{"gene":"F5","run_date":"2026-04-28T17:46:03","timeline":{"discoveries":[{"year":1987,"finding":"Complete cDNA cloning of human Factor V revealed a 2224-amino-acid single-chain protein with a domain structure A1-A2-B-A3-C1-C2 (triplicated A domains homologous to Factor VIII and ceruloplasmin, duplicated C domains, and a large B domain containing 35+ tandem 9-amino-acid repeats with 37 potential N-linked glycosylation sites, 25 in the B domain).","method":"cDNA cloning and sequence analysis of human fetal liver library; direct amino acid sequence comparison with Factor VIII and ceruloplasmin","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 — foundational full-length cDNA sequencing establishing primary structure; highly cited and replicated","pmids":["3110773"],"is_preprint":false},{"year":1982,"finding":"Thrombin activates single-chain Factor V (Mr ~330,000) by limited proteolysis, generating Factor Va with 25–30-fold higher cofactor activity. Activation produces fragments D (105 kDa) and F1F2 (71–74 kDa doublet) held by noncovalent interactions, plus two activation peptides (E and C1); reconstitution of D and F1F2 restores cofactor activity, establishing that these two fragments constitute the biologically active cofactor.","method":"Purification of human Factor V; SDS-PAGE analysis of thrombin cleavage products; reconstitution experiments with isolated fragments; NH2-terminal sequencing","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with purified components plus fragment characterization; highly cited foundational study","pmids":["7076681"],"is_preprint":false},{"year":1988,"finding":"Factor Va functions as an essential nonenzymatic cofactor in the prothrombinase complex (Factor Xa + Factor Va on phospholipid membranes) and in the intrinsic Xase complex, dramatically accelerating thrombin generation; Factor V is activated by thrombin and inactivated by activated protein C (APC), which cleaves cofactors Va and VIIIa to limit clot formation.","method":"Biochemical reconstitution of coagulation enzyme complexes; kinetic analysis; review synthesizing multiple experimental studies","journal":"Annual review of biochemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstituted enzyme complex activity, synthesizing multiple experimental findings; highly cited","pmids":["3052293"],"is_preprint":false},{"year":1989,"finding":"Activated protein C (APC), formed on the endothelial cell surface when thrombin binds thrombomodulin, proteolytically inactivates Factor Va by cleavage, with protein S serving as a nonenzymatic APC cofactor; intact Factor V also serves as an APC cofactor in the inactivation pathway.","method":"Biochemical characterization of protein C activation on endothelial surfaces; proteolysis assays of Factor Va inactivation; identification of protein S cofactor requirement","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution of APC pathway; highly cited foundational study","pmids":["2538457"],"is_preprint":false},{"year":1994,"finding":"APC inactivates Factor Va by sequential proteolytic cleavages at Arg506, Arg306, and Arg679 on the heavy chain; cleavage at Arg506 precedes and is required for cleavage at Arg306 and Arg679; inactivation (>90% loss of cofactor activity) only occurs efficiently in the presence of phospholipid membranes (phosphatidylserine/phosphatidylcholine vesicles); in the absence of membrane, Factor Va retains ~80% activity even after APC cleavage at Arg506.","method":"In vitro APC cleavage assays of purified human Factor V and Factor Va; SDS-PAGE fragment identification; cofactor activity assays with and without phospholipid vesicles","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — rigorous in vitro reconstitution with purified proteins, multiple cleavage sites mapped, membrane dependence demonstrated; highly cited","pmids":["7989361"],"is_preprint":false},{"year":1994,"finding":"The phenotype of APC resistance is caused by a single point mutation in the Factor V gene (G→A at nucleotide 1691, predicting Arg506Gln substitution), producing FV Leiden (FV Q506), which is activated normally by thrombin or Factor Xa but is impaired in inactivation by APC; the allelic frequency is ~2% in the Dutch population.","method":"Family linkage study; DNA sequencing of Factor V gene; functional assays of APC resistance in plasma","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1–2 — mutation identified by sequencing linked to functional APC resistance phenotype; landmark paper with >3500 citations","pmids":["8164741"],"is_preprint":false},{"year":1994,"finding":"Linkage analysis in a family with thrombophilia showed 100% cosegregation of Factor V gene polymorphisms with APC resistance, and identified the Arg506Gln point mutation in the APC cleavage site as the cause; purified Factor V expressed an anticoagulant activity that corrected APC resistance in plasma, establishing Factor V as an APC cofactor.","method":"RFLP linkage analysis in familial thrombophilia kindred; Factor V gene sequencing; purified Factor V cofactor activity assay","journal":"Lancet","confidence":"High","confidence_rationale":"Tier 1–2 — genetic linkage plus functional correction with purified protein; highly cited","pmids":["7911873"],"is_preprint":false},{"year":1998,"finding":"A second APC cleavage site mutation in Factor V, Arg306→Thr (Factor V Cambridge), causes APC resistance and thrombosis, confirming the physiological importance of the Arg306 APC cleavage site in regulation of the prothrombinase complex.","method":"Sequencing of Factor V gene in patients with APC resistance lacking FV Leiden; clinical phenotyping; exclusion of other APC resistance causes","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 — genetic identification with functional phenotype (APC resistance); single-lab study","pmids":["9454742"],"is_preprint":false},{"year":2000,"finding":"The R2 haplotype of the Factor V gene (containing the 4070G variant) is associated with an altered ratio of two functionally distinct FV plasma isoforms: carriers of the Ala2194Gly variant (C2 domain) show a relative increase of the more thrombogenic, more glycosylated FV isoform (FV1) versus FV2, suggesting that differential glycosylation (determined by C2 domain sequence) modulates FV isoform distribution and thrombotic risk.","method":"Molecular genetics (sequencing of R2 homozygotes); chromatographic separation of FV1 and FV2 isoforms; biochemical characterization in plasma","journal":"Thrombosis and haemostasis","confidence":"Medium","confidence_rationale":"Tier 2–3 — biochemical separation of isoforms with genetic correlation; single-lab study","pmids":["10744138"],"is_preprint":false},{"year":2002,"finding":"Recombinant Factor V Cambridge (Arg306Thr) and FV Hong Kong (Arg306Gly) both produce intermediate APC resistance patterns (between wild-type and FV Leiden). In the absence of protein S, APC causes only partial inactivation of these FVa variants. In the presence of protein S, both variants are nearly completely inactivated through stimulation of cleavage at Arg679. Both variants show slightly impaired APC cofactor activity in FVIIIa degradation assays.","method":"Recombinant expression of FV variants; APC inactivation kinetics assays with and without protein S; FVIIIa degradation assays","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro system with recombinant proteins; multiple functional assays; explains clinical phenotype","pmids":["12091344"],"is_preprint":false},{"year":2003,"finding":"MCFD2 (an EF-hand domain protein) mutations cause combined Factor V and Factor VIII deficiency (F5F8D) with a phenotype indistinguishable from LMAN1 mutations. MCFD2 is localized to the ERGIC through a direct, calcium-dependent interaction with LMAN1, and the MCFD2-LMAN1 complex forms a specific cargo receptor for ER-to-Golgi transport of Factor V and Factor VIII.","method":"Mutation screening of F5F8D patients; subcellular localization by immunofluorescence; Co-IP demonstrating MCFD2-LMAN1 calcium-dependent interaction; genetic analysis","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 1–2 — direct protein interaction demonstrated, subcellular localization established, human genetics validated; highly cited","pmids":["12717434"],"is_preprint":false},{"year":2003,"finding":"Coinheritance of FV Leiden in a patient with severe FVII deficiency (FVII Lazio) increases thrombin generation, particularly in the presence of APC, explaining a milder bleeding phenotype. Experiments with purified FV or FV Leiden reconstituted into doubly-deficient plasma confirmed that FV Leiden generates more FXa and thrombin than normal FV due to APC resistance of FVa Leiden.","method":"Thrombin generation assays in patient plasma; FXa and FVa generation assays; reconstitution with purified normal FV vs. FV Leiden in doubly-deficient plasma","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1 — purified protein reconstitution with functional readout; demonstrates FV Leiden APC resistance mechanism in prothrombinase context","pmids":["12881304"],"is_preprint":false},{"year":2009,"finding":"Combined FV and FVIII deficiency (F5F8D) is caused by mutations in LMAN1 or MCFD2, which encode a calcium-dependent heteromeric cargo receptor complex that cycles between the ER and ERGIC. Missense mutations in MCFD2 EF-hand domains