{"gene":"BTN3A2","run_date":"2026-04-28T17:12:38","timeline":{"discoveries":[{"year":2019,"finding":"BTN3A2 overexpression in rat hippocampal slices specifically suppressed excitatory synaptic activity onto CA1 pyramidal neurons, most likely through its interaction with presynaptic adhesion molecules neurexins, as demonstrated by cell surface binding assay.","method":"Electrophysiological analysis of rat hippocampal slices with BTN3A2 overexpression; cell surface binding assay for BTN3A2-neurexin interaction","journal":"EBioMedicine","confidence":"Medium","confidence_rationale":"Tier 2 — direct electrophysiology and binding assay in single study, two orthogonal methods","pmids":["31133542"],"is_preprint":false},{"year":2017,"finding":"BTN3A2 deletion inhibited proliferation, migration, and invasion of gastric cancer cells, establishing a functional role in gastric carcinogenesis. Additionally, a haplotype at the BTN3A2 locus reduced enhancer activity to decrease BTN3A2 expression.","method":"CRISPR/Cas9 knockout in gastric cancer cell lines; reporter/enhancer assay; cell proliferation, migration, and invasion assays","journal":"Gastroenterology","confidence":"Medium","confidence_rationale":"Tier 2 — KO with defined cellular phenotype plus reporter assay, single study","pmids":["28246015"],"is_preprint":false},{"year":2024,"finding":"BTN3A2 interacts with the receptor-binding domain (RBD) of SARS-CoV-2 Spike protein and with ACE2, inhibiting SARS-CoV-2 attachment and reducing ACE2 levels in vitro and in vivo, thereby protecting against infection.","method":"Immunoprecipitation, flow cytometry, biolayer interferometry, competition ELISA, BTN3A2 gene-edited cell lines and transgenic mice infected with live SARS-CoV-2","journal":"EBioMedicine","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal biochemical assays plus in vivo validation in single study","pmids":["39142074"],"is_preprint":false},{"year":2025,"finding":"BTN3A2 interacts with MFGE8, and promotes hypoxia-induced ferroptosis in HUVECs by downregulating MFGE8, thereby inhibiting angiogenesis; BTN3A2 knockdown promoted placental angiogenesis and improved outcomes in a rat preeclampsia model.","method":"Co-immunoprecipitation (BTN3A2-MFGE8 interaction); siRNA knockdown; overexpression in HUVECs under hypoxia; rat PE model with BTN3A2 knockdown","journal":"Life sciences","confidence":"Medium","confidence_rationale":"Tier 2–3 — Co-IP for interaction, KD/OE with phenotypic readout in vitro and in vivo, single study","pmids":["40147528"],"is_preprint":false},{"year":2026,"finding":"BTN3A2 is transcriptionally activated by HIF-1α in glioma under hypoxia (identified by CUT&Tag and promoter luciferase assay), and enhances DNA damage repair through activation of the AKT/SP1/RAD51 axis, contributing to temozolomide resistance; BTN3A2 knockdown reduces proliferation, migration, invasion, and increases TMZ sensitivity in vitro and in vivo.","method":"CUT&Tag, promoter luciferase assay, RNA-seq, lentivirus-mediated BTN3A2 knockdown, in vitro and in vivo functional assays","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods (CUT&Tag, luciferase, RNA-seq, in vivo KD) in single study","pmids":["41965757"],"is_preprint":false},{"year":2024,"finding":"Cryo-EM structures reveal BTN3A2 forms a full-length complex with BTN3A1 and BTN2A1, stabilized by phosphoantigen HMBPP that bridges the intracellular B30.2 domains of BTN3A1 and BTN2A1. The ectodomain of BTN3A2 associates with BTN2A1 in the resting state; upon Vγ9Vδ2 TCR engagement, the BTN3A2–BTN2A1 ectodomain interaction dissociates, allowing BTN2A1 to bind the Vγ9 chain while BTN3A2 binds the apical surface of the Vδ2 chain, demonstrating BTN3A2 as a bona fide TCR ligand via a 'pliers-like gripping' mechanism.","method":"Cryo-EM structural determination of full-length BTN3A1-BTN3A2-BTN2A1 complex and TCR-engaged complex; structural analysis of functional antibody complexes","journal":"bioRxiv","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structures with functional validation of TCR engagement mechanism","pmids":["bio_10.1101_2024.10.02.616253"],"is_preprint":true}],"current_model":"BTN3A2 is a primate-specific butyrophilin that functions as a direct Vγ9Vδ2 TCR ligand within a BTN3A1-BTN3A2-BTN2A1 complex activated by phosphoantigens, suppresses excitatory synaptic activity via neurexin interactions, protects against SARS-CoV-2 by interacting with Spike RBD and reducing ACE2, promotes ferroptosis and inhibits angiogenesis through interaction with MFGE8, and drives glioma chemoresistance via a HIF-1α-activated AKT/SP1/RAD51 DNA repair axis."