{"gene":"C4BPA","run_date":"2026-06-09T22:02:45","timeline":{"discoveries":[{"year":1995,"finding":"The C4BPA promoter is contained within the first 369 bp upstream of the transcription start site, is active only in hepatic cells, and requires HNF1 binding at -38 bp for its activity; this requirement is absolute and the promoter lacks a TATA box.","method":"Transfection experiments with promoter deletion constructs, gel-shift/footprinting identifying HNF1 binding site at -38 bp","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — promoter deletion analysis plus transcription factor binding site identification in a single lab with two orthogonal methods","pmids":["7772049"],"is_preprint":false},{"year":1995,"finding":"IL-6, IL-1β, and IFN-γ increase both C4BPA and C4BPB mRNA levels in Hep3B cells, whereas TNF-α downregulates both; IFN-γ shows differential effects on the two chains; combined IFN-γ + TNF-α produces a synergistic ~10-fold induction of C4BPA mRNA but only marginal increase of C4BPB mRNA, suggesting differential cytokine regulation maintains stable C4BPβ concentrations during acute-phase induction.","method":"In vitro cytokine treatment of Hep3B hepatoma cells with mRNA quantification; analysis of C4BP isoforms in serial sera from acute-phase patients","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based mRNA quantification with multiple cytokine conditions, single lab, supported by patient serum isoform data","pmids":["7561114"],"is_preprint":false},{"year":1990,"finding":"The C4BPA and C4BPB genes are co-localized on human chromosome 1q32 within the regulators of complement activation (RCA) gene cluster, and both genes map to rat chromosome 13, indicating the beta-chain gene is a member of the RCA cluster.","method":"In situ hybridization with cDNA probes; Southern blotting of mouse-rat somatic cell hybrids","journal":"Somatic cell and molecular genetics","confidence":"High","confidence_rationale":"Tier 1 / Strong — two orthogonal mapping methods (in situ hybridization and somatic cell hybrid Southern blotting), findings mutually consistent","pmids":["2237642"],"is_preprint":false},{"year":2019,"finding":"Fetal C4BPA (present in cord blood exosomes) binds CD40 on placental villous trophoblasts to activate non-canonical NF-κB signaling (p100 processing to p52), inducing pro-labor genes; this was supported by computational, crystal structural, and gene functional analyses.","method":"Proteomics of fetal cord blood exosomes; computational docking; crystal structural analysis of C4BPA-CD40 interaction; gene functional assays in placental trophoblast cells","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (proteomics, structural, functional) in a single study; mechanistic validation is present but detail of in-cell rescue experiments is limited in the abstract","pmids":["30940885"],"is_preprint":false},{"year":2020,"finding":"C4BPA is expressed intracellularly in cancer cells (not only extracellularly), where it interacts with the NF-κB subunit RelA; increased intracellular C4BPA levels correlate with sensitivity to oxaliplatin-induced apoptosis, mechanistically via increased IκBα expression and enhanced inhibitory IκBα-RelA complex stability.","method":"Co-immunoprecipitation of C4BPA with RelA; cell lines with patient-specific C4BPA mutations; in vitro and in vivo oxaliplatin treatment; IκBα and RelA complex stability assays","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus functional in vitro/in vivo apoptosis assays in a single lab with multiple cell lines and patient-derived mutations","pmids":["33205012"],"is_preprint":false},{"year":2024,"finding":"S-palmitoylation of C4BPA at Cys15 in murine epididymal epithelial cells is required for its enrichment in epididymosomes and transfer to the sperm surface; palmitoylated C4BPA on sperm protects against complement C4-mediated attacks and maintains sperm motility, whereas the C15S mutant loses this protective function.","method":"Palmitoylation assays; C15S mutant expression; epididymosome isolation; sperm motility assays; complement C4 challenge; inhibition of palmitoylation with chemical inhibitors","journal":"International journal of biological macromolecules","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — site-directed mutagenesis of palmitoylation site combined with functional motility and complement-resistance assays; single lab","pmids":["39370067"],"is_preprint":false},{"year":2026,"finding":"In porcine epididymosomes, C4BPA is palmitoylated specifically at Cys13 and Cys23, a modification carried out by the palmitoyl transferase ZDHHC8; palmitoylated C4BPA in epididymosomes protects sperm from complement C4-mediated damage and maintains porcine sperm motility.","method":"Palmitoylation site mapping (Cys13/Cys23 identified); ZDHHC8 identified as the responsible palmitoyl transferase; epididymosome transfer assays; sperm motility and complement C4 challenge assays","journal":"Biochimica et biophysica acta. Molecular and cell biology of lipids","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — specific palmitoylation sites and enzyme identified, with functional validation in sperm; single lab, single paper","pmids":["41619901"],"is_preprint":false},{"year":2025,"finding":"Tumor-derived C4BPA promotes gastric cancer progression by