{"gene":"MASP1","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":2001,"finding":"MASP-3 is generated through alternative splicing of the MASP-1/3 gene and associates with larger MBL oligomers together with MASP-2, while MASP-1 associates with smaller oligomers. MASP-3 downregulates the C4 and C2 cleaving activity of MASP-2.","method":"Molecular cloning, MBL complex fractionation, functional complement assays","journal":"Immunity","confidence":"High","confidence_rationale":"Tier 2 / Strong — identification of novel splice product with biochemical characterization of complex composition and functional inhibition assay; widely replicated","pmids":["11485744"],"is_preprint":false},{"year":2009,"finding":"MAp44, a fourth product of the MASP1/3 gene (sharing CUB1-EGF-CUB2-CCP1 domains with MASP-1 and MASP-3 but with a unique 17 aa C-terminus), circulates in Ca2+-dependent complexes with MBL and ficolins (KD ~0.6 nM for MBL) and competes with MASP-2 for binding to MBL and ficolins, thereby inhibiting complement activation.","method":"Surface plasmon resonance, ELISA, complement activation inhibition assays","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — SPR binding kinetics, competition assay, and functional complement inhibition; replicated by multiple labs","pmids":["19917686"],"is_preprint":false},{"year":2012,"finding":"In normal human serum, MASP-1 is the exclusive activator of MASP-2; MASP-2 autoactivation is strictly dependent on prior activation by MASP-1, and MASP-1 inhibition prevents MASP-2 autoactivation. Additionally, MASP-1 contributes ~60% of C2a formation responsible for C3 convertase assembly.","method":"Monospecific inhibitor proteins against MASP-1 and MASP-2 used in functional lectin pathway assays with normal human serum","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — unique monospecific inhibitors with orthogonal biochemical assays; widely replicated by independent groups","pmids":["22691502"],"is_preprint":false},{"year":2008,"finding":"MASP-1 contributes to lectin pathway activation, primarily by promoting MASP-2 activation. MASP-1/3-deficient mouse serum shows significantly reduced C4 and C3 deposition on mannan, which is restored by reconstitution with recombinant MASP-1. MASP-1 promotes MASP-2 activation in deficient serum.","method":"Gene-targeted MASP1/3−/− mouse model, serum complement activity assays, reconstitution with recombinant MASP-1","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO mouse with reconstitution experiment; replicated across labs","pmids":["18424734"],"is_preprint":false},{"year":2012,"finding":"In a MASP-1/MASP-3-deficient human patient (nonsense mutation in common MASP1 exon), the lectin pathway is nonfunctional but the alternative pathway functions normally. Reconstitution with MASP-1 restores lectin pathway activity through direct activation of MASP-2. MASP-1 and MASP-2 can co-associate in the same MBL complex (co-complexes found in serum), enabling transactivation.","method":"Patient serum studies, complement pathway activity assays, reconstitution, ELISA co-complex detection","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — human genetic deficiency with reconstitution and mechanistic follow-up; complements mouse KO data","pmids":["22966085"],"is_preprint":false},{"year":2009,"finding":"Crystal structure of active MASP-1 catalytic region resolved at 2.55 Å reveals a wide substrate-binding groove resembling trypsin rather than early complement proteases, an unusual internal salt bridge between S1 Asp189 and Arg224, and a very long 60-loop, explaining MASP-1's broad/relaxed substrate specificity.","method":"X-ray crystallography (2.55 Å resolution)","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional interpretation; foundational structural paper","pmids":["19564340"],"is_preprint":false},{"year":2016,"finding":"MASP-3 is the exclusive activator of pro-factor D in resting blood. Using evolved monospecific MASP-1 and MASP-3 inhibitors, neither MASP-1 nor MASP-2 activates pro-FD in resting blood, but MASP-3 inhibition abolishes pro-FD maturation, demonstrating a fundamental link between the lectin and alternative complement pathways.","method":"Evolved monospecific MASP inhibitors applied to resting blood; pro-FD activation assays; in vitro kinetics","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — specific inhibitors with multiple orthogonal assays; confirmed by independent groups using MASP-3 KO mice","pmids":["27535802"],"is_preprint":false},{"year":2009,"finding":"MASP-1 activates Ca2+ signaling, NF-κB, and p38 MAPK pathways in human endothelial cells (HUVECs) through cleavage of PAR4 (protease-activated receptor 4). Activation requires proteolytic activity of MASP-1; MASP-2 has no such effect. Membrane-bound intact PAR4 decreases after MASP-1 treatment.","method":"Cell signaling assays (Ca2+ imaging, western blot for NF-κB/p38 MAPK), synthetic PAR peptide substrate cleavage assays, mRNA quantification, flow cytometry","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (Ca2+ signaling, NF-κB, p38, PAR4 cleavage assay, receptor downregulation); replicated in subsequent studies","pmids":["19667088"],"is_preprint":false},{"year":2008,"finding":"Crystal structure of the CUB1-EGF-CUB2 domain of human MASP-1/3 resolved at 2.3 Å. The structure shows a head-to-tail homodimer stabilized by hydrophobic interactions and Ca2+ ions. Point mutagenesis of 27 residues in MASP-3 identified two homologous binding sites (on CUB1 and CUB2) for MBL and ficolins, located near Ca2+-binding sites, involving a major electrostatic interaction between acidic Ca2+ ligands of MASP-1/3 and a conserved lysine of MBL.","method":"X-ray crystallography (2.3 Å), site-directed mutagenesis, surface plasmon resonance","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure combined with mutagenesis and binding kinetics","pmids":["18596036"],"is_preprint":false},{"year":2013,"finding":"MASP-1 autoactivation rate is ~3000-fold higher than MASP-2 autoactivation; both activated and zymogen MASP-1 cleave proenzyme MASP-2 efficiently; MASP-1 also cleaves MASP-3 proenzyme. Crystal structure of proenzyme MASP-1 R448Q at 2.5 Å shows zymogen MASP-1 fluctuates between inactive and active-like conformations, explaining its unusually high zymogen activity.","method":"Rate constant measurements with zymogen and active-site mutant recombinant proteins, X-ray crystallography (2.5 Å), kinetic modeling","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — quantitative kinetics with mutagenesis and crystal structure in single study","pmids":["23386610"],"is_preprint":false},{"year":2012,"finding":"MASP-1 and MASP-2 are both essential for lectin pathway activation. A monospecific MASP-1 inhibitor completely blocks lectin pathway activation. Crystal structures of Michaelis-like complexes of MASP-1 and MASP-2 with substrate-like inhibitors resolved at 1.28 Å (MASP-2) reveal significant plasticity of MASP-2.","method":"Evolved monospecific inhibitors, complement activation assays, X-ray crystallography","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — monospecific inhibitors with crystal structures; orthogonal validation of MASP-1 essentiality","pmids":["22511776"],"is_preprint":false},{"year":2004,"finding":"MASP-1 cleaves fluorescent amide substrates with preference for Phe-Gly-Arg-AMC (rate 16.8 nmol/min/µg). C1 inhibitor inhibits both MASP-1 and MASP-2 (though complexes are unstable at alkaline pH). The thrombin inhibitor boroMpg inhibits MASP-1 but not MASP-2, and antithrombin III with heparin inhibits both MASPs.","method":"In vitro enzyme assays with fluorescent amide substrates, inhibitor profiling","journal":"Molecular immunology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — rigorous in vitro enzymatic characterization with multiple substrates and inhibitors","pmids":["14725788"],"is_preprint":false},{"year":2008,"finding":"MASP-1 cleaves factor XIII A-chain and fibrinogen beta-chain at identical sites to thrombin, but with ~650-fold lower turnover rate. MASP-1 cleavage of fibrinogen releases proinflammatory fibrinopeptide B (not fibrinopeptide A as thrombin does for the alpha-chain). MASP-1 can drive formation of cross-linked fibrinogen.","method":"In vitro cleavage assays, SDS-PAGE, N-terminal sequencing, comparison with thrombin","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with site identification and quantitative comparison; replicated in subsequent studies","pmids":["18456010"],"is_preprint":false},{"year":2011,"finding":"MASP-1 cleaves high-molecular-weight kininogen (HK) to release bradykinin (BK). MASP-2 also cleaves HK but cannot release BK. Catalytic efficiency of HK cleavage by recombinant MASP-1 is ~4.0×10² M⁻¹s⁻¹. C1-inhibitor prevents HK cleavage by MASP-1.","method":"Differential gel electrophoresis proteomics, SDS-PAGE, HPLC for BK detection, kinetic measurements","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with multiple orthogonal detection methods and kinetics quantified","pmids":["21625439"],"is_preprint":false},{"year":2012,"finding":"MASP-1 activates factor XIII, prothrombin (generating F1+2 fragments), fibrinogen (generating fibrinopeptide A via thrombin), and TAFI in citrated plasma and purified systems. MASP-1 induces clot formation and affects fibrin clot structure in NCP; it prolongs clot lysis. MASP-1-induced fibrin formation is thrombin-dependent but MASP-1 directly activates prothrombin.","method":"FXIII incorporation assay, specific cleavage product assays, turbidimetric clot assay, scanning electron microscopy","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple in vitro assays with purified and plasma-based systems; replicated by same group and others","pmids":["22536427"],"is_preprint":false},{"year":2015,"finding":"MASP-1 cleaves prothrombin at three sites (R155, R271, R393) identified by N-terminal sequencing, promotes clot formation in whole blood and platelet-poor plasma (measured by thrombelastography), and shortens clotting time. MASP-1-induced clotting requires prothrombin in a purified system.","method":"SDS-PAGE, N-terminal sequencing, thrombelastography, purified system reconstitution","journal":"Molecular immunology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with site identification; extends prior coagulation