{"gene":"FBXO6","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":2003,"finding":"FBXO6 (Fbs2/FBG2) forms an SCF E3 ubiquitin ligase complex (SCFFbs2) that specifically recognizes high-mannose N-glycans (Man3-9GlcNAc2) on misfolded glycoproteins and targets them for ubiquitylation and proteasomal degradation as part of the ERAD pathway. Pull-down with various oligosaccharides defined the sugar-binding specificity; siRNA knockdown and dominant-negative FBX deletion mutant both inhibited TCRα degradation.","method":"Pull-down assay with defined oligosaccharides, co-immunoprecipitation, siRNA knockdown, dominant-negative overexpression, western blot","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods (biochemical pull-down with defined sugars, siRNA knockdown, dominant-negative mutant, in-cell degradation assay); foundational paper replicated by subsequent structural work","pmids":["12939278"],"is_preprint":false},{"year":2009,"finding":"The SCF-Fbx6 E3 ubiquitin ligase complex mediates ubiquitination and proteasomal degradation of Chk1 in response to DNA damage, thereby terminating the S-phase replication checkpoint. DNA damage exposes a degron-like region at the C-terminus of Chk1 that is recognized by Fbx6. Low Fbx6 levels impair Chk1 degradation and correlate with camptothecin resistance.","method":"Co-immunoprecipitation, in vivo ubiquitination assay, RNAi-mediated knockdown, overexpression, western blot, protein stability assays in cultured cancer cells and breast tumor tissues","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, in vivo ubiquitination assay, multiple cell lines, functional checkpoint termination readout, corroborated by independent NSCLC study (PMID:31140586)","pmids":["19716789"],"is_preprint":false},{"year":2012,"finding":"FBXO6 interacts with 29 high-confidence N-glycoproteins in an N-glycan-dependent manner across three cell lines (293T, HeLa, Jurkat), as identified by affinity purification combined with LC-MS. A glycan-recognition-defective FBXO6 mutant lost these interactions, confirming that the FBA domain mediates substrate recognition.","method":"Affinity purification, LC-MS proteomics, comparison of wild-type vs. glycan-recognition mutant FBXO6","journal":"Journal of proteome research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic proteomic identification in three cell lines with mutant control, but functional validation limited to interaction confirmation","pmids":["22268729"],"is_preprint":false},{"year":2016,"finding":"FBXO6 ubiquitinates and promotes proteasomal degradation of Ero1L (a protein disulfide oxidase in the ER), thereby inhibiting ER stress-induced apoptosis. Overexpression of FBXO6 increased Ero1L polyubiquitination and decreased its stability, while FBXO6 inhibition prolonged Ero1L half-life.","method":"In vivo ubiquitination assay, western blot for protein stability, CCK8 and FACS apoptosis assays, overexpression and RNAi knockdown","journal":"Cellular physiology and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo ubiquitination assay plus functional apoptosis readout, single lab, two orthogonal methods","pmids":["27855403"],"is_preprint":false},{"year":2018,"finding":"Overexpression of Fbxo6 inactivates the spindle assembly checkpoint by physically interacting with the checkpoint proteins Mad2 and BubR1, leading to premature exit from nocodazole-induced mitotic arrest, premature sister chromatid separation, and formation of binuclear/multilobed nuclei. Fbxo6 itself is phosphorylated during mitosis.","method":"Co-immunoprecipitation, overexpression in HeLa cells, nocodazole arrest/release assay, flow cytometry, microscopy for chromosome segregation defects","journal":"Cell cycle","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP demonstrating interaction with Mad2 and BubR1, functional mitotic exit assay, single lab","pmids":["30526252"],"is_preprint":false},{"year":2019,"finding":"FBXO6 promotes ubiquitination and proteasomal degradation of IRF3 independently of the canonical SCF complex, through its FBA region interacting with the IAD domain of IRF3. This non-canonical activity suppresses IFN-I antiviral signaling in HEK293T and A549 cells.","method":"Co-immunoprecipitation, domain-mapping experiments (structure-function), ubiquitination assay, overexpression and knockdown in HEK293T and A549 cells, IFN-I reporter assays","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with domain mapping, in-cell ubiquitination assay, functional IFN-I signaling readout; single lab, multiple orthogonal methods","pmids":["31308089"],"is_preprint":false},{"year":2019,"finding":"Fbxo6 reduces Chk1 protein levels and phosphorylation in non-small cell lung cancer cells, sensitizing them to cisplatin, consistent with its role as an SCF E3 ligase subunit mediating Chk1 degradation.","method":"In vitro cell-based assays, western blot for Chk1 protein and phosphorylation levels, cisplatin sensitivity assays, overexpression and knockdown","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — functional validation in NSCLC cells corroborating Chk1 as an FBXO6 substrate (originally established by PMID:19716789); single lab","pmids":["31140586"],"is_preprint":false},{"year":2020,"finding":"FBXO6 directly ubiquitinates and promotes proteasomal degradation of MMP14, reducing proteolytic activation of MMP13 and thereby protecting cartilage from degradation. TGFβ-SMAD2/3 signaling upregulates FBXO6 transcription, placing FBXO6 downstream of TGFβ in this protective pathway. Global and conditional (Col2a1-CreER) FBXO6 knockout mice showed accelerated experimental OA.","method":"Co-immunoprecipitation, in vivo ubiquitination assay, global and conditional knockout mouse models (ACLT-induced and spontaneous OA), SMAD2/3 knockout, overexpression rescue experiments, western blot","journal":"Annals of the rheumatic diseases","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, in vivo ubiquitination assay, multiple mouse genetic models (global KO, conditional KO, SMAD2-/- epistasis), functional OA phenotype readout","pmids":["32409323"],"is_preprint":false},{"year":2021,"finding":"FBXO6 acts as the E3 ubiquitin ligase for RNASET2, promoting its K48-linked ubiquitination and proteasomal degradation via the FBA domain. FBXO6 depletion stabilizes RNASET2 and suppresses ovarian cancer cell proliferation, migration, and invasion.","method":"Co-immunoprecipitation, in vivo ubiquitination assay (K48 linkage specified), domain deletion analysis, siRNA knockdown, overexpression