{"gene":"GBP4","run_date":"2026-04-28T18:06:52","timeline":{"discoveries":[{"year":2007,"finding":"Human GBP4 (HuGBP-4) displays a distinct nucleocytoplasmic distribution in endothelial cells, unlike GBP-1, GBP-3, and GBP-5 which are exclusively cytoplasmic. GBP-4 is robustly induced by IFN-γ but not by TNF-α or IL-1β, and is never detected in the Golgi apparatus even upon IFN-γ and aluminum fluoride treatment, distinguishing it from GBP-1 and GBP-2.","method":"Time-lapse microscopy and fluorescence analyses of GFP-tagged HuGBPs, immunofluorescence, cytokine stimulation experiments","journal":"Journal of interferon & cytokine research","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization experiment with GFP-tagged protein and functional context, single lab","pmids":["17266443"],"is_preprint":false},{"year":2005,"finding":"GBPs, including GBP4, belong to the dynamin superfamily and possess unique GTPase activity capable of hydrolyzing GTP to both GDP and GMP, distinguishing them from other large GTPases.","method":"Biochemical GTPase assays, structural analysis review of the GBP family","journal":"Journal of interferon & cytokine research","confidence":"Low","confidence_rationale":"Tier 3 — review-level summary of biochemical activity ascribed to the GBP family; GBP4-specific assay data not individually described","pmids":["16108726"],"is_preprint":false},{"year":2006,"finding":"Genomic analysis confirmed that human GBP4 is located in the GBP gene cluster on chromosome 1 and, unlike most other human GBPs, lacks canonical GAS (IFN-γ activation site) and ISRE (IFN-stimulated response element) promoter elements, suggesting it may not be fully IFN-responsive in the same manner as other family members.","method":"In silico genomic and promoter analysis of human and murine GBP gene clusters","journal":"Journal of interferon & cytokine research","confidence":"Low","confidence_rationale":"Tier 4 — computational/genomic analysis only","pmids":["16689661"],"is_preprint":false},{"year":2010,"finding":"GBP-4 (non-prenylated) can be redirected to the subcellular compartment occupied by prenylated GBPs (GBP-1, GBP-2, GBP-5) through heterodimerization, demonstrating that GBP-4 participates in a hierarchical heterodimerization network that regulates intracellular trafficking of GBP family members.","method":"Co-immunoprecipitation, yeast two-hybrid analysis, fluorescence complementation assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods (Co-IP, Y2H, fluorescence complementation) in a single study","pmids":["21151871"],"is_preprint":false},{"year":2016,"finding":"Zebrafish Gbp4, an IFN-γ-inducible GTPase harboring a C-terminal CARD domain, is required for inflammasome-dependent clearance of Salmonella Typhimurium by neutrophils in vivo. Gbp4 requires the inflammasome adaptor Asc for its antibacterial function despite having its own CARD domain. The GTPase activity of Gbp4 is indispensable for inflammasome activation. Mechanistically, neutrophil recruitment occurs through Gbp4-independent production of CXCL8 and leukotriene B4, while bacterial clearance is mediated through Gbp4 inflammasome-dependent biosynthesis of prostaglandin D2.","method":"In vivo zebrafish infection model, genetic loss-of-function (morpholino/mutants), GTPase-dead mutant analysis, prostaglandin D2 measurement, CXCL8 and LTB4 measurement, Asc epistasis experiments","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal in vivo genetic approaches with defined phenotypic and biochemical readouts, replicated across conditions","pmids":["27363812"],"is_preprint":false},{"year":2024,"finding":"DNA hypo-methylation in regulatory regions of GBP4 drives its overexpression in pancreatic ductal carcinoma. GBP4 overexpression promotes infiltration of CD8+ T cells but simultaneously induces upregulation of immune checkpoint genes and T cell exhaustion. Targeted methylation of GBP4 regulatory loci using a dCas9-SunTag-DNMT3A system reduced GBP4 expression, validating its epigenetic regulation.","method":"Targeted DNA methylation (dCas9-SunTag-DNMT3A), chemotaxis assays, in vitro T cell killing assays with primary organoids, expression analysis","journal":"Cancer immunology, immunotherapy","confidence":"Medium","confidence_rationale":"Tier 2 — epigenetic editing with functional validation by chemotaxis and killing assays; single lab","pmids":["39110249"],"is_preprint":false},{"year":2025,"finding":"YTHDF1 recognizes m6A modification sites on GBP4 mRNA and enhances GBP4 protein expression, which in turn promotes M1 macrophage polarization. Knockdown of YTHDF1 reduced GBP4 expression and attenuated M1 polarization in an acute lung injury model.","method":"Mouse ALI model, GBP4 overexpression/knockdown, YTHDF1 knockdown, m6A site identification, macrophage polarization assays","journal":"Respiratory research","confidence":"Medium","confidence_rationale":"Tier 2 — loss-of-function for both YTHDF1 and GBP4 with defined cellular phenotype; single lab","pmids":["39806403"],"is_preprint":false},{"year":2025,"finding":"In a murine experimental cerebral malaria model, Gbp4 (downstream of IFN-γ but not IFN-α/β signaling) contributes to pathology by regulating antigen cross-presentation in endothelial cells of the olfactory bulb. Double knockout of Gbp4 and Irgb6 resulted in increased CD4+ and CD8+ T cell infiltration with reduced T cell functionality and impaired antigen presentation, leading to enhanced parasite accumulation and improved host survival.","method":"Gbp4 and Irgb6 single and double knockout mice, transcriptomic profiling (RNA-seq), T cell functional assays, flow cytometry, antigen presentation assays","journal":"mBio","confidence":"Medium","confidence_rationale":"Tier 2 — genetic knockout with multiple orthogonal functional readouts; single study","pmids":["40607809"],"is_preprint":false},{"year":2025,"finding":"In zebrafish, GBP4 functions downstream of type I IFN (IFN-φ1) signaling via the receptor CRFB1 during Salmonella Typhimurium challenge. Natterin deficiency abolished GBP4 expression and prevented proteolytic maturation of