{"gene":"MVB12B","run_date":"2026-06-10T05:19:51","timeline":{"discoveries":[{"year":2007,"finding":"MVB12B (and MVB12A) were identified as the fourth subunit class of human ESCRT-I, associating with the core TSG101-VPS37 binary complex through conserved C-terminal sequence elements. Hydrodynamic studies showed that soluble ESCRT-I contains one copy of each of the four subunit types. Both depletion and overexpression of MVB12 subunits inhibited HIV-1 infectivity and induced aberrant virion morphologies and altered Gag protein processing.","method":"Co-immunoprecipitation, hydrodynamic/sedimentation analysis, siRNA knockdown, HIV-1 budding assay, viral morphology by EM","journal":"Cell host & microbe","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — reciprocal Co-IP, hydrodynamic reconstitution, functional HIV budding assay, replicated across multiple orthogonal methods in a single rigorous study","pmids":["18005716"],"is_preprint":false},{"year":2012,"finding":"The MVB12B MABP (MVB12-associated β-prism) domain adopts a β-prism fold with a hydrophobic membrane-anchoring loop and an electropositive phosphoinositide-binding patch, enabling binding to liposomes containing acidic lipids in a charge-density-dependent (non-stereoselective) manner. The MABP domain autonomously localizes to subcellular puncta and the plasma membrane, suggesting ESCRT-I acts as a coincidence detector for acidic phospholipids and protein ligands.","method":"1.3-Å X-ray crystal structure, in vitro liposome-binding assay, subcellular localization by fluorescence microscopy","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — atomic-resolution crystal structure combined with in vitro lipid-binding assay and live-cell localization in one study","pmids":["22232651"],"is_preprint":false},{"year":2010,"finding":"MVB12B undergoes ubiquitination at Lys264 and Lys290, leading to its instability and inclusion body formation in COS-7 cells. This ubiquitination is induced by EGF stimulation and is regulated by phosphorylation of Tyr241 and Tyr243 of MVB12B. MVB12A promotes aggregation of MVB12B, and these modifications collectively regulate ESCRT-I function.","method":"Site-directed mutagenesis, co-immunoprecipitation, EGF stimulation assay, proteasome inhibitor treatment, immunofluorescence","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis of specific residues plus Co-IP and functional readout, single lab, two orthogonal methods","pmids":["20654576"],"is_preprint":false},{"year":2013,"finding":"MVB12B does not show selective pairing with specific VPS37 partners within ESCRT-I (in contrast to UBAP1, which selectively pairs with VPS37A). siRNA-mediated depletion of MVB12A and MVB12B, unlike depletion of UBAP1, does not disrupt ubiquitin-dependent cargo sorting at the MVB, indicating functional specialization among MVB12 family members.","method":"siRNA knockdown, co-immunoprecipitation, EGF receptor sorting assay","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP and functional sorting assay, single lab; negative result for MVB12B cargo-sorting function is mechanistically informative","pmids":["24284069"],"is_preprint":false},{"year":2019,"finding":"MVB12B is phosphorylated by TBK1 (TANK-binding kinase 1) downstream of STING activation during intracellular bacterial infection, and this phosphorylation is essential for sorting bacterial DNA into extracellular vesicles (EVs). EVs carrying bacterial DNA are then delivered to bystander cells to activate cGAS-STING signaling, inhibit T-cell proliferation, and prime T cells for apoptosis.","method":"Phosphoproteomic mass spectrometry, siRNA knockdown of MVB12B, extracellular vesicle isolation and characterization, bystander cell stimulation assay, T-cell proliferation and apoptosis assays","journal":"Nature microbiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — phosphoproteomic identification of TBK1 substrate, functional siRNA rescue experiments, multiple orthogonal readouts (EV DNA sorting, bystander STING activation, T-cell effects)","pmids":["30804548"],"is_preprint":false},{"year":2018,"finding":"MVB12B knockdown inhibits unconventional secretion of CFTR (ΔF508) stimulated by ER stress, while MVB12B overexpression partially rescues cell-surface expression and Cl⁻ channel function of CFTRΔF508, placing MVB12B in the ESCRT/MVB pathway required for stress-induced unconventional CFTR trafficking.","method":"siRNA knockdown screen of ESCRT proteins, CFTRΔF508 cell-surface expression assay, Cl⁻ channel functional assay, MVB12B