{"gene":"FBXO27","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":2017,"finding":"FBXO27 is a glycoprotein-specific F-box protein that forms an SCF (SKP1/CUL1/F-box) ubiquitin ligase complex (SCF^FBXO27) and ubiquitinates glycoproteins exposed on damaged lysosomal membranes, including SNARE proteins VAMP3 and VAMP7, and lysosomal proteins LAMP1, LAMP2, GNS, PSAP, and TMEM192, to recruit autophagic machinery and induce lysophagy.","method":"Co-immunoprecipitation, overexpression-based ubiquitination screen upon lysosomal damage, identification of substrates by mass spectrometry, functional autophagic machinery recruitment assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP establishing SCF complex, substrate identification with multiple orthogonal methods (ubiquitination screen, overexpression, autophagic recruitment assays), replicated in a focused mechanistic study","pmids":["28743755"],"is_preprint":false},{"year":2017,"finding":"FBXO27 undergoes N-myristoylation, which localizes it to membranes and enables rapid accumulation around damaged lysosomes upon lysosomal damage.","method":"Localization experiments (imaging of FBXO27 at damaged lysosomes), identification of N-myristoylation as membrane-targeting signal","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment with functional context in a single focused study; N-myristoylation as mechanism inferred from the abstract without explicit mutagenesis detail reported","pmids":["28743755"],"is_preprint":false},{"year":2017,"finding":"Ubiquitination of LAMP2 by SCF^FBXO27 upon lysosomal damage enhances autophagic machinery recruitment to damaged lysosomes.","method":"Overexpression of FBXO27, ubiquitination assay of LAMP2, autophagic machinery recruitment assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct functional experiment linking FBXO27-mediated LAMP2 ubiquitination to autophagy recruitment, single lab, single study","pmids":["28743755"],"is_preprint":false},{"year":2008,"finding":"FBXO27 (as part of the FBA family) binds high-mannose and sulfated glycoproteins through a conserved G domain; two aromatic amino acids forming a hydrophobic pocket in the G domain are necessary for high-affinity glycan binding, as demonstrated by site-directed mutagenesis. FBXO27 co-precipitates components of the canonical SCF complex (Skp1, Cullin1, Rbx1).","method":"Glycan arrays, site-directed mutagenesis of G domain aromatic residues, co-immunoprecipitation of SCF complex components","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro binding assays with glycan arrays plus mutagenesis identifying critical residues, combined with co-IP for complex formation, multiple orthogonal methods in one study","pmids":["18203720"],"is_preprint":false},{"year":2011,"finding":"Skp1 binding to FBXO27 (Fbg5) stabilizes its conformation, enabling glycoprotein substrate binding; when expressed alone, Fbg5 does not bind N-glycoproteins, but co-expression with Skp1 facilitates ConA-reactive glycoprotein binding. Skp1 also increases FBXO27 cellular concentration by preventing aggregate formation.","method":"Co-expression and co-immunoprecipitation, ConA-glycoprotein binding assay, assessment of aggregate formation","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding and functional assays in a single lab with two orthogonal methods (co-IP and glycoprotein binding assay)","pmids":["21640084"],"is_preprint":false},{"year":2015,"finding":"Crystal structure of the Skp1-FBG3 (FBXO44) complex determined at 2.6 Å resolution revealed why FBG3 lacks carbohydrate-binding activity despite homology to FBXO27/Fbs3: distinct hydrogen bond networks in four loops (β2-β3, β5-β6, β7-β8, β9-β10) prevent formation of the carbohydrate-binding pocket present in Fbs1/FBXO2. By contrast, FBXO27 (Fbs3/FBG5) is confirmed to recognize N-glycans of glycoproteins.","method":"X-ray crystallography of Skp1-FBG3 complex, structure-based mutational analysis","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — crystal structure with mutagenesis for FBG3; FBXO27's glycan-binding property is referenced as established contrast, not directly re-tested in this