{"gene":"B3GNT2","run_date":"2026-06-09T22:02:44","timeline":{"discoveries":[{"year":1999,"finding":"B3GNT2 (beta3GnT) is a poly-N-acetyllactosamine synthase that both initiates and elongates poly-N-acetyllactosamine chains, showing marked preference for Gal(β1-4)Glc(NAc)-based acceptors; no activity was detected on type 1 Gal(β1-3)GlcNAc or O-glycan core 1 acceptors. The protein is a type II transmembrane polypeptide structurally related to β1,3-galactosyltransferases, sharing conserved amino acid motifs despite inverted donor/acceptor specificities.","method":"In vitro enzyme assay with defined acceptor substrates; substrate specificity panel; cDNA cloning and recombinant expression","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro enzymatic reconstitution with substrate specificity panel; foundational characterization replicated by subsequent studies","pmids":["9892646"],"is_preprint":false},{"year":2000,"finding":"Mouse B3GNT2 ortholog is a type II membrane protein localized to the Golgi apparatus, with enzyme activity preferring Gal(β1-4)Glc(NAc) acceptors; proton NMR confirmed incorporation of GlcNAc in β1,3 linkage to terminal Gal. The human gene maps to chromosome 2p15.","method":"Enzyme assay; NMR analysis of product; subcellular fractionation/localization; Northern blot","journal":"Glycoconjugate journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro enzymatic activity confirmed by NMR; Golgi localization by direct experiment; consistent with human gene characterization","pmids":["11511811"],"is_preprint":false},{"year":2005,"finding":"B3GNT2 and B3GNT8 form a heterocomplex that enhances enzymatic activity: when the two soluble recombinant enzymes are mixed, the Vmax/Km value is 9.3-fold higher than B3GNT2 alone and 160-fold higher than B3GNT8 alone. Both enzymes share similar substrate specificity, preferring tetraantennary N-glycans and 2,6-branched triantennary glycans. Gel filtration confirmed formation of a heterocomplex of ~110-210 kDa.","method":"In vitro enzyme activity assay of recombinant proteins; gel filtration chromatography to detect complex formation","journal":"Glycobiology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with kinetic analysis and physical complex detection by gel filtration; single lab but two orthogonal methods","pmids":["15917431"],"is_preprint":false},{"year":2005,"finding":"N-glycosylation of B3GNT2 is required for enzymatic activity and secretion: four of five potential N-glycosylation sites are occupied. N-glycosylation at Asn219 is necessary for beta3GnT activity; N-glycosylation at Asn127 and Asn219 is critical for efficient protein secretion. The N-terminal region (stem region) is also important for maintaining active protein structure, as truncation of amino acids 1-82 abolishes activity.","method":"Site-directed mutagenesis of N-glycosylation sites; tunicamycin inhibition; truncation analysis; baculovirus expression system","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mutagenesis combined with pharmacological inhibition and truncation in a single study, two orthogonal approaches","pmids":["15737642"],"is_preprint":false},{"year":2010,"finding":"B3GNT2 is the major poly-N-acetyllactosamine (polylactosamine) synthase in vivo. B3gnt2-knockout mice show markedly reduced polylactosamine on N-glycans across tissues. Polylactosamine is present on immune co-stimulatory molecules CD28 and CD19; B3gnt2-/- T cells show hyperactivation (increased Ca2+ flux and proliferation) upon anti-CD3ε/CD28 stimulation, and B3gnt2-/- B cells show hyperproliferation upon BCR stimulation, indicating polylactosamine synthesized by B3GNT2 normally suppresses lymphocyte activation.","method":"Knockout mouse model; flow cytometry; LEL lectin-blotting; glycan analysis by metabolic labeling; lectin microarray; Ca2+ flux assay; proliferation assay","journal":"Methods in enzymology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO mouse with multiple orthogonal readouts linking B3GNT2-dependent polylactosamine on CD28/CD19 to immune suppression","pmids":["20816167"],"is_preprint":false},{"year":2014,"finding":"B3GNT2 co-immunoprecipitates with EGFR in H7721 hepatocellular carcinoma cells, identifying EGFR as a B3GNT2-targeting protein. Polylactosamine on EGFR is increased by EGF treatment and decreased by ATRA, correlating with altered B3GNT2 expression.","method":"Co-immunoprecipitation; RT-PCR for enzyme expression; lectin staining","journal":"Asian Pacific journal of cancer prevention","confidence":"Medium","confidence_rationale":"Tier 3 / Weak — single Co-IP experiment in one cancer cell line, single lab, no mutagenesis or functional rescue","pmids":["25605193"],"is_preprint":false},{"year":2014,"finding":"Co-expression of B3GNT2 and GCNT2 (β1,6-branching glycosyltransferase) in HEK293T cells produces high levels of poly-N-acetyllactosamine (PLN) on the cell surface and on adenylyl cyclase 3, demonstrating cooperative function: GCNT2 generates β1,6-branches that are subsequently extended by B3GNT2 to generate PLN chains.","method":"Co-transfection of HEK293T cells; flow cytometry for cell-surface PLN; immunoprecipitation of adenylyl cyclase 3 with lectin detection","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain-of-function co-expression with defined molecular readout in cell culture; single lab","pmids":["24105809"],"is_preprint":false},{"year":2016,"finding":"Mutations in B3GNT2 identified in colorectal cancer cell lines markedly alter protein localization, post-translational modification, and/or encoded enzymatic activities, and affect migratory potential of colon carcinoma cells, indicating these are functionally deleterious mutations contributing to aberrant glycosylation in CRC.","method":"Targeted re-sequencing; biochemical characterization of wild-type vs. mutant glycosyltransferases (localization, PTM, enzymatic activity assays); migration assay","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal biochemical assays characterizing mutant vs. wild-type protein; single lab","pmids":["27004849"],"is_preprint":false},{"year":2020,"finding":"Crystal structures of human B3GNT2 were determined in unliganded, donor substrate (UDP-GlcNAc)-bound, acceptor substrate-bound, and product-bound states (1.85–2.35 Å resolution). Kinetic studies show transglycosylation follows a sequential mechanism. Critical residues for donor and