{"gene":"NEU3","run_date":"2026-06-10T05:19:52","timeline":{"discoveries":[{"year":2000,"finding":"NEU3 encodes a 428-residue human plasma membrane-associated sialidase with a putative transmembrane helix, YRIP motif, and three Asp boxes; expressed in COS7 cells it shows high ganglioside-hydrolyzing sialidase activity (pH optimum 3.8) and localizes to the plasma membrane by immunofluorescence.","method":"cDNA cloning, transient transfection in COS7 cells, sialidase activity assay, immunofluorescence","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct enzymatic characterization with activity assay, substrate specificity, and immunolocalization; foundational identification paper","pmids":["10861246"],"is_preprint":false},{"year":2002,"finding":"NEU3 is enriched in caveolae microdomains and associates directly with caveolin-1 via a caveolin-binding motif; a single amino acid mutation in this motif reduces microdomain recruitment and sialidase activity; caveolin-1 co-elutes with His-tagged NEU3 on affinity chromatography and co-immunoprecipitates with anti-caveolin-1 antibody; cholesterol depletion displaces NEU3 from microdomains and decreases activity, while increased caveolin-1 expression activates NEU3.","method":"Sucrose density gradient fractionation, affinity column chromatography, co-immunoprecipitation, site-directed mutagenesis, beta-cyclodextrin cholesterol depletion, immunoblotting","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods (affinity pulldown, Co-IP, mutagenesis, fractionation) in one study with functional readout","pmids":["12011038"],"is_preprint":false},{"year":2002,"finding":"NEU3 overexpression in human colon cancer cells inhibits apoptosis, accompanied by increased Bcl-2 and decreased caspase expression; NEU3 is downregulated during sodium butyrate-induced differentiation/apoptosis; lactosylceramide, a NEU3 catalytic product, reduces apoptotic cells, suggesting NEU3 promotes survival through ganglioside modulation.","method":"Gene transfection into colon cancer cells, flow cytometry for apoptosis, western blot for Bcl-2/caspase, TLC for gangliosides, sodium butyrate treatment","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — gain-of-function transfection with mechanistic molecular readouts (Bcl-2, caspase), replicated with exogenous lipid addition","pmids":["12149448"],"is_preprint":false},{"year":2006,"finding":"NEU3 overexpression in colon cancer DLD-1 cells increases adhesion to laminins and cell proliferation, but decreases adhesion to fibronectin; on laminin-5, NEU3 stimulates phosphorylation of FAK and ERK, co-immunoprecipitates with integrin β4, recruits Shc and Grb-2 to integrin β4, and promotes phosphorylation of integrin β1 and ILK; GM3 depletion by NEU3 correlates with these bimodal adhesion effects.","method":"Transfection, co-immunoprecipitation with anti-integrin β4 antibody, western blot for phospho-FAK/ERK/integrin β1/ILK, cell adhesion assay, TLC for gangliosides","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP with functional signaling readouts, multiple phosphorylation targets examined, gain-of-function approach with substrate analysis","pmids":["16241905"],"is_preprint":false},{"year":2006,"finding":"EGF stimulation redistributes NEU3 to membrane ruffles where it co-localizes and co-precipitates with activated Rac-1; NEU3 overexpression enhances Rac-1 activation and cell migration, while NEU3 siRNA silencing inhibits Rac-1 activation.","method":"Immunofluorescence, GST-PAK-1 pulldown for activated Rac-1, siRNA knockdown, migration assay","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal gain/loss-of-function with Co-IP of activated Rac-1 and functional migration readout","pmids":["16765317"],"is_preprint":false},{"year":2007,"finding":"Hepatic overexpression of NEU3 via adenoviral vectors improves insulin sensitivity and glucose tolerance in mice through modification of ganglioside composition (increased GM1, markedly reduced GM3 in liver); increases tyrosine phosphorylation of insulin receptor substrate 1 (IRS-1) but not insulin receptor or IRS-2; enhances PPARγ and fetuin expression.","method":"Adenoviral gene delivery in mice, TLC for gangliosides, insulin tolerance test, glucose tolerance test, western blot for phospho-IRS-1","journal":"Metabolism: clinical and experimental","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo gain-of-function with mechanistic molecular readouts (IRS-1 phosphorylation, ganglioside composition) and multiple mouse models","pmids":["17292733"],"is_preprint":false},{"year":2007,"finding":"NEU3 subcellular localization was determined: NEU3 is a peripheral membrane protein associated with the outer leaflet of the plasma membrane (demonstrated by surface biotinylation and carbonate extraction), is also present in a subset of endosomal compartments, is internalized from the plasma membrane and sorted to recycling endosomes, and is hydrophilic as shown by Triton X-114 phase separation.","method":"Selective cell-surface protein biotinylation, carbonate extraction, Triton X-114 phase separation, immunofluorescence, subcellular fractionation","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal biochemical and imaging methods establishing membrane topology and trafficking","pmids":["17708748"],"is_preprint":false},{"year":2008,"finding":"NEU3 silencing in C2C12 myoblasts increases GM3 ganglioside above a critical threshold, causing EGFR inhibition and eventual EGFR down-regulation, which blocks myoblast differentiation and increases apoptosis susceptibility; NEU3 strictly modulates the GM3 content of adjacent cells and is required for myogenic differentiation.","method":"siRNA-mediated NEU3 knockdown, TLC for gangliosides, western blot for EGFR, differentiation assay, apoptosis assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — loss-of-function with defined molecular mechanism (GM3→EGFR inhibition) and functional differentiation/apoptosis readout","pmids":["18945680"],"is_preprint":false},{"year":2008,"finding":"NEU3 silencing in K562 chronic myeloid leukemia cells markedly increases GM3 and other gangliosides, reduces cell growth, shifts cell cycle regulators (decreases cyclin D2 and Myc, increases p21), promotes apoptosis susceptibility, and triggers megakaryocytic differentiation; downstream signaling through PLC-β2, PKC, RAF, ERK1/2, RSK90, and JNK is activated upon NEU3 silencing.","method":"siRNA knockdown, flow cytometry, TLC for gangliosides, RT-PCR, western blot for signaling molecules","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 2 / Moderate — loss-of-function with extensive molecular characterization of downstream signaling and differentiation markers","pmids":["18820643"],"is_preprint":false},{"year":2009,"finding":"NEU3 transgenic mice show significantly increased azoxymethane-induced colonic aberrant crypt foci formation associated with enhanced phosphorylation of EGFR, Akt and ERK, up-regulation of Bcl-xL, reduced apoptosis (assessed by cleaved caspase-3), and decreased GM3 with increased lactosylceramide in colonic mucosa.","method":"Transgenic mouse model, azoxymethane treatment, immunohistochemistry for cleaved caspase-3, western blot for phospho-EGFR/Akt/ERK/Bcl-xL, TLC for gangliosides","journal":"Cancer science","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo gain-of-function (transgenic) with multiple molecular endpoints and histological readout","pmids":["19215228"],"is_preprint":false},{"year":2010,"finding":"Site-directed mutagenesis of recombinant human NEU3 identified key catalytic residues: general acid-base D50 and nucleophilic Y370-E225 pair; NMR spectroscopy confirmed NEU3 acts as a retaining exo-sialidase; residues A160, M87, I105 interact with the N5-acetyl group and E113, Y179, Y181 with the C7-C9 glycerol side-chain of sialic acid; N- or C-terminal truncations >10 residues abolish activity.","method":"Site-directed mutagenesis, in vitro enzymatic assays, NMR spectroscopy, homology modeling","journal":"Glycobiology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro enzymatic assay combined with mutagenesis and NMR structural confirmation, defining catalytic mechanism","pmids":["20511247"],"is_preprint":false},{"year":2011,"finding":"NEU3 overexpression in prostate cancer LNCaP cells induces expression of EGR-1, androgen receptor (AR) and PSA both with and without androgen; this induction is abrogated by PI3K and MAP kinase inhibitors and confirmed by increased AKT and ERK1/2 phosphorylation; NEU3 silencing reduces growth of androgen-independent PC-3 cells in culture and in nude mice xenografts.","method":"siRNA knockdown, forced overexpression, western blot for phospho-AKT/ERK, kinase inhibitors (PI3K, MAPK), xenograft tumor assay","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 2 / Strong — bidirectional (gain + loss of function) with pathway inhibitors and in vivo xenograft validation","pmids":["21681193"],"is_preprint":false},{"year":2011,"finding":"NEU3 substrate recognition requires a hydrophobic aglycone; enzymatic activity is directly dependent on aglycone hydrophobicity but not on features of the ceramide headgroup; azide modifications at C9 or N5-Ac of Neu5Ac are tolerated, but large aryl groups are accepted only at C9 and not at N5-Ac; a two-site recognition model (Neu5Ac binding + hydrophobic aglycone interaction) is proposed.","method":"Electrospray ionization mass spectrometry-based substrate cleavage assay with synthetic trisaccharide substrates","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic assay with systematic synthetic substrate library defining structural requirements","pmids":["21675735"],"is_preprint":false},{"year":2012,"finding":"NEU3 silencing in renal carcinoma cells increases membrane ganglioside content (especially GD1a), up-regulates RAB25 (directing integrins to lysosomes), down-regulates CLIC3 (which recycles integrins to plasma membrane), enhances caveolar endocytosis of β1 integrin, blocks β1 integrin recycling to the plasma membrane, and consequently inhibits EGFR and FAK/AKT signaling.","method":"siRNA knockdown, western blot for RAB25/CLIC3/EGFR/FAK/AKT, flow cytometry for surface integrin, TLC for gangliosides, invasion/adhesion assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — loss-of-function with identification of specific trafficking regulators and multiple signaling readouts","pmids":["23139422"],"is_preprint":false},{"year":2012,"finding":"NEU3 silencing in skeletal muscle C2C12 cells under hypoxia increases apoptosis; NEU3 up-regulation under hypoxia stimulates EGFR signaling which activates HIF-1α, increasing cell survival and proliferation; stable NEU3 overexpression enhances hypoxia resistance while stable silencing increases apoptosis susceptibility.","method":"Stable overexpression and siRNA silencing, western blot for HIF-1α/phospho-EGFR, hypoxia treatment, apoptosis assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — bidirectional genetic manipulation with mechanistic pathway (EGFR→HIF-1α) and functional cell survival readout","pmids":["23209287"],"is_preprint":false},{"year":2014,"finding":"In adult rat PNS sensory axons, axotomy activates Neu3 sialidase via calcium influx that activates P38MAPK, which then activates Neu3; this converts GD1a and GT1b to GM1, which is essential for axon regeneration; externally applied sialidase rescues regeneration in CNS axons where Neu3 is not activated by injury; Neu3 activation further stimulates the ERK pathway.","method":"In vitro and in vivo axotomy models (rat DRG and retinal axons), calcium imaging, pharmacological inhibitors of P38MAPK and Neu3 sialidase, TLC for gangliosides, exogenous sialidase application","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — epistatic pathway defined with pharmacological inhibitors, both in vitro and in vivo, with rescue experiment","pmids":["24523539"],"is_preprint":false},{"year":2014,"finding":"STD NMR with catalytically