paper","pmids":["26460611"],"is_preprint":false},{"year":2023,"finding":"CREG1 inhibits FBXO27 protein expression, thereby preventing FBXO27-mediated degradation of LAMP2 protein; loss of CREG1 leads to increased FBXO27 expression and reduced LAMP2 levels, impairing autophagy in cardiomyocytes.","method":"Knockdown and overexpression of CREG1 in neonatal mouse cardiomyocytes, western blotting for FBXO27 and LAMP2 protein levels, rescue experiments with LAMP2 overexpression","journal":"Experimental & molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic manipulation (KD/OE) with defined molecular readouts and rescue experiment, single lab","pmids":["37658156"],"is_preprint":false}],"current_model":"FBXO27 is an N-myristoylated, glycoprotein-specific F-box protein that assembles into the SCF^FBXO27 E3 ubiquitin ligase complex via Skp1 (which also stabilizes its conformation for substrate binding); upon lysosomal membrane damage, FBXO27 rapidly localizes to damaged lysosomes and ubiquitinates exposed glycoproteins—including LAMP2, VAMP3, VAMP7, LAMP1, GNS, PSAP, and TMEM192—to recruit autophagic machinery and drive lysophagy, with its activity regulated upstream by CREG1-dependent control of FBXO27 expression levels."},"narrative":{"mechanistic_narrative":"FBXO27 is a glycoprotein-specific F-box protein that nucleates an SCF (SKP1/CUL1/RBX1) E3 ubiquitin ligase complex and drives lysophagy, the selective autophagic clearance of damaged lysosomes [PMID:28743755, PMID:18203720]. Substrate recognition is mediated by a conserved G domain whose hydrophobic pocket, formed by two essential aromatic residues, binds high-mannose and sulfated N-glycans; mutation of these residues abolishes glycan binding [PMID:18203720]. SKP1 binding is required not only for complex assembly but also to stabilize the FBXO27 conformation competent for glycoprotein capture and to prevent its aggregation, increasing its cellular concentration [PMID:21640084]. Upon lysosomal membrane damage, N-myristoylation targets FBXO27 to membranes and enables its rapid accumulation at damaged lysosomes [PMID:28743755], where SCF^FBXO27 ubiquitinates glycoproteins exposed on the cytosolic face—including LAMP1, LAMP2, the SNAREs VAMP3 and VAMP7, GNS, PSAP, and TMEM192—to recruit autophagic machinery [PMID:28743755]; LAMP2 ubiquitination specifically enhances this recruitment [PMID:28743755]. FBXO27 levels are constrained upstream by CREG1, whose loss elevates FBXO27 and depletes LAMP2, impairing autophagy in cardiomyocytes [PMID:37658156].","teleology":[{"year":2008,"claim":"Established the biochemical basis of FBXO27 substrate selection—how an F-box protein recognizes glycoproteins rather than peptide motifs—by mapping glycan binding to a defined G domain pocket.","evidence":"Glycan arrays and site-directed mutagenesis of G domain aromatic residues, plus co-IP of SCF components, in vitro","pmids":["18203720"],"confidence":"High","gaps":["Did not identify physiological glycoprotein substrates in cells","Did not connect glycan recognition to a cellular pathway"]},{"year":2011,"claim":"Showed that SKP1 is not merely a scaffold adaptor but a conformational chaperone required for FBXO27 to bind glycoprotein substrates, explaining why the F-box protein is inactive in isolation.","evidence":"Co-expression/co-IP and ConA-glycoprotein binding assays with assessment of aggregation","pmids":["21640084"],"confidence":"Medium","gaps":["Structural basis of SKP1-induced stabilization not resolved","Single lab, no in vivo substrate context"]},{"year":2015,"claim":"Comparative structural analysis distinguished glycan-binding from non-binding paralogs, confirming FBXO27/Fbs3 as a bona fide N-glycan recognizer within the family.","evidence":"X-ray crystallography of the Skp1-FBG3 complex with structure-based mutagenesis (FBXO27 referenced as contrast)","pmids":["26460611"],"confidence":"Medium","gaps":["FBXO27's own structure not solved","FBXO27 glycan binding referenced, not directly re-tested here"]},{"year":2017,"claim":"Defined the physiological role of FBXO27: a lysophagy effector that senses lysosomal damage and ubiquitinates exposed lysosomal