rescue experiments in ovarian cancer cells","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, K48-specific ubiquitination assay, functional rescue, single lab, multiple orthogonal methods","pmids":["33767133"],"is_preprint":false},{"year":2022,"finding":"FBXO6 promotes proteasomal degradation of NLRX1 (a mitochondrial protein that counteracts virus-induced apoptosis), thereby facilitating IAV-induced alveolar macrophage apoptosis and impairing type I IFN production. FBXO6-deficient mice showed decreased pulmonary viral replication and enhanced type I IFN in the lungs.","method":"Co-immunoprecipitation, gain- and loss-of-function studies (FBXO6 knockout mice, shRNA knockdown in macrophages), in vivo IAV infection model, flow cytometry, IFN measurement","journal":"Journal of medical virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus in vivo knockout mouse model with defined antiviral phenotype; single lab","pmids":["36217277"],"is_preprint":false},{"year":2022,"finding":"HSP90 interacts with FBXO6 and reduces FBXO6-mediated polyubiquitination and proteasomal degradation of CD147, thereby stabilizing CD147 and promoting radioresistance in cervical cancer cells. FBXO6 overexpression sensitizes radioresistant cells to irradiation.","method":"Proteomics screen, co-immunoprecipitation, ubiquitination assay, overexpression and HSP90 inhibitor (17-AAG) treatment, clonogenic survival assays","journal":"Cancer science","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP, ubiquitination assay, functional radiosensitivity readout; single lab, multiple orthogonal methods","pmids":["35043518"],"is_preprint":false},{"year":2023,"finding":"MSI2 (Musashi-2) binds FBXO6 and cooperates with it to induce RNASET2 ubiquitination in vascular smooth muscle cells, regulating chemokine signaling and VSMC phenotypic switching in atherosclerosis.","method":"RNA-binding protein immunoprecipitation, co-immunoprecipitation, siRNA knockdown, western blot, CCK-8, wound healing and transwell assays, in vivo AS mouse model","journal":"Cellular signalling","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP demonstrating MSI2-FBXO6 interaction, functional ubiquitination inferred, single lab","pmids":["37633478"],"is_preprint":false},{"year":2024,"finding":"Crystal structure of bovine FBS2 (FBXO6 ortholog) in complex with SKP1 and the core N-glycan pentasaccharide Man3GlcNAc2 revealed the structural basis of sugar recognition by SCFFbs2 and identified a druggable pocket. NMR data complemented crystallographic findings to define disparate sugar-binding specificities between FBS family members.","method":"X-ray crystallography, NMR spectroscopy, in silico docking","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with defined ligand plus orthogonal NMR validation; directly resolves mechanism of N-glycan recognition","pmids":["39171510"],"is_preprint":false},{"year":2026,"finding":"FBXO6 binds ITGB1 at its glycoprotein recognition site, promotes ITGB1 ubiquitination and degradation, and thereby attenuates downstream FAK/PI3K/AKT/ERK signaling, suppressing colorectal cancer cell migration and invasion. ITGB1 overexpression counteracts these effects.","method":"Co-immunoprecipitation, mass spectrometry substrate identification, in vitro ubiquitination/degradation assays, overexpression and knockdown, in vivo xenograft models, rescue experiments","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus MS substrate identification, functional rescue with ITGB1 overexpression, in vivo xenograft validation; single lab","pmids":["41857001"],"is_preprint":false},{"year":2026,"finding":"FBXO6 directly binds SLC3A2 and induces its degradation through K48-linked ubiquitination, promoting ferroptosis and epithelial barrier disruption in ulcerative colitis.","method":"Co-immunoprecipitation, K48-linked ubiquitination assay, LPS-stimulated HT29 cell model, western blot, machine-learning-guided candidate prioritization","journal":"Inflammation research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, Co-IP and ubiquitination assay reported in abstract without detailed mechanistic follow-up; limited orthogonal validation described","pmids":["41741720"],"is_preprint":false},{"year":2026,"finding":"FBXO6 interacts with STARD3NL and promotes its destabilization, activating the Wnt/β-catenin signaling pathway to drive osteogenic differentiation of bone marrow mesenchymal stem cells.","method":"Label-free quantitative proteomics, co-immunoprecipitation, overexpression and siRNA knockdown, osteogenic differentiation assays (ALP, calcium nodules, osteogenic marker mRNA), Wnt/β-catenin inhibitor (DKK1) rescue, in vivo femoral defect model","journal":"Biochemical pharmacology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP interaction and proteomic identification, functional rescue experiments; single lab, substrate degradation mechanism not fully reconstituted","pmids":["41483826"],"is_preprint":false}],"current_model":"FBXO6 functions as the substrate-recognition subunit of the SCF (Skp1-Cul1-F-box) E3 ubiquitin ligase complex, using its FBA domain to bind high-mannose N-glycans (Man3-9GlcNAc2) on misfolded or cytosolic glycoproteins and target them for K48-linked polyubiquitination and proteasomal degradation; established substrates include Chk1 (terminating the S-phase replication checkpoint), MMP14 (protecting cartilage), IRF3 (suppressing antiviral IFN-I signaling via a non-canonical, SCF-independent mechanism), NLRX1 (facilitating virus-induced macrophage apoptosis), Ero1L (limiting ER stress-induced apoptosis), RNASET2 (promoting ovarian cancer), CD147 (modulated by HSP90 competition), ITGB1 (suppressing colorectal cancer invasiveness), SLC3A2 (driving ferroptosis in colitis), and STARD3NL (promoting osteogenesis via Wnt/β-catenin); additionally, FBXO6 interacts with spindle checkpoint proteins Mad2 and BubR1 to regulate mitotic exit, and its own expression is transcriptionally upregulated by TGFβ-SMAD2/3 signaling."