acceptor recognition and catalysis were identified; mutations of invariant residues impair B3GNT2 activity in cell assays. B3GNT2 contains a novel N-terminal helical domain that stabilizes the catalytic domain and may distinguish among acceptor substrates.","method":"X-ray crystallography (5 structures); kinetic assays; site-directed mutagenesis with cell-based activity assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures in multiple states plus mutagenesis plus kinetic analysis in a single rigorous study","pmids":["33158990"],"is_preprint":false},{"year":2020,"finding":"Crystal structures of human B3GNT2 in complex with UDP:Mg2+ and with UDP:Mg2+ plus the acceptor lacto-N-neotetraose reveal: (1) B3GNT2 uses the GT-A fold with a DxD motif coordinating Mg2+ for UDP-GlcNAc donor binding; (2) the acceptor binding site contacts only the terminal Galβ(1,4)-GlcNAcβ(1,3)- disaccharide, explaining specificity for both N- and O-glycan acceptors; (3) modeling supports a direct displacement inverting catalytic mechanism.","method":"X-ray crystallography (donor-bound and donor+acceptor-bound complexes); structural modeling","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — independent structural study replicating and extending the active site and mechanism findings from PMID:33158990","pmids":["33229435"],"is_preprint":false},{"year":2022,"finding":"CRISPR activation screen identified B3GNT2 overexpression as conferring resistance to T cell-mediated cytotoxicity in melanoma cells and mouse xenografts. Mechanistically, B3GNT2 (a poly-N-acetyllactosamine synthase) targets >10 ligands and receptors on the tumor cell surface, disrupting interactions between tumor cells and T cells and reducing T cell activation.","method":"Genome-scale CRISPR activation screen; overexpression validation in multiple cancer cell types; mouse xenograft models; T cell cytotoxicity assays; analysis of tumor-T cell interactions","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — gain-of-function screen validated in multiple cancer cell types and in vivo models, with mechanistic follow-up on immune evasion targets","pmids":["35338135"],"is_preprint":false},{"year":2022,"finding":"Mutagenesis of B3GNT2 hydrophobic core residue T336I increases catalytic efficiency by modulating the conformational occupancy of the catalytic base between 'D-in' and acceptor-accessible 'D-out' conformations, as demonstrated by experimental mutational analysis and molecular dynamics simulations.","method":"Site-directed mutagenesis; molecular dynamics simulations; enzymatic activity assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — mutagenesis with kinetic characterization and MD simulation; single lab study","pmids":["35780833"],"is_preprint":false},{"year":2023,"finding":"B3GNT2 promotes extension of polylactosamine chains at multiple N-glycans on the Wnt co-receptor LRP6, enhancing LRP6 trafficking to the plasma membrane and promoting Wnt/β-catenin signaling. Both gain-of-function (B3GNT2 overexpression) and loss-of-function evidence support this role.","method":"Cell culture-based expression screen; gain-of-function and loss-of-function experiments; glycan analysis of LRP6; cell surface trafficking assay; Wnt/β-catenin reporter assay","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal gain/loss-of-function with biochemical glycan analysis of LRP6; single lab","pmids":["36980204"],"is_preprint":false},{"year":2024,"finding":"In a secondary CRISPR screen in SPPL3-deficient cells, B3GNT2 was identified as the transferase mediating poly-LacNAc extension on complex N-glycans that underlies resistance to NK cell cytotoxicity. Mass spectrometry confirmed enrichment of N-glycans bearing poly-LacNAc upon SPPL3 loss; inhibiting N-glycan maturation restored NK receptor binding and sensitivity.","method":"Genome-wide CRISPR screen; mass spectrometry of N-glycans; NK cytotoxicity assay; N-glycan maturation inhibition","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — functional CRISPR screen validated by mass spectrometry glycan analysis and NK cytotoxicity assays; multiple orthogonal methods","pmids":["38619967"],"is_preprint":false},{"year":2024,"finding":"Silencing of B3GNT2 in human liver endothelial cells (HLECs) decreased release of Factor VIII (FVIII), and silencing of B3GNT2 in human vein endothelial cells decreased release of von Willebrand factor (VWF), demonstrating a functional role for B3GNT2 in FVIII and VWF secretion.","method":"siRNA knockdown in human endothelial cells; FVIII and VWF release measurement","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean knockdown with specific protein secretion readout in human primary cells; single study","pmids":["38320121"],"is_preprint":false},{"year":2024,"finding":"B3GNT2 tolerates modified UDP-GlcNAc donors bearing azide, alkyne, or diazirine groups at the C2-acetamido position for transfer to glycan acceptors (albeit less efficiently than natural UDP-GlcNAc), and can exo-enzymatically install GlcNAz on cell-surface glycans, enabling subsequent extension with B4GalT1 to form LacNAz motifs.","method":"In vitro enzyme assay with unnatural nucleotide-sugar substrates; cell-surface glyco-engineering with flow cytometric detection","journal":"ACS chemical biology","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro biochemical assay with synthetic substrates plus cell-based application; single lab","pmids":["38394345"],"is_preprint":false},{"year":2025,"finding":"Functional knockdown of B3GNT2 in nociceptive sensory neurons (which upregulate B3GNT2 after NGF/PKC sensitization) identified B3GNT2 as a potential effector of nociceptor sensitization, linking its glycosyltransferase activity to mechanical pain sensitization.","method":"Deep visual proteomics; functional knockdown experiments in cultured nociceptive neurons; mechanical sensitization assay","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockdown with defined phenotypic readout (mechanical sensitization); novel finding but single study","pmids":["41965357"],"is_preprint":false}],"current_model":"B3GNT2 is a Golgi-resident, type II transmembrane β1,3-N-acetylglucosaminyltransferase (GT-A fold, inverting mechanism) that is the major poly-N-acetyllactosamine (poly-LacNAc) synthase in mammals: it sequentially transfers GlcNAc in β1,3 linkage onto Galβ1,4GlcNAc-terminating acceptors on both N- and O-glycans, requiring N-glycosylation at Asn219 for activity and cooperating with B3GNT8 (as a heterocomplex) and GCNT2 (which provides β1,6-branches) to elongate poly-LacNAc chains; these long poly-LacNAc chains on immune co-receptors (CD28, CD19) suppress lymphocyte activation, and their presence on tumor cell surfaces disrupts tumor–T cell and tumor–NK cell interactions to promote immune evasion, while B3GNT2-mediated glycosylation of LRP6 also enhances Wnt/β-catenin signaling and modulates FVIII/VWF secretion from endothelial cells."