{"gene":"CFD","run_date":"2026-06-14T21:02:38+00:00","timeline":{"discoveries":[{"year":1989,"finding":"Recombinant mouse adipsin (CFD ortholog) was shown to cleave complement factor B when complexed with activated C3, demonstrating the same enzymatic activity as human complement factor D and enabling activation of the alternative pathway of complement, resulting in red blood cell lysis.","method":"In vitro enzymatic assay with recombinant protein; hemolytic assay","journal":"Science","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro reconstitution of enzymatic activity with recombinant protein, hemolytic assay, replicated across multiple animal models","pmids":["2734615"],"is_preprint":false},{"year":1994,"finding":"Human CFD is synthesized as an inactive zymogen (profactor D) with an N-terminal activation peptide (AAPPRGR or APPRGR); catalytic amounts of trypsin convert recombinant profactor D to enzymatically active factor D. Human thrombin, kallikrein, and plasmin can also activate profactor D but with lower efficiency (~1/3 specific hemolytic activity). Native profactor D was also isolated from urine of a patient with Fanconi's syndrome.","method":"Baculovirus expression of recombinant profactor D; amino acid sequencing; trypsin/protease activation assays; SDS-PAGE; hemolytic activity assays","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with recombinant protein, mutagenesis-level sequencing of activation peptide, multiple orthogonal methods in one study","pmids":["8144940"],"is_preprint":false},{"year":1996,"finding":"CFD is a unique serine protease that does not require enzymatic cleavage for proteolytic activity nor serpin inactivation for control. Instead, regulation is achieved through reversible conformational changes induced by its single natural substrate C3bB, realigning the catalytic triad, specificity pocket, and substrate binding site — all of which have atypical conformations in the resting state. Mutational studies defined structural determinants responsible for low reactivity with synthetic esters.","method":"Structural and mutational analysis; esterolytic and hemolytic assays with site-directed mutants","journal":"Protein science","confidence":"High","confidence_rationale":"Tier 1 / Moderate — active-site mutagenesis combined with enzymatic assays and structural characterization in a dedicated mechanistic review synthesizing prior experimental work","pmids":["8845746"],"is_preprint":false},{"year":1988,"finding":"CFD is filtered through the glomerulus and catabolized by renal tubular cells under normal circumstances, with the kidney being the primary site of CFD catabolism; the fractional metabolic rate correlates with creatinine clearance. Renal failure causes ~10-fold accumulation of factor D in plasma due to drastically reduced catabolism, not increased synthesis.","method":"Injection of purified radiolabelled factor D into humans; compartmental pharmacokinetic modeling; creatinine clearance correlation","journal":"Kidney international","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct radiolabelling metabolic study in humans with rigorous compartmental modeling across multiple patient groups","pmids":["3199673"],"is_preprint":false},{"year":1993,"finding":"CFD is adsorbed by polyacrylonitrile (PAN) dialysis membranes in a dose- and time-dependent manner; CFD is catalytically inactive while adsorbed to PAN fibers but recovers full hemolytic function upon elution. PAN removes ~95% of CFD from serum passed through a dialyzer, reducing alternative pathway activation.","method":"In vitro incubation of serum/purified radiolabeled CFD with PAN fibers; hemolytic assay of adsorbed vs. eluted CFD; immunoblotting","journal":"Kidney international","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding and functional assays with purified protein and serum, single lab, two orthogonal methods","pmids":["8479128"],"is_preprint":false},{"year":2016,"finding":"CFD (adipsin) promotes adipocyte differentiation and lipid accumulation via a C3a/C3aR signaling axis: CFD overexpression increases C3a production and induces C3aR target gene expression; C3aR knockdown suppresses adipogenesis and abolishes the pro-adipogenic effect of CFD overexpression. shRNA-mediated CFD knockdown inhibits lipid accumulation and adipocyte marker expression.","method":"shRNA knockdown; overexpression; C3a/C3aR agonist treatment; qPCR; lipid staining in preadipocyte differentiation assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function and gain-of-function with defined cellular phenotype, epistasis via C3aR knockdown, single lab","pmids":["27611793"],"is_preprint":false},{"year":2004,"finding":"Genetic deficiency of CFD in MRL/lpr lupus-prone mice prevents glomerular C3 deposition and reduces proliferative renal disease and elevated serum creatinine, establishing CFD-dependent alternative pathway activation as the proximate cause of complement-mediated kidney damage in this model.","method":"Genetic knockout (CFD-deficient mice backcrossed onto MRL/lpr); zymosan AP activation assay; ELISA; histology; electron microscopy; immunofluorescence for C3/IgG","journal":"Kidney international","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic KO with multiple orthogonal phenotypic readouts and functional complement assay, confirms AP specificity","pmids":["14675043"],"is_preprint":false},{"year":2007,"finding":"CFD-deficient mice show significantly protected photoreceptors from light-induced degeneration, establishing that the alternative complement pathway activity (dependent on CFD) mediates rod photoreceptor death in oxidative stress-induced retinal damage.","method":"CFD knockout mice on BALB/c background; constant light exposure; electroretinography; histology","journal":"Investigative ophthalmology & visual science","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic KO with electrophysiological and histological phenotypic readouts, directly ties CFD to complement-mediated photoreceptor loss","pmids":["17962484"],"is_preprint":false},{"year":2018,"finding":"CFD-deficient mice fed ethanol show paradoxically increased liver injury, steatosis, and proinflammatory cytokines compared to wild-type, with accumulation of apoptotic cells and profibrotic responses, demonstrating that CFD-dependent alternative pathway amplification plays a protective, adaptive role in clearing apoptotic cells during alcoholic liver disease.","method":"CFD-deficient mice (FD-/-), C1qa-/-, C4-/-, and C1qa/FD-/- genetic models; chronic/short-term ethanol feeding; hepatic C3 cleavage product detection; apoptotic cell detection; cytokine measurement","journal":"American journal of physiology. Gastrointestinal and liver physiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple genetic KO models with mechanistic pathway dissection, multiple orthogonal readouts, single lab","pmids":["29597356"],"is_preprint":false},{"year":2022,"finding":"The right ventricle predominantly expresses CFD and C3aR1; CFD knockout mice show attenuated right ventricular dysfunction and fibrosis in a model of right ventricular failure. C3a is produced from C3 via the C3 convertase containing CFD; C3aR antagonism improves right ventricular dysfunction, establishing a C3-CFD-C3aR signaling axis in right ventricular remodeling.","method":"CFD-knockout mice; C3-knockout mice; C3aR antagonist treatment; cardiac function assessment; gene expression analysis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple genetic KO models with pharmacological validation, multiple readouts, establishes pathway order","pmids":["36109509"],"is_preprint":false},{"year":2023,"finding":"CFD is produced and secreted by glomerular endothelial cells; CFD knockdown in conditionally immortalized human glomerular endothelial cells reduces local complement activation and attenuates Ang II-induced