},"narrative":{"mechanistic_narrative":"FBXO6 (Fbs2/FBG2) is the substrate-recognition F-box subunit of an SCF (Skp1-Cul1-F-box) E3 ubiquitin ligase that selects glycoproteins and other substrates for K48-linked polyubiquitination and proteasomal degradation [PMID:12939278, PMID:33767133]. Through its FBA domain it binds high-mannose N-glycans (Man3-9GlcNAc2) on misfolded glycoproteins, marking them for ERAD-coupled destruction; crystallography of the FBS2-SKP1 complex bound to the core Man3GlcNAc2 pentasaccharide defines the structural basis of this sugar recognition and reveals a druggable pocket [PMID:12939278, PMID:39171510], and a glycan-recognition-defective FBA mutant loses substrate binding across multiple cell lines [PMID:22268729]. FBXO6 thereby controls the abundance of a broad substrate set: it degrades Chk1 to terminate the S-phase replication checkpoint in response to DNA damage, an activity that modulates sensitivity to genotoxic chemotherapy [PMID:19716789, PMID:31140586]; it degrades the ER oxidase Ero1L to restrain ER stress-induced apoptosis [PMID:27855403]; and it targets MMP14 to limit MMP13 activation and protect cartilage, a protective axis placed downstream of TGFβ-SMAD2/3 signaling that transcriptionally upregulates FBXO6, with knockout mice developing accelerated osteoarthritis [PMID:32409323]. FBXO6 also acts in immune and oncogenic contexts, degrading IRF3 through a non-canonical SCF-independent mechanism to suppress type I interferon signaling [PMID:31308089] and degrading NLRX1 to promote influenza-induced macrophage apoptosis [PMID:36217277]. Beyond ubiquitin ligase activity, FBXO6 interacts with the spindle checkpoint proteins Mad2 and BubR1 to regulate mitotic exit, and is itself phosphorylated during mitosis [PMID:30526252].","teleology":[{"year":2003,"claim":"Established FBXO6's foundational identity as an SCF E3 ligase subunit that recognizes a glycan signal, answering how the cell links N-glycan structure to degradation of misfolded glycoproteins in ERAD.","evidence":"Oligosaccharide pull-down defining sugar specificity, co-IP, siRNA knockdown and dominant-negative FBX mutant scored against TCRα degradation","pmids":["12939278"],"confidence":"High","gaps":["Did not resolve the atomic basis of glycan recognition","Substrate repertoire beyond TCRα unknown at this stage"]},{"year":2009,"claim":"Identified Chk1 as a physiological substrate, showing FBXO6 terminates the S-phase replication checkpoint and that low FBXO6 confers genotoxic drug resistance.","evidence":"Reciprocal co-IP, in vivo ubiquitination assay, RNAi and stability assays in cancer cells and breast tumor tissue","pmids":["19716789"],"confidence":"High","gaps":["Whether Chk1 recognition is glycan-dependent or via a distinct C-terminal degron","Relationship to canonical SCF assembly for this substrate"]},{"year":2012,"claim":"Generalized the glycan-recognition mechanism by mapping a high-confidence N-glycoprotein interactome dependent on an intact FBA domain.","evidence":"Affinity purification with LC-MS across 293T, HeLa, Jurkat comparing wild-type vs glycan-recognition mutant FBXO6","pmids":["22268729"],"confidence":"Medium","gaps":["Interactions not validated as productive ubiquitination substrates","Functional consequence of each interaction not tested"]},{"year":2016,"claim":"Connected FBXO6 to ER redox homeostasis by showing degradation of Ero1L restrains ER stress-induced apoptosis.","evidence":"In vivo ubiquitination, stability western blots, CCK8/FACS apoptosis assays with overexpression and RNAi","pmids":["27855403"],"confidence":"Medium","gaps":["Single lab; reciprocal validation limited","Whether degradation is glycan-dependent not addressed"]},{"year":2018,"claim":"Revealed a degradation-independent mitotic role, with FBXO6 binding Mad2 and BubR1 to inactivate the spindle assembly checkpoint.","evidence":"Co-IP, overexpression in HeLa, nocodazole arrest/release, flow cytometry and microscopy of segregation defects","pmids":["30526252"],"confidence":"Medium","gaps":["Whether the interaction is ubiquitination-coupled or purely scaffolding unclear","Endogenous-level requirement not established"]},{"year":2019,"claim":"Defined a non-canonical, SCF-independent activity in which FBXO6 degrades IRF3 to suppress type I interferon antiviral signaling.","evidence":"Co-IP with FBA-IAD domain mapping, ubiquitination and IFN-I reporter assays in HEK293T and A549","pmids":["31308089"],"confidence":"Medium","gaps":["Mechanism of SCF-independent ubiquitin transfer unresolved","In vivo antiviral consequence not tested in this study"]},{"year":2019,"claim":"Corroborated Chk1 as a substrate in an independent cancer context, linking FBXO6 to cisplatin sensitization in NSCLC.","evidence":"Cell-based assays, Chk1 protein/phospho western blots, cisplatin sensitivity with overexpression and knockdown","pmids":["31140586"],"confidence":"Medium","gaps":["No in vivo validation","Direct ubiquitination not re-demonstrated"]},{"year":2020,"claim":"Established a TGFβ-SMAD2/3 → FBXO6 → MMP14 protective axis in cartilage with strong genetic causality for osteoarthritis.","evidence":"Reciprocal co-IP, in vivo ubiquitination, global and Col2a1-CreER conditional knockout mice, SMAD2/3 epistasis, rescue","pmids":["32409323"],"confidence":"High","gaps":["Whether MMP14 recognition uses the glycan-binding pocket not resolved","Generalizability of TGFβ-driven induction to other tissues"]},{"year":2021,"claim":"Identified RNASET2 as a K48-linked ubiquitination substrate, linking FBXO6 to ovarian cancer progression.","evidence":"Co-IP, K48-specific in vivo ubiquitination, FBA domain deletion, siRNA and rescue in ovarian cancer cells","pmids":["33767133"],"confidence":"Medium","gaps":["Single lab","In vivo tumor validation limited"]},{"year":2022,"claim":"Showed FBXO6 activity is itself regulated by competing chaperone interactions, with HSP90 binding FBXO6 to protect CD147 and confer radioresistance.","evidence":"Proteomics, co-IP, ubiquitination assay, 17-AAG HSP90 inhibition, clonogenic survival in cervical cancer cells","pmids":["35043518"],"confidence":"Medium","gaps":["Structural basis of HSP90-FBXO6 competition unknown","Single lab"]},{"year":2022,"claim":"Extended the antiviral role in vivo, with FBXO6 degrading NLRX1 to promote influenza-induced macrophage apoptosis and dampen type I IFN.","evidence":"Co-IP, FBXO6 knockout mice and macrophage shRNA, in vivo IAV infection, flow cytometry, IFN measurement","pmids":["36217277"],"confidence":"Medium","gaps":["Direct ubiquitination of NLRX1 not fully demonstrated","Relationship to the IRF3 axis not reconciled"]},{"year":2023,"claim":"Implicated an RNA-binding cofactor, MSI2, cooperating with FBXO6 to ubiquitinate RNASET2 in vascular smooth muscle phenotypic switching.","evidence":"RIP, co-IP, siRNA, migration assays and atherosclerosis mouse model","pmids":["37633478"],"confidence":"Low","gaps":["Single Co-IP for MSI2-FBXO6; not reciprocally validated","FBXO6-mediated ubiquitination inferred rather than directly shown