activating JAK2/STAT3 signaling in tumor cells and increasing production of C3a and C5a; secreted C5a then acts via C5aR1 on macrophages to activate STAT3 and drive M2-like polarization, creating a pro-tumoral microenvironment.","method":"C4BPA knockdown and overexpression in GC cell lines; patient-derived GC organoids; subcutaneous xenograft mouse model; JAK2/STAT3 phosphorylation assays; macrophage (THP-1) co-culture with recombinant C5a rescue experiments","journal":"International immunopharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple in vitro and in vivo models with mechanistic rescue by recombinant C5a; single lab","pmids":["41237697"],"is_preprint":false},{"year":2026,"finding":"C4BPA knockout in bovine mammary epithelial cells activates Pink1/Parkin-mediated mitophagy (increased Pink1, Parkin, LC3B-II lipidation, LC3-mitochondria colocalization; decreased p62) and suppresses NF-κB signaling (decreased p-IκB and p-p65; increased IκBα and p65), resulting in reduced pro-inflammatory cytokine expression (TNF-α, IL-1β, IL-6).","method":"C4BPA knockout in bMECs; electron microscopy; immunofluorescence for LC3-mitochondria colocalization; Western blotting for Pink1, Parkin, LC3B-II, p62, p-IκB, p-p65, IκBα; ROS measurement; cytokine expression","journal":"Veterinary sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout with multiple orthogonal readouts (EM, immunofluorescence, protein quantification); single lab","pmids":["41745945"],"is_preprint":false},{"year":2026,"finding":"Recombinant C4BPA secreted by DMD fibroadipogenic precursor (FAP) cells impairs myoblast differentiation: treatment of healthy myoblasts with recombinant C4BPA reduced myotube area, nuclei per myotube, and myotube size, downregulated myogenic markers, upregulated muscle atrophy genes, and reduced contractile function in a 3D engineered muscle model; silencing C4BPA in DMD FAP cultures partially restored myogenic differentiation.","method":"Mass spectrometry of FAP secretome; recombinant C4BPA treatment of myoblasts; 3D engineered muscle model; C4BPA siRNA knockdown in DMD FAPs; myogenic differentiation index, nuclear content, and contractile function readouts","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — secretome proteomics plus recombinant protein functional assay plus siRNA rescue in both 2D and 3D models; single lab","pmids":["41851078"],"is_preprint":false}],"current_model":"C4BPA encodes the alpha-chain of C4b-binding protein, a complement regulator whose hepatic expression is driven by an HNF1-dependent promoter and is differentially regulated by acute-phase cytokines; beyond its extracellular complement-regulatory role, C4BPA undergoes S-palmitoylation (at Cys15 in mice, Cys13/Cys23 in pigs, by ZDHHC8) that is required for its trafficking into epididymosomes and onto sperm where it protects against complement C4-mediated damage; intracellularly, C4BPA interacts with RelA/NF-κB to modulate IκBα stability and apoptosis sensitivity; extracellularly, tumor-derived C4BPA activates JAK2/STAT3 in cancer cells and drives a C5a→C5aR1→STAT3 axis in macrophages promoting M2 polarization, while fetal C4BPA binds placental CD40 to activate non-canonical NF-κB (p100→p52) signaling, and secreted C4BPA from dystrophic FAPs impairs myoblast differentiation."},"narrative":{"mechanistic_narrative":"C4BPA encodes the alpha-chain of C4b-binding protein, a complement regulator transcribed from a hepatic, TATA-less promoter that absolutely requires HNF1 binding at -38 bp and is induced by acute-phase cytokines (IL-6, IL-1β, IFN-γ) while being repressed by TNF-α, with IFN-γ acting differentially on the alpha versus beta chains [PMID:7772049, PMID:7561114]. The gene lies in the regulators of complement activation (RCA) cluster at chromosome 1q32 alongside C4BPB [PMID:2237642]. Beyond its canonical extracellular role, C4BPA is S-palmitoylated—at Cys15 in mouse and Cys13/Cys23 in pig, the latter by the palmitoyl transferase ZDHHC8—a modification required for its loading into epididymosomes and transfer onto the sperm surface, where it protects sperm from complement C4-mediated damage and preserves motility [PMID:39370067, PMID:41619901]. C4BPA also acts intracellularly and in non-canonical signaling contexts: it binds the NF-κB subunit RelA to stabilize inhibitory IκBα-RelA complexes and sensitize cancer cells to oxaliplatin-induced apoptosis [PMID:33205012], and its loss activates Pink1/Parkin-mediated mitophagy with suppression of NF-κB and pro-inflammatory cytokines [PMID:41745945]. In disease settings, fetal C4BPA in cord-blood exosomes binds trophoblast CD40 to drive non-canonical NF-κB (p100→p52) processing and pro-labor gene induction [PMID:30940885], tumor-derived C4BPA activates JAK2/STAT3 and a C5a→C5aR1→STAT3 axis that polarizes macrophages toward an M2 pro-tumoral phenotype [PMID:41237697], and C4BPA secreted by dystrophic fibroadipogenic precursors impairs myoblast differentiation and contractile function [PMID:41851078].","teleology":[{"year":1990,"claim":"Establishing the genomic context resolved whether the C4BP alpha and beta chains are co-regulated members of a complement gene cluster.","evidence":"In situ hybridization and Southern blotting of somatic cell hybrids mapping C4BPA/C4BPB to human 1q32 and rat chromosome 