},"narrative":{"mechanistic_narrative":"B3GNT2 is the major poly-N-acetyllactosamine (poly-LacNAc) synthase in mammals, a Golgi-resident type II transmembrane β1,3-N-acetylglucosaminyltransferase that both initiates and elongates poly-LacNAc by transferring GlcNAc in β1,3 linkage onto Galβ1,4GlcNAc-terminating acceptors, with marked preference for type II (LacNAc) over type 1 or O-glycan core 1 acceptors [PMID:9892646, PMID:11511811]. B3gnt2-knockout mice lose the bulk of N-glycan polylactosamine across tissues, establishing it as the principal enzyme generating these chains in vivo [PMID:20816167]. Crystal structures in unliganded, donor (UDP-GlcNAc)-, acceptor-, and product-bound states show a GT-A fold using a DxD motif to coordinate Mg2+ for donor binding, an acceptor pocket that contacts only the terminal Galβ1,4-GlcNAcβ1,3- disaccharide (rationalizing its dual specificity for N- and O-glycans), and a direct-displacement inverting catalytic mechanism; a novel N-terminal helical domain stabilizes the catalytic domain [PMID:33158990, PMID:33229435]. Enzyme function depends on N-glycosylation at Asn219 and on an intact stem region [PMID:15737642], and the enzyme acts with B3GNT8 as an activity-enhancing heterocomplex and with the β1,6-branching enzyme GCNT2 to build branched poly-LacNAc [PMID:15917431, PMID:24105809]. Functionally, B3GNT2-dependent poly-LacNAc decorates immune co-receptors CD28 and CD19 to restrain lymphocyte activation [PMID:20816167], and its overexpression on tumor cells coats surface ligands and receptors to disrupt tumor–T cell and tumor–NK cell interactions, conferring resistance to T cell and NK cell cytotoxicity and promoting immune evasion [PMID:35338135, PMID:38619967]. Beyond immunity, B3GNT2 glycosylates the Wnt co-receptor LRP6 to enhance its plasma-membrane trafficking and Wnt/β-catenin signaling [PMID:36980204] and contributes to endothelial secretion of Factor VIII and von Willebrand factor [PMID:38320121].","teleology":[{"year":1999,"claim":"Established the core enzymatic identity, defining B3GNT2 as a β1,3-N-acetylglucosaminyltransferase that initiates and elongates poly-LacNAc with strict preference for type II LacNAc acceptors.","evidence":"cDNA cloning, recombinant expression, and in vitro enzyme assays with a defined acceptor specificity panel","pmids":["9892646"],"confidence":"High","gaps":["In vivo physiological substrates not yet defined","Subcellular localization not directly demonstrated in this study"]},{"year":2000,"claim":"Confirmed the chemical linkage and Golgi residence, localizing the enzyme to the compartment where N-/O-glycan elongation occurs and verifying β1,3 GlcNAc addition to terminal Gal.","evidence":"Enzyme assay with proton NMR of product, subcellular fractionation, and Northern blot in the mouse ortholog","pmids":["11511811"],"confidence":"High","gaps":["Did not address regulation of activity or partner enzymes"]},{"year":2005,"claim":"Showed the enzyme does not act alone — a B3GNT2–B3GNT8 heterocomplex markedly boosts catalytic efficiency, revealing a regulatory mode of assembly.","evidence":"In vitro kinetic assays of recombinant proteins and gel filtration to detect physical complex","pmids":["15917431"],"confidence":"High","gaps":["Stoichiometry and in vivo prevalence of the heterocomplex not established","Structural basis of complex enhancement unknown"]},{"year":2005,"claim":"Defined post-translational and structural requirements for activity, showing N-glycosylation at Asn219 and an intact stem region are needed for catalysis and secretion.","evidence":"Site-directed mutagenesis of N-glycosylation sites, tunicamycin inhibition, and truncation analysis in baculovirus expression","pmids":["15737642"],"confidence":"High","gaps":["Mechanism by which Asn219 glycan supports folding/activity not resolved"]},{"year":2010,"claim":"Demonstrated B3GNT2 is the dominant in vivo poly-LacNAc synthase and linked its product on CD28/CD19 to suppression of lymphocyte activation.","evidence":"B3gnt2-knockout mice with lectin blotting, glycan analysis, Ca2+ flux and proliferation assays on T and B cells","pmids":["20816167"],"confidence":"High","gaps":["Direct molecular mechanism linking poly-LacNAc to receptor signaling thresholds not dissected","Other glycoprotein targets in immune cells not enumerated"]},{"year":2014,"claim":"Extended the target repertoire by identifying EGFR as a B3GNT2-associated glycoprotein and demonstrating cooperative poly-LacNAc synthesis with the branching enzyme GCNT2.","evidence":"Co-immunoprecipitation with EGFR in hepatocarcinoma cells; co-transfection of B3GNT2 and GCNT2 in HEK293T with lectin readout on adenylyl cyclase 3","pmids":["25605193","24105809"],"confidence":"Medium","gaps":["EGFR association rests on a single Co-IP without reciprocal validation or mutagenesis","Functional consequence of EGFR glycosylation not tested"]},{"year":2016,"claim":"Connected B3GNT2 sequence variation to disease biology, showing colorectal-cancer mutations alter localization, modification, activity, and cell migration.","evidence":"Targeted re-sequencing with biochemical characterization of wild-type versus mutant enzyme plus migration assays","pmids":["27004849"],"confidence":"Medium","gaps":["Causal contribution of individual mutations to tumor progression in vivo not established"]},{"year":2020,"claim":"Provided atomic-resolution mechanism: multiple crystal structures defined the GT-A fold, DxD/Mg2+ donor coordination, a disaccharide-recognizing acceptor pocket explaining dual N-/O-glycan specificity, and an inverting direct-displacement catalysis.","evidence":"X-ray crystallography of unliganded, donor-, acceptor-, and product-bound states with kinetics and mutagenesis (two independent studies)","pmids":["33158990","33229435"],"confidence":"High","gaps":["Structure of the B3GNT2–B3GNT8 