upregulation of ICAM-1, VCAM-1, von Willebrand factor, and endothelin-1, demonstrating that endothelial-derived CFD drives local complement activation and endothelial dysfunction.","method":"siRNA knockdown in CiGEnCs; immunofluorescence microscopy; mass spectrometry; ELISA; gene expression","journal":"Hypertension research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA loss-of-function with defined molecular phenotype, single lab, two orthogonal methods","pmids":["37188751"],"is_preprint":false},{"year":2023,"finding":"The pro-zymogen form of CFD (pro-FD) is continuously converted to active mature CFD by circulating MASP-3. Active CFD has ~20 million-fold enhanced cleavage of FB when FB is complexed with C3b (C3bB) compared to free FB. Pro-CFD retains ~1/800th the activity of mature CFD toward C3bB and at ~50-fold physiological FD concentration can restore half-maximal AP activity in FD-depleted serum.","method":"In vitro enzymatic assay; MASP-1 and MASP-3 catalytic fragment activity assays; site-directed mutagenesis (Arg25Gln to stabilize proenzyme); FD-depleted serum reconstitution; quantitative kinetics","journal":"Frontiers in immunology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with mutagenesis-stabilized zymogen, quantitative kinetics, multiple enzyme comparisons, functional serum rescue assay","pmids":["37283768"],"is_preprint":false},{"year":2022,"finding":"CFD production by cutaneous squamous cell carcinoma (cSCC) cells is dependent on p38 MAPK activity and is induced by IFN-γ and IL-1β; blocking CFD activity with danicopan inhibits ERK1/2 activation and attenuates cSCC cell proliferation.","method":"RT-qPCR; Western blot; danicopan pharmacological inhibition; kinase inhibitor (p38 inhibitor); cytokine stimulation; cell proliferation assay","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological inhibition with defined signaling readout, upstream regulation by p38/cytokines established, single lab","pmids":["35053469"],"is_preprint":false},{"year":2022,"finding":"CFD derived from epicardial adipose tissue mediates cardiomyocyte apoptosis after myocardial infarction by inducing PARP-1 overactivation; CFD inhibitor (CFD-IN1) reverses cardiomyocyte apoptosis both in vitro and in vivo in a rat MI model. The apoptosis is caspase-independent (pan-caspase inhibitor Z-VAD did not prevent it).","method":"Rat MI model (LAD ligation); H9c2 cell culture; conditioned medium from EAT; CFD-IN1 inhibitor; PARP-1 inhibitor (3-Aminobenzamide); pan-caspase inhibitor Z-VAD; cell viability assays","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological inhibition with defined molecular mechanism (PARP-1), in vitro and in vivo corroboration, single lab","pmids":["36351508"],"is_preprint":false},{"year":2023,"finding":"In Graves' orbitopathy orbital fibroblasts, adipsin/CFD is induced by IGF-1 and CD40L stimulation; exogenous recombinant adipsin activates Akt, ERK, p38, and JNK signaling pathways. siRNA silencing of adipsin suppresses IGF-1-induced IL-6, IL-8, COX2, ICAM-1, CCL2 gene expression and IL-6 protein secretion, and attenuates adipocyte differentiation.","method":"siRNA knockdown; recombinant adipsin treatment; Western blot (Akt, ERK, p38, JNK phosphorylation); ELISA; qPCR; Oil Red O staining","journal":"Investigative ophthalmology & visual science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function and gain-of-function with defined signaling readout, multiple downstream targets, single lab","pmids":["37555734"],"is_preprint":false},{"year":2023,"finding":"HNF1α inhibits CFD expression in hepatocytes; a dominant-negative P291fsinsC HNF1α mutant reverses this inhibition, upregulating CFD. siRNA or pharmacological inhibition of CFD reduced triglyceride levels in hepatocytes, demonstrating that CFD regulates hepatocyte lipid deposition downstream of HNF1α.","method":"Mouse model carrying HNF1α P291fsinsC mutation; transcriptomics; proteomics; siRNA knockdown of CFD in hepatocytes; pharmacological inhibitor; triglyceride measurement","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis (HNF1α→CFD), functional loss-of-function with lipid phenotype, single lab with multiple orthogonal methods","pmids":["37841581"],"is_preprint":false},{"year":2021,"finding":"Reconstitution of CFD-deficient serum with factor D dose- and time-dependently restores alternative pathway activity and complement C3 deposition on bacterial surfaces (Neisseria meningitidis, Streptococcus pneumoniae, non-typeable Haemophilus influenzae), and restores complement-mediated bacterial killing, establishing CFD as the rate-limiting enzyme for AP-mediated bactericidal activity.","method":"FD-deficient patient serum reconstitution; AP hemolytic activity assay; C3 deposition on bacteria by flow cytometry; bacterial killing assay","journal":"Clinical & translational immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reconstitution of patient-deficient serum with purified factor D, multiple orthogonal readouts, single lab","pmids":["33841879"],"is_preprint":false},{"year":2025,"finding":"In a MAFLD mouse model, CRISPR knockout of CFD attenuates hepatocyte lipid deposition; danicopan (CFD pharmacological inhibitor) reduces intracellular triglycerides/cholesterol, improves glucose tolerance, and alleviates hepatic steatosis. Mechanistically, danicopan suppresses NF-κB signaling and inhibits lipid-related genes (CD36/FASN/FATP2) and inflammatory mediators (MMP12/IL-6/TNF-α).","method":"CRISPR knockout; pharmacological inhibition (danicopan); HFD mouse model; hepatocyte culture; NF-κB signaling assays; gene expression; lipid measurements","journal":"Molecular immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR KO with pharmacological corroboration, defined NF-κB signaling mechanism, single lab","pmids":["41308544"],"is_preprint":false},{"year":2023,"finding":"A long-acting, pH-sensitive anti-CFD monoclonal antibody mitigated aberrant complement alternative pathway activation driven by CFD amplification in SARS-CoV-2 infection, protected endothelial cells from damage, and curtailed innate immune response in human vascular organoid and macaque COVID-19 models.","method":"Human vascular organoid infection model; macaque COVID-19 model; anti-CFD monoclonal antibody treatment; intravital imaging; serum proteomics","journal":"Cell stem cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological CFD targeting with defined endothelial phenotype in two orthogonal models (organoid + primate), single lab","pmids":["37802037"],"is_preprint":false},{"year":2021,"finding":"In CFD-deficient mice subjected to cecal ligation and puncture sepsis, platelets show reduced GPIIb/IIIa surface expression compared to wild-type septic mice, linking CFD to platelet activation during sepsis.","method":"CFD-deficient mice; cecal ligation and puncture model; flow cytometry for GPIIb/IIIa; coagulation markers","journal":"Intensive care medicine experimental","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single genetic model, single flow cytometry readout, indirect mechanistic link, single lab","pmids":["34396466"],"is_preprint":false}],"current_model":"Complement Factor D (CFD/adipsin) is a serine protease that exists in circulation predominantly in its active form, converted from its pro-zymogen (pro-FD) by MASP-3; it functions as the rate-limiting enzyme of the alternative complement pathway by cleaving factor B only when factor B is complexed with C3b (C3bB) — an interaction that induces conformational realignment of CFD's catalytic triad and specificity pocket, enhancing cleavage activity ~20 million-fold over free factor B — thereby generating the AP C3 convertase C3bBb; beyond complement activation, CFD drives adipogenesis via C3a/C3aR signaling, regulates hepatocyte lipid metabolism through NF-κB, promotes cardiomyocyte apoptosis via PARP-1, and contributes to endothelial dysfunction through local complement activation, while being catabolized primarily by renal tubular cells."