13","pmids":["2237642"],"confidence":"High","gaps":["Does not address transcriptional co-regulation mechanism","No functional consequence of clustering tested"]},{"year":1995,"claim":"Defining the C4BPA promoter answered how its expression is restricted to liver and identified the transcription factor controlling it.","evidence":"Promoter deletion constructs and gel-shift/footprinting in hepatic cells identifying an absolute HNF1 requirement at -38 bp in a TATA-less promoter","pmids":["7772049"],"confidence":"Medium","gaps":["Other regulatory elements beyond -369 bp not characterized","No in vivo confirmation of HNF1 dependence"]},{"year":1995,"claim":"Cytokine-response profiling explained how C4BPA is regulated as an acute-phase protein and how alpha/beta stoichiometry is maintained.","evidence":"Cytokine treatment of Hep3B hepatoma cells with mRNA quantification plus acute-phase patient serum isoform analysis","pmids":["7561114"],"confidence":"Medium","gaps":["Signaling pathways linking cytokines to differential chain regulation not mapped","Protein-level induction inferred from mRNA"]},{"year":2019,"claim":"Identifying fetal C4BPA as a CD40 ligand revealed a signaling, non-complement role in placental biology and parturition.","evidence":"Cord-blood exosome proteomics, computational docking, crystal structural analysis, and functional assays in trophoblast cells showing CD40-driven p100→p52 processing","pmids":["30940885"],"confidence":"Medium","gaps":["In-cell rescue detail limited","Physiological contribution to labor timing not established in vivo"]},{"year":2020,"claim":"Discovery of intracellular C4BPA binding RelA established a cell-autonomous role in apoptosis regulation independent of complement.","evidence":"Co-IP of C4BPA with RelA, patient-mutation cell lines, and in vitro/in vivo oxaliplatin apoptosis and IκBα-RelA stability assays","pmids":["33205012"],"confidence":"Medium","gaps":["No reciprocal Co-IP or structural basis for RelA interaction","Mechanism of intracellular C4BPA retention not defined"]},{"year":2024,"claim":"Mapping S-palmitoylation at Cys15 explained how C4BPA is trafficked into epididymosomes and onto sperm to confer complement protection.","evidence":"Palmitoylation assays, C15S mutagenesis, epididymosome isolation, and sperm motility/complement C4 challenge in mouse","pmids":["39370067"],"confidence":"Medium","gaps":["Enzyme catalyzing mouse palmitoylation not identified","Mechanism of epididymosome sorting not detailed"]},{"year":2025,"claim":"Characterizing tumor-derived C4BPA defined a JAK2/STAT3 and C5a→C5aR1→STAT3 axis that remodels the tumor immune microenvironment.","evidence":"C4BPA knockdown/overexpression in gastric cancer lines, organoids, xenografts, and THP-1 macrophage co-culture with recombinant C5a rescue","pmids":["41237697"],"confidence":"Medium","gaps":["Direct receptor for C4BPA on tumor cells not identified","Single tumor type tested"]},{"year":2026,"claim":"Identifying ZDHHC8 and the Cys13/Cys23 sites in pig extended the palmitoylation-trafficking mechanism and named the responsible enzyme.","evidence":"Palmitoylation site mapping, ZDHHC8 identification, and epididymosome/sperm complement-protection assays in porcine system","pmids":["41619901"],"confidence":"Medium","gaps":["Whether ZDHHC8 acts on C4BPA in other species not tested","Subcellular site of palmitoylation not localized"]},{"year":2026,"claim":"C4BPA knockout in mammary epithelial cells linked the protein to suppression of mitophagy and NF-κB-driven inflammation.","evidence":"C4BPA knockout in bovine mammary epithelial cells with EM, LC3-mitochondria immunofluorescence, NF-κB pathway Western blots, ROS, and cytokine readouts","pmids":["41745945"],"confidence":"Medium","gaps":["Molecular link between C4BPA and Pink1/Parkin not defined","Whether intracellular RelA interaction underlies this effect untested"]},{"year":2026,"claim":"Secretome analysis of dystrophic FAPs identified C4BPA as a paracrine inhibitor of myogenic differentiation in muscular dystrophy.","evidence":"FAP secretome mass spectrometry, recombinant C4BPA treatment of myoblasts, 3D engineered muscle, and siRNA knockdown in DMD FAPs","pmids":["41851078"],"confidence":"Medium","gaps":["Receptor mediating myoblast effects unidentified","Signaling pathway downstream of C4BPA in myoblasts not mapped"]},{"year":null,"claim":"The unifying receptor logic and structural basis that allow a secreted complement regulator to also act as an intracellular RelA partner and a surface signaling ligand across reproductive, tumor, and muscle contexts remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No single mechanism reconciles intracellular vs extracellular C4BPA functions","Receptors for tumor and myoblast effects unknown","Trigger determining secreted vs retained C4BPA fate undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[5,6]},{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[3]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[4]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[3,7,9]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[4]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[3,5,6]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[5,6,7]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[3,4,7]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,1]}],"complexes":["C4b-binding