{"gene":"VPS8","run_date":"2026-06-11T09:02:06","timeline":{"discoveries":[{"year":1996,"finding":"Yeast Vps8p is a membrane-associated hydrophilic protein of 135 kDa required for accurate sorting of vacuolar hydrolases CPY and proteinase A; in vps8 mutants the Golgi-localized CPY sorting receptor Vps10p mislocalizes to and is aberrantly proteolyzed in the vacuole, and several late-Golgi membrane proteins fail to be retained, indicating Vps8p functions in retrieval of Golgi membrane proteins from the prevacuolar compartment.","method":"Genetic characterization of vps8 mutants, subcellular fractionation, Western blotting for Vps10p localization and proteolysis","journal":"European journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (genetic, biochemical, localization) in a single focused study, single lab","pmids":["8864656"],"is_preprint":false},{"year":1998,"finding":"Genetic epistasis in yeast shows that the vps8-200 allele partially suppresses the vestigial vacuole phenotype of pep5 mutants, restoring near wild-type vacuolar hydrolase maturation and vacuolar morphology; this indicates Pep5p functions at the site of Vps8p action (Golgi-to-prevacuolar compartment transport) as well as more proximal to the vacuole.","method":"Genetic suppressor analysis (double-mutant phenotype characterization), vacuolar hydrolase maturation assays, vacuolar morphology assessment","journal":"Genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with multiple phenotypic readouts, single lab","pmids":["9475722"],"is_preprint":false},{"year":2009,"finding":"Yeast Vps8 is the effector subunit of the CORVET tethering complex: it interacts and cooperates with activated Rab5 homolog Vps21 to induce clustering of late endosomal membranes; this clustering additionally requires Vps3, Vps16, and Vps33 but not other CORVET subunits, indicating CORVET subunits have distinct activities.","method":"In vivo late endosome biogenesis monitoring assay, protein interaction studies, fluorescence microscopy of endosomal clustering","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal in vivo approaches, epistatic dissection of subunit requirements, replicated interaction with Vps21","pmids":["19828734"],"is_preprint":false},{"year":2010,"finding":"Yeast Vps8 membrane association is independent of the class C/HOPS core complex and independent of Rab GTPase Vps21; multiple membrane-binding regions exist in Vps8, with one mapped to the N-terminal part. By two-hybrid analysis, Vps8 physically interacts with Vps21, and its interaction with the HOPS core complex was confirmed by immunoprecipitation. Deletions abolishing HOPS core binding strongly impair endocytic cargo (Ste6) turnover and CPY vacuolar sorting, while deletions abolishing Vps21 binding have only modest effects.","method":"Two-hybrid analysis, immunoprecipitation, deletion mapping, endocytic cargo turnover assays (Ste6, CPY sorting)","journal":"Eukaryotic cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal interaction mapping by two-hybrid and IP, deletion analysis with functional readouts, single lab","pmids":["20173035"],"is_preprint":false},{"year":2013,"finding":"The N-terminal domains of yeast Vps3 and Vps8 (which interact with Rab5/Vps21) are required for CORVET localization to endosomes and for endocytic protein sorting; dual truncation mislocalizes CORVET to the cytosol and impairs sorting but not complex assembly. Overexpression of Vps21 or a single truncated subunit can rescue endosomal localization, indicating CORVET has additional C-terminal binding sites for endosomes beyond its N-terminal β-propeller domains.","method":"N-terminal truncation mutagenesis, subcellular fractionation, fluorescence microscopy, protein sorting assays in yeast","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic mutagenesis with multiple functional and localization readouts, single lab","pmids":["23840658"],"is_preprint":false},{"year":2016,"finding":"Drosophila Vps8 localizes to early endosomes despite absence of a clear Vps3 homolog, and forms a 4-subunit miniCORVET complex with Vps16A, Dor/Vps18, and Car/Vps33A; loss of any of these subunits causes endosome fragmentation, establishing miniCORVET as an unconventional early endosomal tether in Drosophila.","method":"Fluorescence microscopy (co-localization), co-immunoprecipitation, genetic loss-of-function (endosome morphology readout) in Drosophila hemocytes and nephrocytes","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, multiple genetic knockouts with defined endosomal phenotype, replicated across cell types","pmids":["27253064"],"is_preprint":false},{"year":2018,"finding":"Human Vps3 