{"gene":"UBL3","run_date":"2026-04-28T21:43:00","timeline":{"discoveries":[{"year":2018,"finding":"UBL3 acts as a post-translational modification (PTM) factor that directly modifies Ras (and oncogenic RasG12V), and UBL3 modification is required for sorting of UBL3 itself and client proteins to multivesicular bodies (MVBs) and small extracellular vesicles (sEVs); Ubl3-knockout mice show a 60% reduction in total sEV protein content.","method":"Proteomics (1241 UBL3-interacting proteins identified), in vitro/cell-based UBL3 modification assay, Ubl3-knockout mouse model with sEV purification and quantification","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP/proteomics plus KO mouse with defined quantitative phenotype, replicated across multiple substrates","pmids":["30258067"],"is_preprint":false},{"year":2022,"finding":"UBL3 is a necessary adaptor for MARCH1-mediated ubiquitination of MHC II and CD86; this function requires UBL3 plasma membrane anchoring via prenylation. Loss of UBL3 elevates surface MHC II and CD86 on antigen-presenting cells and impairs MARCH1 substrate ubiquitination.","method":"Genome-wide CRISPR knockout screen, Ubl3-deficient mice, flow cytometry for surface MHC II/CD86, ubiquitination assays, prenylation mutant analysis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — genome-wide CRISPR screen plus KO mouse with multiple orthogonal functional readouts and mechanistic dissection of prenylation requirement","pmids":["35411049"],"is_preprint":false},{"year":2023,"finding":"PDE6D interacts with prenylated UBL3 and mediates its trafficking to primary cilia; UBL3 localizes inside the cilium and in vesicle-like structures at the ciliary base in a prenylation-dependent manner, and affinity proteomics of UBL3 confirmed its strong interaction with PDE6D and association with proteins regulating sEVs and ciliogenesis.","method":"Affinity proteomics (PDE6D pulldown), immunofluorescence localization in photoreceptors, prenylation mutant analysis","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 2/3 — affinity proteomics plus localization with prenylation mutant, single lab","pmids":["36672247"],"is_preprint":false},{"year":2023,"finding":"UBL3 interacts with alpha-synuclein (α-syn) in cells; the C-terminal cysteine residues of UBL3 (important for its PTM function) are not essential for this interaction. The UBL3–α-syn interaction is upregulated by MPP+ exposure and downregulated by the EGFR pathway inhibitor osimertinib.","method":"Split Gaussia luciferase complementation assay, co-immunoprecipitation","journal":"Biomedicines","confidence":"Medium","confidence_rationale":"Tier 3 — two complementary cell-based interaction assays from a single lab","pmids":["37371780"],"is_preprint":false},{"year":2023,"finding":"Silencing MGST3 (microsomal glutathione S-transferase 3) downregulates the UBL3–α-syn interaction and reduces their co-localization; oxidative stress induced by H2O2 similarly downregulates this interaction, linking MGST3's antioxidant function to UBL3–α-syn complex stability.","method":"Split Gaussia luciferase complementation assay, RNA interference screen (8 candidates), immunocytochemistry co-localization","journal":"Biomedicines","confidence":"Medium","confidence_rationale":"Tier 3 — RNAi screen plus cell-based interaction assay and imaging, single lab","pmids":["37760932"],"is_preprint":false},{"year":2024,"finding":"MGST3 overexpression upregulates the UBL3–α-syn interaction and promotes translocation of intracellular α-syn to the extracellular compartment via sEVs; this effect is rescued (reduced) under excess oxidative stress, placing MGST3 upstream of the UBL3-dependent sEV sorting of α-syn.","method":"Split Gaussia luciferase complementation assay, MGST3 overexpression, immunocytochemistry, Western blot, RT-qPCR","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 3 — gain-of-function with cell-based interaction and secretion assay, single lab","pmids":["39000460"],"is_preprint":false},{"year":2024,"finding":"UBL3 interacts with 35 novel brain proteins in vivo (including RNA-binding proteins FUS and HPRT1, and LYPLA1); endogenous UBL3 association with FUS, HPRT1, and LYPLA1 was confirmed by IP-western blot from mouse cerebral cortex, expanding the UBL3 interactome in the context of neurodegeneration.","method":"Avidin-based immunoprecipitation from transgenic biotinylated-UBL3 mice, mass spectrometry, IP-western blot","journal":"Molecular brain","confidence":"Medium","confidence_rationale":"Tier 2/3 — in vivo affinity proteomics with transgenic mouse, validated by endogenous IP, single lab","pmids":["39148092"],"is_preprint":false},{"year":2024,"finding":"UBL3 interacts with polyQ-expanded mutant huntingtin fragments (mHTT) and modulates their intracellular sorting; UBL3-positive inclusions were detected in cytoplasm