},"narrative":{"teleology":[{"year":2017,"claim":"Establishing that BTN3A2 has a functional role in epithelial cancer biology: CRISPR knockout demonstrated that BTN3A2 loss inhibits gastric cancer cell proliferation, migration, and invasion, while a regulatory haplotype modulates its expression through enhancer activity.","evidence":"CRISPR/Cas9 knockout in gastric cancer cell lines with proliferation/migration/invasion assays and reporter/enhancer assay","pmids":["28246015"],"confidence":"Medium","gaps":["Mechanism by which BTN3A2 promotes proliferation and invasion not defined","No signaling pathway downstream of BTN3A2 identified in this cancer context","Single study without independent replication"]},{"year":2019,"claim":"Revealing a neuronal function: BTN3A2 suppresses excitatory synaptic activity onto hippocampal CA1 pyramidal neurons through interaction with presynaptic neurexins, establishing a trans-synaptic adhesion role.","evidence":"Electrophysiology in rat hippocampal slices with BTN3A2 overexpression; cell surface binding assay for neurexin interaction","pmids":["31133542"],"confidence":"Medium","gaps":["Specific neurexin isoform(s) mediating the interaction not mapped","Mechanism connecting neurexin binding to synaptic suppression not resolved","No loss-of-function validation in neurons"]},{"year":2024,"claim":"Demonstrating antiviral function: BTN3A2 directly binds SARS-CoV-2 Spike RBD and ACE2, competitively inhibiting viral attachment and reducing ACE2 surface levels, protecting against infection both in vitro and in vivo.","evidence":"Immunoprecipitation, biolayer interferometry, competition ELISA, BTN3A2 gene-edited cells, and transgenic mice infected with live SARS-CoV-2","pmids":["39142074"],"confidence":"High","gaps":["Structural basis of the BTN3A2–RBD and BTN3A2–ACE2 interactions not determined","Whether BTN3A2 restricts other coronaviruses is unknown","Mechanism of ACE2 downregulation not fully elucidated"]},{"year":2024,"claim":"Resolving the structural mechanism of phosphoantigen-dependent γδ T cell activation: cryo-EM showed BTN3A2 forms a resting-state complex with BTN3A1 and BTN2A1 where BTN3A2 ectodomains associate with BTN2A1; phosphoantigen binding triggers dissociation, allowing BTN3A2 to directly engage the Vδ2 TCR chain as a bona fide ligand.","evidence":"Cryo-EM structures of full-length BTN3A1–BTN3A2–BTN2A1 complex in resting and TCR-engaged states (preprint)","pmids":["bio_10.1101_2024.10.02.616253"],"confidence":"High","gaps":["Preprint awaiting peer review","Kinetics of the conformational switch from resting to engaged state not measured","Relative contributions of BTN3A2 versus BTN2A1 ectodomains to TCR activation affinity not quantified"]},{"year":2025,"claim":"Linking BTN3A2 to vascular biology: BTN3A2 interacts with MFGE8 and promotes hypoxia-induced ferroptosis in endothelial cells by downregulating MFGE8, inhibiting angiogenesis; knockdown in a rat preeclampsia model improved placental angiogenesis.","evidence":"Co-immunoprecipitation for BTN3A2–MFGE8; siRNA knockdown and overexpression in HUVECs under hypoxia; rat preeclampsia model","pmids":["40147528"],"confidence":"Medium","gaps":["Mechanism by which BTN3A2 downregulates MFGE8 (degradation vs. transcriptional) not defined","Single study without independent confirmation of MFGE8 interaction","Ferroptosis pathway components directly engaged by BTN3A2 not identified"]},{"year":2026,"claim":"Defining a chemoresistance mechanism in glioma: HIF-1α directly activates BTN3A2 transcription under hypoxia, and BTN3A2 enhances DNA damage repair through the AKT/SP1/RAD51 axis, conferring temozolomide resistance.","evidence":"CUT&Tag, promoter luciferase assay, RNA-seq, lentiviral BTN3A2 knockdown with in vitro and in vivo functional assays","pmids":["41965757"],"confidence":"Medium","gaps":["Direct physical interaction between BTN3A2 and AKT pathway components not demonstrated","Whether AKT/SP1/RAD51 axis activation is specific to glioma or generalizable is unknown","Single study; independent replication needed"]},{"year":null,"claim":"A unifying mechanism explaining how a single transmembrane butyrophilin mediates such diverse functions — immune TCR engagement, synaptic modulation, antiviral defense, ferroptosis regulation, and DNA repair — remains unresolved, particularly whether these reflect context-dependent interactions of the same ectodomain or distinct signaling through the intracellular domain.