{"gene":"GLB1","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":2008,"finding":"GLB1 pre-mRNA undergoes alternative splicing regulated by SR proteins and the nonsense-mediated decay (NMD) pathway, generating two functional transcripts: the full-length lysosomal β-galactosidase (β-gal) mRNA (all 16 exons) and the elastin-binding protein (EBP) mRNA (skipping exons 3, 4, 6 with exon 5 in a different reading frame). Overexpression of different SR proteins altered the relative proportions of these transcripts in a minigene system, indicating SR proteins as regulators of this alternative splicing event.","method":"Minigene splicing assay, cycloheximide-NMD inhibition, SR protein overexpression in HeLa cells and human fibroblasts","journal":"BMC research notes","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — minigene functional assay with SR protein overexpression and NMD inhibition; single lab, two orthogonal methods","pmids":["19114006"],"is_preprint":false},{"year":2011,"finding":"An alternatively spliced form of GLB1 is expressed on the surface of human choroidal endothelial cells and functions as a receptor for elastin-derived peptides (EDPs). Inhibition of this receptor blocked EDP-induced migration of choroidal endothelial cells, establishing GLB1 as the functional EDP receptor in this context.","method":"RT-PCR for receptor identification, cell migration assay with receptor inhibitors, in vivo mouse EDP injection with electroretinography and microarray","journal":"Matrix biology : journal of the International Society for Matrix Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RT-PCR identification plus functional inhibition assay; single lab, two orthogonal methods","pmids":["22178079"],"is_preprint":false},{"year":2007,"finding":"GLB1-encoded β-galactosidase, on reaching the endosomal-lysosomal compartment, associates with protective protein/cathepsin A (PPCA) and neuraminidase to form the lysosomal multienzyme complex (LMC). Coimmunoprecipitation and Western blotting of patient-derived protein extracts showed that pathogenic mutations in GLB1 alter neuraminidase and PPCA patterns, indicating that disease-causing mutations disrupt the LMC.","method":"Expression of mutant alleles in heterologous cells, coimmunoprecipitation, Western blotting of patient protein extracts","journal":"Journal of lipid research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal coimmunoprecipitation with Western blotting for LMC components; single lab, two orthogonal methods","pmids":["17664528"],"is_preprint":false},{"year":2003,"finding":"The L436F polymorphism in GLB1 acts as a modulating variant: when present in cis with the R201C mutation, it severely reduces residual β-galactosidase activity compared to R201C alone. Expression studies in COS1 cells demonstrated that the R201C/L436F complex allele produces much lower GLB1 activity than R201C alone, establishing a cis-modulating mechanism for GLB1 activity.","method":"COS1 cell transfection expression studies, co-transfection experiments, Western blotting","journal":"Human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — heterologous cell expression with mutagenesis-equivalent allele comparison; single lab, two orthogonal methods","pmids":["12644936"],"is_preprint":false},{"year":2007,"finding":"The p.Arg595Trp variant in GLB1 markedly reduces β-galactosidase activity when expressed in COS-1 cells, establishing it as a pseudodeficiency allele — reducing enzymatic activity without causing clinical disease.","method":"COS-1 cell expression assay for β-galactosidase activity","journal":"Clinical genetics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single heterologous expression assay, single lab, single method","pmids":["17661814"],"is_preprint":false},{"year":2010,"finding":"Phenotype-determining GLB1 alleles were characterized by overexpression of missense mutations in COS-1 cells, and subcellular localization of mutant GLB1 proteins was assessed in patient fibroblasts, revealing that specific mutations impair proper intracellular trafficking and lysosomal delivery of the enzyme.","method":"COS-1 cell overexpression assays, subcellular localization in patient fibroblasts","journal":"Clinical genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — heterologous expression with enzyme activity plus subcellular localization in patient cells; single lab, two orthogonal methods","pmids":["20175788"],"is_preprint":false},{"year":2011,"finding":"Fluorous iminoalditol derivatives of 1-deoxygalactonojirimycin act as competitive inhibitors of GLB1-encoded β-galactosidase and function as pharmacological chaperones: they bind the catalytic site of mutant enzymes, correct their misfolded conformation, normalize intracellular trafficking and lysosomal maturation (shown by Western blot), and restore up to tenfold residual enzyme activity in GM1 gangliosidosis patient fibroblasts.","method":"Enzyme activity assay in patient fibroblasts, Western blot for protein trafficking and lysosomal maturation, competitive inhibition assay","journal":"Journal of inherited metabolic disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — competitive inhibition assay plus Western blot for trafficking; single lab, two orthogonal methods","pmids":["22033734"],"is_preprint":false},{"year":2005,"finding":"A 19-bp duplication in exon 15 of the canine GLB1 gene disrupts a potential exon splicing enhancer (ESE), causing exon 15 skipping in a fraction of transcripts. This produces two mutant mRNAs from the same allele: one retaining exon 15 with a premature termination codon (not subject to NMD due to its last-exon position), and one lacking exon 15 entirely — both predicted to encode truncated, non-functional proteins, causing GM1-gangliosidosis.","method":"Molecular cloning, sequencing of mutant allele, mRNA analysis, ESE prediction analysis","journal":"Genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mRNA analysis plus NMD rule application with mechanistic splice-site disruption; single lab, two orthogonal methods (sequencing + transcript analysis)","pmids":["15944348"],"is_preprint":false},{"year":2022,"finding":"Insertion of a processed pseudogene (NPM1) deep in intron 5 of GLB1 introduces pseudogene-derived splicing regulatory motifs that activate a cryptic exon 36 bp upstream of the integration site, leading to aberrant GLB1 splicing and Morquio B disease. Antisense splice-modulating oligonucleotides (ASMOs) incorporated in modified