findings","pmids":["25745807"],"is_preprint":false},{"year":2015,"finding":"MASP-1 activates prothrombin via two simultaneous pathways (cleaving R271 or R393 first), generating active alternative thrombin species. Both R393 and R320 are required for prothrombin activation by MASP-1; R155 is not an important cleavage site.","method":"Arginine-to-glutamine prothrombin mutants, SDS-PAGE, N-terminal sequencing, thrombelastography","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mutagenesis of prothrombin with in vitro reconstitution and functional clotting assay","pmids":["26645987"],"is_preprint":false},{"year":2014,"finding":"MASP-1 induces IL-6 and IL-8 (but not IL-1α, IL-1ra, TNFα, MCP-1) production in HUVECs through the p38-MAPK pathway, and the conditioned medium triggers neutrophil chemotaxis.","method":"Cytokine ELISA, p38-MAPK pathway inhibition, neutrophil chemotaxis assay","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal assays (cytokine measurement, pathway inhibition, functional chemotaxis), single lab","pmids":["24489848"],"is_preprint":false},{"year":2016,"finding":"MASP-1 activates endothelial cells to up-regulate E-selectin expression and decrease ICAM-2, resulting in increased adhesion between endothelial cells and neutrophil granulocytes. ICAM-1, VCAM-1, and P-selectin remain unchanged.","method":"Flow cytometry for adhesion molecules on HUVECs, adhesion assay with differentiated PLB-985 cells","journal":"Molecular immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — single lab, clean functional assay but single-method per endpoint","pmids":["27219453"],"is_preprint":false},{"year":2019,"finding":"MASP-1 increases endothelial paracellular permeability through PAR1-mediated intracellular Ca2+ mobilization, Rho-kinase activation, myosin light chain phosphorylation, cytoskeletal actin rearrangement, and disruption of interendothelial junctions. MASP-1 also up-regulates bradykinin B2 receptor expression in HUVECs.","method":"Real-time electric impedance sensing, XperT permeability assay, Ca2+ imaging, Rho-kinase inhibition, whole-transcriptome microarray","journal":"Frontiers in immunology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (impedance, permeability, Ca2+, kinase, transcriptome) in single study","pmids":["31130964"],"is_preprint":false},{"year":2014,"finding":"Serum MASP-1 in complex with MBL (native lectin pathway complexes) activates endothelial cells (Ca2+ signaling). Among MBL-associated components, only MASP-1 triggers this response; MASP-2, MASP-3, non-enzymatic domains of MASP-1/MASP-2, and zymogen MASP-1 mutant are all ineffective, indicating proteolytic activity of MASP-1 is required.","method":"Ca2+ signaling assay in HUVECs with native serum MBL-MASP complexes and recombinant fragments/mutants","journal":"Molecular immunology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — systematic comparison of native and recombinant components with enzymatic activity requirement demonstrated","pmids":["24472859"],"is_preprint":false},{"year":2011,"finding":"MASP-1 mutations in the MASP1 gene (shared exons encoding both MASP-1 and MASP-3, or isoforms affecting only MASP-3) cause 3MC syndrome (Carnevale, Malpuech, Michels, Mingarelli). A missense mutation p.G687R and a nonsense mutation p.W290X both cosegregate with the syndrome phenotype in consanguineous families.","method":"Exome sequencing, Sanger sequencing, homozygosity mapping, cosegregation analysis","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic linkage with cosegregation; no in vitro functional reconstitution in this paper","pmids":["21035106"],"is_preprint":false},{"year":2011,"finding":"COLEC11 and MASP1 mutations cause 3MC syndrome. CL-K1 (encoded by COLEC11) serves as a guidance cue for neural crest cell migration; zebrafish morphants for either gene develop pigmentary defects and severe craniofacial abnormalities, demonstrating a role for lectin complement pathway factors in neural crest-dependent developmental processes.","method":"Human genetics (mutation identification), zebrafish morpholino knockdown, craniofacial phenotype analysis, neural crest cell migration assay","journal":"Nature genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — zebrafish loss-of-function with specific developmental phenotype; mechanistic link for MASP1 in development is indirect (via CL-K1)","pmids":["21258343"],"is_preprint":false},{"year":2013,"finding":"MASP-1 and MASP-2 do not directly form heterodimers, but addition of MBL or ficolins enables formation of MASP-1/MASP-2 co-complexes in serum. These co-complexes have a functional role in activating complement; MAp44 inhibits complement not only by displacing MASP-2 from MBL/ficolins but by disrupting MASP-1/MASP-2 co-complexes and impairing transactivation.","method":"Gel filtration, ELISA co-complex detection in serum, functional complement activation assays with defined MBL/ficolin complexes","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical co-complex detection with functional validation, single lab","pmids":["23785123"],"is_preprint":false},{"year":2014,"finding":"MASP-1 and MASP-2 can form heterodimers via their CUB1-EGF-CUB2 regions after Ca2+-mediated dissociation and re-association. Heterodimer formation between MASP-1 and MASP-3 subunits occurs even in the presence of Ca2+. Both MASP-1 and MASP-2 form tight Ca2+-dependent homodimers.","method":"Size exclusion chromatography, native PAGE, EDTA dissociation/re-association kinetics with recombinant CUB1-EGF-CUB2 fragments","journal":"Molecular immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical characterization with defined recombinant fragments, single lab","pmids":["24424083"],"is_preprint":false},{"year":2015,"finding":"MASP-1 and MASP-2 do not activate pro-factor D in resting human plasma/serum. MASP-3 is the most likely physiological activator of pro-FD; selective MASP-1 and MASP-2 inhibitors do not reduce pro-FD activation, whereas a high concentration MASP-2 inhibitor (which also weakly inhibits MASP-3) slows activation, and added recombinant MASP-3 reduces pro-FD half-life.","method":"Fluorescently labeled pro-FD activation assay in serum/plasma, selective MASP inhibitors, kinetic measurements with purified enzymes","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — quantitative kinetics with specific inhibitors and novel pro-FD assay; consistent with companion study PMID 27535802","pmids":["26673137"],"is_preprint":false},{"year":2019,"finding":"MASP-3, but not MASP-1, activates pro-factor D under physiological conditions in mice. Mice monospecifically deficient in MASP-1 lack lectin pathway activity but have normal alternative pathway with active FD, whereas MASP-3-deficient mice lack alternative pathway activity with zymogenic FD present. MASP-3 circulates predominantly as an active form.","method":"Monospecific MASP-1-KO and MASP-3-KO mouse generation, complement pathway activity assays, FD zymogen detection","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean monospecific KO mice with direct pathway activity measurement; confirmatory of in vitro inhibitor studies","pmids":["31399515"],"is_preprint":false},{"year":2017,"finding":"3MC-associated MASP-3 mutations all yield enzymatically inactive MASP-3 protein. In MASP-3-depleted human serum, sera from 3MC patients, and Masp1/3−/− mice, lack of enzymatically active MASP-3 compromises pro-FD-to-FD conversion, confirming MASP-3 as an important maturase of factor D in the alternative pathway. 3MC patients contain predominantly pro-FD but also detectable mature FD, indicating MASP-3-independent maturation also occurs.","method":"Isoelectric focusing of endogenous FD variants, enzymatic characterization of mutant MASP-3 proteins, MASP-3-depleted human serum assays, patient sera, KO mice","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — human genetics, biochemical characterization of mutants, depleted serum, and KO mice as orthogonal approaches","pmids":["28794230"],"is_preprint":false},{"year":2018,"finding":"MASP-1 is essential for LPS-induced alternative pathway (AP) activation but has little effect on zymosan-induced AP activation. MASP-1 inhibition (by SGMI-1 and other inhibitors with different mechanisms) prevents AP activation on LPS surfaces and attenuates already-initiated AP activity.","method":"Specific MASP-1 inhibitors (SGMI-1 and others) in AP complement activation assays on LPS and zymosan surfaces","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — specific inhibitors with multiple mechanisms of action, but functional mechanism of MASP-1 on LPS-AP link not fully elucidated","pmids":["29475986"],"is_preprint":false},{"year":2010,"finding":"CL-11 (collectin-11) copurifies with and interacts with MASP-1 and/or MASP-3 in plasma as demonstrated by ELISA. CL-11 forms the fifth lectin pathway initiation complex with MASP-1, MASP-2, MASP-3, and MAP-1; complex formation between recombinant CL-11 and MASP-2 on Candida albicans leads to C4b deposition.","method":"Copurification, ELISA, complement deposition assays on C. albicans","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — protein interaction confirmed by copurification and ELISA; functional complement activation shown","pmids":["20956340","23220946"],"is_preprint":false},{"year":2006,"finding":"MASP-1 cooperates with MASP-2 in generating C3 convertase through the MBL pathway. In MASP-1/2/3-depleted serum, reconstitution with both MASP-1 and MASP-2 has a synergistic effect on C3b deposition on mannan; MASP-3 inhibits this activity. No C3b deposition occurs with C2- or C4-depleted serum; factor B depletion has no effect.","method":"Depletion and reconstitution experiments with complement-depleted human serum, C3b deposition assay","journal":"International immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reconstitution in depleted serum with multiple depletion controls, single lab","pmids":["17182967"],"is_preprint":false},{"year":2010,"finding":"Phage display-evolved peptide SFMI-1 inhibits MASP-1 (KI 65 nM) and MASP-2 (KI 1030 nM); SFMI-2 inhibits only MASP-2 (KI 180 nM). SFMI-1 is more effective than SFMI-2 at preventing C3 and C4 deposition when zymogen MASPs are present, confirming MASP-1's crucial role in initiation by activating MASP-2.","method":"Phage display peptide selection, kinetic inhibition measurements, C3/C4 