{"gene":"VIPAS39","run_date":"2026-06-11T09:02:06","timeline":{"discoveries":[{"year":2010,"finding":"VIPAR (VIPAS39) forms a functional complex with VPS33B that interacts with RAB11A. Knockdown of vipar in zebrafish caused biliary excretion and E-cadherin defects. In Vipar- and Vps33b-deficient mouse mIMDC-3 cells, membrane proteins were expressed abnormally, tight junctions were structurally and functionally defective, Ceacam5 was mis-sorted toward lysosomal degradation, and E-cadherin was transcriptionally downregulated, establishing that the VPS33B-VIPAR complex regulates apical-basolateral polarity in liver and kidney.","method":"Co-immunoprecipitation (VPS33B-VIPAR-RAB11A complex), zebrafish vipar knockdown with biliary/E-cadherin readouts, Vipar/Vps33b-deficient mouse cell lines with tight junction functional assays, immunofluorescence, and protein sorting assays","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, multiple model systems (zebrafish, mouse cells), multiple orthogonal functional readouts, replicated across labs","pmids":["20190753"],"is_preprint":false},{"year":2008,"finding":"The human SPE-39 orthologue (C14orf133/VIPAS39) interacts with VPS33 homologues and co-immunoprecipitates and co-sediments with other HOPS complex subunits. SPE-39 knockdown in human cells altered morphology of syntaxin 7-, syntaxin 8-, and syntaxin 13-positive endosomes and delayed mannose 6-phosphate receptor-mediated cathepsin D delivery and EGF receptor degradation, establishing VIPAS39 as a regulator of lysosomal delivery via the HOPS complex. C. elegans SPE-39 interacts in vitro with both VPS33A and VPS33B, and RNAi of VPS33B phenocopies spe-39 spermatogenesis defects.","method":"Co-immunoprecipitation, co-sedimentation, in vitro binding assay, siRNA knockdown with fluorescence microscopy and trafficking assays (cathepsin D delivery, EGFR degradation), C. elegans genetic epistasis (RNAi)","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (Co-IP, co-sedimentation, in vitro binding, functional trafficking assays, genetic epistasis) in two organisms","pmids":["19109425"],"is_preprint":false},{"year":2012,"finding":"VPS16B (VIPAS39) was identified as a VPS33B-binding protein by yeast two-hybrid and mass spectrometry, confirmed by co-immunoprecipitation. In platelets from an ARC patient with C14orf133/VPS16B mutations, α-granules were completely absent while δ-granules were present. GFP-VPS16B in Dami megakaryocytic cells co-localized with markers of the trans-Golgi network, late endosomes, and α-granules, establishing that VPS16B is essential for platelet α-granule biogenesis.","method":"Yeast two-hybrid, mass spectrometry, co-immunoprecipitation, electron microscopy of patient platelets, immunofluorescence microscopy of GFP-VPS16B in Dami cells","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — yeast two-hybrid, MS, Co-IP, patient cell EM, and localization studies with multiple orthogonal methods","pmids":["23002115"],"is_preprint":false},{"year":2013,"finding":"Disease-causing mutations in VIPAS39/SPE-39 and VPS33B were investigated by yeast two-hybrid, immunoprecipitation, and quantitative fluorescent microscopy. Although few mutations prevent VIPAS39-VPS33B interaction, some mutants fragment VIPAS39-positive endosomes, and all mutants alter the subcellular localization of VPS33B to VIPAS39-positive endosomes, suggesting ARC syndrome results from impaired VIPAS39/SPE-39 and VPS33B-dependent endosomal maturation or fusion.","method":"Yeast two-hybrid, co-immunoprecipitation, quantitative fluorescent microscopy of mutant proteins in cells","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple methods in single lab, clear functional readout of endosomal fragmentation and mislocalization","pmids":["23918659"],"is_preprint":false},{"year":2019,"finding":"VPS33B and VPS16B (VIPAS39) form a small, distinct complex in megakaryocytes with the same hydrodynamic radius as the recombinant VPS33B-VPS16B heterodimer purified from bacteria. The complex localizes to recycling endosomes. VPS33B deficiency (CRISPR/Cas9 KO) causes α-granule cargo (platelet factor 4, von Willebrand factor, P-selectin) degradation in lysosomes rather than correct trafficking, and VPS16B steady-state levels are significantly lower in VPS33B-KO cells, indicating VPS16B is destabilized without VPS33B.","method":"CRISPR/Cas9 knockout in imMKCL megakaryocytes, size-exclusion chromatography, recombinant protein purification, immunofluorescence co-localization, immunoblotting for cargo proteins","journal":"Blood advances","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — CRISPR KO with defined cargo trafficking phenotype, recombinant complex purification, and SEC analysis in one rigorous study","pmids":["31501156"],"is_preprint":false},{"year":2023,"finding":"Human VPS33B-VPS16B forms a high molecular weight complex (~315 kDa) with a VPS33B:VPS16B stoichiometry of 2:3. Structural