overexpression","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional siRNA knockdown plus overexpression with two orthogonal readouts (surface expression and channel function), single lab","pmids":["29969945"],"is_preprint":false},{"year":2025,"finding":"MVB12B overexpression suppressed proliferation and migration of bladder urothelial carcinoma (BLCA) cell lines (T24, UM-UC-3) in vitro, and protein-protein interaction network analysis confirmed MVB12B interactions with ESCRT components, consistent with a tumor-suppressive function.","method":"Overexpression in BLCA cell lines, proliferation and migration functional assays (in vitro), PPI network analysis","journal":"Translational cancer research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, functional assays in cell lines with no pathway rescue or mechanistic depth beyond overexpression phenotype","pmids":["41510117"],"is_preprint":false}],"current_model":"MVB12B is the fourth subunit of human ESCRT-I, binding the TSG101-VPS37 core through conserved C-terminal elements; its MABP domain adopts a β-prism fold that binds acidic membranes in a charge-density-dependent manner; it undergoes TBK1-mediated phosphorylation (at sites regulated by EGF-induced Tyr241/Tyr243 phosphorylation and Lys264/Lys290 ubiquitination) that is essential for sorting bacterial DNA into extracellular vesicles to enable paracrine cGAS-STING signaling; and it participates in stress-induced unconventional secretion of CFTR, while being dispensable for canonical ubiquitin-dependent MVB cargo sorting."},"narrative":{"mechanistic_narrative":"MVB12B is the fourth subunit class of human ESCRT-I, associating with the core TSG101-VPS37 binary complex through conserved C-terminal sequence elements to form a complex containing one copy of each of the four subunit types [PMID:18005716]. Its MABP domain adopts a β-prism fold with a hydrophobic membrane-anchoring loop and an electropositive patch that binds acidic phosphoinositide-containing membranes in a charge-density-dependent, non-stereoselective manner, allowing ESCRT-I to act as a coincidence detector for acidic phospholipids and protein ligands [PMID:22232651]. Functionally, MVB12B is dispensable for canonical ubiquitin-dependent cargo sorting at the MVB, distinguishing it from UBAP1 and indicating specialization within the ESCRT-I subunit family [PMID:24284069]. Instead, MVB12B is dedicated to unconventional and stress- or infection-induced trafficking routes: TBK1 phosphorylates MVB12B downstream of STING during intracellular bacterial infection, and this modification is essential for sorting bacterial DNA into extracellular vesicles that activate cGAS-STING signaling in bystander cells and suppress T-cell responses [PMID:30804548], and MVB12B is required for ER-stress-stimulated unconventional secretion of CFTRΔF508 [PMID:29969945]. Its activity is further regulated by EGF-induced Tyr241/Tyr243 phosphorylation and Lys264/Lys290 ubiquitination that drive its instability and aggregation [PMID:20654576].","teleology":[{"year":2007,"claim":"Established that MVB12B is a bona fide structural component of ESCRT-I rather than a peripheral associate, defining the four-subunit architecture of the human complex and a role in viral budding.","evidence":"Co-IP, hydrodynamic reconstitution, and HIV-1 budding/morphology assays with siRNA depletion and overexpression","pmids":["18005716"],"confidence":"High","gaps":["Did not define how MVB12B contributes mechanistically to membrane budding beyond complex incorporation","No structural basis for TSG101-VPS37 binding resolved"]},{"year":2010,"claim":"Identified post-translational control of MVB12B by EGF-driven tyrosine phosphorylation and ubiquitination, linking receptor signaling to ESCRT-I subunit stability.","evidence":"Site-directed mutagenesis, Co-IP, EGF stimulation and proteasome inhibition in COS-7 cells","pmids":["20654576"],"confidence":"Medium","gaps":["Kinase responsible for Tyr241/Tyr243 phosphorylation not identified","Functional consequence of aggregation for cargo handling not resolved"]},{"year":2012,"claim":"Resolved the structural basis for MVB12B membrane engagement, showing the MABP domain is a β-prism that reads acidic lipid charge density and supports a coincidence-detection model for ESCRT-I.","evidence":"1.3-Å X-ray crystal structure, in vitro liposome binding, and live-cell localization","pmids":["22232651"],"confidence":"High","gaps":["Specific physiological membranes engaged in cells not defined","How lipid binding is coordinated