and Vps8 localize to Rab4-positive recycling vesicles and co-localize with the CHEVI complex on Rab11-positive recycling endosomes; depletion of Vps3 or Vps8 delays delivery of internalised integrins to recycling endosomes and their return to the plasma membrane, causing defects in integrin-dependent cell adhesion, spreading, focal adhesion formation, and cell migration.","method":"siRNA depletion, fluorescence microscopy (co-localization with Rab4/Rab11 markers), integrin trafficking assays, cell adhesion/spreading/migration assays in mammalian cells","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KD with multiple orthogonal functional readouts (trafficking assays, adhesion, migration), co-localization with endosomal markers","pmids":["29476049"],"is_preprint":false},{"year":2019,"finding":"Overexpression of Drosophila Vps8 abolishes late endosomal localization of HOPS-specific subunit Vps41/Lt and prevents HOPS assembly, thereby inhibiting HOPS-dependent trafficking routes including late endosome maturation, autophagosome-lysosome fusion, crinophagy, and lysosome-related organelle formation; this indicates Vps8 negatively regulates HOPS by outcompeting Vps41 when the Vps8:Vps41 ratio is altered.","method":"Overexpression studies, fluorescence microscopy (endosomal localization of HOPS subunits), genetic epistasis, autophagy and lysosomal biogenesis assays in Drosophila","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal in vivo assays (trafficking, autophagy, crinophagy, lysosomal biogenesis) with mechanistic dissection of subunit competition","pmids":["31194677"],"is_preprint":false},{"year":2022,"finding":"In yeast, Vps21 is required for colocalization and interaction of Vps8 with Vps34 on endosomes, and for subsequent Vps34-Atg21 interaction; loss of Vps21 disrupts localization of PI3K complex II subunits (Vps34, Vps38) from endosomes and partly disrupts PI3K complex I subunits (Vps34, Atg14) and Atg21 from the phagophore assembly site, delaying autophagy.","method":"Fluorescence colocalization microscopy, co-immunoprecipitation, autophagy flux assays in vps21Δ yeast","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and colocalization with functional autophagy readout, single lab, single study","pmids":["36076954"],"is_preprint":false}],"current_model":"VPS8 is a CORVET-specific subunit that acts as a Rab5/Vps21 effector to tether early/late endosomal membranes; in yeast it is membrane-associated, binds Vps21 and the HOPS core through distinct domains in its N-terminus, and is required for CPY sorting and endocytic cargo trafficking, while in metazoans (Drosophila and mammals) it forms a miniCORVET or CORVET complex that localizes to early and recycling endosomes to regulate integrin recycling, cell migration, and endosome maturation, with its stoichiometry relative to Vps41 critically controlling the balance between CORVET and HOPS activities."},"narrative":{"mechanistic_narrative":"VPS8 is a subunit of the CORVET membrane-tethering complex that regulates endosomal trafficking by acting as a Rab5/Vps21 effector [PMID:19828734]. In yeast, Vps8 is a membrane-associated protein required for accurate sorting of vacuolar hydrolases, functioning in retrieval of Golgi membrane proteins from the prevacuolar compartment, since its loss causes mislocalization and aberrant proteolysis of the CPY sorting receptor Vps10p [PMID:8864656]. As the effector subunit of CORVET, Vps8 binds activated Vps21 and cooperates with Vps3, Vps16, and Vps33 to drive clustering of endosomal membranes [PMID:19828734]. It engages distinct binding partners through separable regions: an N-terminal segment mediates membrane association and Vps21 binding, while a separate region mediates association with the HOPS/class C core, and loss of core binding more severely impairs endocytic cargo turnover and CPY sorting than loss of Vps21 binding [PMID:20173035, PMID:23840658]. In metazoans, Vps8 assembles into a four-subunit miniCORVET (with Vps16A, Vps18, and Vps33A) that tethers early endosomes in Drosophila [PMID:27253064], and in human cells it localizes to Rab4/Rab11 recycling compartments to drive integrin recycling, controlling cell adhesion, spreading, focal adhesion formation, and migration [PMID:29476049]. The relative abundance of Vps8 and the HOPS-specific subunit Vps41 governs the balance between the two complexes: Vps8 overexpression displaces Vps41 from late endosomes and inhibits HOPS-dependent late endosome maturation, autophagosome–lysosome fusion, and lysosome-related organelle formation [PMID:31194677]. Vps21 further coordinates Vps8 with the PI3K Vps34 machinery on endosomes to