here"]},{"year":2024,"claim":"Resolved the atomic mechanism of glycan recognition, providing the structural basis for SCFFbs2 sugar binding and a druggable pocket.","evidence":"X-ray crystal structure of bovine FBS2-SKP1 with Man3GlcNAc2, complemented by NMR and in silico docking","pmids":["39171510"],"confidence":"High","gaps":["No structure of FBXO6 bound to a full glycoprotein substrate","Druggability not yet validated by chemical probes"]},{"year":2026,"claim":"Expanded the substrate set to ITGB1, SLC3A2, and STARD3NL, linking FBXO6 degradation activity to colorectal cancer invasion, colitis ferroptosis, and Wnt-driven osteogenesis respectively.","evidence":"Co-IP/MS substrate identification, K48 ubiquitination assays, knockdown/overexpression rescue, xenograft and disease models","pmids":["41857001","41741720","41483826"],"confidence":"Low","gaps":["SLC3A2 and STARD3NL findings are single-lab with limited orthogonal validation","STARD3NL degradation mechanism not fully reconstituted","Whether each substrate is recognized via the glycan pocket unaddressed"]},{"year":null,"claim":"How FBXO6 discriminates among its many reported substrates — glycan-dependent versus degron-based versus SCF-independent recognition — and what governs context-specific substrate choice across tissues remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No unified model reconciling glycan recognition with non-glycan substrates like Chk1 and IRF3","Structural basis of substrate selection beyond the glycan pocket unknown","Mechanism of SCF-independent ubiquitination not characterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,3,7,8,13]},{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[0,1,8]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,2,12]}],"localization":[],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,1,7,8]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[1,4]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[5,9]}],"complexes":["SCF (Skp1-Cul1-F-box) E3 ubiquitin ligase"],"partners":["SKP1","CHK1","MMP14","IRF3","NLRX1","MAD2","BUBR1","HSP90"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NRD1","full_name":"F-box only protein 6","aliases":["F-box protein that recognizes sugar chains 2","F-box/G-domain protein 2"],"length_aa":293,"mass_kda":33.9,"function":"Substrate-recognition component of some SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complexes. Involved in endoplasmic reticulum-associated degradation pathway (ERAD) for misfolded lumenal proteins by recognizing and binding sugar chains on unfolded glycoproteins that are retrotranslocated into the cytosol and promoting their ubiquitination and subsequent degradation. Able to recognize and bind denatured glycoproteins, which are modified with not only high-mannose but also complex-type oligosaccharides. Also recognizes sulfated glycans. Also involved in DNA damage response by specifically recognizing activated CHEK1 (phosphorylated on 'Ser-345'), promoting its ubiquitination and degradation. Ubiquitination of CHEK1 is required to ensure that activated CHEK1 does not accumulate as cells progress through S phase, or when replication forks encounter transient impediments during normal DNA replication","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q9NRD1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/FBXO6","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/FBXO6","total_profiled":1310},"omim":[{"mim_id":"609111","title":"F-BOX ONLY PROTEIN 44; FBXO44","url":"https://www.omim.org/entry/609111"},{"mim_id":"607112","title":"F-BOX ONLY PROTEIN 2; FBXO2","url":"https://www.omim.org/entry/607112"},{"mim_id":"605647","title":"F-BOX ONLY PROTEIN 6; FBXO6","url":"https://www.omim.org/entry/605647"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/FBXO6"},"hgnc":{"alias_symbol":["FBX6","FBG2","FBS2","Fbx6b"],"prev_symbol":[]},"alphafold":{"accession":"Q9NRD1","domains":[{"cath_id":"1.20.1280.50","chopping":"13-83","consensus_level":"high","plddt":94.0615,"start":13,"end":83},{"cath_id":"2.60.120.260","chopping":"101-261","consensus_level":"high","plddt":97.0998,"start":101,"end":261}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NRD1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NRD1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NRD1-F1-predicted_aligned_error_v6.png","plddt_mean":88.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=FBXO6","jax_strain_url":"https://www.jax.org/strain/search?query=FBXO6"},"sequence":{"accession":"Q9NRD1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NRD1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NRD1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NRD1"}},"corpus_meta":[{"pmid":"19716789","id":"PMC_19716789","title":"The F box protein Fbx6 regulates Chk1 stability and cellular sensitivity to replication stress.","date":"2009","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/19716789","citation_count":153,"is_preprint":false},{"pmid":"12939278","id":"PMC_12939278","title":"Fbs2 is a new member of the E3 ubiquitin ligase family that recognizes sugar chains.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12939278","citation_count":138,"is_preprint":false},{"pmid":"32409323","id":"PMC_32409323","title":"TGFβ attenuates cartilage extracellular matrix degradation via enhancing FBXO6-mediated MMP14 ubiquitination.","date":"2020","source":"Annals of the rheumatic diseases","url":"https://pubmed.ncbi.nlm.nih.gov/32409323","citation_count":77,"is_preprint":false},{"pmid":"22268729","id":"PMC_22268729","title":"Proteomic identification of common SCF ubiquitin ligase FBXO6-interacting glycoproteins in three kinds of cells.","date":"2012","source":"Journal of proteome research","url":"https://pubmed.ncbi.nlm.nih.gov/22268729","citation_count":39,"is_preprint":false},{"pmid":"33767133","id":"PMC_33767133","title":"FBXO6-mediated RNASET2 ubiquitination and degradation governs the development of ovarian cancer.","date":"2021","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/33767133","citation_count":33,"is_preprint":false},{"pmid":"27855403","id":"PMC_27855403","title":"FBXO6-Mediated Ubiquitination and Degradation of Ero1L Inhibits Endoplasmic Reticulum Stress-Induced Apoptosis.","date":"2016","source":"Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/27855403","citation_count":27,"is_preprint":false},{"pmid":"35043518","id":"PMC_35043518","title":"HSP90 promotes radioresistance of cervical cancer cells via reducing FBXO6-mediated CD147 