protein","IκBα-RelA complex"],"partners":["RELA","CD40","ZDHHC8"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P04003","full_name":"C4b-binding protein alpha chain","aliases":["Proline-rich protein","PRP"],"length_aa":597,"mass_kda":67.0,"function":"Controls the classical pathway of complement activation. It binds as a cofactor to C3b/C4b inactivator (C3bINA), which then hydrolyzes the complement fragment C4b. It also accelerates the degradation of the C4bC2a complex (C3 convertase) by dissociating the complement fragment C2a. Alpha chain binds C4b. It also interacts with anticoagulant protein S and with serum amyloid P component","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/P04003/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/C4BPA","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/C4BPA","total_profiled":1310},"omim":[{"mim_id":"614514","title":"THROMBOPHILIA DUE TO PROTEIN S DEFICIENCY, AUTOSOMAL RECESSIVE; THPH6","url":"https://www.omim.org/entry/614514"},{"mim_id":"612922","title":"HEMOLYTIC UREMIC SYNDROME, ATYPICAL, SUSCEPTIBILITY TO, 2; AHUS2","url":"https://www.omim.org/entry/612922"},{"mim_id":"612336","title":"THROMBOPHILIA DUE TO PROTEIN S DEFICIENCY, AUTOSOMAL DOMINANT; THPH5","url":"https://www.omim.org/entry/612336"},{"mim_id":"235400","title":"HEMOLYTIC UREMIC SYNDROME, ATYPICAL, SUSCEPTIBILITY TO, 1; AHUS1","url":"https://www.omim.org/entry/235400"},{"mim_id":"176880","title":"PROTEIN S; PROS1","url":"https://www.omim.org/entry/176880"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"liver","ntpm":1793.3}],"url":"https://www.proteinatlas.org/search/C4BPA"},"hgnc":{"alias_symbol":[],"prev_symbol":["C4BP"]},"alphafold":{"accession":"P04003","domains":[{"cath_id":"2.10.70.10","chopping":"60-111","consensus_level":"medium","plddt":89.2077,"start":60,"end":111},{"cath_id":"2.10.70.10","chopping":"123-173","consensus_level":"medium","plddt":94.131,"start":123,"end":173},{"cath_id":"2.10.70.10","chopping":"175-236","consensus_level":"high","plddt":92.4102,"start":175,"end":236},{"cath_id":"2.10.70.10","chopping":"240-297","consensus_level":"medium","plddt":91.3186,"start":240,"end":297},{"cath_id":"2.10.70.10","chopping":"309-363","consensus_level":"medium","plddt":81.7107,"start":309,"end":363},{"cath_id":"-","chopping":"374-417","consensus_level":"medium","plddt":77.8402,"start":374,"end":417},{"cath_id":"2.10.70","chopping":"436-482","consensus_level":"high","plddt":80.4011,"start":436,"end":482},{"cath_id":"2.10.70.10","chopping":"487-564","consensus_level":"medium","plddt":85.2945,"start":487,"end":564}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P04003","model_url":"https://alphafold.ebi.ac.uk/files/AF-P04003-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P04003-F1-predicted_aligned_error_v6.png","plddt_mean":81.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=C4BPA","jax_strain_url":"https://www.jax.org/strain/search?query=C4BPA"},"sequence":{"accession":"P04003","fasta_url":"https://rest.uniprot.org/uniprotkb/P04003.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P04003/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P04003"}},"corpus_meta":[{"pmid":"27657339","id":"PMC_27657339","title":"Identification of a novel serum biomarker for pancreatic cancer, C4b-binding protein α-chain (C4BPA) by quantitative proteomic analysis using tandem mass tags.","date":"2016","source":"British journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/27657339","citation_count":78,"is_preprint":false},{"pmid":"7561114","id":"PMC_7561114","title":"Isoforms of human C4b-binding protein. II. Differential modulation of the C4BPA and C4BPB genes by acute phase cytokines.","date":"1995","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/7561114","citation_count":30,"is_preprint":false},{"pmid":"33205012","id":"PMC_33205012","title":"Intracellular C4BPA Levels Regulate NF-κB-Dependent Apoptosis.","date":"2020","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/33205012","citation_count":21,"is_preprint":false},{"pmid":"35173767","id":"PMC_35173767","title":"C4BPA: A Novel Co-Regulator of Immunity and Fat Metabolism in the Bovine Mammary Epithelial Cells.","date":"2022","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/35173767","citation_count":16,"is_preprint":false},{"pmid":"30940885","id":"PMC_30940885","title":"Fetal lung C4BPA induces p100 processing in human placenta.","date":"2019","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/30940885","citation_count":16,"is_preprint":false},{"pmid":"2237642","id":"PMC_2237642","title":"Genes for C4b-binding protein alpha- and beta-chains (C4BPA and C4BPB) are located on chromosome 1, band 1q32, in humans and on chromosome 13 in rats.","date":"1990","source":"Somatic cell and molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/2237642","citation_count":16,"is_preprint":false},{"pmid":"35935235","id":"PMC_35935235","title":"Association Between Plasma Exosomes S100A9/C4BPA and Latent Tuberculosis Infection Treatment: Proteomic Analysis Based on a Randomized Controlled Study.","date":"2022","source":"Frontiers in microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/35935235","citation_count":12,"is_preprint":false},{"pmid":"28627632","id":"PMC_28627632","title":"Association