U7 snRNA blocked the cryptic exon and almost completely restored wild-type splicing in a model cell line.","method":"Whole-genome sequencing, mRNA analysis, minigene co-expression, antisense oligonucleotide splice correction in model cell line","journal":"NPJ genomic medicine","confidence":"High","confidence_rationale":"Tier 1 / Strong — functional minigene assay plus splice rescue by ASMOs, multiple orthogonal methods (WGS, mRNA analysis, minigene, modU7 rescue) in a single rigorous study","pmids":["35882863"],"is_preprint":false},{"year":2015,"finding":"GLB1-encoded lysosomal β-galactosidase accumulates during replicative senescence and therapy-induced senescence in prostate epithelial cells, correlating with senescent morphology and P16/CDKN2A expression. This establishes GLB1 as the molecular origin of senescence-associated β-galactosidase (SA-β-gal) activity.","method":"In vitro replicative senescence of primary prostate epithelial cells, chemotherapy-induced senescence in PCa lines, immunofluorescent staining with quantitative imaging","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro senescence models with immunofluorescent quantification; single lab, two orthogonal experimental systems (replicative and induced senescence)","pmids":["25876105"],"is_preprint":false},{"year":2019,"finding":"GLB1 knockout in human cerebral organoids (via CRISPR/Cas9) causes progressive accumulation of GM1 ganglioside, and microinjection of AAV9-GLB1 vector restores β-galactosidase activity and significantly reduces GM1 ganglioside content, demonstrating that GLB1 encodes the enzyme primarily responsible for GM1 ganglioside degradation in human CNS tissue.","method":"CRISPR/Cas9 GLB1 knockout in human iPSCs, cerebral organoid generation, GM1 ganglioside quantification, AAV9-GLB1 rescue with enzyme activity assay","journal":"Molecular genetics and metabolism reports","confidence":"High","confidence_rationale":"Tier 1 / Strong — genetic knockout + biochemical substrate accumulation + gene rescue with enzyme activity restoration; multiple orthogonal methods in a single rigorous study","pmids":["31534909"],"is_preprint":false},{"year":2024,"finding":"GLB1 knockout in SH-SY5Y human neuronal cells results in loss of β-galactosidase activity and downregulation of NEU1 and CTSA expression, establishing that the GLB1-NEU1-CTSA lysosomal multienzyme complex gene network is functionally interdependent. Knockout also suppressed cell proliferation and invasion.","method":"CRISPR/Cas9 dual-guide knockout, X-gal staining, qPCR, RNA-seq analysis","journal":"Cell biochemistry and function","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR knockout with enzyme activity confirmation plus downstream gene expression analysis; single lab, multiple methods","pmids":["39076066"],"is_preprint":false},{"year":2023,"finding":"Adenine base editing (ABE) of the pathogenic GLB1 c.380G>A (p.Cys127Tyr) variant in patient-derived fibroblasts restores canonical guanine at the target site and rescues synthesis of active β-galactosidase to therapeutic levels, normalizing primary glycoconjugate storage and lysosomal pathology.","method":"CRISPR/Cas-adenine base editing in patient fibroblasts, enzyme activity assay, lysosomal pathology markers, off-target analysis","journal":"The CRISPR journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — base editing with functional rescue demonstrated by enzyme assay and lysosomal markers; single lab, multiple orthogonal readouts","pmids":["36629845"],"is_preprint":false},{"year":2018,"finding":"A novel in-frame deletion (p.Asn490del) in GLB1 alters the catalytic site geometry based on molecular dynamics simulation, causing misalignment of catalytic residues, and enzyme assay in patient leukocytes confirmed ~3% residual β-galactosidase activity, establishing the catalytic importance of residue Asn490.","method":"Molecular dynamics simulation of mutant protein, fluorometric enzyme activity assay in patient leukocytes","journal":"Molecular genetics & genomic medicine","confidence":"Low","confidence_rationale":"Tier 3 / Weak — computational simulation plus single enzyme activity measurement; no in vitro mutagenesis reconstitution","pmids":["30187681"],"is_preprint":false},{"year":2022,"finding":"A Glb1-2A-mCherry (GAC) knock-in reporter in mice shows that GLB1 (lysosomal β-galactosidase) is elevated in tissues of aging mice, with GAC signal linearly correlating with chronological age and exponentially increasing in bleomycin-induced pathological senescence. Senolytic treatment (dasatinib + quercetin) reduced the GAC signal in bleomycin-treated mice, establishing GLB1 as a functional in vivo reporter of systemic senescence.","method":"Knock-in reporter mouse generation, fluorescent signal quantification across ages, bleomycin lung injury model, dasatinib+quercetin senolytic treatment","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — genetic reporter knock-in with functional validation across aging cohort, pathological model, and pharmacological intervention; multiple orthogonal methods in a rigorous study","pmids":["36396643"],"is_preprint":false}],"current_model":"GLB1 encodes lysosomal β-galactosidase, a hydrolase that cleaves β-galactose from GM1 ganglioside and other glycoconjugates within the lysosome; in the lysosome it associates with protective protein/cathepsin A (PPCA) and neuraminidase to form the lysosomal multienzyme complex (LMC). The GLB1 pre-mRNA is alternatively spliced under SR protein regulation to produce either the full-length lysosomal enzyme or an elastin-binding protein (EBP) isoform that localizes to the cell surface and acts as a receptor for elastin-derived peptides. GLB1 is the molecular origin of senescence-associated β-galactosidase (SA-β-gal) activity, with enzyme levels rising progressively during replicative and stress-induced senescence in vivo and in vitro. Pathogenic missense mutations impair enzyme folding, intracellular trafficking, and catalytic activity, and pharmacological chaperones (competitive inhibitors such as iminoalditol derivatives) can correct misfolding and restore lysosomal targeting."