{"gene":"USP40","run_date":"2026-06-11T09:02:06","timeline":{"discoveries":[{"year":2019,"finding":"USP40 physically interacts with CFLARL (c-FLIPL) and performs K48-linked deubiquitination of CFLARL, thereby stabilizing it from proteasomal degradation. GMEB1 acts as a bridge protein that promotes the USP40–CFLARL interaction. USP40 knockdown abolished CFLARL stabilization even upon GMEB1 overexpression, placing USP40 as the catalytic effector downstream of GMEB1 in this complex.","method":"Co-immunoprecipitation, GST pull-down, immunofluorescence, ubiquitination assay, siRNA knockdown, western blotting in NSCLC and 293FT cells","journal":"Journal of experimental & clinical cancer research : CR","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP and GST pull-down with functional knockdown rescue, single lab, multiple orthogonal methods","pmids":["31046799"],"is_preprint":false},{"year":2024,"finding":"USP40 deubiquitinates YAP by removing K48-linked polyubiquitin chains at lysine residues K252 and K315, thereby stabilizing YAP protein in hepatocellular carcinoma cells. USP40 interacts with YAP, and its pro-tumorigenic effects on proliferation, migration, and spheroid formation are YAP-dependent. In turn, YAP transcriptionally activates USP40 expression, forming a positive feedback loop.","method":"Co-immunoprecipitation, ubiquitination assay (site-specific mutagenesis at K252/K315), siRNA knockdown, RNA sequencing, in vivo xenograft, reporter/transcriptional assays","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP with site-directed mutagenesis of ubiquitination sites plus in vivo validation, single lab","pmids":["38537774"],"is_preprint":false},{"year":2024,"finding":"USP40 deubiquitinates heat shock protein HSP90β, leading to its inactivation. This prevents endothelial barrier disruption by reducing RhoA activation and phosphorylation of myosin light chain (MLC) and cofilin, and reduces NF-κB-driven inflammation and ICAM1 expression. EC-targeted USP40 knockout exacerbated experimental lung injury, while lentiviral USP40 overexpression was protective.","method":"Co-immunoprecipitation, ubiquitination assay, siRNA knockdown, lentiviral gene transfer, EC-specific USP40 knockout mice, transendothelial electrical resistance measurement, in vivo LPS lung injury model","journal":"Experimental & molecular medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (biochemical deubiquitination assay, EC-KO mice, lentiviral rescue, in vivo model), functional consequence established","pmids":["38307937"],"is_preprint":false},{"year":2024,"finding":"Indole-3-acetic acid (IAA) acts as an activator of USP40, reducing HSP90β ubiquitination. The protective effects of IAA against LPS-induced EC dysfunction and lung injury were abolished in USP40-deficient endothelial cells and in USP40 EC-specific knockout mice (USP40cdh5-ECKO), establishing USP40 as the required effector of IAA-mediated endothelial protection.","method":"Ubiquitination assay, transendothelial electrical resistance, siRNA knockdown, USP40 EC-specific knockout mice (USP40cdh5-ECKO), LPS lung injury model","journal":"American journal of respiratory cell and molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — EC-specific KO mice with functional lung injury readout, single lab, builds on companion paper (PMID:38307937)","pmids":["38761166"],"is_preprint":false},{"year":2024,"finding":"USP40 interacts with Claudin1 and inhibits its K48-linked polyubiquitination, thereby stabilizing Claudin1 protein in hepatocellular carcinoma cells. USP40 knockdown reduced Claudin1 levels and impaired HCC proliferation, migration, and stemness.","method":"Co-immunoprecipitation, immunofluorescence, ubiquitination assay, siRNA knockdown, overexpression in HCC cell lines and in vivo xenograft","journal":"Biology direct","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP with ubiquitination assay, single lab, multiple cell-line experiments","pmids":["38308285"],"is_preprint":false},{"year":2017,"finding":"USP40 protein is exclusively localized in the podocyte cytoplasm in adult kidney and co-localizes with intermediate filament protein nestin. Immunoprecipitation in glomerular endothelial cells confirmed direct protein–protein binding between USP40 and nestin. USP40 siRNA knockdown significantly reduced nestin protein levels. Zebrafish morphants lacking Usp40 showed disorganized glomeruli, foot process effacement, and disrupted selective glomerular permeability.","method":"Immunoprecipitation, confocal immunofluorescence, siRNA knockdown, zebrafish morpholino knockdown with permeability assay","journal":"American journal of physiology. Renal physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP with functional morphant phenotype, single lab, multiple orthogonal methods","pmids":["28148530"],"is_preprint":false},{"year":2022,"finding":"USP40 deubiquitinates HINT1, stabilizing it from degradation; HINT1 is an inducer of p53. USP40 knockdown in cultured podocytes reduced both HINT1 and p53 protein levels. USP40 was also found bound to nestin in glomeruli. In a mouse FSGS model, HINT1 upregulation preceded proteinuria and was followed sequentially by upregulation of USP40, p53, and nestin.","method":"USP40 knockout mice, siRNA knockdown in podocytes, immunoprecipitation, western blotting, mouse FSGS model with sequential protein expression analysis","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mice and cell knockdown with direct deubiquitination assay and in vivo disease model, single lab","pmids":["35605301"],"is_preprint":false},{"year":2026,"finding":"USP40 deubiquitylates integrin β1 by suppressing its monoubiquitylation (demonstrated in HEK293 cells with ubiquitin constructs). USP40 prevents clathrin-mediated endocytosis of integrin β1, maintaining its expression at the podocyte plasma membrane. USP40 knockout mice subjected to experimental FSGS showed more severe proteinuria, glomerulosclerosis, reduced podocyte number, and reduced integrin β1 expression, with increased clathrin-coated vesicles containing integrin β1 in podocyte foot processes.","method":"USP40 knockout mice in FSGS model, ubiquitin construct transfection in HEK293 cells, integrin β1 internalization assay, electron microscopy, siRNA knockdown in cultured podocytes","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO mice with disease model plus direct ubiquitination assay plus mechanistic endocytosis assay, multiple orthogonal methods, single lab","pmids":["42068752"],"is_preprint":false}],"current_model":"USP40 is a deubiquitinating enzyme that stabilizes multiple substrate proteins—including CFLARL, YAP, HSP90β, Claudin1, HINT1 (which in turn stabilizes p53), nestin, and integrin β1—by removing K48-linked (or monoubiquitin) polyubiquitin chains, thereby regulating endothelial barrier integrity (via HSP90β inactivation and suppression of RhoA/MLC/NF-κB signaling), podocyte adhesion and survival (via integrin β1 retention at the plasma membrane and p53-mediated hypertrophy through HINT1), and cancer cell proliferation/migration (via YAP and Claudin1 stabilization)."},"narrative":{"mechanistic_narrative":"USP40 is a deubiquitinating enzyme that stabilizes diverse substrate proteins by removing degradative ubiquitin marks, thereby controlling endothelial barrier integrity, podocyte survival and adhesion, and cancer cell growth [PMID:38307937, PMID:42068752, PMID:38537774]. In the vasculature, USP40 deubiquitinates and inactivates HSP90β, which limits RhoA activation, MLC and cofilin phosphorylation, and NF-κB-driven ICAM1 expression, protecting the endothelial barrier; endothelial-specific USP40 loss worsens experimental lung injury and the metabolite indole-3-acetic acid confers protection through USP40 [PMID:38307937, PMID:38761166]. In podocytes, USP40 localizes to the cytoplasm with the intermediate filament nestin and sustains glomerular function: it stabilizes HINT1 to drive p53-mediated responses and removes monoubiquitin from integrin β1 to block its clathrin-mediated endocytosis and retain it at the plasma membrane, with USP40 loss producing severe proteinuria and glomerulosclerosis [PMID:28148530, PMID:35605301, PMID:42068752]. In cancer, USP40 removes K48-linked polyubiquitin chains to stabilize substrates including CFLARL (downstream of a GMEB1 bridge), YAP (at K252/K315, in a YAP-driven feedback loop), and Claudin1, promoting proliferation, migration, and stemness [PMID:31046799, PMID:38537774, PMID:38308285].","teleology":[{"year":2017,"claim":"Established the first physiological context for USP40, showing it is a podocyte-cytoplasmic protein bound to nestin and required for normal glomerular structure and permeability.","evidence":"Immunoprecipitation, confocal immunofluorescence, siRNA knockdown, and zebrafish morpholino knockdown with permeability assay","pmids":["28148530"],"confidence":"Medium","gaps":["Did not establish whether nestin is a deubiquitination substrate","Catalytic activity not directly demonstrated in this context"]},{"year":2019,"claim":"Defined USP40 as a catalytic deubiquitinase acting within a complex, removing K48-linked chains from CFLARL with GMEB1 as a bridging adaptor.","evidence":"Reciprocal Co-IP, GST pull-down, ubiquitination assay, and siRNA knockdown rescue in NSCLC and 293FT cells","pmids":["31046799"],"confidence":"Medium","gaps":["Specific ubiquitination sites on CFLARL not