inflammatory caspases Caspy and Caspy2, placing GBP4 in the pathway: Natterin → IFN-φ1/CRFB1 → GBP4 → non-canonical inflammasome activation → Caspy2 maturation → gasdermin pore formation.","method":"CRISPR/Cas9 knockout of natterin, IFN-I neutralizing antibody, RT-qPCR, Western blotting, immunohistochemistry, survival assays","journal":"Frontiers in cellular and infection microbiology","confidence":"Medium","confidence_rationale":"Tier 2 — genetic and antibody-based epistasis with biochemical validation; single lab","pmids":["41220568"],"is_preprint":false},{"year":2026,"finding":"GBP4 physically interacts with NLRP3 in human spermatogonial stem cells, as demonstrated by co-immunoprecipitation. GBP4 shRNA knockdown decreased NLRP3 expression under LPS-induced inflammatory conditions, indicating GBP4 acts upstream to regulate NLRP3-dependent pyroptosis (caspase-1 and gasdermin D activation) in these cells.","method":"Co-immunoprecipitation (Co-IP), GBP4 shRNA knockdown, RNA-Seq, KEGG pathway and PPI analysis, LPS-induced pyroptosis model","journal":"Asian journal of andrology","confidence":"Medium","confidence_rationale":"Tier 2/3 — Co-IP demonstrating physical interaction plus functional shRNA knockdown; single lab","pmids":["41549441"],"is_preprint":false}],"current_model":"GBP4 is an IFN-γ-inducible dynamin-family GTPase with a nucleocytoplasmic distribution that participates in inflammasome activation (requiring its GTPase activity and the adaptor ASC) to drive prostaglandin D2-dependent bacterial clearance by neutrophils; it physically interacts with and regulates NLRP3, is subject to epigenetic control via DNA methylation and YTHDF1-mediated m6A modification of its mRNA, modulates antigen cross-presentation and T cell responses in infection and cancer contexts, and engages in heterodimerization with other GBP family members to regulate intracellular trafficking."},"narrative":{"teleology":[{"year":2006,"claim":"Genomic characterization of the GBP locus revealed that GBP4 lacks canonical GAS and ISRE promoter elements, raising the question of how its expression is regulated relative to other interferon-stimulated GBPs.","evidence":"In silico promoter and genomic analysis of the human and murine GBP gene clusters","pmids":["16689661"],"confidence":"Low","gaps":["Computational analysis only; no experimental promoter validation","Does not address tissue-specific regulatory elements","Functional consequence of absent GAS/ISRE elements untested"]},{"year":2007,"claim":"Direct imaging established that GBP4 has a unique nucleocytoplasmic distribution distinct from other GBPs and is selectively induced by IFN-γ but not TNF-α or IL-1β, defining its subcellular niche and activation signal.","evidence":"Time-lapse microscopy and fluorescence analysis of GFP-tagged GBP4 in endothelial cells with cytokine stimulation","pmids":["17266443"],"confidence":"Medium","gaps":["Localization studied only in endothelial cells; generalizability to immune cells unknown","Mechanism of nucleocytoplasmic partitioning not identified"]},{"year":2010,"claim":"Demonstration that GBP4 participates in a heterodimerization network with prenylated GBPs (GBP-1, -2, -5) explained how a non-prenylated GBP can be redirected to membrane compartments, establishing a trafficking regulation mechanism within the family.","evidence":"Co-immunoprecipitation, yeast two-hybrid, and fluorescence complementation assays","pmids":["21151871"],"confidence":"Medium","gaps":["Functional consequence of GBP4 relocalization not tested in infection models","Stoichiometry and structural basis of heterodimers undefined"]},{"year":2016,"claim":"In vivo genetic studies in zebrafish demonstrated that Gbp4's GTPase activity is indispensable for inflammasome activation and that Gbp4 drives ASC-dependent prostaglandin D2 biosynthesis for neutrophil-mediated bacterial clearance, establishing the first direct antimicrobial mechanism for GBP4.","evidence":"Zebrafish Salmonella infection model with morpholino knockdown, GTPase-dead mutants, Asc epistasis, and prostaglandin D2 measurement","pmids":["27363812"],"confidence":"High","gaps":["Zebrafish Gbp4 contains a C-terminal CARD domain absent in human GBP4; direct translational relevance uncertain","How GTPase activity couples to inflammasome assembly mechanistically unresolved"]},{"year":2024,"claim":"Epigenetic editing revealed that DNA hypomethylation drives GBP4 overexpression in pancreatic cancer, which promotes CD8+ T cell infiltration but simultaneously induces immune checkpoint upregulation and T cell exhaustion, uncovering a dual role in tumor immunity.","evidence":"dCas9-SunTag-DNMT3A targeted methylation, chemotaxis assays, and primary organoid T cell killing assays","pmids":["39110249"],"confidence":"Medium","gaps":["In vivo tumor model validation not reported","Direct mechanism linking GBP4 to checkpoint gene upregulation not identified"]},{"year":2025,"claim":"Multiple studies converged to define GBP4's roles in inflammasome signaling, antigen presentation, and macrophage polarization: YTHDF1-mediated m6A modification was shown to enhance GBP4 translation and promote M1 macrophage polarization; GBP4 was placed in a non-canonical inflammasome pathway downstream of type I IFN via Natterin/CRFB1; and Gbp4 knockout in mice impaired endothelial antigen cross-presentation, altering T cell function in cerebral malaria.","evidence":"Mouse acute lung injury model with YTHDF1/GBP4 knockdown; zebrafish CRISPR natterin knockout with epistasis; Gbp4/Irgb6 double-knockout mice with RNA-seq and T cell functional assays","pmids":["39806403","41220568","40607809"],"confidence":"Medium","gaps":["M1 polarization mechanism downstream of GBP4 not delineated","Relative contributions of Gbp4 versus Irgb6 in antigen presentation not fully resolved","Whether human GBP4 functions equivalently in non-canonical inflammasome activation untested"]},{"year":2026,"claim":"Physical interaction between GBP4 and NLRP3 was demonstrated, and GBP4 knockdown decreased NLRP3 expression during LPS-induced inflammation, establishing GBP4 as an upstream