},"narrative":{"mechanistic_narrative":"GLB1 encodes lysosomal β-galactosidase, the enzyme primarily responsible for degrading GM1 ganglioside in human CNS tissue; CRISPR knockout in cerebral organoids causes progressive GM1 accumulation that is reversed by AAV9-GLB1 delivery [PMID:31534909]. On reaching the endosomal-lysosomal compartment, the enzyme associates with protective protein/cathepsin A (PPCA/CTSA) and neuraminidase (NEU1) to form the lysosomal multienzyme complex, and this gene network is functionally interdependent—loss of GLB1 downregulates NEU1 and CTSA, and pathogenic GLB1 mutations alter neuraminidase and PPCA patterns [PMID:17664528, PMID:39076066]. GLB1 pre-mRNA is alternatively spliced under SR-protein control to yield either the full-length lysosomal enzyme or an elastin-binding protein (EBP) isoform that is displayed at the cell surface and functions as a receptor for elastin-derived peptides driving choroidal endothelial cell migration [PMID:19114006, PMID:22178079]. The locus is the molecular origin of senescence-associated β-galactosidase activity, with enzyme levels rising during replicative and stress-induced senescence in vitro and increasing with chronological age and pathological senescence in vivo, where the signal is reduced by senolytic treatment [PMID:25876105, PMID:36396643]. Pathogenic missense and in-frame variants impair catalytic-site geometry, enzyme folding, intracellular trafficking, and lysosomal delivery, causing GM1 gangliosidosis and Morquio B disease; misfolding can be corrected by pharmacological chaperones (competitive iminoalditol inhibitors) and the underlying lesions by base editing or splice-modulating oligonucleotides [PMID:20175788, PMID:22033734, PMID:35882863, PMID:36629845, PMID:30187681].","teleology":[{"year":2003,"claim":"Established that GLB1 enzyme activity can be modulated in cis by a second variant, defining a complex-allele mechanism for phenotype severity rather than single-mutation effects.","evidence":"COS1 cell expression of R201C alone versus R201C/L436F complex allele with Western blotting","pmids":["12644936"],"confidence":"Medium","gaps":["Mechanism by which L436F further reduces activity (folding vs catalysis) not resolved","Limited to a single allele combination"]},{"year":2005,"claim":"Demonstrated a splicing-regulatory basis for loss of GLB1 function, showing that disruption of an exon splicing enhancer generates truncated non-functional transcripts and causes GM1-gangliosidosis.","evidence":"Cloning, sequencing and mRNA analysis of a canine GLB1 exon 15 duplication with ESE prediction","pmids":["15944348"],"confidence":"Medium","gaps":["Animal-model allele; human equivalence not tested","Predicted truncated proteins not biochemically characterized"]},{"year":2007,"claim":"Identified GLB1 as a subunit of the lysosomal multienzyme complex with PPCA and neuraminidase and showed disease mutations disrupt complex composition, linking enzyme stability to its partner proteins.","evidence":"Reciprocal coimmunoprecipitation and Western blotting of patient protein extracts plus mutant allele expression","pmids":["17664528"],"confidence":"Medium","gaps":["Stoichiometry and assembly order of the complex not defined","No structural model of the interaction"]},{"year":2007,"claim":"Distinguished pathogenic from benign variation by defining a pseudodeficiency allele that lowers enzyme activity without disease, clarifying genotype interpretation.","evidence":"COS-1 expression assay of p.Arg595Trp for β-galactosidase activity","pmids":["17661814"],"confidence":"Low","gaps":["Single heterologous expression assay, single method","Trafficking and complex assembly not assessed"]},{"year":2008,"claim":"Resolved how a single GLB1 locus produces both a lysosomal hydrolase and a surface elastin-binding protein, showing SR proteins and NMD govern the alternative splicing choice.","evidence":"Minigene splicing assay with SR protein overexpression and cycloheximide-NMD inhibition in HeLa cells and fibroblasts","pmids":["19114006"],"confidence":"Medium","gaps":["Endogenous regulation of the isoform ratio in tissues not measured","Which specific SR proteins act physiologically unknown"]},{"year":2010,"claim":"Connected specific missense mutations to defective intracellular trafficking and lysosomal delivery, establishing mistrafficking as a disease mechanism beyond loss of catalysis.","evidence":"COS-1 overexpression activity assays plus subcellular localization in patient fibroblasts","pmids":["20175788"],"confidence":"Medium","gaps":["Trafficking checkpoints disrupted not pinpointed","Quantitative degree of mislocalization per allele unclear"]},{"year":2011,"claim":"Showed the EBP isoform functions as a cell-surface receptor for elastin-derived peptides driving endothelial migration, giving the non-lysosomal GLB1 product a defined signaling role.","evidence":"RT-PCR identification, migration assay with receptor inhibitors, and in vivo mouse EDP injection","pmids":["22178079"],"confidence":"Medium","gaps":["Downstream signaling pathway from the receptor not mapped","Generalizability beyond choroidal endothelium untested"]},{"year":2011,"claim":"Demonstrated that competitive active-site inhibitors act as pharmacological chaperones, correcting mutant enzyme folding, trafficking and lysosomal maturation, providing a therapeutic strategy.","evidence":"Competitive inhibition and enzyme activity assays in patient fibroblasts with Western blot for trafficking","pmids":["22033734"],"confidence":"Medium","gaps":["Mutation-specific responsiveness spectrum not defined","In vivo efficacy not shown"]},{"year":2015,"claim":"Established GLB1 as the molecular source of senescence-associated β-galactosidase by linking enzyme accumulation to replicative and therapy-induced senescence markers.","evidence":"Replicative and chemotherapy-induced senescence in prostate epithelial/cancer cells with quantitative immunofluorescence and P16/CDKN2A correlation","pmids":["25876105"],"confidence":"Medium","gaps":["Causal role of GLB1 in senescence (vs marker) not tested","Mechanism of enzyme upregulation unknown"]},{"year":2018,"claim":"Pinpointed a specific residue (Asn490) as critical for catalytic-site geometry, linking an in-frame deletion to residual activity via active-site misalignment.","evidence":"Molecular dynamics simulation of mutant protein with fluorometric enzyme assay in patient leukocytes","pmids":["30187681"],"confidence":"Low","gaps":["Computational simulation without in vitro mutagenesis reconstitution","Single enzyme activity measurement"]},{"year":2019,"claim":"Provided direct genetic proof that GLB1 is the enzyme responsible for GM1 ganglioside degradation in human CNS tissue and that gene replacement reverses substrate storage.","evidence":"CRISPR/Cas9 knockout in iPSC-derived