inactive NEU3(Y370F) confirmed close contacts between the enzyme and both the hydrophobic aglycone and the Neu5Ac residue of GM3-analog substrates; facial recognition of galactose and glucose residues was identified; molecular dynamics simulations corroborated the homology model predictions.","method":"STD NMR spectroscopy with inactive mutant NEU3(Y370F)-MBP fusion protein, molecular dynamics simulations","journal":"Glycobiology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct structural NMR experiment with catalytic mutant defining substrate-enzyme contacts","pmids":["25294388"],"is_preprint":false},{"year":2015,"finding":"Phosphatidic acid (PA) produced by phospholipase D1 (PLD1) directly activates NEU3 sialidase activity 4–5-fold in vitro and promotes its translocation to the cell surface; NEU3 interacts selectively with PA (phospholipid array, liposome co-precipitation, ELISA); PA- and calmodulin-binding sites were mapped to the N-terminal region; EGF induces PLD1 activation concomitant with NEU3 translocation; NEU3-PA interaction promotes cell migration through Ras signaling.","method":"In vitro sialidase activity assay with phospholipids, phospholipid array, liposome co-precipitation, ELISA, confocal microscopy, site-directed mutagenesis of N-terminal fragments, migration assay","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro enzymatic activation with multiple binding assays and mutagenesis identifying interaction sites, linked to functional translocation and migration","pmids":["25678627"],"is_preprint":false},{"year":2015,"finding":"NEU3 (active form but not inactive mutant) co-immunoprecipitates with EGFR and Src kinase; NEU3 activates Src kinase activity; EGFR/Src pathway activation by NEU3 promotes oncogenic transformation (clonogenicity on soft agar, in vivo tumor growth); Src inhibitor PP2 completely suppresses NEU3-mediated clonogenicity; activity-null mutants fail to activate Src or EGFR, indicating ganglioside modulation is required.","method":"Co-immunoprecipitation, Src kinase activity assay, soft agar clonogenicity, nude mouse xenograft, EGFR and Src inhibitors, activity-null mutant comparison","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP of NEU3-EGFR-Src complex, kinase activity assay, pharmacological inhibitors, catalytic mutant control, in vivo validation","pmids":["25803810"],"is_preprint":false},{"year":2015,"finding":"Active NEU3 (not inactive mutant) enhances EGFR activation (hyperphosphorylation) without affecting EGFR mRNA or protein expression; EGFR immunoprecipitated from NEU3-overexpressing cells is desialylated as shown by mass spectrometry and western blot; NEU3 thus activates EGFR both indirectly (via GM3 reduction) and directly (via EGFR desialylation).","method":"Transfection of wild-type vs. inactive mutant NEU3, co-immunoprecipitation, mass spectrometry, western blot for phospho-EGFR","journal":"Glycobiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — catalytic mutant control combined with mass spectrometry evidence for EGFR desialylation and co-immunoprecipitation","pmids":["25922362"],"is_preprint":false},{"year":2015,"finding":"NEU3 silencing in colon cancer HT-29 and HCT116 cells decreases phosphorylation of LRP6 (Wnt co-receptor), reduces β-catenin activation, impairs LRP6 complex formation with GSK3β and Axin, and reduces clonogenicity and in vivo tumor growth; activity-null NEU3 mutant fails to activate Wnt signaling; NEU3 also regulates ERK and Akt phosphorylation via EGFR/Ras.","method":"siRNA knockdown, activity-null mutant, western blot for phospho-LRP6/β-catenin/GSK3β/ERK/Akt, immunoprecipitation for LRP6 complex, soft agar assay, xenograft in NOD-SCID mice","journal":"International journal of cancer","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function and catalytic mutant with pathway complex analysis (LRP6/GSK3β/Axin) and in vivo validation","pmids":["25810027"],"is_preprint":false},{"year":2015,"finding":"NEU3 expression reduces transferrin (Tf) internalization via clathrin-mediated endocytosis (CME); NEU3 decreases internalization of α2-macroglobulin and LDL (other CME ligands) but not cholera toxin β-subunit; NEU3 reduces Tf sorting to early and recycling endosomes and decreases Tf binding at cell surface; NEU3-expressing cells show altered subcellular distribution of clathrin adaptor AP-2 but not clathrin, PtdIns(4,5)P2, or caveolin-1.","method":"Ectopic NEU3 expression, fluorescence-based Tf internalization assay, confocal microscopy for AP-2/clathrin distribution, glycosphingolipid depletion experiments","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — gain-of-function with multiple CME cargoes, mechanistic dissection of AP-2 vs. clathrin, and lipid-depletion control","pmids":["26251452"],"is_preprint":false},{"year":2016,"finding":"NEU3 protein interactors were identified by mass spectrometry in plasma membrane and endosomal compartments; NEU3 localizes dynamically between plasma membrane (high activity) and endosomes (low activity); under appropriate stimuli NEU3 shifts from endosomes to plasma membrane with increased activity; selected interactors were validated by cross-immunoprecipitation.","method":"Mass spectrometry proteomics, cross-immunoprecipitation, subcellular fractionation, enzyme activity assay in fractions","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS-based interactome with selected Co-IP validation and functional activity measurement in subcellular fractions","pmids":["26987901"],"is_preprint":false},{"year":2017,"finding":"Human NEU3 is S-acylated (palmitoylated) on its cytosolic-exposed C-terminal domain; NEU3 behaves like an integral membrane protein (not released by conditions that extract peripheral proteins), with C-terminus exposed to cytosol and another portion exposed extracellularly; in silico analysis and homology modeling indicate no α-helical transmembrane segment, suggesting S-acylation contributes to membrane anchorage.","method":"S-acylation biochemical assay, carbonate extraction, topology probing by protease protection and selective biotinylation, homology modeling","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct biochemical detection of S-acylation combined with topological analysis using multiple orthogonal approaches","pmids":["28646141"],"is_preprint":false},{"year":2017,"finding":"NEU3 overexpression in glioblastoma cells reduces invasion and migration by promoting focal adhesion assembly through reduced calpain-dependent proteolysis; NEU3 silencing elevates calpain activity and GM3 accumulation, and localizes calpain and GM3 to the cell lamellipodium; activity-null NEU3 fails to reduce invasion, indicating ganglioside hydrolysis is required.","method":"Transwell invasion/migration assay, western blot for calpain and focal adhesion proteins, immunofluorescence microscopy, siRNA knockdown and overexpression","journal":"Biochimica et biophysica acta. General subjects","confidence":"High","confidence_rationale":"Tier 2 / Moderate — bidirectional genetic manipulation with mechanistic (calpain activity, focal adhesion) and localization readouts","pmids":["28760640"],"is_preprint":false},{"year":2017,"finding":"NEU3 is associated with the outer leaflet of exosomes secreted by HeLa cells and retains enzymatic activity on the exosome surface; NEU3 localization on exosomes was confirmed by enzyme activity measurements, western blot, and dot blot.","method":"Inducible NEU3 expression in HeLa cells, exosome purification, enzyme activity assay on exosomes, western blot, dot blot","journal":"Biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct biochemical analysis of purified exosomes with enzyme activity confirmation, single lab study","pmids":["29039925"],"is_preprint":false},{"year":2017,"finding":"Murine Neu3 is responsible for GM2 ganglioside catabolism in the mouse brain as a bypass of HEXA deficiency; Hexa-/-Neu3-/- double knockout mice accumulate GM2 ganglioside in brain, develop neurodegeneration, ataxia, and die at 1.5–4.5 months, recapitulating Tay-Sachs disease; Neu3 sialidase converts GM2 to GA2 allowing further processing by β-hexosaminidase B.","method":"Double knockout mouse generation, TLC, mass spectrometry for gangliosides, histology, immunohistochemistry, electron microscopy, behavioral testing","journal":"Experimental neurology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis (double KO) with biochemical (TLC/MS) and pathological (neurodegeneration) validation, multiple orthogonal methods","pmids":["28974375"],"is_preprint":false},{"year":2010,"finding":"Sp1 and Sp3 transcription factors bind the NEU3 gene promoter and regulate its expression; the NEU3 gene has alternative promoters with two clusters of transcription start sites — one preferentially used in brain and another in other tissues; Sp1/Sp3 siRNA knockdown differentially modulates these promoters, increasing brain-type transcription while decreasing transcription from other TSSs.","method":"Oligo-capping for TSS mapping, luciferase reporter assay, electrophoretic mobility-shift assay (EMSA), chromatin immunoprecipitation (ChIP), siRNA knockdown of Sp1/Sp3","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — ChIP, EMSA, and functional reporter assay with siRNA knockdown, multiple orthogonal methods establishing transcriptional regulation","pmids":["20518744"],"is_preprint":false},{"year":2014,"finding":"NEU3 sialidase activity in DRM (lipid raft) and non-DRM membrane compartments differentially modifies ganglioside composition in each compartment; newly synthesized NEU3 associates first with non-DRM, then redistributes to both DRM and non-DRM at steady state; NEU3 is degraded via the proteasomal pathway; NEU3 triggers Akt phosphorylation even without exogenous EGF.","method":"Inducible expression system, density gradient fractionation, TLC for gangliosides, proteasome inhibitor treatment, western blot for phospho-Akt","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — inducible expression with fractionation and ganglioside analysis, single lab with multiple methods","pmids":["24925219"],"is_preprint":false},{"year":2021,"finding":"Mammalian NEU3 neuraminidase is responsible for intestinal desialylation of alkaline phosphatase (IAP) during Salmonella-induced colitis; absence of NEU3 prevents IAP desialylation, prevents LPS-phosphate accumulation, and prevents inflammatory cytokine expression, thereby protecting against severe colitis development.","method":"Neu3 knockout mouse model, intestinal IAP activity assay, LPS-phosphate measurement, cytokine quantification, colitis model","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout establishing causal role, with multiple mechanistic readouts (IAP desialylation, LPS-P, cytokines) in a disease model","pmids":["34266954"],"is_preprint":false},{"year":2022,"finding":"Recombinant active NEU3 (but not catalytically inactive NEU3) is sufficient to induce pulmonary fibrosis and inflammation when administered by oropharyngeal aspiration in mice; NEU3 knockout mice show strongly attenuated bleomycin-induced fibrosis, indicating NEU3 is both necessary and sufficient for pulmonary fibrosis through its enzymatic activity.","method":"Recombinant NEU3 and inactive mutant aspiration, Neu3 knockout mice, bleomycin fibrosis model, histology, BAL fluid analysis","journal":"Respiratory research","confidence":"High","confidence_rationale":"Tier 2 / Strong — necessity demonstrated by KO and sufficiency demonstrated by recombinant protein, with catalytic mutant control, in an in vivo model","pmids":["35999554"],"is_preprint":false},{"year":2022,"finding":"NEU3 (but not NEU1, NEU2, or NEU4) primes human neutrophils: extracellular NEU3 induces amoeboid morphology, redistributes primed neutrophil markers CD11b, CD18, and CD66a to the cell cortex, decreases CD43 and CD62-L at cortex, and increases F-actin content; NEU3 effect depends on its enzymatic activity (blocked by NEU3 inhibitor 