heterocomplex not solved","Conformational dynamics during catalysis only inferred"]},{"year":2022,"claim":"Defined a conformational determinant of catalytic efficiency, showing a hydrophobic-core residue toggles the catalytic base between 'D-in' and acceptor-accessible 'D-out' states.","evidence":"Site-directed mutagenesis (T336I), molecular dynamics simulations, and enzymatic assays","pmids":["35780833"],"confidence":"Medium","gaps":["Physiological relevance of the D-in/D-out equilibrium not demonstrated","Single-lab MD-based mechanism"]},{"year":2022,"claim":"Established a causal role in tumor immune evasion, showing B3GNT2 overexpression coats multiple surface ligands/receptors with poly-LacNAc to blunt T cell killing.","evidence":"Genome-scale CRISPR activation screen, overexpression validation, mouse xenografts, and T cell cytotoxicity/interaction assays","pmids":["35338135"],"confidence":"High","gaps":["Identity and relative contribution of the >10 individual surface targets not fully resolved"]},{"year":2023,"claim":"Identified a signaling target, showing B3GNT2 extends poly-LacNAc on LRP6 to enhance its surface trafficking and Wnt/β-catenin signaling.","evidence":"Expression screen with reciprocal gain/loss-of-function, glycan analysis of LRP6, trafficking and Wnt reporter assays","pmids":["36980204"],"confidence":"Medium","gaps":["Whether LRP6 glycosylation is direct in vivo and dose-dependent in tissues not established"]},{"year":2024,"claim":"Generalized the immune-evasion mechanism to NK cells and to a regulatory axis, placing B3GNT2 downstream of SPPL3 loss as the transferase whose poly-LacNAc blocks NK receptor binding.","evidence":"Genome-wide CRISPR screen in SPPL3-deficient cells, mass spectrometry of N-glycans, and NK cytotoxicity assays with N-glycan maturation inhibition","pmids":["38619967"],"confidence":"High","gaps":["NK receptors physically occluded by poly-LacNAc not individually mapped"]},{"year":2024,"claim":"Broadened the functional scope to hemostasis and to glyco-engineering tool use, linking B3GNT2 to endothelial FVIII/VWF secretion and demonstrating tolerance of unnatural UDP-GlcNAc donors.","evidence":"siRNA knockdown in human endothelial cells with FVIII/VWF release readouts; in vitro assays with azide/alkyne/diazirine UDP-GlcNAc analogs and cell-surface labeling","pmids":["38320121","38394345"],"confidence":"Medium","gaps":["Mechanism connecting B3GNT2 glycosylation to FVIII/VWF secretory pathway not defined","Specific glycoprotein substrates in endothelial cells unidentified"]},{"year":2025,"claim":"Implicated B3GNT2 in sensory neurobiology, identifying it as a candidate effector of nociceptor sensitization induced by NGF/PKC.","evidence":"Deep visual proteomics and functional knockdown in cultured nociceptive neurons with a mechanical sensitization assay","pmids":["41965357"],"confidence":"Medium","gaps":["Glycoprotein substrates mediating sensitization not identified","In vivo pain relevance not established; single study"]},{"year":null,"claim":"How B3GNT2 substrate selection is governed at the level of specific glycoprotein targets across tissues, and how the B3GNT2–B3GNT8 heterocomplex is structurally organized and regulated, remain open.","evidence":"No timeline study resolves target-level selectivity or the heterocomplex architecture","pmids":[],"confidence":"Medium","gaps":["No structure of the active heterocomplex","Determinants of target glycoprotein choice in vivo unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,1,8,9]}],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,1,8]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[4,10,13]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[12]}],"complexes":["B3GNT2–B3GNT8 heterocomplex"],"partners":["B3GNT8","GCNT2","EGFR","LRP6"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NY97","full_name":"N-acetyllactosaminide beta-1,3-N-acetylglucosaminyltransferase 2","aliases":["Beta-1,3-N-acetylglucosaminyltransferase 1","BGnT-1","Beta-1,3-Gn-T1","Beta3Gn-T1","Beta-1,3-galactosyltransferase 7","Beta-1,3-GalTase 7","Beta3Gal-T7","Beta3GalT7","b3Gal-T7","Beta-3-Gx-T7","UDP-Gal:beta-GlcNAc beta-1,3-galactosyltransferase 7","UDP-GlcNAc:betaGal beta-1,3-N-acetylglucosaminyltransferase 2","BGnT-2","Beta-1,3-Gn-T2","Beta-1,3-N-acetylglucosaminyltransferase 2","Beta3Gn-T2","UDP-galactose:beta-N-acetylglucosamine beta-1,3-galactosyltransferase 7"],"length_aa":397,"mass_kda":46.0,"function":"Beta-1,3-N-acetylglucosaminyltransferase involved in the synthesis of poly-N-acetyllactosamine. Catalyzes the initiation and elongation of poly-N-acetyllactosamine chains. Shows a marked preference for Gal(beta1-4)Glc(NAc)-based acceptors (PubMed:9892646). Probably constitutes the main polylactosamine synthase","subcellular_location":"Golgi apparatus membrane","url":"https://www.uniprot.org/uniprotkb/Q9NY97/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/B3GNT2","classification":"Not Classified","n_dependent_lines":70,"n_total_lines":1208,"dependency_fraction":0.057947019867549666},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CANX","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/B3GNT2","total_profiled":1310},"omim":[{"mim_id":"615357","title":"BETA-1,3-GALACTOSYLTRANSFERASE 8; B3GNT8","url":"https://www.omim.org/entry/615357"},{"mim_id":"615291","title":"BETA-1,3-GALACTOSYLTRANSFERASE 6; B3GALT6","url":"https://www.omim.org/entry/615291"},{"mim_id":"605864","title":"BETA-1,3-N-ACETYLGLUCOSAMINYLTRANSFERASE 4; B3GNT4","url":"https://www.omim.org/entry/605864"},{"mim_id":"605863","title":"BETA-1,3-N-ACETYLGLUCOSAMINYLTRANSFERASE 3; B3GNT3","url":"https://www.omim.org/entry/605863"},{"mim_id":"605581","title":"BETA-1,3-N-ACETYLGLUCOSYAMINYLTRANSFERASE 2; B3GNT2","url":"https://www.omim.org/entry/605581"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/B3GNT2"},"hgnc":{"alias_symbol":["B3GNT-2","BETA3GNT","B3GN-T2","B3GN-T1"],"prev_symbol":["B3GNT1"]},"alphafold":{"accession":"Q9NY97","domains":[{"cath_id":"-","chopping":"57-121","consensus_level":"medium","plddt":85.9285,"start":57,"end":121},{"cath_id":"3.90.550.50","chopping":"141-394","consensus_level":"high","plddt":97.9359,"start":141,"end":394}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NY97","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NY97-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NY97-F1-predicted_aligned_error_v6.png","plddt_mean":91.