and nuclei of striatal neurons in HD patient brain tissue.","method":"Split Gaussia luciferase complementation assay, co-immunoprecipitation, HiBiT lytic detection assay (intracellular sorting), immunocytochemistry, immunohistochemistry on HD postmortem brain","journal":"Neurology international","confidence":"Medium","confidence_rationale":"Tier 3 — multiple cell-based assays plus patient tissue validation, single lab","pmids":["39449505"],"is_preprint":false},{"year":2024,"finding":"UBL3 overexpression enhances EV-mediated secretion of a reporter protein (Achilles) into conditioned media of MDA-MB-231 cells; UBL3-KO reduces this secretion, confirming UBL3's role in EV cargo loading.","method":"Dual-reporter bioluminescence/fluorescence system, UBL3-KO cells, stable overexpression, EV uptake luciferase assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2/3 — KO and overexpression with functional reporter readout, single lab","pmids":["39182355"],"is_preprint":false},{"year":2025,"finding":"UBL3 promotes VEGFR inhibitor resistance in renal cell carcinoma by (1) forming a complex with NOTCH2 and ADAM17 simultaneously, accelerating ADAM17-mediated cleavage of NOTCH2, and (2) sorting UBL3-modified NOTCH2 into sEVs that are taken up by recipient cells to activate NOTCH signaling (via NOTCH-PTEN-AKT and NOTCH-FOS pathways), suppressing apoptosis.","method":"Genome-wide CRISPR/Cas9 library screen, western blot, RNA sequencing, chromatin immunoprecipitation, sEV isolation, Astral-DIA proteomics, co-immunoprecipitation (UBL3-NOTCH2-ADAM17 complex), in vitro and in vivo functional assays, LNP-CRISPR rescue","journal":"Drug resistance updates","confidence":"High","confidence_rationale":"Tier 2 — genome-wide screen plus multiple orthogonal mechanistic assays (co-IP of ternary complex, proteomics, sEV transfer, in vivo rescue) in single rigorous study","pmids":["41418537"],"is_preprint":false},{"year":2026,"finding":"UBL3 regulates MHC II levels on thymic epithelial cells (TECs) and participates in the early CD4+ CD8low CD69+ stage of CD4+ T cell positive selection; deleting UBL3 in Cd83anu/anu mice increases surface MHC II on TECs and rescues CD4+ T cell positive selection, placing UBL3 in the CD83-dependent MHC II ubiquitination pathway in thymus.","method":"Genetic epistasis (Cd83anu/anu Ubl3-/- double-mutant mice), flow cytometry of thymocyte populations and surface MHC II","journal":"European journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 — clean double-KO epistasis with defined cellular phenotype, single lab","pmids":["41636204"],"is_preprint":false}],"current_model":"UBL3 is a prenylated, membrane-anchored ubiquitin-like protein that functions as a post-translational modifier: it covalently modifies client proteins (including Ras, NOTCH2, and α-synuclein), acting as a sorting signal that directs cargo into multivesicular bodies and small extracellular vesicles, while also serving as an essential adaptor for MARCH1-mediated ubiquitination of MHC II and CD86 at the plasma membrane (requiring its prenylation-dependent membrane anchoring), and trafficking to primary cilia via PDE6D."},"narrative":{"teleology":[{"year":2018,"claim":"The fundamental question of UBL3's molecular function was answered: rather than acting as a conventional ubiquitin-like conjugate in protein degradation, UBL3 operates as a PTM factor that modifies client proteins (e.g., Ras) and serves as a sorting signal directing cargo into MVBs and sEVs, with knockout mice showing a dramatic reduction in sEV protein content.","evidence":"Proteomics identifying 1241 interactors, in vitro UBL3 modification assays, and Ubl3-KO mouse sEV quantification","pmids":["30258067"],"confidence":"High","gaps":["The enzymatic machinery (E1/E2/E3) catalyzing UBL3 conjugation to substrates remains unidentified","The structural basis of UBL3 attachment to client proteins is undefined","Whether UBL3 modification is reversible (deconjugation) is unknown"]},{"year":2022,"claim":"A genome-wide CRISPR screen revealed that UBL3 has a second, mechanistically distinct function as an essential adaptor for MARCH1-mediated ubiquitination of MHC II and CD86, requiring prenylation-dependent plasma membrane anchoring rather than its PTM/conjugation activity, establishing UBL3 as a critical regulator of antigen-presenting cell surface phenotype.","evidence":"CRISPR KO screen, Ubl3-deficient mice with flow cytometry for MHC II/CD86, ubiquitination assays, prenylation mutant analysis","pmids":["35411049"],"confidence":"High","gaps":["Whether UBL3 directly bridges MARCH1 to its substrates via a defined binding interface is not resolved","The relationship between UBL3's adaptor role for MARCH1 and its sEV sorting function is unclear"]},{"year":2023,"claim":"The question of how UBL3 reaches specific subcellular compartments