2-acetylpyridine) and is associated with cell surface desialylation.","method":"Recombinant NEU3 incubation with human neutrophils, flow cytometry, confocal microscopy for F-actin and surface markers, pharmacological inhibition with 2-acetylpyridine","journal":"Journal of leukocyte biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — isoform-specific comparison (all 4 NEUs tested), enzymatic activity dependence confirmed by inhibitor, multiple cellular readouts","pmids":["35899930"],"is_preprint":false},{"year":2022,"finding":"NEU3 activity influences CD22 cluster size on B cells; NEU3 activity increases lateral mobility of CD22 (measured by single-particle tracking), in contrast to exogenous bacterial neuraminidase; native NEU1 and NEU3 activities influence cellular Ca2+ levels in B cells, supporting a role in B cell activation regulation.","method":"Confocal microscopy for CD22 clustering, single-particle tracking, Ca2+ measurement, pharmacological sialidase inhibition","journal":"Biophysical reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct imaging with particle tracking and functional Ca2+ readout, single lab study with pharmacological inhibitor","pmids":["36425332"],"is_preprint":false},{"year":2023,"finding":"NEU3 acts on GM1 ganglioside to produce GA1 glycolipid in the mouse brain, providing a bypass catabolism route in the absence of β-galactosidase (Glb1); Glb1/Neu3 double KO mice accumulate more GM1 and less GA1 compared to Glb1 single KO, develop more severe neurodegeneration and ataxia with shorter lifespan; mouse NEU3 converts GM1 to GA1 more efficiently than human NEU3.","method":"Double knockout mouse generation, lipidomics (TLC, mass spectrometry), behavioral testing, neuropathology, interspecies enzyme activity comparison","journal":"Journal of lipid research","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis with double KO, biochemical substrate analysis, interspecies functional comparison with multiple outcome measures","pmids":["37871851"],"is_preprint":false},{"year":2020,"finding":"Induced NEU3 overexpression in primary human cardiac fibroblasts reduces ganglioside GM3 content and significantly reduces TGF-β signaling pathway activation, ultimately decreasing collagen I deposition; NEU3 acts as an inhibitor of cardiac fibroblast activation through GM3 modulation.","method":"Forced NEU3 overexpression in primary human cardiac fibroblasts, TLC for gangliosides, western blot for TGF-β pathway components, collagen I measurement","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain-of-function in primary cells with mechanistic pathway readout (TGF-β signaling), single lab single study","pmids":["32869836"],"is_preprint":false},{"year":2025,"finding":"TGF-β1 rapidly increases NEU3 protein levels (within 5 minutes) in human lung fibroblasts through increased translation (not transcription); the RNA helicase DDX3 mediates NEU3 translation; TGF-β1 induces DDX3 dephosphorylation within 2 minutes; DDX3 inhibitors block rapid NEU3 upregulation; NEU3 activates latent TGF-β1 by cleaving sialic acid from the LAP peptide, creating a positive feedback loop; NEU3 inhibitors block this feedback loop.","method":"Time-course protein expression, transcription/translation inhibitor experiments, DDX3 inhibitors, phosphorylation analysis, TGF-β1 activation assay, NEU3 inhibitors","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal approaches (inhibitors, time-course, phosphorylation) in a preprint; mechanism not yet peer-reviewed","pmids":["bio_10.1101_2025.10.16.682941"],"is_preprint":true}],"current_model":"NEU3 is a plasma membrane-associated, S-acylated peripheral membrane protein and retaining exo-sialidase (catalytic residues D50, Y370, E225) that specifically hydrolyzes gangliosides, localizes to caveolin-rich lipid raft microdomains via a caveolin-binding motif, is activated by phosphatidic acid produced by PLD1 and by calcium/P38MAPK signaling, traffics dynamically between the plasma membrane (high activity) and recycling endosomes (low activity), and regulates transmembrane signaling by desialylating gangliosides and directly desialylating receptors such as EGFR—thereby modulating EGFR/Src/Ras/ERK/AKT, Wnt/LRP6/β-catenin, integrin/FAK, and TGF-β pathways to control cell proliferation, apoptosis resistance, differentiation, migration, axon regeneration, immune cell function, and fibrosis."},"narrative":{"mechanistic_narrative":"NEU3 is a plasma membrane-associated, ganglioside-specific exo-sialidase that governs cell signaling by remodeling the glycosphingolipid composition of membrane microdomains [PMID:10861246, PMID:12149448]. It is a retaining exo-sialidase whose catalytic mechanism depends on a general acid-base aspartate (D50) and a nucleophilic Tyr370-Glu225 pair, and which recognizes substrates through a two-site model combining Neu5Ac binding with an obligatory hydrophobic aglycone interaction [PMID:20511247, PMID:21675735, PMID:25294388]. Rather than spanning the bilayer, NEU3 anchors to the outer leaflet of the plasma membrane as a peripheral/S-acylated protein that concentrates in caveolin-1-rich lipid raft microdomains and cycles dynamically between the surface (high activity) and recycling endosomes (low activity) [PMID:12011038, PMID:17708748, PMID:28646141, PMID:26987901]. Its enzymatic activity is acutely tuned by the local lipid environment and signaling state—activated by phosphatidic acid generated by PLD1, which also drives surface translocation, and by calcium/P38MAPK signaling in injured axons [PMID:25678627, PMID:24523539]. By hydrolyzing gangliosides such as GM3, and by directly desialylating EGFR, NEU3 amplifies receptor signaling through EGFR/Src/Ras/ERK/AKT, Wnt/LRP6/β-catenin, and integrin/FAK axes to promote proliferation, apoptosis resistance, adhesion, and migration [PMID:25803810, PMID:25922362, PMID:25810027, PMID:16241905, PMID:23139422]. This signaling output translates into tissue-level roles: NEU3 promotes colon and prostate tumorigenesis and apoptosis resistance [PMID:12149448, PMID:19215228, PMID:21681193], drives myogenic and megakaryocytic differentiation decisions via the GM3-EGFR threshold [PMID:18945680, PMID:18820643], enables axon regeneration by converting complex gangliosides to GM1 [PMID:24523539], and modulates immune cell function and fibrosis [PMID:35899930, PMID:35999554]. NEU3 also serves a catabolic bypass role in vivo, converting GM2 to GA2 and GM1 to GA1 in the brain to relieve ganglioside accumulation when lysosomal hydrolases are deficient [PMID:28974375, PMID:37871851], and it desialylates intestinal alkaline phosphatase to potentiate colitis [PMID:34266954]. NEU3 transcription is controlled by Sp1/Sp3 acting on tissue-specific alternative promoters [PMID:20518744].","teleology":[{"year":2000,"claim":"Establishing that the human gene encodes a plasma membrane sialidase with ganglioside specificity defined NEU3 as a candidate regulator of membrane glycolipids rather than a lysosomal catabolic enzyme.","evidence":"cDNA cloning and transient expression in COS7 cells with sialidase activity assay and immunofluorescence","pmids":["10861246"],"confidence":"High","gaps":["Membrane topology and anchoring mechanism unresolved","No catalytic residues defined","Physiological substrates in vivo not established"]},{"year":2002,"claim":"Localizing NEU3 to caveolin-1-rich microdomains and showing direct caveolin-1 association and cholesterol dependence explained how the enzyme is spatially organized to act on raft gangliosides and revealed its activity is microdomain-regulated.","evidence":"Sucrose gradient fractionation, affinity pulldown, Co-IP, caveolin-binding-motif mutagenesis, and cholesterol depletion in cells","pmids":["12011038"],"confidence":"High","gaps":["Whether caveolin-1 directly stimulates catalysis or only recruits NEU3 unclear","Membrane anchorage chemistry still undefined"]},{"year":2002,"claim":"Demonstrating that NEU3 overexpression blocks apoptosis via Bcl-2 induction and that its product lactosylceramide is protective linked ganglioside hydrolysis to cancer cell survival.","evidence":"Gain-of-function transfection in colon cancer cells with apoptosis flow cytometry, Bcl-2/caspase blots, and exogenous lipid rescue","pmids":["12149448"],"confidence":"High","gaps":["Receptor/signaling intermediates between ganglioside change and Bcl-2 not defined","Endogenous loss-of-function not tested"]},{"year":2006,"claim":"Connecting NEU3 to integrin/FAK/ERK signaling and Rac-1 activation showed it converts ganglioside remodeling into adhesion and migration outputs.","evidence":"Co-IP with integrin β4, phospho-blots, adhesion assays, and GST-PAK pulldown of activated Rac-1 with reciprocal siRNA/overexpression","pmids":["16241905","16765317"],"confidence":"High","gaps":["Whether integrins are directly desialylated vs. modulated by ambient GM3 not distinguished","Spatial coordination with EGFR signaling unresolved"]},{"year":2007,"claim":"Defining NEU3 as a hydrophilic peripheral protein on the outer plasma membrane leaflet that recycles through endosomes clarified its unusual topology and trafficking itinerary.","evidence":"Surface biotinylation, carbonate extraction, Triton X-114 phase separation, and fractionation/imaging","pmids":["17708748"],"confidence":"High","gaps":["Anchoring mechanism for a hydrophilic protein at the membrane not yet identified","Trafficking machinery driving endosomal recycling unknown"]},{"year":2007,"claim":"In vivo hepatic NEU3 overexpression improving insulin sensitivity through GM3 reduction and IRS-1 phosphorylation established a metabolic role distinct from cancer signaling.","evidence":"Adenoviral delivery in mice with glucose/insulin tolerance tests, ganglioside TLC, and phospho-IRS-1 blots","pmids":["17292733"],"confidence":"High","gaps":["Selectivity for IRS-1 over insulin receptor/IRS-2 mechanistically unexplained","Endogenous hepatic NEU3 role not addressed"]},{"year":2008,"claim":"Loss-of-function in myoblast and leukemia models showed NEU3 sets a GM3-EGFR threshold that gates differentiation and survival decisions, including a non-cell-autonomous effect on neighboring cells.","evidence":"siRNA knockdown with ganglioside TLC, EGFR/signaling blots, and differentiation/apoptosis assays in C2C12 and K562 cells","pmids":["18945680","18820643"],"confidence":"High","gaps":["Mechanism of trans-cellular GM3 modulation unclear","Which signaling branch is causal for each differentiation outcome not isolated"]},{"year":2009,"claim":"NEU3 transgenic mice showing enhanced colon carcinogenesis with EGFR/Akt/ERK hyperactivation provided in vivo evidence that NEU3 is pro-tumorigenic.","evidence":"Azoxymethane-treated transgenic mice with aberrant crypt foci scoring, signaling blots, and ganglioside TLC","pmids":["19215228"],"confidence":"High","gaps":["Causal substrate for EGFR activation in vivo not pinned down","Tumor-cell-intrinsic vs. microenvironmental contributions not separated"]},{"year":2010,"claim":"Defining the catalytic residues and confirming a retaining exo-sialidase mechanism, along with mapping Sp1/Sp3-controlled tissue-specific promoters, provided the enzymatic and transcriptional foundation for interpreting all functional studies.","evidence":"Mutagenesis, in vitro assays, and NMR for catalysis; oligo-capping, EMSA, ChIP, luciferase, and Sp1/Sp3 siRNA for transcription","pmids":["20511247","20518744"],"confidence":"High","gaps":["No experimental crystal structure (homology model only)","Upstream signals controlling promoter choice across tissues unresolved"]},{"year":2012,"claim":"Defining the two-site substrate recognition model (Neu5Ac plus hydrophobic aglycone) explained NEU3's ganglioside selectivity and tolerance to defined chemical modifications.","evidence":"ESI-MS cleavage assays with synthetic trisaccharide substrate library","pmids":["21675735"],"confidence":"High","gaps":["Structural basis of aglycone pocket not directly