abolish interaction with LMAN1. MCFD2 mutations generally cause lower FV and FVIII levels than LMAN1 mutations. The LMAN1-MCFD2 complex acts as a cargo receptor for ER-to-Golgi transport of both FV and FVIII.","method":"Review synthesizing genetic and biochemical studies; EF-hand domain mutation analysis; LMAN1-MCFD2 interaction studies","journal":"British journal of haematology","confidence":"High","confidence_rationale":"Tier 2 — synthesis of multiple experimental studies establishing cargo receptor mechanism; supported by genetic and biochemical data","pmids":["19183188"],"is_preprint":false},{"year":2011,"finding":"LMAN1-deficient (Lman1−/−) mice exhibit ~50% reduction in plasma FV, plasma FVIII, and platelet FV levels, confirming LMAN1 as a cargo receptor required for efficient ER-to-Golgi transport of FV. The reduction is less severe than in human F5F8D patients (5–30%), suggesting partial redundancy or strain-dependent effects. ER in Lman1−/− hepatocytes is slightly distended with accumulation of α1-antitrypsin and GRP78.","method":"Lman1 knockout mouse model; plasma FV and FVIII level measurement; platelet FV measurement; electron microscopy of hepatocytes; in vitro COPII vesicle formation assay","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1–2 — genetic knockout with direct measurement of FV secretion; multiple orthogonal methods","pmids":["21795745"],"is_preprint":false},{"year":2011,"finding":"A homozygous deep-intronic F5 mutation (IVS8 +268A→G) causes inclusion of a pseudo-exon with an in-frame stop codon in F5 mRNA, resulting in severe FV deficiency with undetectable FV activity in plasma and platelets. This patient showed no thrombin generation in platelet-rich plasma triggered with 1–50 pM tissue factor, demonstrating that platelet FV is essential for thrombin generation support in PRP.","method":"F5 gene sequencing; RT-PCR/cDNA analysis of aberrant splicing; prothrombinase-based FV activity assay; thrombin generation in PRP; Western blotting for FV antigen in platelets","journal":"Journal of thrombosis and haemostasis","confidence":"High","confidence_rationale":"Tier 1–2 — molecular characterization of splicing defect with functional consequences; first deep-intronic F5 mutation described","pmids":["21320286"],"is_preprint":false},{"year":2013,"finding":"Crystal structures of the LMAN1 carbohydrate recognition domain (CRD) bound to Man-α-1,2-Man (terminal moiety of high-mannose glycans) reveal the central mannose-binding site; mutagenesis identifies His178 and Gly251/252 as critical for FV/FVIII cargo binding. Mannobiose binding is relatively pH-independent in the ER-to-Golgi range but sensitive to lowered Ca2+ concentrations, suggesting that compartmental Ca2+ changes regulate glycoprotein cargo binding and release from the LMAN1·MCFD2 complex.","method":"X-ray crystallography of LMAN1-CRD with mannobiose; site-directed mutagenesis; in vitro carbohydrate binding assays; Ca2+ titration experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — crystal structure plus mutagenesis plus in vitro binding assays; defines molecular basis of FV/FVIII cargo recognition","pmids":["23709226"],"is_preprint":false},{"year":2014,"finding":"An apparently synonymous F5 variant (c.1281C>G in exon 8) activates a cryptic donor splice site and abolishes an exonic splicing enhancer, causing half of the patient's F5 mRNA to lack the last 18 nucleotides of exon 8. The aberrantly spliced mRNA encodes a putative FV protein lacking amino acids 427–432 that is poorly secreted and nonfunctional when expressed in COS-1 cells. A mutation-specific morpholino antisense oligonucleotide partially corrects the splicing defect.","method":"F5 gene sequencing; RT-PCR/cDNA analysis; F5 minigene assay; bioinformatics splice site prediction; COS-1 cell expression of mutant protein; morpholino antisense oligonucleotide correction","journal":"Haemophilia","confidence":"High","confidence_rationale":"Tier 1–2 — minigene functional validation, cell expression, antisense correction; multiple orthogonal methods","pmids":["25470420"],"is_preprint":false},{"year":2021,"finding":"A novel FV missense mutation Ala2086Asp (FV Besançon) in the C2 domain favors a 'closed conformation' predicting impaired phospholipid binding, causes markedly decreased FV secretion, and paradoxically induces a hypercoagulable/thrombotic state in an FV-deficient patient. Recombinant FVa Besançon shows slightly unfavorable kinetics of prothrombin activation (Km, Vmax) but a lower rate of APC-catalyzed inactivation in the presence of protein S, abolishing FV APC-cofactor activity.","method":"Patient clinical characterization; F5 gene sequencing; recombinant FV Besançon expression; thrombin generation assays in platelet-poor and platelet-rich plasma; APC resistance testing; prothrombinase kinetics with diluted plasma reconstituted with recombinant FVa; TFPI antigen/activity measurement","journal":"Journal of thrombosis and haemostasis","confidence":"High","confidence_rationale":"Tier 1–2 — recombinant protein functional characterization with kinetic assays; multiple mechanistic readouts; explains paradoxical thrombosis in FV-deficient patient","pmids":["33605529"],"is_preprint":false},{"year":2021,"finding":"A novel heterozygous 832-bp deletion within F5 exon 13 (F5-Atlanta) enhances alternative splicing at East Texas (ET) splice sites within exon 13, producing a FV-Short isoform with a truncated B domain. This alternatively spliced transcript markedly elevates circulating total and free TFPIα levels. The findings establish that cis-acting regulatory sequences within F5 exon 13 control alternative splicing at ET splice sites and thereby regulate circulating FV-Short and TFPIα levels.","method":"Patient plasma analysis (TFPI levels, FV isoform sizing); F5 cDNA sequencing; heterologous expression in mammalian cells to recapitulate alternative splicing","journal":"Journal of thrombosis and haemostasis","confidence":"High","confidence_rationale":"Tier 1–2 — mechanistic model validated by recombinant expression; patient plasma data corroborated; identifies cis-regulatory elements in F5 exon 13","pmids":["33773040"],"is_preprint":false},{"year":2023,"finding":"FV-Short, a naturally occurring splice isoform of Factor V with a truncated B domain, binds TFPIα with high affinity. Together with protein S, FV-Short forms a high-affinity trimolecular complex (FV-Short/protein S/TFPIα) that synergistically stimulates the FXa-inhibitory activity of TFPIα, functioning as a natural anticoagulant threshold mechanism. In the East Texas bleeding disorder, this complex is elevated ~10-fold, explaining the bleeding phenotype.","method":"Synthesis of experimental findings on FV-Short discovery; binding affinity measurements; functional TFPIα inhibition assays; patient plasma characterization","journal":"Journal of thrombosis and haemostasis","confidence":"High","confidence_rationale":"Tier 1–2 — synthesis of binding studies and functional assays establishing anticoagulant mechanism of FV-Short; replicated across multiple studies","pmids":["36746318"],"is_preprint":false},{"year":2004,"finding":"Three F5 gene mutations were identified in two Chinese pedigrees with inherited FV deficiency: (i) homozygous IVS8 -2A>G (splicing mutation) that abolishes the canonical splice acceptor site and activates a cryptic acceptor 24 bp upstream, inserting 8 extra amino acids into FV; (ii) heterozygous 2238-9del AG (frameshift, exon 13, introducing premature stop at AA 689); and (iii) heterozygous G6410T (exon 23, missense Gly2079Val).","method":"PCR amplification and sequencing of all 25 F5 exons; RT-PCR/cDNA analysis of aberrant mRNA from patient lymphocytes","journal":"Haemophilia","confidence":"Medium","confidence_rationale":"Tier 2 — molecular characterization of splicing mechanism by cDNA analysis; functional consequence (FV deficiency) established by clinical phenotype","pmids":["15086325"],"is_preprint":false}],"current_model":"Coagulation Factor V (F5) is a large plasma glycoprotein (A1-A2-B-A3-C1-C2 domain structure) that circulates as a procofactor and, upon thrombin-mediated activation (cleavage generating heavy and light chains held noncovalently), becomes Factor Va — a critical nonenzymatic cofactor of the prothrombinase complex (Factor Xa/Factor Va/phospholipid/Ca²⁺) that dramatically accelerates thrombin generation; Factor Va is inactivated by APC through sequential phospholipid-dependent cleavages at Arg506, Arg306, and Arg679 (with protein S as cofactor), and the common FV Leiden mutation (Arg506Gln) impairs this inactivation causing thrombophilia; Factor V is also secreted by an LMAN1-MCFD2 calcium-dependent cargo receptor complex in the ER-to-Golgi pathway, and a naturally occurring splice isoform (FV-Short) with a truncated B domain forms a high-affinity trimolecular complex with TFPIα and protein S that provides an anticoagulant threshold by synergistically stimulating FXa inhibition."