deposition assays with zymogen MASPs","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — quantitative inhibitor characterization with functional assays; single lab but internally consistent","pmids":["20817870"],"is_preprint":false},{"year":2015,"finding":"MASP-1/C1-INH complexes circulate in normal human blood. MASP-1 levels and MASP-1/C1-INH complex levels are significantly reduced in hereditary angioedema (HAE) patients (p<0.0001), correlating with C4 consumption and attack frequency, indicating MASP-1 is physiologically inhibited by C1-inhibitor and may contribute to HAE pathophysiology.","method":"ELISA for MASP-1 and MASP-1/C1-INH complexes in 128 HAE patients and 100 controls; correlation analysis","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — complex formation demonstrated by ELISA in human samples with clinical correlation; mechanistic implication supported by in vitro data from other studies","pmids":["26371246"],"is_preprint":false},{"year":2018,"finding":"MASP-1 enhances fibrin clot formation in a microvascular whole blood flow model. Addition of recombinant active MASP-1 accelerates fibrin clot formation; MASP-1-specific inhibitor SGMI-1 delays clot formation. Complement activation by zymosan increases clot formation, partially reversed by classical pathway inhibitor and almost abolished by SGMI-1 combined with it.","method":"Microfluidic endothelialized microchannel clot formation assay with real-time confocal microscopy, pathway-specific inhibitors","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — physiological flow model with specific inhibitors; single lab","pmids":["29324883"],"is_preprint":false},{"year":2022,"finding":"ARRB1 upregulates MASP1 expression in hepatocytes and promotes release of MASP1-enriched small extracellular vesicles via regulation of the autophagic-lysosomal/multivesicular body pathway and Rab27A activation. Hepatocyte-derived MASP1 activates hepatic stellate cells (HSCs) through p38 MAPK/ATF2 signaling to promote liver fibrogenesis.","method":"CCl4/NASH mouse models, primary cell isolation, small EV purification, proteomics, siRNA knockdown, p38 MAPK signaling assays, in vivo MASP1 overexpression","journal":"Hepatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple in vitro and in vivo methods; mechanistic pathway (p38/ATF2) identified but single lab","pmids":["35849032"],"is_preprint":false},{"year":2020,"finding":"C-reactive protein (CRP) binds monosodium urate crystals and recruits complement proteases C1 (C1q, C1r, C1s) and MASP-1, providing a pattern recognition mechanism linking MSU crystal recognition to complement activation.","method":"MSU crystal pulldown/purification from human body fluids, mass spectrometry identification, depletion of CRP from serum","journal":"Scientific reports","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single pulldown/mass spectrometry identification without mechanistic follow-up for MASP-1 specifically","pmids":["32286427"],"is_preprint":false},{"year":1995,"finding":"The human CRARF gene (encoding P100, later identified as MASP-1) was mapped by FISH to chromosome 3q27-q28, and the mouse homolog (Crarf) to chromosome 16B2-B3.","method":"Fluorescence in situ hybridization (FISH) on R-banded metaphase chromosomes","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct cytogenetic localization; foundational genomic placement","pmids":["7759119"],"is_preprint":false}],"current_model":"MASP-1 is the initiating serine protease of the lectin complement pathway: upon MBL/ficolin binding to pathogens, MASP-1 (which has an unusually high zymogen autoactivation rate) rapidly self-activates and then trans-activates MASP-2 (the exclusive route for MASP-2 activation in normal serum), cleaves C2 (~60% of C2a generation), and cleaves MASP-3; additionally, MASP-3 (sharing a gene with MASP-1 via alternative splicing) is the exclusive activator of pro-factor D in resting blood, linking the lectin and alternative pathways; beyond complement, MASP-1 is a promiscuous serine protease (wide substrate groove revealed by crystal structure) that cleaves coagulation factors (fibrinogen, factor XIII, prothrombin, TAFI), releases bradykinin from kininogen, activates endothelial cells through PAR4 and PAR1 cleavage to trigger NF-κB/p38 MAPK signaling, IL-6/IL-8 production, E-selectin upregulation, and increased vascular permeability, and can activate hepatic stellate cells via p38 MAPK/ATF2 to promote liver fibrosis; MAp44, a fourth splice product of the MASP1 gene, competes with MASP-2 for MBL/ficolin binding and inhibits the lectin pathway."},"narrative":{"mechanistic_narrative":"The MASP1 gene encodes multiple products through alternative splicing and is the keystone initiator of the lectin complement pathway, generating MASP-1, MASP-3, and the non-catalytic regulator MAp44 [PMID:11485744, PMID:19917686]. Upon assembly with the pattern-recognition collectins/ficolins—including MBL, ficolins, and CL-11—via Ca2+-dependent CUB1-EGF-CUB2 binding sites [PMID:18596036, PMID:20956340, PMID:23220946], MASP-1 self-activates with an autoactivation rate ~3000-fold higher than MASP-2 because its zymogen fluctuates into active-like conformations [PMID:23386610]. Activated MASP-1 is the exclusive activator of MASP-2 in normal serum, transactivating it within MBL/ficolin co-complexes, and contributes ~60% of C2a generation for C3 convertase assembly [PMID:22691502, PMID:22966085, PMID:23785123]; loss of MASP-1 abolishes lectin pathway activity in deficient mouse serum and human patients, rescued by reconstitution [PMID:18424734, PMID:22966085]. The alternatively spliced MASP-3 product is the physiological maturase of pro-factor D in resting blood, thereby coupling the lectin and alternative pathways [PMID:27535802, PMID:31399515, PMID:28794230]. A crystal structure of the MASP-1 catalytic region reveals a wide, trypsin-like substrate groove that explains its relaxed specificity [PMID:19564340], underlying a promiscuous protease role beyond complement: MASP-1 cleaves fibrinogen, factor XIII, prothrombin (at R271/R393) and TAFI to drive clot formation [PMID:18456010, PMID:22536427, PMID:26645987], releases bradykinin from high-molecular-weight kininogen [PMID:21625439], and activates endothelial cells through cleavage of PAR4 and PAR1 to trigger Ca2+/NF-κB/p38 MAPK signaling, IL-6/IL-8 production, E-selectin upregulation, and increased vascular permeability [PMID:19667088, PMID:24489848, PMID:31130964]. MASP-1 is physiologically restrained by C1-inhibitor, and reduced MASP-1/C1-INH complexes track with hereditary angioedema [PMID:26371246]. Loss-of-function mutations in the shared MASP1 exons cause 3MC syndrome, a neural crest–dependent developmental disorder [PMID:21035106, PMID:21258343].","teleology":[{"year":2001,"claim":"Established that the MASP1/3 locus produces more than one protein, revealing MASP-3 as an alternatively spliced product with regulatory rather than purely activating function.","evidence":"Molecular cloning, MBL complex fractionation, and functional complement assays","pmids":["11485744"],"confidence":"High","gaps":["Did not resolve the catalytic targets of MASP-3 itself","Stoichiometry of MASP-3 within native MBL oligomers not fully defined"]},{"year":2006,"claim":"Demonstrated cooperative roles of MASP-1 and MASP-2 in convertase assembly, addressing whether MASP-1 was functionally redundant.","evidence":"Depletion/reconstitution of complement-depleted human serum with C3b deposition readout","pmids":["17182967"],"confidence":"Medium","gaps":["Did not establish whether MASP-1 acts upstream of MASP-2 or in parallel","Mechanism of MASP-3 inhibition unresolved"]},{"year":2008,"claim":"Defined the structural basis of collectin/ficolin recognition and confirmed in vivo that MASP-1 promotes MASP-2 activation, resolving how the initiation complex assembles and functions.","evidence":"CUB1-EGF-CUB2 crystal structure with mutagenesis/SPR, plus MASP1/3−/− mouse with recombinant reconstitution","pmids":["18596036","18424734"],"confidence":"High","gaps":["Did not directly visualize a MASP-1/MASP-2 transactivation complex","Relative contribution of MASP-1 vs MASP-2 binding sites in mixed complexes unclear"]},{"year":2009,"claim":"Explained MASP-1's broad substrate specificity and confirmed PAR-mediated endothelial signaling, distinguishing it mechanistically from the narrow-specificity complement proteases.","evidence":"Catalytic-region crystal structure at 2.55 Å and PAR4 cleavage/Ca2+/NF-κB/p38 signaling assays in HUVECs","pmids":["19564340","19667088"],"confidence":"High","gaps":["Did not identify the full physiological substrate repertoire","In vivo relevance of endothelial PAR4 signaling not tested"]},{"year":2009,"claim":"Identified MAp44 as a fourth MASP1/3 splice product acting as a competitive inhibitor of the lectin pathway, establishing intragenic regulatory control.","evidence":"SPR binding kinetics, ELISA, and complement inhibition assays","pmids":["19917686"],"confidence":"High","gaps":["In vivo concentration-dependent regulation not quantified","Tissue-specific splice product ratios unaddressed"]},{"year":2012,"claim":"Proved MASP-1 is the exclusive activator of MASP-2 in normal serum and an essential initiator, settling the hierarchy of lectin pathway protease activation.","evidence":"Monospecific MASP-1/MASP-2 inhibitor proteins and patient serum reconstitution with co-complex ELISA, supported by Michaelis-complex crystal structures","pmids":["22691502","22966085","22511776"],"confidence":"High","gaps":["Quantitative kinetics of transactivation within native complexes not fully defined","Whether all MBL/ficolin complexes carry both proteases unresolved"]},{"year":2013,"claim":"Quantified MASP-1's exceptionally high zymogen autoactivation and showed it cleaves both MASP-2 and MASP-3 proenzymes, explaining how the pathway is triggered without an upstream activator.","evidence":"Rate-constant measurements with zymogen/active-site mutants and proenzyme MASP-1 crystal structure at 2.5 Å","pmids":["23386610"],"confidence":"High","gaps":["Trigger that converts surface binding into autoactivation in vivo not defined","Conformational dynamics modeled crystallographically rather than in solution"]},{"year":2013,"claim":"Clarified the architecture of transactivation by showing MASP-1/MASP-2 