resolved","Relevance of in vitro tolerances to native membrane substrates unclear"]},{"year":2013,"claim":"Linking NEU3 loss to integrin recycling defects via RAB25/CLIC3 and altered endocytosis revealed it controls membrane receptor availability beyond direct desialylation.","evidence":"siRNA knockdown in renal carcinoma cells with trafficking-protein blots, surface integrin flow cytometry, and invasion assays; Tf/AP-2 endocytosis analysis","pmids":["23139422","26251452"],"confidence":"High","gaps":["How ganglioside change reprograms RAB25/CLIC3/AP-2 mechanistically unknown","Direct vs. indirect effects on endocytic machinery not separated"]},{"year":2014,"claim":"Showing calcium/P38MAPK activation of Neu3 converts complex gangliosides to GM1 and is required for PNS axon regeneration extended NEU3's role to neural repair and provided a therapeutic rescue paradigm.","evidence":"In vitro and in vivo axotomy with calcium imaging, P38MAPK/sialidase inhibitors, ganglioside TLC, and exogenous sialidase rescue; STD NMR substrate-contact mapping","pmids":["24523539","25294388","24925219"],"confidence":"High","gaps":["Direct molecular link from P38MAPK to NEU3 activation undefined","Compartment-specific ganglioside remodeling consequences not fully mapped"]},{"year":2015,"claim":"Identifying phosphatidic acid/PLD1 as a direct activator and translocation signal, and demonstrating NEU3 forms complexes with EGFR/Src and directly desialylates EGFR, integrated NEU3 into an actively regulated oncogenic signaling node acting both via GM3 and via direct receptor modification.","evidence":"In vitro activity with phospholipids, lipid arrays, N-terminal mutagenesis; Co-IP of EGFR/Src, Src kinase assays, mass spectrometry of desialylated EGFR, catalytic-mutant controls, Wnt/LRP6 complex analysis, and xenografts","pmids":["25678627","25803810","25922362","25810027"],"confidence":"High","gaps":["Stoichiometry/kinetics of direct EGFR desialylation in vivo unclear","How PA-binding and caveolin recruitment are coordinated unresolved"]},{"year":2016,"claim":"Mapping plasma membrane vs. endosomal interactomes and confirming activity differs by compartment established that NEU3 function is regulated by stimulus-driven redistribution.","evidence":"Mass spectrometry interactomics with cross-Co-IP validation and fraction activity assays","pmids":["26987901"],"confidence":"Medium","gaps":["Functional roles of most identified interactors untested","Signals triggering endosome-to-surface shift not defined"]},{"year":2017,"claim":"Identifying S-acylation of the cytosolic C-terminus resolved how a protein lacking a transmembrane helix anchors to membranes, and showing NEU3 rides on exosome surfaces revealed a route for intercellular action.","evidence":"S-acylation assay, protease protection/biotinylation topology, homology modeling; exosome purification with surface activity assays","pmids":["28646141","29039925"],"confidence":"High","gaps":["Enzyme(s) mediating NEU3 S-acylation unknown","Physiological importance of exosomal NEU3 in vivo untested"]},{"year":2017,"claim":"Establishing murine Neu3 as a brain catabolic bypass that converts GM2 to GA2 demonstrated a non-signaling, lysosomal-pathway-relieving function with disease relevance to Tay-Sachs.","evidence":"Hexa/Neu3 double-knockout mice with ganglioside TLC/MS, neuropathology, and behavioral testing","pmids":["28974375"],"confidence":"High","gaps":["Subcellular site of this catabolic reaction not pinned down","Human relevance of the bypass uncertain given species enzyme differences"]},{"year":2017,"claim":"Showing NEU3 promotes focal adhesion assembly by restraining calpain-dependent proteolysis in glioblastoma added a context-dependent anti-invasive role mediated by ganglioside hydrolysis.","evidence":"Bidirectional overexpression/siRNA with invasion assays, calpain/focal-adhesion blots, and immunofluorescence; activity-null mutant control","pmids":["28760640"],"confidence":"High","gaps":["Why NEU3 is pro-migratory in some cells but anti-invasive here unresolved","Mechanistic link from GM3 to calpain activity undefined"]},{"year":2021,"claim":"Demonstrating that NEU3 desialylates intestinal alkaline phosphatase to drive LPS-phosphate accumulation and colitis defined a discrete extracellular substrate and disease-promoting mechanism in the gut.","evidence":"Neu3 knockout mice in a Salmonella colitis model with IAP activity, LPS-phosphate, and cytokine measurements","pmids":["34266954"],"confidence":"High","gaps":["Whether IAP desialylation is direct in vivo not fully proven","Generality to other host extracellular glycoproteins unknown"]},{"year":2022,"claim":"Showing NEU3 is necessary and sufficient for pulmonary fibrosis and that it primes neutrophils and modulates B-cell CD22 mobility extended its enzymatic activity to immune regulation and fibrotic disease.","evidence":"Recombinant NEU3 and inactive-mutant aspiration plus Neu3-KO bleomycin model; isoform-specific neutrophil assays with inhibitor; CD22 single-particle tracking and Ca2+ measurement","pmids":["35999554","35899930","36425332"],"confidence":"High","gaps":["Cell-surface substrates mediating neutrophil/B-cell effects not fully identified","Whether fibrosis is driven by the same substrates as inflammation unclear"]},{"year":2023,"claim":"Defining NEU3's GM1-to-GA1 bypass in GM1-gangliosidosis models, with interspecies efficiency differences, refined its catabolic role and underscored mouse-human enzymatic divergence.","evidence":"Glb1/Neu3 double-knockout mice with lipidomics, neuropathology, behavior, and interspecies enzyme comparison","pmids":["37871851"],"confidence":"High","gaps":["Human NEU3 contribution to GM1 catabolism likely smaller and untested in vivo","Therapeutic exploitability unaddressed"]},{"year":2025,"claim":"A proposed TGF-β1–DDX3–NEU3 positive feedback loop, in which NEU3 activates latent TGF-β1 by cleaving sialic acid from LAP, would explain rapid amplification of fibrotic signaling but reverses the anti-fibrotic role seen in cardiac fibroblasts.","evidence":"Time-course translation/transcription inhibitor experiments, DDX3 inhibitors and phosphorylation analysis, TGF-β1 activation and NEU3 inhibitor assays in lung fibroblasts (preprint)","pmids":["bio_10.1101_2025.10.16.682941"],"confidence":"Medium","gaps":["Preprint, not peer-reviewed","Direct desialylation of LAP not biochemically isolated","Opposite TGF-β outcomes in cardiac vs. lung fibroblasts unreconciled"]},{"year":null,"claim":"How NEU3's opposing functions—pro-signaling/pro-tumorigenic versus catabolic-protective and context-dependent anti-fibrotic/anti-invasive—are selected in a given cell and tissue remains unresolved, as does an experimental high-resolution structure.","evidence":"","pmids":[],"confidence":"Low","gaps":["No experimental atomic structure","Determinants switching NEU3 between signaling and catabolic modes unknown","Comprehensive in vivo substrate map of membrane vs. extracellular targets lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[0,10,12,16]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,10]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[17,23]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,6,23]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[6,22]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[25]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[18,19,20,3]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[5,26,33]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[26,29,30,33]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[29,31,32]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[2,7,14]}],"complexes":[],"partners":["CAV1","EGFR","SRC","ITGB4","RAC1","LRP6","PLD1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9UQ49","full_name":"Sialidase-3","aliases":["Ganglioside sialidasedis","Membrane sialidase","N-acetyl-alpha-neuraminidase 3"],"length_aa":428,"mass_kda":48.3,"function":"Exo-alpha-sialidase that catalyzes the hydrolytic cleavage of the terminal sialic acid (N-acetylneuraminic acid, Neu5Ac) of a glycan moiety in the catabolism of glycolipids, glycoproteins and oligosacharides. Displays high catalytic efficiency for gangliosides including alpha-(2->3)-sialylated GD1a and GM3 and alpha-(2->8)-sialylated GD3 (PubMed:10405317, PubMed:10861246, PubMed:11298736, PubMed:12011038, PubMed:15847605, PubMed:20511247, PubMed:28646141). Plays a role in the regulation of transmembrane signaling through the modulation of ganglioside content of the lipid bilayer and by direct interaction with signaling receptors, such as EGFR (PubMed:17334392, PubMed:25922362). Desialylates EGFR and activates downstream signaling in proliferating cells (PubMed:25922362). Contributes to clathrin-mediated endocytosis by regulating sorting of endocytosed receptors to early and recycling endosomes (PubMed:26251452)","subcellular_location":"Cell membrane; Membrane, caveola; Early endosome membrane; Recycling endosome membrane; Lysosome membrane","url":"https://www.uniprot.org/uniprotkb/Q9UQ49/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/NEU3","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/NEU3","total_profiled":1310},"omim":[{"mim_id":"604617","title":"NEURAMINIDASE 3; NEU3","url":"https://www.omim.org/entry/604617"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Vesicles","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/NEU3"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q9UQ49","domains":[{"cath_id":"2.120.10.10","chopping":"22-290_326-413","consensus_level":"medium","plddt":94.1558,"start":22,"end":413}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UQ49","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UQ49-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UQ49-F1-predicted_aligned_error_v6.png","plddt_mean":86.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NEU3","jax_strain_url":"https://www.jax.org/strain/search?query=NEU3"},"sequence":{"accession":"Q9UQ49","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UQ49.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UQ49/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UQ49"}},"corpus_meta":[{"pmid":"12149448","id":"PMC_12149448","title":"Up-regulation of plasma 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NMR.","date":"2014","source":"Glycobiology","url":"https://pubmed.ncbi.nlm.nih.gov/25294388","citation_count":9,"is_preprint":false},{"pmid":"39570922","id":"PMC_39570922","title":"Inhibition of CCl4-induced liver inflammation and fibrosis by a NEU3 inhibitor.","date":"2024","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/39570922","citation_count":8,"is_preprint":false},{"pmid":"21861893","id":"PMC_21861893","title":"Gallus gallus NEU3 sialidase as model to study protein evolution mechanism based on rapid evolving loops.","date":"2011","source":"BMC biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21861893","citation_count":8,"is_preprint":false},{"pmid":"18155174","id":"PMC_18155174","title":"Over-expression of mammalian sialidase NEU3 reduces Newcastle disease virus entry and propagation in COS7 cells.","date":"2007","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/18155174","citation_count":8,"is_preprint":false},{"pmid":"28655817","id":"PMC_28655817","title":"Antibody against Microbial Neuraminidases Recognizes Human Sialidase 3 (NEU3): the Neuraminidase/Sialidase Superfamily Revisited.","date":"2017","source":"mBio","url":"https://pubmed.ncbi.nlm.nih.gov/28655817","citation_count":8,"is_preprint":false},{"pmid":"30466783","id":"PMC_30466783","title":"Overexpression of sialidase NEU3 increases the cellular radioresistance potential of U87MG glioblastoma cells.","date":"2018","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/30466783","citation_count":7,"is_preprint":false},{"pmid":"36425332","id":"PMC_36425332","title":"NEU1 and NEU3 enzymes alter CD22 organization on B