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Analysis of FBXO2, FBXO6, FBXO12, and FBXO41 Variants in Han Chinese Patients with Sporadic Parkinson's Disease.","date":"2017","source":"Neuroscience bulletin","url":"https://pubmed.ncbi.nlm.nih.gov/28341977","citation_count":12,"is_preprint":false},{"pmid":"30526252","id":"PMC_30526252","title":"Overexpression of Fbxo6 inactivates spindle checkpoint by interacting with Mad2 and BubR1.","date":"2018","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/30526252","citation_count":11,"is_preprint":false},{"pmid":"35063764","id":"PMC_35063764","title":"The USP18-FBXO6 axis maintains the malignancy of ovarian cancer.","date":"2022","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/35063764","citation_count":10,"is_preprint":false},{"pmid":"37633478","id":"PMC_37633478","title":"Musashi-2 binds with Fbxo6 to induce Rnaset2 ubiquitination and chemokine signaling pathway during vascular smooth muscle cell phenotypic switch in atherosclerosis.","date":"2023","source":"Cellular signalling","url":"https://pubmed.ncbi.nlm.nih.gov/37633478","citation_count":3,"is_preprint":false},{"pmid":"39171510","id":"PMC_39171510","title":"Structural basis of sugar recognition by SCFFBS2 ubiquitin ligase involved in NGLY1 deficiency.","date":"2024","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/39171510","citation_count":3,"is_preprint":false},{"pmid":"39674232","id":"PMC_39674232","title":"Delivery of FBXO6 with highly branched poly(β-amino ester)s to modulate the inflammatory environment for the treatment of osteoarthritis.","date":"2024","source":"Journal of controlled release : official journal of the Controlled Release Society","url":"https://pubmed.ncbi.nlm.nih.gov/39674232","citation_count":1,"is_preprint":false},{"pmid":"41857001","id":"PMC_41857001","title":"FBXO6 regulates colon cancer migration and invasion via ITGB1 ubiquitination and downstream signaling.","date":"2026","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/41857001","citation_count":0,"is_preprint":false},{"pmid":"41741720","id":"PMC_41741720","title":"FBXO6 mediated ubiquitination of SLC3A2 drives ferroptosis in ulcerative colitis: a machine learning and SHAP discovery.","date":"2026","source":"Inflammation research : official journal of the European Histamine Research Society ... [et al.]","url":"https://pubmed.ncbi.nlm.nih.gov/41741720","citation_count":0,"is_preprint":false},{"pmid":"41483826","id":"PMC_41483826","title":"Accelerating bone healing in femoral defect model using FBXO6-modified bone marrow-derived mesenchymal stem cells on a collagen scaffold.","date":"2026","source":"Biochemical pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/41483826","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13698,"output_tokens":4335,"usd":0.05306,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12255,"output_tokens":4388,"usd":0.085487,"stage2_stop_reason":"end_turn"},"total_usd":0.138547,"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\": 2003,\n      \"finding\": \"FBXO6 (Fbs2/FBG2) forms an SCF E3 ubiquitin ligase complex (SCFFbs2) that specifically recognizes high-mannose N-glycans (Man3-9GlcNAc2) on misfolded glycoproteins and targets them for ubiquitylation and proteasomal degradation as part of the ERAD pathway. Pull-down with various oligosaccharides defined the sugar-binding specificity; siRNA knockdown and dominant-negative FBX deletion mutant both inhibited TCRα degradation.\",\n      \"method\": \"Pull-down assay with defined oligosaccharides, co-immunoprecipitation, siRNA knockdown, dominant-negative overexpression, western blot\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods (biochemical pull-down with defined sugars, siRNA knockdown, dominant-negative mutant, in-cell degradation assay); foundational paper replicated by subsequent structural work\",\n      \"pmids\": [\"12939278\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"The SCF-Fbx6 E3 ubiquitin ligase complex mediates ubiquitination and proteasomal degradation of Chk1 in response to DNA damage, thereby terminating the S-phase replication checkpoint. DNA damage exposes a degron-like region at the C-terminus of Chk1 that is recognized by Fbx6. Low Fbx6 levels impair Chk1 degradation and correlate with camptothecin resistance.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assay, RNAi-mediated knockdown, overexpression, western blot, protein stability assays in cultured cancer cells and breast tumor tissues\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, in vivo ubiquitination assay, multiple cell lines, functional checkpoint termination readout, corroborated by independent NSCLC study (PMID:31140586)\",\n      \"pmids\": [\"19716789\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"FBXO6 interacts with 29 high-confidence N-glycoproteins in an N-glycan-dependent manner across three cell lines (293T, HeLa, Jurkat), as identified by affinity purification combined with LC-MS. A glycan-recognition-defective FBXO6 mutant lost these interactions, confirming that the FBA domain mediates substrate recognition.\",\n      \"method\": \"Affinity purification, LC-MS proteomics, comparison of wild-type vs. glycan-recognition mutant FBXO6\",\n      \"journal\": \"Journal of proteome research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic proteomic identification in three cell lines with mutant control, but functional validation limited to interaction confirmation\",\n      \"pmids\": [\"22268729\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"FBXO6 ubiquitinates and promotes proteasomal degradation of Ero1L (a protein disulfide oxidase in the ER), thereby inhibiting ER stress-induced apoptosis. Overexpression of FBXO6 increased Ero1L polyubiquitination and decreased its stability, while FBXO6 inhibition prolonged Ero1L half-life.\",\n      \"method\": \"In vivo ubiquitination assay, western blot for protein stability, CCK8 and FACS apoptosis assays, overexpression and RNAi knockdown\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo ubiquitination assay plus functional apoptosis readout, single lab, two orthogonal methods\",\n      \"pmids\": [\"27855403\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Overexpression of Fbxo6 inactivates the spindle assembly checkpoint by physically interacting with the checkpoint proteins Mad2 and BubR1, leading to premature exit from nocodazole-induced mitotic arrest, premature sister chromatid separation, and formation of binuclear/multilobed nuclei. Fbxo6 itself is phosphorylated during mitosis.