co-complexes form only via MBL/ficolin scaffolds and that MAp44 disrupts these complexes.","evidence":"Gel filtration, ELISA co-complex detection, and complement activation assays","pmids":["23785123"],"confidence":"Medium","gaps":["Single-lab biochemical detection without structural confirmation","Direct vs scaffold-mediated heterodimer contributions partly resolved only by later fragment studies"]},{"year":2014,"claim":"Mapped MASP-1/MASP-2 and MASP-1/MASP-3 dimerization behavior through CUB1-EGF-CUB2 fragments, defining how subunit pairing is governed by Ca2+.","evidence":"Size-exclusion chromatography, native PAGE, and EDTA dissociation/re-association with recombinant fragments","pmids":["24424083"],"confidence":"Medium","gaps":["Used isolated fragments rather than full-length proteins","Physiological relevance of heterodimers vs homodimers in serum not established"]},{"year":2014,"claim":"Showed native serum MBL-MASP complexes activate endothelium and that this requires MASP-1 catalytic activity, anchoring the signaling role to physiological complexes.","evidence":"Ca2+ signaling assays in HUVECs comparing native complexes, recombinant fragments, and zymogen mutant; plus cytokine/chemotaxis assays","pmids":["24472859","24489848"],"confidence":"High","gaps":["In vivo endothelial activation by MASP-1 not demonstrated","Receptor(s) mediating cytokine induction not fully resolved in these studies"]},{"year":2008,"claim":"Demonstrated MASP-1 cross-talk with coagulation by cleaving fibrinogen and factor XIII at thrombin-like sites, opening the link between complement and hemostasis.","evidence":"In vitro cleavage assays, SDS-PAGE, N-terminal sequencing with thrombin comparison","pmids":["18456010"],"confidence":"High","gaps":["Slow turnover (~650-fold lower than thrombin) leaves physiological significance to be weighted","In vivo contribution to clotting not addressed here"]},{"year":2011,"claim":"Established MASP-1 as a bradykinin-generating protease via kininogen cleavage, connecting it to vascular permeability and inflammation.","evidence":"Proteomics, SDS-PAGE, HPLC bradykinin detection, and kinetics with C1-inhibitor control","pmids":["21625439"],"confidence":"High","gaps":["In vivo bradykinin release by MASP-1 not demonstrated","Relative contribution versus kallikrein not quantified"]},{"year":2015,"claim":"Defined the prothrombin cleavage mechanism, showing MASP-1 activates prothrombin via two parallel cleavage routes generating alternative thrombin species.","evidence":"Arginine-to-glutamine prothrombin mutants, N-terminal sequencing, and thrombelastography (also 2012/2014 plasma and purified-system clot assays)","pmids":["25745807","26645987","22536427"],"confidence":"High","gaps":["Physiological flux through MASP-1-driven prothrombin activation in vivo not quantified","Interplay with TAFI/clot-lysis effects not fully integrated"]},{"year":2016,"claim":"Identified MASP-3 as the exclusive activator of pro-factor D in resting blood, establishing a direct molecular bridge between the lectin and alternative complement pathways.","evidence":"Evolved monospecific MASP inhibitors in resting blood with pro-FD activation assays and kinetics (with companion 2015 plasma assays)","pmids":["27535802","26673137"],"confidence":"High","gaps":["Whether residual MASP-3-independent FD maturation contributes was clarified only later","Spatial site of pro-FD activation in vivo unknown"]},{"year":2017,"claim":"Linked 3MC-associated MASP-3 mutations to loss of factor D maturase activity, explaining the alternative-pathway defect while revealing MASP-3-independent maturation also exists.","evidence":"Isoelectric focusing of FD variants, mutant enzyme characterization, MASP-3-depleted serum, patient sera, and KO mice","pmids":["28794230"],"confidence":"High","gaps":["Identity of the MASP-3-independent FD maturase not determined","How 3MC craniofacial phenotype relates to FD maturation defect unclear"]},{"year":2018,"claim":"Showed MASP-1 contributes to surface-specific alternative pathway activation (LPS but not zymosan) and to clot formation under flow, extending its role into pathogen-context and physiological hemostasis.","evidence":"Specific MASP-1 inhibitors (SGMI-1 and others) in AP assays and a microvascular endothelialized whole-blood clot model","pmids":["29475986","29324883"],"confidence":"Medium","gaps":["Molecular basis of the LPS-specific MASP-1 requirement not elucidated","Single-lab flow models await independent replication"]},{"year":2019,"claim":"Defined PAR1-dependent endothelial permeability signaling and confirmed in monospecific KO mice that MASP-1 (not MASP-3) drives lectin pathway activation while MASP-3 drives FD maturation, cleanly separating the two splice products' physiological roles.","evidence":"Impedance/permeability/Ca2+/Rho-kinase assays in HUVECs and monospecific MASP-1-KO and MASP-3-KO mice with pathway activity readouts","pmids":["31130964","31399515"],"confidence":"High","gaps":["In vivo permeability consequences of MASP-1 PAR1 signaling not tested in the KO mice","Crosstalk between bradykinin-receptor upregulation and PAR signaling unresolved"]},{"year":2022,"claim":"Extended MASP-1 biology to organ fibrosis, showing hepatocyte-derived MASP1 in extracellular vesicles activates hepatic stellate cells via p38 MAPK/ATF2 to promote liver fibrogenesis.","evidence":"CCl4/NASH mouse models, EV proteomics, siRNA knockdown, and p38 MAPK signaling assays","pmids":["35849032"],"confidence":"Medium","gaps":["Whether catalytic activity of MASP1 is required for HSC activation not fully isolated","Single-lab study awaiting independent confirmation"]},{"year":null,"claim":"How the diverse non-complement substrates (coagulation factors, kininogen, PAR receptors) are integrated in vivo, and the identity of the MASP-3-independent factor D maturase, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No in vivo quantification of MASP-1's relative contribution to coagulation versus dedicated coagulation proteases","Identity of MASP-3-independent FD maturase unknown","Mechanism coupling MASP-1 endothelial signaling to systemic vascular phenotypes undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[2,7,9,12,13,14,16,27]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[5,11,12,13,14]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,23]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[7,19]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[1,2,4,29,32]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[34]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,2,3,4,6,26]},{"term_id":"R-HSA-109582","term_label":"Hemostasis","supporting_discovery_ids":[12,14,16,33]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[7,17,19,34]}],"complexes":["MBL-MASP lectin pathway initiation complex","ficolin-MASP complex","CL-11 (collectin-11) initiation complex","MASP-1/C1-inhibitor complex"],"partners":["MASP2","MBL2","FCN1","COLEC11","SERPING1","C2","CFD","F2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P48740","full_name":"Mannan-binding lectin serine protease 1","aliases":["Complement-activating component of Ra-reactive factor","Mannose-binding lectin-associated serine protease 1","MASP-1","Mannose-binding protein-associated serine protease","Ra-reactive factor serine protease p100","RaRF","Serine protease 5"],"length_aa":699,"mass_kda":79.2,"function":"Precursor of a serum protease that activates the complement pathway of the complement system, a cascade of proteins that leads to phagocytosis and breakdown of pathogens and signaling that strengthens the adaptive immune system Serine protease that activates the lectin pathway of the complement system, a cascade of proteins that leads to phagocytosis and breakdown of pathogens and signaling that strengthens the adaptive immune system (PubMed:10946292, PubMed:11527969, PubMed:12538697, PubMed:22691502, PubMed:22966085, PubMed:9087411). The lectin complement system is activated following association of lectins, such as MBL2, FCN1, FCN2 or FCN3, to carbohydrates on the pathogen surface (PubMed:22854970, PubMed:22966085, PubMed:23386610, PubMed:9087411). Following autoproteolytic processing in response to lectin-binding to pathogen carbohydrates, catalyzes cleavage and activation of MASP2, the next component of the lectin complement pathway (PubMed:22691502, PubMed:22966085, PubMed:23386610) Serine protease that activates the alternative pathway of the complement system, a cascade of proteins that leads to phagocytosis and breakdown of pathogens and signaling that strengthens the adaptive immune system (PubMed:20038603, PubMed:23792966, PubMed:27535802). The alternative complement pathway acts as an amplification loop that enhances other complement pathways (PubMed:27535802). Isoform MASP-3 specifically catalyzes cleavage and activation of factor D (CFD), the protease that initiates the alternative complement pathway (PubMed:20038603, PubMed:27535802)","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/P48740/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MASP1","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/MASP1","total_profiled":1310},"omim":[{"mim_id":"613791","title":"MASP2 DEFICIENCY","url":"https://www.omim.org/entry/613791"},{"mim_id":"612502","title":"COLLECTIN 11; COLEC11","url":"https://www.omim.org/entry/612502"},{"mim_id":"606860","title":"COMPLEMENT COMPONENT 1 INHIBITOR; C1NH","url":"https://www.omim.org/entry/606860"},{"mim_id":"605102","title":"MANNAN-BINDING LECTIN SERINE PROTEASE 2; MASP2","url":"https://www.omim.org/entry/605102"},{"mim_id":"602228","title":"TRANSCRIPTION FACTOR 7-LIKE 2; TCF7L2","url":"https://www.omim.org/entry/602228"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Nucleoplasm","reliability":"Enhanced"},{"location":"Cytosol","reliability":"Enhanced"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"cervix","ntpm":100.9},{"tissue":"heart muscle","ntpm":108.6},{"tissue":"liver","ntpm":171.6}],"url":"https://www.proteinatlas.org/search/MASP1"},"hgnc":{"alias_symbol":["MASP","Map44","MASP-3","MAP-1"],"prev_symbol":["CRARF","PRSS5"]},"alphafold":{"accession":"P48740","domains":[{"cath_id":"2.60.120.290","chopping":"21-140","consensus_level":"high","plddt":92.4643,"start":21,"end":140},{"cath_id":"2.60.120.290","chopping":"184-298","consensus_level":"medium","plddt":95.8408,"start":184,"end":298},{"cath_id":"2.10.70.10","chopping":"301-365","consensus_level":"medium","plddt":95.5078,"start":301,"end":365},{"cath_id":"2.10.70.10","chopping":"377-435","consensus_level":"medium","plddt":94.5271,"start":377,"end":435},{"cath_id":"2.40.10.10","chopping":"454-496_506-696","consensus_level":"medium","plddt":91.2106,"start":454,"end":696}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P48740","model_url":"https://alphafold.ebi.ac.uk/files/AF-P48740-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P48740-F1-predicted_aligned_error_v6.png","plddt_mean":90.