support autophagy [PMID:36076954].","teleology":[{"year":1996,"claim":"Established that Vps8 is required for fidelity of vacuolar protein sorting, framing it as a trafficking factor that retrieves Golgi membrane proteins from the prevacuolar compartment rather than a hydrolase itself.","evidence":"Genetic characterization of yeast vps8 mutants with subcellular fractionation and Western blotting for Vps10p localization and proteolysis","pmids":["8864656"],"confidence":"Medium","gaps":["No molecular complex or direct binding partners identified","Mechanism of retrieval not defined","No Rab connection established"]},{"year":1998,"claim":"Genetic epistasis placed Pep5 at the site of Vps8 action, beginning to map the functional pathway around Vps8 in Golgi-to-prevacuolar transport.","evidence":"Genetic suppressor analysis of vps8/pep5 double mutants with hydrolase maturation and vacuolar morphology readouts in yeast","pmids":["9475722"],"confidence":"Medium","gaps":["Physical interaction not tested","Did not define a discrete complex","Molecular nature of cooperation unresolved"]},{"year":2009,"claim":"Defined Vps8 as the effector subunit of the CORVET tethering complex and a Rab5/Vps21 partner, explaining how it physically links activated Rab to endosomal membrane clustering.","evidence":"In vivo late endosome biogenesis and clustering assays with protein interaction studies in yeast","pmids":["19828734"],"confidence":"High","gaps":["Domain architecture of Vps21 versus core binding not yet mapped","Structural basis of tethering unknown","Metazoan relevance untested"]},{"year":2010,"claim":"Separated the membrane-binding, Vps21-binding, and HOPS-core-binding determinants of Vps8 and showed the core interaction is functionally dominant for cargo sorting.","evidence":"Two-hybrid analysis, immunoprecipitation, and deletion mapping with Ste6 turnover and CPY sorting readouts in yeast","pmids":["20173035"],"confidence":"Medium","gaps":["Precise structural interfaces not resolved","Multiple membrane-binding regions not fully mapped","Single-lab two-hybrid evidence"]},{"year":2013,"claim":"Showed CORVET endosomal targeting depends on the N-terminal Rab-binding domains of Vps3 and Vps8 but that additional C-terminal binding sites exist, refining how the complex is recruited to membranes.","evidence":"N-terminal truncation mutagenesis with fractionation, microscopy, and sorting assays in yeast","pmids":["23840658"],"confidence":"Medium","gaps":["C-terminal endosomal binding partners not identified","Quantitative contribution of each site unresolved","Structural model lacking"]},{"year":2016,"claim":"Extended Vps8 function to metazoans by identifying a four-subunit miniCORVET that tethers early endosomes in Drosophila despite the absence of a Vps3 homolog.","evidence":"Co-localization, reciprocal co-immunoprecipitation, and genetic loss-of-function with endosome morphology readout in Drosophila hemocytes and nephrocytes","pmids":["27253064"],"confidence":"High","gaps":["Rab effector partner in flies not defined","Whether miniCORVET fully recapitulates yeast CORVET activity unclear","Tethering mechanism in vivo not reconstituted"]},{"year":2018,"claim":"Assigned a human cellular role to Vps8 in integrin recycling, linking endosomal trafficking to adhesion and migration phenotypes.","evidence":"siRNA depletion with co-localization (Rab4/Rab11), integrin trafficking, and adhesion/spreading/migration assays in mammalian cells","pmids":["29476049"],"confidence":"High","gaps":["Direct Rab effector interactions in human cells not biochemically mapped","Cargo selectivity beyond integrins untested","Complex composition (CORVET vs CHEVI) at recycling endosomes not fully resolved"]},{"year":2019,"claim":"Demonstrated that Vps8 stoichiometry relative to Vps41 acts as a switch between CORVET and HOPS activities, explaining how Vps8 levels negatively regulate HOPS-dependent maturation and autophagy.","evidence":"Overexpression, microscopy of HOPS subunit localization, genetic epistasis, and autophagy/lysosomal biogenesis assays in Drosophila","pmids":["31194677"],"confidence":"High","gaps":["Mechanism of competitive displacement at the core not structurally defined","Whether the same switch operates in mammals untested","Regulation of Vps8:Vps41 ratio in vivo unknown"]},{"year":2022,"claim":"Connected Vps8 to the PI3K Vps34 machinery via Vps21, showing Rab-dependent coordination of tethering with phosphoinositide signaling during autophagy.","evidence":"Co-localization, co-immunoprecipitation, and autophagy flux assays in vps21Δ yeast","pmids":["36076954"],"confidence":"Medium","gaps":["Direct Vps8–Vps34 interaction