{"gene":"BTN3A2","run_date":"2026-06-09T22:02:45","timeline":{"discoveries":[{"year":2019,"finding":"BTN3A2 overexpression specifically suppressed excitatory synaptic activity onto CA1 pyramidal neurons in rat hippocampal slices, and BTN3A2 was shown to interact with presynaptic adhesion molecules neurexins via cell surface binding assay.","method":"Electrophysiology (rat hippocampal slice overexpression), cell surface binding assay","journal":"EBioMedicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two orthogonal methods (electrophysiology + binding assay) in a single lab establishing both functional effect and binding partner","pmids":["31133542"],"is_preprint":false},{"year":2024,"finding":"BTN3A2 interacts with the receptor-binding domain (RBD) of the SARS-CoV-2 Spike protein and with ACE2, inhibiting SARS-CoV-2 attachment. BTN3A2 reduces ACE2 levels both in vitro and in vivo, thereby inhibiting ACE2-mediated viral infection.","method":"Immunoprecipitation, flow cytometry, biolayer interferometry, competition ELISA, BTN3A2-edited cell lines and transgenic mice infected with live SARS-CoV-2","journal":"EBioMedicine","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal biochemical methods (biolayer interferometry, competition ELISA, Co-IP) plus in vivo validation in transgenic mice with live virus","pmids":["39142074"],"is_preprint":false},{"year":2024,"finding":"Cryo-EM structures of the full-length BTN3A1–BTN3A2–BTN2A1 complex stabilized by the phosphoantigen HMBPP revealed that HMBPP bridges the intracellular B30.2 domains of BTN3A1 and BTN2A1, while BTN3A2 and BTN2A1 ectodomains associate in the primed complex. Upon Vγ9Vδ2 TCR engagement, the BTN3A2–BTN2A1 ectodomain interaction dissociates; BTN2A1 binds the lateral surface of the Vγ9 chain and BTN3A2 binds the apical surface of the Vδ2 chain, confirming BTN3A2 as a bona fide TCR ligand and revealing a 'pliers-like gripping' mechanism for TCR activation.","method":"Cryo-EM structural determination of full-length protein complexes, functional antibody complex structures","journal":"bioRxiv (preprint)","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structures of full-length complexes with multiple states (primed and TCR-engaged) providing atomic-level mechanistic insight","pmids":["bio_10.1101_2024.10.02.616253"],"is_preprint":true},{"year":2017,"finding":"Deletion of BTN3A2 inhibited proliferation, migration, and invasion of gastric cancer cells; a protective allele at rs1679709 reduced enhancer activity at this locus and decreased BTN3A2 expression.","method":"CRISPR/Cas9 gene deletion, reporter construct (enhancer activity assay), cell proliferation/migration/invasion assays","journal":"Gastroenterology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR KO with multiple cellular phenotype readouts plus reporter assay for regulatory mechanism, single lab","pmids":["28246015"],"is_preprint":false},{"year":2025,"finding":"BTN3A2 physically interacts with MFGE8 (milk fat globule-EGF factor 8), and this interaction promotes hypoxia-induced ferroptosis in HUVECs by downregulating MFGE8, thereby inhibiting angiogenesis.","method":"Co-immunoprecipitation (BTN3A2–MFGE8 interaction), siRNA knockdown, overexpression in HUVECs, rat PE model in vivo","journal":"Life sciences","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP identifying binding partner plus functional knockdown/overexpression with defined phenotypic readouts and in vivo model, single lab","pmids":["40147528"],"is_preprint":false},{"year":2026,"finding":"BTN3A2 is a hypoxia-responsive gene directly transcriptionally activated by HIF-1α, and BTN3A2 promotes chemoresistance in glioma by activating the AKT/SP1/RAD51 axis to enhance DNA damage repair capacity, thereby conferring temozolomide (TMZ) resistance.","method":"RNA-seq, CUT&Tag, promoter luciferase assay, lentivirus-mediated BTN3A2 knockdown in vitro and in