glycoproteins to trigger autophagic clearance, with N-myristoylation providing damage-responsive membrane targeting.","evidence":"Co-IP, overexpression ubiquitination screen upon lysosomal damage, mass spectrometry substrate identification, localization imaging, and autophagic recruitment assays","pmids":["28743755"],"confidence":"High","gaps":["Endogenous loss-of-function lysophagy phenotype not fully characterized","N-myristoylation mechanism inferred without explicit mutagenesis","Relative contribution of each substrate to recruitment unclear"]},{"year":2023,"claim":"Placed FBXO27 within an upstream regulatory circuit, showing its abundance is controlled by CREG1 and that unrestrained FBXO27 degrades LAMP2 to impair autophagy in cardiomyocytes.","evidence":"CREG1 knockdown/overexpression in neonatal mouse cardiomyocytes with western blot and LAMP2 rescue","pmids":["37658156"],"confidence":"Medium","gaps":["Mechanism by which CREG1 controls FBXO27 levels not defined","Tissue specificity of this regulation unknown"]},{"year":null,"claim":"How FBXO27 distinguishes damage-exposed glycans from normal lumenal glycoproteins and how substrate ubiquitination is mechanistically read by autophagy receptors remains open.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structure of the FBXO27 substrate-bound complex","Autophagy receptor coupling to ubiquitinated substrates not defined","In vivo physiological requirement beyond cardiomyocytes unestablished"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,2]},{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[0,3]}],"localization":[{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[0,1]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[0,2,6]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,3]}],"complexes":["SCF^FBXO27 (SKP1-CUL1-RBX1)"],"partners":["SKP1","CUL1","RBX1","LAMP2","VAMP3","VAMP7","CREG1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8NI29","full_name":"F-box only protein 27","aliases":["F-box/G-domain protein 5"],"length_aa":283,"mass_kda":31.6,"function":"Substrate-recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex. Able to recognize and bind denatured glycoproteins, which are modified with complex-type oligosaccharides","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q8NI29/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/FBXO27","classification":"Not Classified","n_dependent_lines":5,"n_total_lines":1208,"dependency_fraction":0.0041390728476821195},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/FBXO27","total_profiled":1310},"omim":[{"mim_id":"609099","title":"F-BOX ONLY PROTEIN 27; FBXO27","url":"https://www.omim.org/entry/609099"},{"mim_id":"609094","title":"F-BOX ONLY PROTEIN 17; FBXO17","url":"https://www.omim.org/entry/609094"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"skin 1","ntpm":35.4}],"url":"https://www.proteinatlas.org/search/FBXO27"},"hgnc":{"alias_symbol":["Fbg5","Fbx27"],"prev_symbol":[]},"alphafold":{"accession":"Q8NI29","domains":[{"cath_id":"1.20.1280.50","chopping":"28-106","consensus_level":"high","plddt":90.0234,"start":28,"end":106},{"cath_id":"2.60.120.260","chopping":"113-279","consensus_level":"high","plddt":96.6011,"start":113,"end":279}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NI29","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NI29-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NI29-F1-predicted_aligned_error_v6.png","plddt_mean":91.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=FBXO27","jax_strain_url":"https://www.jax.org/strain/search?query=FBXO27"},"sequence":{"accession":"Q8NI29","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8NI29.