versus Rab-bridged not distinguished","Single-lab study","Mechanistic order of recruitment events incomplete"]},{"year":null,"claim":"How the Vps8:Vps41 ratio is set and regulated in mammalian cells, and the structural basis by which Vps8 discriminates CORVET versus HOPS core assembly, remain unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No structure of mammalian CORVET/Vps8 interfaces","Regulators of complex stoichiometry unknown","Full cargo repertoire of Vps8-dependent trafficking undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[2,3,5]}],"localization":[{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[2,5,6]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[6]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[2,5,6]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[7,8]}],"complexes":["CORVET","miniCORVET","HOPS core (class C)"],"partners":["VPS21/RAB5","VPS3","VPS16/VPS16A","VPS33/VPS33A","VPS18","VPS41","VPS34"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8N3P4","full_name":"Vacuolar protein sorting-associated protein 8 homolog","aliases":[],"length_aa":1428,"mass_kda":161.8,"function":"Plays a role in vesicle-mediated protein trafficking of the endocytic membrane transport pathway. Believed to act as a component of the putative CORVET endosomal tethering complexes which is proposed to be involved in the Rab5-to-Rab7 endosome conversion probably implicating MON1A/B, and via binding SNAREs and SNARE complexes to mediate tethering and docking events during SNARE-mediated membrane fusion. The CORVET complex is proposed to function as a Rab5 effector to mediate early endosome fusion probably in specific endosome subpopulations (PubMed:25266290). Functions predominantly in APPL1-containing endosomes (PubMed:25266290)","subcellular_location":"Early endosome","url":"https://www.uniprot.org/uniprotkb/Q8N3P4/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/VPS8","classification":"Not Classified","n_dependent_lines":143,"n_total_lines":1208,"dependency_fraction":0.1183774834437086},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000156931","cell_line_id":"CID001787","localizations":[{"compartment":"vesicles","grade":3}],"interactors":[{"gene":"VPS18","stoichiometry":10.0},{"gene":"TTK","stoichiometry":10.0},{"gene":"TGFBRAP1","stoichiometry":10.0},{"gene":"ITPRIP","stoichiometry":10.0},{"gene":"NAN","stoichiometry":0.2},{"gene":"VPS11","stoichiometry":0.2},{"gene":"PRMT1","stoichiometry":0.2},{"gene":"VPS16","stoichiometry":0.2},{"gene":"VPS33A","stoichiometry":0.2},{"gene":"HIST1H2BN;HIST1H2BM;HIST1H2BH;HIST2H2BF;HIST1H2BC;HIST1H2BD;HIST1H2BK;H2BFS","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID001787","total_profiled":1310},"omim":[{"mim_id":"618366","title":"VPS8 CORVET COMPLEX SUBUNIT; VPS8","url":"https://www.omim.org/entry/618366"},{"mim_id":"606026","title":"NEGATIVE ELONGATION FACTOR COMPLEX, MEMBER A; NELFA","url":"https://www.omim.org/entry/606026"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/VPS8"},"hgnc":{"alias_symbol":["FLJ32099"],"prev_symbol":["KIAA0804"]},"alphafold":{"accession":"Q8N3P4","domains":[{"cath_id":"2.130.10.10","chopping":"134-498","consensus_level":"medium","plddt":90.5224,"start":134,"end":498},{"cath_id":"-","chopping":"504-629","consensus_level":"high","plddt":87.0234,"start":504,"end":629},{"cath_id":"-","chopping":"1081-1103_1113-1156_1165-1203","consensus_level":"medium","plddt":76.8753,"start":1081,"end":1203}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8N3P4","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8N3P4-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8N3P4-F1-predicted_aligned_error_v6.png","plddt_mean":74.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=VPS8","jax_strain_url":"https://www.jax.org/strain/search?query=VPS8"},"sequence":{"accession":"Q8N3P4","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8N3P4.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8N3P4/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8N3P4"}},"corpus_meta":[{"pmid":"19828734","id":"PMC_19828734","title":"The CORVET subunit Vps8 cooperates with the Rab5 homolog Vps21 to induce clustering of late endosomal compartments.","date":"2009","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/19828734","citation_count":80,"is_preprint":false},{"pmid":"27253064","id":"PMC_27253064","title":"MiniCORVET is a Vps8-containing early endosomal tether in Drosophila.","date":"2016","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/27253064","citation_count":52,"is_preprint":false},{"pmid":"29476049","id":"PMC_29476049","title":"Vps3 and Vps8 control integrin