with protein-ligand recognition not directly tested"]},{"year":2013,"claim":"Demonstrated functional specialization within ESCRT-I by showing MVB12B is dispensable for ubiquitin-dependent MVB cargo sorting, unlike UBAP1.","evidence":"siRNA depletion, Co-IP, and EGF receptor sorting assay","pmids":["24284069"],"confidence":"Medium","gaps":["The cargoes or pathways that DO require MVB12B were not identified here","Whether MVB12B pairs nonselectively with all VPS37 isoforms in cells not fully resolved"]},{"year":2018,"claim":"Placed MVB12B in a non-canonical secretory route, showing it is required for ER-stress-induced unconventional secretion of misfolded CFTR.","evidence":"ESCRT siRNA knockdown screen with CFTRΔF508 surface expression and Cl⁻ channel assays plus overexpression rescue","pmids":["29969945"],"confidence":"Medium","gaps":["Direct interaction between MVB12B and CFTR not shown","Mechanism linking ESCRT-I to the unconventional secretory carrier undefined"]},{"year":2019,"claim":"Defined a signaling-coupled cargo-sorting function: TBK1 phosphorylation of MVB12B directs bacterial DNA into extracellular vesicles for paracrine innate immune signaling.","evidence":"Phosphoproteomic MS, MVB12B siRNA knockdown, EV isolation, bystander cGAS-STING activation, and T-cell proliferation/apoptosis assays","pmids":["30804548"],"confidence":"High","gaps":["TBK1 phosphosite(s) on MVB12B not mapped here","How phosphorylation redirects DNA cargo into the EV pathway mechanistically unresolved"]},{"year":2025,"claim":"Suggested a tumor-suppressive cellular phenotype for MVB12B in bladder urothelial carcinoma via overexpression effects on proliferation and migration.","evidence":"Overexpression in BLCA cell lines with proliferation/migration assays and PPI network analysis","pmids":["41510117"],"confidence":"Low","gaps":["Single-lab overexpression phenotype without rescue or in vivo validation","No mechanistic link between ESCRT-I activity and the anti-proliferative effect","Loss-of-function evidence absent"]},{"year":null,"claim":"It remains unknown which physiological cargoes MVB12B selectively routes and how its membrane-binding, phosphorylation, and ubiquitination states are integrated to switch between canonical ESCRT-I and unconventional secretory functions.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model connecting MABP lipid binding to cargo selection","Substrate code distinguishing EV-DNA sorting from CFTR secretion not defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[1]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[0,5]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[4]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[5]}],"complexes":["ESCRT-I"],"partners":["TSG101","VPS37","MVB12A","TBK1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9H7P6","full_name":"Multivesicular body subunit 12B","aliases":["ESCRT-I complex subunit MVB12B","Protein FAM125B"],"length_aa":319,"mass_kda":35.6,"function":"Component of the ESCRT-I complex, a regulator of vesicular trafficking process. Required for the sorting of endocytic ubiquitinated cargos into multivesicular bodies","subcellular_location":"Endosome; Late endosome membrane","url":"https://www.uniprot.org/uniprotkb/Q9H7P6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MVB12B","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":[{"gene":"VPS37B","stoichiometry":10.0},{"gene":"TSG101","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/MVB12B","total_profiled":1310},"omim":[{"mim_id":"621543","title":"UBIQUITIN-ASSOCIATED PROTEIN 1-LIKE PROTEIN; UBAP1L","url":"https://www.omim.org/entry/621543"},{"mim_id":"621454","title":"MULTIVESICULAR BODY SUBUNIT 12B; MVB12B","url":"https://www.omim.org/entry/621454"},{"mim_id":"621453","title":"MULTIVESICULAR BODY SUBUNIT 12A; MVB12A","url":"https://www.omim.org/entry/621453"},{"mim_id":"609787","title":"UBIQUITIN-ASSOCIATED PROTEIN 1; UBAP1","url":"https://www.omim.org/entry/609787"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Vesicles","reliability":"Supported"},{"location":"Primary cilium","reliability":"Additional"},{"location":"Primary cilium tip","reliability":"Additional"},{"location":"Primary cilium transition zone","reliability":"Additional"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"brain","ntpm":110.8}],"url":"https://www.proteinatlas.org/search/MVB12B"},"hgnc":{"alias_symbol":["FLJ00001"],"prev_symbol":["C9orf28","FAM125B"]},"alphafold":{"accession":"Q9H7P6","domains":[{"cath_id":"2.100.10.50","chopping":"51-192","consensus_level":"high","plddt":95.0068,"start":51,"end":192}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H7P6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H7P6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H7P6-F1-predicted_aligned_error_v6.png","plddt_mean":76.