{"gene":"BTN3A1","run_date":"2026-06-09T22:02:45","timeline":{"discoveries":[{"year":2012,"finding":"BTN3A1 (CD277) is required for phosphoantigen (PAg)-induced Vγ9Vδ2 T cell activation; CD277 knockdown and domain-shuffling confirmed the BTN3A1 isoform is specifically implicated. FRAP experiments showed that intracellular PAg accumulation decreases BTN3A1 membrane mobility, linking PAg sensing to altered membrane dynamics.","method":"CD277 knockdown, domain-shuffling, FRAP, antibody agonist/antagonist functional assays","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (KD, domain-shuffling, FRAP, functional antibody experiments) in a single rigorous study, widely cited and consistent with subsequent literature","pmids":["22767497"],"is_preprint":false},{"year":2012,"finding":"The three BTN3A isoforms (BTN3A1, BTN3A2, BTN3A3) exist as V-shaped homodimers in solution, associating through the membrane-proximal C-type Ig domain. The agonist antibody 20.1 and antagonist antibody 103.2 bind separate epitopes on the BTN3A Ig-V domain with high affinity but different valencies. BTN3A1 is necessary for Vγ9Vδ2 T cell activation.","method":"X-ray crystallography, structural studies, antibody binding assays, functional T cell activation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure combined with functional binding assays; single lab but multiple orthogonal methods","pmids":["22846996"],"is_preprint":false},{"year":2015,"finding":"Phosphoantigens bind directly to the intracellular B30.2 domain of BTN3A1: microbial HMBPP binds with affinity ~1.1 µM and endogenous IPP at ~627 µM. The plakin family member periplakin interacts with a membrane-proximal di-leucine motif in the BTN3A1 cytoplasmic tail; this interaction is functionally required for γδ T cell activation (re-expression of BTN3A1 lacking the periplakin binding motif fails to restore responses).","method":"In vitro binding assay (B30.2 domain), yeast two-hybrid, co-IP, knockdown/re-expression rescue, functional T cell activation assays","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct biochemical binding assay for pAg affinity combined with yeast two-hybrid, functional rescue experiments; replicated by subsequent structural studies","pmids":["25637025"],"is_preprint":false},{"year":2017,"finding":"Phosphoantigen binding to the intracellular B30.2 domain of BTN3A1 induces a global conformational change in that domain, as characterized by NMR and MD simulations. Two distinct dimer interfaces in the full-length intracellular domain are near the pAg-binding pocket. The extracellular domains of BTN3A1 adopt a V-shaped conformation at rest; locking them in this conformation (without perturbing membrane reorganization) diminishes pAg-induced T cell activation.","method":"NMR spectroscopy, X-ray crystallography, molecular dynamics simulations, biochemical assays, cellular T cell activation assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR + crystallography + MD + functional cellular validation; multiple orthogonal methods in one rigorous study","pmids":["28807997"],"is_preprint":false},{"year":2017,"finding":"The BTN3A1 B30.2 domain binds phosphoantigens and various negatively charged small molecules in a positively charged surface pocket. BTN3A1 discriminates phosphoantigens from non-antigenic small molecules by their ability to induce a specific conformational change propagating from the pAg binding site to distal parts of the domain, acting as a conformational antigenic sensor.","method":"NMR chemical shift perturbation, X-ray crystallography","journal":"ACS chemical biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR and X-ray crystallography with mechanistic interpretation; single lab with two orthogonal structural methods","pmids":["28862425"],"is_preprint":false},{"year":2017,"finding":"The juxtamembrane domain of BTN3A1 is required for correct pAg-induced Vγ9Vδ2 T cell activation; mutations in the juxtamembrane domain (but not the transmembrane domain) markedly enhanced or reduced γδ T cell reactivity. A juxtamembrane region identified as a possible dimerization interface proximal to the B30.2 domain is particularly important.","method":"Domain mutagenesis, functional T cell activation assays","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function mutagenesis with defined cellular phenotype; single lab, two complementary approaches (enhancement and reduction mutations)","pmids":["28461569"],"is_preprint":false},{"year":2016,"finding":"BTN3A1 acts as a positive regulator of nucleic acid-mediated type I interferon signaling. In the resting state, BTN3A1 is constitutively associated with TBK1. Upon nucleic acid stimulation, the BTN3A1-TBK1 complex redistributes to the perinuclear region where BTN3A1 mediates the interaction between TBK1 and IRF3, leading to IRF3 phosphorylation. Microtubule-associated protein MAP4 controls dynein-dependent transport of BTN3A1 to the perinuclear region in response to nucleic acid stimulation.","method":"Co-immunoprecipitation, knockdown (BTN3A1 and MAP4), subcellular fractionation/localization, IFN-β reporter assays, immunofluorescence","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP showing constitutive BTN3A1-TBK1 complex, KD with defined IRF3 phosphorylation and IFN-β phenotype, localization data tied to function; multiple orthogonal methods in one study","pmids":["27911820"],"is_preprint":false},{"year":2014,"finding":"BTN3A1 expression alone is sufficient for activation of Vγ9Vδ2 T cells by the agonist antibody 20.1, but PAg-mediated Vγ9Vδ2 T cell activation requires BTN3A1 plus additional gene(s) on human chromosome 6.","method":"Genetic complementation — BTN3A1 transduction into CHO cells vs. CHO cells containing entire human chromosome 6; Vγ9Vδ2 TCR transductant activation assays","journal":"European journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — clean epistasis experiment distinguishing antibody- vs. PAg-mediated activation with genetic complementation; replicated across multiple TCR transductants","pmids":["24890657"],"is_preprint":false},{"year":2016,"finding":"Internalization of HMBPP into target cells is required for BTN3A1-dependent lysis by Vγ9Vδ2 effector T cells (pretreatment at 4°C decreased HMBPP-induced lysis). A cell-permeable prodrug that bypasses energy-dependent uptake restores BTN3A1-dependent lysis, supporting an inside-out model of T cell triggering by intracellular BTN3A1.","method":"Cytotoxicity assays, temperature-dependent uptake experiments, BTN3A1 disruption, prodrug/compound comparison","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional mechanistic dissection with multiple conditions; single lab, two complementary approaches (temperature block and prodrug)","pmids":["27271567"],"is_preprint":false},{"year":2019,"finding":"Site-directed mutagenesis of BTN3A1 B30.2 domain identified H381 as critical for ligand binding (mutation fully blocks binding), while mutations to charged surface residues impacted diphosphate interactions. Monophosphonate analogs bind similarly to BTN3A1 but differ in antigenicity, demonstrating that BTN3A1 binding and T cell activation efficacy are not linearly correlated.","method":"Site-directed mutagenesis, fluorescence polarization binding assay, T cell proliferation and IFN-γ assays, molecular docking","journal":"Journal of medicinal chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — mutagenesis with in vitro binding assay; single lab with biochemical and cellular validation","pmids":["31268699"],"is_preprint":false},{"year":2020,"finding":"BTN3A1 on tumor cells inhibits tumor-reactive αβ T cell receptor activation by preventing segregation of N-glycosylated CD45 from the immune synapse. CD277-specific antibodies restore αβ T cell effector activity and elicit BTN2A1-dependent γδ lymphocyte cytotoxicity against BTN3A1+ cancer cells.","method":"In vitro co-culture T cell activation assays, immune synapse imaging, BTN3A1 expression manipulation, in vivo tumor models","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 / Strong — mechanistic finding linking BTN3A1 to CD45 segregation at immune synapse with multiple functional readouts, replicated in vivo; published in Science with broad methods","pmids":["32820120"],"is_preprint":false},{"year":2022,"finding":"BTN3A1 promotes radioresistance in esophageal squamous cell carcinoma by activating ULK1-mediated autophagy; BTN3A1 interacts with ULK1 (identified by immunoprecipitation and mass spectrometry) and promotes ULK1 phosphorylation to initiate autophagy. HIF-1α directly promotes BTN3A1 transcription upon irradiation (confirmed by ChIP and luciferase reporter assay).","method":"Immunoprecipitation, mass spectrometry, western blotting, ChIP, luciferase reporter assay, KD/OE in vitro and in vivo","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP/MS identifies ULK1 interaction, ChIP/luciferase confirms HIF-1α-BTN3A1 transcriptional axis; single lab, multiple orthogonal methods","pmids":["36418890"],"is_preprint":false},{"year":2020,"finding":"NLRC5 promotes transcription of BTN3A1-3 genes through an atypical regulatory motif in their