trafficking from early to recycling endosomes and regulate integrin-dependent functions.","date":"2018","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/29476049","citation_count":41,"is_preprint":false},{"pmid":"8864656","id":"PMC_8864656","title":"The VPS8 gene is required for localization and trafficking of the CPY sorting receptor in Saccharomyces cerevisiae.","date":"1996","source":"European journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/8864656","citation_count":26,"is_preprint":false},{"pmid":"31194677","id":"PMC_31194677","title":"Vps8 overexpression inhibits HOPS-dependent trafficking routes by outcompeting Vps41/Lt.","date":"2019","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/31194677","citation_count":24,"is_preprint":false},{"pmid":"23840658","id":"PMC_23840658","title":"The N-terminal domains of Vps3 and Vps8 are critical for localization and function of the CORVET tethering complex on endosomes.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23840658","citation_count":19,"is_preprint":false},{"pmid":"20173035","id":"PMC_20173035","title":"Mapping of Vps21 and HOPS binding sites in Vps8 and effect of binding site mutants on endocytic trafficking.","date":"2010","source":"Eukaryotic cell","url":"https://pubmed.ncbi.nlm.nih.gov/20173035","citation_count":16,"is_preprint":false},{"pmid":"36076954","id":"PMC_36076954","title":"Vps21 Directs the PI3K-PI(3)P-Atg21-Atg16 Module to Phagophores via Vps8 for Autophagy.","date":"2022","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/36076954","citation_count":11,"is_preprint":false},{"pmid":"9475722","id":"PMC_9475722","title":"Genetic interaction with vps8-200 allows partial suppression of the vestigial vacuole phenotype caused by a pep5 mutation in Saccharomyces cerevisiae.","date":"1998","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/9475722","citation_count":11,"is_preprint":false},{"pmid":"40494419","id":"PMC_40494419","title":"ANKK1, ANKRD50, GRK5, PACSIN1 and VPS8 are novel candidate genes associated with late onset Parkinson's disease: Definition of a novel predictive protocol based on polygenic model of inheritance.","date":"2025","source":"Neurobiology of disease","url":"https://pubmed.ncbi.nlm.nih.gov/40494419","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.07.17.603885","title":"A powdery mildew core effector protein targets host endosome tethering complexes HOPS and CORVET","date":"2024-07-22","source":"bioRxiv","url":"https://doi.org/10.1101/2024.07.17.603885","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7546,"output_tokens":2590,"usd":0.030744,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9661,"output_tokens":3312,"usd":0.065552,"stage2_stop_reason":"end_turn"},"total_usd":0.096296,"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\": 1996,\n      \"finding\": \"Yeast Vps8p is a membrane-associated hydrophilic protein of 135 kDa required for accurate sorting of vacuolar hydrolases CPY and proteinase A; in vps8 mutants the Golgi-localized CPY sorting receptor Vps10p mislocalizes to and is aberrantly proteolyzed in the vacuole, and several late-Golgi membrane proteins fail to be retained, indicating Vps8p functions in retrieval of Golgi membrane proteins from the prevacuolar compartment.\",\n      \"method\": \"Genetic characterization of vps8 mutants, subcellular fractionation, Western blotting for Vps10p localization and proteolysis\",\n      \"journal\": \"European journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (genetic, biochemical, localization) in a single focused study, single lab\",\n      \"pmids\": [\"8864656\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Genetic epistasis in yeast shows that the vps8-200 allele partially suppresses the vestigial vacuole phenotype of pep5 mutants, restoring near wild-type vacuolar hydrolase maturation and vacuolar morphology; this indicates Pep5p functions at the site of Vps8p action (Golgi-to-prevacuolar compartment transport) as well as more proximal to the vacuole.\",\n      \"method\": \"Genetic suppressor analysis (double-mutant phenotype characterization), vacuolar hydrolase maturation assays, vacuolar morphology assessment\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with multiple phenotypic readouts, single lab\",\n      \"pmids\": [\"9475722\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Yeast Vps8 is the effector subunit of the CORVET tethering complex: it interacts and cooperates with activated Rab5 homolog Vps21 to induce clustering of late endosomal membranes; this clustering additionally requires Vps3, Vps16, and Vps33 but not other CORVET subunits, indicating CORVET subunits have distinct activities.