mapped","In vivo relevance not tested"]},{"year":2022,"claim":"Linked USP40 to podocyte injury signaling by showing it stabilizes HINT1 to elevate p53, with sequential induction in an FSGS model.","evidence":"USP40 knockout mice, podocyte siRNA knockdown, immunoprecipitation, and mouse FSGS model with sequential expression analysis","pmids":["35605301"],"confidence":"Medium","gaps":["Ubiquitin chain type on HINT1 not specified","Causal ordering of HINT1/USP40/p53/nestin not dissected mechanistically"]},{"year":2024,"claim":"Established USP40 as an endothelial barrier protector through deubiquitination and inactivation of HSP90β, suppressing RhoA/MLC and NF-κB signaling, and showed it is the required effector of IAA-mediated protection.","evidence":"Ubiquitination assay, EC-specific USP40 knockout mice, lentiviral rescue, TEER, and in vivo LPS lung injury model across two studies","pmids":["38307937","38761166"],"confidence":"High","gaps":["How USP40 deubiquitination inactivates HSP90β mechanistically not resolved","Upstream activation of USP40 by IAA not defined at the molecular level"]},{"year":2024,"claim":"Extended USP40's pro-tumorigenic role by identifying YAP (sites K252/K315) and Claudin1 as K48-linked deubiquitination substrates, with a YAP–USP40 positive feedback loop.","evidence":"Co-IP, site-directed mutagenesis ubiquitination assays, siRNA knockdown, RNA-seq, reporter assays, and xenografts in HCC cells","pmids":["38537774","38308285"],"confidence":"Medium","gaps":["Single-lab evidence for each substrate","Whether YAP and Claudin1 stabilization are independent or coupled not established"]},{"year":2026,"claim":"Defined a membrane-trafficking mechanism: USP40 removes monoubiquitin from integrin β1 to block clathrin-mediated endocytosis and retain it at the podocyte plasma membrane, protecting against FSGS.","evidence":"USP40 knockout mice in FSGS model, ubiquitin construct transfection in HEK293, internalization assay, electron microscopy, and podocyte siRNA knockdown","pmids":["42068752"],"confidence":"High","gaps":["Ubiquitin ligase that monoubiquitylates integrin β1 not identified","Relationship between integrin β1, HINT1, and nestin pathways in podocytes not integrated"]},{"year":null,"claim":"Whether USP40's many reported substrates reflect distinct tissue-specific functions or a shared recognition mechanism, and the structural basis of its substrate selectivity, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of USP40 substrate engagement","No unifying recruitment or specificity determinant identified across substrates"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,2,4,6,7]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,1,2,7]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[5]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[7]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,1,2,4,7]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[1,4,6,7]}],"complexes":[],"partners":["CFLAR","GMEB1","YAP1","HSP90AB1","CLDN1","NES","HINT1","ITGB1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NVE5","full_name":"Ubiquitin carboxyl-terminal hydrolase 40","aliases":["Deubiquitinating enzyme 40","Ubiquitin thioesterase 40","Ubiquitin-specific-processing protease 40"],"length_aa":1235,"mass_kda":140.1,"function":"Deubiquitinating enzyme that plays a key role in maintaining endothelial cell (EC) barrier integrity and regulating apoptosis and inflammation. Stabilizes Claudin-1/CLDN1 by cleaving its polyubiquitin chains, thereby protecting tight junction structure (PubMed:38308285). Prevents EC barrier disruption by inhibiting RhoA activation and reducing phosphorylation of myosin light chain and cofilin. Suppresses EC inflammation by inhibiting NF-kappa-B activation, decreasing ICAM1 expression, and reducing leukocyte adhesion to ECs (PubMed:38307937). Mediates these protective effects in part via deubiquitination and inactivation of heat shock protein 90-beta/HSP90AB1 (PubMed:38307937). Targets CFLAR for 'Lys-48'-linked deubiquitination, stabilizing its protein levels. This interaction is facilitated by the adapter protein GMEB1, which enhances USP40-CFLAR binding. Through CFLAR stabilization, USP40 inhibits pro-caspase-8 activation and protects against apoptosis (PubMed:31046799). Additionally, USP40 stabilizes HINT1, an activator of p53/TP53, thereby maintaining p53/TP53 levels and sustaining the HINT1-p53/TP53 axis (By similarity)","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q9NVE5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/USP40","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/USP40","total_profiled":1310},"omim":[{"mim_id":"610570","title":"UBIQUITIN-SPECIFIC