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=B3GNT2","jax_strain_url":"https://www.jax.org/strain/search?query=B3GNT2"},"sequence":{"accession":"Q9NY97","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NY97.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NY97/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NY97"}},"corpus_meta":[{"pmid":"11821425","id":"PMC_11821425","title":"Molecular cloning and characterization of a novel UDP-GlcNAc:GalNAc-peptide beta1,3-N-acetylglucosaminyltransferase (beta 3Gn-T6), an enzyme synthesizing the core 3 structure of O-glycans.","date":"2002","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11821425","citation_count":132,"is_preprint":false},{"pmid":"35338135","id":"PMC_35338135","title":"CRISPR activation screen identifies BCL-2 proteins and B3GNT2 as drivers of cancer resistance to T cell-mediated cytotoxicity.","date":"2022","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/35338135","citation_count":98,"is_preprint":false},{"pmid":"11283017","id":"PMC_11283017","title":"Molecular cloning and characterization of UDP-GlcNAc:lactosylceramide beta 1,3-N-acetylglucosaminyltransferase (beta 3Gn-T5), an essential enzyme for the expression of HNK-1 and Lewis X epitopes on glycolipids.","date":"2001","source":"The Journal of biological 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The protein is a type II transmembrane polypeptide structurally related to β1,3-galactosyltransferases, sharing conserved amino acid motifs despite inverted donor/acceptor specificities.\",\n      \"method\": \"In vitro enzyme assay with defined acceptor substrates; substrate specificity panel; cDNA cloning and recombinant expression\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro enzymatic reconstitution with substrate specificity panel; foundational characterization replicated by subsequent studies\",\n      \"pmids\": [\"9892646\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Mouse B3GNT2 ortholog is a type II membrane protein localized to the Golgi apparatus, with enzyme activity preferring Gal(β1-4)Glc(NAc) acceptors; proton NMR confirmed incorporation of GlcNAc in β1,3 linkage to terminal Gal. The human gene maps to chromosome 2p15.\",\n      \"method\": \"Enzyme assay; NMR analysis of product; subcellular fractionation/localization; Northern blot\",\n      \"journal\": \"Glycoconjugate journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro enzymatic activity confirmed by NMR; Golgi localization by direct experiment; consistent with human gene characterization\",\n      \"pmids\": [\"11511811\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"B3GNT2 and B3GNT8 form a heterocomplex that enhances enzymatic activity: when the two soluble recombinant enzymes are mixed, the Vmax/Km value is 9.3-fold higher than B3GNT2 alone and 160-fold higher than B3GNT8 alone. Both enzymes share similar substrate specificity, preferring tetraantennary N-glycans and 2,6-branched triantennary glycans. Gel filtration confirmed formation of a heterocomplex of ~110-210 kDa.\",\n      \"method\": \"In vitro enzyme activity assay of recombinant proteins; gel filtration chromatography to detect complex formation\",\n      \"journal\": \"Glycobiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with kinetic analysis and physical complex detection by gel filtration; single lab but two orthogonal methods\",\n      \"pmids\": [\"15917431\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"N-glycosylation of B3GNT2 is required for enzymatic activity and secretion: four of five potential N-glycosylation sites are occupied. N-glycosylation at Asn219 is necessary for beta3GnT activity; N-glycosylation at Asn127 and Asn219 is critical for efficient protein secretion. The N-terminal region (stem region) is also important for maintaining active protein structure, as truncation of amino acids 1-82 abolishes activity.\",\n      \"method\": \"Site-directed mutagenesis of N-glycosylation sites; tunicamycin inhibition; truncation analysis; baculovirus expression system\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis combined with pharmacological inhibition and truncation in a single study, two orthogonal approaches\",\n      \"pmids\": [\"15737642\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"B3GNT2 is the major poly-N-acetyllactosamine (polylactosamine) synthase in vivo. B3gnt2-knockout mice show markedly reduced polylactosamine on N-glycans across tissues. Polylactosamine is present on immune co-stimulatory molecules CD28 and CD19; B3gnt2-/- T cells show hyperactivation (increased Ca2+ flux and proliferation) upon anti-CD3ε/CD28 stimulation, and B3gnt2-/- B cells show hyperproliferation upon BCR stimulation, indicating polylactosamine synthesized by B3GNT2 normally suppresses lymphocyte activation.\",\n      \"method\": \"Knockout mouse model; flow cytometry; LEL lectin-blotting; glycan analysis by metabolic labeling; lectin microarray; Ca2+ flux assay; proliferation assay\",\n      \"journal\": \"Methods in enzymology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO mouse with multiple orthogonal readouts linking B3GNT2-dependent polylactosamine on CD28/CD19 to immune suppression\",\n      \"pmids\": [\"20816167\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"B3GNT2 co-immunoprecipitates with EGFR in H7721 hepatocellular carcinoma cells, identifying EGFR as a B3GNT2-targeting protein. Polylactosamine on EGFR is increased by EGF treatment and decreased by ATRA, correlating with altered B3GNT2 expression.\",\n      \"method\": \"Co-immunoprecipitation; RT-PCR for enzyme expression; lectin staining\",\n      \"journal\": \"Asian Pacific journal of cancer prevention\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP experiment in one cancer cell line, single lab, no mutagenesis or functional rescue\",\n      \"pmids\": [\"25605193\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Co-expression of B3GNT2 and GCNT2 (β1,6-branching glycosyltransferase) in HEK293T cells produces high levels of poly-N-acetyllactosamine (PLN) on the cell surface and on adenylyl cyclase 3, demonstrating cooperative function: GCNT2 generates β1,6-branches that are subsequently extended by B3GNT2 to generate PLN chains.