\",\n      \"method\": \"Co-immunoprecipitation, overexpression in HeLa cells, nocodazole arrest/release assay, flow cytometry, microscopy for chromosome segregation defects\",\n      \"journal\": \"Cell cycle\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP demonstrating interaction with Mad2 and BubR1, functional mitotic exit assay, single lab\",\n      \"pmids\": [\"30526252\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"FBXO6 promotes ubiquitination and proteasomal degradation of IRF3 independently of the canonical SCF complex, through its FBA region interacting with the IAD domain of IRF3. This non-canonical activity suppresses IFN-I antiviral signaling in HEK293T and A549 cells.\",\n      \"method\": \"Co-immunoprecipitation, domain-mapping experiments (structure-function), ubiquitination assay, overexpression and knockdown in HEK293T and A549 cells, IFN-I reporter assays\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with domain mapping, in-cell ubiquitination assay, functional IFN-I signaling readout; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"31308089\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Fbxo6 reduces Chk1 protein levels and phosphorylation in non-small cell lung cancer cells, sensitizing them to cisplatin, consistent with its role as an SCF E3 ligase subunit mediating Chk1 degradation.\",\n      \"method\": \"In vitro cell-based assays, western blot for Chk1 protein and phosphorylation levels, cisplatin sensitivity assays, overexpression and knockdown\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — functional validation in NSCLC cells corroborating Chk1 as an FBXO6 substrate (originally established by PMID:19716789); single lab\",\n      \"pmids\": [\"31140586\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"FBXO6 directly ubiquitinates and promotes proteasomal degradation of MMP14, reducing proteolytic activation of MMP13 and thereby protecting cartilage from degradation. TGFβ-SMAD2/3 signaling upregulates FBXO6 transcription, placing FBXO6 downstream of TGFβ in this protective pathway. Global and conditional (Col2a1-CreER) FBXO6 knockout mice showed accelerated experimental OA.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assay, global and conditional knockout mouse models (ACLT-induced and spontaneous OA), SMAD2/3 knockout, overexpression rescue experiments, western blot\",\n      \"journal\": \"Annals of the rheumatic diseases\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, in vivo ubiquitination assay, multiple mouse genetic models (global KO, conditional KO, SMAD2-/- epistasis), functional OA phenotype readout\",\n      \"pmids\": [\"32409323\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"FBXO6 acts as the E3 ubiquitin ligase for RNASET2, promoting its K48-linked ubiquitination and proteasomal degradation via the FBA domain. FBXO6 depletion stabilizes RNASET2 and suppresses ovarian cancer cell proliferation, migration, and invasion.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assay (K48 linkage specified), domain deletion analysis, siRNA knockdown, overexpression rescue experiments in ovarian cancer cells\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, K48-specific ubiquitination assay, functional rescue, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"33767133\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"FBXO6 promotes proteasomal degradation of NLRX1 (a mitochondrial protein that counteracts virus-induced apoptosis), thereby facilitating IAV-induced alveolar macrophage apoptosis and impairing type I IFN production. FBXO6-deficient mice showed decreased pulmonary viral replication and enhanced type I IFN in the lungs.\",\n      \"method\": \"Co-immunoprecipitation, gain- and loss-of-function studies (FBXO6 knockout mice, shRNA knockdown in macrophages), in vivo IAV infection model, flow cytometry, IFN measurement\",\n      \"journal\": \"Journal of medical virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus in vivo knockout mouse model with defined antiviral phenotype; single lab\",\n      \"pmids\": [\"36217277\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"HSP90 interacts with FBXO6 and reduces FBXO6-mediated polyubiquitination and proteasomal degradation of CD147, thereby stabilizing CD147 and promoting radioresistance in cervical cancer cells. FBXO6 overexpression sensitizes radioresistant cells to irradiation.\",\n      \"method\": \"Proteomics screen, co-immunoprecipitation, ubiquitination assay, overexpression and HSP90 inhibitor (17-AAG) treatment, clonogenic survival assays\",\n      \"journal\": \"Cancer science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP, ubiquitination assay, functional radiosensitivity readout; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"35043518\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MSI2 (Musashi-2) binds FBXO6 and cooperates with it to induce RNASET2 ubiquitination in vascular smooth muscle cells, regulating chemokine signaling and VSMC phenotypic switching in atherosclerosis.\",\n      \"method\": \"RNA-binding protein immunoprecipitation, co-immunoprecipitation, siRNA knockdown, western blot, CCK-8, wound healing and transwell assays, in vivo AS mouse model\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP demonstrating MSI2-FBXO6 interaction, functional ubiquitination inferred, single lab\",\n      \"pmids\": [\"37633478\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Crystal structure of bovine FBS2 (FBXO6 ortholog) in complex with SKP1 and the core N-glycan pentasaccharide Man3GlcNAc2 revealed the structural basis of sugar recognition by SCFFbs2 and identified a druggable pocket. NMR data complemented crystallographic findings to define disparate sugar-binding specificities between FBS family members.\",\n      \"method\": \"X-ray crystallography, NMR spectroscopy, in silico docking\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with defined ligand plus orthogonal NMR validation; directly resolves mechanism of N-glycan recognition\",\n      \"pmids\": [\"39171510\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"FBXO6 binds ITGB1 at its glycoprotein recognition site, promotes ITGB1 ubiquitination and degradation, and thereby attenuates downstream FAK/PI3K/AKT/ERK signaling, suppressing colorectal cancer cell migration and invasion. ITGB1 overexpression counteracts these effects.