},"narrative":{"mechanistic_narrative":"Complement Factor D (CFD/adipsin) is the rate-limiting serine protease of the alternative complement pathway, whose single physiological substrate is factor B presented within the C3bB complex [PMID:2734615, PMID:8845746]. CFD is unusual among serine proteases in that it does not require proteolytic cleavage of itself or serpin inactivation for control; instead its catalytic triad, specificity pocket, and substrate-binding site adopt atypical resting conformations that are realigned only upon binding C3bB, conferring substrate-induced activity [PMID:8845746]. Mature CFD cleaves factor B ~20 million-fold more efficiently when factor B is complexed with C3b than as free factor B, generating the C3 convertase that drives the pathway [PMID:37283768]. CFD itself is synthesized as a zymogen (profactor D) bearing an N-terminal activation peptide; in circulation it is continuously matured by MASP-3, while trypsin and other proteases can perform this conversion in vitro [PMID:8144940, PMID:37283768]. Serum reconstitution experiments establish CFD as the rate-limiting enzyme for alternative-pathway hemolysis, C3 deposition on bacteria, and complement-mediated bacterial killing [PMID:2734615, PMID:33841879]. CFD is filtered through the glomerulus and catabolized primarily by renal tubular cells, so renal failure causes marked plasma accumulation [PMID:3199673]. Genetic ablation studies extend its role beyond serum complement: CFD-dependent alternative-pathway activation drives complement-mediated tissue injury in lupus nephritis and light-induced photoreceptor degeneration, yet plays a protective, adaptive role in clearing apoptotic cells during alcoholic liver disease [PMID:14675043, PMID:17962484, PMID:29597356]. Beyond complement, CFD/adipsin promotes adipocyte differentiation and lipid accumulation through a C3a/C3aR signaling axis, an axis also operative in right-ventricular remodeling [PMID:27611793, PMID:36109509], and contributes to hepatocyte lipid metabolism, cardiomyocyte apoptosis, and endothelial dysfunction as documented across multiple tissue models [PMID:37841581, PMID:36351508, PMID:37188751].","teleology":[{"year":1989,"claim":"Established that adipsin/CFD is enzymatically a complement factor D, resolving whether the adipocyte-derived protein had complement protease activity.","evidence":"In vitro enzymatic and hemolytic assays with recombinant mouse adipsin cleaving factor B in complex with activated C3","pmids":["2734615"],"confidence":"High","gaps":["Did not resolve how CFD distinguishes free factor B from C3b-bound factor B","No structural basis for substrate specificity"]},{"year":1988,"claim":"Defined the route of CFD turnover, explaining why circulating CFD accumulates in renal disease.","evidence":"Radiolabelled factor D injection into humans with compartmental pharmacokinetic modeling and creatinine clearance correlation","pmids":["3199673"],"confidence":"High","gaps":["Molecular mechanism of tubular uptake/degradation not defined","Does not address consequences of accumulation for AP activity"]},{"year":1994,"claim":"Showed CFD is made as a zymogen requiring activation-peptide removal, framing the question of its physiological activator.","evidence":"Baculovirus-expressed profactor D, amino acid sequencing, and trypsin/protease activation with hemolytic readout","pmids":["8144940"],"confidence":"High","gaps":["Did not identify the physiological in vivo activating protease","Relative contribution of thrombin/kallikrein/plasmin in vivo unknown"]},{"year":1996,"claim":"Explained how CFD activity is regulated without zymogen cleavage or serpins, identifying substrate-induced conformational realignment as the control mechanism.","evidence":"Structural and active-site mutational analysis with esterolytic and hemolytic assays","pmids":["8845746"],"confidence":"High","gaps":["Atomic dynamics of the resting-to-active transition not fully resolved","Quantitative link between conformational change and cleavage rate not yet measured"]},{"year":1993,"claim":"Demonstrated that CFD activity can be physically modulated by adsorption, providing a route to dampen alternative-pathway activation.","evidence":"In vitro incubation of serum/purified CFD with polyacrylonitrile fibers, hemolytic and immunoblot readouts","pmids":["8479128"],"confidence":"Medium","gaps":["Single lab, in vitro only","Clinical relevance of adsorptive removal not established here"]},{"year":2004,"claim":"Established CFD-dependent alternative-pathway activation as the proximate driver of complement-mediated kidney injury in autoimmune disease.","evidence":"CFD-deficient MRL/lpr mice with histology, immunofluorescence for C3/IgG, and functional AP assay","pmids":["14675043"],"confidence":"High","gaps":["Does not address non-complement functions of CFD","Human translatability not tested"]},{"year":2007,"claim":"Extended CFD's pathogenic role to oxidative retinal injury, linking AP activity to photoreceptor death.","evidence":"CFD-knockout mice with light-exposure model, electroretinography, and histology","pmids":["17962484"],"confidence":"High","gaps":["Cellular source of CFD in the retina not defined","Downstream effector of photoreceptor death not identified"]},{"year":2016,"claim":"Identified a non-complement, pro-adipogenic role for CFD acting through C3a/C3aR signaling.","evidence":"shRNA knockdown, overexpression, and C3aR-knockdown epistasis in preadipocyte differentiation with lipid staining and qPCR","pmids":["27611793"],"confidence":"Medium","gaps":["Single lab, cell-based","Whether C3a is generated by canonical AP convertase in this context not directly shown"]},{"year":2018,"claim":"Revealed that CFD-dependent AP amplification can be protective, clearing apoptotic cells in alcoholic liver disease rather than only causing injury.","evidence":"Multiple complement-pathway genetic KO models with ethanol feeding, C3 cleavage detection, apoptosis and cytokine readouts","pmids":["29597356"],"confidence":"High","gaps":["Mechanism of apoptotic-cell recognition by AP not defined","Tissue/context determinants of protective vs pathogenic AP not resolved"]},{"year":2021,"claim":"Quantitatively confirmed CFD as the rate-limiting enzyme for AP bactericidal activity through serum reconstitution.","evidence":"FD-deficient patient serum reconstituted with factor D; AP hemolysis, C3 deposition on bacteria by flow cytometry, and killing assays","pmids":["33841879"],"confidence":"Medium","gaps":["Single lab","Restricted to the bacterial species tested"]},{"year":2021,"claim":"Linked CFD to platelet activation during sepsis, hinting at a coagulation interface.","evidence":"CFD-deficient mice in cecal ligation and puncture with flow cytometry for platelet GPIIb/IIIa","pmids":["34396466"],"confidence":"Low","gaps":["Single genetic model with a single flow cytometry readout; indirect mechanistic link","No direct molecular pathway connecting CFD to platelet activation"]},{"year":2022,"claim":"Defined a C3-CFD-C3aR signaling axis in right-ventricular remodeling, ordering the pathway in cardiac pathology.","evidence":"CFD- and C3-knockout mice plus C3aR antagonist with cardiac function and gene-expression readouts","pmids":["36109509"],"confidence":"High","gaps":["Cellular target of C3aR signaling in RV not pinpointed","Whether CFD acts locally vs systemically not resolved"]},{"year":2022,"claim":"Identified upstream regulation of CFD by p38/cytokine signaling and a pro-proliferative role in squamous cell carcinoma.","evidence":"RT-qPCR, Western blot, danicopan inhibition, and p38 inhibitor in cSCC cells with proliferation readout","pmids":["35053469"],"confidence":"Medium","gaps":["Single lab","Whether the effect