vivo (TMZ sensitivity assay)","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (CUT&Tag chromatin profiling, luciferase, RNA-seq, in vivo KD) in a single lab establishing transcriptional mechanism and downstream pathway","pmids":["41965757"],"is_preprint":false}],"current_model":"BTN3A2 is a primate-specific butyrophilin family transmembrane protein that forms a trimeric complex with BTN3A1 and BTN2A1; upon phosphoantigen (HMBPP) binding to BTN3A1/BTN2A1 intracellular B30.2 domains, BTN3A2 acts as a bona fide ligand for the Vγ9Vδ2 TCR (binding the Vδ2 chain apical surface) through a 'pliers-like' activation mechanism. Beyond immune surveillance, BTN3A2 interacts with neurexins to suppress excitatory synaptic transmission, interacts with ACE2 and SARS-CoV-2 Spike RBD to restrict viral infection by reducing ACE2 levels, interacts with MFGE8 to promote ferroptosis and inhibit angiogenesis, and in glioma is transcriptionally induced by HIF-1α and drives chemoresistance via the AKT/SP1/RAD51 DNA damage repair axis."},"narrative":{"mechanistic_narrative":"BTN3A2 is a butyrophilin-family transmembrane protein that functions as the antigen-presenting arm of a phosphoantigen-sensing complex and operates more broadly as a context-dependent regulator of cell-surface signaling and stress responses [PMID:bio_10.1101_2024.10.02.616253]. In Vγ9Vδ2 T-cell immune surveillance, BTN3A2 assembles into a full-length complex with BTN3A1 and BTN2A1; phosphoantigen (HMBPP) bridges the intracellular B30.2 domains of BTN3A1 and BTN2A1, and upon T-cell receptor engagement the BTN3A2–BTN2A1 ectodomain interaction dissociates so that BTN3A2 binds the apical surface of the Vδ2 chain, establishing it as a bona fide TCR ligand acting through a 'pliers-like gripping' activation mechanism [PMID:bio_10.1101_2024.10.02.616253]. Beyond immunity, BTN3A2 engages diverse cell-surface and secreted partners: it binds presynaptic neurexins and suppresses excitatory synaptic transmission onto hippocampal neurons [PMID:31133542]; it interacts with both ACE2 and the SARS-CoV-2 Spike receptor-binding domain and restricts viral attachment by lowering ACE2 levels [PMID:39142074]; and it binds MFGE8, downregulating it to promote hypoxia-induced ferroptosis and inhibit angiogenesis [PMID:40147528]. BTN3A2 is also a hypoxia-responsive gene directly activated by HIF-1α that drives temozolomide chemoresistance in glioma through an AKT/SP1/RAD51 DNA-damage-repair axis [PMID:41965757], and its expression supports gastric cancer cell proliferation, migration, and invasion [PMID:28246015].","teleology":[{"year":2017,"claim":"Established that BTN3A2 expression is functionally pro-tumorigenic and genetically regulated, addressing whether the locus contributes causally to cancer cell behavior rather than being a bystander.","evidence":"CRISPR/Cas9 deletion with proliferation/migration/invasion readouts plus enhancer reporter assay at rs1679709 in gastric cancer cells","pmids":["28246015"],"confidence":"Medium","gaps":["No molecular partner or signaling pathway linking BTN3A2 to the cancer phenotype identified","Single lab, gastric cancer only"]},{"year":2019,"claim":"Identified a non-immune neuronal role, showing BTN3A2 binds presynaptic neurexins and modulates synaptic transmission, expanding its function beyond the immune system.","evidence":"Hippocampal slice electrophysiology with BTN3A2 overexpression and cell-surface neurexin binding assay in rat","pmids":["31133542"],"confidence":"Medium","gaps":["Mechanism by which neurexin binding suppresses excitatory transmission unresolved","Endogenous loss-of-function not tested","Binding stoichiometry/affinity not defined"]},{"year":2024,"claim":"Defined an antiviral function, showing BTN3A2 binds both the SARS-CoV-2 Spike RBD and ACE2 and restricts infection by reducing ACE2 levels.","evidence":"Co-IP, biolayer interferometry, competition ELISA, flow cytometry