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry substrate identification, in vitro ubiquitination/degradation assays, overexpression and knockdown, in vivo xenograft models, rescue experiments\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus MS substrate identification, functional rescue with ITGB1 overexpression, in vivo xenograft validation; single lab\",\n      \"pmids\": [\"41857001\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"FBXO6 directly binds SLC3A2 and induces its degradation through K48-linked ubiquitination, promoting ferroptosis and epithelial barrier disruption in ulcerative colitis.\",\n      \"method\": \"Co-immunoprecipitation, K48-linked ubiquitination assay, LPS-stimulated HT29 cell model, western blot, machine-learning-guided candidate prioritization\",\n      \"journal\": \"Inflammation research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, Co-IP and ubiquitination assay reported in abstract without detailed mechanistic follow-up; limited orthogonal validation described\",\n      \"pmids\": [\"41741720\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"FBXO6 interacts with STARD3NL and promotes its destabilization, activating the Wnt/β-catenin signaling pathway to drive osteogenic differentiation of bone marrow mesenchymal stem cells.\",\n      \"method\": \"Label-free quantitative proteomics, co-immunoprecipitation, overexpression and siRNA knockdown, osteogenic differentiation assays (ALP, calcium nodules, osteogenic marker mRNA), Wnt/β-catenin inhibitor (DKK1) rescue, in vivo femoral defect model\",\n      \"journal\": \"Biochemical pharmacology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP interaction and proteomic identification, functional rescue experiments; single lab, substrate degradation mechanism not fully reconstituted\",\n      \"pmids\": [\"41483826\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"FBXO6 functions as the substrate-recognition subunit of the SCF (Skp1-Cul1-F-box) E3 ubiquitin ligase complex, using its FBA domain to bind high-mannose N-glycans (Man3-9GlcNAc2) on misfolded or cytosolic glycoproteins and target them for K48-linked polyubiquitination and proteasomal degradation; established substrates include Chk1 (terminating the S-phase replication checkpoint), MMP14 (protecting cartilage), IRF3 (suppressing antiviral IFN-I signaling via a non-canonical, SCF-independent mechanism), NLRX1 (facilitating virus-induced macrophage apoptosis), Ero1L (limiting ER stress-induced apoptosis), RNASET2 (promoting ovarian cancer), CD147 (modulated by HSP90 competition), ITGB1 (suppressing colorectal cancer invasiveness), SLC3A2 (driving ferroptosis in colitis), and STARD3NL (promoting osteogenesis via Wnt/β-catenin); additionally, FBXO6 interacts with spindle checkpoint proteins Mad2 and BubR1 to regulate mitotic exit, and its own expression is transcriptionally upregulated by TGFβ-SMAD2/3 signaling.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"FBXO6 (Fbs2/FBG2) is the substrate-recognition F-box subunit of an SCF (Skp1-Cul1-F-box) E3 ubiquitin ligase that selects glycoproteins and other substrates for K48-linked polyubiquitination and proteasomal degradation [#0, #8]. Through its FBA domain it binds high-mannose N-glycans (Man3-9GlcNAc2) on misfolded glycoproteins, marking them for ERAD-coupled destruction; crystallography of the FBS2-SKP1 complex bound to the core Man3GlcNAc2 pentasaccharide defines the structural basis of this sugar recognition and reveals a druggable pocket [#0, #12], and a glycan-recognition-defective FBA mutant loses substrate binding across multiple cell lines [#2]. FBXO6 thereby controls the abundance of a broad substrate set: it degrades Chk1 to terminate the S-phase replication checkpoint in response to DNA damage, an activity that modulates sensitivity to genotoxic chemotherapy [#1, #6]; it degrades the ER oxidase Ero1L to restrain ER stress-induced apoptosis [#3]; and it targets MMP14 to limit MMP13 activation and protect cartilage, a protective axis placed downstream of TGF\\u03b2-SMAD2/3 signaling that transcriptionally upregulates FBXO6, with knockout mice developing accelerated osteoarthritis [#7]. FBXO6 also acts in immune and oncogenic contexts, degrading IRF3 through a non-canonical SCF-independent mechanism to suppress type I interferon signaling [#5] and degrading NLRX1 to promote influenza-induced macrophage apoptosis [#9]. Beyond ubiquitin ligase activity, FBXO6 interacts with the spindle checkpoint proteins Mad2 and BubR1 to regulate mitotic exit, and is itself phosphorylated during mitosis [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Established FBXO6's foundational identity as an SCF E3 ligase subunit that recognizes a glycan signal, answering how the cell links N-glycan structure to degradation of misfolded glycoproteins in ERAD.\",\n      \"evidence\": \"Oligosaccharide pull-down defining sugar specificity, co-IP, siRNA knockdown and dominant-negative FBX mutant scored against TCR\\u03b1 degradation\",\n      \"pmids\": [\"12939278\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve the atomic basis of glycan recognition\", \"Substrate repertoire beyond TCR\\u03b1 unknown at this stage\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identified Chk1 as a physiological substrate, showing FBXO6 terminates the S-phase replication checkpoint and that low FBXO6 confers genotoxic drug resistance.\",\n      \"evidence\": \"Reciprocal co-IP, in vivo ubiquitination assay, RNAi and stability assays in cancer cells and breast tumor tissue\",\n      \"pmids\": [\"19716789\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Chk1 recognition is glycan-dependent or via a distinct C-terminal degron\", \"Relationship to canonical SCF assembly for this substrate\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Generalized the glycan-recognition mechanism by mapping a high-confidence N-glycoprotein interactome dependent on an intact FBA domain.\",\n      \"evidence\": \"Affinity purification with LC-MS across 293T, HeLa, Jurkat comparing wild-type vs glycan-recognition mutant FBXO6\",\n      \"pmids\": [\"22268729\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Interactions not validated as productive ubiquitination substrates\", \"Functional consequence of each interaction not tested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Connected FBXO6 to ER redox homeostasis by showing degradation of Ero1L restrains ER stress-induced apoptosis.