promoters. Forced NLRC5 expression promoted Vγ9Vδ2 T cell-mediated killing of tumor cells in a BTN3A-dependent manner.","method":"Promoter reporter assays, gene expression manipulation (OE/KD), T cell cytotoxicity assays, correlation analysis in primary cells","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — promoter regulatory motif validated with functional BTN3A-dependent rescue; single lab, promoter reporter plus functional assay","pmids":["33364588"],"is_preprint":false},{"year":2011,"finding":"T cells express all three BTN3/CD277 isoforms, whereas NK cells express mostly BTN3A2 (which lacks the B30.2 intracellular domain). BTN3A1 triggering on T cells enhances TCR-induced signaling; however, BTN3A1 triggering does not affect NK cell activation, while specific engagement of BTN3A2 (but not BTN3A1) decreases NKp30-induced cytokine production.","method":"Isoform-specific expression analysis, functional antibody triggering assays, cytokine/proliferation measurements, TCR signaling assays","journal":"European journal of immunology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — functional co-stimulation assays with isoform-specific context; single lab, multiple functional readouts","pmids":["21918970"],"is_preprint":false},{"year":2023,"finding":"HMBPP binds to the B30.2 domain of BTN3A1 but not to BTN2A1 (confirmed by 31P-NMR, abrogating signals from both phosphorus atoms upon BTN3A1 binding). The BTN2A1 B30.2 domain forms a homodimer; mutation L325G (but not L318G) both prevents BTN2A1 internal domain homodimerization and blocks its binding to HMBPP-bound BTN3A1 (measured by ITC), identifying a cytoplasmic BTN2A1-BTN3A1/HMBPP complex.","method":"31P-NMR, size exclusion chromatography, NMR, isothermal titration calorimetry (ITC), site-directed mutagenesis, functional T cell ELISA assays","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR directly shows HMBPP binds BTN3A1 not BTN2A1; ITC measures BTN2A1-BTN3A1/HMBPP complex; mutagenesis validates functional importance; multiple orthogonal methods in one study","pmids":["37171180"],"is_preprint":false},{"year":2025,"finding":"19F NMR of specific BTN3A1 point mutants (W421C, T449C, T506C) showed these residues are conformationally influenced by HMBPP and BTN2A1 association. W421 is at the BTN2A1 binding interface (19F labeling of W421C reduces BTN2A1 binding affinity). T506 is distal from the pAg binding site, indicating a larger conformational change in the B30.2 domain upon HMBPP and BTN2A1 binding. Juxtamembrane residues T304C and G323C are unaffected, localizing changes to the B30.2 domain.","method":"19F solution NMR, site-directed mutagenesis, binding affinity measurements","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — 19F NMR with point mutants directly maps conformational changes; single lab, single method type but mechanistically detailed","pmids":["40079188"],"is_preprint":false},{"year":2024,"finding":"Cryo-EM structures show that HMBPP bridges the intracellular B30.2 domains of BTN3A1 and BTN2A1 within the full-length BTN3A1-BTN3A2-BTN2A1 complex. Upon Vγ9Vδ2 TCR engagement, BTN3A2-BTN2A1 ectodomain interaction dissociates: BTN2A1 binds the lateral surface of the Vγ9 chain and BTN3A2 binds the apical surface of the Vδ2 chain, suggesting a 'pliers-like gripping' mechanism for TCR activation.","method":"Cryo-electron microscopy (cryo-EM) structural determination of full-length complexes","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — high-quality structural data (cryo-EM), but preprint not yet peer-reviewed; single study","pmids":["bio_10.1101_2024.10.02.616253"],"is_preprint":true},{"year":2024,"finding":"BTN3A1 expressed on cervical cancer cells promotes Vγ9Vδ2 T cell exhaustion by engaging γδ TCRs and upregulating transcription factors NR4A2/3 downstream of TCR signaling. Blocking TCR or knocking down NR4A2/3 reverses BTN3A1-induced T cell exhaustion. IFN-γ secreted by Vδ2 T cells in turn promotes BTN3A1 and PD-L1 expression on tumor cells (a feedback loop).","method":"BTN3A1 KO/OE in tumor cell lines, co-culture with Vδ2 T cells, flow cytometry, RNA-seq, Western blot, gene knockdown","journal":"Cell communication and signaling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO/OE with defined TCR-signaling/NR4A2/3 pathway placement and rescue experiment; single lab, multiple methods","pmids":["39342337"],"is_preprint":false},{"year":2025,"finding":"ICT01 (agonist antibody targeting BTN3A extracellular domain) binds to a unique region in the BTN3A extracellular domain, destabilizes the BTN2A1-BTN3A interface, and facilitates Vγ9Vδ2 TCR engagement, resulting in γδ T cell activation independently of phosphoantigens.","method":"Structural analysis, biochemical assays, cellular T cell activation assays","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 1 / Weak — preprint; structural + biochemical + cellular methods described but not yet peer-reviewed; single study","pmids":["bio_10.1101_2025.10.21.681109"],"is_preprint":true},{"year":2024,"finding":"Full activation of Vγ9Vδ2 TCR requires phosphorylation of juxtamembrane (JTM) amino acids of BTN3A1, leading to activating heterodimerization of BTN2A1 and BTN3A1 at the cell surface. Single oncogenic mutations in cells upregulate surface BTN2A1 and enable Vγ9Vδ2 TCR binding, but full T cell activation additionally requires BTN3A1 JTM phosphorylation-dependent heterodimerization. PHLDB2, SYNJ2, and CARMIL1 were identified as key regulators of this surface heterodimerization.","method":"Step-wise mutagenesis organoid/cell models, surface BTN2A1/3A1 expression analysis, protein interactome mapping, in vitro and in vivo T cell activation assays","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 2 / Weak — preprint; mechanistic pathway placement with interactome data, but not yet peer-reviewed; single study","pmids":["bio_10.1101_2024.11.19.624272"],"is_preprint":true}],"current_model":"BTN3A1 is a type-1 transmembrane protein that acts as an intracellular phosphoantigen (pAg) sensor through its B30.2 domain (directly binding HMBPP and IPP), undergoes a conformational change upon pAg binding that propagates through the protein, forms a cytoplasmic complex with BTN2A1 (bridged by HMBPP) and associates with BTN3A2 extracellularly, reorganizes at the plasma membrane to engage the Vγ9Vδ2 TCR (with BTN2A1 contacting the Vγ9 chain and BTN3A2 the Vδ2 chain) via an inside-out signaling mechanism requiring its juxtamembrane and periplakin-binding domains; additionally, BTN3A1 inhibits αβ T cell activation by preventing CD45 exclusion from the immune synapse, constitutively associates with TBK1 and mediates dynein/MAP4-dependent perinuclear redistribution to facilitate TBK1-IRF3 phosphorylation in innate antiviral signaling, and in cancer cells interacts with ULK1 to promote autophagy-mediated radioresistance downstream of HIF-1α."},"narrative":{"mechanistic_narrative":"BTN3A1 (CD277) is a type-I transmembrane butyrophilin that operates as an intracellular phosphoantigen (pAg) sensor required for activation of Vγ9Vδ2 T cells [PMID:22767497, PMID:22846996]. Sensing occurs through its cytoplasmic B30.2 domain, which directly binds pAgs in a positively charged surface pocket—microbial HMBPP with high affinity and endogenous IPP with lower affinity—and discriminates antigenic from non-antigenic phosphometabolites by their ability to trigger a conformational change that propagates from the binding pocket to distal regions of the domain [PMID:25637025, PMID:28807997, PMID:28862425]. pAg binding does not act alone: HMBPP bridges the B30.2 domain of BTN3A1 to that of BTN2A1, forming a cytoplasmic BTN2A1–BTN3A1 complex within a larger BTN3A1–BTN3A2–BTN2A1 assembly, and these intracellular events are relayed to the cell surface through the BTN3A1 juxtamembrane region and a membrane-proximal di-leucine motif that recruits periplakin, both of which are required for T cell triggering [PMID:37171180, PMID:25637025, PMID:28461569]. Surface signal output requires reorganization of the extracellular V-shaped homodimers and juxtamembrane phosphorylation-dependent BTN2A1–BTN3A1 heterodimerization, with BTN2A1 and BTN3A2 ectodomains engaging distinct surfaces of the Vγ9Vδ2 TCR in an inside-out 'gripping' mechanism [PMID:28807997, PMID:bio_10.1101_2024.10.02.616253]. Beyond γδ T cell triggering, BTN3A1 on tumor cells suppresses αβ T cell activation by preventing exclusion of N-glycosylated CD45 from the immune synapse [PMID:32820120], acts as a positive regulator of nucleic-acid-induced type I interferon signaling by constitutively associating with TBK1 and undergoing dynein/MAP4-dependent perinuclear redistribution to promote TBK1–IRF3 phosphorylation [PMID:27911820], and is transcriptionally induced by HIF-1α to drive ULK1-mediated autophagy and radioresistance in esophageal carcinoma [PMID:36418890]. Its transcription is controlled by NLRC5 and HIF-1α [PMID:33364588, PMID:36418890].","teleology":[{"year":2012,"claim":"Established that the BTN3A1 isoform specifically, not other CD277 isoforms, is the molecule required for phosphoantigen-induced Vγ9Vδ2 T cell activation, and linked pAg sensing