\",\n      \"method\": \"In vivo late endosome biogenesis monitoring assay, protein interaction studies, fluorescence microscopy of endosomal clustering\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal in vivo approaches, epistatic dissection of subunit requirements, replicated interaction with Vps21\",\n      \"pmids\": [\"19828734\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Yeast Vps8 membrane association is independent of the class C/HOPS core complex and independent of Rab GTPase Vps21; multiple membrane-binding regions exist in Vps8, with one mapped to the N-terminal part. By two-hybrid analysis, Vps8 physically interacts with Vps21, and its interaction with the HOPS core complex was confirmed by immunoprecipitation. Deletions abolishing HOPS core binding strongly impair endocytic cargo (Ste6) turnover and CPY vacuolar sorting, while deletions abolishing Vps21 binding have only modest effects.\",\n      \"method\": \"Two-hybrid analysis, immunoprecipitation, deletion mapping, endocytic cargo turnover assays (Ste6, CPY sorting)\",\n      \"journal\": \"Eukaryotic cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal interaction mapping by two-hybrid and IP, deletion analysis with functional readouts, single lab\",\n      \"pmids\": [\"20173035\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The N-terminal domains of yeast Vps3 and Vps8 (which interact with Rab5/Vps21) are required for CORVET localization to endosomes and for endocytic protein sorting; dual truncation mislocalizes CORVET to the cytosol and impairs sorting but not complex assembly. Overexpression of Vps21 or a single truncated subunit can rescue endosomal localization, indicating CORVET has additional C-terminal binding sites for endosomes beyond its N-terminal β-propeller domains.\",\n      \"method\": \"N-terminal truncation mutagenesis, subcellular fractionation, fluorescence microscopy, protein sorting assays in yeast\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic mutagenesis with multiple functional and localization readouts, single lab\",\n      \"pmids\": [\"23840658\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Drosophila Vps8 localizes to early endosomes despite absence of a clear Vps3 homolog, and forms a 4-subunit miniCORVET complex with Vps16A, Dor/Vps18, and Car/Vps33A; loss of any of these subunits causes endosome fragmentation, establishing miniCORVET as an unconventional early endosomal tether in Drosophila.\",\n      \"method\": \"Fluorescence microscopy (co-localization), co-immunoprecipitation, genetic loss-of-function (endosome morphology readout) in Drosophila hemocytes and nephrocytes\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, multiple genetic knockouts with defined endosomal phenotype, replicated across cell types\",\n      \"pmids\": [\"27253064\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Human Vps3 and Vps8 localize to Rab4-positive recycling vesicles and co-localize with the CHEVI complex on Rab11-positive recycling endosomes; depletion of Vps3 or Vps8 delays delivery of internalised integrins to recycling endosomes and their return to the plasma membrane, causing defects in integrin-dependent cell adhesion, spreading, focal adhesion formation, and cell migration.\",\n      \"method\": \"siRNA depletion, fluorescence microscopy (co-localization with Rab4/Rab11 markers), integrin trafficking assays, cell adhesion/spreading/migration assays in mammalian cells\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KD with multiple orthogonal functional readouts (trafficking assays, adhesion, migration), co-localization with endosomal markers\",\n      \"pmids\": [\"29476049\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Overexpression of Drosophila Vps8 abolishes late endosomal localization of HOPS-specific subunit Vps41/Lt and prevents HOPS assembly, thereby inhibiting HOPS-dependent trafficking routes including late endosome maturation, autophagosome-lysosome fusion, crinophagy, and lysosome-related organelle formation; this indicates Vps8 negatively regulates HOPS by outcompeting Vps41 when the Vps8:Vps41 ratio is altered.\",\n      \"method\": \"Overexpression studies, fluorescence microscopy (endosomal localization of HOPS subunits), genetic epistasis, autophagy and lysosomal biogenesis assays in Drosophila\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal in vivo assays (trafficking, autophagy, crinophagy, lysosomal biogenesis) with mechanistic dissection of subunit competition\",\n      \"pmids\": [\"31194677\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In yeast, Vps21 is required for colocalization and interaction of Vps8 with Vps34 on endosomes, and for subsequent Vps34-Atg21 interaction; loss of Vps21 disrupts localization of PI3K complex II subunits (Vps34, Vps38) from endosomes and partly disrupts PI3K complex I subunits (Vps34, Atg14) and Atg21 from the phagophore assembly site, delaying autophagy.