regulator of canonical NLRP3 inflammasome signaling in human cells.","evidence":"Co-immunoprecipitation and shRNA knockdown in human spermatogonial stem cells under LPS stimulation","pmids":["41549441"],"confidence":"Medium","gaps":["Reciprocal Co-IP not reported","Whether GBP4 stabilizes NLRP3 protein or regulates its transcription not distinguished","Single cell type (spermatogonial stem cells) limits generalizability"]},{"year":null,"claim":"The structural basis of GBP4 interaction with NLRP3 and other inflammasome components, the precise GTPase-dependent conformational changes driving inflammasome assembly, and whether human GBP4 (lacking a CARD domain) activates inflammasomes through the same mechanism as zebrafish Gbp4 remain open questions.","evidence":"","pmids":[],"confidence":"Low","gaps":["No crystal structure or cryo-EM structure of GBP4 or GBP4-NLRP3 complex","No reconstituted in vitro inflammasome activation assay with purified human GBP4","Mechanism linking GTPase cycle to effector recruitment unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003924","term_label":"GTPase activity","supporting_discovery_ids":[1,4]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[4,7,8,9]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[4,8,9]}],"complexes":[],"partners":["NLRP3","ASC","GBP1","GBP2","GBP5","YTHDF1"],"other_free_text":[]},"mechanistic_narrative":"GBP4 is an IFN-γ-inducible dynamin-superfamily GTPase that functions as a critical mediator of inflammasome activation and innate immune defense against intracellular bacteria. It exhibits a distinctive nucleocytoplasmic distribution, engages in heterodimerization with prenylated GBP family members to regulate intracellular trafficking, and activates inflammasomes in a GTPase activity– and ASC-dependent manner to drive prostaglandin D2–mediated bacterial clearance by neutrophils [PMID:17266443, PMID:21151871, PMID:27363812]. GBP4 physically interacts with NLRP3 and positively regulates NLRP3 expression and downstream pyroptotic signaling, while also functioning in non-canonical inflammasome pathways leading to gasdermin pore formation [PMID:41549441, PMID:41220568]. Beyond inflammasome biology, GBP4 modulates antigen cross-presentation and CD8+ T cell responses in both infection and cancer contexts, with its expression regulated epigenetically through DNA methylation and post-transcriptionally via YTHDF1-mediated m6A recognition [PMID:40607809, PMID:39110249, PMID:39806403]."},"prefetch_data":{"uniprot":{"accession":"Q96PP9","full_name":"Guanylate-binding protein 4","aliases":["GTP-binding protein 4","GBP-4","Guanine nucleotide-binding protein 4"],"length_aa":640,"mass_kda":73.2,"function":"Interferon (IFN)-inducible GTPase that plays important roles in innate immunity against a diverse range of bacterial, viral and protozoan pathogens (By similarity). Negatively regulates the antiviral response by inhibiting activation of IRF7 transcription factor (By similarity)","subcellular_location":"Golgi apparatus membrane; Cytoplasm; Nucleus; Cytoplasm, perinuclear region","url":"https://www.uniprot.org/uniprotkb/Q96PP9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GBP4","classification":"Not Classified","n_dependent_lines":5,"n_total_lines":1208,"dependency_fraction":0.0041390728476821195},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/GBP4","total_profiled":1310},"omim":[{"mim_id":"612468","title":"GUANYLATE-BINDING PROTEIN 7; GBP7","url":"https://www.omim.org/entry/612468"},{"mim_id":"612467","title":"GUANYLATE-BINDING PROTEIN 6; GBP6","url":"https://www.omim.org/entry/612467"},{"mim_id":"612466","title":"GUANYLATE-BINDING PROTEIN 4; GBP4","url":"https://www.omim.org/entry/612466"},{"mim_id":"611467","title":"GUANYLATE-BINDING PROTEIN 5: GBP5","url":"https://www.omim.org/entry/611467"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Golgi apparatus","reliability":"Supported"},{"location":"Plasma membrane","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GBP4"},"hgnc":{"alias_symbol":["Mpa2"],"prev_symbol":[]},"alphafold":{"accession":"Q96PP9","domains":[{"cath_id":"3.40.50.300","chopping":"32-168_186-325","consensus_level":"high","plddt":90.6835,"start":32,"end":325},{"cath_id":"1.10.287","chopping":"534-623","consensus_level":"medium","plddt":78.912,"start":534,"end":623}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96PP9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q96PP9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q96PP9-F1-predicted_aligned_error_v6.png","plddt_mean":85.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GBP4","jax_strain_url":"https://www.jax.org/strain/search?query=GBP4"},"sequence":{"accession":"Q96PP9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q96PP9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q96PP9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96PP9"}},"corpus_meta":[{"pmid":"27363812","id":"PMC_27363812","title":"Neutrophils mediate Salmonella Typhimurium clearance through the GBP4 inflammasome-dependent production of prostaglandins.","date":"2016","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/27363812","citation_count":102,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"29737453","id":"PMC_29737453","title":"Integrating CNVs into meta-QTL identified GBP4 as positional candidate for adult cattle stature.","date":"2018","source":"Functional & integrative genomics","url":"https://pubmed.ncbi.nlm.nih.gov/29737453","citation_count":19,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"16765538","id":"PMC_16765538","title":"High conservation of the differentially amplified MPA2 satellite DNA family in parthenogenetic root-knot nematodes.","date":"2006","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/16765538","citation_count":12,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"39110249","id":"PMC_39110249","title":"DNA hypo-methylation and 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standard","round2_stage1":{"model":"claude-sonnet-4-6","input_tokens":14320,"output_tokens":3616,"usd":0.0486},"round2_rules_fired":"R3","round2_stage2":{"model":"claude-opus-4-6","input_tokens":6292,"output_tokens":2224,"usd":0.13059}},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2016,\n      \"finding\": \"Zebrafish Gbp4, an IFNγ-inducible GTPase with a C-terminal CARD domain, functions as an inflammasome adaptor requiring the universal adaptor Asc for its antibacterial activity. Its GTPase activity is indispensable for inflammasome activation and Salmonella Typhimurium clearance by neutrophils, and it mediates bacterial clearance through inflammasome-dependent biosynthesis of prostaglandin D2.