},"narrative":{"teleology":[{"year":1982,"claim":"Establishing how Factor V is converted to its active cofactor form resolved the long-standing question of how a single-chain procofactor gains catalytic relevance: thrombin generates a heavy chain (D fragment) and light chain (F1F2 doublet) whose noncovalent association reconstitutes cofactor activity.","evidence":"Purification of human FV; SDS-PAGE of thrombin cleavage products; reconstitution of cofactor activity from isolated fragments","pmids":["7076681"],"confidence":"High","gaps":["Precise thrombin cleavage sites on the procofactor were not mapped at single-residue resolution","Contribution of individual domains to prothrombinase assembly was not defined"]},{"year":1987,"claim":"Determination of the complete primary structure of Factor V revealed its A1-A2-B-A3-C1-C2 domain architecture and homology to Factor VIII and ceruloplasmin, providing the structural framework for interpreting all subsequent mutagenesis and disease-mutation studies.","evidence":"Full-length cDNA cloning from human fetal liver library with sequence analysis","pmids":["3110773"],"confidence":"High","gaps":["No three-dimensional structure was available","Function of the large, heavily glycosylated B domain remained unclear"]},{"year":1988,"claim":"Reconstitution of the prothrombinase and intrinsic Xase complexes demonstrated that Factor Va is the critical nonenzymatic cofactor that dramatically accelerates thrombin generation, and that APC limits coagulation by proteolytically inactivating both Factor Va and Factor VIIIa.","evidence":"Biochemical reconstitution of coagulation enzyme complexes with kinetic analysis","pmids":["3052293","2538457"],"confidence":"High","gaps":["APC cleavage sites on FVa were not yet mapped","The role of protein S as APC cofactor was not molecularly defined"]},{"year":1994,"claim":"Mapping APC cleavage sites at Arg506, Arg306, and Arg679 — and the near-simultaneous discovery that the Arg506Gln (FV Leiden) mutation causes APC resistance and familial thrombophilia — established the molecular basis of the predominant inherited thrombotic risk factor and the obligate sequential inactivation pathway of Factor Va.","evidence":"In vitro APC cleavage assays with purified FVa and phospholipid vesicles; family linkage study and DNA sequencing in thrombophilia kindreds; APC resistance assays","pmids":["7989361","8164741","7911873"],"confidence":"High","gaps":["Structural basis of APC–FVa interaction was not resolved","Whether protein S specifically redirects APC cleavage hierarchy was not yet shown"]},{"year":1998,"claim":"Identification of a second APC-site mutation (Arg306Thr, FV Cambridge) in a thrombophilic patient confirmed that Arg306 is a physiologically important APC cleavage site independent of Arg506.","evidence":"F5 gene sequencing in APC-resistant patients lacking FV Leiden; clinical phenotyping","pmids":["9454742"],"confidence":"Medium","gaps":["Only a single kindred was described","Relative contribution of Arg306 versus Arg506 cleavage to overall FVa inactivation was not quantified"]},{"year":2002,"claim":"Recombinant expression of FV Cambridge and FV Hong Kong variants demonstrated that Arg306 mutations produce intermediate APC resistance and that protein S rescues near-complete inactivation by stimulating cleavage at Arg679, quantifying the protein S contribution to the alternative inactivation pathway.","evidence":"Recombinant FV variant expression; APC inactivation kinetics ± protein S; FVIIIa degradation assays","pmids":["12091344"],"confidence":"High","gaps":["Structural basis of protein S stimulation of Arg679 cleavage was unknown","In vivo relevance of the Arg679 cleavage site was not tested"]},{"year":2003,"claim":"Discovery that MCFD2 and LMAN1 form a calcium-dependent cargo receptor complex required for ER-to-Golgi transport of both Factor V and Factor VIII explained the molecular basis of combined F5F8 deficiency and identified the secretory pathway mechanism for FV.","evidence":"Mutation screening of F5F8D patients; co-immunoprecipitation of MCFD2–LMAN1; subcellular localization by immunofluorescence","pmids":["12717434"],"confidence":"High","gaps":["Direct binding of LMAN1–MCFD2 to FV cargo had not been reconstituted","Whether the complex recognizes FV glycans or polypeptide determinants was unresolved"]},{"year":2011,"claim":"LMAN1 knockout mice confirmed in vivo that LMAN1 is required for efficient FV (and FVIII) secretion, though the ~50% reduction was milder than in human F5F8D patients, suggesting partial redundancy or species differences in the secretory pathway.","evidence":"Lman1−/− mouse model; plasma FV/FVIII and platelet FV measurement; electron microscopy of hepatocyte ER","pmids":["21795745"],"confidence":"High","gaps":["Identity of any redundant ER-to-Golgi cargo receptor for FV was unknown","Platelet-specific FV trafficking mechanism was not defined"]},{"year":2013,"claim":"Crystal structures of the LMAN1 carbohydrate recognition domain bound to mannobiose defined how LMAN1 recognizes high-mannose glycans on FV/FVIII cargo, and mutagenesis identified critical residues (His178, Gly251/252); Ca²⁺-dependent binding suggested compartmental Ca²⁺ gradients regulate cargo release.","evidence":"X-ray crystallography of LMAN1-CRD with mannobiose; site-directed mutagenesis; Ca²⁺ titration binding assays","pmids":["23709226"],"confidence":"High","gaps":["No structure of the full LMAN1–MCFD2–FV ternary complex","Which specific glycan sites on FV are recognized was not determined"]},{"year":2021,"claim":"Discovery of FV-Short as a naturally occurring splice isoform and identification of cis-regulatory elements in F5 exon 13 that control alternative splicing at East Texas splice sites established a previously unrecognized regulatory layer linking F5 mRNA processing to circulating TFPIα levels and anticoagulant capacity.","evidence":"Patient plasma analysis; F5 cDNA sequencing of the F5-Atlanta deletion; heterologous expression recapitulating alternative splicing","pmids":["33773040","33605529"],"confidence":"High","gaps":["Trans-acting splicing regulators controlling FV-Short production were not identified","Quantitative contribution of FV-Short to normal hemostatic balance in healthy individuals was not established"]},{"year":2023,"claim":"Demonstration that FV-Short, protein S, and TFPIα form a high-affinity trimolecular complex that synergistically inhibits Factor Xa revealed a dual procoagulant/anticoagulant role for Factor V and explained the bleeding phenotype of the East Texas disorder.","evidence":"Binding affinity measurements; functional TFPIα inhibition assays; patient plasma characterization","pmids":["36746318"],"confidence":"High","gaps":["Structural basis of the FV-Short/protein S/TFPIα complex is unresolved","Whether therapeutic modulation of FV-Short splicing can rebalance hemostasis is untested"]},{"year":null,"claim":"Major open questions include the three-dimensional structure of intact Factor Va in the prothrombinase complex, the identity of trans-acting regulators of FV-Short alternative splicing, and the structural determinants that allow Factor V to switch between procoagulant cofactor (in prothrombinase) and anticoagulant cofactor (for APC and as FV-Short/TFPIα complex) roles.","evidence":"","pmids":[],"confidence":"High","gaps":["No high-resolution structure of FVa within the prothrombinase complex","Trans-acting regulators of FV-Short splicing unknown","Molecular basis of FV dual procoagulant/anticoagulant switching unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[2,3,4,6,19]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[4,17]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[1,2,5,14,19]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[10,12,13,15]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[10,12]}],"pathway":[{"term_id":"R-HSA-109582","term_label":"Hemostasis","supporting_discovery_ids":[1,2,3,4,5,6,9,11,17,19]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[10,12,13,15]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[5,6,7,14]}],"complexes":["Prothrombinase complex (FXa/FVa/phospholipid/Ca²⁺)","FV-Short/TFPIα/protein S anticoagulant complex"],"partners":["F10","PROC","PROS1","TFPI","LMAN1","MCFD2","F2"],"other_free_text":[]},"mechanistic_narrative":"Coagulation factor V is a large plasma glycoprotein (A1-A2-B-A3-C1-C2 domain architecture) that circulates as an inactive procofactor and, upon thrombin-mediated proteolysis generating noncovalently associated heavy and light chains, becomes Factor Va — the essential nonenzymatic cofactor of the prothrombinase complex (Factor Xa/Factor Va/phospholipid/Ca²⁺) that dramatically accelerates prothrombin conversion to thrombin [PMID:7076681, PMID:3052293]. Factor Va is inactivated by activated protein C (APC) through sequential phospholipid-dependent cleavages at Arg506, Arg306, and Arg679, with protein S as cofactor; the FV Leiden mutation (Arg506Gln) impairs this inactivation and is the most common inherited cause of thrombophilia [PMID:7989361, PMID:8164741]. Efficient ER-to-Golgi secretion of Factor V requires the LMAN1–MCFD2 calcium-dependent cargo receptor complex, and biallelic loss-of-function mutations in LMAN1 or MCFD2 cause combined Factor V and Factor VIII deficiency [PMID:12717434, PMID:21795745]. A naturally occurring splice isoform, FV-Short, forms a high-affinity trimolecular complex with TFPIα and protein S that synergistically inhibits Factor Xa, establishing an anticoagulant threshold whose dysregulation underlies the East Texas bleeding disorder [PMID:36746318, PMID:33773040]."