was addressed: PDE6D binds prenylated UBL3 and mediates its trafficking to primary cilia, where UBL3 localizes in a prenylation-dependent manner, revealing a ciliary function and extending UBL3's role beyond the endosomal/plasma membrane compartments.","evidence":"Affinity proteomics, immunofluorescence in photoreceptors, prenylation mutant analysis","pmids":["36672247"],"confidence":"Medium","gaps":["The functional consequence of UBL3 ciliary localization (e.g., ciliary signaling, cargo sorting) is unknown","Whether UBL3 modifies ciliary proteins as a PTM factor has not been tested","Single-lab finding awaits independent confirmation"]},{"year":2023,"claim":"UBL3 was linked to neurodegeneration-associated proteins: it interacts with α-synuclein (independent of its C-terminal PTM cysteines), and this interaction is modulated by the mitochondrial toxin MPP+ and regulated by the antioxidant enzyme MGST3, with MGST3 overexpression promoting UBL3-dependent sEV secretion of α-synuclein.","evidence":"Split luciferase complementation, co-IP, RNAi screen, MGST3 overexpression with sEV secretion assays","pmids":["37371780","37760932","39000460"],"confidence":"Medium","gaps":["Whether UBL3-dependent α-synuclein sEV release is pathogenic or protective in vivo is unknown","The mechanism by which MGST3 modulates UBL3–α-synuclein interaction is indirect and undefined","All studies from single lab"]},{"year":2024,"claim":"The UBL3 brain interactome was expanded in vivo, revealing interactions with RNA-binding proteins (FUS) and metabolic enzymes (HPRT1, LYPLA1), and UBL3 was shown to interact with polyQ-expanded huntingtin fragments and co-localize with mHTT inclusions in Huntington's disease patient brain, suggesting UBL3 participates in intracellular sorting of aggregation-prone proteins.","evidence":"Biotinylated-UBL3 transgenic mouse proteomics with endogenous IP validation; split luciferase, co-IP, and immunohistochemistry on HD postmortem brain","pmids":["39148092","39449505"],"confidence":"Medium","gaps":["Whether UBL3 modification of mHTT or FUS alters their aggregation or toxicity in vivo is untested","The functional significance of UBL3 interaction with RNA-binding proteins is unknown","Findings from single lab require independent validation"]},{"year":2025,"claim":"UBL3's sEV sorting function was shown to have direct pathological relevance: UBL3 forms a ternary complex with NOTCH2 and ADAM17, accelerates NOTCH2 cleavage, and packages modified NOTCH2 into sEVs that activate NOTCH signaling in recipient cells, driving VEGFR inhibitor resistance in renal cell carcinoma through NOTCH-PTEN-AKT and NOTCH-FOS pathways.","evidence":"Genome-wide CRISPR screen, co-IP of ternary complex, sEV proteomics, RNA-seq, ChIP, in vivo LNP-CRISPR rescue","pmids":["41418537"],"confidence":"High","gaps":["Whether UBL3-NOTCH2 sEV-mediated resistance operates in other cancer types is unknown","The precise UBL3 modification site(s) on NOTCH2 are not mapped"]},{"year":2026,"claim":"Genetic epistasis in double-mutant mice established that UBL3 functions in the CD83-dependent MHC II ubiquitination pathway in thymic epithelial cells, with UBL3 deletion rescuing CD4+ T cell positive selection in CD83-deficient animals, placing UBL3 as a physiological regulator of T cell development.","evidence":"Cd83anu/anu Ubl3−/− double-KO mice, flow cytometry of thymocyte subsets and TEC surface MHC II","pmids":["41636204"],"confidence":"Medium","gaps":["Whether UBL3 acts through MARCH1 or an alternative E3 ligase in thymic epithelial cells is not resolved","The broader impact on immune tolerance and autoimmunity is untested"]},{"year":null,"claim":"Key unresolved questions include the identity of the E1/E2/E3 enzymatic cascade for UBL3 conjugation, the structural basis of UBL3 attachment to substrates, whether UBL3 modification is reversible, and the in vivo consequences of UBL3-dependent sEV transfer of neurodegeneration-associated proteins.","evidence":"","pmids":[],"confidence":"Low","gaps":["No E1, E2, or E3 enzyme for UBL3 conjugation has been identified","No crystal or cryo-EM structure of UBL3 in complex with any substrate exists","Whether UBL3-mediated sEV sorting of α-synuclein/mHTT is protective or pathogenic in vivo remains untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0031386","term_label":"protein tag activity","supporting_discovery_ids":[0,9]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,10]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[0,8]},{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[2]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[0,8,9]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[1,10]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,1]}],"complexes":["UBL3-NOTCH2-ADAM17 ternary