\",\n      \"evidence\": \"In vivo ubiquitination, stability western blots, CCK8/FACS apoptosis assays with overexpression and RNAi\",\n      \"pmids\": [\"27855403\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; reciprocal validation limited\", \"Whether degradation is glycan-dependent not addressed\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Revealed a degradation-independent mitotic role, with FBXO6 binding Mad2 and BubR1 to inactivate the spindle assembly checkpoint.\",\n      \"evidence\": \"Co-IP, overexpression in HeLa, nocodazole arrest/release, flow cytometry and microscopy of segregation defects\",\n      \"pmids\": [\"30526252\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether the interaction is ubiquitination-coupled or purely scaffolding unclear\", \"Endogenous-level requirement not established\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Defined a non-canonical, SCF-independent activity in which FBXO6 degrades IRF3 to suppress type I interferon antiviral signaling.\",\n      \"evidence\": \"Co-IP with FBA-IAD domain mapping, ubiquitination and IFN-I reporter assays in HEK293T and A549\",\n      \"pmids\": [\"31308089\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of SCF-independent ubiquitin transfer unresolved\", \"In vivo antiviral consequence not tested in this study\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Corroborated Chk1 as a substrate in an independent cancer context, linking FBXO6 to cisplatin sensitization in NSCLC.\",\n      \"evidence\": \"Cell-based assays, Chk1 protein/phospho western blots, cisplatin sensitivity with overexpression and knockdown\",\n      \"pmids\": [\"31140586\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vivo validation\", \"Direct ubiquitination not re-demonstrated\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Established a TGF\\u03b2-SMAD2/3 \\u2192 FBXO6 \\u2192 MMP14 protective axis in cartilage with strong genetic causality for osteoarthritis.\",\n      \"evidence\": \"Reciprocal co-IP, in vivo ubiquitination, global and Col2a1-CreER conditional knockout mice, SMAD2/3 epistasis, rescue\",\n      \"pmids\": [\"32409323\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether MMP14 recognition uses the glycan-binding pocket not resolved\", \"Generalizability of TGF\\u03b2-driven induction to other tissues\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified RNASET2 as a K48-linked ubiquitination substrate, linking FBXO6 to ovarian cancer progression.\",\n      \"evidence\": \"Co-IP, K48-specific in vivo ubiquitination, FBA domain deletion, siRNA and rescue in ovarian cancer cells\",\n      \"pmids\": [\"33767133\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"In vivo tumor validation limited\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Showed FBXO6 activity is itself regulated by competing chaperone interactions, with HSP90 binding FBXO6 to protect CD147 and confer radioresistance.\",\n      \"evidence\": \"Proteomics, co-IP, ubiquitination assay, 17-AAG HSP90 inhibition, clonogenic survival in cervical cancer cells\",\n      \"pmids\": [\"35043518\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of HSP90-FBXO6 competition unknown\", \"Single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Extended the antiviral role in vivo, with FBXO6 degrading NLRX1 to promote influenza-induced macrophage apoptosis and dampen type I IFN.\",\n      \"evidence\": \"Co-IP, FBXO6 knockout mice and macrophage shRNA, in vivo IAV infection, flow cytometry, IFN measurement\",\n      \"pmids\": [\"36217277\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct ubiquitination of NLRX1 not fully demonstrated\", \"Relationship to the IRF3 axis not reconciled\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Implicated an RNA-binding cofactor, MSI2, cooperating with FBXO6 to ubiquitinate RNASET2 in vascular smooth muscle phenotypic switching.\",\n      \"evidence\": \"RIP, co-IP, siRNA, migration assays and atherosclerosis mouse model\",\n      \"pmids\": [\"37633478\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single Co-IP for MSI2-FBXO6; not reciprocally validated\", \"FBXO6-mediated ubiquitination inferred rather than directly shown here\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Resolved the atomic mechanism of glycan recognition, providing the structural basis for SCFFbs2 sugar binding and a druggable pocket.\",\n      \"evidence\": \"X-ray crystal structure of bovine FBS2-SKP1 with Man3GlcNAc2, complemented by NMR and in silico docking\",\n      \"pmids\": [\"39171510\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structure of FBXO6 bound to a full glycoprotein substrate\", \"Druggability not yet validated by chemical probes\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Expanded the substrate set to ITGB1, SLC3A2, and STARD3NL, linking FBXO6 degradation activity to colorectal cancer invasion, colitis ferroptosis, and Wnt-driven osteogenesis respectively.\",\n      \"evidence\": \"Co-IP/MS substrate identification, K48 ubiquitination assays, knockdown/overexpression rescue, xenograft and disease models\",\n      \"pmids\": [\"41857001\", \"41741720\", \"41483826\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"SLC3A2 and STARD3NL findings are single-lab with limited orthogonal validation\", \"STARD3NL degradation mechanism not fully reconstituted\", \"Whether each substrate is recognized via the glycan pocket unaddressed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How FBXO6 discriminates among its many reported substrates \\u2014 glycan-dependent versus degron-based versus SCF-independent recognition \\u2014 and what governs context-specific substrate choice across tissues remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No unified model reconciling glycan recognition with non-glycan substrates like Chk1 and IRF3\", \"Structural basis of substrate selection beyond the glycan pocket unknown\", \"Mechanism of SCF-independent ubiquitination not characterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 3, 7, 8, 13]},\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [0, 1, 8]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 2, 12]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 1, 7, 8]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [1, 4]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [5, 9]}\n    ],\n    \"complexes\": [\"SCF (Skp1-Cul1-F-box) E3 ubiquitin ligase\"],\n    \"partners\": [\"SKP1\", \"Chk1\", \"MMP14\", \"IRF3\", \"NLRX1\", \"Mad2\", \"BubR1\", \"HSP90\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":5,"faith_total":5,"faith_pct":100.0}}