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MVB12B","jax_strain_url":"https://www.jax.org/strain/search?query=MVB12B"},"sequence":{"accession":"Q9H7P6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9H7P6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9H7P6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H7P6"}},"corpus_meta":[{"pmid":"30804548","id":"PMC_30804548","title":"Intracellular bacteria engage a STING-TBK1-MVB12b pathway to enable paracrine cGAS-STING signalling.","date":"2019","source":"Nature microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/30804548","citation_count":108,"is_preprint":false},{"pmid":"18005716","id":"PMC_18005716","title":"Identification of human MVB12 proteins as ESCRT-I subunits that function in HIV budding.","date":"2007","source":"Cell host & microbe","url":"https://pubmed.ncbi.nlm.nih.gov/18005716","citation_count":99,"is_preprint":false},{"pmid":"29969945","id":"PMC_29969945","title":"Specific autophagy and ESCRT components participate in the unconventional secretion of CFTR.","date":"2018","source":"Autophagy","url":"https://pubmed.ncbi.nlm.nih.gov/29969945","citation_count":55,"is_preprint":false},{"pmid":"22232651","id":"PMC_22232651","title":"Structural basis for membrane targeting by the MVB12-associated β-prism domain of the human ESCRT-I MVB12 subunit.","date":"2012","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/22232651","citation_count":43,"is_preprint":false},{"pmid":"24518671","id":"PMC_24518671","title":"A genome-wide association study of intra-ocular pressure suggests a novel association in the gene FAM125B in the TwinsUK cohort.","date":"2014","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/24518671","citation_count":37,"is_preprint":false},{"pmid":"27363808","id":"PMC_27363808","title":"Indexing Effects of Copy Number Variation on Genes Involved in Developmental Delay.","date":"2016","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/27363808","citation_count":31,"is_preprint":false},{"pmid":"24284069","id":"PMC_24284069","title":"The molecular basis for selective assembly of the UBAP1-containing endosome-specific ESCRT-I complex.","date":"2013","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/24284069","citation_count":30,"is_preprint":false},{"pmid":"20654576","id":"PMC_20654576","title":"Distinct functions of human MVB12A and MVB12B in the ESCRT-I dependent on their posttranslational modifications.","date":"2010","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/20654576","citation_count":26,"is_preprint":false},{"pmid":"33504897","id":"PMC_33504897","title":"Transcriptome-wide Mendelian randomization study prioritising novel tissue-dependent genes for glioma susceptibility.","date":"2021","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/33504897","citation_count":13,"is_preprint":false},{"pmid":"24899618","id":"PMC_24899618","title":"Protective effect of ischaemic preconditioning in total knee arthroplasty.","date":"2014","source":"European review for medical and pharmacological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/24899618","citation_count":9,"is_preprint":false},{"pmid":"38339094","id":"PMC_38339094","title":"Genetic Factors Associated with the Development of Neuropathy in Type 2 Diabetes.","date":"2024","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/38339094","citation_count":5,"is_preprint":false},{"pmid":"33163277","id":"PMC_33163277","title":"Novel genetic variants of PIP5K1C and MVB12B of the endosome-related pathway predict cutaneous melanoma-specific survival.","date":"2020","source":"American journal of cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/33163277","citation_count":4,"is_preprint":false},{"pmid":"38255187","id":"PMC_38255187","title":"Cell-Free Genic Extrachromosomal Circular DNA Profiles of DNase Knockouts Associated with Systemic Lupus Erythematosus and Relation with Common Fragile Sites.","date":"2023","source":"Biomedicines","url":"https://pubmed.ncbi.nlm.nih.gov/38255187","citation_count":4,"is_preprint":false},{"pmid":"41510117","id":"PMC_41510117","title":"Multivesicular body subunit 12B (MVB12B) overexpression represses proliferation and migration in bladder urothelial carcinoma.","date":"2025","source":"Translational cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/41510117","citation_count":0,"is_preprint":false},{"pmid":"39967738","id":"PMC_39967738","title":"Transcriptome analysis of 3D4/21 cells expressing CSFV NS4B.","date":"2025","source":"Frontiers in microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/39967738","citation_count":0,"is_preprint":false},{"pmid":"41404738","id":"PMC_41404738","title":"Identification of Biomarkers for Right Ventricular Dysfunction in Idiopathic Dilated Cardiomyopathy Via Urinary Proteomics and Machine Learning.","date":"2025","source":"Journal of the American Heart Association","url":"https://pubmed.ncbi.nlm.nih.gov/41404738","citation_count":0,"is_preprint":false},{"pmid":"40493586","id":"PMC_40493586","title":"Leveraging molecular-QTL co-association to predict novel disease-associated genetic loci using a graph convolutional neural network.","date":"2025","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/40493586","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11497,"output_tokens":2005,"usd":0.032283,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8965,"output_tokens":2682,"usd":0.055938,"stage2_stop_reason":"end_turn"},"total_usd":0.088221,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"MVB12B (and MVB12A) were identified as the fourth subunit class of human ESCRT-I, associating with the core TSG101-VPS37 binary complex through conserved C-terminal sequence elements. Hydrodynamic studies showed that soluble ESCRT-I contains one copy of each of the four subunit types. Both depletion and overexpression of MVB12 subunits inhibited HIV-1 infectivity and induced aberrant virion morphologies and altered Gag protein processing.\",\n      \"method\": \"Co-immunoprecipitation, hydrodynamic/sedimentation analysis, siRNA knockdown, HIV-1 budding assay, viral morphology by EM\",\n      \"journal\": \"Cell host & microbe\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — reciprocal Co-IP, hydrodynamic reconstitution, functional HIV budding assay, replicated across multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"18005716\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The MVB12B MABP (MVB12-associated β-prism) domain adopts a β-prism fold with a hydrophobic membrane-anchoring loop and an electropositive phosphoinositide-binding patch, enabling binding to liposomes containing acidic lipids in a charge-density-dependent (non-stereoselective) manner. The MABP domain autonomously localizes to subcellular puncta and the plasma membrane, suggesting ESCRT-I acts as a coincidence detector for acidic phospholipids and protein ligands.\",\n      \"method\": \"1.3-Å X-ray crystal structure, in vitro liposome-binding assay, subcellular localization by fluorescence microscopy\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — atomic-resolution crystal structure combined with in vitro lipid-binding assay and live-cell localization in one study\",\n      \"pmids\": [\"22232651\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"MVB12B undergoes ubiquitination at Lys264 and Lys290, leading to its instability and inclusion body formation in COS-7 cells. This ubiquitination is induced by EGF stimulation and is regulated by phosphorylation of Tyr241 and Tyr243 of MVB12B. MVB12A promotes aggregation of MVB12B, and these modifications collectively regulate ESCRT-I function.\",\n      \"method\": \"Site-directed mutagenesis, co-immunoprecipitation, EGF stimulation assay, proteasome inhibitor treatment, immunofluorescence\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis of specific residues plus Co-IP and functional readout, single lab, two orthogonal methods\",\n      \"pmids\": [\"20654576\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"MVB12B does not show selective pairing with specific VPS37 partners within ESCRT-I (in contrast to UBAP1, which selectively pairs with VPS37A). siRNA-mediated depletion of MVB12A and MVB12B, unlike depletion of UBAP1, does not disrupt ubiquitin-dependent cargo sorting at the MVB, indicating functional specialization among MVB12 family members.\",\n      \"method\": \"siRNA knockdown, co-immunoprecipitation, EGF receptor sorting assay\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP and functional sorting assay, single lab; negative result for MVB12B cargo-sorting function is mechanistically informative\",\n      \"pmids\": [\"24284069\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"MVB12B is phosphorylated by TBK1 (TANK-binding kinase 1) downstream of STING activation during intracellular bacterial infection, and this phosphorylation is essential for sorting bacterial DNA into extracellular vesicles (EVs). EVs carrying bacterial DNA are then delivered to bystander cells to activate cGAS-STING signaling, inhibit T-cell proliferation, and prime T cells for apoptosis.