complex"],"partners":["NOTCH2","ADAM17","MARCH1","PDE6D","SNCA","MGST3","FUS","HTT"],"other_free_text":[]},"mechanistic_narrative":"UBL3 is a prenylated ubiquitin-like protein that functions as a post-translational modification factor and membrane-anchored sorting signal, directing diverse client proteins into multivesicular bodies and small extracellular vesicles (sEVs). UBL3 covalently modifies substrates including Ras, NOTCH2, and α-synuclein, and Ubl3-knockout mice show a ~60% reduction in total sEV protein content, establishing UBL3 as a major determinant of EV cargo loading [PMID:30258067, PMID:39182355]. UBL3 also serves as an essential prenylation-dependent adaptor for MARCH1-mediated ubiquitination of MHC class II and CD86 on antigen-presenting cells, and genetic epistasis with CD83 places UBL3 in the MHC II ubiquitination pathway that controls CD4⁺ T cell positive selection in the thymus [PMID:35411049, PMID:41636204]. In addition, UBL3 forms a ternary complex with NOTCH2 and ADAM17, promoting ADAM17-mediated NOTCH2 cleavage and sEV-mediated transfer of activated NOTCH2 to recipient cells, thereby driving VEGFR inhibitor resistance in renal cell carcinoma [PMID:41418537]."},"prefetch_data":{"uniprot":{"accession":"O95164","full_name":"Ubiquitin-like protein 3","aliases":["Membrane-anchored ubiquitin-fold protein","HsMUB","MUB","Protein HCG-1"],"length_aa":117,"mass_kda":13.2,"function":"","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/O95164/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/UBL3","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/UBL3","total_profiled":1310},"omim":[{"mim_id":"606849","title":"UBIQUITIN-LIKE 5; UBL5","url":"https://www.omim.org/entry/606849"},{"mim_id":"604711","title":"UBIQUITIN-LIKE 3; UBL3","url":"https://www.omim.org/entry/604711"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Centrosome","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/UBL3"},"hgnc":{"alias_symbol":["HCG-1","DKFZP434K151","FLJ32018"],"prev_symbol":["PNSC1"]},"alphafold":{"accession":"O95164","domains":[{"cath_id":"3.10.20.90","chopping":"9-86","consensus_level":"high","plddt":88.0981,"start":9,"end":86}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O95164","model_url":"https://alphafold.ebi.ac.uk/files/AF-O95164-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O95164-F1-predicted_aligned_error_v6.png","plddt_mean":78.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=UBL3","jax_strain_url":"https://www.jax.org/strain/search?query=UBL3"},"sequence":{"accession":"O95164","fasta_url":"https://rest.uniprot.org/uniprotkb/O95164.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O95164/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O95164"}},"corpus_meta":[{"pmid":"30258067","id":"PMC_30258067","title":"UBL3 modification influences protein sorting to small extracellular vesicles.","date":"2018","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/30258067","citation_count":69,"is_preprint":false},{"pmid":"35411049","id":"PMC_35411049","title":"Ubiquitin-like protein 3 (UBL3) is required for MARCH ubiquitination of major histocompatibility complex class II and CD86.","date":"2022","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/35411049","citation_count":28,"is_preprint":false},{"pmid":"32296577","id":"PMC_32296577","title":"Identification of a potential tumor suppressor gene, UBL3, in non-small cell lung cancer.","date":"2020","source":"Cancer biology & medicine","url":"https://pubmed.ncbi.nlm.nih.gov/32296577","citation_count":15,"is_preprint":false},{"pmid":"10375635","id":"PMC_10375635","title":"Cloning, mapping and expression of UBL3, a novel ubiquitin-like gene.","date":"1999","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/10375635","citation_count":11,"is_preprint":false},{"pmid":"37371780","id":"PMC_37371780","title":"UBL3 Interacts with Alpha-Synuclein in Cells and the Interaction Is Downregulated by the EGFR Pathway Inhibitor Osimertinib.","date":"2023","source":"Biomedicines","url":"https://pubmed.ncbi.nlm.nih.gov/37371780","citation_count":9,"is_preprint":false},{"pmid":"36674743","id":"PMC_36674743","title":"A New Potential Therapeutic Target for Cancer in Ubiquitin-Like Proteins-UBL3.","date":"2023","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/36674743","citation_count":7,"is_preprint":false},{"pmid":"36672247","id":"PMC_36672247","title":"PDE6D Mediates Trafficking of Prenylated Proteins NIM1K and UBL3 to Primary Cilia.","date":"2023","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/36672247","citation_count":7,"is_preprint":false},{"pmid":"37760932","id":"PMC_37760932","title":"UBL3 Interaction with α-Synuclein Is Downregulated by Silencing MGST3.","date":"2023","source":"Biomedicines","url":"https://pubmed.ncbi.nlm.nih.gov/37760932","citation_count":7,"is_preprint":false},{"pmid":"39000460","id":"PMC_39000460","title":"Alpha-Synuclein