to changes in BTN3A1 membrane behavior.","evidence":"CD277 knockdown, domain-shuffling, FRAP, and functional agonist/antagonist antibody assays","pmids":["22767497"],"confidence":"High","gaps":["Did not identify where pAg binds within BTN3A1","Did not resolve the molecular link between altered membrane mobility and TCR engagement"]},{"year":2012,"claim":"Defined the resting architecture of BTN3A as V-shaped homodimers associating through their membrane-proximal Ig domains, and localized agonist/antagonist antibody epitopes to the Ig-V domain.","evidence":"X-ray crystallography and antibody binding plus functional T cell assays","pmids":["22846996"],"confidence":"High","gaps":["Did not address how ectodomain conformation couples to intracellular sensing","No structure of the full-length receptor or its partners"]},{"year":2014,"claim":"Distinguished antibody-mediated from pAg-mediated activation, showing BTN3A1 alone suffices for agonist-antibody triggering but pAg sensing requires additional chromosome-6-encoded gene(s).","evidence":"Genetic complementation comparing BTN3A1-transduced CHO cells with cells carrying human chromosome 6, across multiple TCR transductants","pmids":["24890657"],"confidence":"High","gaps":["The required cofactor gene(s) on chromosome 6 were not identified here"]},{"year":2015,"claim":"Provided the direct biochemical basis for sensing by showing pAgs bind the intracellular B30.2 domain and identifying periplakin as a cytoplasmic-tail partner functionally required for γδ activation.","evidence":"In vitro B30.2 binding assays, yeast two-hybrid, co-IP, and knockdown/re-expression rescue with functional T cell assays","pmids":["25637025"],"confidence":"High","gaps":["Did not show how B30.2 occupancy is transmitted to the membrane or to the TCR","Mechanistic role of periplakin beyond binding not resolved"]},{"year":2016,"claim":"Revealed a distinct innate-immune function: BTN3A1 constitutively binds TBK1 and undergoes MAP4/dynein-dependent perinuclear relocation to bridge TBK1–IRF3 and drive type I interferon signaling.","evidence":"Reciprocal co-IP, BTN3A1 and MAP4 knockdown, subcellular fractionation/immunofluorescence, and IFN-β reporter assays","pmids":["27911820"],"confidence":"High","gaps":["How nucleic-acid sensing triggers BTN3A1 redistribution is unresolved","Relationship between this innate role and pAg sensing is not addressed"]},{"year":2016,"claim":"Supported the inside-out model by demonstrating that intracellular delivery of HMBPP into target cells is required for BTN3A1-dependent lysis.","evidence":"Cytotoxicity assays with temperature-dependent uptake block and a cell-permeable prodrug bypass","pmids":["27271567"],"confidence":"Medium","gaps":["Indirect inference of intracellular sensing from uptake manipulation","Did not directly visualize intracellular pAg-BTN3A1 engagement"]},{"year":2017,"claim":"Defined the sensing mechanism as conformational: pAg binding induces a global B30.2 conformational change, and locking the ectodomain V-shape blunts activation, tying intracellular sensing to extracellular reorganization.","evidence":"NMR, X-ray crystallography, MD simulations, and cellular T cell activation assays (two studies)","pmids":["28807997","28862425"],"confidence":"High","gaps":["How the B30.2 conformational change propagates across the membrane was not established","Identity of the surface partner transmitting the signal not yet known"]},{"year":2017,"claim":"Identified the juxtamembrane domain as a critical transmission element, with mutations bidirectionally tuning γδ T cell reactivity.","evidence":"Domain mutagenesis with functional T cell activation assays","pmids":["28461569"],"confidence":"Medium","gaps":["The interacting partner at the juxtamembrane interface was not defined here","Single-lab mutagenesis without structural confirmation of the proposed dimerization interface"]},{"year":2019,"claim":"Mapped B30.2 ligand-binding determinants (notably H381) and showed that binding affinity and antigenic potency are not linearly correlated, reinforcing the conformational-sensor model.","evidence":"Site-directed mutagenesis, fluorescence-polarization binding, T cell proliferation/IFN-γ assays, and docking","pmids":["31268699"],"confidence":"Medium","gaps":["Did not resolve what distinguishes activating from non-activating bound conformations structurally"]},{"year":2020,"claim":"Uncovered a tumor-immunosuppressive function whereby BTN3A1 inhibits αβ TCR activation by preventing CD45 segregation from the immune synapse, while anti-CD277 restores αβ responses and elicits BTN2A1-dependent γδ cytotoxicity.","evidence":"Co-culture T cell assays, immune synapse imaging, BTN3A1 expression manipulation, and in vivo tumor models","pmids":["32820120"],"confidence":"High","gaps":["Molecular basis of CD45 retention by BTN3A1 not detailed","Relationship to the γδ-activating function in the same synapse not fully integrated"]},{"year":2020,"claim":"Placed BTN3A transcription downstream of NLRC5, linking antigen-presentation regulation to γδ-mediated tumor killing.","evidence":"Promoter reporter assays, NLRC5 OE/KD, and BTN3A-dependent T cell cytotoxicity assays","pmids":["33364588"],"confidence":"Medium","gaps":["The atypical promoter motif's direct occupancy mechanism not biochemically resolved"]},{"year":2022,"claim":"Identified a cancer-intrinsic role in which HIF-1α-induced BTN3A1 binds ULK1 and promotes its phosphorylation to drive autophagy-mediated radioresistance.","evidence":"Co-IP/mass spectrometry, ChIP, luciferase reporter, and KD/OE in vitro and in vivo in esophageal carcinoma","pmids":["36418890"],"confidence":"Medium","gaps":["Whether BTN3A1 directly catalyzes or scaffolds ULK1 phosphorylation is unclear","Relationship to BTN3A1's immune functions not addressed"]},{"year":2023,"claim":"Demonstrated the molecular partnership underlying pAg relay: HMBPP binds BTN3A1 (not BTN2A1) and bridges a cytoplasmic BTN2A1–BTN3A1 complex dependent on BTN2A1 B30.2 homodimerization.","evidence":"31P-NMR, NMR, ITC, size-exclusion chromatography, and mutagenesis (L325G) with functional T cell ELISA","pmids":["37171180"],"confidence":"High","gaps":["Stoichiometry within the full receptor assembly not resolved here","How the cytoplasmic complex couples to surface TCR engagement not shown"]},{"year":2024,"claim":"Linked surface heterodimerization to activation, showing that juxtamembrane phosphorylation of BTN3A1 drives BTN2A1–BTN3A1 surface heterodimerization required for full Vγ9Vδ2 TCR activation, and identified PHLDB2, SYNJ2, and CARMIL1 as regulators.","evidence":"Step-wise mutagenesis organoid/cell models, surface expression analysis, interactome mapping, and T cell assays (preprint)","pmids":["bio_10.1101_2024.11.19.624272"],"confidence":"Low","gaps":["Preprint, not yet peer-reviewed","The responsible juxtamembrane kinase is not identified","Mechanistic roles of PHLDB2/SYNJ2/CARMIL1 not defined"]},{"year":2024,"claim":"Provided structural integration of the full pathway, showing HMBPP-bridged intracellular B30.2 contacts and a 'pliers-like' ectodomain rearrangement engaging the Vγ9Vδ2 TCR.","evidence":"Cryo-EM of full-length BTN3A1–BTN3A2–BTN2A1 complexes (preprint)","pmids":["bio_10.1101_2024.10.02.616253"],"confidence":"Medium","gaps":["Preprint, not yet peer-reviewed","Dynamics of the inside-out transition between resting and engaged states not captured"]},{"year":2024,"claim":"Extended the tumor-immune role by showing tumor BTN3A1 drives Vγ9Vδ2 T cell exhaustion via TCR-dependent NR4A2/3 induction within an IFN-γ feedback loop upregulating BTN3A1 and PD-L1.","evidence":"BTN3A1 KO/OE in tumor lines, co-culture with Vδ2 T cells, RNA-seq, flow cytometry, and NR4A2/3 knockdown rescue","pmids":["39342337"],"confidence":"Medium","gaps":["Causal contribution of the IFN-γ feedback loop in vivo not fully established","Generalizability beyond cervical cancer not tested"]},{"year":2025,"claim":"Refined the conformational map, using 19F NMR to localize HMBPP/BTN2A1-induced changes to the B30.2 domain and to a BTN2A1-binding interface residue (W421), while juxtamembrane residues remain unaffected.","evidence":"19F solution NMR of point mutants with binding affinity measurements","pmids":["40079188"],"confidence":"Medium","gaps":["Single method type","How the larger B30.2 conformational change is mechanically transmitted not resolved"]},{"year":null,"claim":"It remains unresolved how the intracellular B30.2 conformational change and BTN2A1 complex are mechanically transduced across the membrane to drive surface heterodimerization, and which kinase phosphorylates the BTN3A1 juxtamembrane region.","evidence":"","pmids":[],"confidence":"Low","gaps":["No identified juxtamembrane kinase","No peer-reviewed full-length structure of resting versus TCR-engaged states","Integration of BTN3A1's γδ-sensing, αβ-suppressive, interferon, and autophagy roles is