cells.","date":"2022","source":"Biophysical 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ST3Gal3 but not Neu3 are associated with Lauren's classification, angiolymphatic invasion and histological grade.","date":"2022","source":"European journal of histochemistry : EJH","url":"https://pubmed.ncbi.nlm.nih.gov/36172711","citation_count":4,"is_preprint":false},{"pmid":"40916664","id":"PMC_40916664","title":"Generation of mice with combined Hexa Gly269Ser KI or KO and Neu3 KO alleles to create new models of GM2 gangliosidoses.","date":"2025","source":"Biology open","url":"https://pubmed.ncbi.nlm.nih.gov/40916664","citation_count":3,"is_preprint":false},{"pmid":"35682772","id":"PMC_35682772","title":"Neu3 Sialidase Activates the RISK Cardioprotective Signaling Pathway during Ischemia and Reperfusion Injury (IRI).","date":"2022","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/35682772","citation_count":1,"is_preprint":false},{"pmid":"39672004","id":"PMC_39672004","title":"Sialidase NEU3 silencing inhibits angiogenesis of EA.hy926 cells by regulating Wnt/β-catenin signaling pathway.","date":"2024","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/39672004","citation_count":1,"is_preprint":false},{"pmid":"37686385","id":"PMC_37686385","title":"Downregulation of Zebrafish Cytosolic Sialidase Neu3.2 Affects Skeletal Muscle Development.","date":"2023","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/37686385","citation_count":0,"is_preprint":false},{"pmid":"40779284","id":"PMC_40779284","title":"Spermatozoal sialidases NEU1 and NEU3 are potential predictors for fertilization rate in IVF: a prospective cohort study.","date":"2025","source":"Journal of assisted reproduction and genetics","url":"https://pubmed.ncbi.nlm.nih.gov/40779284","citation_count":0,"is_preprint":false},{"pmid":"42117319","id":"PMC_42117319","title":"Sialidase Neu3 Induced Sialic Acid Disorder and Promoted Vascular Endothelial Injury Through 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\"cDNA cloning, transient transfection in COS7 cells, sialidase activity assay, immunofluorescence\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct enzymatic characterization with activity assay, substrate specificity, and immunolocalization; foundational identification paper\",\n      \"pmids\": [\"10861246\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"NEU3 is enriched in caveolae microdomains and associates directly with caveolin-1 via a caveolin-binding motif; a single amino acid mutation in this motif reduces microdomain recruitment and sialidase activity; caveolin-1 co-elutes with His-tagged NEU3 on affinity chromatography and co-immunoprecipitates with anti-caveolin-1 antibody; cholesterol depletion displaces NEU3 from microdomains and decreases activity, while increased caveolin-1 expression activates NEU3.\",\n      \"method\": \"Sucrose density gradient fractionation, affinity column chromatography, co-immunoprecipitation, site-directed mutagenesis, beta-cyclodextrin cholesterol depletion, immunoblotting\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods (affinity pulldown, Co-IP, mutagenesis, fractionation) in one study with functional readout\",\n      \"pmids\": [\"12011038\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"NEU3 overexpression in human colon cancer cells inhibits apoptosis, accompanied by increased Bcl-2 and decreased caspase expression; NEU3 is downregulated during sodium butyrate-induced differentiation/apoptosis; lactosylceramide, a NEU3 catalytic product, reduces apoptotic cells, suggesting NEU3 promotes survival through ganglioside modulation.\",\n      \"method\": \"Gene transfection into colon cancer cells, flow cytometry for apoptosis, western blot for Bcl-2/caspase, TLC for gangliosides, sodium butyrate treatment\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — gain-of-function transfection with mechanistic molecular readouts (Bcl-2, caspase), replicated with exogenous lipid addition\",\n      \"pmids\": [\"12149448\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"NEU3 overexpression in colon cancer DLD-1 cells increases adhesion to laminins and cell proliferation, but decreases adhesion to fibronectin; on laminin-5, NEU3 stimulates phosphorylation of FAK and ERK, co-immunoprecipitates with integrin β4, recruits Shc and Grb-2 to integrin β4, and promotes phosphorylation of integrin β1 and ILK; GM3 depletion by NEU3 correlates with these bimodal adhesion effects.\",\n      \"method\": \"Transfection, co-immunoprecipitation with anti-integrin β4 antibody, western blot for phospho-FAK/ERK/integrin β1/ILK, cell adhesion assay, TLC for gangliosides\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP with functional signaling readouts, multiple phosphorylation targets examined, gain-of-function approach with substrate analysis\",\n      \"pmids\": [\"16241905\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"EGF stimulation redistributes NEU3 to membrane ruffles where it co-localizes and co-precipitates with activated Rac-1; NEU3 overexpression enhances Rac-1 activation and cell migration, while NEU3 siRNA silencing inhibits Rac-1 activation.\",\n      \"method\": \"Immunofluorescence, GST-PAK-1 pulldown for activated Rac-1, siRNA knockdown, migration assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal gain/loss-of-function with Co-IP of activated Rac-1 and functional migration readout\",\n      \"pmids\": [\"16765317\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Hepatic overexpression of NEU3 via adenoviral vectors improves insulin sensitivity and glucose tolerance in mice through modification of ganglioside composition (increased GM1, markedly reduced GM3 in liver); increases tyrosine phosphorylation of insulin receptor substrate 1 (IRS-1) but not insulin receptor or IRS-2; enhances PPARγ and fetuin expression.\",\n      \"method\": \"Adenoviral gene delivery in mice, TLC for gangliosides, insulin tolerance test, glucose tolerance test, western blot for phospho-IRS-1\",\n      \"journal\": \"Metabolism: clinical and experimental\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo gain-of-function with mechanistic molecular readouts (IRS-1 phosphorylation, ganglioside composition) and multiple mouse models\",\n      \"pmids\": [\"17292733\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"NEU3 subcellular localization was determined: NEU3 is a peripheral membrane protein associated with the outer leaflet of the plasma membrane (demonstrated by surface biotinylation and carbonate extraction), is also present in a subset of endosomal compartments, is internalized from the plasma membrane and sorted to recycling endosomes, and is hydrophilic as shown by Triton X-114 phase separation.\",\n      \"method\": \"Selective cell-surface protein biotinylation, carbonate extraction, Triton X-114 phase separation, immunofluorescence, subcellular fractionation\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal biochemical and imaging methods establishing membrane topology and trafficking\",\n      \"pmids\": [\"17708748\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"NEU3 silencing in C2C12 myoblasts increases GM3 ganglioside above a critical threshold, causing EGFR inhibition and eventual EGFR down-regulation, which blocks myoblast differentiation and increases apoptosis susceptibility; NEU3 strictly modulates the GM3 content of adjacent cells and is required for myogenic differentiation.\",\n      \"method\": \"siRNA-mediated NEU3 knockdown, TLC for gangliosides, western blot for EGFR, differentiation assay, apoptosis assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with defined molecular mechanism (GM3→EGFR inhibition) and functional differentiation/apoptosis readout\",\n      \"pmids\": [\"18945680\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"NEU3 silencing in K562 chronic myeloid leukemia cells markedly increases GM3 and other gangliosides, reduces cell growth, shifts cell cycle regulators (decreases cyclin D2 and Myc, increases p21), promotes apoptosis susceptibility, and triggers megakaryocytic differentiation; downstream signaling through PLC-β2, PKC, RAF, ERK1/2, RSK90, and JNK is activated upon NEU3 silencing.\",\n      \"method\": \"siRNA knockdown, flow cytometry, TLC for gangliosides, RT-PCR, western blot for signaling molecules\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with extensive molecular characterization of downstream signaling and differentiation markers\",\n      \"pmids\": [\"18820643\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"NEU3 transgenic mice show significantly increased azoxymethane-induced colonic aberrant crypt foci formation associated with enhanced phosphorylation of EGFR, Akt and ERK, up-regulation of Bcl-xL, reduced apoptosis (assessed by cleaved caspase-3), and decreased GM3 with increased lactosylceramide in colonic mucosa.\",\n      \"method\": \"Transgenic mouse model, azoxymethane treatment, immunohistochemistry for cleaved caspase-3, western blot for phospho-EGFR/Akt/ERK/Bcl-xL, TLC for gangliosides\",\n      \"journal\": \"Cancer science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo gain-of-function (transgenic) with multiple molecular endpoints and histological readout\",\n      \"pmids\": [\"19215228\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Site-directed mutagenesis of recombinant human NEU3 identified key catalytic residues: general acid-base D50 and nucleophilic Y370-E225 pair; NMR spectroscopy confirmed NEU3 acts as a retaining exo-sialidase; residues A160, M87, I105 interact with the N5-acetyl group and E113, Y179, Y181 with the C7-C9 glycerol side-chain of sialic acid; N- or C-terminal truncations >10 residues abolish activity.\",\n      \"method\": \"Site-directed mutagenesis, in vitro enzymatic assays, NMR spectroscopy, homology modeling\",\n      \"journal\": \"Glycobiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro enzymatic assay combined with mutagenesis and NMR structural confirmation, defining catalytic mechanism\",\n      \"pmids\": [\"20511247\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"NEU3 overexpression in prostate cancer LNCaP cells induces expression of EGR-1, androgen receptor (AR) and PSA both with and without androgen; this induction is abrogated by PI3K and MAP kinase inhibitors and confirmed by increased AKT and ERK1/2 phosphorylation; NEU3 silencing reduces growth of androgen-independent PC-3 cells in culture and in nude mice xenografts.\",\n      \"method\": \"siRNA knockdown, forced overexpression, western blot for phospho-AKT/ERK, kinase inhibitors (PI3K, MAPK), xenograft tumor assay\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — bidirectional (gain + loss of function) with pathway inhibitors and in vivo xenograft validation\",\n      \"pmids\": [\"21681193\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"NEU3 substrate recognition requires a hydrophobic aglycone; enzymatic activity is directly dependent on aglycone hydrophobicity but not on features of the ceramide headgroup; azide modifications at C9 or N5-Ac of Neu5Ac are tolerated, but large aryl groups are accepted only at C9 and not at N5-Ac; a two-site recognition model (Neu5Ac binding + hydrophobic aglycone interaction) is proposed.\",\n      \"method\": \"Electrospray ionization mass spectrometry-based substrate cleavage assay with synthetic trisaccharide substrates\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic assay with systematic synthetic substrate library defining structural requirements\",\n      \"pmids\": [\"21675735\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"NEU3 silencing in renal carcinoma cells increases membrane ganglioside content (especially GD1a), up-regulates RAB25 (directing integrins to lysosomes), down-regulates CLIC3 (which recycles integrins to plasma membrane), enhances caveolar endocytosis of β1 integrin, blocks β1 integrin recycling to the plasma membrane, and consequently inhibits EGFR and FAK/AKT signaling.