Interaction with UBL3 Is Upregulated by Microsomal Glutathione S-Transferase 3, Leading to Increased Extracellular Transport of the Alpha-Synuclein under Oxidative Stress.","date":"2024","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/39000460","citation_count":6,"is_preprint":false},{"pmid":"39148092","id":"PMC_39148092","title":"Comprehensive identification of ubiquitin-like 3 (UBL3)-interacting proteins in the mouse brain.","date":"2024","source":"Molecular brain","url":"https://pubmed.ncbi.nlm.nih.gov/39148092","citation_count":2,"is_preprint":false},{"pmid":"39449505","id":"PMC_39449505","title":"UBL3 Interacts with PolyQ-Expanded Huntingtin Fragments and Modifies Their Intracellular Sorting.","date":"2024","source":"Neurology international","url":"https://pubmed.ncbi.nlm.nih.gov/39449505","citation_count":1,"is_preprint":false},{"pmid":"41418537","id":"PMC_41418537","title":"UBL3 governs VEGFR inhibitor resistance by activating NOTCH signaling in renal cell carcinoma.","date":"2025","source":"Drug resistance updates : reviews and commentaries in antimicrobial and anticancer chemotherapy","url":"https://pubmed.ncbi.nlm.nih.gov/41418537","citation_count":0,"is_preprint":false},{"pmid":"39182355","id":"PMC_39182355","title":"UBL3 overexpression enhances EV-mediated Achilles protein secretion in conditioned media of MDA-MB-231 cells.","date":"2024","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/39182355","citation_count":0,"is_preprint":false},{"pmid":"40548297","id":"PMC_40548297","title":"Bone Mesenchymal Stromal Cell-Derived Extracellular Vesicles Protect Articular Cartilage Through Regulating tRF-Gln-TTG-019/UBL3.","date":"2025","source":"Mediators of inflammation","url":"https://pubmed.ncbi.nlm.nih.gov/40548297","citation_count":0,"is_preprint":false},{"pmid":"41636204","id":"PMC_41636204","title":"UBL3 Participates in the Early Stages of CD83-Dependent CD4+ T Cell Selection.","date":"2026","source":"European journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/41636204","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.10.09.25337647","title":"Machine-learning-based analysis of transcriptomics data for the identification of molecular signatures in cancer","date":"2025-10-10","source":"bioRxiv","url":"https://doi.org/10.1101/2025.10.09.25337647","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9795,"output_tokens":2785,"usd":0.03558},"stage2":{"model":"claude-opus-4-6","input_tokens":6154,"output_tokens":2741,"usd":0.148943},"total_usd":0.184523,"stage1_batch_id":"msgbatch_01RPbVc9PDH9zQmYK5Hs6srm","stage2_batch_id":"msgbatch_01JVbVLzeKN2yVrsGp3zC8aM","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2018,\n      \"finding\": \"UBL3 acts as a post-translational modification (PTM) factor that directly modifies Ras (and oncogenic RasG12V), and UBL3 modification is required for sorting of UBL3 itself and client proteins to multivesicular bodies (MVBs) and small extracellular vesicles (sEVs); Ubl3-knockout mice show a 60% reduction in total sEV protein content.\",\n      \"method\": \"Proteomics (1241 UBL3-interacting proteins identified), in vitro/cell-based UBL3 modification assay, Ubl3-knockout mouse model with sEV purification and quantification\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP/proteomics plus KO mouse with defined quantitative phenotype, replicated across multiple substrates\",\n      \"pmids\": [\"30258067\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"UBL3 is a necessary adaptor for MARCH1-mediated ubiquitination of MHC II and CD86; this function requires UBL3 plasma membrane anchoring via prenylation. Loss of UBL3 elevates surface MHC II and CD86 on antigen-presenting cells and impairs MARCH1 substrate ubiquitination.\",\n      \"method\": \"Genome-wide CRISPR knockout screen, Ubl3-deficient mice, flow cytometry for surface MHC II/CD86, ubiquitination assays, prenylation mutant analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genome-wide CRISPR screen plus KO mouse with multiple orthogonal functional readouts and mechanistic dissection of prenylation requirement\",\n      \"pmids\": [\"35411049\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PDE6D interacts with prenylated UBL3 and mediates its trafficking to primary cilia; UBL3 localizes inside the cilium and in vesicle-like structures at the ciliary base in a prenylation-dependent manner, and affinity proteomics of UBL3 confirmed its strong interaction with PDE6D and association with proteins regulating sEVs and ciliogenesis.