in edited cell lines, and transgenic mice infected with live SARS-CoV-2","pmids":["39142074"],"confidence":"High","gaps":["Molecular basis of ACE2 downregulation (degradation vs. trafficking) not resolved","Whether antiviral activity generalizes beyond SARS-CoV-2 unknown"]},{"year":2024,"claim":"Resolved the structural mechanism of phosphoantigen sensing, confirming BTN3A2 as a direct Vγ9Vδ2 TCR ligand within the BTN3A1–BTN3A2–BTN2A1 complex.","evidence":"Cryo-EM structures of full-length complexes in primed and TCR-engaged states stabilized by HMBPP (preprint)","pmids":["bio_10.1101_2024.10.02.616253"],"confidence":"High","gaps":["Preprint, not peer-reviewed","Dynamics of the primed-to-engaged transition in cells not directly observed","Quantitative contribution of BTN3A2 vs BTN2A1 to TCR triggering not separated"]},{"year":2025,"claim":"Linked BTN3A2 to vascular biology, showing its interaction with MFGE8 drives hypoxia-induced ferroptosis and anti-angiogenic effects.","evidence":"Co-IP, siRNA knockdown and overexpression in HUVECs, and a rat preeclampsia model in vivo","pmids":["40147528"],"confidence":"Medium","gaps":["How BTN3A2 binding downregulates MFGE8 is undefined","Connection to ferroptosis machinery not mechanistically dissected","Single lab"]},{"year":2026,"claim":"Placed BTN3A2 within hypoxic transcriptional control and DNA-repair-mediated chemoresistance, identifying it as a HIF-1α target driving temozolomide resistance.","evidence":"RNA-seq, CUT&Tag, promoter luciferase, and lentiviral knockdown in glioma cells and in vivo TMZ sensitivity assays","pmids":["41965757"],"confidence":"Medium","gaps":["Mechanism connecting cell-surface BTN3A2 to intracellular AKT/SP1/RAD51 signaling unclear","Direct vs indirect activation of the AKT axis not established","Single lab, glioma only"]},{"year":null,"claim":"How a single butyrophilin reconciles its membrane-receptor functions (TCR ligand, neurexin/ACE2/MFGE8 binding) with intracellular signaling outputs (AKT/SP1/RAD51) remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No unifying mechanism links surface binding events to downstream intracellular pathways","Tissue-specific partner selection not understood","Physiological vs pathological roles not integrated"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[2]},{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[0]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1,2]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[2]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[1,3,5]}],"complexes":["BTN3A1-BTN3A2-BTN2A1 phosphoantigen-sensing complex"],"partners":["BTN3A1","BTN2A1","ACE2","MFGE8"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P78410","full_name":"Butyrophilin subfamily 3 member A2","aliases":[],"length_aa":334,"mass_kda":36.4,"function":"Plays a role in T-cell responses in the adaptive immune response. Inhibits the release of IFNG from activated T-cells","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/P78410/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/BTN3A2","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1165,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/BTN3A2","total_profiled":1310},"omim":[{"mim_id":"613595","title":"BUTYROPHILIN, SUBFAMILY 3, MEMBER A3; BTN3A3","url":"https://www.omim.org/entry/613595"},{"mim_id":"613594","title":"BUTYROPHILIN, SUBFAMILY 3, MEMBER A2; BTN3A2","url":"https://www.omim.org/entry/613594"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"lymphoid tissue","ntpm":83.3}],"url":"https://www.proteinatlas.org/search/BTN3A2"},"hgnc":{"alias_symbol":["BTN3.2"],"prev_symbol":[]},"alphafold":{"accession":"P78410","domains":[{"cath_id":"2.60.40.10","chopping":"30-144","consensus_level":"high","plddt":96.4578,"start":30,"end":144},{"cath_id":"2.60.40.10","chopping":"152-245","consensus_level":"high","plddt":90.5109,"start":152,"end":245}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P78410","model_url":"https://alphafold.ebi.ac.uk/files/AF-P78410-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P78410-F1-predicted_aligned_error_v6.png","plddt_mean":89.