cerebral organoids with GM1 quantification and AAV9-GLB1 rescue","pmids":["31534909"],"confidence":"High","gaps":["Long-term and behavioral consequences of rescue not assessed in this system","Cell-type specificity within CNS not dissected"]},{"year":2022,"claim":"Revealed a pseudogene-insertion mechanism creating a cryptic exon that causes Morquio B, and showed splice-modulating oligonucleotides can restore wild-type GLB1 splicing.","evidence":"Whole-genome sequencing, mRNA analysis, minigene co-expression, and modified U7-snRNA antisense splice correction in a model cell line","pmids":["35882863"],"confidence":"High","gaps":["Correction in patient tissue/in vivo not demonstrated","Frequency of such structural lesions in patients unknown"]},{"year":2022,"claim":"Validated GLB1 as a quantitative in vivo reporter of systemic senescence, linking enzyme levels to chronological age and pharmacologically reversible pathological senescence.","evidence":"Glb1-2A-mCherry knock-in mouse with signal quantification across ages, bleomycin injury, and dasatinib+quercetin senolytic treatment","pmids":["36396643"],"confidence":"High","gaps":["Whether elevated GLB1 contributes functionally to senescence not addressed","Mechanism driving enzyme accumulation in senescent cells unresolved"]},{"year":2023,"claim":"Demonstrated precise correction of a pathogenic point mutation by adenine base editing, restoring active enzyme and normalizing lysosomal storage in patient cells.","evidence":"CRISPR adenine base editing of c.380G>A in patient fibroblasts with enzyme assay, lysosomal markers, and off-target analysis","pmids":["36629845"],"confidence":"Medium","gaps":["In vivo delivery and durability not tested","Applicable only to transition-amenable variants"]},{"year":2024,"claim":"Confirmed functional interdependence of the GLB1-NEU1-CTSA network in human neuronal cells and linked GLB1 loss to altered proliferation and invasion.","evidence":"CRISPR dual-guide knockout in SH-SY5Y cells with X-gal staining, qPCR and RNA-seq","pmids":["39076066"],"confidence":"Medium","gaps":["Mechanism linking GLB1 loss to NEU1/CTSA downregulation unknown","Proliferation/invasion phenotype mechanism not defined"]},{"year":null,"claim":"Whether GLB1 enzyme accumulation actively drives the senescent phenotype or is merely a biomarker, and how SR-protein-controlled isoform choice is regulated in physiological tissues, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No loss-of-function test of GLB1's causal contribution to senescence","Physiological control of EBP vs lysosomal isoform ratio uncharacterized","No experimental structure of the human enzyme or multienzyme complex in the corpus"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[10,13,6]},{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[10]},{"term_id":"GO:0001618","term_label":"virus receptor activity","supporting_discovery_ids":[1]}],"localization":[{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[2,5,6,10]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[10]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[0]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[8,12]}],"complexes":["lysosomal multienzyme complex (GLB1-NEU1-CTSA)"],"partners":["CTSA","NEU1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P16278","full_name":"Beta-galactosidase","aliases":["Acid beta-galactosidase","Lactase","Elastin receptor 1"],"length_aa":677,"mass_kda":76.1,"function":"Cleaves beta-linked terminal galactosyl residues from gangliosides, glycoproteins, and glycosaminoglycans Has no beta-galactosidase catalytic activity, but plays functional roles in the formation of extracellular elastic fibers (elastogenesis) and in the development of connective tissue. Seems to be identical to the elastin-binding protein (EBP), a major component of the non-integrin cell surface receptor expressed on fibroblasts, smooth muscle cells, chondroblasts, leukocytes, and certain cancer cell types. In elastin producing cells, associates with tropoelastin intracellularly and functions as a recycling molecular chaperone which facilitates the secretions of tropoelastin and its assembly into elastic fibers","subcellular_location":"Cytoplasm, perinuclear region","url":"https://www.uniprot.org/uniprotkb/P16278/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GLB1","classification":"Not Classified","n_dependent_lines":8,"n_total_lines":1208,"dependency_fraction":0.006622516556291391},"opencell":{"profiled":true,"resolved_as":"EBP","ensg_id":"ENSG00000147155","cell_line_id":"CID000289","localizations":[{"compartment":"vesicles","grade":3},{"compartment":"er","grade":2}],"interactors":[{"gene":"CANX","stoichiometry":0.2},{"gene":"LPCAT1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000289","total_profiled":1310},"omim":[{"mim_id":"613111","title":"CATHEPSIN A; CTSA","url":"https://www.omim.org/entry/613111"},{"mim_id":"612770","title":"PHOSPHATIDYLSERINE DECARBOXYLASE; PISD","url":"https://www.omim.org/entry/612770"},{"mim_id":"611458","title":"GALACTOSIDASE, BETA-1; GLB1","url":"https://www.omim.org/entry/611458"},{"mim_id":"608272","title":"NEURAMINIDASE 1; NEU1","url":"https://www.omim.org/entry/608272"},{"mim_id":"253010","title":"MUCOPOLYSACCHARIDOSIS, TYPE IVB; MPS4B","url":"https://www.omim.org/entry/253010"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Vesicles","reliability":"Supported"},{"location":"Golgi apparatus","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GLB1"},"hgnc":{"alias_symbol":["EBP"],"prev_symbol":["ELNR1"]},"alphafold":{"accession":"P16278","domains":[{"cath_id":"3.20.20.80","chopping":"35-357","consensus_level":"high","plddt":97.9173,"start":35,"end":357},{"cath_id":"2.60.120.260","chopping":"376-381_547-640","consensus_level":"high","plddt":94.1607,"start":376,"end":640},{"cath_id":"2.60.120.260","chopping":"396-515","consensus_level":"high","plddt":97.3488,"start":396,"end":515}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P16278","model_url":"https://alphafold.ebi.ac.uk/files/AF-P16278-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P16278-F1-predicted_aligned_error_v6.png","plddt_mean":90.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GLB1","jax_strain_url":"https://www.jax.org/strain/search?query=GLB1"},"sequence":{"accession":"P16278","fasta_url":"https://rest.uniprot.org/uniprotkb/P16278.