\",\n      \"method\": \"Affinity proteomics (PDE6D pulldown), immunofluorescence localization in photoreceptors, prenylation mutant analysis\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — affinity proteomics plus localization with prenylation mutant, single lab\",\n      \"pmids\": [\"36672247\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"UBL3 interacts with alpha-synuclein (α-syn) in cells; the C-terminal cysteine residues of UBL3 (important for its PTM function) are not essential for this interaction. The UBL3–α-syn interaction is upregulated by MPP+ exposure and downregulated by the EGFR pathway inhibitor osimertinib.\",\n      \"method\": \"Split Gaussia luciferase complementation assay, co-immunoprecipitation\",\n      \"journal\": \"Biomedicines\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — two complementary cell-based interaction assays from a single lab\",\n      \"pmids\": [\"37371780\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Silencing MGST3 (microsomal glutathione S-transferase 3) downregulates the UBL3–α-syn interaction and reduces their co-localization; oxidative stress induced by H2O2 similarly downregulates this interaction, linking MGST3's antioxidant function to UBL3–α-syn complex stability.\",\n      \"method\": \"Split Gaussia luciferase complementation assay, RNA interference screen (8 candidates), immunocytochemistry co-localization\",\n      \"journal\": \"Biomedicines\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — RNAi screen plus cell-based interaction assay and imaging, single lab\",\n      \"pmids\": [\"37760932\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MGST3 overexpression upregulates the UBL3–α-syn interaction and promotes translocation of intracellular α-syn to the extracellular compartment via sEVs; this effect is rescued (reduced) under excess oxidative stress, placing MGST3 upstream of the UBL3-dependent sEV sorting of α-syn.\",\n      \"method\": \"Split Gaussia luciferase complementation assay, MGST3 overexpression, immunocytochemistry, Western blot, RT-qPCR\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — gain-of-function with cell-based interaction and secretion assay, single lab\",\n      \"pmids\": [\"39000460\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"UBL3 interacts with 35 novel brain proteins in vivo (including RNA-binding proteins FUS and HPRT1, and LYPLA1); endogenous UBL3 association with FUS, HPRT1, and LYPLA1 was confirmed by IP-western blot from mouse cerebral cortex, expanding the UBL3 interactome in the context of neurodegeneration.\",\n      \"method\": \"Avidin-based immunoprecipitation from transgenic biotinylated-UBL3 mice, mass spectrometry, IP-western blot\",\n      \"journal\": \"Molecular brain\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — in vivo affinity proteomics with transgenic mouse, validated by endogenous IP, single lab\",\n      \"pmids\": [\"39148092\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"UBL3 interacts with polyQ-expanded mutant huntingtin fragments (mHTT) and modulates their intracellular sorting; UBL3-positive inclusions were detected in cytoplasm and nuclei of striatal neurons in HD patient brain tissue.\",\n      \"method\": \"Split Gaussia luciferase complementation assay, co-immunoprecipitation, HiBiT lytic detection assay (intracellular sorting), immunocytochemistry, immunohistochemistry on HD postmortem brain\",\n      \"journal\": \"Neurology international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — multiple cell-based assays plus patient tissue validation, single lab\",\n      \"pmids\": [\"39449505\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"UBL3 overexpression enhances EV-mediated secretion of a reporter protein (Achilles) into conditioned media of MDA-MB-231 cells; UBL3-KO reduces this secretion, confirming UBL3's role in EV cargo loading.\",\n      \"method\": \"Dual-reporter bioluminescence/fluorescence system, UBL3-KO cells, stable overexpression, EV uptake luciferase assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — KO and overexpression with functional reporter readout, single lab\",\n      \"pmids\": [\"39182355\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"UBL3 promotes VEGFR inhibitor resistance in renal cell carcinoma by (1) forming a complex with NOTCH2 and ADAM17 simultaneously, accelerating ADAM17-mediated cleavage of NOTCH2, and (2) sorting UBL3-modified NOTCH2 into sEVs that are taken up by recipient cells to activate NOTCH signaling (via NOTCH-PTEN-AKT and NOTCH-FOS pathways), suppressing apoptosis.\",\n      \"method\": \"Genome-wide CRISPR/Cas9 library screen, western blot, RNA sequencing, chromatin immunoprecipitation, sEV isolation, Astral-DIA proteomics, co-immunoprecipitation (UBL3-NOTCH2-ADAM17 complex), in vitro and in vivo functional assays, LNP-CRISPR rescue\",\n      \"journal\": \"Drug resistance updates\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genome-wide screen plus multiple orthogonal mechanistic assays (co-IP of ternary complex, proteomics, sEV transfer, in vivo rescue) in single rigorous study\",\n      \"pmids\": [\"41418537\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"UBL3 regulates MHC II levels on thymic epithelial cells (TECs) and participates in the early CD4+ CD8low CD69+ stage of CD4+ T cell positive selection; deleting UBL3 in Cd83anu/anu mice increases surface MHC II on TECs and rescues CD4+ T cell positive selection, placing UBL3 in the CD83-dependent MHC II ubiquitination pathway in thymus.