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8NI29/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NI29"}},"corpus_meta":[{"pmid":"32048886","id":"PMC_32048886","title":"Organelle-specific autophagy in inflammatory diseases: a potential therapeutic target underlying the quality control of multiple organelles.","date":"2020","source":"Autophagy","url":"https://pubmed.ncbi.nlm.nih.gov/32048886","citation_count":347,"is_preprint":false},{"pmid":"28743755","id":"PMC_28743755","title":"Ubiquitination of exposed glycoproteins by SCFFBXO27 directs damaged lysosomes for autophagy.","date":"2017","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/28743755","citation_count":117,"is_preprint":false},{"pmid":"18203720","id":"PMC_18203720","title":"Diversity in tissue expression, substrate binding, and SCF complex formation for a lectin family of ubiquitin ligases.","date":"2008","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/18203720","citation_count":67,"is_preprint":false},{"pmid":"37658156","id":"PMC_37658156","title":"The CREG1-FBXO27-LAMP2 axis alleviates diabetic cardiomyopathy by promoting autophagy in cardiomyocytes.","date":"2023","source":"Experimental & molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/37658156","citation_count":32,"is_preprint":false},{"pmid":"37357416","id":"PMC_37357416","title":"TRIM16-mediated lysophagy suppresses high-glucose-accumulated neuronal Aβ.","date":"2023","source":"Autophagy","url":"https://pubmed.ncbi.nlm.nih.gov/37357416","citation_count":32,"is_preprint":false},{"pmid":"12383498","id":"PMC_12383498","title":"A new subfamily of structurally related human F-box proteins.","date":"2002","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/12383498","citation_count":31,"is_preprint":false},{"pmid":"21640084","id":"PMC_21640084","title":"Skp1 stabilizes the conformation of F-box proteins.","date":"2011","source":"Biochemical and biophysical research 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immunology","url":"https://pubmed.ncbi.nlm.nih.gov/39923360","citation_count":4,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11037,"output_tokens":1958,"usd":0.031241,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8866,"output_tokens":2268,"usd":0.050515,"stage2_stop_reason":"end_turn"},"total_usd":0.081756,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2017,\n      \"finding\": \"FBXO27 is a glycoprotein-specific F-box protein that forms an SCF (SKP1/CUL1/F-box) ubiquitin ligase complex (SCF^FBXO27) and ubiquitinates glycoproteins exposed on damaged lysosomal membranes, including SNARE proteins VAMP3 and VAMP7, and lysosomal proteins LAMP1, LAMP2, GNS, PSAP, and TMEM192, to recruit autophagic machinery and induce lysophagy.\",\n      \"method\": \"Co-immunoprecipitation, overexpression-based ubiquitination screen upon lysosomal damage, identification of substrates by mass spectrometry, functional autophagic machinery recruitment assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP establishing SCF complex, substrate identification with multiple orthogonal methods (ubiquitination screen, overexpression, autophagic recruitment assays), replicated in a focused mechanistic study\",\n      \"pmids\": [\"28743755\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"FBXO27 undergoes N-myristoylation, which localizes it to membranes and enables rapid accumulation around damaged lysosomes upon lysosomal damage.\",\n      \"method\": \"Localization experiments (imaging of FBXO27 at damaged lysosomes), identification of N-myristoylation as membrane-targeting signal\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment with functional context in a single focused study; N-myristoylation as mechanism inferred from the abstract without explicit mutagenesis detail reported\",\n      \"pmids\": [\"28743755\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Ubiquitination of LAMP2 by SCF^FBXO27 upon lysosomal damage enhances autophagic machinery recruitment to damaged lysosomes.\",\n      \"method\": \"Overexpression of FBXO27, ubiquitination assay of LAMP2, autophagic machinery recruitment assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct functional experiment linking FBXO27-mediated LAMP2 ubiquitination to autophagy recruitment, single lab, single study\",\n      \"pmids\": [\"28743755\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"FBXO27 (as part of the FBA family) binds high-mannose and sulfated glycoproteins through a conserved G domain; two aromatic amino acids forming a hydrophobic pocket in the G domain are necessary for high-affinity glycan binding, as demonstrated by site-directed mutagenesis. FBXO27 co-precipitates components of the canonical SCF complex (Skp1, Cullin1, Rbx1).