requires complement convertase activity vs another mechanism unclear"]},{"year":2022,"claim":"Defined a caspase-independent, PARP-1-mediated mechanism by which CFD drives cardiomyocyte apoptosis after infarction.","evidence":"Rat MI model, conditioned medium from epicardial adipose tissue, CFD and PARP-1 inhibitors, pan-caspase inhibitor controls","pmids":["36351508"],"confidence":"Medium","gaps":["Single lab","Receptor linking secreted CFD to PARP-1 activation not identified"]},{"year":2023,"claim":"Showed glomerular endothelial cells produce CFD that drives local complement activation and endothelial dysfunction.","evidence":"siRNA knockdown in conditionally immortalized human glomerular endothelial cells with Ang II stimulation, IF, mass spec, ELISA","pmids":["37188751"],"confidence":"Medium","gaps":["Single lab","Relative contribution of local vs circulating CFD in vivo not established"]},{"year":2023,"claim":"Resolved the physiological activator of profactor D, identifying MASP-3 as the continuous maturase and quantifying zymogen residual activity.","evidence":"In vitro kinetics with MASP-1/MASP-3 fragments, Arg25Gln-stabilized proenzyme, and FD-depleted serum reconstitution","pmids":["37283768"],"confidence":"High","gaps":["Regulation of MASP-3 availability in vivo not addressed","Whether pro-FD contributes meaningfully to AP under physiological conditions unresolved"]},{"year":2023,"claim":"Placed CFD as a transcriptional target of HNF1α controlling hepatocyte lipid deposition.","evidence":"HNF1α P291fsinsC mutant mouse, transcriptomics/proteomics, CFD siRNA and inhibitor with triglyceride measurement","pmids":["37841581"],"confidence":"Medium","gaps":["Single lab","Whether lipid effect depends on complement convertase activity not separated"]},{"year":2023,"claim":"Defined adipsin/CFD as an autocrine amplifier of inflammatory and adipogenic signaling in Graves' orbitopathy fibroblasts.","evidence":"siRNA silencing and recombinant adipsin treatment with Akt/ERK/p38/JNK phosphorylation, qPCR, ELISA, and Oil Red O staining","pmids":["37555734"],"confidence":"Medium","gaps":["Receptor mediating adipsin-induced kinase activation not identified","Single lab"]},{"year":2023,"claim":"Demonstrated therapeutic CFD blockade mitigates aberrant AP amplification and protects endothelium in viral infection.","evidence":"Long-acting pH-sensitive anti-CFD antibody in human vascular organoid and macaque COVID-19 models with imaging and proteomics","pmids":["37802037"],"confidence":"Medium","gaps":["Single lab","Mechanism of endothelial protection beyond reduced AP activation not detailed"]},{"year":2025,"claim":"Linked CFD to hepatic steatosis via NF-κB signaling, connecting complement protease activity to metabolic and inflammatory gene programs.","evidence":"CRISPR CFD knockout and danicopan inhibition in a MAFLD mouse model with NF-κB assays, lipid and gene-expression readouts","pmids":["41308544"],"confidence":"Medium","gaps":["Single lab","Whether NF-κB activation is downstream of C3a/C3aR or convertase-independent not resolved"]},{"year":null,"claim":"How CFD's catalytic complement activity is mechanistically partitioned from its diverse C3a/C3aR-dependent and convertase-independent tissue signaling roles remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model distinguishing convertase-dependent vs independent CFD effects across tissues","Direct receptors mediating non-complement CFD signaling not identified","In vivo source (local vs circulating) of CFD in each pathology not systematically resolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,2,11,16]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,1,11]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[3,10,11]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,6,7,8,16]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[5,15,17]}],"complexes":[],"partners":["CFB","C3","MASP3","C3AR1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P00746","full_name":"Complement factor D","aliases":["Adipsin","C3 convertase activator","Properdin factor D"],"length_aa":253,"mass_kda":27.0,"function":"Serine protease that initiates 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:21205667, PubMed:22362762, PubMed:6769474, PubMed:874324, PubMed:9748277). In contrast to other complement pathways (classical, lectin and GZMK) that are directly activated by pathogens or antigen-antibody complexes, the alternative complement pathway is initiated by the spontaneous hydrolysis of complement C3 (PubMed:21205667, PubMed:22362762, PubMed:6769474, PubMed:874324). The alternative complement pathway acts as an amplification loop that enhances complement activation by mediating the formation of C3 and C5 convertases (PubMed:21205667, PubMed:22362762, PubMed:6769474, PubMed:874324). Activated CFD cleaves factor B (CFB) when the latter is complexed with complement C3b, activating the C3 convertase of the alternative pathway (PubMed:21205667, PubMed:6769474, PubMed:874324, PubMed:9748277)","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/P00746/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CFD","classification":"Not Classified","n_dependent_lines":9,"n_total_lines":1208,"dependency_fraction":0.0074503311258278145},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CFD","total_profiled":1310},"omim":[{"mim_id":"621351","title":"SERINE PROTEASE 57; PRSS57","url":"https://www.omim.org/entry/621351"},{"mim_id":"613912","title":"COMPLEMENT FACTOR D DEFICIENCY; CFDD","url":"https://www.omim.org/entry/613912"},{"mim_id":"610379","title":"WEST NILE VIRUS, SUSCEPTIBILITY TO","url":"https://www.omim.org/entry/610379"},{"mim_id":"609414","title":"PHOSPHOINOSITIDE KINASE, FYVE FINGER-CONTAINING; PIKFYVE","url":"https://www.omim.org/entry/609414"},{"mim_id":"138470","title":"COMPLEMENT FACTOR B; CFB","url":"https://www.omim.org/entry/138470"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"adipose tissue","ntpm":1421.6}],"url":"https://www.proteinatlas.org/search/CFD"},"hgnc":{"alias_symbol":["ADN"],"prev_symbol":["DF","PFD"]},"alphafold":{"accession":"P00746","domains":[{"cath_id":"2.40.10.10","chopping":"41-133_247-253","consensus_level":"medium","plddt":97.2674,"start":41,"end":253},{"cath_id":"2.40.10.10","chopping":"134-243","consensus_level":"medium","plddt":94.3892,"start":134,"end":243}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P00746","model_url":"https://alphafold.ebi.ac.uk/files/AF-P00746-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P00746-F1-predicted_aligned_error_v6.png","plddt_mean":91.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CFD","jax_strain_url":"https://www.jax.org/strain/search?query=CFD"},"sequence":{"accession":"P00746","fasta_url":"https://rest.uniprot.org/uniprotkb/P00746.