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=BTN3A2","jax_strain_url":"https://www.jax.org/strain/search?query=BTN3A2"},"sequence":{"accession":"P78410","fasta_url":"https://rest.uniprot.org/uniprotkb/P78410.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P78410/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P78410"}},"corpus_meta":[{"pmid":"28246015","id":"PMC_28246015","title":"Exome Array Analysis Identifies Variants in SPOCD1 and BTN3A2 That Affect Risk for Gastric Cancer.","date":"2017","source":"Gastroenterology","url":"https://pubmed.ncbi.nlm.nih.gov/28246015","citation_count":64,"is_preprint":false},{"pmid":"31133542","id":"PMC_31133542","title":"Identification of the primate-specific gene BTN3A2 as an additional schizophrenia risk gene in the MHC loci.","date":"2019","source":"EBioMedicine","url":"https://pubmed.ncbi.nlm.nih.gov/31133542","citation_count":35,"is_preprint":false},{"pmid":"28382515","id":"PMC_28382515","title":"Evolutionary and polymorphism analyses reveal the central role of BTN3A2 in the concerted evolution of the BTN3 gene family.","date":"2017","source":"Immunogenetics","url":"https://pubmed.ncbi.nlm.nih.gov/28382515","citation_count":22,"is_preprint":false},{"pmid":"36091044","id":"PMC_36091044","title":"Long noncoding RNA profiling reveals that LncRNA BTN3A2 inhibits the host inflammatory response to Eimeria tenella infection in chickens.","date":"2022","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/36091044","citation_count":12,"is_preprint":false},{"pmid":"39142074","id":"PMC_39142074","title":"Primate-specific BTN3A2 protects against SARS-CoV-2 infection by interacting with and reducing ACE2.","date":"2024","source":"EBioMedicine","url":"https://pubmed.ncbi.nlm.nih.gov/39142074","citation_count":2,"is_preprint":false},{"pmid":"40147528","id":"PMC_40147528","title":"BTN3A2 interacted with MFGE8 to alleviate preeclampsia by promoting ferroptosis and inhibiting angiogenesis.","date":"2025","source":"Life sciences","url":"https://pubmed.ncbi.nlm.nih.gov/40147528","citation_count":2,"is_preprint":false},{"pmid":"40775620","id":"PMC_40775620","title":"Decoding the epigenetic-immune nexus in hepatocellular carcinoma: a Mendelian randomization study reveals BTN3A2, S100A12 and TRIM27 as white blood cell regulators.","date":"2025","source":"BMC cancer","url":"https://pubmed.ncbi.nlm.nih.gov/40775620","citation_count":2,"is_preprint":false},{"pmid":"41965757","id":"PMC_41965757","title":"Hypoxia-induced BTN3A2 promotes glioma progression and chemoresistance via AKT/SP1/RAD51-mediated DNA damage.","date":"2026","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/41965757","citation_count":0,"is_preprint":false},{"pmid":"41006511","id":"PMC_41006511","title":"Multiomics Mendelian randomization integrating pQTL, eQTL and mQTL data revealed BTN3A2 as a potential drug target for nephrolithiasis.","date":"2025","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/41006511","citation_count":0,"is_preprint":false},{"pmid":"42062698","id":"PMC_42062698","title":"Integrated multi-dimensional analyses reveal a BTN3A2-centered diagnostic risk score and a monocyte-T cell axis as central drivers of dermatomyositis.","date":"2026","source":"Clinical rheumatology","url":"https://pubmed.ncbi.nlm.nih.gov/42062698","citation_count":0,"is_preprint":false},{"pmid":"41503897","id":"PMC_41503897","title":"DNA Methylation-mediated BTN3A2 Regulation via CD14+CD16+ Monocytes Protects Against Primary Sclerosing Cholangitis.","date":"2026","source":"Current topics in medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/41503897","citation_count":0,"is_preprint":false},{"pmid":"41980300","id":"PMC_41980300","title":"A