\",\n      \"method\": \"Fluorescence colocalization microscopy, co-immunoprecipitation, autophagy flux assays in vps21Δ yeast\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and colocalization with functional autophagy readout, single lab, single study\",\n      \"pmids\": [\"36076954\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"VPS8 is a CORVET-specific subunit that acts as a Rab5/Vps21 effector to tether early/late endosomal membranes; in yeast it is membrane-associated, binds Vps21 and the HOPS core through distinct domains in its N-terminus, and is required for CPY sorting and endocytic cargo trafficking, while in metazoans (Drosophila and mammals) it forms a miniCORVET or CORVET complex that localizes to early and recycling endosomes to regulate integrin recycling, cell migration, and endosome maturation, with its stoichiometry relative to Vps41 critically controlling the balance between CORVET and HOPS activities.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"VPS8 is a subunit of the CORVET membrane-tethering complex that regulates endosomal trafficking by acting as a Rab5/Vps21 effector [#2]. In yeast, Vps8 is a membrane-associated protein required for accurate sorting of vacuolar hydrolases, functioning in retrieval of Golgi membrane proteins from the prevacuolar compartment, since its loss causes mislocalization and aberrant proteolysis of the CPY sorting receptor Vps10p [#0]. As the effector subunit of CORVET, Vps8 binds activated Vps21 and cooperates with Vps3, Vps16, and Vps33 to drive clustering of endosomal membranes [#2]. It engages distinct binding partners through separable regions: an N-terminal segment mediates membrane association and Vps21 binding, while a separate region mediates association with the HOPS/class C core, and loss of core binding more severely impairs endocytic cargo turnover and CPY sorting than loss of Vps21 binding [#3, #4]. In metazoans, Vps8 assembles into a four-subunit miniCORVET (with Vps16A, Vps18, and Vps33A) that tethers early endosomes in Drosophila [#5], and in human cells it localizes to Rab4/Rab11 recycling compartments to drive integrin recycling, controlling cell adhesion, spreading, focal adhesion formation, and migration [#6]. The relative abundance of Vps8 and the HOPS-specific subunit Vps41 governs the balance between the two complexes: Vps8 overexpression displaces Vps41 from late endosomes and inhibits HOPS-dependent late endosome maturation, autophagosome–lysosome fusion, and lysosome-related organelle formation [#7]. Vps21 further coordinates Vps8 with the PI3K Vps34 machinery on endosomes to support autophagy [#8].\"\n  ,\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Established that Vps8 is required for fidelity of vacuolar protein sorting, framing it as a trafficking factor that retrieves Golgi membrane proteins from the prevacuolar compartment rather than a hydrolase itself.\",\n      \"evidence\": \"Genetic characterization of yeast vps8 mutants with subcellular fractionation and Western blotting for Vps10p localization and proteolysis\",\n      \"pmids\": [\"8864656\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No molecular complex or direct binding partners identified\", \"Mechanism of retrieval not defined\", \"No Rab connection established\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Genetic epistasis placed Pep5 at the site of Vps8 action, beginning to map the functional pathway around Vps8 in Golgi-to-prevacuolar transport.\",\n      \"evidence\": \"Genetic suppressor analysis of vps8/pep5 double mutants with hydrolase maturation and vacuolar morphology readouts in yeast\",\n      \"pmids\": [\"9475722\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physical interaction not tested\", \"Did not define a discrete complex\", \"Molecular nature of cooperation unresolved\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Defined Vps8 as the effector subunit of the CORVET tethering complex and a Rab5/Vps21 partner, explaining how it physically links activated Rab to endosomal membrane clustering.