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P16278/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P16278"}},"corpus_meta":[{"pmid":"25876105","id":"PMC_25876105","title":"Overexpression of the novel senescence marker β-galactosidase (GLB1) in prostate cancer predicts reduced PSA recurrence.","date":"2015","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25876105","citation_count":67,"is_preprint":false},{"pmid":"31534909","id":"PMC_31534909","title":"Human GLB1 knockout cerebral organoids: A model system for testing AAV9-mediated GLB1 gene therapy for reducing GM1 ganglioside storage in GM1 gangliosidosis.","date":"2019","source":"Molecular genetics and metabolism reports","url":"https://pubmed.ncbi.nlm.nih.gov/31534909","citation_count":51,"is_preprint":false},{"pmid":"16667080","id":"PMC_16667080","title":"Molecular characterization of the major maize embryo globulin encoded by the glb1 gene.","date":"1989","source":"Plant physiology","url":"https://pubmed.ncbi.nlm.nih.gov/16667080","citation_count":50,"is_preprint":false},{"pmid":"16941474","id":"PMC_16941474","title":"Twenty-one novel mutations in the GLB1 gene identified in a large group of GM1-gangliosidosis and Morquio B patients: possible common origin for the prevalent p.R59H mutation among gypsies.","date":"2006","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/16941474","citation_count":49,"is_preprint":false},{"pmid":"36396643","id":"PMC_36396643","title":"A Glb1-2A-mCherry reporter monitors systemic aging and predicts lifespan in middle-aged mice.","date":"2022","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/36396643","citation_count":37,"is_preprint":false},{"pmid":"17309651","id":"PMC_17309651","title":"Identification of 14 novel GLB1 mutations, including five deletions, in 19 patients with GM1 gangliosidosis from South America.","date":"2007","source":"Clinical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/17309651","citation_count":34,"is_preprint":false},{"pmid":"12644936","id":"PMC_12644936","title":"Modulating action of the new polymorphism L436F detected in the GLB1 gene of a type-II GM1 gangliosidosis 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frame). Overexpression of different SR proteins altered the relative proportions of these transcripts in a minigene system, indicating SR proteins as regulators of this alternative splicing event.\",\n      \"method\": \"Minigene splicing assay, cycloheximide-NMD inhibition, SR protein overexpression in HeLa cells and human fibroblasts\",\n      \"journal\": \"BMC research notes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — minigene functional assay with SR protein overexpression and NMD inhibition; single lab, two orthogonal methods\",\n      \"pmids\": [\"19114006\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"An alternatively spliced form of GLB1 is expressed on the surface of human choroidal endothelial cells and functions as a receptor for elastin-derived peptides (EDPs). Inhibition of this receptor blocked EDP-induced migration of choroidal endothelial cells, establishing GLB1 as the functional EDP receptor in this context.\",\n      \"method\": \"RT-PCR for receptor identification, cell migration assay with receptor inhibitors, in vivo mouse EDP injection with electroretinography and microarray\",\n      \"journal\": \"Matrix biology : journal of the International Society for Matrix Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RT-PCR identification plus functional inhibition assay; single lab, two orthogonal methods\",\n      \"pmids\": [\"22178079\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"GLB1-encoded β-galactosidase, on reaching the endosomal-lysosomal compartment, associates with protective protein/cathepsin A (PPCA) and neuraminidase to form the lysosomal multienzyme complex (LMC). Coimmunoprecipitation and Western blotting of patient-derived protein extracts showed that pathogenic mutations in GLB1 alter neuraminidase and PPCA patterns, indicating that disease-causing mutations disrupt the LMC.\",\n      \"method\": \"Expression of mutant alleles in heterologous cells, coimmunoprecipitation, Western blotting of patient protein extracts\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal coimmunoprecipitation with Western blotting for LMC components; single lab, two orthogonal methods\",\n      \"pmids\": [\"17664528\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The L436F polymorphism in GLB1 acts as a modulating variant: when present in cis with the R201C mutation, it severely reduces residual β-galactosidase activity compared to R201C alone. Expression studies in COS1 cells demonstrated that the R201C/L436F complex allele produces much lower GLB1 activity than R201C alone, establishing a cis-modulating mechanism for GLB1 activity.\",\n      \"method\": \"COS1 cell transfection expression studies, co-transfection experiments, Western blotting\",\n      \"journal\": \"Human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — heterologous cell expression with mutagenesis-equivalent allele comparison; single lab, two orthogonal methods\",\n      \"pmids\": [\"12644936\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The p.Arg595Trp variant in GLB1 markedly reduces β-galactosidase activity when expressed in COS-1 cells, establishing it as a pseudodeficiency allele — reducing enzymatic activity without causing clinical disease.\",\n      \"method\": \"COS-1 cell expression assay for β-galactosidase activity\",\n      \"journal\": \"Clinical genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single heterologous expression assay, single lab, single method\",\n      \"pmids\": [\"17661814\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Phenotype-determining GLB1 alleles were characterized by overexpression of missense mutations in COS-1 cells, and subcellular localization of mutant GLB1 proteins was assessed in patient fibroblasts, revealing that specific mutations impair proper intracellular trafficking and lysosomal delivery of the enzyme.\",\n      \"method\": \"COS-1 cell overexpression assays, subcellular localization in patient fibroblasts\",\n      \"journal\": \"Clinical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — heterologous expression with enzyme activity plus subcellular localization in patient cells; single lab, two orthogonal methods\",\n      \"pmids\": [\"20175788\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Fluorous iminoalditol derivatives of 1-deoxygalactonojirimycin act as competitive inhibitors of GLB1-encoded β-galactosidase and function as pharmacological chaperones: they bind the catalytic site of mutant enzymes, correct their misfolded conformation, normalize intracellular trafficking and lysosomal maturation (shown by Western blot), and restore up to tenfold residual enzyme activity in GM1 gangliosidosis patient fibroblasts.