\",\n      \"method\": \"Phosphoproteomic mass spectrometry, siRNA knockdown of MVB12B, extracellular vesicle isolation and characterization, bystander cell stimulation assay, T-cell proliferation and apoptosis assays\",\n      \"journal\": \"Nature microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — phosphoproteomic identification of TBK1 substrate, functional siRNA rescue experiments, multiple orthogonal readouts (EV DNA sorting, bystander STING activation, T-cell effects)\",\n      \"pmids\": [\"30804548\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MVB12B knockdown inhibits unconventional secretion of CFTR (ΔF508) stimulated by ER stress, while MVB12B overexpression partially rescues cell-surface expression and Cl⁻ channel function of CFTRΔF508, placing MVB12B in the ESCRT/MVB pathway required for stress-induced unconventional CFTR trafficking.\",\n      \"method\": \"siRNA knockdown screen of ESCRT proteins, CFTRΔF508 cell-surface expression assay, Cl⁻ channel functional assay, MVB12B overexpression\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional siRNA knockdown plus overexpression with two orthogonal readouts (surface expression and channel function), single lab\",\n      \"pmids\": [\"29969945\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MVB12B overexpression suppressed proliferation and migration of bladder urothelial carcinoma (BLCA) cell lines (T24, UM-UC-3) in vitro, and protein-protein interaction network analysis confirmed MVB12B interactions with ESCRT components, consistent with a tumor-suppressive function.\",\n      \"method\": \"Overexpression in BLCA cell lines, proliferation and migration functional assays (in vitro), PPI network analysis\",\n      \"journal\": \"Translational cancer research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, functional assays in cell lines with no pathway rescue or mechanistic depth beyond overexpression phenotype\",\n      \"pmids\": [\"41510117\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MVB12B is the fourth subunit of human ESCRT-I, binding the TSG101-VPS37 core through conserved C-terminal elements; its MABP domain adopts a β-prism fold that binds acidic membranes in a charge-density-dependent manner; it undergoes TBK1-mediated phosphorylation (at sites regulated by EGF-induced Tyr241/Tyr243 phosphorylation and Lys264/Lys290 ubiquitination) that is essential for sorting bacterial DNA into extracellular vesicles to enable paracrine cGAS-STING signaling; and it participates in stress-induced unconventional secretion of CFTR, while being dispensable for canonical ubiquitin-dependent MVB cargo sorting.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MVB12B is the fourth subunit class of human ESCRT-I, associating with the core TSG101-VPS37 binary complex through conserved C-terminal sequence elements to form a complex containing one copy of each of the four subunit types [#0]. Its MABP domain adopts a β-prism fold with a hydrophobic membrane-anchoring loop and an electropositive patch that binds acidic phosphoinositide-containing membranes in a charge-density-dependent, non-stereoselective manner, allowing ESCRT-I to act as a coincidence detector for acidic phospholipids and protein ligands [#1]. Functionally, MVB12B is dispensable for canonical ubiquitin-dependent cargo sorting at the MVB, distinguishing it from UBAP1 and indicating specialization within the ESCRT-I subunit family [#3]. Instead, MVB12B is dedicated to unconventional and stress- or infection-induced trafficking routes: TBK1 phosphorylates MVB12B downstream of STING during intracellular bacterial infection, and this modification is essential for sorting bacterial DNA into extracellular vesicles that activate cGAS-STING signaling in bystander cells and suppress T-cell responses [#4], and MVB12B is required for ER-stress-stimulated unconventional secretion of CFTRΔF508 [#5]. Its activity is further regulated by EGF-induced Tyr241/Tyr243 phosphorylation and Lys264/Lys290 ubiquitination that drive its instability and aggregation [#2].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Established that MVB12B is a bona fide structural component of ESCRT-I rather than a peripheral associate, defining the four-subunit architecture of the human complex and a role in viral budding.