chemiluminescent imaging immunosensor based on copper-doped NiFe PBA nanozyme for detection of BTN3A2: A candidate biomarker in early stage of gastric cancer.","date":"2026","source":"Biosensors & bioelectronics","url":"https://pubmed.ncbi.nlm.nih.gov/41980300","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.10.02.616253","title":"Cryo-EM structural insights into Vγ9Vδ2 TCR activation via multiple butyrophilins","date":"2024-10-03","source":"bioRxiv","url":"https://doi.org/10.1101/2024.10.02.616253","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9877,"output_tokens":1773,"usd":0.028113,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8612,"output_tokens":2631,"usd":0.054418,"stage2_stop_reason":"end_turn"},"total_usd":0.082531,"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\": 2019,\n      \"finding\": \"BTN3A2 overexpression specifically suppressed excitatory synaptic activity onto CA1 pyramidal neurons in rat hippocampal slices, and BTN3A2 was shown to interact with presynaptic adhesion molecules neurexins via cell surface binding assay.\",\n      \"method\": \"Electrophysiology (rat hippocampal slice overexpression), cell surface binding assay\",\n      \"journal\": \"EBioMedicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal methods (electrophysiology + binding assay) in a single lab establishing both functional effect and binding partner\",\n      \"pmids\": [\"31133542\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"BTN3A2 interacts with the receptor-binding domain (RBD) of the SARS-CoV-2 Spike protein and with ACE2, inhibiting SARS-CoV-2 attachment. BTN3A2 reduces ACE2 levels both in vitro and in vivo, thereby inhibiting ACE2-mediated viral infection.\",\n      \"method\": \"Immunoprecipitation, flow cytometry, biolayer interferometry, competition ELISA, BTN3A2-edited cell lines and transgenic mice infected with live SARS-CoV-2\",\n      \"journal\": \"EBioMedicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal biochemical methods (biolayer interferometry, competition ELISA, Co-IP) plus in vivo validation in transgenic mice with live virus\",\n      \"pmids\": [\"39142074\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Cryo-EM structures of the full-length BTN3A1–BTN3A2–BTN2A1 complex stabilized by the phosphoantigen HMBPP revealed that HMBPP bridges the intracellular B30.2 domains of BTN3A1 and BTN2A1, while BTN3A2 and BTN2A1 ectodomains associate in the primed complex. Upon Vγ9Vδ2 TCR engagement, the BTN3A2–BTN2A1 ectodomain interaction dissociates; BTN2A1 binds the lateral surface of the Vγ9 chain and BTN3A2 binds the apical surface of the Vδ2 chain, confirming BTN3A2 as a bona fide TCR ligand and revealing a 'pliers-like gripping' mechanism for TCR activation.\",\n      \"method\": \"Cryo-EM structural determination of full-length protein complexes, functional antibody complex structures\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structures of full-length complexes with multiple states (primed and TCR-engaged) providing atomic-level mechanistic insight\",\n      \"pmids\": [\"bio_10.1101_2024.10.02.616253\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Deletion of BTN3A2 inhibited proliferation, migration, and invasion of gastric cancer cells; a protective allele at rs1679709 reduced enhancer activity at this locus and decreased BTN3A2 expression.\",\n      \"method\": \"CRISPR/Cas9 gene deletion, reporter construct (enhancer activity assay), cell proliferation/migration/invasion assays\",\n      \"journal\": \"Gastroenterology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR KO with multiple cellular phenotype readouts plus reporter assay for regulatory mechanism, single lab\",\n      \"pmids\": [\"28246015\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"BTN3A2 physically interacts with MFGE8 (milk fat globule-EGF factor 8), and this interaction promotes hypoxia-induced ferroptosis in HUVECs by downregulating MFGE8, thereby inhibiting angiogenesis.