\",\n      \"method\": \"In vivo zebrafish infection model with genetic knockouts/knockdowns, GTPase-dead mutants, and prostaglandin D2 measurement\",\n      \"journal\": \"Nature Communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (genetic knockouts, mutagenesis, biochemical readouts) in a well-controlled in vivo model; >100 citations\",\n      \"pmids\": [\"27363812\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"GBP4 physically interacts with NLRP3 in human spermatogonial stem cells (Co-IP), and GBP4 knockdown (shRNA) reduces NLRP3 expression under inflammatory conditions, placing GBP4 upstream of NLRP3-mediated pyroptosis (Caspase-1 and Gasdermin D activation) triggered by LPS.\",\n      \"method\": \"Co-immunoprecipitation (Co-IP), GBP4 shRNA knockdown, RNA-Seq, NLRP3 siRNA, IL-18/IL-1β measurement, Caspase-1/Gasdermin D detection\",\n      \"journal\": \"Asian Journal of Andrology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP plus functional knockdown with defined pyroptosis readout, but single study, single lab\",\n      \"pmids\": [\"41549441\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"YTHDF1 enhances GBP4 expression by recognizing m6A modification sites on GBP4 mRNA; YTHDF1 knockdown reduces GBP4 expression and attenuates M1 macrophage polarization in acute lung injury models.\",\n      \"method\": \"m6A modification analysis, YTHDF1 knockdown experiments, GBP4 overexpression/knockdown, macrophage polarization assays in ALI mouse model\",\n      \"journal\": \"Respiratory Research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — functional knockdown with defined polarization phenotype and identified m6A reader, single lab study\",\n      \"pmids\": [\"39806403\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"DNA hypomethylation in regulatory regions of GBP4 drives its overexpression in pancreatic ductal carcinoma; targeted methylation via dCas9-SunTag-DNMT3A confirms regulatory control. GBP4 overexpression promotes CD8+ T cell infiltration but also upregulates immune checkpoint genes, inducing T cell exhaustion.\",\n      \"method\": \"Targeted methylation using dCas9-SunTag-DNMT3A-sgRNA system, GBP4 overexpression, chemotaxis assays, T cell killing assays with primary organoids\",\n      \"journal\": \"Cancer Immunology, Immunotherapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct epigenetic editing validates regulatory mechanism, functional downstream assays performed, single lab\",\n      \"pmids\": [\"39110249\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In a zebrafish model, Gbp4 functions downstream of IFN-φ1/CRFB1 signaling (IFN-I pathway), acting as an LPS sensor that licenses non-canonical inflammasome activation; Natterin deficiency abolishes Gbp4 expression and prevents proteolytic maturation of inflammatory caspases Caspy and Caspy2, abolishing downstream GSDME-mediated pore formation.\",\n      \"method\": \"CRISPR/Cas9 knockout of natterin, RT-qPCR, Western blotting, immunohistochemistry, IFN-I neutralizing antibody treatment in zebrafish embryos\",\n      \"journal\": \"Frontiers in Cellular and Infection Microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with CRISPR KO and multiple orthogonal methods placing Gbp4 in IFN-I/inflammasome pathway, but zebrafish model and single lab\",\n      \"pmids\": [\"41220568\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Mouse Gbp4 and Irgb6, acting downstream of IFN-γ but not IFN-α/β signaling, contribute to experimental cerebral malaria pathology by regulating antigen cross-presentation in endothelial cells of the olfactory bulb; double-knockout mice show increased CD4+/CD8+ T cell infiltration but reduced T cell functionality and impaired antigen presentation, leading to enhanced parasite accumulation.\",\n      \"method\": \"Gbp4 knockout, Irgb6 knockout, and double-knockout mice; transcriptomic profiling (RNA-seq); flow cytometry for T cell analysis; antigen presentation assays\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic KO with defined immune phenotype and pathway placement (IFN-γ downstream), single lab\",\n      \"pmids\": [\"40607809\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GBP4 is an IFNγ-inducible GTPase that acts as an inflammasome adaptor (requiring ASC and its own GTPase activity) to drive prostaglandin D2-dependent bacterial clearance by neutrophils; it physically interacts with and regulates NLRP3 upstream of pyroptosis; its expression is epigenetically controlled by DNA methylation and m6A modification (read by YTHDF1); and it contributes to antigen cross-presentation in endothelial cells downstream of IFN-γ signaling, modulating T cell-mediated immunity.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\nI'll classify each paper first, then extract discoveries from KEPT papers.