},"prefetch_data":{"uniprot":{"accession":"P12259","full_name":"Coagulation factor V","aliases":["Activated protein C cofactor","Proaccelerin, labile factor"],"length_aa":2224,"mass_kda":251.7,"function":"Central regulator of hemostasis. It serves as a critical cofactor for the prothrombinase activity of factor Xa that results in the activation of prothrombin to thrombin","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/P12259/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/F5","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/F5","total_profiled":1310},"omim":[{"mim_id":"621535","title":"SPINOCEREBELLAR ATAXIA 52; SCA52","url":"https://www.omim.org/entry/621535"},{"mim_id":"621424","title":"LEUKOENCEPHALOPATHY WITHOUT LACUNAE, ADULT-ONSET; LUCAO","url":"https://www.omim.org/entry/621424"},{"mim_id":"621143","title":"HOLOPROSENCEPHALY 10; 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/F4, and /F5.","date":"2014","source":"Analytical chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/24605815","citation_count":17,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"19020903","id":"PMC_19020903","title":"The joint association between F5 gene polymorphisms and maternal smoking during pregnancy on preterm delivery.","date":"2008","source":"Human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/19020903","citation_count":17,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"20206697","id":"PMC_20206697","title":"Expression and purification of an anti-clenbuterol single chain Fv antibody in Escherichia coli.","date":"2010","source":"Protein expression and purification","url":"https://pubmed.ncbi.nlm.nih.gov/20206697","citation_count":17,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"25470420","id":"PMC_25470420","title":"Characterization of an apparently synonymous F5 mutation causing aberrant splicing and factor V 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variations have association with preeclampsia in Pakistani patients: a case control study.","date":"2019","source":"BMC medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/31646966","citation_count":15,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"11005928","id":"PMC_11005928","title":"Construction and structural modeling of a single-chain Fv-asparaginase fusion protein resistant to proteolysis.","date":"2000","source":"Biotechnology and bioengineering","url":"https://pubmed.ncbi.nlm.nih.gov/11005928","citation_count":15,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"25200834","id":"PMC_25200834","title":"The concentrations of EGFR, LRG1, ITIH4, and F5 in serum correlate with the number of colonic adenomas in ApcPirc/+ rats.","date":"2014","source":"Cancer prevention research (Philadelphia, Pa.)","url":"https://pubmed.ncbi.nlm.nih.gov/25200834","citation_count":15,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"8047074","id":"PMC_8047074","title":"Molecular cloning, expression and mutagenesis of an anti-insulin single chain Fv (scFv).","date":"1994","source":"Molecular immunology","url":"https://pubmed.ncbi.nlm.nih.gov/8047074","citation_count":14,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"8889803","id":"PMC_8889803","title":"Construction and expression of bi-functional proteins of single-chain Fv with effector domains.","date":"1996","source":"Journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/8889803","citation_count":14,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"15086325","id":"PMC_15086325","title":"Identification of three F5 gene mutations associated with inherited coagulation factor V deficiency in two Chinese pedigrees.","date":"2004","source":"Haemophilia : the official journal of the World Federation of 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disorders drug targets","url":"https://pubmed.ncbi.nlm.nih.gov/29546836","citation_count":13,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"11320404","id":"PMC_11320404","title":"Single chain Fv: a ligand in receptor-mediated gene delivery.","date":"2001","source":"Gene therapy","url":"https://pubmed.ncbi.nlm.nih.gov/11320404","citation_count":13,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"20460695","id":"PMC_20460695","title":"Development of a gene transfer system for the mycelia of Flammulina velutipes Fv-1 strain.","date":"2010","source":"Bioscience, biotechnology, and biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/20460695","citation_count":13,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"11482347","id":"PMC_11482347","title":"Antibody engineering for targeted therapy of cancer: recombinant Fv-immunotoxins.","date":"2001","source":"Current pharmaceutical 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microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/24632257","citation_count":12,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"8164741","id":"PMC_8164741","title":"Mutation in blood coagulation factor V associated with resistance to activated protein C.","date":"1994","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/8164741","citation_count":3563,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"12477932","id":"PMC_12477932","title":"Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences.","date":"2002","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/12477932","citation_count":1479,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"10391209","id":"PMC_10391209","title":"Characterization of single-nucleotide polymorphisms in coding regions of human genes.","date":"1999","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/10391209","citation_count":1381,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"26186194","id":"PMC_26186194","title":"The BioPlex Network: A Systematic Exploration of the Human Interactome.","date":"2015","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/26186194","citation_count":1118,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"28514442","id":"PMC_28514442","title":"Architecture of the human interactome defines protein communities and disease networks.","date":"2017","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/28514442","citation_count":1085,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"2538457","id":"PMC_2538457","title":"The roles of protein C and thrombomodulin in the regulation of blood coagulation.","date":"1989","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/2538457","citation_count":927,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"11076863","id":"PMC_11076863","title":"DNA cloning using in vitro site-specific recombination.","date":"2000","source":"Genome research","url":"https://pubmed.ncbi.nlm.nih.gov/11076863","citation_count":815,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"33961781","id":"PMC_33961781","title":"Dual proteome-scale networks reveal cell-specific remodeling of the human interactome.","date":"2021","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/33961781","citation_count":705,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"14718574","id":"PMC_14718574","title":"The human plasma proteome: a nonredundant list developed by combination of four separate sources.","date":"2004","source":"Molecular & cellular proteomics : MCP","url":"https://pubmed.ncbi.nlm.nih.gov/14718574","citation_count":658,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"21873635","id":"PMC_21873635","title":"Phylogenetic-based propagation of functional annotations within the Gene Ontology consortium.","date":"2011","source":"Briefings in bioinformatics","url":"https://pubmed.ncbi.nlm.nih.gov/21873635","citation_count":656,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"3052293","id":"PMC_3052293","title":"Cofactor proteins in the assembly and expression of blood clotting enzyme complexes.","date":"1988","source":"Annual review of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/3052293","citation_count":534,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"18248600","id":"PMC_18248600","title":"Pregnancy, the postpartum period and prothrombotic defects: risk of venous thrombosis in the MEGA study.","date":"2008","source":"Journal of thrombosis and haemostasis : JTH","url":"https://pubmed.ncbi.nlm.nih.gov/18248600","citation_count":427,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"7911873","id":"PMC_7911873","title":"Linkage between inherited resistance to activated protein C and factor V gene mutation in venous thrombosis.","date":"1994","source":"Lancet (London, England)","url":"https://pubmed.ncbi.nlm.nih.gov/7911873","citation_count":419,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"16344560","id":"PMC_16344560","title":"Diversification of transcriptional modulation: large-scale identification and characterization of putative alternative promoters of human genes.","date":"2005","source":"Genome research","url":"https://pubmed.ncbi.nlm.nih.gov/16344560","citation_count":409,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"3110773","id":"PMC_3110773","title":"Complete cDNA and derived amino acid sequence of human factor V.","date":"1987","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/3110773","citation_count":398,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"20351233","id":"PMC_20351233","title":"Risk assessment of recurrence in patients with unprovoked deep vein thrombosis or pulmonary embolism: the Vienna prediction