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P00746/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P00746"}},"corpus_meta":[{"pmid":"2734615","id":"PMC_2734615","title":"Adipsin and complement factor D activity: an immune-related defect in obesity.","date":"1989","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/2734615","citation_count":246,"is_preprint":false},{"pmid":"8845746","id":"PMC_8845746","title":"Complement factor D, a novel serine protease.","date":"1996","source":"Protein science : a publication of the Protein Society","url":"https://pubmed.ncbi.nlm.nih.gov/8845746","citation_count":127,"is_preprint":false},{"pmid":"3199673","id":"PMC_3199673","title":"Metabolism of complement factor D in renal failure.","date":"1988","source":"Kidney international","url":"https://pubmed.ncbi.nlm.nih.gov/3199673","citation_count":109,"is_preprint":false},{"pmid":"34566967","id":"PMC_34566967","title":"Complement Factor D as a Strategic Target for Regulating the Alternative Complement Pathway.","date":"2021","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/34566967","citation_count":106,"is_preprint":false},{"pmid":"33121236","id":"PMC_33121236","title":"Danicopan: an oral complement factor D inhibitor for paroxysmal nocturnal hemoglobinuria.","date":"2021","source":"Haematologica","url":"https://pubmed.ncbi.nlm.nih.gov/33121236","citation_count":91,"is_preprint":false},{"pmid":"14675043","id":"PMC_14675043","title":"Effects of complement factor D deficiency on the renal disease of MRL/lpr mice.","date":"2004","source":"Kidney international","url":"https://pubmed.ncbi.nlm.nih.gov/14675043","citation_count":87,"is_preprint":false},{"pmid":"27611793","id":"PMC_27611793","title":"Small Molecule-Induced Complement Factor D (Adipsin) Promotes Lipid Accumulation and Adipocyte Differentiation.","date":"2016","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/27611793","citation_count":85,"is_preprint":false},{"pmid":"22003108","id":"PMC_22003108","title":"Complement factor D in age-related macular degeneration.","date":"2011","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/22003108","citation_count":81,"is_preprint":false},{"pmid":"17962484","id":"PMC_17962484","title":"Eliminating complement factor D reduces photoreceptor susceptibility to light-induced damage.","date":"2007","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/17962484","citation_count":78,"is_preprint":false},{"pmid":"8479128","id":"PMC_8479128","title":"Adsorption of complement factor D by polyacrylonitrile dialysis membranes.","date":"1993","source":"Kidney international","url":"https://pubmed.ncbi.nlm.nih.gov/8479128","citation_count":61,"is_preprint":false},{"pmid":"31573880","id":"PMC_31573880","title":"Discovery and Development of the Oral Complement Factor D Inhibitor Danicopan (ACH-4471).","date":"2020","source":"Current medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/31573880","citation_count":42,"is_preprint":false},{"pmid":"29597356","id":"PMC_29597356","title":"Complement Factor D protects mice from ethanol-induced inflammation and liver injury.","date":"2018","source":"American journal of physiology. 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complexed with activated C3, demonstrating the same enzymatic activity as human complement factor D and enabling activation of the alternative pathway of complement, resulting in red blood cell lysis.\",\n      \"method\": \"In vitro enzymatic assay with recombinant protein; hemolytic assay\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro reconstitution of enzymatic activity with recombinant protein, hemolytic assay, replicated across multiple animal models\",\n      \"pmids\": [\"2734615\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Human CFD is synthesized as an inactive zymogen (profactor D) with an N-terminal activation peptide (AAPPRGR or APPRGR); catalytic amounts of trypsin convert recombinant profactor D to enzymatically active factor D. Human thrombin, kallikrein, and plasmin can also activate profactor D but with lower efficiency (~1/3 specific hemolytic activity). Native profactor D was also isolated from urine of a patient with Fanconi's syndrome.\",\n      \"method\": \"Baculovirus expression of recombinant profactor D; amino acid sequencing; trypsin/protease activation assays; SDS-PAGE; hemolytic activity assays\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with recombinant protein, mutagenesis-level sequencing of activation peptide, multiple orthogonal methods in one study\",\n      \"pmids\": [\"8144940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"CFD is a unique serine protease that does not require enzymatic cleavage for proteolytic activity nor serpin inactivation for control. Instead, regulation is achieved through reversible conformational changes induced by its single natural substrate C3bB, realigning the catalytic triad, specificity pocket, and substrate binding site — all of which have atypical conformations in the resting state. Mutational studies defined structural determinants responsible for low reactivity with synthetic esters.\",\n      \"method\": \"Structural and mutational analysis; esterolytic and hemolytic assays with site-directed mutants\",\n      \"journal\": \"Protein science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — active-site mutagenesis combined with enzymatic assays and structural characterization in a dedicated mechanistic review synthesizing prior experimental work\",\n      \"pmids\": [\"8845746\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1988,\n      \"finding\": \"CFD is filtered through the glomerulus and catabolized by renal tubular cells under normal circumstances, with the kidney being the primary site of CFD catabolism; the fractional metabolic rate correlates with creatinine clearance. Renal failure causes ~10-fold accumulation of factor D in plasma due to drastically reduced catabolism, not increased synthesis.\",\n      \"method\": \"Injection of purified radiolabelled factor D into humans; compartmental pharmacokinetic modeling; creatinine clearance correlation\",\n      \"journal\": \"Kidney international\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct radiolabelling metabolic study in humans with rigorous compartmental modeling across multiple patient groups\",\n      \"pmids\": [\"3199673\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"CFD is adsorbed by polyacrylonitrile (PAN) dialysis membranes in a dose- and time-dependent manner; CFD is catalytically inactive while adsorbed to PAN fibers but recovers full hemolytic function upon elution. PAN removes ~95% of CFD from serum passed through a dialyzer, reducing alternative pathway activation.\",\n      \"method\": \"In vitro incubation of serum/purified radiolabeled CFD with PAN fibers; hemolytic assay of adsorbed vs. eluted CFD; immunoblotting\",\n      \"journal\": \"Kidney international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding and functional assays with purified protein and serum, single lab, two orthogonal methods\",\n      \"pmids\": [\"8479128\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"CFD (adipsin) promotes adipocyte differentiation and lipid accumulation via a C3a/C3aR signaling axis: CFD overexpression increases C3a production and induces C3aR target gene expression; C3aR knockdown suppresses adipogenesis and abolishes the pro-adipogenic effect of CFD overexpression. shRNA-mediated CFD knockdown inhibits lipid accumulation and adipocyte marker expression.\",\n      \"method\": \"shRNA knockdown; overexpression; C3a/C3aR agonist treatment; qPCR; lipid staining in preadipocyte differentiation assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function and gain-of-function with defined cellular phenotype, epistasis via C3aR knockdown, single lab\",\n      \"pmids\": [\"27611793\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Genetic deficiency of CFD in MRL/lpr lupus-prone mice prevents glomerular C3 deposition and reduces proliferative renal disease and elevated serum creatinine, establishing CFD-dependent alternative pathway activation as the proximate cause of complement-mediated kidney damage in this model.\",\n      \"method\": \"Genetic knockout (CFD-deficient mice backcrossed onto MRL/lpr); zymosan AP activation assay; ELISA; histology; electron microscopy; immunofluorescence for C3/IgG\",\n      \"journal\": \"Kidney international\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic KO with multiple orthogonal phenotypic readouts and functional complement assay, confirms AP specificity\",\n      \"pmids\": [\"14675043\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"CFD-deficient mice show significantly protected photoreceptors from light-induced degeneration, establishing that the alternative complement pathway activity (dependent on CFD) mediates rod photoreceptor death in oxidative stress-induced retinal damage.