\",\n      \"method\": \"Glycan arrays, site-directed mutagenesis of G domain aromatic residues, co-immunoprecipitation of SCF complex components\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro binding assays with glycan arrays plus mutagenesis identifying critical residues, combined with co-IP for complex formation, multiple orthogonal methods in one study\",\n      \"pmids\": [\"18203720\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Skp1 binding to FBXO27 (Fbg5) stabilizes its conformation, enabling glycoprotein substrate binding; when expressed alone, Fbg5 does not bind N-glycoproteins, but co-expression with Skp1 facilitates ConA-reactive glycoprotein binding. Skp1 also increases FBXO27 cellular concentration by preventing aggregate formation.\",\n      \"method\": \"Co-expression and co-immunoprecipitation, ConA-glycoprotein binding assay, assessment of aggregate formation\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding and functional assays in a single lab with two orthogonal methods (co-IP and glycoprotein binding assay)\",\n      \"pmids\": [\"21640084\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Crystal structure of the Skp1-FBG3 (FBXO44) complex determined at 2.6 Å resolution revealed why FBG3 lacks carbohydrate-binding activity despite homology to FBXO27/Fbs3: distinct hydrogen bond networks in four loops (β2-β3, β5-β6, β7-β8, β9-β10) prevent formation of the carbohydrate-binding pocket present in Fbs1/FBXO2. By contrast, FBXO27 (Fbs3/FBG5) is confirmed to recognize N-glycans of glycoproteins.\",\n      \"method\": \"X-ray crystallography of Skp1-FBG3 complex, structure-based mutational analysis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — crystal structure with mutagenesis for FBG3; FBXO27's glycan-binding property is referenced as established contrast, not directly re-tested in this paper\",\n      \"pmids\": [\"26460611\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CREG1 inhibits FBXO27 protein expression, thereby preventing FBXO27-mediated degradation of LAMP2 protein; loss of CREG1 leads to increased FBXO27 expression and reduced LAMP2 levels, impairing autophagy in cardiomyocytes.\",\n      \"method\": \"Knockdown and overexpression of CREG1 in neonatal mouse cardiomyocytes, western blotting for FBXO27 and LAMP2 protein levels, rescue experiments with LAMP2 overexpression\",\n      \"journal\": \"Experimental & molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic manipulation (KD/OE) with defined molecular readouts and rescue experiment, single lab\",\n      \"pmids\": [\"37658156\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"FBXO27 is an N-myristoylated, glycoprotein-specific F-box protein that assembles into the SCF^FBXO27 E3 ubiquitin ligase complex via Skp1 (which also stabilizes its conformation for substrate binding); upon lysosomal membrane damage, FBXO27 rapidly localizes to damaged lysosomes and ubiquitinates exposed glycoproteins—including LAMP2, VAMP3, VAMP7, LAMP1, GNS, PSAP, and TMEM192—to recruit autophagic machinery and drive lysophagy, with its activity regulated upstream by CREG1-dependent control of FBXO27 expression levels.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"FBXO27 is a glycoprotein-specific F-box protein that nucleates an SCF (SKP1/CUL1/RBX1) E3 ubiquitin ligase complex and drives lysophagy, the selective autophagic clearance of damaged lysosomes [#0, #3]. Substrate recognition is mediated by a conserved G domain whose hydrophobic pocket, formed by two essential aromatic residues, binds high-mannose and sulfated N-glycans; mutation of these residues abolishes glycan binding [#3]. SKP1 binding is required not only for complex assembly but also to stabilize the FBXO27 conformation competent for glycoprotein capture and to prevent its aggregation, increasing its cellular concentration [#4]. Upon lysosomal membrane damage, N-myristoylation targets FBXO27 to membranes and enables its rapid accumulation at damaged lysosomes [#1], where SCF^FBXO27 ubiquitinates glycoproteins exposed on the cytosolic face—including LAMP1, LAMP2, the SNAREs VAMP3 and VAMP7, GNS, PSAP, and TMEM192—to recruit autophagic machinery [#0]; LAMP2 ubiquitination specifically enhances this recruitment [#2]. FBXO27 levels are constrained upstream by CREG1, whose loss elevates FBXO27 and depletes LAMP2, impairing autophagy in cardiomyocytes [#6].