model.","date":"2010","source":"Circulation","url":"https://pubmed.ncbi.nlm.nih.gov/20351233","citation_count":389,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"12524220","id":"PMC_12524220","title":"The dynamics of thrombin formation.","date":"2003","source":"Arteriosclerosis, thrombosis, and vascular biology","url":"https://pubmed.ncbi.nlm.nih.gov/12524220","citation_count":387,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"16335952","id":"PMC_16335952","title":"Human plasma N-glycoproteome analysis by immunoaffinity subtraction, hydrazide chemistry, and mass spectrometry.","date":"2005","source":"Journal of proteome research","url":"https://pubmed.ncbi.nlm.nih.gov/16335952","citation_count":350,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"7989361","id":"PMC_7989361","title":"The mechanism of inactivation of human factor V and human factor Va by activated protein C.","date":"1994","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/7989361","citation_count":347,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"19783216","id":"PMC_19783216","title":"Antiphospholipid antibodies and risk of myocardial infarction and ischaemic stroke in young women in the RATIO study: a case-control study.","date":"2009","source":"The Lancet. Neurology","url":"https://pubmed.ncbi.nlm.nih.gov/19783216","citation_count":315,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"15534175","id":"PMC_15534175","title":"Meta-analysis of genetic studies in ischemic stroke: thirty-two genes involving approximately 18,000 cases and 58,000 controls.","date":"2004","source":"Archives of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/15534175","citation_count":313,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"11583312","id":"PMC_11583312","title":"Combined effect of factor V Leiden and prothrombin 20210A on the risk of venous thromboembolism--pooled analysis of 8 case-control studies including 2310 cases and 3204 controls. Study Group for Pooled-Analysis in Venous Thromboembolism.","date":"2001","source":"Thrombosis and haemostasis","url":"https://pubmed.ncbi.nlm.nih.gov/11583312","citation_count":261,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"11018168","id":"PMC_11018168","title":"Mutations in coagulation factors in women with unexplained late fetal loss.","date":"2000","source":"The New England journal of medicine","url":"https://pubmed.ncbi.nlm.nih.gov/11018168","citation_count":250,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"19278955","id":"PMC_19278955","title":"Common susceptibility alleles are unlikely to contribute as strongly as the FV and ABO loci to VTE risk: results from a GWAS approach.","date":"2009","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/19278955","citation_count":245,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"7076681","id":"PMC_7076681","title":"Thrombin-catalyzed activation of human coagulation factor V.","date":"1982","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/7076681","citation_count":244,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"9454742","id":"PMC_9454742","title":"Factor V Cambridge: a new mutation (Arg306-->Thr) associated with resistance to activated protein C.","date":"1998","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/9454742","citation_count":239,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"12717434","id":"PMC_12717434","title":"Bleeding due to disruption of a cargo-specific ER-to-Golgi transport complex.","date":"2003","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/12717434","citation_count":234,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"11022077","id":"PMC_11022077","title":"Symptomatic ischemic stroke in full-term neonates : role of acquired and genetic prothrombotic risk factors.","date":"2000","source":"Stroke","url":"https://pubmed.ncbi.nlm.nih.gov/11022077","citation_count":224,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"24769233","id":"PMC_24769233","title":"Proteomic analysis of cerebrospinal fluid extracellular vesicles: a comprehensive dataset.","date":"2014","source":"Journal of proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/24769233","citation_count":218,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"17897305","id":"PMC_17897305","title":"Risk of venous thrombosis: obesity and its joint effect with oral contraceptive use and prothrombotic mutations.","date":"2007","source":"British journal of haematology","url":"https://pubmed.ncbi.nlm.nih.gov/17897305","citation_count":217,"is_preprint":false,"source_track":"gene2pubmed"}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":46189,"output_tokens":1,"usd":0.069291},"stage2":{"model":"","input_tokens":0,"output_tokens":0,"usd":0.0},"total_usd":0.401825,"stage1_batch_id":"msgbatch_0118RScg3WGaGkaZRtWZbtce","stage2_batch_id":"msgbatch_01Cpfzvtbj42aqp5oYZ5Te2s","note":"batch pricing = 50% of standard","round2_stage1":{"model":"claude-sonnet-4-6","input_tokens":60489,"output_tokens":6653,"usd":0.140631},"round2_rules_fired":"R1","round2_stage2":{"model":"claude-opus-4-6","input_tokens":9667,"output_tokens":3184,"usd":0.191903}},"stage1_raw":"\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\nI'll systematically classify each paper before extracting discoveries.\n\n**Classification:**\n\nThe target gene is **F5** = human coagulation **Factor V** (blood coagulation protein).\n\n**KEEP papers** (about coagulation Factor V / F5):\n- Retrieved: [5], [14], [19], [25], [28], [31], [35], [36], [41], [42], [46], [55], [66], [68], [73], [83], [91]\n- Gene2pubmed: [1], [6], [11], [13], [15], [19], [25], [26], [27]\n\n**EXCLUDE papers:**\n- Antibody Fv fragment papers (immunoglobulin Fv, scFv, dsFv engineering): [1],[2],[3],[4],[6],[7],[8],[9],[10],[11],[12 (retrieved)],[15],[16],[17],[20],[21],[22],[24],[26],[27],[29],[32],[33],[37],[38],[44],[45],[47],[48],[49],[50],[54],[57],[60],[61],[67],[69],[72],[74],[75],[79],[82],[87],[89],[90],[93],[94],[95],[97] — all Fv antibody fragment papers (alias collision: \"Fv\" = antibody fragment variable region, not Factor V)\n- Mouse retrovirus restriction genes Fv-1, Fv-2, Fv-4: [13],[23],[39],[52],[58],[59],[70],[76] — alias collision (murine leukemia virus restriction loci)\n- Macaque premotor cortex area F5 (neuroscience): [12],[84] — alias collision\n- Botulinum toxin BoNT/F5: [40],[80],[100] — alias collision\n- Rice f5 locus: [63] — symbol collision (plant gene)\n- Tomato SlERF.F5: [64] — symbol collision (plant gene)\n- Flammulina velutipes Fv-1: [96] — symbol collision (fungal gene)\n- E. coli F5/K99 fimbriae: [56],[78] — symbol collision (bacterial adhesin)\n- FV-3 (frog virus 3): [30] — alias collision\n- Protein Fv (hepatitis-associated protein activating basophils): [34] — different protein\n- F5-phenylalanine (pentafluorophenylalanine): [16] — alias collision\n- F-5 fragment of HSP90α: [62] — alias collision\n- FV-429 (flavonoid derivative drug): [51] — alias collision\n- Mouse chromosome 7 F4/F5 bands: [85] — cytogenetic band nomenclature, not the gene\n- Gene2pubmed [2],[3],[4],[5],[7],[8],[9],[10],[14] — general genomics/proteomics databases not specific to F5 mechanism\n- Gene2pubmed [12],[16],[20],[21],[22],[23],[24],[28],[29],[30] — epidemiological/clinical studies without mechanistic content on F5 protein\n\n**KEEP and extract from:**\n\nRetrieved: [5],[14],[19],[25],[28],[31],[35],[36],[41],[42],[46],[55],[66],[68],[73],[83],[91]\nGene2pubmed: [1],[6],[11],[13],[15],[19=g2p19],[25=g2p25],[26],[27]\n\nNow extracting mechanistic discoveries:\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1987,\n      \"finding\": \"Complete cDNA cloning of human Factor V revealed a 2224-amino-acid single-chain protein with a domain structure A1-A2-B-A3-C1-C2 (triplicated A domains homologous to Factor VIII and ceruloplasmin, duplicated C domains, and a large B domain containing 35+ tandem 9-amino-acid repeats with 37 potential N-linked glycosylation sites, 25 in the B domain).\",\n      \"method\": \"cDNA cloning and sequence analysis of human fetal liver library; direct amino acid sequence comparison with Factor VIII and ceruloplasmin\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — foundational full-length cDNA sequencing establishing primary structure; highly cited and replicated\",\n      \"pmids\": [\"3110773\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1982,\n      \"finding\": \"Thrombin activates single-chain Factor V (Mr ~330,000) by limited proteolysis, generating Factor Va with 25–30-fold higher cofactor activity. Activation produces fragments D (105 kDa) and F1F2 (71–74 kDa doublet) held by noncovalent interactions, plus two activation peptides (E and C1); reconstitution of D and F1F2 restores cofactor activity, establishing that these two fragments constitute the biologically active cofactor.\",\n      \"method\": \"Purification of human Factor V; SDS-PAGE analysis of thrombin cleavage products; reconstitution experiments with isolated fragments; NH2-terminal sequencing\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with purified components plus fragment characterization; highly cited foundational study\",\n      \"pmids\": [\"7076681\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1988,\n      \"finding\": \"Factor Va functions as an essential nonenzymatic cofactor in the prothrombinase complex (Factor Xa + Factor Va on phospholipid membranes) and in the intrinsic Xase complex, dramatically accelerating thrombin generation; Factor V is activated by thrombin and inactivated by activated protein C (APC), which cleaves cofactors Va and VIIIa to limit clot formation.