\",\n      \"method\": \"Genetic epistasis (Cd83anu/anu Ubl3-/- double-mutant mice), flow cytometry of thymocyte populations and surface MHC II\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean double-KO epistasis with defined cellular phenotype, single lab\",\n      \"pmids\": [\"41636204\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"UBL3 is a prenylated, membrane-anchored ubiquitin-like protein that functions as a post-translational modifier: it covalently modifies client proteins (including Ras, NOTCH2, and α-synuclein), acting as a sorting signal that directs cargo into multivesicular bodies and small extracellular vesicles, while also serving as an essential adaptor for MARCH1-mediated ubiquitination of MHC II and CD86 at the plasma membrane (requiring its prenylation-dependent membrane anchoring), and trafficking to primary cilia via PDE6D.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"UBL3 is a prenylated ubiquitin-like protein that functions as a post-translational modification factor and membrane-anchored sorting signal, directing diverse client proteins into multivesicular bodies and small extracellular vesicles (sEVs). UBL3 covalently modifies substrates including Ras, NOTCH2, and α-synuclein, and Ubl3-knockout mice show a ~60% reduction in total sEV protein content, establishing UBL3 as a major determinant of EV cargo loading [PMID:30258067, PMID:39182355]. UBL3 also serves as an essential prenylation-dependent adaptor for MARCH1-mediated ubiquitination of MHC class II and CD86 on antigen-presenting cells, and genetic epistasis with CD83 places UBL3 in the MHC II ubiquitination pathway that controls CD4⁺ T cell positive selection in the thymus [PMID:35411049, PMID:41636204]. In addition, UBL3 forms a ternary complex with NOTCH2 and ADAM17, promoting ADAM17-mediated NOTCH2 cleavage and sEV-mediated transfer of activated NOTCH2 to recipient cells, thereby driving VEGFR inhibitor resistance in renal cell carcinoma [PMID:41418537].\",\n  \"teleology\": [\n    {\n      \"year\": 2018,\n      \"claim\": \"The fundamental question of UBL3's molecular function was answered: rather than acting as a conventional ubiquitin-like conjugate in protein degradation, UBL3 operates as a PTM factor that modifies client proteins (e.g., Ras) and serves as a sorting signal directing cargo into MVBs and sEVs, with knockout mice showing a dramatic reduction in sEV protein content.\",\n      \"evidence\": \"Proteomics identifying 1241 interactors, in vitro UBL3 modification assays, and Ubl3-KO mouse sEV quantification\",\n      \"pmids\": [\"30258067\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The enzymatic machinery (E1/E2/E3) catalyzing UBL3 conjugation to substrates remains unidentified\",\n        \"The structural basis of UBL3 attachment to client proteins is undefined\",\n        \"Whether UBL3 modification is reversible (deconjugation) is unknown\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"A genome-wide CRISPR screen revealed that UBL3 has a second, mechanistically distinct function as an essential adaptor for MARCH1-mediated ubiquitination of MHC II and CD86, requiring prenylation-dependent plasma membrane anchoring rather than its PTM/conjugation activity, establishing UBL3 as a critical regulator of antigen-presenting cell surface phenotype.\",\n      \"evidence\": \"CRISPR KO screen, Ubl3-deficient mice with flow cytometry for MHC II/CD86, ubiquitination assays, prenylation mutant analysis\",\n      \"pmids\": [\"35411049\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether UBL3 directly bridges MARCH1 to its substrates via a defined binding interface is not resolved\",\n        \"The relationship between UBL3's adaptor role for MARCH1 and its sEV sorting function is unclear\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"The question of how UBL3 reaches specific subcellular compartments was addressed: PDE6D binds prenylated UBL3 and mediates its trafficking to primary cilia, where UBL3 localizes in a prenylation-dependent manner, revealing a ciliary function and extending UBL3's role beyond the endosomal/plasma membrane compartments.