\",\n      \"method\": \"CFD knockout mice on BALB/c background; constant light exposure; electroretinography; histology\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic KO with electrophysiological and histological phenotypic readouts, directly ties CFD to complement-mediated photoreceptor loss\",\n      \"pmids\": [\"17962484\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CFD-deficient mice fed ethanol show paradoxically increased liver injury, steatosis, and proinflammatory cytokines compared to wild-type, with accumulation of apoptotic cells and profibrotic responses, demonstrating that CFD-dependent alternative pathway amplification plays a protective, adaptive role in clearing apoptotic cells during alcoholic liver disease.\",\n      \"method\": \"CFD-deficient mice (FD-/-), C1qa-/-, C4-/-, and C1qa/FD-/- genetic models; chronic/short-term ethanol feeding; hepatic C3 cleavage product detection; apoptotic cell detection; cytokine measurement\",\n      \"journal\": \"American journal of physiology. Gastrointestinal and liver physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple genetic KO models with mechanistic pathway dissection, multiple orthogonal readouts, single lab\",\n      \"pmids\": [\"29597356\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The right ventricle predominantly expresses CFD and C3aR1; CFD knockout mice show attenuated right ventricular dysfunction and fibrosis in a model of right ventricular failure. C3a is produced from C3 via the C3 convertase containing CFD; C3aR antagonism improves right ventricular dysfunction, establishing a C3-CFD-C3aR signaling axis in right ventricular remodeling.\",\n      \"method\": \"CFD-knockout mice; C3-knockout mice; C3aR antagonist treatment; cardiac function assessment; gene expression analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple genetic KO models with pharmacological validation, multiple readouts, establishes pathway order\",\n      \"pmids\": [\"36109509\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CFD is produced and secreted by glomerular endothelial cells; CFD knockdown in conditionally immortalized human glomerular endothelial cells reduces local complement activation and attenuates Ang II-induced upregulation of ICAM-1, VCAM-1, von Willebrand factor, and endothelin-1, demonstrating that endothelial-derived CFD drives local complement activation and endothelial dysfunction.\",\n      \"method\": \"siRNA knockdown in CiGEnCs; immunofluorescence microscopy; mass spectrometry; ELISA; gene expression\",\n      \"journal\": \"Hypertension research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA loss-of-function with defined molecular phenotype, single lab, two orthogonal methods\",\n      \"pmids\": [\"37188751\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The pro-zymogen form of CFD (pro-FD) is continuously converted to active mature CFD by circulating MASP-3. Active CFD has ~20 million-fold enhanced cleavage of FB when FB is complexed with C3b (C3bB) compared to free FB. Pro-CFD retains ~1/800th the activity of mature CFD toward C3bB and at ~50-fold physiological FD concentration can restore half-maximal AP activity in FD-depleted serum.\",\n      \"method\": \"In vitro enzymatic assay; MASP-1 and MASP-3 catalytic fragment activity assays; site-directed mutagenesis (Arg25Gln to stabilize proenzyme); FD-depleted serum reconstitution; quantitative kinetics\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with mutagenesis-stabilized zymogen, quantitative kinetics, multiple enzyme comparisons, functional serum rescue assay\",\n      \"pmids\": [\"37283768\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CFD production by cutaneous squamous cell carcinoma (cSCC) cells is dependent on p38 MAPK activity and is induced by IFN-γ and IL-1β; blocking CFD activity with danicopan inhibits ERK1/2 activation and attenuates cSCC cell proliferation.\",\n      \"method\": \"RT-qPCR; Western blot; danicopan pharmacological inhibition; kinase inhibitor (p38 inhibitor); cytokine stimulation; cell proliferation assay\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological inhibition with defined signaling readout, upstream regulation by p38/cytokines established, single lab\",\n      \"pmids\": [\"35053469\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CFD derived from epicardial adipose tissue mediates cardiomyocyte apoptosis after myocardial infarction by inducing PARP-1 overactivation; CFD inhibitor (CFD-IN1) reverses cardiomyocyte apoptosis both in vitro and in vivo in a rat MI model. The apoptosis is caspase-independent (pan-caspase inhibitor Z-VAD did not prevent it).\",\n      \"method\": \"Rat MI model (LAD ligation); H9c2 cell culture; conditioned medium from EAT; CFD-IN1 inhibitor; PARP-1 inhibitor (3-Aminobenzamide); pan-caspase inhibitor Z-VAD; cell viability assays\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological inhibition with defined molecular mechanism (PARP-1), in vitro and in vivo corroboration, single lab\",\n      \"pmids\": [\"36351508\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"In Graves' orbitopathy orbital fibroblasts, adipsin/CFD is induced by IGF-1 and CD40L stimulation; exogenous recombinant adipsin activates Akt, ERK, p38, and JNK signaling pathways. siRNA silencing of adipsin suppresses IGF-1-induced IL-6, IL-8, COX2, ICAM-1, CCL2 gene expression and IL-6 protein secretion, and attenuates adipocyte differentiation.\",\n      \"method\": \"siRNA knockdown; recombinant adipsin treatment; Western blot (Akt, ERK, p38, JNK phosphorylation); ELISA; qPCR; Oil Red O staining\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function and gain-of-function with defined signaling readout, multiple downstream targets, single lab\",\n      \"pmids\": [\"37555734\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"HNF1α inhibits CFD expression in hepatocytes; a dominant-negative P291fsinsC HNF1α mutant reverses this inhibition, upregulating CFD. siRNA or pharmacological inhibition of CFD reduced triglyceride levels in hepatocytes, demonstrating that CFD regulates hepatocyte lipid deposition downstream of HNF1α.\",\n      \"method\": \"Mouse model carrying HNF1α P291fsinsC mutation; transcriptomics; proteomics; siRNA knockdown of CFD in hepatocytes; pharmacological inhibitor; triglyceride measurement\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis (HNF1α→CFD), functional loss-of-function with lipid phenotype, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"37841581\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Reconstitution of CFD-deficient serum with factor D dose- and time-dependently restores alternative pathway activity and complement C3 deposition on bacterial surfaces (Neisseria meningitidis, Streptococcus pneumoniae, non-typeable Haemophilus influenzae), and restores complement-mediated bacterial killing, establishing CFD as the rate-limiting enzyme for AP-mediated bactericidal activity.\",\n      \"method\": \"FD-deficient patient serum reconstitution; AP hemolytic activity assay; C3 deposition on bacteria by flow cytometry; bacterial killing assay\",\n      \"journal\": \"Clinical & translational immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reconstitution of patient-deficient serum with purified factor D, multiple orthogonal readouts, single lab\",\n      \"pmids\": [\"33841879\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In a MAFLD mouse model, CRISPR knockout of CFD attenuates hepatocyte lipid deposition; danicopan (CFD pharmacological inhibitor) reduces intracellular triglycerides/cholesterol, improves glucose tolerance, and alleviates hepatic steatosis. Mechanistically, danicopan suppresses NF-κB signaling and inhibits lipid-related genes (CD36/FASN/FATP2) and inflammatory mediators (MMP12/IL-6/TNF-α).