitophagy-dependent secretion), and sperm surface function.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"SERPING1 encodes C1 inhibitor (C1-INH), a serine protease inhibitor (serpin) that controls the classical and lectin complement pathways and the contact/kallikrein-kinin system by forming irreversible covalent complexes with activated C1r, C1s, MASP-1, Factor XII, and plasma kallikrein [PMID:4703226, PMID:5063623, PMID:8144914, PMID:36420270]. Polyanions such as heparin and dextran sulfate accelerate C1-INH inhibition of C1s through dual interactions with both the protease and the serpin reactive center loop, while sialic acid residues on C1-INH regulate its circulatory half-life via hepatic asialoglycoprotein receptor-mediated clearance without affecting inhibitory function [PMID:19522701, PMID:7451969]. Loss-of-function SERPING1 mutations cause hereditary angioedema (HAE) through distinct mechanisms including haploinsufficiency, reactive center loop cleavage converting C1-INH from inhibitor to substrate, and dominant-negative intracellular aggregation wherein mutant C1-INH traps wild-type protein in the endoplasmic reticulum [PMID:8798678, PMID:30398465, PMID:37301409, PMID:32445210]. Beyond complement regulation, C1-INH promotes cortical neuronal migration upstream of C3/C5aR signaling and modulates macrophage polarization through JAK-STAT pathway suppression [PMID:28670268, PMID:37456855].\",\n  \"teleology\": [\n    {\n      \"year\": 1972,\n      \"claim\": \"Establishing that C1-INH directly inactivates the activated C1 complex resolved the identity of the principal inhibitor of classical pathway initiation and showed the inhibition is selective for certain enzymatic activities of C1*.\",\n      \"evidence\": \"In vitro enzyme activity assays with synthetic substrates comparing heat-inactivated vs. C1-INH-inactivated C1*\",\n      \"pmids\": [\"5063623\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of selectivity for C2-cleaving but not C4-cleaving activity was not resolved\", \"Stoichiometry of the C1-INH–C1 interaction was not determined\"]\n    },\n    {\n      \"year\": 1973,\n      \"claim\": \"Demonstrating that C1-INH directly inhibits activated Factor XII fragments established that a single serpin controls both complement and contact/kinin pathways, explaining the dual phenotype (complement consumption and bradykinin generation) in C1-INH deficiency.\",\n      \"evidence\": \"In vitro functional inhibition assay with purified C1-INH and Hageman factor fragments, dose-response analysis\",\n      \"pmids\": [\"4703226\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative physiological contribution of C1-INH vs. other Factor XII inhibitors not quantified\", \"Kinetic parameters for Factor XII inhibition were not determined\"]\n    },\n    {\n      \"year\": 1981,\n      \"claim\": \"Revealing that sialic acid residues govern C1-INH circulatory half-life via hepatic asialoglycoprotein receptors, without affecting inhibitory activity, separated the pharmacokinetic from catalytic determinants of C1-INH function.\",\n      \"evidence\": \"In vivo rabbit clearance studies with glycosidase-treated radiolabeled C1-INH; competitive inhibition with asialo-alpha1-acid glycoprotein\",\n      \"pmids\": [\"7451969\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Role of other glycan modifications (e.g., O-glycans on the N-terminal domain) not addressed\", \"Human in vivo validation not performed\"]\n    },\n    {\n      \"year\": 1989,\n      \"claim\": \"Identifying that autoantibodies in acquired C1-INH deficiency convert C1-INH from an inhibitor to a substrate (cleavage without covalent complex formation) revealed a pathogenic mechanism distinct from genetic deficiency.\",\n      \"evidence\": \"NH2-terminal sequence analysis of patient C1-INH cleavage fragments; SDS-PAGE; functional assays\",\n      \"pmids\": [\"2723058\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for autoantibody-mediated substrate conversion was unknown\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"A natural C1-INH mutant that inhibits C1s but not C1r demonstrated that distinct structural determinants on C1-INH mediate inhibition of different target proteases, establishing that the serpin is not a generic inhibitor but has protease-specific recognition elements.