of single nucleotide polymorphisms in the 5' upstream region of the C4BPA gene with essential hypertension in a northeastern Han Chinese population.","date":"2017","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/28627632","citation_count":12,"is_preprint":false},{"pmid":"35733178","id":"PMC_35733178","title":"Potential biomarkers of spinal dural arteriovenous fistula: C4BPA and C1QA.","date":"2022","source":"Journal of neuroinflammation","url":"https://pubmed.ncbi.nlm.nih.gov/35733178","citation_count":10,"is_preprint":false},{"pmid":"7772049","id":"PMC_7772049","title":"Expression of the human gene coding for the alpha-chain of C4b-binding protein, C4BPA, is controlled by an HNF1-dependent hepatic-specific promoter.","date":"1995","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/7772049","citation_count":10,"is_preprint":false},{"pmid":"25660618","id":"PMC_25660618","title":"An evaluation of association between common variants in C4BPB/C4BPA genes and schizophrenia.","date":"2015","source":"Neuroscience letters","url":"https://pubmed.ncbi.nlm.nih.gov/25660618","citation_count":10,"is_preprint":false},{"pmid":"39370067","id":"PMC_39370067","title":"The role of S-palmitoylation of C4BPA in regulating murine sperm motility and complement resistance.","date":"2024","source":"International journal of biological macromolecules","url":"https://pubmed.ncbi.nlm.nih.gov/39370067","citation_count":6,"is_preprint":false},{"pmid":"39272751","id":"PMC_39272751","title":"Altered Expression of C4BPA and CXCL1 Genes in the Endometrium of Patients with Recurrent Implantation Failure after In Vitro Fertilization and Thin Endometrium.","date":"2024","source":"Diagnostics (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/39272751","citation_count":2,"is_preprint":false},{"pmid":"40237358","id":"PMC_40237358","title":"Identification of serum C4BPA as a potential diagnostic marker of right ventricular remodelling via proteomic analysis.","date":"2025","source":"ESC heart failure","url":"https://pubmed.ncbi.nlm.nih.gov/40237358","citation_count":1,"is_preprint":false},{"pmid":"41053817","id":"PMC_41053817","title":"Identification of C4BPA as a genetically informed drug target in NSCLC: an integrative single-cell and multi-omics study based on the druggable genes.","date":"2025","source":"Human genomics","url":"https://pubmed.ncbi.nlm.nih.gov/41053817","citation_count":0,"is_preprint":false},{"pmid":"41237697","id":"PMC_41237697","title":"Tumor-derived C4BPA promotes macrophage M2-like polarization through C5a -C5aR1-STAT3 axis and drives gastric cancer progression.","date":"2025","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/41237697","citation_count":0,"is_preprint":false},{"pmid":"41851078","id":"PMC_41851078","title":"Impact of C4BPA on Muscle progenitor cell differentiation: insights for Duchenne muscular dystrophy treatment.","date":"2026","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/41851078","citation_count":0,"is_preprint":false},{"pmid":"41745945","id":"PMC_41745945","title":"Knockout of the C4BPA Gene Promotes Mitophagy via Activation of the Pink1/Parkin Pathway and Alleviates the Inflammatory Response by Inhibiting the NF-κB Signalling Pathway in Bovine Mammary Epithelial Cells.","date":"2026","source":"Veterinary sciences","url":"https://pubmed.ncbi.nlm.nih.gov/41745945","citation_count":0,"is_preprint":false},{"pmid":"41619901","id":"PMC_41619901","title":"Palmitoylation of C4BPA in porcine epididymosomes mitigates complement C4-mediated damage to sperm.","date":"2026","source":"Biochimica et biophysica acta. Molecular and cell biology of lipids","url":"https://pubmed.ncbi.nlm.nih.gov/41619901","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":12354,"output_tokens":2881,"usd":0.040139,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10223,"output_tokens":3575,"usd":0.070245,"stage2_stop_reason":"end_turn"},"total_usd":0.110384,"stage1_batch_id":"msgbatch_0179Z2pxRYBsXi2xADneafRw","stage2_batch_id":"msgbatch_01LaY9ZaVdgjWArcZo9eqQE5","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1995,\n      \"finding\": \"The C4BPA promoter is contained within the first 369 bp upstream of the transcription start site, is active only in hepatic cells, and requires HNF1 binding at -38 bp for its activity; this requirement is absolute and the promoter lacks a TATA box.\",\n      \"method\": \"Transfection experiments with promoter deletion constructs, gel-shift/footprinting identifying HNF1 binding site at -38 bp\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — promoter deletion analysis plus transcription factor binding site identification in a single lab with two orthogonal methods\",\n      \"pmids\": [\"7772049\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"IL-6, IL-1β, and IFN-γ increase both C4BPA and C4BPB mRNA levels in Hep3B cells, whereas TNF-α downregulates both; IFN-γ shows differential effects on the two chains; combined IFN-γ + TNF-α produces a synergistic ~10-fold induction of C4BPA mRNA but only marginal increase of C4BPB mRNA, suggesting differential cytokine regulation maintains stable C4BPβ concentrations during acute-phase induction.