PROTEASE 40; USP40","url":"https://www.omim.org/entry/610570"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"},{"location":"Focal adhesion sites","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/USP40"},"hgnc":{"alias_symbol":["FLJ10785"],"prev_symbol":[]},"alphafold":{"accession":"Q9NVE5","domains":[{"cath_id":"-","chopping":"43-159_453-517","consensus_level":"medium","plddt":86.6859,"start":43,"end":517},{"cath_id":"3.90.70.10","chopping":"165-297","consensus_level":"medium","plddt":92.5384,"start":165,"end":297},{"cath_id":"-","chopping":"360-406","consensus_level":"high","plddt":87.5302,"start":360,"end":406},{"cath_id":"3.10.20.90","chopping":"529-639","consensus_level":"high","plddt":85.4417,"start":529,"end":639},{"cath_id":"3.10.20.90","chopping":"641-728","consensus_level":"high","plddt":72.2184,"start":641,"end":728},{"cath_id":"3.10.20.90","chopping":"748-838","consensus_level":"medium","plddt":82.7569,"start":748,"end":838},{"cath_id":"3.10.20.90","chopping":"841-919","consensus_level":"medium","plddt":82.9695,"start":841,"end":919},{"cath_id":"3.10.20.90","chopping":"928-944_982-1064","consensus_level":"medium","plddt":82.3349,"start":928,"end":1064},{"cath_id":"3.10.20.90","chopping":"1066-1137_1150-1196","consensus_level":"medium","plddt":84.5782,"start":1066,"end":1196}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NVE5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NVE5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NVE5-F1-predicted_aligned_error_v6.png","plddt_mean":76.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=USP40","jax_strain_url":"https://www.jax.org/strain/search?query=USP40"},"sequence":{"accession":"Q9NVE5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NVE5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NVE5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NVE5"}},"corpus_meta":[{"pmid":"16917932","id":"PMC_16917932","title":"Genetic evidence for ubiquitin-specific proteases USP24 and USP40 as candidate genes for late-onset Parkinson disease.","date":"2006","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/16917932","citation_count":53,"is_preprint":false},{"pmid":"31046799","id":"PMC_31046799","title":"Glucocorticoid modulatory element-binding protein 1 (GMEB1) interacts with the de-ubiquitinase USP40 to stabilize CFLARL and inhibit apoptosis in human non-small cell lung cancer cells.","date":"2019","source":"Journal of experimental & clinical cancer research : CR","url":"https://pubmed.ncbi.nlm.nih.gov/31046799","citation_count":27,"is_preprint":false},{"pmid":"38537774","id":"PMC_38537774","title":"USP40 promotes hepatocellular carcinoma progression through a YAP/USP40 positive feedback loop.","date":"2024","source":"Cancer letters","url":"https://pubmed.ncbi.nlm.nih.gov/38537774","citation_count":15,"is_preprint":false},{"pmid":"38761166","id":"PMC_38761166","title":"Indole-3-Acetic Acid Protects Against Lipopolysaccharide-induced Endothelial Cell Dysfunction and Lung Injury through the Activation of USP40.","date":"2024","source":"American journal of respiratory cell and molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/38761166","citation_count":15,"is_preprint":false},{"pmid":"28148530","id":"PMC_28148530","title":"USP40 gene knockdown disrupts glomerular permeability in zebrafish.","date":"2017","source":"American journal of physiology. Renal physiology","url":"https://pubmed.ncbi.nlm.nih.gov/28148530","citation_count":14,"is_preprint":false},{"pmid":"22923019","id":"PMC_22923019","title":"Association analysis of single-nucleotide polymorphisms of USP24 and USP40 with Parkinson's disease in the Han Chinese population.","date":"2012","source":"European neurology","url":"https://pubmed.ncbi.nlm.nih.gov/22923019","citation_count":12,"is_preprint":false},{"pmid":"35605301","id":"PMC_35605301","title":"USP40 deubiquitinates HINT1 and stabilizes p53 in podocyte damage.","date":"2022","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/35605301","citation_count":10,"is_preprint":false},{"pmid":"38307937","id":"PMC_38307937","title":"The deubiquitinase USP40 preserves endothelial integrity by targeting the heat shock protein HSP90β.","date":"2024","source":"Experimental & molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/38307937","citation_count":9,"is_preprint":false},{"pmid":"38308285","id":"PMC_38308285","title":"USP40 promotes hepatocellular carcinoma cell proliferation, migration and stemness by deubiquitinating and stabilizing Claudin1.","date":"2024","source":"Biology direct","url":"https://pubmed.ncbi.nlm.nih.gov/38308285","citation_count":9,"is_preprint":false},{"pmid":"31933881","id":"PMC_31933881","title":"A detrimental