\",\n      \"method\": \"Co-immunoprecipitation (BTN3A2–MFGE8 interaction), siRNA knockdown, overexpression in HUVECs, rat PE model in vivo\",\n      \"journal\": \"Life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP identifying binding partner plus functional knockdown/overexpression with defined phenotypic readouts and in vivo model, single lab\",\n      \"pmids\": [\"40147528\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"BTN3A2 is a hypoxia-responsive gene directly transcriptionally activated by HIF-1α, and BTN3A2 promotes chemoresistance in glioma by activating the AKT/SP1/RAD51 axis to enhance DNA damage repair capacity, thereby conferring temozolomide (TMZ) resistance.\",\n      \"method\": \"RNA-seq, CUT&Tag, promoter luciferase assay, lentivirus-mediated BTN3A2 knockdown in vitro and in vivo (TMZ sensitivity assay)\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (CUT&Tag chromatin profiling, luciferase, RNA-seq, in vivo KD) in a single lab establishing transcriptional mechanism and downstream pathway\",\n      \"pmids\": [\"41965757\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"BTN3A2 is a primate-specific butyrophilin family transmembrane protein that forms a trimeric complex with BTN3A1 and BTN2A1; upon phosphoantigen (HMBPP) binding to BTN3A1/BTN2A1 intracellular B30.2 domains, BTN3A2 acts as a bona fide ligand for the Vγ9Vδ2 TCR (binding the Vδ2 chain apical surface) through a 'pliers-like' activation mechanism. Beyond immune surveillance, BTN3A2 interacts with neurexins to suppress excitatory synaptic transmission, interacts with ACE2 and SARS-CoV-2 Spike RBD to restrict viral infection by reducing ACE2 levels, interacts with MFGE8 to promote ferroptosis and inhibit angiogenesis, and in glioma is transcriptionally induced by HIF-1α and drives chemoresistance via the AKT/SP1/RAD51 DNA damage repair axis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"BTN3A2 is a butyrophilin-family transmembrane protein that functions as the antigen-presenting arm of a phosphoantigen-sensing complex and operates more broadly as a context-dependent regulator of cell-surface signaling and stress responses [#2]. In Vγ9Vδ2 T-cell immune surveillance, BTN3A2 assembles into a full-length complex with BTN3A1 and BTN2A1; phosphoantigen (HMBPP) bridges the intracellular B30.2 domains of BTN3A1 and BTN2A1, and upon T-cell receptor engagement the BTN3A2–BTN2A1 ectodomain interaction dissociates so that BTN3A2 binds the apical surface of the Vδ2 chain, establishing it as a bona fide TCR ligand acting through a 'pliers-like gripping' activation mechanism [#2]. Beyond immunity, BTN3A2 engages diverse cell-surface and secreted partners: it binds presynaptic neurexins and suppresses excitatory synaptic transmission onto hippocampal neurons [#0]; it interacts with both ACE2 and the SARS-CoV-2 Spike receptor-binding domain and restricts viral attachment by lowering ACE2 levels [#1]; and it binds MFGE8, downregulating it to promote hypoxia-induced ferroptosis and inhibit angiogenesis [#4]. BTN3A2 is also a hypoxia-responsive gene directly activated by HIF-1α that drives temozolomide chemoresistance in glioma through an AKT/SP1/RAD51 DNA-damage-repair axis [#5], and its expression supports gastric cancer cell proliferation, migration, and invasion [#3].\",\n  \"teleology\": [\n    {\n      \"year\": 2017,\n      \"claim\": \"Established that BTN3A2 expression is functionally pro-tumorigenic and genetically regulated, addressing whether the locus contributes causally to cancer cell behavior rather than being a bystander.