\",\n      \"method\": \"In vitro cytokine treatment of Hep3B hepatoma cells with mRNA quantification; analysis of C4BP isoforms in serial sera from acute-phase patients\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based mRNA quantification with multiple cytokine conditions, single lab, supported by patient serum isoform data\",\n      \"pmids\": [\"7561114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1990,\n      \"finding\": \"The C4BPA and C4BPB genes are co-localized on human chromosome 1q32 within the regulators of complement activation (RCA) gene cluster, and both genes map to rat chromosome 13, indicating the beta-chain gene is a member of the RCA cluster.\",\n      \"method\": \"In situ hybridization with cDNA probes; Southern blotting of mouse-rat somatic cell hybrids\",\n      \"journal\": \"Somatic cell and molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — two orthogonal mapping methods (in situ hybridization and somatic cell hybrid Southern blotting), findings mutually consistent\",\n      \"pmids\": [\"2237642\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Fetal C4BPA (present in cord blood exosomes) binds CD40 on placental villous trophoblasts to activate non-canonical NF-κB signaling (p100 processing to p52), inducing pro-labor genes; this was supported by computational, crystal structural, and gene functional analyses.\",\n      \"method\": \"Proteomics of fetal cord blood exosomes; computational docking; crystal structural analysis of C4BPA-CD40 interaction; gene functional assays in placental trophoblast cells\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (proteomics, structural, functional) in a single study; mechanistic validation is present but detail of in-cell rescue experiments is limited in the abstract\",\n      \"pmids\": [\"30940885\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"C4BPA is expressed intracellularly in cancer cells (not only extracellularly), where it interacts with the NF-κB subunit RelA; increased intracellular C4BPA levels correlate with sensitivity to oxaliplatin-induced apoptosis, mechanistically via increased IκBα expression and enhanced inhibitory IκBα-RelA complex stability.\",\n      \"method\": \"Co-immunoprecipitation of C4BPA with RelA; cell lines with patient-specific C4BPA mutations; in vitro and in vivo oxaliplatin treatment; IκBα and RelA complex stability assays\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus functional in vitro/in vivo apoptosis assays in a single lab with multiple cell lines and patient-derived mutations\",\n      \"pmids\": [\"33205012\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"S-palmitoylation of C4BPA at Cys15 in murine epididymal epithelial cells is required for its enrichment in epididymosomes and transfer to the sperm surface; palmitoylated C4BPA on sperm protects against complement C4-mediated attacks and maintains sperm motility, whereas the C15S mutant loses this protective function.\",\n      \"method\": \"Palmitoylation assays; C15S mutant expression; epididymosome isolation; sperm motility assays; complement C4 challenge; inhibition of palmitoylation with chemical inhibitors\",\n      \"journal\": \"International journal of biological macromolecules\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — site-directed mutagenesis of palmitoylation site combined with functional motility and complement-resistance assays; single lab\",\n      \"pmids\": [\"39370067\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"In porcine epididymosomes, C4BPA is palmitoylated specifically at Cys13 and Cys23, a modification carried out by the palmitoyl transferase ZDHHC8; palmitoylated C4BPA in epididymosomes protects sperm from complement C4-mediated damage and maintains porcine sperm motility.\",\n      \"method\": \"Palmitoylation site mapping (Cys13/Cys23 identified); ZDHHC8 identified as the responsible palmitoyl transferase; epididymosome transfer assays; sperm motility and complement C4 challenge assays\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular and cell biology of lipids\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — specific palmitoylation sites and enzyme identified, with functional validation in sperm; single lab, single paper\",\n      \"pmids\": [\"41619901\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Tumor-derived C4BPA promotes gastric cancer progression by activating JAK2/STAT3 signaling in tumor cells and increasing production of C3a and C5a; secreted C5a then acts via C5aR1 on macrophages to activate STAT3 and drive M2-like polarization, creating a pro-tumoral microenvironment.\",\n      \"method\": \"C4BPA knockdown and overexpression in GC cell lines; patient-derived GC organoids; subcutaneous xenograft mouse model; JAK2/STAT3 phosphorylation assays; macrophage (THP-1) co-culture with recombinant C5a rescue experiments\",\n      \"journal\": \"International immunopharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple in vitro and in vivo models with mechanistic rescue by recombinant C5a; single lab\",\n      \"pmids\": [\"41237697\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"C4BPA knockout in bovine mammary epithelial cells activates Pink1/Parkin-mediated mitophagy (increased Pink1, Parkin, LC3B-II lipidation, LC3-mitochondria colocalization; decreased p62) and suppresses NF-κB signaling (decreased p-IκB and p-p65; increased IκBα and p65), resulting in reduced pro-inflammatory cytokine expression (TNF-α, IL-1β, IL-6).