mutation on USP40 unlocks the tumorigenesis in a rare case of lung cancer.","date":"2019","source":"International journal of clinical and experimental pathology","url":"https://pubmed.ncbi.nlm.nih.gov/31933881","citation_count":4,"is_preprint":false},{"pmid":"42068752","id":"PMC_42068752","title":"USP40 protects podocytes by deubiquitylating integrin β1.","date":"2026","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/42068752","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.05.03.652026","title":"<i>In silico</i>  analysis and Predictive linkage of Deubiquitinating Enzymes underlying Early Development","date":"2025-05-08","source":"bioRxiv","url":"https://doi.org/10.1101/2025.05.03.652026","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8360,"output_tokens":2380,"usd":0.03039,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9518,"output_tokens":2521,"usd":0.055308,"stage2_stop_reason":"end_turn"},"total_usd":0.085698,"stage1_batch_id":"msgbatch_01UT1AahFPCAyn2uVweS7A9z","stage2_batch_id":"msgbatch_01HuKWtKNT4Pqj1bc8eEP5RV","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2019,\n      \"finding\": \"USP40 physically interacts with CFLARL (c-FLIPL) and performs K48-linked deubiquitination of CFLARL, thereby stabilizing it from proteasomal degradation. GMEB1 acts as a bridge protein that promotes the USP40–CFLARL interaction. USP40 knockdown abolished CFLARL stabilization even upon GMEB1 overexpression, placing USP40 as the catalytic effector downstream of GMEB1 in this complex.\",\n      \"method\": \"Co-immunoprecipitation, GST pull-down, immunofluorescence, ubiquitination assay, siRNA knockdown, western blotting in NSCLC and 293FT cells\",\n      \"journal\": \"Journal of experimental & clinical cancer research : CR\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP and GST pull-down with functional knockdown rescue, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"31046799\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"USP40 deubiquitinates YAP by removing K48-linked polyubiquitin chains at lysine residues K252 and K315, thereby stabilizing YAP protein in hepatocellular carcinoma cells. USP40 interacts with YAP, and its pro-tumorigenic effects on proliferation, migration, and spheroid formation are YAP-dependent. In turn, YAP transcriptionally activates USP40 expression, forming a positive feedback loop.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay (site-specific mutagenesis at K252/K315), siRNA knockdown, RNA sequencing, in vivo xenograft, reporter/transcriptional assays\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP with site-directed mutagenesis of ubiquitination sites plus in vivo validation, single lab\",\n      \"pmids\": [\"38537774\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"USP40 deubiquitinates heat shock protein HSP90β, leading to its inactivation. This prevents endothelial barrier disruption by reducing RhoA activation and phosphorylation of myosin light chain (MLC) and cofilin, and reduces NF-κB-driven inflammation and ICAM1 expression. EC-targeted USP40 knockout exacerbated experimental lung injury, while lentiviral USP40 overexpression was protective.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, siRNA knockdown, lentiviral gene transfer, EC-specific USP40 knockout mice, transendothelial electrical resistance measurement, in vivo LPS lung injury model\",\n      \"journal\": \"Experimental & molecular medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (biochemical deubiquitination assay, EC-KO mice, lentiviral rescue, in vivo model), functional consequence established\",\n      \"pmids\": [\"38307937\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Indole-3-acetic acid (IAA) acts as an activator of USP40, reducing HSP90β ubiquitination. The protective effects of IAA against LPS-induced EC dysfunction and lung injury were abolished in USP40-deficient endothelial cells and in USP40 EC-specific knockout mice (USP40cdh5-ECKO), establishing USP40 as the required effector of IAA-mediated endothelial protection.\",\n      \"method\": \"Ubiquitination assay, transendothelial electrical resistance, siRNA knockdown, USP40 EC-specific knockout mice (USP40cdh5-ECKO), LPS lung injury model\",\n      \"journal\": \"American journal of respiratory cell and molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — EC-specific KO mice with functional lung injury readout, single lab, builds on companion paper (PMID:38307937)\",\n      \"pmids\": [\"38761166\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"USP40 interacts with Claudin1 and inhibits its K48-linked polyubiquitination, thereby stabilizing Claudin1 protein in hepatocellular carcinoma cells. USP40 knockdown reduced Claudin1 levels and impaired HCC proliferation, migration, and stemness.