\n\n**Classification:**\n\nRetrieved papers:\n1. PMID:27363812 — Zebrafish Gbp4 inflammasome/Salmonella study → KEEP (ortholog, consistent function)\n2. PMID:29737453 — Cattle GBP4 CNV/stature association → EXCLUDE (expression correlation only, no mechanism)\n3. PMID:16765538 — Nematode satellite DNA (MPA2) → EXCLUDE (symbol collision)\n4. PMID:39110249 — GBP4 in pancreatic cancer/T cell exhaustion → KEEP (mechanistic: DNA methylation regulation, chemotaxis assay)\n5. PMID:39806403 — YTHDF1/m6A/GBP4 in ALI → KEEP (mechanistic: m6A modification regulates GBP4)\n6. PMID:39868816 — GBP4 variants/DIALF → EXCLUDE (GWAS/association study)\n7. PMID:40607809 — Gbp4/Irgb6 in cerebral malaria → KEEP (mechanistic: KO with defined immune phenotype)\n8. PMID:40776645 — GBP4 in Crohn's disease (WGCNA/IHC) → EXCLUDE (biomarker/expression study)\n9. PMID:41220568 — Natterin/GBP4/inflammasome zebrafish → KEEP (mechanistic: pathway placement)\n10. PMID:41549441 — GBP4/NLRP3/pyroptosis in SSCs → KEEP (Co-IP, shRNA mechanism)\n\nGene2pubmed papers:\n- PMID:12477932 — MGC cDNA library → EXCLUDE (no GBP4-specific mechanism)\n- PMID:21873635 — GO annotation propagation → EXCLUDE (bioinformatics)\n- PMID:16689661 — GBP gene cluster genomics → KEEP (GBP4 genomic/expression characterization)\n- PMID:21151871 — GBP heterodimerization trafficking → KEEP (GBP-2 and GBP-4 localization data)\n- PMID:20379614 — Smoking cessation/nicotine genetics → EXCLUDE (no GBP4 mechanism)\n- PMID:23333304 — HIV Vif/CBFβ/RUNX1 → EXCLUDE (not GBP4)\n- PMID:30021884 — Crosslinking MS nuclei → EXCLUDE (not GBP4-specific)\n- PMID:17266443 — HuGBP expression/localization → KEEP (GBP-4 specific subcellular localization)\n- PMID:20237496 — Hepatitis B vaccine genetics → EXCLUDE (no GBP4 mechanism)\n- PMID:16108726 — GBP family GTPase review → KEEP (GTPase activity characterization)\n- PMID:36138187 — NUDT21/CD19/B-ALL → EXCLUDE (not GBP4)\n- PMID:24667918 — HIV Tat/BBB → EXCLUDE (not GBP4)\n- PMID:9659399 — Mouse GBP3 cloning → EXCLUDE (GBP3, not GBP4)\n- PMID:38347243 — GBP4 tumor microenvironment → EXCLUDE (expression/correlation)\n- PMID:23867815 — HIV gp120 gene expression → EXCLUDE (no GBP4 mechanism)\n- PMID:40437099 — EndoMAP endosome interactome → EXCLUDE (not GBP4)\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"Human GBP4 (HuGBP-4) displays a distinct nucleocytoplasmic distribution in endothelial cells, unlike GBP-1, GBP-3, and GBP-5 which are exclusively cytoplasmic. GBP-4 is robustly induced by IFN-γ but not by TNF-α or IL-1β, and is never detected in the Golgi apparatus even upon IFN-γ and aluminum fluoride treatment, distinguishing it from GBP-1 and GBP-2.\",\n      \"method\": \"Time-lapse microscopy and fluorescence analyses of GFP-tagged HuGBPs, immunofluorescence, cytokine stimulation experiments\",\n      \"journal\": \"Journal of interferon & cytokine research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization experiment with GFP-tagged protein and functional context, single lab\",\n      \"pmids\": [\"17266443\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"GBPs, including GBP4, belong to the dynamin superfamily and possess unique GTPase activity capable of hydrolyzing GTP to both GDP and GMP, distinguishing them from other large GTPases.\",\n      \"method\": \"Biochemical GTPase assays, structural analysis review of the GBP family\",\n      \"journal\": \"Journal of interferon & cytokine research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — review-level summary of biochemical activity ascribed to the GBP family; GBP4-specific assay data not individually described\",\n      \"pmids\": [\"16108726\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Genomic analysis confirmed that human GBP4 is located in the GBP gene cluster on chromosome 1 and, unlike most other human GBPs, lacks canonical GAS (IFN-γ activation site) and ISRE (IFN-stimulated response element) promoter elements, suggesting it may not be fully IFN-responsive in the same manner as other family members.\",\n      \"method\": \"In silico genomic and promoter analysis of human and murine GBP gene clusters\",\n      \"journal\": \"Journal of interferon & cytokine research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 — computational/genomic analysis only\",\n      \"pmids\": [\"16689661\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"GBP-4 (non-prenylated) can be redirected to the subcellular compartment occupied by prenylated GBPs (GBP-1, GBP-2, GBP-5) through heterodimerization, demonstrating that GBP-4 participates in a hierarchical heterodimerization network that regulates intracellular trafficking of GBP family members.\",\n      \"method\": \"Co-immunoprecipitation, yeast two-hybrid analysis, fluorescence complementation assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (Co-IP, Y2H, fluorescence complementation) in a single study\",\n      \"pmids\": [\"21151871\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Zebrafish Gbp4, an IFN-γ-inducible GTPase harboring a C-terminal CARD domain, is required for inflammasome-dependent clearance of Salmonella Typhimurium by neutrophils in vivo. Gbp4 requires the inflammasome adaptor Asc for its antibacterial function despite having its own CARD domain. The GTPase activity of Gbp4 is indispensable for inflammasome activation. Mechanistically, neutrophil recruitment occurs through Gbp4-independent production of CXCL8 and leukotriene B4, while bacterial clearance is mediated through Gbp4 inflammasome-dependent biosynthesis of prostaglandin D2.\",\n      \"method\": \"In vivo zebrafish infection model, genetic loss-of-function (morpholino/mutants), GTPase-dead mutant analysis, prostaglandin D2 measurement, CXCL8 and LTB4 measurement, Asc epistasis experiments\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal in vivo genetic approaches with defined phenotypic and biochemical readouts, replicated across conditions\",\n      \"pmids\": [\"27363812\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"DNA hypo-methylation in regulatory regions of GBP4 drives its overexpression in pancreatic ductal carcinoma. GBP4 overexpression promotes infiltration of CD8+ T cells but simultaneously induces upregulation of immune checkpoint genes and T cell exhaustion. Targeted methylation of GBP4 regulatory loci using a dCas9-SunTag-DNMT3A system reduced GBP4 expression, validating its epigenetic regulation.\",\n      \"method\": \"Targeted DNA methylation (dCas9-SunTag-DNMT3A), chemotaxis assays, in vitro T cell killing assays with primary organoids, expression analysis\",\n      \"journal\": \"Cancer immunology, immunotherapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — epigenetic editing with functional validation by chemotaxis and killing assays; single lab\",\n      \"pmids\": [\"39110249\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"YTHDF1 recognizes m6A modification sites on GBP4 mRNA and enhances GBP4 protein expression, which in turn promotes M1 macrophage polarization. Knockdown of YTHDF1 reduced GBP4 expression and attenuated M1 polarization in an acute lung injury model.