\",\n      \"method\": \"CRISPR knockout; pharmacological inhibition (danicopan); HFD mouse model; hepatocyte culture; NF-κB signaling assays; gene expression; lipid measurements\",\n      \"journal\": \"Molecular immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR KO with pharmacological corroboration, defined NF-κB signaling mechanism, single lab\",\n      \"pmids\": [\"41308544\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"A long-acting, pH-sensitive anti-CFD monoclonal antibody mitigated aberrant complement alternative pathway activation driven by CFD amplification in SARS-CoV-2 infection, protected endothelial cells from damage, and curtailed innate immune response in human vascular organoid and macaque COVID-19 models.\",\n      \"method\": \"Human vascular organoid infection model; macaque COVID-19 model; anti-CFD monoclonal antibody treatment; intravital imaging; serum proteomics\",\n      \"journal\": \"Cell stem cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological CFD targeting with defined endothelial phenotype in two orthogonal models (organoid + primate), single lab\",\n      \"pmids\": [\"37802037\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In CFD-deficient mice subjected to cecal ligation and puncture sepsis, platelets show reduced GPIIb/IIIa surface expression compared to wild-type septic mice, linking CFD to platelet activation during sepsis.\",\n      \"method\": \"CFD-deficient mice; cecal ligation and puncture model; flow cytometry for GPIIb/IIIa; coagulation markers\",\n      \"journal\": \"Intensive care medicine experimental\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single genetic model, single flow cytometry readout, indirect mechanistic link, single lab\",\n      \"pmids\": [\"34396466\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Complement Factor D (CFD/adipsin) is a serine protease that exists in circulation predominantly in its active form, converted from its pro-zymogen (pro-FD) by MASP-3; it functions as the rate-limiting enzyme of the alternative complement pathway by cleaving factor B only when factor B is complexed with C3b (C3bB) — an interaction that induces conformational realignment of CFD's catalytic triad and specificity pocket, enhancing cleavage activity ~20 million-fold over free factor B — thereby generating the AP C3 convertase C3bBb; beyond complement activation, CFD drives adipogenesis via C3a/C3aR signaling, regulates hepatocyte lipid metabolism through NF-κB, promotes cardiomyocyte apoptosis via PARP-1, and contributes to endothelial dysfunction through local complement activation, while being catabolized primarily by renal tubular cells.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"Complement Factor D (CFD/adipsin) is the rate-limiting serine protease of the alternative complement pathway, whose single physiological substrate is factor B presented within the C3bB complex [#0, #2]. CFD is unusual among serine proteases in that it does not require proteolytic cleavage of itself or serpin inactivation for control; instead its catalytic triad, specificity pocket, and substrate-binding site adopt atypical resting conformations that are realigned only upon binding C3bB, conferring substrate-induced activity [#2]. Mature CFD cleaves factor B ~20 million-fold more efficiently when factor B is complexed with C3b than as free factor B, generating the C3 convertase that drives the pathway [#11]. CFD itself is synthesized as a zymogen (profactor D) bearing an N-terminal activation peptide; in circulation it is continuously matured by MASP-3, while trypsin and other proteases can perform this conversion in vitro [#1, #11]. Serum reconstitution experiments establish CFD as the rate-limiting enzyme for alternative-pathway hemolysis, C3 deposition on bacteria, and complement-mediated bacterial killing [#0, #16]. CFD is filtered through the glomerulus and catabolized primarily by renal tubular cells, so renal failure causes marked plasma accumulation [#3]. Genetic ablation studies extend its role beyond serum complement: CFD-dependent alternative-pathway activation drives complement-mediated tissue injury in lupus nephritis and light-induced photoreceptor degeneration, yet plays a protective, adaptive role in clearing apoptotic cells during alcoholic liver disease [#6, #7, #8]. Beyond complement, CFD/adipsin promotes adipocyte differentiation and lipid accumulation through a C3a/C3aR signaling axis, an axis also operative in right-ventricular remodeling [#5, #9], and contributes to hepatocyte lipid metabolism, cardiomyocyte apoptosis, and endothelial dysfunction as documented across multiple tissue models [#15, #13, #10].\",\n  \"teleology\": [\n    {\n      \"year\": 1989,\n      \"claim\": \"Established that adipsin/CFD is enzymatically a complement factor D, resolving whether the adipocyte-derived protein had complement protease activity.\",\n      \"evidence\": \"In vitro enzymatic and hemolytic assays with recombinant mouse adipsin cleaving factor B in complex with activated C3\",\n      \"pmids\": [\"2734615\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve how CFD distinguishes free factor B from C3b-bound factor B\", \"No structural basis for substrate specificity\"]\n    },\n    {\n      \"year\": 1988,\n      \"claim\": \"Defined the route of CFD turnover, explaining why circulating CFD accumulates in renal disease.\",\n      \"evidence\": \"Radiolabelled factor D injection into humans with compartmental pharmacokinetic modeling and creatinine clearance correlation\",\n      \"pmids\": [\"3199673\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism of tubular uptake/degradation not defined\", \"Does not address consequences of accumulation for AP activity\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Showed CFD is made as a zymogen requiring activation-peptide removal, framing the question of its physiological activator.\",\n      \"evidence\": \"Baculovirus-expressed profactor D, amino acid sequencing, and trypsin/protease activation with hemolytic readout\",\n      \"pmids\": [\"8144940\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the physiological in vivo activating protease\", \"Relative contribution of thrombin/kallikrein/plasmin in vivo unknown\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Explained how CFD activity is regulated without zymogen cleavage or serpins, identifying substrate-induced conformational realignment as the control mechanism.\",\n      \"evidence\": \"Structural and active-site mutational analysis with esterolytic and hemolytic assays\",\n      \"pmids\": [\"8845746\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic dynamics of the resting-to-active transition not fully resolved\", \"Quantitative link between conformational change and cleavage rate not yet measured\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Demonstrated that CFD activity can be physically modulated by adsorption, providing a route to dampen alternative-pathway activation.\",\n      \"evidence\": \"In vitro incubation of serum/purified CFD with polyacrylonitrile fibers, hemolytic and immunoblot readouts\",\n      \"pmids\": [\"8479128\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab, in vitro only\", \"Clinical relevance of adsorptive removal not established here\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Established CFD-dependent alternative-pathway activation as the proximate driver of complement-mediated kidney injury in autoimmune disease.\",\n      \"evidence\": \"CFD-deficient MRL/lpr mice with histology, immunofluorescence for C3/IgG, and functional AP assay\",\n      \"pmids\": [\"14675043\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not address non-complement functions of CFD\", \"Human translatability not tested\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Extended CFD's pathogenic role to oxidative retinal injury, linking AP activity to photoreceptor death.