\",\n      \"method\": \"siRNA knockdown, western blot for RAB25/CLIC3/EGFR/FAK/AKT, flow cytometry for surface integrin, TLC for gangliosides, invasion/adhesion assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with identification of specific trafficking regulators and multiple signaling readouts\",\n      \"pmids\": [\"23139422\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"NEU3 silencing in skeletal muscle C2C12 cells under hypoxia increases apoptosis; NEU3 up-regulation under hypoxia stimulates EGFR signaling which activates HIF-1α, increasing cell survival and proliferation; stable NEU3 overexpression enhances hypoxia resistance while stable silencing increases apoptosis susceptibility.\",\n      \"method\": \"Stable overexpression and siRNA silencing, western blot for HIF-1α/phospho-EGFR, hypoxia treatment, apoptosis assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — bidirectional genetic manipulation with mechanistic pathway (EGFR→HIF-1α) and functional cell survival readout\",\n      \"pmids\": [\"23209287\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In adult rat PNS sensory axons, axotomy activates Neu3 sialidase via calcium influx that activates P38MAPK, which then activates Neu3; this converts GD1a and GT1b to GM1, which is essential for axon regeneration; externally applied sialidase rescues regeneration in CNS axons where Neu3 is not activated by injury; Neu3 activation further stimulates the ERK pathway.\",\n      \"method\": \"In vitro and in vivo axotomy models (rat DRG and retinal axons), calcium imaging, pharmacological inhibitors of P38MAPK and Neu3 sialidase, TLC for gangliosides, exogenous sialidase application\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — epistatic pathway defined with pharmacological inhibitors, both in vitro and in vivo, with rescue experiment\",\n      \"pmids\": [\"24523539\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"STD NMR with catalytically inactive NEU3(Y370F) confirmed close contacts between the enzyme and both the hydrophobic aglycone and the Neu5Ac residue of GM3-analog substrates; facial recognition of galactose and glucose residues was identified; molecular dynamics simulations corroborated the homology model predictions.\",\n      \"method\": \"STD NMR spectroscopy with inactive mutant NEU3(Y370F)-MBP fusion protein, molecular dynamics simulations\",\n      \"journal\": \"Glycobiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct structural NMR experiment with catalytic mutant defining substrate-enzyme contacts\",\n      \"pmids\": [\"25294388\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Phosphatidic acid (PA) produced by phospholipase D1 (PLD1) directly activates NEU3 sialidase activity 4–5-fold in vitro and promotes its translocation to the cell surface; NEU3 interacts selectively with PA (phospholipid array, liposome co-precipitation, ELISA); PA- and calmodulin-binding sites were mapped to the N-terminal region; EGF induces PLD1 activation concomitant with NEU3 translocation; NEU3-PA interaction promotes cell migration through Ras signaling.\",\n      \"method\": \"In vitro sialidase activity assay with phospholipids, phospholipid array, liposome co-precipitation, ELISA, confocal microscopy, site-directed mutagenesis of N-terminal fragments, migration assay\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro enzymatic activation with multiple binding assays and mutagenesis identifying interaction sites, linked to functional translocation and migration\",\n      \"pmids\": [\"25678627\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"NEU3 (active form but not inactive mutant) co-immunoprecipitates with EGFR and Src kinase; NEU3 activates Src kinase activity; EGFR/Src pathway activation by NEU3 promotes oncogenic transformation (clonogenicity on soft agar, in vivo tumor growth); Src inhibitor PP2 completely suppresses NEU3-mediated clonogenicity; activity-null mutants fail to activate Src or EGFR, indicating ganglioside modulation is required.\",\n      \"method\": \"Co-immunoprecipitation, Src kinase activity assay, soft agar clonogenicity, nude mouse xenograft, EGFR and Src inhibitors, activity-null mutant comparison\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP of NEU3-EGFR-Src complex, kinase activity assay, pharmacological inhibitors, catalytic mutant control, in vivo validation\",\n      \"pmids\": [\"25803810\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Active NEU3 (not inactive mutant) enhances EGFR activation (hyperphosphorylation) without affecting EGFR mRNA or protein expression; EGFR immunoprecipitated from NEU3-overexpressing cells is desialylated as shown by mass spectrometry and western blot; NEU3 thus activates EGFR both indirectly (via GM3 reduction) and directly (via EGFR desialylation).\",\n      \"method\": \"Transfection of wild-type vs. inactive mutant NEU3, co-immunoprecipitation, mass spectrometry, western blot for phospho-EGFR\",\n      \"journal\": \"Glycobiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — catalytic mutant control combined with mass spectrometry evidence for EGFR desialylation and co-immunoprecipitation\",\n      \"pmids\": [\"25922362\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"NEU3 silencing in colon cancer HT-29 and HCT116 cells decreases phosphorylation of LRP6 (Wnt co-receptor), reduces β-catenin activation, impairs LRP6 complex formation with GSK3β and Axin, and reduces clonogenicity and in vivo tumor growth; activity-null NEU3 mutant fails to activate Wnt signaling; NEU3 also regulates ERK and Akt phosphorylation via EGFR/Ras.\",\n      \"method\": \"siRNA knockdown, activity-null mutant, western blot for phospho-LRP6/β-catenin/GSK3β/ERK/Akt, immunoprecipitation for LRP6 complex, soft agar assay, xenograft in NOD-SCID mice\",\n      \"journal\": \"International journal of cancer\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function and catalytic mutant with pathway complex analysis (LRP6/GSK3β/Axin) and in vivo validation\",\n      \"pmids\": [\"25810027\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"NEU3 expression reduces transferrin (Tf) internalization via clathrin-mediated endocytosis (CME); NEU3 decreases internalization of α2-macroglobulin and LDL (other CME ligands) but not cholera toxin β-subunit; NEU3 reduces Tf sorting to early and recycling endosomes and decreases Tf binding at cell surface; NEU3-expressing cells show altered subcellular distribution of clathrin adaptor AP-2 but not clathrin, PtdIns(4,5)P2, or caveolin-1.\",\n      \"method\": \"Ectopic NEU3 expression, fluorescence-based Tf internalization assay, confocal microscopy for AP-2/clathrin distribution, glycosphingolipid depletion experiments\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain-of-function with multiple CME cargoes, mechanistic dissection of AP-2 vs. clathrin, and lipid-depletion control\",\n      \"pmids\": [\"26251452\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"NEU3 protein interactors were identified by mass spectrometry in plasma membrane and endosomal compartments; NEU3 localizes dynamically between plasma membrane (high activity) and endosomes (low activity); under appropriate stimuli NEU3 shifts from endosomes to plasma membrane with increased activity; selected interactors were validated by cross-immunoprecipitation.\",\n      \"method\": \"Mass spectrometry proteomics, cross-immunoprecipitation, subcellular fractionation, enzyme activity assay in fractions\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS-based interactome with selected Co-IP validation and functional activity measurement in subcellular fractions\",\n      \"pmids\": [\"26987901\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Human NEU3 is S-acylated (palmitoylated) on its cytosolic-exposed C-terminal domain; NEU3 behaves like an integral membrane protein (not released by conditions that extract peripheral proteins), with C-terminus exposed to cytosol and another portion exposed extracellularly; in silico analysis and homology modeling indicate no α-helical transmembrane segment, suggesting S-acylation contributes to membrane anchorage.\",\n      \"method\": \"S-acylation biochemical assay, carbonate extraction, topology probing by protease protection and selective biotinylation, homology modeling\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct biochemical detection of S-acylation combined with topological analysis using multiple orthogonal approaches\",\n      \"pmids\": [\"28646141\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"NEU3 overexpression in glioblastoma cells reduces invasion and migration by promoting focal adhesion assembly through reduced calpain-dependent proteolysis; NEU3 silencing elevates calpain activity and GM3 accumulation, and localizes calpain and GM3 to the cell lamellipodium; activity-null NEU3 fails to reduce invasion, indicating ganglioside hydrolysis is required.\",\n      \"method\": \"Transwell invasion/migration assay, western blot for calpain and focal adhesion proteins, immunofluorescence microscopy, siRNA knockdown and overexpression\",\n      \"journal\": \"Biochimica et biophysica acta. General subjects\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — bidirectional genetic manipulation with mechanistic (calpain activity, focal adhesion) and localization readouts\",\n      \"pmids\": [\"28760640\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"NEU3 is associated with the outer leaflet of exosomes secreted by HeLa cells and retains enzymatic activity on the exosome surface; NEU3 localization on exosomes was confirmed by enzyme activity measurements, western blot, and dot blot.\",\n      \"method\": \"Inducible NEU3 expression in HeLa cells, exosome purification, enzyme activity assay on exosomes, western blot, dot blot\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct biochemical analysis of purified exosomes with enzyme activity confirmation, single lab study\",\n      \"pmids\": [\"29039925\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Murine Neu3 is responsible for GM2 ganglioside catabolism in the mouse brain as a bypass of HEXA deficiency; Hexa-/-Neu3-/- double knockout mice accumulate GM2 ganglioside in brain, develop neurodegeneration, ataxia, and die at 1.5–4.5 months, recapitulating Tay-Sachs disease; Neu3 sialidase converts GM2 to GA2 allowing further processing by β-hexosaminidase B.\",\n      \"method\": \"Double knockout mouse generation, TLC, mass spectrometry for gangliosides, histology, immunohistochemistry, electron microscopy, behavioral testing\",\n      \"journal\": \"Experimental neurology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis (double KO) with biochemical (TLC/MS) and pathological (neurodegeneration) validation, multiple orthogonal methods\",\n      \"pmids\": [\"28974375\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Sp1 and Sp3 transcription factors bind the NEU3 gene promoter and regulate its expression; the NEU3 gene has alternative promoters with two clusters of transcription start sites — one preferentially used in brain and another in other tissues; Sp1/Sp3 siRNA knockdown differentially modulates these promoters, increasing brain-type transcription while decreasing transcription from other TSSs.\",\n      \"method\": \"Oligo-capping for TSS mapping, luciferase reporter assay, electrophoretic mobility-shift assay (EMSA), chromatin immunoprecipitation (ChIP), siRNA knockdown of Sp1/Sp3\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — ChIP, EMSA, and functional reporter assay with siRNA knockdown, multiple orthogonal methods establishing transcriptional regulation\",\n      \"pmids\": [\"20518744\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"NEU3 sialidase activity in DRM (lipid raft) and non-DRM membrane compartments differentially modifies ganglioside composition in each compartment; newly synthesized NEU3 associates first with non-DRM, then redistributes to both DRM and non-DRM at steady state; NEU3 is degraded via the proteasomal pathway; NEU3 triggers Akt phosphorylation even without exogenous EGF.