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence, ubiquitination assay, siRNA knockdown, overexpression in HCC cell lines and in vivo xenograft\",\n      \"journal\": \"Biology direct\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP with ubiquitination assay, single lab, multiple cell-line experiments\",\n      \"pmids\": [\"38308285\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"USP40 protein is exclusively localized in the podocyte cytoplasm in adult kidney and co-localizes with intermediate filament protein nestin. Immunoprecipitation in glomerular endothelial cells confirmed direct protein–protein binding between USP40 and nestin. USP40 siRNA knockdown significantly reduced nestin protein levels. Zebrafish morphants lacking Usp40 showed disorganized glomeruli, foot process effacement, and disrupted selective glomerular permeability.\",\n      \"method\": \"Immunoprecipitation, confocal immunofluorescence, siRNA knockdown, zebrafish morpholino knockdown with permeability assay\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP with functional morphant phenotype, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"28148530\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"USP40 deubiquitinates HINT1, stabilizing it from degradation; HINT1 is an inducer of p53. USP40 knockdown in cultured podocytes reduced both HINT1 and p53 protein levels. USP40 was also found bound to nestin in glomeruli. In a mouse FSGS model, HINT1 upregulation preceded proteinuria and was followed sequentially by upregulation of USP40, p53, and nestin.\",\n      \"method\": \"USP40 knockout mice, siRNA knockdown in podocytes, immunoprecipitation, western blotting, mouse FSGS model with sequential protein expression analysis\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mice and cell knockdown with direct deubiquitination assay and in vivo disease model, single lab\",\n      \"pmids\": [\"35605301\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"USP40 deubiquitylates integrin β1 by suppressing its monoubiquitylation (demonstrated in HEK293 cells with ubiquitin constructs). USP40 prevents clathrin-mediated endocytosis of integrin β1, maintaining its expression at the podocyte plasma membrane. USP40 knockout mice subjected to experimental FSGS showed more severe proteinuria, glomerulosclerosis, reduced podocyte number, and reduced integrin β1 expression, with increased clathrin-coated vesicles containing integrin β1 in podocyte foot processes.\",\n      \"method\": \"USP40 knockout mice in FSGS model, ubiquitin construct transfection in HEK293 cells, integrin β1 internalization assay, electron microscopy, siRNA knockdown in cultured podocytes\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO mice with disease model plus direct ubiquitination assay plus mechanistic endocytosis assay, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"42068752\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"USP40 is a deubiquitinating enzyme that stabilizes multiple substrate proteins—including CFLARL, YAP, HSP90β, Claudin1, HINT1 (which in turn stabilizes p53), nestin, and integrin β1—by removing K48-linked (or monoubiquitin) polyubiquitin chains, thereby regulating endothelial barrier integrity (via HSP90β inactivation and suppression of RhoA/MLC/NF-κB signaling), podocyte adhesion and survival (via integrin β1 retention at the plasma membrane and p53-mediated hypertrophy through HINT1), and cancer cell proliferation/migration (via YAP and Claudin1 stabilization).\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"USP40 is a deubiquitinating enzyme that stabilizes diverse substrate proteins by removing degradative ubiquitin marks, thereby controlling endothelial barrier integrity, podocyte survival and adhesion, and cancer cell growth [#2, #7, #1]. In the vasculature, USP40 deubiquitinates and inactivates HSP90\\u03b2, which limits RhoA activation, MLC and cofilin phosphorylation, and NF-\\u03baB-driven ICAM1 expression, protecting the endothelial barrier; endothelial-specific USP40 loss worsens experimental lung injury and the metabolite indole-3-acetic acid confers protection through USP40 [#2, #3]. In podocytes, USP40 localizes to the cytoplasm with the intermediate filament nestin and sustains glomerular function: it stabilizes HINT1 to drive p53-mediated responses and removes monoubiquitin from integrin \\u03b21 to block its clathrin-mediated endocytosis and retain it at the plasma membrane, with USP40 loss producing severe proteinuria and glomerulosclerosis [#5, #6, #7]. In cancer, USP40 removes K48-linked polyubiquitin chains to stabilize substrates including CFLARL (downstream of a GMEB1 bridge), YAP (at K252/K315, in a YAP-driven feedback loop), and Claudin1, promoting proliferation, migration, and stemness [#0, #1, #4].