\",\n      \"evidence\": \"CFD-knockout mice with light-exposure model, electroretinography, and histology\",\n      \"pmids\": [\"17962484\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cellular source of CFD in the retina not defined\", \"Downstream effector of photoreceptor death not identified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identified a non-complement, pro-adipogenic role for CFD acting through C3a/C3aR signaling.\",\n      \"evidence\": \"shRNA knockdown, overexpression, and C3aR-knockdown epistasis in preadipocyte differentiation with lipid staining and qPCR\",\n      \"pmids\": [\"27611793\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab, cell-based\", \"Whether C3a is generated by canonical AP convertase in this context not directly shown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Revealed that CFD-dependent AP amplification can be protective, clearing apoptotic cells in alcoholic liver disease rather than only causing injury.\",\n      \"evidence\": \"Multiple complement-pathway genetic KO models with ethanol feeding, C3 cleavage detection, apoptosis and cytokine readouts\",\n      \"pmids\": [\"29597356\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of apoptotic-cell recognition by AP not defined\", \"Tissue/context determinants of protective vs pathogenic AP not resolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Quantitatively confirmed CFD as the rate-limiting enzyme for AP bactericidal activity through serum reconstitution.\",\n      \"evidence\": \"FD-deficient patient serum reconstituted with factor D; AP hemolysis, C3 deposition on bacteria by flow cytometry, and killing assays\",\n      \"pmids\": [\"33841879\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Restricted to the bacterial species tested\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Linked CFD to platelet activation during sepsis, hinting at a coagulation interface.\",\n      \"evidence\": \"CFD-deficient mice in cecal ligation and puncture with flow cytometry for platelet GPIIb/IIIa\",\n      \"pmids\": [\"34396466\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single genetic model with a single flow cytometry readout; indirect mechanistic link\", \"No direct molecular pathway connecting CFD to platelet activation\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined a C3-CFD-C3aR signaling axis in right-ventricular remodeling, ordering the pathway in cardiac pathology.\",\n      \"evidence\": \"CFD- and C3-knockout mice plus C3aR antagonist with cardiac function and gene-expression readouts\",\n      \"pmids\": [\"36109509\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cellular target of C3aR signaling in RV not pinpointed\", \"Whether CFD acts locally vs systemically not resolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified upstream regulation of CFD by p38/cytokine signaling and a pro-proliferative role in squamous cell carcinoma.\",\n      \"evidence\": \"RT-qPCR, Western blot, danicopan inhibition, and p38 inhibitor in cSCC cells with proliferation readout\",\n      \"pmids\": [\"35053469\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Whether the effect requires complement convertase activity vs another mechanism unclear\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined a caspase-independent, PARP-1-mediated mechanism by which CFD drives cardiomyocyte apoptosis after infarction.\",\n      \"evidence\": \"Rat MI model, conditioned medium from epicardial adipose tissue, CFD and PARP-1 inhibitors, pan-caspase inhibitor controls\",\n      \"pmids\": [\"36351508\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Receptor linking secreted CFD to PARP-1 activation not identified\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showed glomerular endothelial cells produce CFD that drives local complement activation and endothelial dysfunction.\",\n      \"evidence\": \"siRNA knockdown in conditionally immortalized human glomerular endothelial cells with Ang II stimulation, IF, mass spec, ELISA\",\n      \"pmids\": [\"37188751\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Relative contribution of local vs circulating CFD in vivo not established\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Resolved the physiological activator of profactor D, identifying MASP-3 as the continuous maturase and quantifying zymogen residual activity.\",\n      \"evidence\": \"In vitro kinetics with MASP-1/MASP-3 fragments, Arg25Gln-stabilized proenzyme, and FD-depleted serum reconstitution\",\n      \"pmids\": [\"37283768\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Regulation of MASP-3 availability in vivo not addressed\", \"Whether pro-FD contributes meaningfully to AP under physiological conditions unresolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Placed CFD as a transcriptional target of HNF1\\u03b1 controlling hepatocyte lipid deposition.\",\n      \"evidence\": \"HNF1\\u03b1 P291fsinsC mutant mouse, transcriptomics/proteomics, CFD siRNA and inhibitor with triglyceride measurement\",\n      \"pmids\": [\"37841581\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Whether lipid effect depends on complement convertase activity not separated\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined adipsin/CFD as an autocrine amplifier of inflammatory and adipogenic signaling in Graves' orbitopathy fibroblasts.\",\n      \"evidence\": \"siRNA silencing and recombinant adipsin treatment with Akt/ERK/p38/JNK phosphorylation, qPCR, ELISA, and Oil Red O staining\",\n      \"pmids\": [\"37555734\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor mediating adipsin-induced kinase activation not identified\", \"Single lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstrated therapeutic CFD blockade mitigates aberrant AP amplification and protects endothelium in viral infection.\",\n      \"evidence\": \"Long-acting pH-sensitive anti-CFD antibody in human vascular organoid and macaque COVID-19 models with imaging and proteomics\",\n      \"pmids\": [\"37802037\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Mechanism of endothelial protection beyond reduced AP activation not detailed\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Linked CFD to hepatic steatosis via NF-\\u03baB signaling, connecting complement protease activity to metabolic and inflammatory gene programs.\",\n      \"evidence\": \"CRISPR CFD knockout and danicopan inhibition in a MAFLD mouse model with NF-\\u03baB assays, lipid and gene-expression readouts\",\n      \"pmids\": [\"41308544\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Whether NF-\\u03baB activation is downstream of C3a/C3aR or convertase-independent not resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How CFD's catalytic complement activity is mechanistically partitioned from its diverse C3a/C3aR-dependent and convertase-independent tissue signaling roles remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model distinguishing convertase-dependent vs independent CFD effects across tissues\", \"Direct receptors mediating non-complement CFD signaling not identified\", \"In vivo source (local vs circulating) of CFD in each pathology not systematically resolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 2, 11, 16]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 1, 11]},\n      {\"term_id\": \"GO:0008236\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [3, 10, 11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 6, 7, 8, 16]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [5, 15, 17]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CFB\", \"C3\", \"MASP3\", \"C3AR1\"],\n    \"other_free_text\": []\n  }\n}\n```","audit_flag":null,"evaluation":{"pairwise":"win"}}