\",\n      \"evidence\": \"Functional binding assays with activated C1s and C1r using purified patient-derived C1-INH; trypsin cleavage resistance at Arg444\",\n      \"pmids\": [\"8144914\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for differential C1r vs. C1s recognition not determined\", \"Whether exosite interactions beyond the RCL contribute was not tested\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Characterization of the C1INH-Ta mutant (ΔLys-251) showed that a single residue deletion converts C1-INH into a substrate for multiple proteases and causes folding abnormalities with multimerization, providing a mechanistic template for serpinopathy-type disease.\",\n      \"evidence\": \"Recombinant protein expressed in COS cells; protease complex formation assays; size fractionation; thermal stability; epitope mapping\",\n      \"pmids\": [\"8798678\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Crystal structure of mutant conformer was not obtained\", \"Whether ER quality control eliminates these misfolded species in vivo was not tested\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Mapping autoantibody epitopes to C1-INH residues 438–459 and showing they block covalent complex formation prior to the enzyme–inhibitor encounter refined understanding of how acquired deficiency mimics the substrate-conversion mechanism seen in certain genetic mutants.\",\n      \"evidence\": \"SDS-PAGE; peptide competition assays with affinity-purified autoantibodies from two patients\",\n      \"pmids\": [\"9508789\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether all acquired C1-INH deficiency autoantibodies share this epitope was not established\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Detection of a C1-INH-like molecule on human and murine sperm surfaces, with antibody-mediated reduction in motility and fertilization, suggested a complement-independent reproductive function for C1-INH.\",\n      \"evidence\": \"Western blot, immunofluorescence, and ELISA on human sperm; computerized motility analysis; murine in vitro fertilization with anti-C1-INH antibody\",\n      \"pmids\": [\"9412721\", \"10607415\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity confirmation by mass spectrometry was not performed\", \"Mechanism by which sperm-surface C1-INH affects motility is unknown\", \"Whether this is the SERPING1 gene product or a cross-reactive protein was not genetically confirmed\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Functional splicing assays demonstrated that specific SERPING1 splice-site mutations cause exon 2 skipping, and a common polymorphism at the exon 2 boundary contributes low-level aberrant splicing, providing a molecular explanation for variable expressivity in HAE families.\",\n      \"evidence\": \"Minigene transfection assays in HepG2/Hep3B cells; RT-PCR; family co-segregation analysis\",\n      \"pmids\": [\"16470590\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative contribution of aberrant splicing to circulating C1-INH levels in vivo not measured\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Using chimeric serpins, polyanion-mediated acceleration of C1s inhibition was shown to require dual interactions with both C1s and the C1-INH RCL, establishing that glycosaminoglycans serve as a template to bridge protease and inhibitor.\",\n      \"evidence\": \"In vitro association rate assays with chimeric alpha1-antitrypsin/C1-INH RCL; protease activity assays; dextran sulfate and heparin binding studies\",\n      \"pmids\": [\"19522701\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological polyanion identity in vivo (heparan sulfate vs. others) not determined\", \"Structural model of the ternary complex lacking\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"In vivo knockout and knockdown of Serping1 impaired cortical neuronal migration, rescued by C3 cleavage products or C3aR/C5aR agonists, placing C1-INH upstream of complement-mediated signaling in brain development — a function unrelated to protease inhibition per se.\",\n      \"evidence\": \"In utero electroporation knockdown; Serping1 knockout mice; rescue with cleaved C3 protein or C3aR/C5aR agonist\",\n      \"pmids\": [\"28670268\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether C1-INH acts by regulating complement activation or through a separate mechanism in the developing brain was not fully resolved\", \"Cell-autonomous vs. non-cell-autonomous contributions not dissected at the molecular level\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Discovery that certain HAE-causing SERPING1 mutants exert dominant-negative effects by physically interacting with wild-type C1-INH and trapping it in the ER explained why some patients have more severe disease than predicted by haploinsufficiency alone.