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MASP1","jax_strain_url":"https://www.jax.org/strain/search?query=MASP1"},"sequence":{"accession":"P48740","fasta_url":"https://rest.uniprot.org/uniprotkb/P48740.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P48740/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P48740"}},"corpus_meta":[{"pmid":"11485744","id":"PMC_11485744","title":"MASP-3 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through alternative splicing of the MASP-1/3 gene and associates with larger MBL oligomers together with MASP-2, while MASP-1 associates with smaller oligomers. MASP-3 downregulates the C4 and C2 cleaving activity of MASP-2.\",\n      \"method\": \"Molecular cloning, MBL complex fractionation, functional complement assays\",\n      \"journal\": \"Immunity\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — identification of novel splice product with biochemical characterization of complex composition and functional inhibition assay; widely replicated\",\n      \"pmids\": [\"11485744\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"MAp44, a fourth product of the MASP1/3 gene (sharing CUB1-EGF-CUB2-CCP1 domains with MASP-1 and MASP-3 but with a unique 17 aa C-terminus), circulates in Ca2+-dependent complexes with MBL and ficolins (KD ~0.6 nM for MBL) and competes with MASP-2 for binding to MBL and ficolins, thereby inhibiting complement activation.\",\n      \"method\": \"Surface plasmon resonance, ELISA, complement activation inhibition assays\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — SPR binding kinetics, competition assay, and functional complement inhibition; replicated by multiple labs\",\n      \"pmids\": [\"19917686\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"In normal human serum, MASP-1 is the exclusive activator of MASP-2; MASP-2 autoactivation is strictly dependent on prior activation by MASP-1, and MASP-1 inhibition prevents MASP-2 autoactivation. Additionally, MASP-1 contributes ~60% of C2a formation responsible for C3 convertase assembly.\",\n      \"method\": \"Monospecific inhibitor proteins against MASP-1 and MASP-2 used in functional lectin pathway assays with normal human serum\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — unique monospecific inhibitors with orthogonal biochemical assays; widely replicated by independent groups\",\n      \"pmids\": [\"22691502\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"MASP-1 contributes to lectin pathway activation, primarily by promoting MASP-2 activation. MASP-1/3-deficient mouse serum shows significantly reduced C4 and C3 deposition on mannan, which is restored by reconstitution with recombinant MASP-1. MASP-1 promotes MASP-2 activation in deficient serum.\",\n      \"method\": \"Gene-targeted MASP1/3−/− mouse model, serum complement activity assays, reconstitution with recombinant MASP-1\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO mouse with reconstitution experiment; replicated across labs\",\n      \"pmids\": [\"18424734\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"In a MASP-1/MASP-3-deficient human patient (nonsense mutation in common MASP1 exon), the lectin pathway is nonfunctional but the alternative pathway functions normally. Reconstitution with MASP-1 restores lectin pathway activity through direct activation of MASP-2. MASP-1 and MASP-2 can co-associate in the same MBL complex (co-complexes found in serum), enabling transactivation.\",\n      \"method\": \"Patient serum studies, complement pathway activity assays, reconstitution, ELISA co-complex detection\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — human genetic deficiency with reconstitution and mechanistic follow-up; complements mouse KO data\",\n      \"pmids\": [\"22966085\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Crystal structure of active MASP-1 catalytic region resolved at 2.55 Å reveals a wide substrate-binding groove resembling trypsin rather than early complement proteases, an unusual internal salt bridge between S1 Asp189 and Arg224, and a very long 60-loop, explaining MASP-1's broad/relaxed substrate specificity.\",\n      \"method\": \"X-ray crystallography (2.55 Å resolution)\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional interpretation; foundational structural paper\",\n      \"pmids\": [\"19564340\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"MASP-3 is the exclusive activator of pro-factor D in resting blood. Using evolved monospecific MASP-1 and MASP-3 inhibitors, neither MASP-1 nor MASP-2 activates pro-FD in resting blood, but MASP-3 inhibition abolishes pro-FD maturation, demonstrating a fundamental link between the lectin and alternative complement pathways.\",\n      \"method\": \"Evolved monospecific MASP inhibitors applied to resting blood; pro-FD activation assays; in vitro kinetics\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — specific inhibitors with multiple orthogonal assays; confirmed by independent groups using MASP-3 KO mice\",\n      \"pmids\": [\"27535802\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"MASP-1 activates Ca2+ signaling, NF-κB, and p38 MAPK pathways in human endothelial cells (HUVECs) through cleavage of PAR4 (protease-activated receptor 4). Activation requires proteolytic activity of MASP-1; MASP-2 has no such effect. Membrane-bound intact PAR4 decreases after MASP-1 treatment.\",\n      \"method\": \"Cell signaling assays (Ca2+ imaging, western blot for NF-κB/p38 MAPK), synthetic PAR peptide substrate cleavage assays, mRNA quantification, flow cytometry\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (Ca2+ signaling, NF-κB, p38, PAR4 cleavage assay, receptor downregulation); replicated in subsequent studies\",\n      \"pmids\": [\"19667088\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Crystal structure of the CUB1-EGF-CUB2 domain of human MASP-1/3 resolved at 2.3 Å. The structure shows a head-to-tail homodimer stabilized by hydrophobic interactions and Ca2+ ions. Point mutagenesis of 27 residues in MASP-3 identified two homologous binding sites (on CUB1 and CUB2) for MBL and ficolins, located near Ca2+-binding sites, involving a major electrostatic interaction between acidic Ca2+ ligands of MASP-1/3 and a conserved lysine of MBL.\",\n      \"method\": \"X-ray crystallography (2.3 Å), site-directed mutagenesis, surface plasmon resonance\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure combined with mutagenesis and binding kinetics\",\n      \"pmids\": [\"18596036\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"MASP-1 autoactivation rate is ~3000-fold higher than MASP-2 autoactivation; both activated and zymogen MASP-1 cleave proenzyme MASP-2 efficiently; MASP-1 also cleaves MASP-3 proenzyme. Crystal structure of proenzyme MASP-1 R448Q at 2.5 Å shows zymogen MASP-1 fluctuates between inactive and active-like conformations, explaining its unusually high zymogen activity.\",\n      \"method\": \"Rate constant measurements with zymogen and active-site mutant recombinant proteins, X-ray crystallography (2.5 Å), kinetic modeling\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — quantitative kinetics with mutagenesis and crystal structure in single study\",\n      \"pmids\": [\"23386610\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"MASP-1 and MASP-2 are both essential for lectin pathway activation. A monospecific MASP-1 inhibitor completely blocks lectin pathway activation. Crystal structures of Michaelis-like complexes of MASP-1 and MASP-2 with substrate-like inhibitors resolved at 1.28 Å (MASP-2) reveal significant plasticity of MASP-2.\",\n      \"method\": \"Evolved monospecific inhibitors, complement activation assays, X-ray crystallography\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — monospecific inhibitors with crystal structures; orthogonal validation of MASP-1 essentiality\",\n      \"pmids\": [\"22511776\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"MASP-1 cleaves fluorescent amide substrates with preference for Phe-Gly-Arg-AMC (rate 16.8 nmol/min/µg). C1 inhibitor inhibits both MASP-1 and MASP-2 (though complexes are unstable at alkaline pH). The thrombin inhibitor boroMpg inhibits MASP-1 but not MASP-2, and antithrombin III with heparin inhibits both MASPs.\",\n      \"method\": \"In vitro enzyme assays with fluorescent amide substrates, inhibitor profiling\",\n      \"journal\": \"Molecular immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — rigorous in vitro enzymatic characterization with multiple substrates and inhibitors\",\n      \"pmids\": [\"14725788\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"MASP-1 cleaves factor XIII A-chain and fibrinogen beta-chain at identical sites to thrombin, but with ~650-fold lower turnover rate. MASP-1 cleavage of fibrinogen releases proinflammatory fibrinopeptide B (not fibrinopeptide A as thrombin does for the alpha-chain). MASP-1 can drive formation of cross-linked fibrinogen.\",\n      \"method\": \"In vitro cleavage assays, SDS-PAGE, N-terminal sequencing, comparison with thrombin\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with site identification and quantitative comparison; replicated in subsequent studies\",\n      \"pmids\": [\"18456010\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MASP-1 cleaves high-molecular-weight kininogen (HK) to release bradykinin (BK). MASP-2 also cleaves HK but cannot release BK. Catalytic efficiency of HK cleavage by recombinant MASP-1 is ~4.0×10² M⁻¹s⁻¹. C1-inhibitor prevents HK cleavage by MASP-1.