\",\n  \"teleology\": [\n    {\n      \"year\": 2008,\n      \"claim\": \"Established the biochemical basis of FBXO27 substrate selection—how an F-box protein recognizes glycoproteins rather than peptide motifs—by mapping glycan binding to a defined G domain pocket.\",\n      \"evidence\": \"Glycan arrays and site-directed mutagenesis of G domain aromatic residues, plus co-IP of SCF components, in vitro\",\n      \"pmids\": [\"18203720\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify physiological glycoprotein substrates in cells\", \"Did not connect glycan recognition to a cellular pathway\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed that SKP1 is not merely a scaffold adaptor but a conformational chaperone required for FBXO27 to bind glycoprotein substrates, explaining why the F-box protein is inactive in isolation.\",\n      \"evidence\": \"Co-expression/co-IP and ConA-glycoprotein binding assays with assessment of aggregation\",\n      \"pmids\": [\"21640084\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of SKP1-induced stabilization not resolved\", \"Single lab, no in vivo substrate context\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Comparative structural analysis distinguished glycan-binding from non-binding paralogs, confirming FBXO27/Fbs3 as a bona fide N-glycan recognizer within the family.\",\n      \"evidence\": \"X-ray crystallography of the Skp1-FBG3 complex with structure-based mutagenesis (FBXO27 referenced as contrast)\",\n      \"pmids\": [\"26460611\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"FBXO27's own structure not solved\", \"FBXO27 glycan binding referenced, not directly re-tested here\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defined the physiological role of FBXO27: a lysophagy effector that senses lysosomal damage and ubiquitinates exposed lysosomal glycoproteins to trigger autophagic clearance, with N-myristoylation providing damage-responsive membrane targeting.\",\n      \"evidence\": \"Co-IP, overexpression ubiquitination screen upon lysosomal damage, mass spectrometry substrate identification, localization imaging, and autophagic recruitment assays\",\n      \"pmids\": [\"28743755\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endogenous loss-of-function lysophagy phenotype not fully characterized\", \"N-myristoylation mechanism inferred without explicit mutagenesis\", \"Relative contribution of each substrate to recruitment unclear\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Placed FBXO27 within an upstream regulatory circuit, showing its abundance is controlled by CREG1 and that unrestrained FBXO27 degrades LAMP2 to impair autophagy in cardiomyocytes.\",\n      \"evidence\": \"CREG1 knockdown/overexpression in neonatal mouse cardiomyocytes with western blot and LAMP2 rescue\",\n      \"pmids\": [\"37658156\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which CREG1 controls FBXO27 levels not defined\", \"Tissue specificity of this regulation unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How FBXO27 distinguishes damage-exposed glycans from normal lumenal glycoproteins and how substrate ubiquitination is mechanistically read by autophagy receptors remains open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structure of the FBXO27 substrate-bound complex\", \"Autophagy receptor coupling to ubiquitinated substrates not defined\", \"In vivo physiological requirement beyond cardiomyocytes unestablished\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [0, 2, 6]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"complexes\": [\"SCF^FBXO27 (SKP1-CUL1-RBX1)\"],\n    \"partners\": [\"SKP1\", \"CUL1\", \"RBX1\", \"LAMP2\", \"VAMP3\", \"VAMP7\", \"CREG1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}