\",\n      \"evidence\": \"Co-immunoprecipitation; immunofluorescence in patient fibroblasts; AAV gene delivery rescue\",\n      \"pmids\": [\"30398465\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"ER stress pathway involvement (UPR activation) not characterized\", \"Proportion of HAE variants acting through this mechanism was unknown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Structure-function analysis of homozygous SERPING1 variants in the reactive center loop (S438F) and gate region (I379T) demonstrated region-specific mechanisms of dysfunction — substrate conversion vs. loss of protease interaction — refining genotype-phenotype correlations.\",\n      \"evidence\": \"Functional protease binding assays (C1s, FXIIa); SDS-PAGE isoform analysis; patient plasma studies\",\n      \"pmids\": [\"32445210\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Crystal structures of gate region mutants not available\", \"Only two variants characterized in detail\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Systematic testing of 28 HAE-causing SERPING1 variants established that dominant-negative trans-inhibition of wild-type C1-INH and serpinopathy-type intracellular aggregation occur specifically in heterozygous configurations, providing a mechanistic classification framework for HAE variants.\",\n      \"evidence\": \"Transfection of HeLa cells with 28 SERPING1 variant constructs; co-expression studies measuring expression, secretion, function, and localization\",\n      \"pmids\": [\"37301409\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo validation of variant classification not performed\", \"Whether therapeutic chaperones could rescue ER-retained variants not tested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identification that C1-INH suppresses profibrotic macrophage polarization via JAK-STAT pathway downregulation extended C1-INH function beyond protease inhibition to immune cell reprogramming.\",\n      \"evidence\": \"FACS; RNA-seq; co-culture and in vivo mouse model of intrauterine adhesion\",\n      \"pmids\": [\"37456855\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct molecular target of C1-INH in JAK-STAT suppression not identified\", \"Whether this is protease-inhibition-dependent or independent is unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"A novel SERPING1 variant was shown to cause ER retention that triggers GRP75-mediated calcium overload, mitochondrial damage, and apoptosis, linking C1-INH misfolding to mitochondrial pathology beyond simple loss of secretion.\",\n      \"evidence\": \"ER localization assay; GRP75 Western blot; calcium measurement; mitochondrial assays; siRNA knockdown rescue\",\n      \"pmids\": [\"39272138\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether GRP75-mediated mitochondrial damage is a general feature of ER-retained C1-INH variants or specific to this mutation is unknown\", \"In vivo relevance of apoptosis pathway in HAE pathology not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis of C1-INH's differential protease specificity, the molecular mechanism by which C1-INH modulates JAK-STAT and mTOR signaling independent of protease inhibition, and whether therapeutic chaperones or gene therapy can rescue dominant-negative SERPING1 variants in vivo.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No high-resolution structure of C1-INH in complex with C1r, C1s, or MASP-1\", \"Protease-independent signaling mechanisms not molecularly defined\", \"In vivo rescue of dominant-negative variants not demonstrated in animal models\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 4, 5, 10, 14, 17]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 5, 6, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [2, 9, 13, 14]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [12, 15, 16, 18]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [7, 8, 9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 1, 4, 10, 11, 14]},\n      {\"term_id\": \"R-HSA-109582\", \"supporting_discovery_ids\": [0, 17]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [3, 5, 6, 12, 15, 17, 18]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [11]}\n    ],\n    \"complexes\": [\n      \"C1-INH–C1s covalent complex\",\n      \"C1-INH–MASP-1 covalent complex\",\n      \"C1-INH–FXIIa covalent complex\"\n    ],\n    \"partners\": [\n      \"C1S\",\n      \"C1R\",\n      \"MASP1\",\n      \"F12\",\n      \"KLKB1\",\n      \"GRP75\",\n      \"SP5\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}