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structure–function mapping linking specific BTN3A2 domains to non-immune functions","Relative physiological importance of immune versus non-immune roles in vivo unknown","No interactome study comprehensively cataloguing BTN3A2 binding partners across tissues"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[0,5]},{"term_id":"GO:0001618","term_label":"virus receptor activity","supporting_discovery_ids":[2]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,2,5]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[5]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[4]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[3]}],"complexes":["BTN3A1–BTN3A2–BTN2A1"],"partners":["BTN3A1","BTN2A1","NRXN1","ACE2","MFGE8"],"other_free_text":[]},"mechanistic_narrative":"BTN3A2 is a butyrophilin family member that functions as a direct Vγ9Vδ2 T cell receptor ligand within a trimeric BTN3A1–BTN3A2–BTN2A1 complex; upon phosphoantigen-driven activation, the BTN3A2–BTN2A1 ectodomain interaction dissociates, enabling BTN3A2 to engage the Vδ2 chain via a pliers-like gripping mechanism [PMID:bio_10.1101_2024.10.02.616253]. Beyond immune recognition, BTN3A2 interacts with the SARS-CoV-2 Spike receptor-binding domain and reduces ACE2 levels, protecting against viral infection in vitro and in transgenic mice [PMID:39142074]. BTN3A2 also modulates excitatory synaptic transmission through interaction with neurexins [PMID:31133542], promotes hypoxia-induced ferroptosis by downregulating MFGE8 to inhibit angiogenesis [PMID:40147528], and drives glioma temozolomide resistance via a HIF-1α–activated AKT/SP1/RAD51 DNA repair axis [PMID:41965757]."},"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":63,"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":34,"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":11,"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":"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":1,"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":1,"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":"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":"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":8282,"output_tokens":1669,"usd":0.024941},"stage2":{"model":"claude-opus-4-6","input_tokens":4927,"output_tokens":2232,"usd":0.120652},"total_usd":0.145593,"stage1_batch_id":"msgbatch_01TqNM6p6FsoMBT2jzQTwKBr","stage2_batch_id":"msgbatch_01Ya473eco8sTHbvRymQaU8o","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2019,\n      \"finding\": \"BTN3A2 overexpression in rat hippocampal slices specifically suppressed excitatory synaptic activity onto CA1 pyramidal neurons, most likely through its interaction with presynaptic adhesion molecules neurexins, as demonstrated by cell surface binding assay.\",\n      \"method\": \"Electrophysiological analysis of rat hippocampal slices with BTN3A2 overexpression; cell surface binding assay for BTN3A2-neurexin interaction\",\n      \"journal\": \"EBioMedicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct electrophysiology and binding assay in single study, two orthogonal methods\",\n      \"pmids\": [\"31133542\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"BTN3A2 deletion inhibited proliferation, migration, and invasion of gastric cancer cells, establishing a functional role in gastric carcinogenesis. Additionally, a haplotype at the BTN3A2 locus reduced enhancer activity to decrease BTN3A2 expression.\",\n      \"method\": \"CRISPR/Cas9 knockout in gastric cancer cell lines; reporter/enhancer assay; cell proliferation, migration, and invasion assays\",\n      \"journal\": \"Gastroenterology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO with defined cellular phenotype plus reporter assay, single study\",\n      \"pmids\": [\"28246015\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"BTN3A2 interacts with the receptor-binding domain (RBD) of SARS-CoV-2 Spike protein and with ACE2, inhibiting SARS-CoV-2 attachment and reducing ACE2 levels in vitro and in vivo, thereby protecting against infection.\",\n      \"method\": \"Immunoprecipitation, flow cytometry, biolayer interferometry, competition ELISA, BTN3A2 gene-edited cell lines and transgenic mice infected with live SARS-CoV-2\",\n      \"journal\": \"EBioMedicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal biochemical assays plus in vivo validation in single study\",\n      \"pmids\": [\"39142074\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"BTN3A2 interacts with MFGE8, and promotes hypoxia-induced ferroptosis in HUVECs by downregulating MFGE8, thereby inhibiting angiogenesis; BTN3A2 knockdown promoted placental angiogenesis and improved outcomes in a rat preeclampsia model.