\",\n      \"method\": \"Biochemical reconstitution of coagulation enzyme complexes; kinetic analysis; review synthesizing multiple experimental studies\",\n      \"journal\": \"Annual review of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted enzyme complex activity, synthesizing multiple experimental findings; highly cited\",\n      \"pmids\": [\"3052293\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1989,\n      \"finding\": \"Activated protein C (APC), formed on the endothelial cell surface when thrombin binds thrombomodulin, proteolytically inactivates Factor Va by cleavage, with protein S serving as a nonenzymatic APC cofactor; intact Factor V also serves as an APC cofactor in the inactivation pathway.\",\n      \"method\": \"Biochemical characterization of protein C activation on endothelial surfaces; proteolysis assays of Factor Va inactivation; identification of protein S cofactor requirement\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution of APC pathway; highly cited foundational study\",\n      \"pmids\": [\"2538457\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"APC inactivates Factor Va by sequential proteolytic cleavages at Arg506, Arg306, and Arg679 on the heavy chain; cleavage at Arg506 precedes and is required for cleavage at Arg306 and Arg679; inactivation (>90% loss of cofactor activity) only occurs efficiently in the presence of phospholipid membranes (phosphatidylserine/phosphatidylcholine vesicles); in the absence of membrane, Factor Va retains ~80% activity even after APC cleavage at Arg506.\",\n      \"method\": \"In vitro APC cleavage assays of purified human Factor V and Factor Va; SDS-PAGE fragment identification; cofactor activity assays with and without phospholipid vesicles\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — rigorous in vitro reconstitution with purified proteins, multiple cleavage sites mapped, membrane dependence demonstrated; highly cited\",\n      \"pmids\": [\"7989361\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"The phenotype of APC resistance is caused by a single point mutation in the Factor V gene (G→A at nucleotide 1691, predicting Arg506Gln substitution), producing FV Leiden (FV Q506), which is activated normally by thrombin or Factor Xa but is impaired in inactivation by APC; the allelic frequency is ~2% in the Dutch population.\",\n      \"method\": \"Family linkage study; DNA sequencing of Factor V gene; functional assays of APC resistance in plasma\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — mutation identified by sequencing linked to functional APC resistance phenotype; landmark paper with >3500 citations\",\n      \"pmids\": [\"8164741\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Linkage analysis in a family with thrombophilia showed 100% cosegregation of Factor V gene polymorphisms with APC resistance, and identified the Arg506Gln point mutation in the APC cleavage site as the cause; purified Factor V expressed an anticoagulant activity that corrected APC resistance in plasma, establishing Factor V as an APC cofactor.\",\n      \"method\": \"RFLP linkage analysis in familial thrombophilia kindred; Factor V gene sequencing; purified Factor V cofactor activity assay\",\n      \"journal\": \"Lancet\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — genetic linkage plus functional correction with purified protein; highly cited\",\n      \"pmids\": [\"7911873\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"A second APC cleavage site mutation in Factor V, Arg306→Thr (Factor V Cambridge), causes APC resistance and thrombosis, confirming the physiological importance of the Arg306 APC cleavage site in regulation of the prothrombinase complex.\",\n      \"method\": \"Sequencing of Factor V gene in patients with APC resistance lacking FV Leiden; clinical phenotyping; exclusion of other APC resistance causes\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic identification with functional phenotype (APC resistance); single-lab study\",\n      \"pmids\": [\"9454742\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"The R2 haplotype of the Factor V gene (containing the 4070G variant) is associated with an altered ratio of two functionally distinct FV plasma isoforms: carriers of the Ala2194Gly variant (C2 domain) show a relative increase of the more thrombogenic, more glycosylated FV isoform (FV1) versus FV2, suggesting that differential glycosylation (determined by C2 domain sequence) modulates FV isoform distribution and thrombotic risk.\",\n      \"method\": \"Molecular genetics (sequencing of R2 homozygotes); chromatographic separation of FV1 and FV2 isoforms; biochemical characterization in plasma\",\n      \"journal\": \"Thrombosis and haemostasis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — biochemical separation of isoforms with genetic correlation; single-lab study\",\n      \"pmids\": [\"10744138\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Recombinant Factor V Cambridge (Arg306Thr) and FV Hong Kong (Arg306Gly) both produce intermediate APC resistance patterns (between wild-type and FV Leiden). In the absence of protein S, APC causes only partial inactivation of these FVa variants. In the presence of protein S, both variants are nearly completely inactivated through stimulation of cleavage at Arg679. Both variants show slightly impaired APC cofactor activity in FVIIIa degradation assays.\",\n      \"method\": \"Recombinant expression of FV variants; APC inactivation kinetics assays with and without protein S; FVIIIa degradation assays\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro system with recombinant proteins; multiple functional assays; explains clinical phenotype\",\n      \"pmids\": [\"12091344\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"MCFD2 (an EF-hand domain protein) mutations cause combined Factor V and Factor VIII deficiency (F5F8D) with a phenotype indistinguishable from LMAN1 mutations. MCFD2 is localized to the ERGIC through a direct, calcium-dependent interaction with LMAN1, and the MCFD2-LMAN1 complex forms a specific cargo receptor for ER-to-Golgi transport of Factor V and Factor VIII.\",\n      \"method\": \"Mutation screening of F5F8D patients; subcellular localization by immunofluorescence; Co-IP demonstrating MCFD2-LMAN1 calcium-dependent interaction; genetic analysis\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — direct protein interaction demonstrated, subcellular localization established, human genetics validated; highly cited\",\n      \"pmids\": [\"12717434\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Coinheritance of FV Leiden in a patient with severe FVII deficiency (FVII Lazio) increases thrombin generation, particularly in the presence of APC, explaining a milder bleeding phenotype. Experiments with purified FV or FV Leiden reconstituted into doubly-deficient plasma confirmed that FV Leiden generates more FXa and thrombin than normal FV due to APC resistance of FVa Leiden.\",\n      \"method\": \"Thrombin generation assays in patient plasma; FXa and FVa generation assays; reconstitution with purified normal FV vs. FV Leiden in doubly-deficient plasma\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — purified protein reconstitution with functional readout; demonstrates FV Leiden APC resistance mechanism in prothrombinase context\",\n      \"pmids\": [\"12881304\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Combined FV and FVIII deficiency (F5F8D) is caused by mutations in LMAN1 or MCFD2, which encode a calcium-dependent heteromeric cargo receptor complex that cycles between the ER and ERGIC. Missense mutations in MCFD2 EF-hand domains abolish interaction with LMAN1. MCFD2 mutations generally cause lower FV and FVIII levels than LMAN1 mutations. The LMAN1-MCFD2 complex acts as a cargo receptor for ER-to-Golgi transport of both FV and FVIII.\",\n      \"method\": \"Review synthesizing genetic and biochemical studies; EF-hand domain mutation analysis; LMAN1-MCFD2 interaction studies\",\n      \"journal\": \"British journal of haematology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — synthesis of multiple experimental studies establishing cargo receptor mechanism; supported by genetic and biochemical data\",\n      \"pmids\": [\"19183188\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"LMAN1-deficient (Lman1−/−) mice exhibit ~50% reduction in plasma FV, plasma FVIII, and platelet FV levels, confirming LMAN1 as a cargo receptor required for efficient ER-to-Golgi transport of FV. The reduction is less severe than in human F5F8D patients (5–30%), suggesting partial redundancy or strain-dependent effects. ER in Lman1−/− hepatocytes is slightly distended with accumulation of α1-antitrypsin and GRP78.