\",\n      \"evidence\": \"Affinity proteomics, immunofluorescence in photoreceptors, prenylation mutant analysis\",\n      \"pmids\": [\"36672247\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"The functional consequence of UBL3 ciliary localization (e.g., ciliary signaling, cargo sorting) is unknown\",\n        \"Whether UBL3 modifies ciliary proteins as a PTM factor has not been tested\",\n        \"Single-lab finding awaits independent confirmation\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"UBL3 was linked to neurodegeneration-associated proteins: it interacts with α-synuclein (independent of its C-terminal PTM cysteines), and this interaction is modulated by the mitochondrial toxin MPP+ and regulated by the antioxidant enzyme MGST3, with MGST3 overexpression promoting UBL3-dependent sEV secretion of α-synuclein.\",\n      \"evidence\": \"Split luciferase complementation, co-IP, RNAi screen, MGST3 overexpression with sEV secretion assays\",\n      \"pmids\": [\"37371780\", \"37760932\", \"39000460\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether UBL3-dependent α-synuclein sEV release is pathogenic or protective in vivo is unknown\",\n        \"The mechanism by which MGST3 modulates UBL3–α-synuclein interaction is indirect and undefined\",\n        \"All studies from single lab\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"The UBL3 brain interactome was expanded in vivo, revealing interactions with RNA-binding proteins (FUS) and metabolic enzymes (HPRT1, LYPLA1), and UBL3 was shown to interact with polyQ-expanded huntingtin fragments and co-localize with mHTT inclusions in Huntington's disease patient brain, suggesting UBL3 participates in intracellular sorting of aggregation-prone proteins.\",\n      \"evidence\": \"Biotinylated-UBL3 transgenic mouse proteomics with endogenous IP validation; split luciferase, co-IP, and immunohistochemistry on HD postmortem brain\",\n      \"pmids\": [\"39148092\", \"39449505\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether UBL3 modification of mHTT or FUS alters their aggregation or toxicity in vivo is untested\",\n        \"The functional significance of UBL3 interaction with RNA-binding proteins is unknown\",\n        \"Findings from single lab require independent validation\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"UBL3's sEV sorting function was shown to have direct pathological relevance: UBL3 forms a ternary complex with NOTCH2 and ADAM17, accelerates NOTCH2 cleavage, and packages modified NOTCH2 into sEVs that activate NOTCH signaling in recipient cells, driving VEGFR inhibitor resistance in renal cell carcinoma through NOTCH-PTEN-AKT and NOTCH-FOS pathways.\",\n      \"evidence\": \"Genome-wide CRISPR screen, co-IP of ternary complex, sEV proteomics, RNA-seq, ChIP, in vivo LNP-CRISPR rescue\",\n      \"pmids\": [\"41418537\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether UBL3-NOTCH2 sEV-mediated resistance operates in other cancer types is unknown\",\n        \"The precise UBL3 modification site(s) on NOTCH2 are not mapped\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Genetic epistasis in double-mutant mice established that UBL3 functions in the CD83-dependent MHC II ubiquitination pathway in thymic epithelial cells, with UBL3 deletion rescuing CD4+ T cell positive selection in CD83-deficient animals, placing UBL3 as a physiological regulator of T cell development.\",\n      \"evidence\": \"Cd83anu/anu Ubl3−/− double-KO mice, flow cytometry of thymocyte subsets and TEC surface MHC II\",\n      \"pmids\": [\"41636204\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether UBL3 acts through MARCH1 or an alternative E3 ligase in thymic epithelial cells is not resolved\",\n        \"The broader impact on immune tolerance and autoimmunity is untested\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the identity of the E1/E2/E3 enzymatic cascade for UBL3 conjugation, the structural basis of UBL3 attachment to substrates, whether UBL3 modification is reversible, and the in vivo consequences of UBL3-dependent sEV transfer of neurodegeneration-associated proteins.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No E1, E2, or E3 enzyme for UBL3 conjugation has been identified\",\n        \"No crystal or cryo-EM structure of UBL3 in complex with any substrate exists\",\n        \"Whether UBL3-mediated sEV sorting of α-synuclein/mHTT is protective or pathogenic in vivo remains untested\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0031386\", \"supporting_discovery_ids\": [0, 9]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [0, 8]},\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 8, 9]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [1, 10]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"complexes\": [\n      \"UBL3-NOTCH2-ADAM17 ternary complex\"\n    ],\n    \"partners\": [\n      \"NOTCH2\",\n      \"ADAM17\",\n      \"MARCH1\",\n      \"PDE6D\",\n      \"SNCA\",\n      \"MGST3\",\n      \"FUS\",\n      \"HTT\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}