\",\n      \"method\": \"Enzyme activity assay in patient fibroblasts, Western blot for protein trafficking and lysosomal maturation, competitive inhibition assay\",\n      \"journal\": \"Journal of inherited metabolic disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — competitive inhibition assay plus Western blot for trafficking; single lab, two orthogonal methods\",\n      \"pmids\": [\"22033734\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"A 19-bp duplication in exon 15 of the canine GLB1 gene disrupts a potential exon splicing enhancer (ESE), causing exon 15 skipping in a fraction of transcripts. This produces two mutant mRNAs from the same allele: one retaining exon 15 with a premature termination codon (not subject to NMD due to its last-exon position), and one lacking exon 15 entirely — both predicted to encode truncated, non-functional proteins, causing GM1-gangliosidosis.\",\n      \"method\": \"Molecular cloning, sequencing of mutant allele, mRNA analysis, ESE prediction analysis\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mRNA analysis plus NMD rule application with mechanistic splice-site disruption; single lab, two orthogonal methods (sequencing + transcript analysis)\",\n      \"pmids\": [\"15944348\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Insertion of a processed pseudogene (NPM1) deep in intron 5 of GLB1 introduces pseudogene-derived splicing regulatory motifs that activate a cryptic exon 36 bp upstream of the integration site, leading to aberrant GLB1 splicing and Morquio B disease. Antisense splice-modulating oligonucleotides (ASMOs) incorporated in modified U7 snRNA blocked the cryptic exon and almost completely restored wild-type splicing in a model cell line.\",\n      \"method\": \"Whole-genome sequencing, mRNA analysis, minigene co-expression, antisense oligonucleotide splice correction in model cell line\",\n      \"journal\": \"NPJ genomic medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — functional minigene assay plus splice rescue by ASMOs, multiple orthogonal methods (WGS, mRNA analysis, minigene, modU7 rescue) in a single rigorous study\",\n      \"pmids\": [\"35882863\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"GLB1-encoded lysosomal β-galactosidase accumulates during replicative senescence and therapy-induced senescence in prostate epithelial cells, correlating with senescent morphology and P16/CDKN2A expression. This establishes GLB1 as the molecular origin of senescence-associated β-galactosidase (SA-β-gal) activity.\",\n      \"method\": \"In vitro replicative senescence of primary prostate epithelial cells, chemotherapy-induced senescence in PCa lines, immunofluorescent staining with quantitative imaging\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro senescence models with immunofluorescent quantification; single lab, two orthogonal experimental systems (replicative and induced senescence)\",\n      \"pmids\": [\"25876105\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"GLB1 knockout in human cerebral organoids (via CRISPR/Cas9) causes progressive accumulation of GM1 ganglioside, and microinjection of AAV9-GLB1 vector restores β-galactosidase activity and significantly reduces GM1 ganglioside content, demonstrating that GLB1 encodes the enzyme primarily responsible for GM1 ganglioside degradation in human CNS tissue.\",\n      \"method\": \"CRISPR/Cas9 GLB1 knockout in human iPSCs, cerebral organoid generation, GM1 ganglioside quantification, AAV9-GLB1 rescue with enzyme activity assay\",\n      \"journal\": \"Molecular genetics and metabolism reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — genetic knockout + biochemical substrate accumulation + gene rescue with enzyme activity restoration; multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"31534909\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"GLB1 knockout in SH-SY5Y human neuronal cells results in loss of β-galactosidase activity and downregulation of NEU1 and CTSA expression, establishing that the GLB1-NEU1-CTSA lysosomal multienzyme complex gene network is functionally interdependent. Knockout also suppressed cell proliferation and invasion.\",\n      \"method\": \"CRISPR/Cas9 dual-guide knockout, X-gal staining, qPCR, RNA-seq analysis\",\n      \"journal\": \"Cell biochemistry and function\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR knockout with enzyme activity confirmation plus downstream gene expression analysis; single lab, multiple methods\",\n      \"pmids\": [\"39076066\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Adenine base editing (ABE) of the pathogenic GLB1 c.380G>A (p.Cys127Tyr) variant in patient-derived fibroblasts restores canonical guanine at the target site and rescues synthesis of active β-galactosidase to therapeutic levels, normalizing primary glycoconjugate storage and lysosomal pathology.\",\n      \"method\": \"CRISPR/Cas-adenine base editing in patient fibroblasts, enzyme activity assay, lysosomal pathology markers, off-target analysis\",\n      \"journal\": \"The CRISPR journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — base editing with functional rescue demonstrated by enzyme assay and lysosomal markers; single lab, multiple orthogonal readouts\",\n      \"pmids\": [\"36629845\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"A novel in-frame deletion (p.Asn490del) in GLB1 alters the catalytic site geometry based on molecular dynamics simulation, causing misalignment of catalytic residues, and enzyme assay in patient leukocytes confirmed ~3% residual β-galactosidase activity, establishing the catalytic importance of residue Asn490.\",\n      \"method\": \"Molecular dynamics simulation of mutant protein, fluorometric enzyme activity assay in patient leukocytes\",\n      \"journal\": \"Molecular genetics & genomic medicine\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — computational simulation plus single enzyme activity measurement; no in vitro mutagenesis reconstitution\",\n      \"pmids\": [\"30187681\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"A Glb1-2A-mCherry (GAC) knock-in reporter in mice shows that GLB1 (lysosomal β-galactosidase) is elevated in tissues of aging mice, with GAC signal linearly correlating with chronological age and exponentially increasing in bleomycin-induced pathological senescence. Senolytic treatment (dasatinib + quercetin) reduced the GAC signal in bleomycin-treated mice, establishing GLB1 as a functional in vivo reporter of systemic senescence.