\",\n      \"method\": \"Co-immunoprecipitation (BTN3A2-MFGE8 interaction); siRNA knockdown; overexpression in HUVECs under hypoxia; rat PE model with BTN3A2 knockdown\",\n      \"journal\": \"Life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — Co-IP for interaction, KD/OE with phenotypic readout in vitro and in vivo, single study\",\n      \"pmids\": [\"40147528\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"BTN3A2 is transcriptionally activated by HIF-1α in glioma under hypoxia (identified by CUT&Tag and promoter luciferase assay), and enhances DNA damage repair through activation of the AKT/SP1/RAD51 axis, contributing to temozolomide resistance; BTN3A2 knockdown reduces proliferation, migration, invasion, and increases TMZ sensitivity in vitro and in vivo.\",\n      \"method\": \"CUT&Tag, promoter luciferase assay, RNA-seq, lentivirus-mediated BTN3A2 knockdown, in vitro and in vivo functional assays\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (CUT&Tag, luciferase, RNA-seq, in vivo KD) in single study\",\n      \"pmids\": [\"41965757\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Cryo-EM structures reveal BTN3A2 forms a full-length complex with BTN3A1 and BTN2A1, stabilized by phosphoantigen HMBPP that bridges the intracellular B30.2 domains of BTN3A1 and BTN2A1. The ectodomain of BTN3A2 associates with BTN2A1 in the resting state; upon Vγ9Vδ2 TCR engagement, the BTN3A2–BTN2A1 ectodomain interaction dissociates, allowing BTN2A1 to bind the Vγ9 chain while BTN3A2 binds the apical surface of the Vδ2 chain, demonstrating BTN3A2 as a bona fide TCR ligand via a 'pliers-like gripping' mechanism.\",\n      \"method\": \"Cryo-EM structural determination of full-length BTN3A1-BTN3A2-BTN2A1 complex and TCR-engaged complex; structural analysis of functional antibody complexes\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structures with functional validation of TCR engagement mechanism\",\n      \"pmids\": [\"bio_10.1101_2024.10.02.616253\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"BTN3A2 is a primate-specific butyrophilin that functions as a direct Vγ9Vδ2 TCR ligand within a BTN3A1-BTN3A2-BTN2A1 complex activated by phosphoantigens, suppresses excitatory synaptic activity via neurexin interactions, protects against SARS-CoV-2 by interacting with Spike RBD and reducing ACE2, promotes ferroptosis and inhibits angiogenesis through interaction with MFGE8, and drives glioma chemoresistance via a HIF-1α-activated AKT/SP1/RAD51 DNA repair axis.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"BTN3A2 is a butyrophilin family member that functions as a direct Vγ9Vδ2 T cell receptor ligand within a trimeric BTN3A1–BTN3A2–BTN2A1 complex; upon phosphoantigen-driven activation, the BTN3A2–BTN2A1 ectodomain interaction dissociates, enabling BTN3A2 to engage the Vδ2 chain via a pliers-like gripping mechanism [PMID:bio_10.1101_2024.10.02.616253]. Beyond immune recognition, BTN3A2 interacts with the SARS-CoV-2 Spike receptor-binding domain and reduces ACE2 levels, protecting against viral infection in vitro and in transgenic mice [PMID:39142074]. BTN3A2 also modulates excitatory synaptic transmission through interaction with neurexins [PMID:31133542], promotes hypoxia-induced ferroptosis by downregulating MFGE8 to inhibit angiogenesis [PMID:40147528], and drives glioma temozolomide resistance via a HIF-1α–activated AKT/SP1/RAD51 DNA repair axis [PMID:41965757].\",\n  \"teleology\": [\n    {\n      \"year\": 2017,\n      \"claim\": \"Establishing that BTN3A2 has a functional role in epithelial cancer biology: CRISPR knockout demonstrated that BTN3A2 loss inhibits gastric cancer cell proliferation, migration, and invasion, while a regulatory haplotype modulates its expression through enhancer activity.\",\n      \"evidence\": \"CRISPR/Cas9 knockout in gastric cancer cell lines with proliferation/migration/invasion assays and reporter/enhancer assay\",\n      \"pmids\": [\"28246015\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism by which BTN3A2 promotes proliferation and invasion not defined\",\n        \"No signaling pathway downstream of BTN3A2 identified in this cancer context\",\n        \"Single study without independent replication\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Revealing a neuronal function: BTN3A2 suppresses excitatory synaptic activity onto hippocampal CA1 pyramidal neurons through interaction with presynaptic neurexins, establishing a trans-synaptic adhesion role.