analysis by CD, SAXS, and negative-staining EM revealed a well-folded α-helical, two-lobed shape, with each lobe containing one VPS33B molecule oriented in opposite directions. Truncated VPS16B (amino acids 143–316) is sufficient for complex formation with VPS33B. ARC-causing VPS33B missense variant L30P disrupts complex formation, whereas S243F and H344D do not. The bidirectional orientation of VPS33B molecules suggests the complex can interact with separate SNARE bundles/SNAREpins.","method":"Size-exclusion chromatography-multiangle light scattering (SEC-MALS), circular dichroism, small-angle X-ray scattering (SAXS), negative-staining EM, quantitative immunoblotting, avidin tagging, truncation/mutagenesis analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple structural methods (SAXS, EM, CD, SEC-MALS) combined with mutagenesis and stoichiometric analysis in one rigorous study","pmids":["37062417"],"is_preprint":false},{"year":2012,"finding":"Tyrosine phosphorylation of SPE-39 (VIPAS39) following EGF stimulation promotes its ubiquitination at the C-terminal region, reducing SPE-39 stability. Ubiquitination is regulated by phosphorylation of Tyr-11. Association of VPS33B with SPE-39 inhibits EGF-stimulated ubiquitination of SPE-39, stabilizing it. SPE-39 and VPS33B have an opposing functional relationship in downregulation of the EGF receptor in EGF-stimulated COS-7 cells.","method":"Ubiquitination and phosphorylation assays (immunoprecipitation/immunoblotting), site-directed mutagenesis (Tyr-11), co-immunoprecipitation, EGF receptor downregulation assay in COS-7 cells","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — site-directed mutagenesis combined with Co-IP and functional EGFR downregulation assay, single lab","pmids":["22677173"],"is_preprint":false},{"year":2018,"finding":"VPS33B and VIPAR (VIPAS39) are essential for epidermal lamellar body biogenesis and function. Mouse knockouts of Vps33b or Vipas39 develop ichthyosis with abnormal lamellar body morphology, disrupted localization of lamellar body cargo, increased corneocyte thickness, decreased cornified envelope thickness, and reduced lipid deposition in stratum corneum, establishing a role for the VPS33B-VIPAR complex in lysosome-related organelle biogenesis in skin.","method":"Mouse knockout (Vps33b and Vipas39), histology, immunofluorescence, electron microscopy of skin biopsies and primary cells","journal":"Biochimica et biophysica acta. Molecular basis of disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two knockout mouse models with orthogonal microscopy methods, single lab","pmids":["29409756"],"is_preprint":false},{"year":2022,"finding":"Stable expression of VPS16B (VIPAS39) in platelets, megakaryocytes, and other primary cells is dependent on VPS33B expression. A novel homozygous nonsense VPS33B variant in ARC syndrome patients caused loss of expression of both VPS33B and VPS16B in platelets, indicating VPS16B protein stability requires its partner VPS33B.","method":"Patient platelet protein expression analysis by immunoblotting, electron microscopy, confirmatory genetic testing","journal":"Journal of thrombosis and haemostasis : JTH","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — primary patient cell analysis with immunoblotting and EM, single case/lab, confirms findings from CRISPR KO study (PMID:31501156)","pmids":["35325493"],"is_preprint":false},{"year":2025,"finding":"VIPAS39 was identified by IP-MS as a pivotal regulator that sorts ACSL4 into late endosomes, facilitating its release as exosomes. In ferroptosis-resistant ovarian cancer cells, VIPAS39 mediates exosomal export of ACSL4, reducing intracellular ACSL4 protein levels and conferring resistance to ferroptosis. Targeting VIPAS39 overcomes ferroptosis resistance and suppresses tumor growth in CDX and PDX models.","method":"Immunoprecipitation-mass spectrometry (IP-MS), live-cell imaging with pH-sensitive CD63-pHuji reporter, protein binding assays, cell viability and lipid peroxidation assays, CDX and PDX xenograft models","journal":"EBioMedicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — IP-MS identification validated with live-cell reporter assay and in vivo xenograft, multiple orthogonal methods in single lab","pmids":["40088627"],"is_preprint":false},{"year":2003,"finding":"C. elegans SPE-39 (ortholog of VIPAS39) encodes a novel hydrophilic protein required for intracellular membrane reorganization during spermatogenesis. In spe-39 mutants, membranous organelles (MOs) are absent and fibrous bodies are disorganized, replaced by small vesicles with internal membranes. SPE-39 protein is distributed throughout the cytoplasm and not specifically associated with FB-MOs. The gene has orthologs in Drosophila and humans but no yeast homolog, suggesting a metazoan-specific membrane biogenesis function.","method":"Genetic analysis (spe-39 mutants), electron microscopy of spermatocytes, immunofluorescence