\",\n      \"method\": \"Lman1 knockout mouse model; plasma FV and FVIII level measurement; platelet FV measurement; electron microscopy of hepatocytes; in vitro COPII vesicle formation assay\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — genetic knockout with direct measurement of FV secretion; multiple orthogonal methods\",\n      \"pmids\": [\"21795745\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"A homozygous deep-intronic F5 mutation (IVS8 +268A→G) causes inclusion of a pseudo-exon with an in-frame stop codon in F5 mRNA, resulting in severe FV deficiency with undetectable FV activity in plasma and platelets. This patient showed no thrombin generation in platelet-rich plasma triggered with 1–50 pM tissue factor, demonstrating that platelet FV is essential for thrombin generation support in PRP.\",\n      \"method\": \"F5 gene sequencing; RT-PCR/cDNA analysis of aberrant splicing; prothrombinase-based FV activity assay; thrombin generation in PRP; Western blotting for FV antigen in platelets\",\n      \"journal\": \"Journal of thrombosis and haemostasis\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — molecular characterization of splicing defect with functional consequences; first deep-intronic F5 mutation described\",\n      \"pmids\": [\"21320286\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Crystal structures of the LMAN1 carbohydrate recognition domain (CRD) bound to Man-α-1,2-Man (terminal moiety of high-mannose glycans) reveal the central mannose-binding site; mutagenesis identifies His178 and Gly251/252 as critical for FV/FVIII cargo binding. Mannobiose binding is relatively pH-independent in the ER-to-Golgi range but sensitive to lowered Ca2+ concentrations, suggesting that compartmental Ca2+ changes regulate glycoprotein cargo binding and release from the LMAN1·MCFD2 complex.\",\n      \"method\": \"X-ray crystallography of LMAN1-CRD with mannobiose; site-directed mutagenesis; in vitro carbohydrate binding assays; Ca2+ titration experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure plus mutagenesis plus in vitro binding assays; defines molecular basis of FV/FVIII cargo recognition\",\n      \"pmids\": [\"23709226\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"An apparently synonymous F5 variant (c.1281C>G in exon 8) activates a cryptic donor splice site and abolishes an exonic splicing enhancer, causing half of the patient's F5 mRNA to lack the last 18 nucleotides of exon 8. The aberrantly spliced mRNA encodes a putative FV protein lacking amino acids 427–432 that is poorly secreted and nonfunctional when expressed in COS-1 cells. A mutation-specific morpholino antisense oligonucleotide partially corrects the splicing defect.\",\n      \"method\": \"F5 gene sequencing; RT-PCR/cDNA analysis; F5 minigene assay; bioinformatics splice site prediction; COS-1 cell expression of mutant protein; morpholino antisense oligonucleotide correction\",\n      \"journal\": \"Haemophilia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — minigene functional validation, cell expression, antisense correction; multiple orthogonal methods\",\n      \"pmids\": [\"25470420\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A novel FV missense mutation Ala2086Asp (FV Besançon) in the C2 domain favors a 'closed conformation' predicting impaired phospholipid binding, causes markedly decreased FV secretion, and paradoxically induces a hypercoagulable/thrombotic state in an FV-deficient patient. Recombinant FVa Besançon shows slightly unfavorable kinetics of prothrombin activation (Km, Vmax) but a lower rate of APC-catalyzed inactivation in the presence of protein S, abolishing FV APC-cofactor activity.\",\n      \"method\": \"Patient clinical characterization; F5 gene sequencing; recombinant FV Besançon expression; thrombin generation assays in platelet-poor and platelet-rich plasma; APC resistance testing; prothrombinase kinetics with diluted plasma reconstituted with recombinant FVa; TFPI antigen/activity measurement\",\n      \"journal\": \"Journal of thrombosis and haemostasis\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — recombinant protein functional characterization with kinetic assays; multiple mechanistic readouts; explains paradoxical thrombosis in FV-deficient patient\",\n      \"pmids\": [\"33605529\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A novel heterozygous 832-bp deletion within F5 exon 13 (F5-Atlanta) enhances alternative splicing at East Texas (ET) splice sites within exon 13, producing a FV-Short isoform with a truncated B domain. This alternatively spliced transcript markedly elevates circulating total and free TFPIα levels. The findings establish that cis-acting regulatory sequences within F5 exon 13 control alternative splicing at ET splice sites and thereby regulate circulating FV-Short and TFPIα levels.\",\n      \"method\": \"Patient plasma analysis (TFPI levels, FV isoform sizing); F5 cDNA sequencing; heterologous expression in mammalian cells to recapitulate alternative splicing\",\n      \"journal\": \"Journal of thrombosis and haemostasis\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — mechanistic model validated by recombinant expression; patient plasma data corroborated; identifies cis-regulatory elements in F5 exon 13\",\n      \"pmids\": [\"33773040\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"FV-Short, a naturally occurring splice isoform of Factor V with a truncated B domain, binds TFPIα with high affinity. Together with protein S, FV-Short forms a high-affinity trimolecular complex (FV-Short/protein S/TFPIα) that synergistically stimulates the FXa-inhibitory activity of TFPIα, functioning as a natural anticoagulant threshold mechanism. In the East Texas bleeding disorder, this complex is elevated ~10-fold, explaining the bleeding phenotype.\",\n      \"method\": \"Synthesis of experimental findings on FV-Short discovery; binding affinity measurements; functional TFPIα inhibition assays; patient plasma characterization\",\n      \"journal\": \"Journal of thrombosis and haemostasis\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — synthesis of binding studies and functional assays establishing anticoagulant mechanism of FV-Short; replicated across multiple studies\",\n      \"pmids\": [\"36746318\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Three F5 gene mutations were identified in two Chinese pedigrees with inherited FV deficiency: (i) homozygous IVS8 -2A>G (splicing mutation) that abolishes the canonical splice acceptor site and activates a cryptic acceptor 24 bp upstream, inserting 8 extra amino acids into FV; (ii) heterozygous 2238-9del AG (frameshift, exon 13, introducing premature stop at AA 689); and (iii) heterozygous G6410T (exon 23, missense Gly2079Val).\",\n      \"method\": \"PCR amplification and sequencing of all 25 F5 exons; RT-PCR/cDNA analysis of aberrant mRNA from patient lymphocytes\",\n      \"journal\": \"Haemophilia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — molecular characterization of splicing mechanism by cDNA analysis; functional consequence (FV deficiency) established by clinical phenotype\",\n      \"pmids\": [\"15086325\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Coagulation Factor V (F5) is a large plasma glycoprotein (A1-A2-B-A3-C1-C2 domain structure) that circulates as a procofactor and, upon thrombin-mediated activation (cleavage generating heavy and light chains held noncovalently), becomes Factor Va — a critical nonenzymatic cofactor of the prothrombinase complex (Factor Xa/Factor Va/phospholipid/Ca²⁺) that dramatically accelerates thrombin generation; Factor Va is inactivated by APC through sequential phospholipid-dependent cleavages at Arg506, Arg306, and Arg679 (with protein S as cofactor), and the common FV Leiden mutation (Arg506Gln) impairs this inactivation causing thrombophilia; Factor V is also secreted by an LMAN1-MCFD2 calcium-dependent cargo receptor complex in the ER-to-Golgi pathway, and a naturally occurring splice isoform (FV-Short) with a truncated B domain forms a high-affinity trimolecular complex with TFPIα and protein S that provides an anticoagulant threshold by synergistically stimulating FXa inhibition.\"\n}\n```","stage2_raw":"\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"Coagulation factor V is a large plasma glycoprotein (A1-A2-B-A3-C1-C2 domain architecture) that circulates as an inactive procofactor and, upon thrombin-mediated proteolysis generating noncovalently associated heavy and light chains, becomes Factor Va — the essential nonenzymatic cofactor of the prothrombinase complex (Factor Xa/Factor Va/phospholipid/Ca²⁺) that dramatically accelerates prothrombin conversion to thrombin [PMID:7076681, PMID:3052293]. Factor Va is inactivated by activated protein C (APC) through sequential phospholipid-dependent cleavages at Arg506, Arg306, and Arg679, with protein S as cofactor; the FV Leiden mutation (Arg506Gln) impairs this inactivation and is the most common inherited cause of thrombophilia [PMID:7989361, PMID:8164741]. Efficient ER-to-Golgi secretion of Factor V requires the LMAN1–MCFD2 calcium-dependent cargo receptor complex, and biallelic loss-of-function mutations in LMAN1 or MCFD2 cause combined Factor V and Factor VIII deficiency [PMID:12717434, PMID:21795745]. A naturally occurring splice isoform, FV-Short, forms a high-affinity trimolecular complex with TFPIα and protein S that synergistically inhibits Factor Xa, establishing an anticoagulant threshold whose dysregulation underlies the East Texas bleeding disorder [PMID:36746318, PMID:33773040].