incomplete"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[2,3,4,14]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[2,4]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,16]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[6,11]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1,16]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[2,6,14]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,6,10]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[6,13,17]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[11]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[10,11,17]}],"complexes":["BTN3A1-BTN3A2-BTN2A1 receptor complex"],"partners":["BTN2A1","BTN3A2","PERIPLAKIN","TBK1","MAP4","ULK1","IRF3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O00481","full_name":"Butyrophilin subfamily 3 member A1","aliases":[],"length_aa":513,"mass_kda":57.7,"function":"Plays a role in T-cell activation and in the adaptive immune response. Regulates the proliferation of activated T-cells. Regulates the release of cytokines and IFNG by activated T-cells. Mediates the response of T-cells toward infected and transformed cells that are characterized by high levels of phosphorylated metabolites, such as isopentenyl pyrophosphate","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/O00481/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/BTN3A1","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/BTN3A1","total_profiled":1310},"omim":[{"mim_id":"613595","title":"BUTYROPHILIN, SUBFAMILY 3, MEMBER A3; BTN3A3","url":"https://www.omim.org/entry/613595"},{"mim_id":"613593","title":"BUTYROPHILIN, SUBFAMILY 3, MEMBER A1; BTN3A1","url":"https://www.omim.org/entry/613593"},{"mim_id":"613590","title":"BUTYROPHILIN, SUBFAMILY 2, MEMBER A1; BTN2A1","url":"https://www.omim.org/entry/613590"},{"mim_id":"191390","title":"INFLAMMATORY BOWEL DISEASE 11; IBD11","url":"https://www.omim.org/entry/191390"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Uncertain","locations":[{"location":"Vesicles","reliability":"Uncertain"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/BTN3A1"},"hgnc":{"alias_symbol":["BT3.1","BTF5","CD277","BTN3.1"],"prev_symbol":[]},"alphafold":{"accession":"O00481","domains":[{"cath_id":"2.60.40.10","chopping":"33-145","consensus_level":"high","plddt":95.3199,"start":33,"end":145},{"cath_id":"2.60.40.10","chopping":"152-241","consensus_level":"high","plddt":89.9124,"start":152,"end":241},{"cath_id":"2.60.120.920","chopping":"327-512","consensus_level":"high","plddt":95.7384,"start":327,"end":512},{"cath_id":"1.20.5","chopping":"247-322","consensus_level":"high","plddt":73.2692,"start":247,"end":322}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O00481","model_url":"https://alphafold.ebi.ac.uk/files/AF-O00481-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O00481-F1-predicted_aligned_error_v6.png","plddt_mean":89.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=BTN3A1","jax_strain_url":"https://www.jax.org/strain/search?query=BTN3A1"},"sequence":{"accession":"O00481","fasta_url":"https://rest.uniprot.org/uniprotkb/O00481.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O00481/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O00481"}},"corpus_meta":[{"pmid":"22767497","id":"PMC_22767497","title":"Key implication of CD277/butyrophilin-3 (BTN3A) in cellular stress sensing by a major human γδ T-cell subset.","date":"2012","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/22767497","citation_count":484,"is_preprint":false},{"pmid":"22846996","id":"PMC_22846996","title":"The molecular basis for modulation of human Vγ9Vδ2 T cell responses by CD277/butyrophilin-3 (BTN3A)-specific antibodies.","date":"2012","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22846996","citation_count":147,"is_preprint":false},{"pmid":"32820120","id":"PMC_32820120","title":"BTN3A1 governs antitumor responses by coordinating αβ and γδ T cells.","date":"2020","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/32820120","citation_count":131,"is_preprint":false},{"pmid":"25637025","id":"PMC_25637025","title":"Activation of human γδ T cells by cytosolic interactions of BTN3A1 with soluble phosphoantigens and the cytoskeletal adaptor periplakin.","date":"2015","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/25637025","citation_count":128,"is_preprint":false},{"pmid":"28807997","id":"PMC_28807997","title":"Phosphoantigen-induced conformational change of butyrophilin 3A1 (BTN3A1) and its implication on Vγ9Vδ2 T cell activation.","date":"2017","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/28807997","citation_count":105,"is_preprint":false},{"pmid":"24890657","id":"PMC_24890657","title":"Vγ9Vδ2 TCR-activation by phosphorylated antigens requires butyrophilin 3 A1 (BTN3A1) and additional genes on human chromosome 6.","date":"2014","source":"European journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/24890657","citation_count":71,"is_preprint":false},{"pmid":"21918970","id":"PMC_21918970","title":"Differential role for CD277 as a co-regulator of the immune signal in T and NK cells.","date":"2011","source":"European journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/21918970","citation_count":70,"is_preprint":false},{"pmid":"33178494","id":"PMC_33178494","title":"Baseline plasma levels of soluble PD-1, PD-L1, and BTN3A1 predict response to nivolumab treatment in patients with metastatic renal cell carcinoma: a step toward a biomarker for therapeutic decisions.","date":"2020","source":"Oncoimmunology","url":"https://pubmed.ncbi.nlm.nih.gov/33178494","citation_count":61,"is_preprint":false},{"pmid":"28862425","id":"PMC_28862425","title":"BTN3A1 Discriminates γδ T Cell Phosphoantigens from Nonantigenic Small Molecules via a Conformational Sensor in Its B30.2 Domain.","date":"2017","source":"ACS chemical biology","url":"https://pubmed.ncbi.nlm.nih.gov/28862425","citation_count":59,"is_preprint":false},{"pmid":"28386905","id":"PMC_28386905","title":"Butyrophilin 3A (BTN3A, CD277)-specific antibody 20.1 differentially activates Vγ9Vδ2 TCR clonotypes and interferes with phosphoantigen activation.","date":"2017","source":"European journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/28386905","citation_count":53,"is_preprint":false},{"pmid":"27619996","id":"PMC_27619996","title":"Butyrophilin 3A/CD277-Dependent Activation of Human γδ T Cells: Accessory Cell Capacity of Distinct Leukocyte Populations.","date":"2016","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/27619996","citation_count":42,"is_preprint":false},{"pmid":"27271567","id":"PMC_27271567","title":"HMBPP Analog Prodrugs Bypass Energy-Dependent Uptake To Promote Efficient BTN3A1-Mediated Malignant Cell Lysis by Vγ9Vδ2 T Lymphocyte Effectors.","date":"2016","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/27271567","citation_count":41,"is_preprint":false},{"pmid":"28461569","id":"PMC_28461569","title":"The Juxtamembrane Domain of Butyrophilin BTN3A1 Controls Phosphoantigen-Mediated Activation of Human Vγ9Vδ2 T Cells.","date":"2017","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/28461569","citation_count":39,"is_preprint":false},{"pmid":"27911820","id":"PMC_27911820","title":"MAP4-regulated dynein-dependent trafficking of BTN3A1 controls the TBK1-IRF3 signaling axis.","date":"2016","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/27911820","citation_count":29,"is_preprint":false},{"pmid":"36418890","id":"PMC_36418890","title":"BTN3A1 promotes tumor progression and radiation resistance in esophageal squamous cell carcinoma by regulating ULK1-mediated autophagy.","date":"2022","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/36418890","citation_count":23,"is_preprint":false},{"pmid":"36288286","id":"PMC_36288286","title":"Up-regulation of BTN3A1 on CD14+ cells promotes Vγ9Vδ2 T cell activation in psoriasis.","date":"2022","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/36288286","citation_count":23,"is_preprint":false},{"pmid":"33364588","id":"PMC_33364588","title":"NLRC5 promotes transcription of BTN3A1-3 genes and Vγ9Vδ2 T cell-mediated killing.","date":"2020","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/33364588","citation_count":23,"is_preprint":false},{"pmid":"36096643","id":"PMC_36096643","title":"Cutting Edge: Bispecific γδ T Cell Engager Containing Heterodimeric BTN2A1 and BTN3A1 Promotes Targeted Activation of Vγ9Vδ2+ T Cells in the Presence of Costimulation by CD28 or NKG2D.","date":"2022","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/36096643","citation_count":22,"is_preprint":false},{"pmid":"34293829","id":"PMC_34293829","title":"Comprehensive analysis of BTN3A1 in cancers: mining of omics data and validation in patient samples and cellular models.","date":"2021","source":"FEBS open bio","url":"https://pubmed.ncbi.nlm.nih.gov/34293829","citation_count":20,"is_preprint":false},{"pmid":"29670629","id":"PMC_29670629","title":"Regulation of Human γδ T Cells by BTN3A1 Protein Stability and ATP-Binding Cassette Transporters.","date":"2018","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/29670629","citation_count":18,"is_preprint":false},{"pmid":"29937767","id":"PMC_29937767","title":"ABCA1, apoA-I, and BTN3A1: A Legitimate Ménage à Trois in Dendritic Cells.","date":"2018","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/29937767","citation_count":17,"is_preprint":false},{"pmid":"34240204","id":"PMC_34240204","title":"Long