\",\n      \"method\": \"Co-transfection of HEK293T cells; flow cytometry for cell-surface PLN; immunoprecipitation of adenylyl cyclase 3 with lectin detection\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain-of-function co-expression with defined molecular readout in cell culture; single lab\",\n      \"pmids\": [\"24105809\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Mutations in B3GNT2 identified in colorectal cancer cell lines markedly alter protein localization, post-translational modification, and/or encoded enzymatic activities, and affect migratory potential of colon carcinoma cells, indicating these are functionally deleterious mutations contributing to aberrant glycosylation in CRC.\",\n      \"method\": \"Targeted re-sequencing; biochemical characterization of wild-type vs. mutant glycosyltransferases (localization, PTM, enzymatic activity assays); migration assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal biochemical assays characterizing mutant vs. wild-type protein; single lab\",\n      \"pmids\": [\"27004849\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Crystal structures of human B3GNT2 were determined in unliganded, donor substrate (UDP-GlcNAc)-bound, acceptor substrate-bound, and product-bound states (1.85–2.35 Å resolution). Kinetic studies show transglycosylation follows a sequential mechanism. Critical residues for donor and acceptor recognition and catalysis were identified; mutations of invariant residues impair B3GNT2 activity in cell assays. B3GNT2 contains a novel N-terminal helical domain that stabilizes the catalytic domain and may distinguish among acceptor substrates.\",\n      \"method\": \"X-ray crystallography (5 structures); kinetic assays; site-directed mutagenesis with cell-based activity assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures in multiple states plus mutagenesis plus kinetic analysis in a single rigorous study\",\n      \"pmids\": [\"33158990\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Crystal structures of human B3GNT2 in complex with UDP:Mg2+ and with UDP:Mg2+ plus the acceptor lacto-N-neotetraose reveal: (1) B3GNT2 uses the GT-A fold with a DxD motif coordinating Mg2+ for UDP-GlcNAc donor binding; (2) the acceptor binding site contacts only the terminal Galβ(1,4)-GlcNAcβ(1,3)- disaccharide, explaining specificity for both N- and O-glycan acceptors; (3) modeling supports a direct displacement inverting catalytic mechanism.\",\n      \"method\": \"X-ray crystallography (donor-bound and donor+acceptor-bound complexes); structural modeling\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — independent structural study replicating and extending the active site and mechanism findings from PMID:33158990\",\n      \"pmids\": [\"33229435\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CRISPR activation screen identified B3GNT2 overexpression as conferring resistance to T cell-mediated cytotoxicity in melanoma cells and mouse xenografts. Mechanistically, B3GNT2 (a poly-N-acetyllactosamine synthase) targets >10 ligands and receptors on the tumor cell surface, disrupting interactions between tumor cells and T cells and reducing T cell activation.\",\n      \"method\": \"Genome-scale CRISPR activation screen; overexpression validation in multiple cancer cell types; mouse xenograft models; T cell cytotoxicity assays; analysis of tumor-T cell interactions\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — gain-of-function screen validated in multiple cancer cell types and in vivo models, with mechanistic follow-up on immune evasion targets\",\n      \"pmids\": [\"35338135\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Mutagenesis of B3GNT2 hydrophobic core residue T336I increases catalytic efficiency by modulating the conformational occupancy of the catalytic base between 'D-in' and acceptor-accessible 'D-out' conformations, as demonstrated by experimental mutational analysis and molecular dynamics simulations.\",\n      \"method\": \"Site-directed mutagenesis; molecular dynamics simulations; enzymatic activity assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis with kinetic characterization and MD simulation; single lab study\",\n      \"pmids\": [\"35780833\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"B3GNT2 promotes extension of polylactosamine chains at multiple N-glycans on the Wnt co-receptor LRP6, enhancing LRP6 trafficking to the plasma membrane and promoting Wnt/β-catenin signaling. Both gain-of-function (B3GNT2 overexpression) and loss-of-function evidence support this role.\",\n      \"method\": \"Cell culture-based expression screen; gain-of-function and loss-of-function experiments; glycan analysis of LRP6; cell surface trafficking assay; Wnt/β-catenin reporter assay\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal gain/loss-of-function with biochemical glycan analysis of LRP6; single lab\",\n      \"pmids\": [\"36980204\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"In a secondary CRISPR screen in SPPL3-deficient cells, B3GNT2 was identified as the transferase mediating poly-LacNAc extension on complex N-glycans that underlies resistance to NK cell cytotoxicity. Mass spectrometry confirmed enrichment of N-glycans bearing poly-LacNAc upon SPPL3 loss; inhibiting N-glycan maturation restored NK receptor binding and sensitivity.\",\n      \"method\": \"Genome-wide CRISPR screen; mass spectrometry of N-glycans; NK cytotoxicity assay; N-glycan maturation inhibition\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — functional CRISPR screen validated by mass spectrometry glycan analysis and NK cytotoxicity assays; multiple orthogonal methods\",\n      \"pmids\": [\"38619967\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Silencing of B3GNT2 in human liver endothelial cells (HLECs) decreased release of Factor VIII (FVIII), and silencing of B3GNT2 in human vein endothelial cells decreased release of von Willebrand factor (VWF), demonstrating a functional role for B3GNT2 in FVIII and VWF secretion.\",\n      \"method\": \"siRNA knockdown in human endothelial cells; FVIII and VWF release measurement\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean knockdown with specific protein secretion readout in human primary cells; single study\",\n      \"pmids\": [\"38320121\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"B3GNT2 tolerates modified UDP-GlcNAc donors bearing azide, alkyne, or diazirine groups at the C2-acetamido position for transfer to glycan acceptors (albeit less efficiently than natural UDP-GlcNAc), and can exo-enzymatically install GlcNAz on cell-surface glycans, enabling subsequent extension with B4GalT1 to form LacNAz motifs.