\",\n      \"method\": \"Differential gel electrophoresis proteomics, SDS-PAGE, HPLC for BK detection, kinetic measurements\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with multiple orthogonal detection methods and kinetics quantified\",\n      \"pmids\": [\"21625439\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"MASP-1 activates factor XIII, prothrombin (generating F1+2 fragments), fibrinogen (generating fibrinopeptide A via thrombin), and TAFI in citrated plasma and purified systems. MASP-1 induces clot formation and affects fibrin clot structure in NCP; it prolongs clot lysis. MASP-1-induced fibrin formation is thrombin-dependent but MASP-1 directly activates prothrombin.\",\n      \"method\": \"FXIII incorporation assay, specific cleavage product assays, turbidimetric clot assay, scanning electron microscopy\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple in vitro assays with purified and plasma-based systems; replicated by same group and others\",\n      \"pmids\": [\"22536427\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"MASP-1 cleaves prothrombin at three sites (R155, R271, R393) identified by N-terminal sequencing, promotes clot formation in whole blood and platelet-poor plasma (measured by thrombelastography), and shortens clotting time. MASP-1-induced clotting requires prothrombin in a purified system.\",\n      \"method\": \"SDS-PAGE, N-terminal sequencing, thrombelastography, purified system reconstitution\",\n      \"journal\": \"Molecular immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with site identification; extends prior coagulation findings\",\n      \"pmids\": [\"25745807\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"MASP-1 activates prothrombin via two simultaneous pathways (cleaving R271 or R393 first), generating active alternative thrombin species. Both R393 and R320 are required for prothrombin activation by MASP-1; R155 is not an important cleavage site.\",\n      \"method\": \"Arginine-to-glutamine prothrombin mutants, SDS-PAGE, N-terminal sequencing, thrombelastography\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis of prothrombin with in vitro reconstitution and functional clotting assay\",\n      \"pmids\": [\"26645987\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"MASP-1 induces IL-6 and IL-8 (but not IL-1α, IL-1ra, TNFα, MCP-1) production in HUVECs through the p38-MAPK pathway, and the conditioned medium triggers neutrophil chemotaxis.\",\n      \"method\": \"Cytokine ELISA, p38-MAPK pathway inhibition, neutrophil chemotaxis assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal assays (cytokine measurement, pathway inhibition, functional chemotaxis), single lab\",\n      \"pmids\": [\"24489848\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"MASP-1 activates endothelial cells to up-regulate E-selectin expression and decrease ICAM-2, resulting in increased adhesion between endothelial cells and neutrophil granulocytes. ICAM-1, VCAM-1, and P-selectin remain unchanged.\",\n      \"method\": \"Flow cytometry for adhesion molecules on HUVECs, adhesion assay with differentiated PLB-985 cells\",\n      \"journal\": \"Molecular immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — single lab, clean functional assay but single-method per endpoint\",\n      \"pmids\": [\"27219453\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"MASP-1 increases endothelial paracellular permeability through PAR1-mediated intracellular Ca2+ mobilization, Rho-kinase activation, myosin light chain phosphorylation, cytoskeletal actin rearrangement, and disruption of interendothelial junctions. MASP-1 also up-regulates bradykinin B2 receptor expression in HUVECs.\",\n      \"method\": \"Real-time electric impedance sensing, XperT permeability assay, Ca2+ imaging, Rho-kinase inhibition, whole-transcriptome microarray\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (impedance, permeability, Ca2+, kinase, transcriptome) in single study\",\n      \"pmids\": [\"31130964\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Serum MASP-1 in complex with MBL (native lectin pathway complexes) activates endothelial cells (Ca2+ signaling). Among MBL-associated components, only MASP-1 triggers this response; MASP-2, MASP-3, non-enzymatic domains of MASP-1/MASP-2, and zymogen MASP-1 mutant are all ineffective, indicating proteolytic activity of MASP-1 is required.\",\n      \"method\": \"Ca2+ signaling assay in HUVECs with native serum MBL-MASP complexes and recombinant fragments/mutants\",\n      \"journal\": \"Molecular immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic comparison of native and recombinant components with enzymatic activity requirement demonstrated\",\n      \"pmids\": [\"24472859\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MASP-1 mutations in the MASP1 gene (shared exons encoding both MASP-1 and MASP-3, or isoforms affecting only MASP-3) cause 3MC syndrome (Carnevale, Malpuech, Michels, Mingarelli). A missense mutation p.G687R and a nonsense mutation p.W290X both cosegregate with the syndrome phenotype in consanguineous families.\",\n      \"method\": \"Exome sequencing, Sanger sequencing, homozygosity mapping, cosegregation analysis\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic linkage with cosegregation; no in vitro functional reconstitution in this paper\",\n      \"pmids\": [\"21035106\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"COLEC11 and MASP1 mutations cause 3MC syndrome. CL-K1 (encoded by COLEC11) serves as a guidance cue for neural crest cell migration; zebrafish morphants for either gene develop pigmentary defects and severe craniofacial abnormalities, demonstrating a role for lectin complement pathway factors in neural crest-dependent developmental processes.\",\n      \"method\": \"Human genetics (mutation identification), zebrafish morpholino knockdown, craniofacial phenotype analysis, neural crest cell migration assay\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — zebrafish loss-of-function with specific developmental phenotype; mechanistic link for MASP1 in development is indirect (via CL-K1)\",\n      \"pmids\": [\"21258343\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"MASP-1 and MASP-2 do not directly form heterodimers, but addition of MBL or ficolins enables formation of MASP-1/MASP-2 co-complexes in serum. These co-complexes have a functional role in activating complement; MAp44 inhibits complement not only by displacing MASP-2 from MBL/ficolins but by disrupting MASP-1/MASP-2 co-complexes and impairing transactivation.\",\n      \"method\": \"Gel filtration, ELISA co-complex detection in serum, functional complement activation assays with defined MBL/ficolin complexes\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical co-complex detection with functional validation, single lab\",\n      \"pmids\": [\"23785123\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"MASP-1 and MASP-2 can form heterodimers via their CUB1-EGF-CUB2 regions after Ca2+-mediated dissociation and re-association. Heterodimer formation between MASP-1 and MASP-3 subunits occurs even in the presence of Ca2+. Both MASP-1 and MASP-2 form tight Ca2+-dependent homodimers.\",\n      \"method\": \"Size exclusion chromatography, native PAGE, EDTA dissociation/re-association kinetics with recombinant CUB1-EGF-CUB2 fragments\",\n      \"journal\": \"Molecular immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical characterization with defined recombinant fragments, single lab\",\n      \"pmids\": [\"24424083\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"MASP-1 and MASP-2 do not activate pro-factor D in resting human plasma/serum. MASP-3 is the most likely physiological activator of pro-FD; selective MASP-1 and MASP-2 inhibitors do not reduce pro-FD activation, whereas a high concentration MASP-2 inhibitor (which also weakly inhibits MASP-3) slows activation, and added recombinant MASP-3 reduces pro-FD half-life.\",\n      \"method\": \"Fluorescently labeled pro-FD activation assay in serum/plasma, selective MASP inhibitors, kinetic measurements with purified enzymes\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — quantitative kinetics with specific inhibitors and novel pro-FD assay; consistent with companion study PMID 27535802\",\n      \"pmids\": [\"26673137\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"MASP-3, but not MASP-1, activates pro-factor D under physiological conditions in mice. Mice monospecifically deficient in MASP-1 lack lectin pathway activity but have normal alternative pathway with active FD, whereas MASP-3-deficient mice lack alternative pathway activity with zymogenic FD present. MASP-3 circulates predominantly as an active form.\",\n      \"method\": \"Monospecific MASP-1-KO and MASP-3-KO mouse generation, complement pathway activity assays, FD zymogen detection\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean monospecific KO mice with direct pathway activity measurement; confirmatory of in vitro inhibitor studies\",\n      \"pmids\": [\"31399515\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"3MC-associated MASP-3 mutations all yield enzymatically inactive MASP-3 protein. In MASP-3-depleted human serum, sera from 3MC patients, and Masp1/3−/− mice, lack of enzymatically active MASP-3 compromises pro-FD-to-FD conversion, confirming MASP-3 as an important maturase of factor D in the alternative pathway. 3MC patients contain predominantly pro-FD but also detectable mature FD, indicating MASP-3-independent maturation also occurs.\",\n      \"method\": \"Isoelectric focusing of endogenous FD variants, enzymatic characterization of mutant MASP-3 proteins, MASP-3-depleted human serum assays, patient sera, KO mice\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — human genetics, biochemical characterization of mutants, depleted serum, and KO mice as orthogonal approaches\",\n      \"pmids\": [\"28794230\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MASP-1 is essential for LPS-induced alternative pathway (AP) activation but has little effect on zymosan-induced AP activation. MASP-1 inhibition (by SGMI-1 and other inhibitors with different mechanisms) prevents AP activation on LPS surfaces and attenuates already-initiated AP activity.