noncoding RNA HOXA-AS2 accelerates cervical cancer by the miR-509-3p/BTN3A1 axis.","date":"2021","source":"The Journal of pharmacy and pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/34240204","citation_count":14,"is_preprint":false},{"pmid":"31268699","id":"PMC_31268699","title":"Probing the Ligand-Binding Pocket of BTN3A1.","date":"2019","source":"Journal of medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/31268699","citation_count":11,"is_preprint":false},{"pmid":"39342337","id":"PMC_39342337","title":"BTN3A1 expressed in cervical cancer cells promotes Vγ9Vδ2 T cells exhaustion through upregulating transcription factors NR4A2/3 downstream of TCR signaling.","date":"2024","source":"Cell communication and signaling : CCS","url":"https://pubmed.ncbi.nlm.nih.gov/39342337","citation_count":10,"is_preprint":false},{"pmid":"37171180","id":"PMC_37171180","title":"Mutations to the BTN2A1 Linker Region Impact Its Homodimerization and Its Cytoplasmic Interaction with Phospho-Antigen-Bound BTN3A1.","date":"2023","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/37171180","citation_count":9,"is_preprint":false},{"pmid":"35178171","id":"PMC_35178171","title":"Synthesis and Metabolism of BTN3A1 Ligands: Studies on Diene Modifications to the Phosphoantigen Scaffold.","date":"2022","source":"ACS medicinal chemistry letters","url":"https://pubmed.ncbi.nlm.nih.gov/35178171","citation_count":8,"is_preprint":false},{"pmid":"35920929","id":"PMC_35920929","title":"CD277 agonist enhances the immunogenicity of relapsed/refractory acute myeloid leukemia towards Vδ2+ T cell cytotoxicity.","date":"2022","source":"Annals of hematology","url":"https://pubmed.ncbi.nlm.nih.gov/35920929","citation_count":7,"is_preprint":false},{"pmid":"37688767","id":"PMC_37688767","title":"Synergistic effects of BTN3A1, SHP2, CD274, and STAT3 gene polymorphisms on the risk of systemic lupus erythematosus: a multifactorial dimensional reduction analysis.","date":"2023","source":"Clinical rheumatology","url":"https://pubmed.ncbi.nlm.nih.gov/37688767","citation_count":5,"is_preprint":false},{"pmid":"34545848","id":"PMC_34545848","title":"Elevated Expressions of BTN3A1 and RhoB in Psoriasis Vulgaris Lesions by an Immunohistochemical Study.","date":"2022","source":"Applied immunohistochemistry & molecular morphology : AIMM","url":"https://pubmed.ncbi.nlm.nih.gov/34545848","citation_count":5,"is_preprint":false},{"pmid":"40091603","id":"PMC_40091603","title":"Autologous Peripheral Vγ9Vδ2 T Cell Synergizes with αβ T Cell Through Antigen Presentation and BTN3A1 Blockade in Immunotherapy of Cervical Cancer.","date":"2025","source":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/40091603","citation_count":4,"is_preprint":false},{"pmid":"28631855","id":"PMC_28631855","title":"A Photo-Crosslinkable Biotin Derivative of the Phosphoantigen (E)-4-Hydroxy-3-Methylbut-2-Enyl Diphosphate (HMBPP) Activates Vγ9Vδ2 T Cells and Binds to the HMBPP Site of BTN3A1.","date":"2017","source":"Chemistry (Weinheim an der Bergstrasse, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/28631855","citation_count":4,"is_preprint":false},{"pmid":"28597565","id":"PMC_28597565","title":"BTN3A1-antibodies and phosphoantigens: TCRVγ9Vδ2 \"see\" the difference.","date":"2017","source":"European journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/28597565","citation_count":2,"is_preprint":false},{"pmid":"41226733","id":"PMC_41226733","title":"BTN2A1 and BTN3A1 as Novel Coeliac Disease Risk Loci: An In Silico Analysis.","date":"2025","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/41226733","citation_count":2,"is_preprint":false},{"pmid":"32958123","id":"PMC_32958123","title":"[Butyrophilin 3A1 (BTN3A1) enhances activation and proliferation of human peripheral blood Vγ9Vδ2 T cells induced by MTB-HAg].","date":"2020","source":"Xi bao yu fen zi mian yi xue za zhi = Chinese journal of cellular and molecular immunology","url":"https://pubmed.ncbi.nlm.nih.gov/32958123","citation_count":2,"is_preprint":false},{"pmid":"39417845","id":"PMC_39417845","title":"A regulatory variant rs9379874 in T1D risk region 6p22.2 affects BTN3A1 expression regulating T cell function.","date":"2024","source":"Acta diabetologica","url":"https://pubmed.ncbi.nlm.nih.gov/39417845","citation_count":1,"is_preprint":false},{"pmid":"39919440","id":"PMC_39919440","title":"Synthesis and evaluation of triazole-containing aryl/acyloxy prodrugs of a BTN3A1 ligand.","date":"2025","source":"European journal of medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/39919440","citation_count":0,"is_preprint":false},{"pmid":"42248853","id":"PMC_42248853","title":"Metformin sensitizes esophageal squamous cell carcinoma to Vγ9Vδ2 T cell-mediated cytotoxicity by upregulating BTN3A1 and BTN2A1.","date":"2026","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/42248853","citation_count":0,"is_preprint":false},{"pmid":"40079188","id":"PMC_40079188","title":"Investigation of structural and dynamic properties of the Butyrophilin BTN3A1/BTN2A1 cytoplasmic complex by 19F solution NMR.","date":"2025","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/40079188","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.10.21.681109","title":"Molecular Mechanisms Underlying Human Vγ9Vδ2 T Cell Activation by Butyrophilin-3 (BTN3) Targeted Antibodies","date":"2025-10-21","source":"bioRxiv","url":"https://doi.org/10.1101/2025.10.21.681109","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.06.12.659293","title":"The early human interferon gamma response to  <i>Toxoplasma gondii</i>  is driven by Vγ9Vδ2 T-cell sensing of host phosphoantigens and subsequent NK-cell activation","date":"2025-06-17","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.12.659293","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.11.19.624272","title":"Sensitivity to Vγ9Vδ2TCR T cells is imprinted after single mutations during early oncogenesis","date":"2024-11-21","source":"bioRxiv","url":"https://doi.org/10.1101/2024.11.19.624272","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.07.01.662467","title":"STELLA: Towards a Biomedical World Model with Self-Evolving Multimodal Agents","date":"2025-07-05","source":"bioRxiv","url":"https://doi.org/10.1101/2025.07.01.662467","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.05.05.652251","title":"γδ T Cells Target and Ablate Senescent Cells in Aging and Alleviate Pulmonary Fibrosis","date":"2025-05-09","source":"bioRxiv","url":"https://doi.org/10.1101/2025.05.05.652251","citation_count":0,"is_preprint":true},{"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":25990,"output_tokens":5656,"usd":0.081405,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":14089,"output_tokens":5560,"usd":0.104722,"stage2_stop_reason":"end_turn"},"total_usd":0.186127,"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\": 2012,\n      \"finding\": \"BTN3A1 (CD277) is required for phosphoantigen (PAg)-induced Vγ9Vδ2 T cell activation; CD277 knockdown and domain-shuffling confirmed the BTN3A1 isoform is specifically implicated. FRAP experiments showed that intracellular PAg accumulation decreases BTN3A1 membrane mobility, linking PAg sensing to altered membrane dynamics.\",\n      \"method\": \"CD277 knockdown, domain-shuffling, FRAP, antibody agonist/antagonist functional assays\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (KD, domain-shuffling, FRAP, functional antibody experiments) in a single rigorous study, widely cited and consistent with subsequent literature\",\n      \"pmids\": [\"22767497\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The three BTN3A isoforms (BTN3A1, BTN3A2, BTN3A3) exist as V-shaped homodimers in solution, associating through the membrane-proximal C-type Ig domain. The agonist antibody 20.1 and antagonist antibody 103.2 bind separate epitopes on the BTN3A Ig-V domain with high affinity but different valencies. BTN3A1 is necessary for Vγ9Vδ2 T cell activation.\",\n      \"method\": \"X-ray crystallography, structural studies, antibody binding assays, functional T cell activation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure combined with functional binding assays; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"22846996\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Phosphoantigens bind directly to the intracellular B30.2 domain of BTN3A1: microbial HMBPP binds with affinity ~1.1 µM and endogenous IPP at ~627 µM. The plakin family member periplakin interacts with a membrane-proximal di-leucine motif in the BTN3A1 cytoplasmic tail; this interaction is functionally required for γδ T cell activation (re-expression of BTN3A1 lacking the periplakin binding motif fails to restore responses).