\",\n      \"method\": \"Mouse ALI model, GBP4 overexpression/knockdown, YTHDF1 knockdown, m6A site identification, macrophage polarization assays\",\n      \"journal\": \"Respiratory research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function for both YTHDF1 and GBP4 with defined cellular phenotype; single lab\",\n      \"pmids\": [\"39806403\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In a murine experimental cerebral malaria model, Gbp4 (downstream of IFN-γ but not IFN-α/β signaling) contributes to pathology by regulating antigen cross-presentation in endothelial cells of the olfactory bulb. Double knockout of Gbp4 and Irgb6 resulted in increased CD4+ and CD8+ T cell infiltration with reduced T cell functionality and impaired antigen presentation, leading to enhanced parasite accumulation and improved host survival.\",\n      \"method\": \"Gbp4 and Irgb6 single and double knockout mice, transcriptomic profiling (RNA-seq), T cell functional assays, flow cytometry, antigen presentation assays\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic knockout with multiple orthogonal functional readouts; single study\",\n      \"pmids\": [\"40607809\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In zebrafish, GBP4 functions downstream of type I IFN (IFN-φ1) signaling via the receptor CRFB1 during Salmonella Typhimurium challenge. Natterin deficiency abolished GBP4 expression and prevented proteolytic maturation of inflammatory caspases Caspy and Caspy2, placing GBP4 in the pathway: Natterin → IFN-φ1/CRFB1 → GBP4 → non-canonical inflammasome activation → Caspy2 maturation → gasdermin pore formation.\",\n      \"method\": \"CRISPR/Cas9 knockout of natterin, IFN-I neutralizing antibody, RT-qPCR, Western blotting, immunohistochemistry, survival assays\",\n      \"journal\": \"Frontiers in cellular and infection microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic and antibody-based epistasis with biochemical validation; single lab\",\n      \"pmids\": [\"41220568\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"GBP4 physically interacts with NLRP3 in human spermatogonial stem cells, as demonstrated by co-immunoprecipitation. GBP4 shRNA knockdown decreased NLRP3 expression under LPS-induced inflammatory conditions, indicating GBP4 acts upstream to regulate NLRP3-dependent pyroptosis (caspase-1 and gasdermin D activation) in these cells.\",\n      \"method\": \"Co-immunoprecipitation (Co-IP), GBP4 shRNA knockdown, RNA-Seq, KEGG pathway and PPI analysis, LPS-induced pyroptosis model\",\n      \"journal\": \"Asian journal of andrology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — Co-IP demonstrating physical interaction plus functional shRNA knockdown; single lab\",\n      \"pmids\": [\"41549441\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GBP4 is an IFN-γ-inducible dynamin-family GTPase with a nucleocytoplasmic distribution that participates in inflammasome activation (requiring its GTPase activity and the adaptor ASC) to drive prostaglandin D2-dependent bacterial clearance by neutrophils; it physically interacts with and regulates NLRP3, is subject to epigenetic control via DNA methylation and YTHDF1-mediated m6A modification of its mRNA, modulates antigen cross-presentation and T cell responses in infection and cancer contexts, and engages in heterodimerization with other GBP family members to regulate intracellular trafficking.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"GBP4 is an interferon-inducible GTPase that functions as an inflammasome adaptor linking innate immune sensing to pyroptotic and inflammatory effector responses. In zebrafish, Gbp4 requires the universal inflammasome adaptor ASC and its own GTPase activity to drive caspase activation and prostaglandin D2-dependent bacterial clearance by neutrophils, and it acts downstream of IFN-I signaling as an LPS sensor licensing non-canonical inflammasome activation and gasdermin-mediated pore formation [PMID:27363812, PMID:41220568]. In mammalian cells, GBP4 physically interacts with NLRP3 and is required for NLRP3 expression and downstream Caspase-1/Gasdermin D-mediated pyroptosis; its expression is regulated by DNA methylation and by the m6A reader YTHDF1, which stabilizes GBP4 mRNA to promote M1 macrophage polarization [PMID:41549441, PMID:39806403, PMID:39110249]. GBP4 also contributes to IFN-γ-dependent antigen cross-presentation in endothelial cells, modulating CD8+ T cell-mediated immunity during infection [PMID:40607809].\",\n  \"teleology\": [\n    {\n      \"year\": 2016,\n      \"claim\": \"Establishing GBP4 as an inflammasome adaptor: it was unknown how IFN-γ-inducible GTPases linked to inflammasome function; zebrafish Gbp4 was shown to require ASC and its own GTPase activity for inflammasome activation and prostaglandin D2-dependent Salmonella clearance in neutrophils, defining GBP4 as a GTPase-dependent inflammasome adaptor.\",\n      \"evidence\": \"In vivo zebrafish infection with genetic knockouts, GTPase-dead mutants, and prostaglandin D2 measurement\",\n      \"pmids\": [\"27363812\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Mechanism by which GTPase activity triggers inflammasome assembly is undefined\",\n        \"Whether the CARD domain directly nucleates ASC specks was not resolved\",\n        \"Conservation of the prostaglandin D2 effector axis in mammals not tested\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Revealing epigenetic control of GBP4 expression: it was unknown how GBP4 becomes aberrantly overexpressed in tumors; targeted DNA methylation editing demonstrated that promoter hypomethylation drives GBP4 overexpression in pancreatic cancer, which recruits CD8+ T cells but simultaneously induces immune checkpoint upregulation and T cell exhaustion.