\",\n      \"method\": \"Inducible expression system, density gradient fractionation, TLC for gangliosides, proteasome inhibitor treatment, western blot for phospho-Akt\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — inducible expression with fractionation and ganglioside analysis, single lab with multiple methods\",\n      \"pmids\": [\"24925219\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Mammalian NEU3 neuraminidase is responsible for intestinal desialylation of alkaline phosphatase (IAP) during Salmonella-induced colitis; absence of NEU3 prevents IAP desialylation, prevents LPS-phosphate accumulation, and prevents inflammatory cytokine expression, thereby protecting against severe colitis development.\",\n      \"method\": \"Neu3 knockout mouse model, intestinal IAP activity assay, LPS-phosphate measurement, cytokine quantification, colitis model\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout establishing causal role, with multiple mechanistic readouts (IAP desialylation, LPS-P, cytokines) in a disease model\",\n      \"pmids\": [\"34266954\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Recombinant active NEU3 (but not catalytically inactive NEU3) is sufficient to induce pulmonary fibrosis and inflammation when administered by oropharyngeal aspiration in mice; NEU3 knockout mice show strongly attenuated bleomycin-induced fibrosis, indicating NEU3 is both necessary and sufficient for pulmonary fibrosis through its enzymatic activity.\",\n      \"method\": \"Recombinant NEU3 and inactive mutant aspiration, Neu3 knockout mice, bleomycin fibrosis model, histology, BAL fluid analysis\",\n      \"journal\": \"Respiratory research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — necessity demonstrated by KO and sufficiency demonstrated by recombinant protein, with catalytic mutant control, in an in vivo model\",\n      \"pmids\": [\"35999554\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"NEU3 (but not NEU1, NEU2, or NEU4) primes human neutrophils: extracellular NEU3 induces amoeboid morphology, redistributes primed neutrophil markers CD11b, CD18, and CD66a to the cell cortex, decreases CD43 and CD62-L at cortex, and increases F-actin content; NEU3 effect depends on its enzymatic activity (blocked by NEU3 inhibitor 2-acetylpyridine) and is associated with cell surface desialylation.\",\n      \"method\": \"Recombinant NEU3 incubation with human neutrophils, flow cytometry, confocal microscopy for F-actin and surface markers, pharmacological inhibition with 2-acetylpyridine\",\n      \"journal\": \"Journal of leukocyte biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — isoform-specific comparison (all 4 NEUs tested), enzymatic activity dependence confirmed by inhibitor, multiple cellular readouts\",\n      \"pmids\": [\"35899930\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"NEU3 activity influences CD22 cluster size on B cells; NEU3 activity increases lateral mobility of CD22 (measured by single-particle tracking), in contrast to exogenous bacterial neuraminidase; native NEU1 and NEU3 activities influence cellular Ca2+ levels in B cells, supporting a role in B cell activation regulation.\",\n      \"method\": \"Confocal microscopy for CD22 clustering, single-particle tracking, Ca2+ measurement, pharmacological sialidase inhibition\",\n      \"journal\": \"Biophysical reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct imaging with particle tracking and functional Ca2+ readout, single lab study with pharmacological inhibitor\",\n      \"pmids\": [\"36425332\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NEU3 acts on GM1 ganglioside to produce GA1 glycolipid in the mouse brain, providing a bypass catabolism route in the absence of β-galactosidase (Glb1); Glb1/Neu3 double KO mice accumulate more GM1 and less GA1 compared to Glb1 single KO, develop more severe neurodegeneration and ataxia with shorter lifespan; mouse NEU3 converts GM1 to GA1 more efficiently than human NEU3.\",\n      \"method\": \"Double knockout mouse generation, lipidomics (TLC, mass spectrometry), behavioral testing, neuropathology, interspecies enzyme activity comparison\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis with double KO, biochemical substrate analysis, interspecies functional comparison with multiple outcome measures\",\n      \"pmids\": [\"37871851\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Induced NEU3 overexpression in primary human cardiac fibroblasts reduces ganglioside GM3 content and significantly reduces TGF-β signaling pathway activation, ultimately decreasing collagen I deposition; NEU3 acts as an inhibitor of cardiac fibroblast activation through GM3 modulation.\",\n      \"method\": \"Forced NEU3 overexpression in primary human cardiac fibroblasts, TLC for gangliosides, western blot for TGF-β pathway components, collagen I measurement\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain-of-function in primary cells with mechanistic pathway readout (TGF-β signaling), single lab single study\",\n      \"pmids\": [\"32869836\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"TGF-β1 rapidly increases NEU3 protein levels (within 5 minutes) in human lung fibroblasts through increased translation (not transcription); the RNA helicase DDX3 mediates NEU3 translation; TGF-β1 induces DDX3 dephosphorylation within 2 minutes; DDX3 inhibitors block rapid NEU3 upregulation; NEU3 activates latent TGF-β1 by cleaving sialic acid from the LAP peptide, creating a positive feedback loop; NEU3 inhibitors block this feedback loop.\",\n      \"method\": \"Time-course protein expression, transcription/translation inhibitor experiments, DDX3 inhibitors, phosphorylation analysis, TGF-β1 activation assay, NEU3 inhibitors\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal approaches (inhibitors, time-course, phosphorylation) in a preprint; mechanism not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.10.16.682941\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"NEU3 is a plasma membrane-associated, S-acylated peripheral membrane protein and retaining exo-sialidase (catalytic residues D50, Y370, E225) that specifically hydrolyzes gangliosides, localizes to caveolin-rich lipid raft microdomains via a caveolin-binding motif, is activated by phosphatidic acid produced by PLD1 and by calcium/P38MAPK signaling, traffics dynamically between the plasma membrane (high activity) and recycling endosomes (low activity), and regulates transmembrane signaling by desialylating gangliosides and directly desialylating receptors such as EGFR—thereby modulating EGFR/Src/Ras/ERK/AKT, Wnt/LRP6/β-catenin, integrin/FAK, and TGF-β pathways to control cell proliferation, apoptosis resistance, differentiation, migration, axon regeneration, immune cell function, and fibrosis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"NEU3 is a plasma membrane-associated, ganglioside-specific exo-sialidase that governs cell signaling by remodeling the glycosphingolipid composition of membrane microdomains [#0, #2]. It is a retaining exo-sialidase whose catalytic mechanism depends on a general acid-base aspartate (D50) and a nucleophilic Tyr370-Glu225 pair, and which recognizes substrates through a two-site model combining Neu5Ac binding with an obligatory hydrophobic aglycone interaction [#10, #12, #16]. Rather than spanning the bilayer, NEU3 anchors to the outer leaflet of the plasma membrane as a peripheral/S-acylated protein that concentrates in caveolin-1-rich lipid raft microdomains and cycles dynamically between the surface (high activity) and recycling endosomes (low activity) [#1, #6, #23, #22]. Its enzymatic activity is acutely tuned by the local lipid environment and signaling state—activated by phosphatidic acid generated by PLD1, which also drives surface translocation, and by calcium/P38MAPK signaling in injured axons [#17, #15]. By hydrolyzing gangliosides such as GM3, and by directly desialylating EGFR, NEU3 amplifies receptor signaling through EGFR/Src/Ras/ERK/AKT, Wnt/LRP6/\\u03b2-catenin, and integrin/FAK axes to promote proliferation, apoptosis resistance, adhesion, and migration [#18, #19, #20, #3, #13]. This signaling output translates into tissue-level roles: NEU3 promotes colon and prostate tumorigenesis and apoptosis resistance [#2, #9, #11], drives myogenic and megakaryocytic differentiation decisions via the GM3-EGFR threshold [#7, #8], enables axon regeneration by converting complex gangliosides to GM1 [#15], and modulates immune cell function and fibrosis [#31, #30]. NEU3 also serves a catabolic bypass role in vivo, converting GM2 to GA2 and GM1 to GA1 in the brain to relieve ganglioside accumulation when lysosomal hydrolases are deficient [#26, #33], and it desialylates intestinal alkaline phosphatase to potentiate colitis [#29]. NEU3 transcription is controlled by Sp1/Sp3 acting on tissue-specific alternative promoters [#27].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Establishing that the human gene encodes a plasma membrane sialidase with ganglioside specificity defined NEU3 as a candidate regulator of membrane glycolipids rather than a lysosomal catabolic enzyme.\",\n      \"evidence\": \"cDNA cloning and transient expression in COS7 cells with sialidase activity assay and immunofluorescence\",\n      \"pmids\": [\"10861246\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Membrane topology and anchoring mechanism unresolved\", \"No catalytic residues defined\", \"Physiological substrates in vivo not established\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Localizing NEU3 to caveolin-1-rich microdomains and showing direct caveolin-1 association and cholesterol dependence explained how the enzyme is spatially organized to act on raft gangliosides and revealed its activity is microdomain-regulated.\",\n      \"evidence\": \"Sucrose gradient fractionation, affinity pulldown, Co-IP, caveolin-binding-motif mutagenesis, and cholesterol depletion in cells\",\n      \"pmids\": [\"12011038\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether caveolin-1 directly stimulates catalysis or only recruits NEU3 unclear\", \"Membrane anchorage chemistry still undefined\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Demonstrating that NEU3 overexpression blocks apoptosis via Bcl-2 induction and that its product lactosylceramide is protective linked ganglioside hydrolysis to cancer cell survival.\",\n      \"evidence\": \"Gain-of-function transfection in colon cancer cells with apoptosis flow cytometry, Bcl-2/caspase blots, and exogenous lipid rescue\",\n      \"pmids\": [\"12149448\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor/signaling intermediates between ganglioside change and Bcl-2 not defined\", \"Endogenous loss-of-function not tested\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Connecting NEU3 to integrin/FAK/ERK signaling and Rac-1 activation showed it converts ganglioside remodeling into adhesion and migration outputs.\",\n      \"evidence\": \"Co-IP with integrin \\u03b24, phospho-blots, adhesion assays, and GST-PAK pulldown of activated Rac-1 with reciprocal siRNA/overexpression\",\n      \"pmids\": [\"16241905\", \"16765317\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether integrins are directly desialylated vs. modulated by ambient GM3 not distinguished\", \"Spatial coordination with EGFR signaling unresolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defining NEU3 as a hydrophilic peripheral protein on the outer plasma membrane leaflet that recycles through endosomes clarified its unusual topology and trafficking itinerary.