\",\n      \"evidence\": \"Electrophysiology in rat hippocampal slices with BTN3A2 overexpression; cell surface binding assay for neurexin interaction\",\n      \"pmids\": [\"31133542\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Specific neurexin isoform(s) mediating the interaction not mapped\",\n        \"Mechanism connecting neurexin binding to synaptic suppression not resolved\",\n        \"No loss-of-function validation in neurons\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstrating antiviral function: BTN3A2 directly binds SARS-CoV-2 Spike RBD and ACE2, competitively inhibiting viral attachment and reducing ACE2 surface levels, protecting against infection both in vitro and in vivo.\",\n      \"evidence\": \"Immunoprecipitation, biolayer interferometry, competition ELISA, BTN3A2 gene-edited cells, and transgenic mice infected with live SARS-CoV-2\",\n      \"pmids\": [\"39142074\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of the BTN3A2–RBD and BTN3A2–ACE2 interactions not determined\",\n        \"Whether BTN3A2 restricts other coronaviruses is unknown\",\n        \"Mechanism of ACE2 downregulation not fully elucidated\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Resolving the structural mechanism of phosphoantigen-dependent γδ T cell activation: cryo-EM showed BTN3A2 forms a resting-state complex with BTN3A1 and BTN2A1 where BTN3A2 ectodomains associate with BTN2A1; phosphoantigen binding triggers dissociation, allowing BTN3A2 to directly engage the Vδ2 TCR chain as a bona fide ligand.\",\n      \"evidence\": \"Cryo-EM structures of full-length BTN3A1–BTN3A2–BTN2A1 complex in resting and TCR-engaged states (preprint)\",\n      \"pmids\": [\"bio_10.1101_2024.10.02.616253\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Preprint awaiting peer review\",\n        \"Kinetics of the conformational switch from resting to engaged state not measured\",\n        \"Relative contributions of BTN3A2 versus BTN2A1 ectodomains to TCR activation affinity not quantified\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Linking BTN3A2 to vascular biology: BTN3A2 interacts with MFGE8 and promotes hypoxia-induced ferroptosis in endothelial cells by downregulating MFGE8, inhibiting angiogenesis; knockdown in a rat preeclampsia model improved placental angiogenesis.\",\n      \"evidence\": \"Co-immunoprecipitation for BTN3A2–MFGE8; siRNA knockdown and overexpression in HUVECs under hypoxia; rat preeclampsia model\",\n      \"pmids\": [\"40147528\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism by which BTN3A2 downregulates MFGE8 (degradation vs. transcriptional) not defined\",\n        \"Single study without independent confirmation of MFGE8 interaction\",\n        \"Ferroptosis pathway components directly engaged by BTN3A2 not identified\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Defining a chemoresistance mechanism in glioma: HIF-1α directly activates BTN3A2 transcription under hypoxia, and BTN3A2 enhances DNA damage repair through the AKT/SP1/RAD51 axis, conferring temozolomide resistance.\",\n      \"evidence\": \"CUT&Tag, promoter luciferase assay, RNA-seq, lentiviral BTN3A2 knockdown with in vitro and in vivo functional assays\",\n      \"pmids\": [\"41965757\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct physical interaction between BTN3A2 and AKT pathway components not demonstrated\",\n        \"Whether AKT/SP1/RAD51 axis activation is specific to glioma or generalizable is unknown\",\n        \"Single study; independent replication needed\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A unifying mechanism explaining how a single transmembrane butyrophilin mediates such diverse functions — immune TCR engagement, synaptic modulation, antiviral defense, ferroptosis regulation, and DNA repair — remains unresolved, particularly whether these reflect context-dependent interactions of the same ectodomain or distinct signaling through the intracellular domain.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No structure–function mapping linking specific BTN3A2 domains to non-immune functions\",\n        \"Relative physiological importance of immune versus non-immune roles in vivo unknown\",\n        \"No interactome study comprehensively cataloguing BTN3A2 binding partners across tissues\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"GO:0001618\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 2, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"complexes\": [\n      \"BTN3A1–BTN3A2–BTN2A1\"\n    ],\n    \"partners\": [\n      \"BTN3A1\",\n      \"BTN2A1\",\n      \"NRXN1\",\n      \"ACE2\",\n      \"MFGE8\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}