\",\n      \"method\": \"C4BPA knockout in bMECs; electron microscopy; immunofluorescence for LC3-mitochondria colocalization; Western blotting for Pink1, Parkin, LC3B-II, p62, p-IκB, p-p65, IκBα; ROS measurement; cytokine expression\",\n      \"journal\": \"Veterinary sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout with multiple orthogonal readouts (EM, immunofluorescence, protein quantification); single lab\",\n      \"pmids\": [\"41745945\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Recombinant C4BPA secreted by DMD fibroadipogenic precursor (FAP) cells impairs myoblast differentiation: treatment of healthy myoblasts with recombinant C4BPA reduced myotube area, nuclei per myotube, and myotube size, downregulated myogenic markers, upregulated muscle atrophy genes, and reduced contractile function in a 3D engineered muscle model; silencing C4BPA in DMD FAP cultures partially restored myogenic differentiation.\",\n      \"method\": \"Mass spectrometry of FAP secretome; recombinant C4BPA treatment of myoblasts; 3D engineered muscle model; C4BPA siRNA knockdown in DMD FAPs; myogenic differentiation index, nuclear content, and contractile function readouts\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — secretome proteomics plus recombinant protein functional assay plus siRNA rescue in both 2D and 3D models; single lab\",\n      \"pmids\": [\"41851078\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"C4BPA encodes the alpha-chain of C4b-binding protein, a complement regulator whose hepatic expression is driven by an HNF1-dependent promoter and is differentially regulated by acute-phase cytokines; beyond its extracellular complement-regulatory role, C4BPA undergoes S-palmitoylation (at Cys15 in mice, Cys13/Cys23 in pigs, by ZDHHC8) that is required for its trafficking into epididymosomes and onto sperm where it protects against complement C4-mediated damage; intracellularly, C4BPA interacts with RelA/NF-κB to modulate IκBα stability and apoptosis sensitivity; extracellularly, tumor-derived C4BPA activates JAK2/STAT3 in cancer cells and drives a C5a→C5aR1→STAT3 axis in macrophages promoting M2 polarization, while fetal C4BPA binds placental CD40 to activate non-canonical NF-κB (p100→p52) signaling, and secreted C4BPA from dystrophic FAPs impairs myoblast differentiation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"C4BPA encodes the alpha-chain of C4b-binding protein, a complement regulator transcribed from a hepatic, TATA-less promoter that absolutely requires HNF1 binding at -38 bp and is induced by acute-phase cytokines (IL-6, IL-1\\u03b2, IFN-\\u03b3) while being repressed by TNF-\\u03b1, with IFN-\\u03b3 acting differentially on the alpha versus beta chains [#0, #1]. The gene lies in the regulators of complement activation (RCA) cluster at chromosome 1q32 alongside C4BPB [#2]. Beyond its canonical extracellular role, C4BPA is S-palmitoylated\\u2014at Cys15 in mouse and Cys13/Cys23 in pig, the latter by the palmitoyl transferase ZDHHC8\\u2014a modification required for its loading into epididymosomes and transfer onto the sperm surface, where it protects sperm from complement C4-mediated damage and preserves motility [#5, #6]. C4BPA also acts intracellularly and in non-canonical signaling contexts: it binds the NF-\\u03baB subunit RelA to stabilize inhibitory I\\u03baB\\u03b1-RelA complexes and sensitize cancer cells to oxaliplatin-induced apoptosis [#4], and its loss activates Pink1/Parkin-mediated mitophagy with suppression of NF-\\u03baB and pro-inflammatory cytokines [#8]. In disease settings, fetal C4BPA in cord-blood exosomes binds trophoblast CD40 to drive non-canonical NF-\\u03baB (p100\\u2192p52) processing and pro-labor gene induction [#3], tumor-derived C4BPA activates JAK2/STAT3 and a C5a\\u2192C5aR1\\u2192STAT3 axis that polarizes macrophages toward an M2 pro-tumoral phenotype [#7], and C4BPA secreted by dystrophic fibroadipogenic precursors impairs myoblast differentiation and contractile function [#9].\",\n  \"teleology\": [\n    {\n      \"year\": 1990,\n      \"claim\": \"Establishing the genomic context resolved whether the C4BP alpha and beta chains are co-regulated members of a complement gene cluster.\",\n      \"evidence\": \"In situ hybridization and Southern blotting of somatic cell hybrids mapping C4BPA/C4BPB to human 1q32 and rat chromosome 13\",\n      \"pmids\": [\"2237642\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not address transcriptional co-regulation mechanism\", \"No functional consequence of clustering tested\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Defining the C4BPA promoter answered how its expression is restricted to liver and identified the transcription factor controlling it.\",\n      \"evidence\": \"Promoter deletion constructs and gel-shift/footprinting in hepatic cells identifying an absolute HNF1 requirement at -38 bp in a TATA-less promoter\",\n      \"pmids\": [\"7772049\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Other regulatory elements beyond -369 bp not characterized\", \"No in vivo confirmation of HNF1 dependence\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Cytokine-response profiling explained how C4BPA is regulated as an acute-phase protein and how alpha/beta stoichiometry is maintained.