\",\n      \"evidence\": \"In vivo late endosome biogenesis and clustering assays with protein interaction studies in yeast\",\n      \"pmids\": [\"19828734\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Domain architecture of Vps21 versus core binding not yet mapped\", \"Structural basis of tethering unknown\", \"Metazoan relevance untested\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Separated the membrane-binding, Vps21-binding, and HOPS-core-binding determinants of Vps8 and showed the core interaction is functionally dominant for cargo sorting.\",\n      \"evidence\": \"Two-hybrid analysis, immunoprecipitation, and deletion mapping with Ste6 turnover and CPY sorting readouts in yeast\",\n      \"pmids\": [\"20173035\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Precise structural interfaces not resolved\", \"Multiple membrane-binding regions not fully mapped\", \"Single-lab two-hybrid evidence\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showed CORVET endosomal targeting depends on the N-terminal Rab-binding domains of Vps3 and Vps8 but that additional C-terminal binding sites exist, refining how the complex is recruited to membranes.\",\n      \"evidence\": \"N-terminal truncation mutagenesis with fractionation, microscopy, and sorting assays in yeast\",\n      \"pmids\": [\"23840658\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"C-terminal endosomal binding partners not identified\", \"Quantitative contribution of each site unresolved\", \"Structural model lacking\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Extended Vps8 function to metazoans by identifying a four-subunit miniCORVET that tethers early endosomes in Drosophila despite the absence of a Vps3 homolog.\",\n      \"evidence\": \"Co-localization, reciprocal co-immunoprecipitation, and genetic loss-of-function with endosome morphology readout in Drosophila hemocytes and nephrocytes\",\n      \"pmids\": [\"27253064\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Rab effector partner in flies not defined\", \"Whether miniCORVET fully recapitulates yeast CORVET activity unclear\", \"Tethering mechanism in vivo not reconstituted\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Assigned a human cellular role to Vps8 in integrin recycling, linking endosomal trafficking to adhesion and migration phenotypes.\",\n      \"evidence\": \"siRNA depletion with co-localization (Rab4/Rab11), integrin trafficking, and adhesion/spreading/migration assays in mammalian cells\",\n      \"pmids\": [\"29476049\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct Rab effector interactions in human cells not biochemically mapped\", \"Cargo selectivity beyond integrins untested\", \"Complex composition (CORVET vs CHEVI) at recycling endosomes not fully resolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstrated that Vps8 stoichiometry relative to Vps41 acts as a switch between CORVET and HOPS activities, explaining how Vps8 levels negatively regulate HOPS-dependent maturation and autophagy.\",\n      \"evidence\": \"Overexpression, microscopy of HOPS subunit localization, genetic epistasis, and autophagy/lysosomal biogenesis assays in Drosophila\",\n      \"pmids\": [\"31194677\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of competitive displacement at the core not structurally defined\", \"Whether the same switch operates in mammals untested\", \"Regulation of Vps8:Vps41 ratio in vivo unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Connected Vps8 to the PI3K Vps34 machinery via Vps21, showing Rab-dependent coordination of tethering with phosphoinositide signaling during autophagy.\",\n      \"evidence\": \"Co-localization, co-immunoprecipitation, and autophagy flux assays in vps21Δ yeast\",\n      \"pmids\": [\"36076954\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct Vps8–Vps34 interaction versus Rab-bridged not distinguished\", \"Single-lab study\", \"Mechanistic order of recruitment events incomplete\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the Vps8:Vps41 ratio is set and regulated in mammalian cells, and the structural basis by which Vps8 discriminates CORVET versus HOPS core assembly, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structure of mammalian CORVET/Vps8 interfaces\", \"Regulators of complex stoichiometry unknown\", \"Full cargo repertoire of Vps8-dependent trafficking undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [2, 3, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [2, 5, 6]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [2, 5, 6]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [7, 8]}\n    ],\n    \"complexes\": [\"CORVET\", \"miniCORVET\", \"HOPS core (class C)\"],\n    \"partners\": [\"VPS21/Rab5\", \"VPS3\", \"VPS16/VPS16A\", \"VPS33/VPS33A\", \"VPS18\", \"VPS41\", \"VPS34\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}