\",\n      \"evidence\": \"dCas9-SunTag-DNMT3A targeted methylation, chemotaxis and T cell killing assays with patient-derived organoids\",\n      \"pmids\": [\"39110249\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether DNA methylation changes at the GBP4 locus are cause or consequence of tumor progression is unclear\",\n        \"Identity of immune checkpoint genes upregulated downstream of GBP4 not fully characterized\",\n        \"Single-lab study without independent replication\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Defining GBP4 as an NLRP3 interactor and pyroptosis regulator in mammalian cells: it was unknown whether GBP4 directly engaged canonical inflammasome sensors; Co-IP showed GBP4 physically binds NLRP3, and GBP4 knockdown reduced NLRP3 expression and attenuated Caspase-1/Gasdermin D activation, placing GBP4 upstream of NLRP3-mediated pyroptosis.\",\n      \"evidence\": \"Co-immunoprecipitation, shRNA knockdown, Caspase-1 and Gasdermin D detection in human spermatogonial stem cells\",\n      \"pmids\": [\"41549441\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Interaction awaits reciprocal Co-IP or endogenous pull-down validation\",\n        \"Whether GBP4 regulates NLRP3 transcriptionally or post-translationally is unresolved\",\n        \"Single cell type (spermatogonial stem cells) limits generalizability\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identifying m6A-dependent post-transcriptional regulation of GBP4: it was unknown how GBP4 mRNA stability was controlled; YTHDF1 was shown to read m6A marks on GBP4 mRNA to enhance its expression, coupling epitranscriptomic regulation to M1 macrophage polarization in acute lung injury.\",\n      \"evidence\": \"m6A modification analysis, YTHDF1 knockdown, GBP4 overexpression/knockdown, macrophage polarization assays in ALI mouse model\",\n      \"pmids\": [\"39806403\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Specific m6A sites on GBP4 mRNA were not mapped at nucleotide resolution\",\n        \"Whether YTHDF1 enhances GBP4 translation or mRNA stability was not distinguished\",\n        \"Single-lab study in one disease model\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Positioning Gbp4 in the IFN-I/non-canonical inflammasome axis: it was unknown how IFN-I signaling licensed non-canonical inflammasome activation; Gbp4 was placed downstream of IFN-φ1/CRFB1 and upstream of Caspy/Caspy2 maturation and GSDME pore formation, with Natterin required for Gbp4 expression.\",\n      \"evidence\": \"CRISPR/Cas9 natterin knockout, IFN-I neutralizing antibody, RT-qPCR and Western blot in zebrafish embryos\",\n      \"pmids\": [\"41220568\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct LPS-sensing mechanism by Gbp4 not biochemically demonstrated\",\n        \"Whether Natterin regulates Gbp4 transcriptionally or post-transcriptionally is unresolved\",\n        \"Zebrafish non-canonical pathway components differ from mammalian counterparts\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extending GBP4 function to antigen cross-presentation: it was unknown whether GBP4 regulated adaptive immunity beyond inflammasome signaling; Gbp4 knockout mice showed impaired endothelial antigen cross-presentation and reduced T cell functionality during cerebral malaria, establishing GBP4 as an IFN-γ-dependent regulator of MHC-I-restricted antigen presentation.\",\n      \"evidence\": \"Gbp4 and Irgb6 single/double-knockout mice, RNA-seq, flow cytometry, antigen presentation assays\",\n      \"pmids\": [\"40607809\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"GBP4 and Irgb6 contributions were not fully disentangled in double-knockout\",\n        \"Molecular mechanism by which GBP4 facilitates cross-presentation is unknown\",\n        \"Whether antigen presentation role is cell-autonomous to endothelial cells needs confirmation\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The structural basis for GBP4's interaction with NLRP3 and ASC, the precise mechanism by which GTPase activity triggers inflammasome assembly, and whether the inflammasome and antigen-presentation functions of GBP4 operate through shared or independent pathways remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No crystal structure or cryo-EM structure of GBP4 or its complexes\",\n        \"GTPase substrates and hydrolysis-coupled conformational changes uncharacterized\",\n        \"Relationship between inflammasome adaptor function and antigen cross-presentation role not tested\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003924\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 1, 4, 5]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [0, 1, 4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"NLRP3\",\n      \"ASC\",\n      \"YTHDF1\",\n      \"IRGB6\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"GBP4 is an IFN-γ-inducible dynamin-superfamily GTPase that functions as a critical mediator of inflammasome activation and innate immune defense against intracellular bacteria. It exhibits a distinctive nucleocytoplasmic distribution, engages in heterodimerization with prenylated GBP family members to regulate intracellular trafficking, and activates inflammasomes in a GTPase activity– and ASC-dependent manner to drive prostaglandin D2–mediated bacterial clearance by neutrophils [PMID:17266443, PMID:21151871, PMID:27363812]. GBP4 physically interacts with NLRP3 and positively regulates NLRP3 expression and downstream pyroptotic signaling, while also functioning in non-canonical inflammasome pathways leading to gasdermin pore formation [PMID:41549441, PMID:41220568]. Beyond inflammasome biology, GBP4 modulates antigen cross-presentation and CD8+ T cell responses in both infection and cancer contexts, with its expression regulated epigenetically through DNA methylation and post-transcriptionally via YTHDF1-mediated m6A recognition [PMID:40607809, PMID:39110249, PMID:39806403].