\",\n      \"method\": \"In vitro binding assay (B30.2 domain), yeast two-hybrid, co-IP, knockdown/re-expression rescue, functional T cell activation assays\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct biochemical binding assay for pAg affinity combined with yeast two-hybrid, functional rescue experiments; replicated by subsequent structural studies\",\n      \"pmids\": [\"25637025\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Phosphoantigen binding to the intracellular B30.2 domain of BTN3A1 induces a global conformational change in that domain, as characterized by NMR and MD simulations. Two distinct dimer interfaces in the full-length intracellular domain are near the pAg-binding pocket. The extracellular domains of BTN3A1 adopt a V-shaped conformation at rest; locking them in this conformation (without perturbing membrane reorganization) diminishes pAg-induced T cell activation.\",\n      \"method\": \"NMR spectroscopy, X-ray crystallography, molecular dynamics simulations, biochemical assays, cellular T cell activation assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR + crystallography + MD + functional cellular validation; multiple orthogonal methods in one rigorous study\",\n      \"pmids\": [\"28807997\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The BTN3A1 B30.2 domain binds phosphoantigens and various negatively charged small molecules in a positively charged surface pocket. BTN3A1 discriminates phosphoantigens from non-antigenic small molecules by their ability to induce a specific conformational change propagating from the pAg binding site to distal parts of the domain, acting as a conformational antigenic sensor.\",\n      \"method\": \"NMR chemical shift perturbation, X-ray crystallography\",\n      \"journal\": \"ACS chemical biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR and X-ray crystallography with mechanistic interpretation; single lab with two orthogonal structural methods\",\n      \"pmids\": [\"28862425\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The juxtamembrane domain of BTN3A1 is required for correct pAg-induced Vγ9Vδ2 T cell activation; mutations in the juxtamembrane domain (but not the transmembrane domain) markedly enhanced or reduced γδ T cell reactivity. A juxtamembrane region identified as a possible dimerization interface proximal to the B30.2 domain is particularly important.\",\n      \"method\": \"Domain mutagenesis, functional T cell activation assays\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function mutagenesis with defined cellular phenotype; single lab, two complementary approaches (enhancement and reduction mutations)\",\n      \"pmids\": [\"28461569\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"BTN3A1 acts as a positive regulator of nucleic acid-mediated type I interferon signaling. In the resting state, BTN3A1 is constitutively associated with TBK1. Upon nucleic acid stimulation, the BTN3A1-TBK1 complex redistributes to the perinuclear region where BTN3A1 mediates the interaction between TBK1 and IRF3, leading to IRF3 phosphorylation. Microtubule-associated protein MAP4 controls dynein-dependent transport of BTN3A1 to the perinuclear region in response to nucleic acid stimulation.\",\n      \"method\": \"Co-immunoprecipitation, knockdown (BTN3A1 and MAP4), subcellular fractionation/localization, IFN-β reporter assays, immunofluorescence\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP showing constitutive BTN3A1-TBK1 complex, KD with defined IRF3 phosphorylation and IFN-β phenotype, localization data tied to function; multiple orthogonal methods in one study\",\n      \"pmids\": [\"27911820\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"BTN3A1 expression alone is sufficient for activation of Vγ9Vδ2 T cells by the agonist antibody 20.1, but PAg-mediated Vγ9Vδ2 T cell activation requires BTN3A1 plus additional gene(s) on human chromosome 6.\",\n      \"method\": \"Genetic complementation — BTN3A1 transduction into CHO cells vs. CHO cells containing entire human chromosome 6; Vγ9Vδ2 TCR transductant activation assays\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean epistasis experiment distinguishing antibody- vs. PAg-mediated activation with genetic complementation; replicated across multiple TCR transductants\",\n      \"pmids\": [\"24890657\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Internalization of HMBPP into target cells is required for BTN3A1-dependent lysis by Vγ9Vδ2 effector T cells (pretreatment at 4°C decreased HMBPP-induced lysis). A cell-permeable prodrug that bypasses energy-dependent uptake restores BTN3A1-dependent lysis, supporting an inside-out model of T cell triggering by intracellular BTN3A1.\",\n      \"method\": \"Cytotoxicity assays, temperature-dependent uptake experiments, BTN3A1 disruption, prodrug/compound comparison\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional mechanistic dissection with multiple conditions; single lab, two complementary approaches (temperature block and prodrug)\",\n      \"pmids\": [\"27271567\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Site-directed mutagenesis of BTN3A1 B30.2 domain identified H381 as critical for ligand binding (mutation fully blocks binding), while mutations to charged surface residues impacted diphosphate interactions. Monophosphonate analogs bind similarly to BTN3A1 but differ in antigenicity, demonstrating that BTN3A1 binding and T cell activation efficacy are not linearly correlated.\",\n      \"method\": \"Site-directed mutagenesis, fluorescence polarization binding assay, T cell proliferation and IFN-γ assays, molecular docking\",\n      \"journal\": \"Journal of medicinal chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis with in vitro binding assay; single lab with biochemical and cellular validation\",\n      \"pmids\": [\"31268699\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"BTN3A1 on tumor cells inhibits tumor-reactive αβ T cell receptor activation by preventing segregation of N-glycosylated CD45 from the immune synapse. CD277-specific antibodies restore αβ T cell effector activity and elicit BTN2A1-dependent γδ lymphocyte cytotoxicity against BTN3A1+ cancer cells.\",\n      \"method\": \"In vitro co-culture T cell activation assays, immune synapse imaging, BTN3A1 expression manipulation, in vivo tumor models\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mechanistic finding linking BTN3A1 to CD45 segregation at immune synapse with multiple functional readouts, replicated in vivo; published in Science with broad methods\",\n      \"pmids\": [\"32820120\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"BTN3A1 promotes radioresistance in esophageal squamous cell carcinoma by activating ULK1-mediated autophagy; BTN3A1 interacts with ULK1 (identified by immunoprecipitation and mass spectrometry) and promotes ULK1 phosphorylation to initiate autophagy. HIF-1α directly promotes BTN3A1 transcription upon irradiation (confirmed by ChIP and luciferase reporter assay).\",\n      \"method\": \"Immunoprecipitation, mass spectrometry, western blotting, ChIP, luciferase reporter assay, KD/OE in vitro and in vivo\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP/MS identifies ULK1 interaction, ChIP/luciferase confirms HIF-1α-BTN3A1 transcriptional axis; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"36418890\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"NLRC5 promotes transcription of BTN3A1-3 genes through an atypical regulatory motif in their promoters. Forced NLRC5 expression promoted Vγ9Vδ2 T cell-mediated killing of tumor cells in a BTN3A-dependent manner.\",\n      \"method\": \"Promoter reporter assays, gene expression manipulation (OE/KD), T cell cytotoxicity assays, correlation analysis in primary cells\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — promoter regulatory motif validated with functional BTN3A-dependent rescue; single lab, promoter reporter plus functional assay\",\n      \"pmids\": [\"33364588\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"T cells express all three BTN3/CD277 isoforms, whereas NK cells express mostly BTN3A2 (which lacks the B30.2 intracellular domain). BTN3A1 triggering on T cells enhances TCR-induced signaling; however, BTN3A1 triggering does not affect NK cell activation, while specific engagement of BTN3A2 (but not BTN3A1) decreases NKp30-induced cytokine production.\",\n      \"method\": \"Isoform-specific expression analysis, functional antibody triggering assays, cytokine/proliferation measurements, TCR signaling assays\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — functional co-stimulation assays with isoform-specific context; single lab, multiple functional readouts\",\n      \"pmids\": [\"21918970\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"HMBPP binds to the B30.2 domain of BTN3A1 but not to BTN2A1 (confirmed by 31P-NMR, abrogating signals from both phosphorus atoms upon BTN3A1 binding). The BTN2A1 B30.2 domain forms a homodimer; mutation L325G (but not L318G) both prevents BTN2A1 internal domain homodimerization and blocks its binding to HMBPP-bound BTN3A1 (measured by ITC), identifying a cytoplasmic BTN2A1-BTN3A1/HMBPP complex.