\",\n      \"evidence\": \"CRISPR/Cas9 deletion with proliferation/migration/invasion readouts plus enhancer reporter assay at rs1679709 in gastric cancer cells\",\n      \"pmids\": [\"28246015\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No molecular partner or signaling pathway linking BTN3A2 to the cancer phenotype identified\", \"Single lab, gastric cancer only\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identified a non-immune neuronal role, showing BTN3A2 binds presynaptic neurexins and modulates synaptic transmission, expanding its function beyond the immune system.\",\n      \"evidence\": \"Hippocampal slice electrophysiology with BTN3A2 overexpression and cell-surface neurexin binding assay in rat\",\n      \"pmids\": [\"31133542\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which neurexin binding suppresses excitatory transmission unresolved\", \"Endogenous loss-of-function not tested\", \"Binding stoichiometry/affinity not defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Defined an antiviral function, showing BTN3A2 binds both the SARS-CoV-2 Spike RBD and ACE2 and restricts infection by reducing ACE2 levels.\",\n      \"evidence\": \"Co-IP, biolayer interferometry, competition ELISA, flow cytometry in edited cell lines, and transgenic mice infected with live SARS-CoV-2\",\n      \"pmids\": [\"39142074\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of ACE2 downregulation (degradation vs. trafficking) not resolved\", \"Whether antiviral activity generalizes beyond SARS-CoV-2 unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Resolved the structural mechanism of phosphoantigen sensing, confirming BTN3A2 as a direct Vγ9Vδ2 TCR ligand within the BTN3A1–BTN3A2–BTN2A1 complex.\",\n      \"evidence\": \"Cryo-EM structures of full-length complexes in primed and TCR-engaged states stabilized by HMBPP (preprint)\",\n      \"pmids\": [\"bio_10.1101_2024.10.02.616253\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Preprint, not peer-reviewed\", \"Dynamics of the primed-to-engaged transition in cells not directly observed\", \"Quantitative contribution of BTN3A2 vs BTN2A1 to TCR triggering not separated\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Linked BTN3A2 to vascular biology, showing its interaction with MFGE8 drives hypoxia-induced ferroptosis and anti-angiogenic effects.\",\n      \"evidence\": \"Co-IP, siRNA knockdown and overexpression in HUVECs, and a rat preeclampsia model in vivo\",\n      \"pmids\": [\"40147528\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How BTN3A2 binding downregulates MFGE8 is undefined\", \"Connection to ferroptosis machinery not mechanistically dissected\", \"Single lab\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Placed BTN3A2 within hypoxic transcriptional control and DNA-repair-mediated chemoresistance, identifying it as a HIF-1α target driving temozolomide resistance.\",\n      \"evidence\": \"RNA-seq, CUT&Tag, promoter luciferase, and lentiviral knockdown in glioma cells and in vivo TMZ sensitivity assays\",\n      \"pmids\": [\"41965757\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism connecting cell-surface BTN3A2 to intracellular AKT/SP1/RAD51 signaling unclear\", \"Direct vs indirect activation of the AKT axis not established\", \"Single lab, glioma only\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a single butyrophilin reconciles its membrane-receptor functions (TCR ligand, neurexin/ACE2/MFGE8 binding) with intracellular signaling outputs (AKT/SP1/RAD51) remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No unifying mechanism links surface binding events to downstream intracellular pathways\", \"Tissue-specific partner selection not understood\", \"Physiological vs pathological roles not integrated\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1, 2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 3, 5]}\n    ],\n    \"complexes\": [\"BTN3A1-BTN3A2-BTN2A1 phosphoantigen-sensing complex\"],\n    \"partners\": [\"BTN3A1\", \"BTN2A1\", \"ACE2\", \"MFGE8\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":1,"faith_total":2,"faith_pct":50.0}}