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Genomic characterization of the GBP locus revealed that GBP4 lacks canonical GAS and ISRE promoter elements, raising the question of how its expression is regulated relative to other interferon-stimulated GBPs.\",\n      \"evidence\": \"In silico promoter and genomic analysis of the human and murine GBP gene clusters\",\n      \"pmids\": [\"16689661\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Computational analysis only; no experimental promoter validation\", \"Does not address tissue-specific regulatory elements\", \"Functional consequence of absent GAS/ISRE elements untested\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Direct imaging established that GBP4 has a unique nucleocytoplasmic distribution distinct from other GBPs and is selectively induced by IFN-γ but not TNF-α or IL-1β, defining its subcellular niche and activation signal.\",\n      \"evidence\": \"Time-lapse microscopy and fluorescence analysis of GFP-tagged GBP4 in endothelial cells with cytokine stimulation\",\n      \"pmids\": [\"17266443\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Localization studied only in endothelial cells; generalizability to immune cells unknown\", \"Mechanism of nucleocytoplasmic partitioning not identified\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Demonstration that GBP4 participates in a heterodimerization network with prenylated GBPs (GBP-1, -2, -5) explained how a non-prenylated GBP can be redirected to membrane compartments, establishing a trafficking regulation mechanism within the family.\",\n      \"evidence\": \"Co-immunoprecipitation, yeast two-hybrid, and fluorescence complementation assays\",\n      \"pmids\": [\"21151871\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of GBP4 relocalization not tested in infection models\", \"Stoichiometry and structural basis of heterodimers undefined\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"In vivo genetic studies in zebrafish demonstrated that Gbp4's GTPase activity is indispensable for inflammasome activation and that Gbp4 drives ASC-dependent prostaglandin D2 biosynthesis for neutrophil-mediated bacterial clearance, establishing the first direct antimicrobial mechanism for GBP4.\",\n      \"evidence\": \"Zebrafish Salmonella infection model with morpholino knockdown, GTPase-dead mutants, Asc epistasis, and prostaglandin D2 measurement\",\n      \"pmids\": [\"27363812\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Zebrafish Gbp4 contains a C-terminal CARD domain absent in human GBP4; direct translational relevance uncertain\", \"How GTPase activity couples to inflammasome assembly mechanistically unresolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Epigenetic editing revealed that DNA hypomethylation drives GBP4 overexpression in pancreatic cancer, which promotes CD8+ T cell infiltration but simultaneously induces immune checkpoint upregulation and T cell exhaustion, uncovering a dual role in tumor immunity.\",\n      \"evidence\": \"dCas9-SunTag-DNMT3A targeted methylation, chemotaxis assays, and primary organoid T cell killing assays\",\n      \"pmids\": [\"39110249\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo tumor model validation not reported\", \"Direct mechanism linking GBP4 to checkpoint gene upregulation not identified\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Multiple studies converged to define GBP4's roles in inflammasome signaling, antigen presentation, and macrophage polarization: YTHDF1-mediated m6A modification was shown to enhance GBP4 translation and promote M1 macrophage polarization; GBP4 was placed in a non-canonical inflammasome pathway downstream of type I IFN via Natterin/CRFB1; and Gbp4 knockout in mice impaired endothelial antigen cross-presentation, altering T cell function in cerebral malaria.\",\n      \"evidence\": \"Mouse acute lung injury model with YTHDF1/GBP4 knockdown; zebrafish CRISPR natterin knockout with epistasis; Gbp4/Irgb6 double-knockout mice with RNA-seq and T cell functional assays\",\n      \"pmids\": [\"39806403\", \"41220568\", \"40607809\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"M1 polarization mechanism downstream of GBP4 not delineated\", \"Relative contributions of Gbp4 versus Irgb6 in antigen presentation not fully resolved\", \"Whether human GBP4 functions equivalently in non-canonical inflammasome activation untested\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Physical interaction between GBP4 and NLRP3 was demonstrated, and GBP4 knockdown decreased NLRP3 expression during LPS-induced inflammation, establishing GBP4 as an upstream regulator of canonical NLRP3 inflammasome signaling in human cells.\",\n      \"evidence\": \"Co-immunoprecipitation and shRNA knockdown in human spermatogonial stem cells under LPS stimulation\",\n      \"pmids\": [\"41549441\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Reciprocal Co-IP not reported\", \"Whether GBP4 stabilizes NLRP3 protein or regulates its transcription not distinguished\", \"Single cell type (spermatogonial stem cells) limits generalizability\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The structural basis of GBP4 interaction with NLRP3 and other inflammasome components, the precise GTPase-dependent conformational changes driving inflammasome assembly, and whether human GBP4 (lacking a CARD domain) activates inflammasomes through the same mechanism as zebrafish Gbp4 remain open questions.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No crystal structure or cryo-EM structure of GBP4 or GBP4-NLRP3 complex\", \"No reconstituted in vitro inflammasome activation assay with purified human GBP4\", \"Mechanism linking GTPase cycle to effector recruitment unresolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003924\", \"supporting_discovery_ids\": [1, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [4, 7, 8, 9]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [4, 8, 9]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"NLRP3\",\n      \"ASC\",\n      \"GBP1\",\n      \"GBP2\",\n      \"GBP5\",\n      \"YTHDF1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}