\",\n      \"method\": \"31P-NMR, size exclusion chromatography, NMR, isothermal titration calorimetry (ITC), site-directed mutagenesis, functional T cell ELISA assays\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR directly shows HMBPP binds BTN3A1 not BTN2A1; ITC measures BTN2A1-BTN3A1/HMBPP complex; mutagenesis validates functional importance; multiple orthogonal methods in one study\",\n      \"pmids\": [\"37171180\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"19F NMR of specific BTN3A1 point mutants (W421C, T449C, T506C) showed these residues are conformationally influenced by HMBPP and BTN2A1 association. W421 is at the BTN2A1 binding interface (19F labeling of W421C reduces BTN2A1 binding affinity). T506 is distal from the pAg binding site, indicating a larger conformational change in the B30.2 domain upon HMBPP and BTN2A1 binding. Juxtamembrane residues T304C and G323C are unaffected, localizing changes to the B30.2 domain.\",\n      \"method\": \"19F solution NMR, site-directed mutagenesis, binding affinity measurements\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — 19F NMR with point mutants directly maps conformational changes; single lab, single method type but mechanistically detailed\",\n      \"pmids\": [\"40079188\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Cryo-EM structures show that HMBPP bridges the intracellular B30.2 domains of BTN3A1 and BTN2A1 within the full-length BTN3A1-BTN3A2-BTN2A1 complex. Upon Vγ9Vδ2 TCR engagement, BTN3A2-BTN2A1 ectodomain interaction dissociates: BTN2A1 binds the lateral surface of the Vγ9 chain and BTN3A2 binds the apical surface of the Vδ2 chain, suggesting a 'pliers-like gripping' mechanism for TCR activation.\",\n      \"method\": \"Cryo-electron microscopy (cryo-EM) structural determination of full-length complexes\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — high-quality structural data (cryo-EM), but preprint not yet peer-reviewed; single study\",\n      \"pmids\": [\"bio_10.1101_2024.10.02.616253\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"BTN3A1 expressed on cervical cancer cells promotes Vγ9Vδ2 T cell exhaustion by engaging γδ TCRs and upregulating transcription factors NR4A2/3 downstream of TCR signaling. Blocking TCR or knocking down NR4A2/3 reverses BTN3A1-induced T cell exhaustion. IFN-γ secreted by Vδ2 T cells in turn promotes BTN3A1 and PD-L1 expression on tumor cells (a feedback loop).\",\n      \"method\": \"BTN3A1 KO/OE in tumor cell lines, co-culture with Vδ2 T cells, flow cytometry, RNA-seq, Western blot, gene knockdown\",\n      \"journal\": \"Cell communication and signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO/OE with defined TCR-signaling/NR4A2/3 pathway placement and rescue experiment; single lab, multiple methods\",\n      \"pmids\": [\"39342337\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ICT01 (agonist antibody targeting BTN3A extracellular domain) binds to a unique region in the BTN3A extracellular domain, destabilizes the BTN2A1-BTN3A interface, and facilitates Vγ9Vδ2 TCR engagement, resulting in γδ T cell activation independently of phosphoantigens.\",\n      \"method\": \"Structural analysis, biochemical assays, cellular T cell activation assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 1 / Weak — preprint; structural + biochemical + cellular methods described but not yet peer-reviewed; single study\",\n      \"pmids\": [\"bio_10.1101_2025.10.21.681109\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Full activation of Vγ9Vδ2 TCR requires phosphorylation of juxtamembrane (JTM) amino acids of BTN3A1, leading to activating heterodimerization of BTN2A1 and BTN3A1 at the cell surface. Single oncogenic mutations in cells upregulate surface BTN2A1 and enable Vγ9Vδ2 TCR binding, but full T cell activation additionally requires BTN3A1 JTM phosphorylation-dependent heterodimerization. PHLDB2, SYNJ2, and CARMIL1 were identified as key regulators of this surface heterodimerization.\",\n      \"method\": \"Step-wise mutagenesis organoid/cell models, surface BTN2A1/3A1 expression analysis, protein interactome mapping, in vitro and in vivo T cell activation assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 2 / Weak — preprint; mechanistic pathway placement with interactome data, but not yet peer-reviewed; single study\",\n      \"pmids\": [\"bio_10.1101_2024.11.19.624272\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"BTN3A1 is a type-1 transmembrane protein that acts as an intracellular phosphoantigen (pAg) sensor through its B30.2 domain (directly binding HMBPP and IPP), undergoes a conformational change upon pAg binding that propagates through the protein, forms a cytoplasmic complex with BTN2A1 (bridged by HMBPP) and associates with BTN3A2 extracellularly, reorganizes at the plasma membrane to engage the Vγ9Vδ2 TCR (with BTN2A1 contacting the Vγ9 chain and BTN3A2 the Vδ2 chain) via an inside-out signaling mechanism requiring its juxtamembrane and periplakin-binding domains; additionally, BTN3A1 inhibits αβ T cell activation by preventing CD45 exclusion from the immune synapse, constitutively associates with TBK1 and mediates dynein/MAP4-dependent perinuclear redistribution to facilitate TBK1-IRF3 phosphorylation in innate antiviral signaling, and in cancer cells interacts with ULK1 to promote autophagy-mediated radioresistance downstream of HIF-1α.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"BTN3A1 (CD277) is a type-I transmembrane butyrophilin that operates as an intracellular phosphoantigen (pAg) sensor required for activation of Vγ9Vδ2 T cells [#0, #1]. Sensing occurs through its cytoplasmic B30.2 domain, which directly binds pAgs in a positively charged surface pocket—microbial HMBPP with high affinity and endogenous IPP with lower affinity—and discriminates antigenic from non-antigenic phosphometabolites by their ability to trigger a conformational change that propagates from the binding pocket to distal regions of the domain [#2, #3, #4]. pAg binding does not act alone: HMBPP bridges the B30.2 domain of BTN3A1 to that of BTN2A1, forming a cytoplasmic BTN2A1–BTN3A1 complex within a larger BTN3A1–BTN3A2–BTN2A1 assembly, and these intracellular events are relayed to the cell surface through the BTN3A1 juxtamembrane region and a membrane-proximal di-leucine motif that recruits periplakin, both of which are required for T cell triggering [#14, #2, #5]. Surface signal output requires reorganization of the extracellular V-shaped homodimers and juxtamembrane phosphorylation-dependent BTN2A1–BTN3A1 heterodimerization, with BTN2A1 and BTN3A2 ectodomains engaging distinct surfaces of the Vγ9Vδ2 TCR in an inside-out 'gripping' mechanism [#3, #16]. Beyond γδ T cell triggering, BTN3A1 on tumor cells suppresses αβ T cell activation by preventing exclusion of N-glycosylated CD45 from the immune synapse [#10], acts as a positive regulator of nucleic-acid-induced type I interferon signaling by constitutively associating with TBK1 and undergoing dynein/MAP4-dependent perinuclear redistribution to promote TBK1–IRF3 phosphorylation [#6], and is transcriptionally induced by HIF-1α to drive ULK1-mediated autophagy and radioresistance in esophageal carcinoma [#11]. Its transcription is controlled by NLRC5 and HIF-1α [#12, #11].\",\n  \"teleology\": [\n    {\n      \"year\": 2012,\n      \"claim\": \"Established that the BTN3A1 isoform specifically, not other CD277 isoforms, is the molecule required for phosphoantigen-induced Vγ9Vδ2 T cell activation, and linked pAg sensing to changes in BTN3A1 membrane behavior.\",\n      \"evidence\": \"CD277 knockdown, domain-shuffling, FRAP, and functional agonist/antagonist antibody assays\",\n      \"pmids\": [\"22767497\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify where pAg binds within BTN3A1\", \"Did not resolve the molecular link between altered membrane mobility and TCR engagement\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Defined the resting architecture of BTN3A as V-shaped homodimers associating through their membrane-proximal Ig domains, and localized agonist/antagonist antibody epitopes to the Ig-V domain.\",\n      \"evidence\": \"X-ray crystallography and antibody binding plus functional T cell assays\",\n      \"pmids\": [\"22846996\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address how ectodomain conformation couples to intracellular sensing\", \"No structure of the full-length receptor or its partners\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Distinguished antibody-mediated from pAg-mediated activation, showing BTN3A1 alone suffices for agonist-antibody triggering but pAg sensing requires additional chromosome-6-encoded gene(s).\",\n      \"evidence\": \"Genetic complementation comparing BTN3A1-transduced CHO cells with cells carrying human chromosome 6, across multiple TCR transductants\",\n      \"pmids\": [\"24890657\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The required cofactor gene(s) on chromosome 6 were not identified here\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Provided the direct biochemical basis for sensing by showing pAgs bind the intracellular B30.2 domain and identifying periplakin as a cytoplasmic-tail partner functionally required for γδ activation.