\",\n      \"method\": \"Knock-in reporter mouse generation, fluorescent signal quantification across ages, bleomycin lung injury model, dasatinib+quercetin senolytic treatment\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — genetic reporter knock-in with functional validation across aging cohort, pathological model, and pharmacological intervention; multiple orthogonal methods in a rigorous study\",\n      \"pmids\": [\"36396643\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GLB1 encodes lysosomal β-galactosidase, a hydrolase that cleaves β-galactose from GM1 ganglioside and other glycoconjugates within the lysosome; in the lysosome it associates with protective protein/cathepsin A (PPCA) and neuraminidase to form the lysosomal multienzyme complex (LMC). The GLB1 pre-mRNA is alternatively spliced under SR protein regulation to produce either the full-length lysosomal enzyme or an elastin-binding protein (EBP) isoform that localizes to the cell surface and acts as a receptor for elastin-derived peptides. GLB1 is the molecular origin of senescence-associated β-galactosidase (SA-β-gal) activity, with enzyme levels rising progressively during replicative and stress-induced senescence in vivo and in vitro. Pathogenic missense mutations impair enzyme folding, intracellular trafficking, and catalytic activity, and pharmacological chaperones (competitive inhibitors such as iminoalditol derivatives) can correct misfolding and restore lysosomal targeting.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GLB1 encodes lysosomal β-galactosidase, the enzyme primarily responsible for degrading GM1 ganglioside in human CNS tissue; CRISPR knockout in cerebral organoids causes progressive GM1 accumulation that is reversed by AAV9-GLB1 delivery [#10]. On reaching the endosomal-lysosomal compartment, the enzyme associates with protective protein/cathepsin A (PPCA/CTSA) and neuraminidase (NEU1) to form the lysosomal multienzyme complex, and this gene network is functionally interdependent—loss of GLB1 downregulates NEU1 and CTSA, and pathogenic GLB1 mutations alter neuraminidase and PPCA patterns [#2, #11]. GLB1 pre-mRNA is alternatively spliced under SR-protein control to yield either the full-length lysosomal enzyme or an elastin-binding protein (EBP) isoform that is displayed at the cell surface and functions as a receptor for elastin-derived peptides driving choroidal endothelial cell migration [#0, #1]. The locus is the molecular origin of senescence-associated β-galactosidase activity, with enzyme levels rising during replicative and stress-induced senescence in vitro and increasing with chronological age and pathological senescence in vivo, where the signal is reduced by senolytic treatment [#9, #14]. Pathogenic missense and in-frame variants impair catalytic-site geometry, enzyme folding, intracellular trafficking, and lysosomal delivery, causing GM1 gangliosidosis and Morquio B disease; misfolding can be corrected by pharmacological chaperones (competitive iminoalditol inhibitors) and the underlying lesions by base editing or splice-modulating oligonucleotides [#5, #6, #8, #12, #13].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Established that GLB1 enzyme activity can be modulated in cis by a second variant, defining a complex-allele mechanism for phenotype severity rather than single-mutation effects.\",\n      \"evidence\": \"COS1 cell expression of R201C alone versus R201C/L436F complex allele with Western blotting\",\n      \"pmids\": [\"12644936\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which L436F further reduces activity (folding vs catalysis) not resolved\", \"Limited to a single allele combination\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Demonstrated a splicing-regulatory basis for loss of GLB1 function, showing that disruption of an exon splicing enhancer generates truncated non-functional transcripts and causes GM1-gangliosidosis.\",\n      \"evidence\": \"Cloning, sequencing and mRNA analysis of a canine GLB1 exon 15 duplication with ESE prediction\",\n      \"pmids\": [\"15944348\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Animal-model allele; human equivalence not tested\", \"Predicted truncated proteins not biochemically characterized\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Identified GLB1 as a subunit of the lysosomal multienzyme complex with PPCA and neuraminidase and showed disease mutations disrupt complex composition, linking enzyme stability to its partner proteins.\",\n      \"evidence\": \"Reciprocal coimmunoprecipitation and Western blotting of patient protein extracts plus mutant allele expression\",\n      \"pmids\": [\"17664528\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry and assembly order of the complex not defined\", \"No structural model of the interaction\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Distinguished pathogenic from benign variation by defining a pseudodeficiency allele that lowers enzyme activity without disease, clarifying genotype interpretation.\",\n      \"evidence\": \"COS-1 expression assay of p.Arg595Trp for β-galactosidase activity\",\n      \"pmids\": [\"17661814\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single heterologous expression assay, single method\", \"Trafficking and complex assembly not assessed\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Resolved how a single GLB1 locus produces both a lysosomal hydrolase and a surface elastin-binding protein, showing SR proteins and NMD govern the alternative splicing choice.\",\n      \"evidence\": \"Minigene splicing assay with SR protein overexpression and cycloheximide-NMD inhibition in HeLa cells and fibroblasts\",\n      \"pmids\": [\"19114006\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Endogenous regulation of the isoform ratio in tissues not measured\", \"Which specific SR proteins act physiologically unknown\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Connected specific missense mutations to defective intracellular trafficking and lysosomal delivery, establishing mistrafficking as a disease mechanism beyond loss of catalysis.