\",\n  \"teleology\": [\n    {\n      \"year\": 1982,\n      \"claim\": \"Establishing how Factor V is converted to its active cofactor form resolved the long-standing question of how a single-chain procofactor gains catalytic relevance: thrombin generates a heavy chain (D fragment) and light chain (F1F2 doublet) whose noncovalent association reconstitutes cofactor activity.\",\n      \"evidence\": \"Purification of human FV; SDS-PAGE of thrombin cleavage products; reconstitution of cofactor activity from isolated fragments\",\n      \"pmids\": [\"7076681\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise thrombin cleavage sites on the procofactor were not mapped at single-residue resolution\", \"Contribution of individual domains to prothrombinase assembly was not defined\"]\n    },\n    {\n      \"year\": 1987,\n      \"claim\": \"Determination of the complete primary structure of Factor V revealed its A1-A2-B-A3-C1-C2 domain architecture and homology to Factor VIII and ceruloplasmin, providing the structural framework for interpreting all subsequent mutagenesis and disease-mutation studies.\",\n      \"evidence\": \"Full-length cDNA cloning from human fetal liver library with sequence analysis\",\n      \"pmids\": [\"3110773\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No three-dimensional structure was available\", \"Function of the large, heavily glycosylated B domain remained unclear\"]\n    },\n    {\n      \"year\": 1988,\n      \"claim\": \"Reconstitution of the prothrombinase and intrinsic Xase complexes demonstrated that Factor Va is the critical nonenzymatic cofactor that dramatically accelerates thrombin generation, and that APC limits coagulation by proteolytically inactivating both Factor Va and Factor VIIIa.\",\n      \"evidence\": \"Biochemical reconstitution of coagulation enzyme complexes with kinetic analysis\",\n      \"pmids\": [\"3052293\", \"2538457\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"APC cleavage sites on FVa were not yet mapped\", \"The role of protein S as APC cofactor was not molecularly defined\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Mapping APC cleavage sites at Arg506, Arg306, and Arg679 — and the near-simultaneous discovery that the Arg506Gln (FV Leiden) mutation causes APC resistance and familial thrombophilia — established the molecular basis of the predominant inherited thrombotic risk factor and the obligate sequential inactivation pathway of Factor Va.\",\n      \"evidence\": \"In vitro APC cleavage assays with purified FVa and phospholipid vesicles; family linkage study and DNA sequencing in thrombophilia kindreds; APC resistance assays\",\n      \"pmids\": [\"7989361\", \"8164741\", \"7911873\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of APC–FVa interaction was not resolved\", \"Whether protein S specifically redirects APC cleavage hierarchy was not yet shown\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Identification of a second APC-site mutation (Arg306Thr, FV Cambridge) in a thrombophilic patient confirmed that Arg306 is a physiologically important APC cleavage site independent of Arg506.\",\n      \"evidence\": \"F5 gene sequencing in APC-resistant patients lacking FV Leiden; clinical phenotyping\",\n      \"pmids\": [\"9454742\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Only a single kindred was described\", \"Relative contribution of Arg306 versus Arg506 cleavage to overall FVa inactivation was not quantified\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Recombinant expression of FV Cambridge and FV Hong Kong variants demonstrated that Arg306 mutations produce intermediate APC resistance and that protein S rescues near-complete inactivation by stimulating cleavage at Arg679, quantifying the protein S contribution to the alternative inactivation pathway.\",\n      \"evidence\": \"Recombinant FV variant expression; APC inactivation kinetics ± protein S; FVIIIa degradation assays\",\n      \"pmids\": [\"12091344\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of protein S stimulation of Arg679 cleavage was unknown\", \"In vivo relevance of the Arg679 cleavage site was not tested\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Discovery that MCFD2 and LMAN1 form a calcium-dependent cargo receptor complex required for ER-to-Golgi transport of both Factor V and Factor VIII explained the molecular basis of combined F5F8 deficiency and identified the secretory pathway mechanism for FV.\",\n      \"evidence\": \"Mutation screening of F5F8D patients; co-immunoprecipitation of MCFD2–LMAN1; subcellular localization by immunofluorescence\",\n      \"pmids\": [\"12717434\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct binding of LMAN1–MCFD2 to FV cargo had not been reconstituted\", \"Whether the complex recognizes FV glycans or polypeptide determinants was unresolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"LMAN1 knockout mice confirmed in vivo that LMAN1 is required for efficient FV (and FVIII) secretion, though the ~50% reduction was milder than in human F5F8D patients, suggesting partial redundancy or species differences in the secretory pathway.\",\n      \"evidence\": \"Lman1−/− mouse model; plasma FV/FVIII and platelet FV measurement; electron microscopy of hepatocyte ER\",\n      \"pmids\": [\"21795745\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of any redundant ER-to-Golgi cargo receptor for FV was unknown\", \"Platelet-specific FV trafficking mechanism was not defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Crystal structures of the LMAN1 carbohydrate recognition domain bound to mannobiose defined how LMAN1 recognizes high-mannose glycans on FV/FVIII cargo, and mutagenesis identified critical residues (His178, Gly251/252); Ca²⁺-dependent binding suggested compartmental Ca²⁺ gradients regulate cargo release.\",\n      \"evidence\": \"X-ray crystallography of LMAN1-CRD with mannobiose; site-directed mutagenesis; Ca²⁺ titration binding assays\",\n      \"pmids\": [\"23709226\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structure of the full LMAN1–MCFD2–FV ternary complex\", \"Which specific glycan sites on FV are recognized was not determined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Discovery of FV-Short as a naturally occurring splice isoform and identification of cis-regulatory elements in F5 exon 13 that control alternative splicing at East Texas splice sites established a previously unrecognized regulatory layer linking F5 mRNA processing to circulating TFPIα levels and anticoagulant capacity.\",\n      \"evidence\": \"Patient plasma analysis; F5 cDNA sequencing of the F5-Atlanta deletion; heterologous expression recapitulating alternative splicing\",\n      \"pmids\": [\"33773040\", \"33605529\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trans-acting splicing regulators controlling FV-Short production were not identified\", \"Quantitative contribution of FV-Short to normal hemostatic balance in healthy individuals was not established\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstration that FV-Short, protein S, and TFPIα form a high-affinity trimolecular complex that synergistically inhibits Factor Xa revealed a dual procoagulant/anticoagulant role for Factor V and explained the bleeding phenotype of the East Texas disorder.\",\n      \"evidence\": \"Binding affinity measurements; functional TFPIα inhibition assays; patient plasma characterization\",\n      \"pmids\": [\"36746318\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the FV-Short/protein S/TFPIα complex is unresolved\", \"Whether therapeutic modulation of FV-Short splicing can rebalance hemostasis is untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Major open questions include the three-dimensional structure of intact Factor Va in the prothrombinase complex, the identity of trans-acting regulators of FV-Short alternative splicing, and the structural determinants that allow Factor V to switch between procoagulant cofactor (in prothrombinase) and anticoagulant cofactor (for APC and as FV-Short/TFPIα complex) roles.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No high-resolution structure of FVa within the prothrombinase complex\", \"Trans-acting regulators of FV-Short splicing unknown\", \"Molecular basis of FV dual procoagulant/anticoagulant switching unresolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [2, 3, 4, 6, 19]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [4, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [1, 2, 5, 14, 19]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [10, 12, 13, 15]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [10, 12]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-109582\", \"supporting_discovery_ids\": [1, 2, 3, 4, 5, 6, 9, 11, 17, 19]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [10, 12, 13, 15]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [5, 6, 7, 14]}\n    ],\n    \"complexes\": [\n      \"Prothrombinase complex (FXa/FVa/phospholipid/Ca²⁺)\",\n      \"FV-Short/TFPIα/protein S anticoagulant complex\"\n    ],\n    \"partners\": [\n      \"F10\",\n      \"PROC\",\n      \"PROS1\",\n      \"TFPI\",\n      \"LMAN1\",\n      \"MCFD2\",\n      \"F2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}