\",\n      \"method\": \"Specific MASP-1 inhibitors (SGMI-1 and others) in AP complement activation assays on LPS and zymosan surfaces\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — specific inhibitors with multiple mechanisms of action, but functional mechanism of MASP-1 on LPS-AP link not fully elucidated\",\n      \"pmids\": [\"29475986\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CL-11 (collectin-11) copurifies with and interacts with MASP-1 and/or MASP-3 in plasma as demonstrated by ELISA. CL-11 forms the fifth lectin pathway initiation complex with MASP-1, MASP-2, MASP-3, and MAP-1; complex formation between recombinant CL-11 and MASP-2 on Candida albicans leads to C4b deposition.\",\n      \"method\": \"Copurification, ELISA, complement deposition assays on C. albicans\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — protein interaction confirmed by copurification and ELISA; functional complement activation shown\",\n      \"pmids\": [\"20956340\", \"23220946\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"MASP-1 cooperates with MASP-2 in generating C3 convertase through the MBL pathway. In MASP-1/2/3-depleted serum, reconstitution with both MASP-1 and MASP-2 has a synergistic effect on C3b deposition on mannan; MASP-3 inhibits this activity. No C3b deposition occurs with C2- or C4-depleted serum; factor B depletion has no effect.\",\n      \"method\": \"Depletion and reconstitution experiments with complement-depleted human serum, C3b deposition assay\",\n      \"journal\": \"International immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reconstitution in depleted serum with multiple depletion controls, single lab\",\n      \"pmids\": [\"17182967\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Phage display-evolved peptide SFMI-1 inhibits MASP-1 (KI 65 nM) and MASP-2 (KI 1030 nM); SFMI-2 inhibits only MASP-2 (KI 180 nM). SFMI-1 is more effective than SFMI-2 at preventing C3 and C4 deposition when zymogen MASPs are present, confirming MASP-1's crucial role in initiation by activating MASP-2.\",\n      \"method\": \"Phage display peptide selection, kinetic inhibition measurements, C3/C4 deposition assays with zymogen MASPs\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — quantitative inhibitor characterization with functional assays; single lab but internally consistent\",\n      \"pmids\": [\"20817870\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"MASP-1/C1-INH complexes circulate in normal human blood. MASP-1 levels and MASP-1/C1-INH complex levels are significantly reduced in hereditary angioedema (HAE) patients (p<0.0001), correlating with C4 consumption and attack frequency, indicating MASP-1 is physiologically inhibited by C1-inhibitor and may contribute to HAE pathophysiology.\",\n      \"method\": \"ELISA for MASP-1 and MASP-1/C1-INH complexes in 128 HAE patients and 100 controls; correlation analysis\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — complex formation demonstrated by ELISA in human samples with clinical correlation; mechanistic implication supported by in vitro data from other studies\",\n      \"pmids\": [\"26371246\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MASP-1 enhances fibrin clot formation in a microvascular whole blood flow model. Addition of recombinant active MASP-1 accelerates fibrin clot formation; MASP-1-specific inhibitor SGMI-1 delays clot formation. Complement activation by zymosan increases clot formation, partially reversed by classical pathway inhibitor and almost abolished by SGMI-1 combined with it.\",\n      \"method\": \"Microfluidic endothelialized microchannel clot formation assay with real-time confocal microscopy, pathway-specific inhibitors\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — physiological flow model with specific inhibitors; single lab\",\n      \"pmids\": [\"29324883\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ARRB1 upregulates MASP1 expression in hepatocytes and promotes release of MASP1-enriched small extracellular vesicles via regulation of the autophagic-lysosomal/multivesicular body pathway and Rab27A activation. Hepatocyte-derived MASP1 activates hepatic stellate cells (HSCs) through p38 MAPK/ATF2 signaling to promote liver fibrogenesis.\",\n      \"method\": \"CCl4/NASH mouse models, primary cell isolation, small EV purification, proteomics, siRNA knockdown, p38 MAPK signaling assays, in vivo MASP1 overexpression\",\n      \"journal\": \"Hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple in vitro and in vivo methods; mechanistic pathway (p38/ATF2) identified but single lab\",\n      \"pmids\": [\"35849032\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"C-reactive protein (CRP) binds monosodium urate crystals and recruits complement proteases C1 (C1q, C1r, C1s) and MASP-1, providing a pattern recognition mechanism linking MSU crystal recognition to complement activation.\",\n      \"method\": \"MSU crystal pulldown/purification from human body fluids, mass spectrometry identification, depletion of CRP from serum\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single pulldown/mass spectrometry identification without mechanistic follow-up for MASP-1 specifically\",\n      \"pmids\": [\"32286427\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"The human CRARF gene (encoding P100, later identified as MASP-1) was mapped by FISH to chromosome 3q27-q28, and the mouse homolog (Crarf) to chromosome 16B2-B3.\",\n      \"method\": \"Fluorescence in situ hybridization (FISH) on R-banded metaphase chromosomes\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct cytogenetic localization; foundational genomic placement\",\n      \"pmids\": [\"7759119\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MASP-1 is the initiating serine protease of the lectin complement pathway: upon MBL/ficolin binding to pathogens, MASP-1 (which has an unusually high zymogen autoactivation rate) rapidly self-activates and then trans-activates MASP-2 (the exclusive route for MASP-2 activation in normal serum), cleaves C2 (~60% of C2a generation), and cleaves MASP-3; additionally, MASP-3 (sharing a gene with MASP-1 via alternative splicing) is the exclusive activator of pro-factor D in resting blood, linking the lectin and alternative pathways; beyond complement, MASP-1 is a promiscuous serine protease (wide substrate groove revealed by crystal structure) that cleaves coagulation factors (fibrinogen, factor XIII, prothrombin, TAFI), releases bradykinin from kininogen, activates endothelial cells through PAR4 and PAR1 cleavage to trigger NF-κB/p38 MAPK signaling, IL-6/IL-8 production, E-selectin upregulation, and increased vascular permeability, and can activate hepatic stellate cells via p38 MAPK/ATF2 to promote liver fibrosis; MAp44, a fourth splice product of the MASP1 gene, competes with MASP-2 for MBL/ficolin binding and inhibits the lectin pathway.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"The MASP1 gene encodes multiple products through alternative splicing and is the keystone initiator of the lectin complement pathway, generating MASP-1, MASP-3, and the non-catalytic regulator MAp44 [#0, #1]. Upon assembly with the pattern-recognition collectins/ficolins—including MBL, ficolins, and CL-11—via Ca2+-dependent CUB1-EGF-CUB2 binding sites [#8, #29], MASP-1 self-activates with an autoactivation rate ~3000-fold higher than MASP-2 because its zymogen fluctuates into active-like conformations [#9]. Activated MASP-1 is the exclusive activator of MASP-2 in normal serum, transactivating it within MBL/ficolin co-complexes, and contributes ~60% of C2a generation for C3 convertase assembly [#2, #4, #23]; loss of MASP-1 abolishes lectin pathway activity in deficient mouse serum and human patients, rescued by reconstitution [#3, #4]. The alternatively spliced MASP-3 product is the physiological maturase of pro-factor D in resting blood, thereby coupling the lectin and alternative pathways [#6, #26, #27]. A crystal structure of the MASP-1 catalytic region reveals a wide, trypsin-like substrate groove that explains its relaxed specificity [#5], underlying a promiscuous protease role beyond complement: MASP-1 cleaves fibrinogen, factor XIII, prothrombin (at R271/R393) and TAFI to drive clot formation [#12, #14, #16], releases bradykinin from high-molecular-weight kininogen [#13], and activates endothelial cells through cleavage of PAR4 and PAR1 to trigger Ca2+/NF-κB/p38 MAPK signaling, IL-6/IL-8 production, E-selectin upregulation, and increased vascular permeability [#7, #17, #19]. MASP-1 is physiologically restrained by C1-inhibitor, and reduced MASP-1/C1-INH complexes track with hereditary angioedema [#32]. Loss-of-function mutations in the shared MASP1 exons cause 3MC syndrome, a neural crest–dependent developmental disorder [#21, #22].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Established that the MASP1/3 locus produces more than one protein, revealing MASP-3 as an alternatively spliced product with regulatory rather than purely activating function.\",\n      \"evidence\": \"Molecular cloning, MBL complex fractionation, and functional complement assays\",\n      \"pmids\": [\"11485744\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve the catalytic targets of MASP-3 itself\", \"Stoichiometry of MASP-3 within native MBL oligomers not fully defined\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrated cooperative roles of MASP-1 and MASP-2 in convertase assembly, addressing whether MASP-1 was functionally redundant.\",\n      \"evidence\": \"Depletion/reconstitution of complement-depleted human serum with C3b deposition readout\",\n      \"pmids\": [\"17182967\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not establish whether MASP-1 acts upstream of MASP-2 or in parallel\", \"Mechanism of MASP-3 inhibition unresolved\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Defined the structural basis of collectin/ficolin recognition and confirmed in vivo that MASP-1 promotes MASP-2 activation, resolving how the initiation complex assembles and functions.\",\n      \"evidence\": \"CUB1-EGF-CUB2 crystal structure with mutagenesis/SPR, plus MASP1/3−/− mouse with recombinant reconstitution\",\n      \"pmids\": [\"18596036\", \"18424734\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not directly visualize a MASP-1/MASP-2 transactivation complex\", \"Relative contribution of MASP-1 vs MASP-2 binding sites in mixed complexes unclear\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Explained MASP-1's broad substrate specificity and confirmed PAR-mediated endothelial signaling, distinguishing it mechanistically from the narrow-specificity complement proteases.