\",\n      \"evidence\": \"In vitro B30.2 binding assays, yeast two-hybrid, co-IP, and knockdown/re-expression rescue with functional T cell assays\",\n      \"pmids\": [\"25637025\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not show how B30.2 occupancy is transmitted to the membrane or to the TCR\", \"Mechanistic role of periplakin beyond binding not resolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Revealed a distinct innate-immune function: BTN3A1 constitutively binds TBK1 and undergoes MAP4/dynein-dependent perinuclear relocation to bridge TBK1–IRF3 and drive type I interferon signaling.\",\n      \"evidence\": \"Reciprocal co-IP, BTN3A1 and MAP4 knockdown, subcellular fractionation/immunofluorescence, and IFN-β reporter assays\",\n      \"pmids\": [\"27911820\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How nucleic-acid sensing triggers BTN3A1 redistribution is unresolved\", \"Relationship between this innate role and pAg sensing is not addressed\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Supported the inside-out model by demonstrating that intracellular delivery of HMBPP into target cells is required for BTN3A1-dependent lysis.\",\n      \"evidence\": \"Cytotoxicity assays with temperature-dependent uptake block and a cell-permeable prodrug bypass\",\n      \"pmids\": [\"27271567\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Indirect inference of intracellular sensing from uptake manipulation\", \"Did not directly visualize intracellular pAg-BTN3A1 engagement\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defined the sensing mechanism as conformational: pAg binding induces a global B30.2 conformational change, and locking the ectodomain V-shape blunts activation, tying intracellular sensing to extracellular reorganization.\",\n      \"evidence\": \"NMR, X-ray crystallography, MD simulations, and cellular T cell activation assays (two studies)\",\n      \"pmids\": [\"28807997\", \"28862425\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the B30.2 conformational change propagates across the membrane was not established\", \"Identity of the surface partner transmitting the signal not yet known\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identified the juxtamembrane domain as a critical transmission element, with mutations bidirectionally tuning γδ T cell reactivity.\",\n      \"evidence\": \"Domain mutagenesis with functional T cell activation assays\",\n      \"pmids\": [\"28461569\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The interacting partner at the juxtamembrane interface was not defined here\", \"Single-lab mutagenesis without structural confirmation of the proposed dimerization interface\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Mapped B30.2 ligand-binding determinants (notably H381) and showed that binding affinity and antigenic potency are not linearly correlated, reinforcing the conformational-sensor model.\",\n      \"evidence\": \"Site-directed mutagenesis, fluorescence-polarization binding, T cell proliferation/IFN-γ assays, and docking\",\n      \"pmids\": [\"31268699\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not resolve what distinguishes activating from non-activating bound conformations structurally\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Uncovered a tumor-immunosuppressive function whereby BTN3A1 inhibits αβ TCR activation by preventing CD45 segregation from the immune synapse, while anti-CD277 restores αβ responses and elicits BTN2A1-dependent γδ cytotoxicity.\",\n      \"evidence\": \"Co-culture T cell assays, immune synapse imaging, BTN3A1 expression manipulation, and in vivo tumor models\",\n      \"pmids\": [\"32820120\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of CD45 retention by BTN3A1 not detailed\", \"Relationship to the γδ-activating function in the same synapse not fully integrated\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Placed BTN3A transcription downstream of NLRC5, linking antigen-presentation regulation to γδ-mediated tumor killing.\",\n      \"evidence\": \"Promoter reporter assays, NLRC5 OE/KD, and BTN3A-dependent T cell cytotoxicity assays\",\n      \"pmids\": [\"33364588\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The atypical promoter motif's direct occupancy mechanism not biochemically resolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified a cancer-intrinsic role in which HIF-1α-induced BTN3A1 binds ULK1 and promotes its phosphorylation to drive autophagy-mediated radioresistance.\",\n      \"evidence\": \"Co-IP/mass spectrometry, ChIP, luciferase reporter, and KD/OE in vitro and in vivo in esophageal carcinoma\",\n      \"pmids\": [\"36418890\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether BTN3A1 directly catalyzes or scaffolds ULK1 phosphorylation is unclear\", \"Relationship to BTN3A1's immune functions not addressed\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstrated the molecular partnership underlying pAg relay: HMBPP binds BTN3A1 (not BTN2A1) and bridges a cytoplasmic BTN2A1–BTN3A1 complex dependent on BTN2A1 B30.2 homodimerization.\",\n      \"evidence\": \"31P-NMR, NMR, ITC, size-exclusion chromatography, and mutagenesis (L325G) with functional T cell ELISA\",\n      \"pmids\": [\"37171180\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry within the full receptor assembly not resolved here\", \"How the cytoplasmic complex couples to surface TCR engagement not shown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Linked surface heterodimerization to activation, showing that juxtamembrane phosphorylation of BTN3A1 drives BTN2A1–BTN3A1 surface heterodimerization required for full Vγ9Vδ2 TCR activation, and identified PHLDB2, SYNJ2, and CARMIL1 as regulators.\",\n      \"evidence\": \"Step-wise mutagenesis organoid/cell models, surface expression analysis, interactome mapping, and T cell assays (preprint)\",\n      \"pmids\": [\"bio_10.1101_2024.11.19.624272\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Preprint, not yet peer-reviewed\", \"The responsible juxtamembrane kinase is not identified\", \"Mechanistic roles of PHLDB2/SYNJ2/CARMIL1 not defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Provided structural integration of the full pathway, showing HMBPP-bridged intracellular B30.2 contacts and a 'pliers-like' ectodomain rearrangement engaging the Vγ9Vδ2 TCR.\",\n      \"evidence\": \"Cryo-EM of full-length BTN3A1–BTN3A2–BTN2A1 complexes (preprint)\",\n      \"pmids\": [\"bio_10.1101_2024.10.02.616253\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not yet peer-reviewed\", \"Dynamics of the inside-out transition between resting and engaged states not captured\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended the tumor-immune role by showing tumor BTN3A1 drives Vγ9Vδ2 T cell exhaustion via TCR-dependent NR4A2/3 induction within an IFN-γ feedback loop upregulating BTN3A1 and PD-L1.\",\n      \"evidence\": \"BTN3A1 KO/OE in tumor lines, co-culture with Vδ2 T cells, RNA-seq, flow cytometry, and NR4A2/3 knockdown rescue\",\n      \"pmids\": [\"39342337\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal contribution of the IFN-γ feedback loop in vivo not fully established\", \"Generalizability beyond cervical cancer not tested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Refined the conformational map, using 19F NMR to localize HMBPP/BTN2A1-induced changes to the B30.2 domain and to a BTN2A1-binding interface residue (W421), while juxtamembrane residues remain unaffected.\",\n      \"evidence\": \"19F solution NMR of point mutants with binding affinity measurements\",\n      \"pmids\": [\"40079188\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single method type\", \"How the larger B30.2 conformational change is mechanically transmitted not resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how the intracellular B30.2 conformational change and BTN2A1 complex are mechanically transduced across the membrane to drive surface heterodimerization, and which kinase phosphorylates the BTN3A1 juxtamembrane region.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No identified juxtamembrane kinase\", \"No peer-reviewed full-length structure of resting versus TCR-engaged states\", \"Integration of BTN3A1's γδ-sensing, αβ-suppressive, interferon, and autophagy roles is incomplete\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [2, 3, 4, 14]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [2, 4]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 16]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [6, 11]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1, 16]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [2, 6, 14]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 6, 10]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [6, 13, 17]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [11]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [10, 11, 17]}\n    ],\n    \"complexes\": [\n      \"BTN3A1-BTN3A2-BTN2A1 receptor complex\"\n    ],\n    \"partners\": [\n      \"BTN2A1\",\n      \"BTN3A2\",\n      \"periplakin\",\n      \"TBK1\",\n      \"MAP4\",\n      \"ULK1\",\n      \"IRF3\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":5,"faith_pct":80.0}}