\",\n      \"evidence\": \"Cytokine treatment of Hep3B hepatoma cells with mRNA quantification plus acute-phase patient serum isoform analysis\",\n      \"pmids\": [\"7561114\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Signaling pathways linking cytokines to differential chain regulation not mapped\", \"Protein-level induction inferred from mRNA\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identifying fetal C4BPA as a CD40 ligand revealed a signaling, non-complement role in placental biology and parturition.\",\n      \"evidence\": \"Cord-blood exosome proteomics, computational docking, crystal structural analysis, and functional assays in trophoblast cells showing CD40-driven p100\\u2192p52 processing\",\n      \"pmids\": [\"30940885\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In-cell rescue detail limited\", \"Physiological contribution to labor timing not established in vivo\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Discovery of intracellular C4BPA binding RelA established a cell-autonomous role in apoptosis regulation independent of complement.\",\n      \"evidence\": \"Co-IP of C4BPA with RelA, patient-mutation cell lines, and in vitro/in vivo oxaliplatin apoptosis and I\\u03baB\\u03b1-RelA stability assays\",\n      \"pmids\": [\"33205012\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No reciprocal Co-IP or structural basis for RelA interaction\", \"Mechanism of intracellular C4BPA retention not defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Mapping S-palmitoylation at Cys15 explained how C4BPA is trafficked into epididymosomes and onto sperm to confer complement protection.\",\n      \"evidence\": \"Palmitoylation assays, C15S mutagenesis, epididymosome isolation, and sperm motility/complement C4 challenge in mouse\",\n      \"pmids\": [\"39370067\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Enzyme catalyzing mouse palmitoylation not identified\", \"Mechanism of epididymosome sorting not detailed\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Characterizing tumor-derived C4BPA defined a JAK2/STAT3 and C5a\\u2192C5aR1\\u2192STAT3 axis that remodels the tumor immune microenvironment.\",\n      \"evidence\": \"C4BPA knockdown/overexpression in gastric cancer lines, organoids, xenografts, and THP-1 macrophage co-culture with recombinant C5a rescue\",\n      \"pmids\": [\"41237697\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct receptor for C4BPA on tumor cells not identified\", \"Single tumor type tested\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Identifying ZDHHC8 and the Cys13/Cys23 sites in pig extended the palmitoylation-trafficking mechanism and named the responsible enzyme.\",\n      \"evidence\": \"Palmitoylation site mapping, ZDHHC8 identification, and epididymosome/sperm complement-protection assays in porcine system\",\n      \"pmids\": [\"41619901\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether ZDHHC8 acts on C4BPA in other species not tested\", \"Subcellular site of palmitoylation not localized\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"C4BPA knockout in mammary epithelial cells linked the protein to suppression of mitophagy and NF-\\u03baB-driven inflammation.\",\n      \"evidence\": \"C4BPA knockout in bovine mammary epithelial cells with EM, LC3-mitochondria immunofluorescence, NF-\\u03baB pathway Western blots, ROS, and cytokine readouts\",\n      \"pmids\": [\"41745945\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular link between C4BPA and Pink1/Parkin not defined\", \"Whether intracellular RelA interaction underlies this effect untested\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Secretome analysis of dystrophic FAPs identified C4BPA as a paracrine inhibitor of myogenic differentiation in muscular dystrophy.\",\n      \"evidence\": \"FAP secretome mass spectrometry, recombinant C4BPA treatment of myoblasts, 3D engineered muscle, and siRNA knockdown in DMD FAPs\",\n      \"pmids\": [\"41851078\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor mediating myoblast effects unidentified\", \"Signaling pathway downstream of C4BPA in myoblasts not mapped\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The unifying receptor logic and structural basis that allow a secreted complement regulator to also act as an intracellular RelA partner and a surface signaling ligand across reproductive, tumor, and muscle contexts remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No single mechanism reconciles intracellular vs extracellular C4BPA functions\", \"Receptors for tumor and myoblast effects unknown\", \"Trigger determining secreted vs retained C4BPA fate undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [5, 6]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [3, 7, 9]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [3, 5, 6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [5, 6, 7]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 4, 7]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"complexes\": [\n      \"C4b-binding protein\",\n      \"I\\u03baB\\u03b1-RelA complex\"\n    ],\n    \"partners\": [\n      \"RELA\",\n      \"CD40\",\n      \"ZDHHC8\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":5,"faith_total":5,"faith_pct":100.0}}