\",\n  \"teleology\": [\n    {\n      \"year\": 2017,\n      \"claim\": \"Established the first physiological context for USP40, showing it is a podocyte-cytoplasmic protein bound to nestin and required for normal glomerular structure and permeability.\",\n      \"evidence\": \"Immunoprecipitation, confocal immunofluorescence, siRNA knockdown, and zebrafish morpholino knockdown with permeability assay\",\n      \"pmids\": [\"28148530\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not establish whether nestin is a deubiquitination substrate\", \"Catalytic activity not directly demonstrated in this context\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Defined USP40 as a catalytic deubiquitinase acting within a complex, removing K48-linked chains from CFLARL with GMEB1 as a bridging adaptor.\",\n      \"evidence\": \"Reciprocal Co-IP, GST pull-down, ubiquitination assay, and siRNA knockdown rescue in NSCLC and 293FT cells\",\n      \"pmids\": [\"31046799\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific ubiquitination sites on CFLARL not mapped\", \"In vivo relevance not tested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Linked USP40 to podocyte injury signaling by showing it stabilizes HINT1 to elevate p53, with sequential induction in an FSGS model.\",\n      \"evidence\": \"USP40 knockout mice, podocyte siRNA knockdown, immunoprecipitation, and mouse FSGS model with sequential expression analysis\",\n      \"pmids\": [\"35605301\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ubiquitin chain type on HINT1 not specified\", \"Causal ordering of HINT1/USP40/p53/nestin not dissected mechanistically\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Established USP40 as an endothelial barrier protector through deubiquitination and inactivation of HSP90\\u03b2, suppressing RhoA/MLC and NF-\\u03baB signaling, and showed it is the required effector of IAA-mediated protection.\",\n      \"evidence\": \"Ubiquitination assay, EC-specific USP40 knockout mice, lentiviral rescue, TEER, and in vivo LPS lung injury model across two studies\",\n      \"pmids\": [\"38307937\", \"38761166\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How USP40 deubiquitination inactivates HSP90\\u03b2 mechanistically not resolved\", \"Upstream activation of USP40 by IAA not defined at the molecular level\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended USP40's pro-tumorigenic role by identifying YAP (sites K252/K315) and Claudin1 as K48-linked deubiquitination substrates, with a YAP\\u2013USP40 positive feedback loop.\",\n      \"evidence\": \"Co-IP, site-directed mutagenesis ubiquitination assays, siRNA knockdown, RNA-seq, reporter assays, and xenografts in HCC cells\",\n      \"pmids\": [\"38537774\", \"38308285\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab evidence for each substrate\", \"Whether YAP and Claudin1 stabilization are independent or coupled not established\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Defined a membrane-trafficking mechanism: USP40 removes monoubiquitin from integrin \\u03b21 to block clathrin-mediated endocytosis and retain it at the podocyte plasma membrane, protecting against FSGS.\",\n      \"evidence\": \"USP40 knockout mice in FSGS model, ubiquitin construct transfection in HEK293, internalization assay, electron microscopy, and podocyte siRNA knockdown\",\n      \"pmids\": [\"42068752\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Ubiquitin ligase that monoubiquitylates integrin \\u03b21 not identified\", \"Relationship between integrin \\u03b21, HINT1, and nestin pathways in podocytes not integrated\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether USP40's many reported substrates reflect distinct tissue-specific functions or a shared recognition mechanism, and the structural basis of its substrate selectivity, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of USP40 substrate engagement\", \"No unifying recruitment or specificity determinant identified across substrates\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 2, 4, 6, 7]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 1, 2, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 1, 2, 4, 7]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 4, 6, 7]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CFLAR\", \"GMEB1\", \"YAP1\", \"HSP90AB1\", \"CLDN1\", \"NES\", \"HINT1\", \"ITGB1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":4,"faith_pct":100.0}}