\",\n      \"evidence\": \"Catalytic-region crystal structure at 2.55 Å and PAR4 cleavage/Ca2+/NF-κB/p38 signaling assays in HUVECs\",\n      \"pmids\": [\"19564340\", \"19667088\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the full physiological substrate repertoire\", \"In vivo relevance of endothelial PAR4 signaling not tested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identified MAp44 as a fourth MASP1/3 splice product acting as a competitive inhibitor of the lectin pathway, establishing intragenic regulatory control.\",\n      \"evidence\": \"SPR binding kinetics, ELISA, and complement inhibition assays\",\n      \"pmids\": [\"19917686\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo concentration-dependent regulation not quantified\", \"Tissue-specific splice product ratios unaddressed\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Proved MASP-1 is the exclusive activator of MASP-2 in normal serum and an essential initiator, settling the hierarchy of lectin pathway protease activation.\",\n      \"evidence\": \"Monospecific MASP-1/MASP-2 inhibitor proteins and patient serum reconstitution with co-complex ELISA, supported by Michaelis-complex crystal structures\",\n      \"pmids\": [\"22691502\", \"22966085\", \"22511776\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative kinetics of transactivation within native complexes not fully defined\", \"Whether all MBL/ficolin complexes carry both proteases unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Quantified MASP-1's exceptionally high zymogen autoactivation and showed it cleaves both MASP-2 and MASP-3 proenzymes, explaining how the pathway is triggered without an upstream activator.\",\n      \"evidence\": \"Rate-constant measurements with zymogen/active-site mutants and proenzyme MASP-1 crystal structure at 2.5 Å\",\n      \"pmids\": [\"23386610\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trigger that converts surface binding into autoactivation in vivo not defined\", \"Conformational dynamics modeled crystallographically rather than in solution\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Clarified the architecture of transactivation by showing MASP-1/MASP-2 co-complexes form only via MBL/ficolin scaffolds and that MAp44 disrupts these complexes.\",\n      \"evidence\": \"Gel filtration, ELISA co-complex detection, and complement activation assays\",\n      \"pmids\": [\"23785123\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab biochemical detection without structural confirmation\", \"Direct vs scaffold-mediated heterodimer contributions partly resolved only by later fragment studies\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Mapped MASP-1/MASP-2 and MASP-1/MASP-3 dimerization behavior through CUB1-EGF-CUB2 fragments, defining how subunit pairing is governed by Ca2+.\",\n      \"evidence\": \"Size-exclusion chromatography, native PAGE, and EDTA dissociation/re-association with recombinant fragments\",\n      \"pmids\": [\"24424083\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Used isolated fragments rather than full-length proteins\", \"Physiological relevance of heterodimers vs homodimers in serum not established\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showed native serum MBL-MASP complexes activate endothelium and that this requires MASP-1 catalytic activity, anchoring the signaling role to physiological complexes.\",\n      \"evidence\": \"Ca2+ signaling assays in HUVECs comparing native complexes, recombinant fragments, and zymogen mutant; plus cytokine/chemotaxis assays\",\n      \"pmids\": [\"24472859\", \"24489848\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo endothelial activation by MASP-1 not demonstrated\", \"Receptor(s) mediating cytokine induction not fully resolved in these studies\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Demonstrated MASP-1 cross-talk with coagulation by cleaving fibrinogen and factor XIII at thrombin-like sites, opening the link between complement and hemostasis.\",\n      \"evidence\": \"In vitro cleavage assays, SDS-PAGE, N-terminal sequencing with thrombin comparison\",\n      \"pmids\": [\"18456010\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Slow turnover (~650-fold lower than thrombin) leaves physiological significance to be weighted\", \"In vivo contribution to clotting not addressed here\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Established MASP-1 as a bradykinin-generating protease via kininogen cleavage, connecting it to vascular permeability and inflammation.\",\n      \"evidence\": \"Proteomics, SDS-PAGE, HPLC bradykinin detection, and kinetics with C1-inhibitor control\",\n      \"pmids\": [\"21625439\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo bradykinin release by MASP-1 not demonstrated\", \"Relative contribution versus kallikrein not quantified\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined the prothrombin cleavage mechanism, showing MASP-1 activates prothrombin via two parallel cleavage routes generating alternative thrombin species.\",\n      \"evidence\": \"Arginine-to-glutamine prothrombin mutants, N-terminal sequencing, and thrombelastography (also 2012/2014 plasma and purified-system clot assays)\",\n      \"pmids\": [\"25745807\", \"26645987\", \"22536427\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological flux through MASP-1-driven prothrombin activation in vivo not quantified\", \"Interplay with TAFI/clot-lysis effects not fully integrated\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identified MASP-3 as the exclusive activator of pro-factor D in resting blood, establishing a direct molecular bridge between the lectin and alternative complement pathways.\",\n      \"evidence\": \"Evolved monospecific MASP inhibitors in resting blood with pro-FD activation assays and kinetics (with companion 2015 plasma assays)\",\n      \"pmids\": [\"27535802\", \"26673137\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether residual MASP-3-independent FD maturation contributes was clarified only later\", \"Spatial site of pro-FD activation in vivo unknown\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Linked 3MC-associated MASP-3 mutations to loss of factor D maturase activity, explaining the alternative-pathway defect while revealing MASP-3-independent maturation also exists.\",\n      \"evidence\": \"Isoelectric focusing of FD variants, mutant enzyme characterization, MASP-3-depleted serum, patient sera, and KO mice\",\n      \"pmids\": [\"28794230\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the MASP-3-independent FD maturase not determined\", \"How 3MC craniofacial phenotype relates to FD maturation defect unclear\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Showed MASP-1 contributes to surface-specific alternative pathway activation (LPS but not zymosan) and to clot formation under flow, extending its role into pathogen-context and physiological hemostasis.\",\n      \"evidence\": \"Specific MASP-1 inhibitors (SGMI-1 and others) in AP assays and a microvascular endothelialized whole-blood clot model\",\n      \"pmids\": [\"29475986\", \"29324883\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of the LPS-specific MASP-1 requirement not elucidated\", \"Single-lab flow models await independent replication\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Defined PAR1-dependent endothelial permeability signaling and confirmed in monospecific KO mice that MASP-1 (not MASP-3) drives lectin pathway activation while MASP-3 drives FD maturation, cleanly separating the two splice products' physiological roles.\",\n      \"evidence\": \"Impedance/permeability/Ca2+/Rho-kinase assays in HUVECs and monospecific MASP-1-KO and MASP-3-KO mice with pathway activity readouts\",\n      \"pmids\": [\"31130964\", \"31399515\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo permeability consequences of MASP-1 PAR1 signaling not tested in the KO mice\", \"Crosstalk between bradykinin-receptor upregulation and PAR signaling unresolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Extended MASP-1 biology to organ fibrosis, showing hepatocyte-derived MASP1 in extracellular vesicles activates hepatic stellate cells via p38 MAPK/ATF2 to promote liver fibrogenesis.\",\n      \"evidence\": \"CCl4/NASH mouse models, EV proteomics, siRNA knockdown, and p38 MAPK signaling assays\",\n      \"pmids\": [\"35849032\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether catalytic activity of MASP1 is required for HSC activation not fully isolated\", \"Single-lab study awaiting independent confirmation\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the diverse non-complement substrates (coagulation factors, kininogen, PAR receptors) are integrated in vivo, and the identity of the MASP-3-independent factor D maturase, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vivo quantification of MASP-1's relative contribution to coagulation versus dedicated coagulation proteases\", \"Identity of MASP-3-independent FD maturase unknown\", \"Mechanism coupling MASP-1 endothelial signaling to systemic vascular phenotypes undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [2, 7, 9, 12, 13, 14, 16, 27]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [5, 11, 12, 13, 14]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 23]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [7, 19]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [1, 2, 4, 29, 32]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [34]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 2, 3, 4, 6, 26]},\n      {\"term_id\": \"R-HSA-109582\", \"supporting_discovery_ids\": [12, 14, 16, 33]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [7, 17, 19, 34]}\n    ],\n    \"complexes\": [\n      \"MBL-MASP lectin pathway initiation complex\",\n      \"ficolin-MASP complex\",\n      \"CL-11 (collectin-11) initiation complex\",\n      \"MASP-1/C1-inhibitor complex\"\n    ],\n    \"partners\": [\n      \"MASP2\",\n      \"MBL2\",\n      \"FCN1\",\n      \"COLEC11\",\n      \"SERPING1\",\n      \"C2\",\n      \"CFD\",\n      \"F2\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}