\",\n      \"method\": \"In vitro enzyme assay with unnatural nucleotide-sugar substrates; cell-surface glyco-engineering with flow cytometric detection\",\n      \"journal\": \"ACS chemical biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro biochemical assay with synthetic substrates plus cell-based application; single lab\",\n      \"pmids\": [\"38394345\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Functional knockdown of B3GNT2 in nociceptive sensory neurons (which upregulate B3GNT2 after NGF/PKC sensitization) identified B3GNT2 as a potential effector of nociceptor sensitization, linking its glycosyltransferase activity to mechanical pain sensitization.\",\n      \"method\": \"Deep visual proteomics; functional knockdown experiments in cultured nociceptive neurons; mechanical sensitization assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockdown with defined phenotypic readout (mechanical sensitization); novel finding but single study\",\n      \"pmids\": [\"41965357\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"B3GNT2 is a Golgi-resident, type II transmembrane β1,3-N-acetylglucosaminyltransferase (GT-A fold, inverting mechanism) that is the major poly-N-acetyllactosamine (poly-LacNAc) synthase in mammals: it sequentially transfers GlcNAc in β1,3 linkage onto Galβ1,4GlcNAc-terminating acceptors on both N- and O-glycans, requiring N-glycosylation at Asn219 for activity and cooperating with B3GNT8 (as a heterocomplex) and GCNT2 (which provides β1,6-branches) to elongate poly-LacNAc chains; these long poly-LacNAc chains on immune co-receptors (CD28, CD19) suppress lymphocyte activation, and their presence on tumor cell surfaces disrupts tumor–T cell and tumor–NK cell interactions to promote immune evasion, while B3GNT2-mediated glycosylation of LRP6 also enhances Wnt/β-catenin signaling and modulates FVIII/VWF secretion from endothelial cells.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"B3GNT2 is the major poly-N-acetyllactosamine (poly-LacNAc) synthase in mammals, a Golgi-resident type II transmembrane β1,3-N-acetylglucosaminyltransferase that both initiates and elongates poly-LacNAc by transferring GlcNAc in β1,3 linkage onto Galβ1,4GlcNAc-terminating acceptors, with marked preference for type II (LacNAc) over type 1 or O-glycan core 1 acceptors [#0, #1]. B3gnt2-knockout mice lose the bulk of N-glycan polylactosamine across tissues, establishing it as the principal enzyme generating these chains in vivo [#4]. Crystal structures in unliganded, donor (UDP-GlcNAc)-, acceptor-, and product-bound states show a GT-A fold using a DxD motif to coordinate Mg2+ for donor binding, an acceptor pocket that contacts only the terminal Galβ1,4-GlcNAcβ1,3- disaccharide (rationalizing its dual specificity for N- and O-glycans), and a direct-displacement inverting catalytic mechanism; a novel N-terminal helical domain stabilizes the catalytic domain [#8, #9]. Enzyme function depends on N-glycosylation at Asn219 and on an intact stem region [#3], and the enzyme acts with B3GNT8 as an activity-enhancing heterocomplex and with the β1,6-branching enzyme GCNT2 to build branched poly-LacNAc [#2, #6]. Functionally, B3GNT2-dependent poly-LacNAc decorates immune co-receptors CD28 and CD19 to restrain lymphocyte activation [#4], and its overexpression on tumor cells coats surface ligands and receptors to disrupt tumor–T cell and tumor–NK cell interactions, conferring resistance to T cell and NK cell cytotoxicity and promoting immune evasion [#10, #13]. Beyond immunity, B3GNT2 glycosylates the Wnt co-receptor LRP6 to enhance its plasma-membrane trafficking and Wnt/β-catenin signaling [#12] and contributes to endothelial secretion of Factor VIII and von Willebrand factor [#14].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Established the core enzymatic identity, defining B3GNT2 as a β1,3-N-acetylglucosaminyltransferase that initiates and elongates poly-LacNAc with strict preference for type II LacNAc acceptors.\",\n      \"evidence\": \"cDNA cloning, recombinant expression, and in vitro enzyme assays with a defined acceptor specificity panel\",\n      \"pmids\": [\"9892646\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo physiological substrates not yet defined\", \"Subcellular localization not directly demonstrated in this study\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Confirmed the chemical linkage and Golgi residence, localizing the enzyme to the compartment where N-/O-glycan elongation occurs and verifying β1,3 GlcNAc addition to terminal Gal.\",\n      \"evidence\": \"Enzyme assay with proton NMR of product, subcellular fractionation, and Northern blot in the mouse ortholog\",\n      \"pmids\": [\"11511811\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address regulation of activity or partner enzymes\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Showed the enzyme does not act alone — a B3GNT2–B3GNT8 heterocomplex markedly boosts catalytic efficiency, revealing a regulatory mode of assembly.\",\n      \"evidence\": \"In vitro kinetic assays of recombinant proteins and gel filtration to detect physical complex\",\n      \"pmids\": [\"15917431\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and in vivo prevalence of the heterocomplex not established\", \"Structural basis of complex enhancement unknown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Defined post-translational and structural requirements for activity, showing N-glycosylation at Asn219 and an intact stem region are needed for catalysis and secretion.\",\n      \"evidence\": \"Site-directed mutagenesis of N-glycosylation sites, tunicamycin inhibition, and truncation analysis in baculovirus expression\",\n      \"pmids\": [\"15737642\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which Asn219 glycan supports folding/activity not resolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Demonstrated B3GNT2 is the dominant in vivo poly-LacNAc synthase and linked its product on CD28/CD19 to suppression of lymphocyte activation.