\",\n      \"evidence\": \"Co-IP, hydrodynamic reconstitution, and HIV-1 budding/morphology assays with siRNA depletion and overexpression\",\n      \"pmids\": [\"18005716\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define how MVB12B contributes mechanistically to membrane budding beyond complex incorporation\", \"No structural basis for TSG101-VPS37 binding resolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identified post-translational control of MVB12B by EGF-driven tyrosine phosphorylation and ubiquitination, linking receptor signaling to ESCRT-I subunit stability.\",\n      \"evidence\": \"Site-directed mutagenesis, Co-IP, EGF stimulation and proteasome inhibition in COS-7 cells\",\n      \"pmids\": [\"20654576\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Kinase responsible for Tyr241/Tyr243 phosphorylation not identified\", \"Functional consequence of aggregation for cargo handling not resolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Resolved the structural basis for MVB12B membrane engagement, showing the MABP domain is a β-prism that reads acidic lipid charge density and supports a coincidence-detection model for ESCRT-I.\",\n      \"evidence\": \"1.3-Å X-ray crystal structure, in vitro liposome binding, and live-cell localization\",\n      \"pmids\": [\"22232651\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific physiological membranes engaged in cells not defined\", \"How lipid binding is coordinated with protein-ligand recognition not directly tested\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Demonstrated functional specialization within ESCRT-I by showing MVB12B is dispensable for ubiquitin-dependent MVB cargo sorting, unlike UBAP1.\",\n      \"evidence\": \"siRNA depletion, Co-IP, and EGF receptor sorting assay\",\n      \"pmids\": [\"24284069\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The cargoes or pathways that DO require MVB12B were not identified here\", \"Whether MVB12B pairs nonselectively with all VPS37 isoforms in cells not fully resolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Placed MVB12B in a non-canonical secretory route, showing it is required for ER-stress-induced unconventional secretion of misfolded CFTR.\",\n      \"evidence\": \"ESCRT siRNA knockdown screen with CFTRΔF508 surface expression and Cl⁻ channel assays plus overexpression rescue\",\n      \"pmids\": [\"29969945\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct interaction between MVB12B and CFTR not shown\", \"Mechanism linking ESCRT-I to the unconventional secretory carrier undefined\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Defined a signaling-coupled cargo-sorting function: TBK1 phosphorylation of MVB12B directs bacterial DNA into extracellular vesicles for paracrine innate immune signaling.\",\n      \"evidence\": \"Phosphoproteomic MS, MVB12B siRNA knockdown, EV isolation, bystander cGAS-STING activation, and T-cell proliferation/apoptosis assays\",\n      \"pmids\": [\"30804548\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"TBK1 phosphosite(s) on MVB12B not mapped here\", \"How phosphorylation redirects DNA cargo into the EV pathway mechanistically unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Suggested a tumor-suppressive cellular phenotype for MVB12B in bladder urothelial carcinoma via overexpression effects on proliferation and migration.\",\n      \"evidence\": \"Overexpression in BLCA cell lines with proliferation/migration assays and PPI network analysis\",\n      \"pmids\": [\"41510117\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single-lab overexpression phenotype without rescue or in vivo validation\", \"No mechanistic link between ESCRT-I activity and the anti-proliferative effect\", \"Loss-of-function evidence absent\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unknown which physiological cargoes MVB12B selectively routes and how its membrane-binding, phosphorylation, and ubiquitination states are integrated to switch between canonical ESCRT-I and unconventional secretory functions.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model connecting MABP lipid binding to cargo selection\", \"Substrate code distinguishing EV-DNA sorting from CFTR secretion not defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"complexes\": [\"ESCRT-I\"],\n    \"partners\": [\"TSG101\", \"VPS37\", \"MVB12A\", \"TBK1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}