\",\n      \"evidence\": \"COS-1 overexpression activity assays plus subcellular localization in patient fibroblasts\",\n      \"pmids\": [\"20175788\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Trafficking checkpoints disrupted not pinpointed\", \"Quantitative degree of mislocalization per allele unclear\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed the EBP isoform functions as a cell-surface receptor for elastin-derived peptides driving endothelial migration, giving the non-lysosomal GLB1 product a defined signaling role.\",\n      \"evidence\": \"RT-PCR identification, migration assay with receptor inhibitors, and in vivo mouse EDP injection\",\n      \"pmids\": [\"22178079\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Downstream signaling pathway from the receptor not mapped\", \"Generalizability beyond choroidal endothelium untested\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Demonstrated that competitive active-site inhibitors act as pharmacological chaperones, correcting mutant enzyme folding, trafficking and lysosomal maturation, providing a therapeutic strategy.\",\n      \"evidence\": \"Competitive inhibition and enzyme activity assays in patient fibroblasts with Western blot for trafficking\",\n      \"pmids\": [\"22033734\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mutation-specific responsiveness spectrum not defined\", \"In vivo efficacy not shown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Established GLB1 as the molecular source of senescence-associated β-galactosidase by linking enzyme accumulation to replicative and therapy-induced senescence markers.\",\n      \"evidence\": \"Replicative and chemotherapy-induced senescence in prostate epithelial/cancer cells with quantitative immunofluorescence and P16/CDKN2A correlation\",\n      \"pmids\": [\"25876105\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal role of GLB1 in senescence (vs marker) not tested\", \"Mechanism of enzyme upregulation unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Pinpointed a specific residue (Asn490) as critical for catalytic-site geometry, linking an in-frame deletion to residual activity via active-site misalignment.\",\n      \"evidence\": \"Molecular dynamics simulation of mutant protein with fluorometric enzyme assay in patient leukocytes\",\n      \"pmids\": [\"30187681\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Computational simulation without in vitro mutagenesis reconstitution\", \"Single enzyme activity measurement\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Provided direct genetic proof that GLB1 is the enzyme responsible for GM1 ganglioside degradation in human CNS tissue and that gene replacement reverses substrate storage.\",\n      \"evidence\": \"CRISPR/Cas9 knockout in iPSC-derived cerebral organoids with GM1 quantification and AAV9-GLB1 rescue\",\n      \"pmids\": [\"31534909\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Long-term and behavioral consequences of rescue not assessed in this system\", \"Cell-type specificity within CNS not dissected\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Revealed a pseudogene-insertion mechanism creating a cryptic exon that causes Morquio B, and showed splice-modulating oligonucleotides can restore wild-type GLB1 splicing.\",\n      \"evidence\": \"Whole-genome sequencing, mRNA analysis, minigene co-expression, and modified U7-snRNA antisense splice correction in a model cell line\",\n      \"pmids\": [\"35882863\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Correction in patient tissue/in vivo not demonstrated\", \"Frequency of such structural lesions in patients unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Validated GLB1 as a quantitative in vivo reporter of systemic senescence, linking enzyme levels to chronological age and pharmacologically reversible pathological senescence.\",\n      \"evidence\": \"Glb1-2A-mCherry knock-in mouse with signal quantification across ages, bleomycin injury, and dasatinib+quercetin senolytic treatment\",\n      \"pmids\": [\"36396643\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether elevated GLB1 contributes functionally to senescence not addressed\", \"Mechanism driving enzyme accumulation in senescent cells unresolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstrated precise correction of a pathogenic point mutation by adenine base editing, restoring active enzyme and normalizing lysosomal storage in patient cells.\",\n      \"evidence\": \"CRISPR adenine base editing of c.380G>A in patient fibroblasts with enzyme assay, lysosomal markers, and off-target analysis\",\n      \"pmids\": [\"36629845\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo delivery and durability not tested\", \"Applicable only to transition-amenable variants\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Confirmed functional interdependence of the GLB1-NEU1-CTSA network in human neuronal cells and linked GLB1 loss to altered proliferation and invasion.\",\n      \"evidence\": \"CRISPR dual-guide knockout in SH-SY5Y cells with X-gal staining, qPCR and RNA-seq\",\n      \"pmids\": [\"39076066\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking GLB1 loss to NEU1/CTSA downregulation unknown\", \"Proliferation/invasion phenotype mechanism not defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether GLB1 enzyme accumulation actively drives the senescent phenotype or is merely a biomarker, and how SR-protein-controlled isoform choice is regulated in physiological tissues, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No loss-of-function test of GLB1's causal contribution to senescence\", \"Physiological control of EBP vs lysosomal isoform ratio uncharacterized\", \"No experimental structure of the human enzyme or multienzyme complex in the corpus\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [10, 13, 6]},\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [10]},\n      {\"term_id\": \"GO:0001618\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [2, 5, 6, 10]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:1430728\", \"supporting_discovery_ids\": [10]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [10]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [8, 12]}\n    ],\n    \"complexes\": [\"lysosomal multienzyme complex (GLB1-NEU1-CTSA)\"],\n    \"partners\": [\"CTSA\", \"NEU1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}