\",\n      \"evidence\": \"B3gnt2-knockout mice with lectin blotting, glycan analysis, Ca2+ flux and proliferation assays on T and B cells\",\n      \"pmids\": [\"20816167\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct molecular mechanism linking poly-LacNAc to receptor signaling thresholds not dissected\", \"Other glycoprotein targets in immune cells not enumerated\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Extended the target repertoire by identifying EGFR as a B3GNT2-associated glycoprotein and demonstrating cooperative poly-LacNAc synthesis with the branching enzyme GCNT2.\",\n      \"evidence\": \"Co-immunoprecipitation with EGFR in hepatocarcinoma cells; co-transfection of B3GNT2 and GCNT2 in HEK293T with lectin readout on adenylyl cyclase 3\",\n      \"pmids\": [\"25605193\", \"24105809\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"EGFR association rests on a single Co-IP without reciprocal validation or mutagenesis\", \"Functional consequence of EGFR glycosylation not tested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Connected B3GNT2 sequence variation to disease biology, showing colorectal-cancer mutations alter localization, modification, activity, and cell migration.\",\n      \"evidence\": \"Targeted re-sequencing with biochemical characterization of wild-type versus mutant enzyme plus migration assays\",\n      \"pmids\": [\"27004849\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal contribution of individual mutations to tumor progression in vivo not established\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Provided atomic-resolution mechanism: multiple crystal structures defined the GT-A fold, DxD/Mg2+ donor coordination, a disaccharide-recognizing acceptor pocket explaining dual N-/O-glycan specificity, and an inverting direct-displacement catalysis.\",\n      \"evidence\": \"X-ray crystallography of unliganded, donor-, acceptor-, and product-bound states with kinetics and mutagenesis (two independent studies)\",\n      \"pmids\": [\"33158990\", \"33229435\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of the B3GNT2–B3GNT8 heterocomplex not solved\", \"Conformational dynamics during catalysis only inferred\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined a conformational determinant of catalytic efficiency, showing a hydrophobic-core residue toggles the catalytic base between 'D-in' and acceptor-accessible 'D-out' states.\",\n      \"evidence\": \"Site-directed mutagenesis (T336I), molecular dynamics simulations, and enzymatic assays\",\n      \"pmids\": [\"35780833\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological relevance of the D-in/D-out equilibrium not demonstrated\", \"Single-lab MD-based mechanism\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Established a causal role in tumor immune evasion, showing B3GNT2 overexpression coats multiple surface ligands/receptors with poly-LacNAc to blunt T cell killing.\",\n      \"evidence\": \"Genome-scale CRISPR activation screen, overexpression validation, mouse xenografts, and T cell cytotoxicity/interaction assays\",\n      \"pmids\": [\"35338135\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity and relative contribution of the >10 individual surface targets not fully resolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified a signaling target, showing B3GNT2 extends poly-LacNAc on LRP6 to enhance its surface trafficking and Wnt/β-catenin signaling.\",\n      \"evidence\": \"Expression screen with reciprocal gain/loss-of-function, glycan analysis of LRP6, trafficking and Wnt reporter assays\",\n      \"pmids\": [\"36980204\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether LRP6 glycosylation is direct in vivo and dose-dependent in tissues not established\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Generalized the immune-evasion mechanism to NK cells and to a regulatory axis, placing B3GNT2 downstream of SPPL3 loss as the transferase whose poly-LacNAc blocks NK receptor binding.\",\n      \"evidence\": \"Genome-wide CRISPR screen in SPPL3-deficient cells, mass spectrometry of N-glycans, and NK cytotoxicity assays with N-glycan maturation inhibition\",\n      \"pmids\": [\"38619967\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"NK receptors physically occluded by poly-LacNAc not individually mapped\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Broadened the functional scope to hemostasis and to glyco-engineering tool use, linking B3GNT2 to endothelial FVIII/VWF secretion and demonstrating tolerance of unnatural UDP-GlcNAc donors.\",\n      \"evidence\": \"siRNA knockdown in human endothelial cells with FVIII/VWF release readouts; in vitro assays with azide/alkyne/diazirine UDP-GlcNAc analogs and cell-surface labeling\",\n      \"pmids\": [\"38320121\", \"38394345\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism connecting B3GNT2 glycosylation to FVIII/VWF secretory pathway not defined\", \"Specific glycoprotein substrates in endothelial cells unidentified\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Implicated B3GNT2 in sensory neurobiology, identifying it as a candidate effector of nociceptor sensitization induced by NGF/PKC.\",\n      \"evidence\": \"Deep visual proteomics and functional knockdown in cultured nociceptive neurons with a mechanical sensitization assay\",\n      \"pmids\": [\"41965357\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Glycoprotein substrates mediating sensitization not identified\", \"In vivo pain relevance not established; single study\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How B3GNT2 substrate selection is governed at the level of specific glycoprotein targets across tissues, and how the B3GNT2–B3GNT8 heterocomplex is structurally organized and regulated, remain open.\",\n      \"evidence\": \"No timeline study resolves target-level selectivity or the heterocomplex architecture\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structure of the active heterocomplex\", \"Determinants of target glycoprotein choice in vivo unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 1, 8, 9]},\n      {\"term_id\": \"GO:0016757\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 1, 8]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [4, 10, 13]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [12]}\n    ],\n    \"complexes\": [\"B3GNT2–B3GNT8 heterocomplex\"],\n    \"partners\": [\"B3GNT8\", \"GCNT2\", \"EGFR\", \"LRP6\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}