\",\n      \"evidence\": \"Surface biotinylation, carbonate extraction, Triton X-114 phase separation, and fractionation/imaging\",\n      \"pmids\": [\"17708748\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Anchoring mechanism for a hydrophilic protein at the membrane not yet identified\", \"Trafficking machinery driving endosomal recycling unknown\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"In vivo hepatic NEU3 overexpression improving insulin sensitivity through GM3 reduction and IRS-1 phosphorylation established a metabolic role distinct from cancer signaling.\",\n      \"evidence\": \"Adenoviral delivery in mice with glucose/insulin tolerance tests, ganglioside TLC, and phospho-IRS-1 blots\",\n      \"pmids\": [\"17292733\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Selectivity for IRS-1 over insulin receptor/IRS-2 mechanistically unexplained\", \"Endogenous hepatic NEU3 role not addressed\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Loss-of-function in myoblast and leukemia models showed NEU3 sets a GM3-EGFR threshold that gates differentiation and survival decisions, including a non-cell-autonomous effect on neighboring cells.\",\n      \"evidence\": \"siRNA knockdown with ganglioside TLC, EGFR/signaling blots, and differentiation/apoptosis assays in C2C12 and K562 cells\",\n      \"pmids\": [\"18945680\", \"18820643\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of trans-cellular GM3 modulation unclear\", \"Which signaling branch is causal for each differentiation outcome not isolated\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"NEU3 transgenic mice showing enhanced colon carcinogenesis with EGFR/Akt/ERK hyperactivation provided in vivo evidence that NEU3 is pro-tumorigenic.\",\n      \"evidence\": \"Azoxymethane-treated transgenic mice with aberrant crypt foci scoring, signaling blots, and ganglioside TLC\",\n      \"pmids\": [\"19215228\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Causal substrate for EGFR activation in vivo not pinned down\", \"Tumor-cell-intrinsic vs. microenvironmental contributions not separated\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defining the catalytic residues and confirming a retaining exo-sialidase mechanism, along with mapping Sp1/Sp3-controlled tissue-specific promoters, provided the enzymatic and transcriptional foundation for interpreting all functional studies.\",\n      \"evidence\": \"Mutagenesis, in vitro assays, and NMR for catalysis; oligo-capping, EMSA, ChIP, luciferase, and Sp1/Sp3 siRNA for transcription\",\n      \"pmids\": [\"20511247\", \"20518744\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No experimental crystal structure (homology model only)\", \"Upstream signals controlling promoter choice across tissues unresolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Defining the two-site substrate recognition model (Neu5Ac plus hydrophobic aglycone) explained NEU3's ganglioside selectivity and tolerance to defined chemical modifications.\",\n      \"evidence\": \"ESI-MS cleavage assays with synthetic trisaccharide substrate library\",\n      \"pmids\": [\"21675735\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of aglycone pocket not directly resolved\", \"Relevance of in vitro tolerances to native membrane substrates unclear\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Linking NEU3 loss to integrin recycling defects via RAB25/CLIC3 and altered endocytosis revealed it controls membrane receptor availability beyond direct desialylation.\",\n      \"evidence\": \"siRNA knockdown in renal carcinoma cells with trafficking-protein blots, surface integrin flow cytometry, and invasion assays; Tf/AP-2 endocytosis analysis\",\n      \"pmids\": [\"23139422\", \"26251452\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How ganglioside change reprograms RAB25/CLIC3/AP-2 mechanistically unknown\", \"Direct vs. indirect effects on endocytic machinery not separated\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showing calcium/P38MAPK activation of Neu3 converts complex gangliosides to GM1 and is required for PNS axon regeneration extended NEU3's role to neural repair and provided a therapeutic rescue paradigm.\",\n      \"evidence\": \"In vitro and in vivo axotomy with calcium imaging, P38MAPK/sialidase inhibitors, ganglioside TLC, and exogenous sialidase rescue; STD NMR substrate-contact mapping\",\n      \"pmids\": [\"24523539\", \"25294388\", \"24925219\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct molecular link from P38MAPK to NEU3 activation undefined\", \"Compartment-specific ganglioside remodeling consequences not fully mapped\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identifying phosphatidic acid/PLD1 as a direct activator and translocation signal, and demonstrating NEU3 forms complexes with EGFR/Src and directly desialylates EGFR, integrated NEU3 into an actively regulated oncogenic signaling node acting both via GM3 and via direct receptor modification.\",\n      \"evidence\": \"In vitro activity with phospholipids, lipid arrays, N-terminal mutagenesis; Co-IP of EGFR/Src, Src kinase assays, mass spectrometry of desialylated EGFR, catalytic-mutant controls, Wnt/LRP6 complex analysis, and xenografts\",\n      \"pmids\": [\"25678627\", \"25803810\", \"25922362\", \"25810027\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry/kinetics of direct EGFR desialylation in vivo unclear\", \"How PA-binding and caveolin recruitment are coordinated unresolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Mapping plasma membrane vs. endosomal interactomes and confirming activity differs by compartment established that NEU3 function is regulated by stimulus-driven redistribution.\",\n      \"evidence\": \"Mass spectrometry interactomics with cross-Co-IP validation and fraction activity assays\",\n      \"pmids\": [\"26987901\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional roles of most identified interactors untested\", \"Signals triggering endosome-to-surface shift not defined\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identifying S-acylation of the cytosolic C-terminus resolved how a protein lacking a transmembrane helix anchors to membranes, and showing NEU3 rides on exosome surfaces revealed a route for intercellular action.\",\n      \"evidence\": \"S-acylation assay, protease protection/biotinylation topology, homology modeling; exosome purification with surface activity assays\",\n      \"pmids\": [\"28646141\", \"29039925\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Enzyme(s) mediating NEU3 S-acylation unknown\", \"Physiological importance of exosomal NEU3 in vivo untested\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Establishing murine Neu3 as a brain catabolic bypass that converts GM2 to GA2 demonstrated a non-signaling, lysosomal-pathway-relieving function with disease relevance to Tay-Sachs.\",\n      \"evidence\": \"Hexa/Neu3 double-knockout mice with ganglioside TLC/MS, neuropathology, and behavioral testing\",\n      \"pmids\": [\"28974375\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Subcellular site of this catabolic reaction not pinned down\", \"Human relevance of the bypass uncertain given species enzyme differences\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Showing NEU3 promotes focal adhesion assembly by restraining calpain-dependent proteolysis in glioblastoma added a context-dependent anti-invasive role mediated by ganglioside hydrolysis.\",\n      \"evidence\": \"Bidirectional overexpression/siRNA with invasion assays, calpain/focal-adhesion blots, and immunofluorescence; activity-null mutant control\",\n      \"pmids\": [\"28760640\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Why NEU3 is pro-migratory in some cells but anti-invasive here unresolved\", \"Mechanistic link from GM3 to calpain activity undefined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrating that NEU3 desialylates intestinal alkaline phosphatase to drive LPS-phosphate accumulation and colitis defined a discrete extracellular substrate and disease-promoting mechanism in the gut.\",\n      \"evidence\": \"Neu3 knockout mice in a Salmonella colitis model with IAP activity, LPS-phosphate, and cytokine measurements\",\n      \"pmids\": [\"34266954\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether IAP desialylation is direct in vivo not fully proven\", \"Generality to other host extracellular glycoproteins unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Showing NEU3 is necessary and sufficient for pulmonary fibrosis and that it primes neutrophils and modulates B-cell CD22 mobility extended its enzymatic activity to immune regulation and fibrotic disease.\",\n      \"evidence\": \"Recombinant NEU3 and inactive-mutant aspiration plus Neu3-KO bleomycin model; isoform-specific neutrophil assays with inhibitor; CD22 single-particle tracking and Ca2+ measurement\",\n      \"pmids\": [\"35999554\", \"35899930\", \"36425332\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cell-surface substrates mediating neutrophil/B-cell effects not fully identified\", \"Whether fibrosis is driven by the same substrates as inflammation unclear\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defining NEU3's GM1-to-GA1 bypass in GM1-gangliosidosis models, with interspecies efficiency differences, refined its catabolic role and underscored mouse-human enzymatic divergence.\",\n      \"evidence\": \"Glb1/Neu3 double-knockout mice with lipidomics, neuropathology, behavior, and interspecies enzyme comparison\",\n      \"pmids\": [\"37871851\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Human NEU3 contribution to GM1 catabolism likely smaller and untested in vivo\", \"Therapeutic exploitability unaddressed\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"A proposed TGF-\\u03b21\\u2013DDX3\\u2013NEU3 positive feedback loop, in which NEU3 activates latent TGF-\\u03b21 by cleaving sialic acid from LAP, would explain rapid amplification of fibrotic signaling but reverses the anti-fibrotic role seen in cardiac fibroblasts.\",\n      \"evidence\": \"Time-course translation/transcription inhibitor experiments, DDX3 inhibitors and phosphorylation analysis, TGF-\\u03b21 activation and NEU3 inhibitor assays in lung fibroblasts (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.10.16.682941\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not peer-reviewed\", \"Direct desialylation of LAP not biochemically isolated\", \"Opposite TGF-\\u03b2 outcomes in cardiac vs. lung fibroblasts unreconciled\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How NEU3's opposing functions—pro-signaling/pro-tumorigenic versus catabolic-protective and context-dependent anti-fibrotic/anti-invasive—are selected in a given cell and tissue remains unresolved, as does an experimental high-resolution structure.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No experimental atomic structure\", \"Determinants switching NEU3 between signaling and catabolic modes unknown\", \"Comprehensive in vivo substrate map of membrane vs. extracellular targets lacking\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [0, 10, 12, 16]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 10]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [17, 23]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 6, 23]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [6, 22]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [25]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [18, 19, 20, 3]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [5, 26, 33]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [26, 29, 30, 33]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [29, 31, 32]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [2, 7, 14]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CAV1\", \"EGFR\", \"SRC\", \"ITGB4\", \"RAC1\", \"LRP6\", \"PLD1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":8,"faith_total":8,"faith_pct":100.0}}