with SPE-39-specific antiserum, gene identification/sequencing","journal":"Genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function with EM ultrastructural phenotype and immunofluorescence localization in C. elegans ortholog, single lab","pmids":["14504223"],"is_preprint":false}],"current_model":"VIPAS39 (VPS16B/VIPAR/SPE-39) forms a stoichiometric, bidirectional heteromeric complex with VPS33B (2 VPS33B : 3 VPS16B, ~315 kDa) that functions as a metazoan-specific component of the HOPS-related endosomal trafficking machinery, facilitating vesicular fusion via SNARE interactions; the complex localizes to RAB11A-positive recycling endosomes, late endosomes, and trans-Golgi network, where it directs cargo sorting for lysosome-related organelle biogenesis (platelet α-granules, epidermal lamellar bodies), maintains apical-basolateral epithelial polarity, and regulates EGFR downregulation—with VPS33B required for VPS16B protein stability, and VIPAS39 additionally mediating exosomal export of ACSL4 to modulate ferroptosis sensitivity."},"narrative":{"mechanistic_narrative":"VIPAS39 (VPS16B/VIPAR/SPE-39) is a metazoan-specific endosomal trafficking factor that operates as an obligate stoichiometric partner of VPS33B, together forming a HOPS-related complex that directs vesicular fusion and cargo sorting for the biogenesis of lysosome-related organelles [PMID:19109425, PMID:23002115]. The two proteins assemble into a defined ~315 kDa heteromer with a 2:3 VPS33B:VPS16B stoichiometry adopting a two-lobed, bidirectional architecture in which each lobe contains an oppositely oriented VPS33B, an arrangement compatible with engaging separate SNARE bundles during membrane fusion [PMID:37062417]. The complex acts at recycling endosomes, late endosomes, and the trans-Golgi network, where it controls lysosomal cargo delivery, EGF receptor degradation, and apical-basolateral epithelial polarity—loss of VIPAS39 fragments endosomes, mis-sorts membrane cargo toward lysosomal degradation, and disrupts tight junctions in liver and kidney models [PMID:20190753, PMID:19109425, PMID:23918659]. Through this sorting activity VIPAS39 and VPS33B are required for platelet α-granule and epidermal lamellar body biogenesis, and mutations in VIPAS39/VPS33B cause ARC (arthrogryposis–renal dysfunction–cholestasis) syndrome [PMID:23002115, PMID:29409756, PMID:23918659]. VPS16B protein stability is strictly dependent on VPS33B, with VPS33B loss destabilizing VIPAS39 in megakaryocytes and patient cells [PMID:31501156, PMID:35325493]. Beyond its core trafficking role, VIPAS39 sorts ACSL4 into late endosomes for exosomal export, lowering intracellular ACSL4 and conferring ferroptosis resistance in ovarian cancer [PMID:40088627].","teleology":[{"year":2003,"claim":"Established that the VIPAS39 ortholog encodes a novel, metazoan-specific cytoplasmic protein required for intracellular membrane reorganization, defining a membrane-biogenesis function distinct from yeast trafficking machinery.","evidence":"Genetic loss-of-function and EM ultrastructure of spe-39 mutant C. elegans spermatocytes with immunofluorescence localization","pmids":["14504223"],"confidence":"Medium","gaps":["No molecular partners identified at this stage","Biochemical activity undefined","Mammalian relevance not yet established"]},{"year":2008,"claim":"Connected VIPAS39 to the HOPS machinery and lysosomal delivery by showing it binds VPS33 homologues and that its loss perturbs endosomal trafficking, identifying the molecular system in which it acts.","evidence":"Co-IP, co-sedimentation, in vitro binding, siRNA knockdown with cathepsin D and EGFR trafficking assays in human cells, plus C. elegans RNAi epistasis","pmids":["19109425"],"confidence":"High","gaps":["Stoichiometry and complex architecture unknown","Whether VIPAS39 acts with VPS33A or VPS33B in vivo unresolved"]},{"year":2010,"claim":"Defined the VPS33B-VIPAS39 complex as a regulator of epithelial apical-basolateral polarity via RAB11A-associated trafficking, linking trafficking defects to organ-level (liver/kidney) phenotypes.","evidence":"Reciprocal Co-IP for VPS33B-VIPAR-RAB11A, zebrafish knockdown, Vipar/Vps33b-deficient mouse cells with tight junction and cargo-sorting readouts","pmids":["20190753"],"confidence":"High","gaps":["Direct mechanism of cargo selection not resolved","How polarity defects arise from endosomal fusion failure not defined at molecular level"]},{"year":2012,"claim":"Showed the complex is essential for platelet α-granule biogenesis, establishing VIPAS39's role in lysosome-related organelle formation and its disease relevance to ARC syndrome.","evidence":"Yeast two-hybrid, MS, Co-IP, EM of ARC patient platelets, GFP-VPS16B localization in Dami megakaryocytes","pmids":["23002115"],"confidence":"High","gaps":["Cargo routing mechanism into nascent α-granules not detailed","δ-granule independence not mechanistically explained"]},{"year":2012,"claim":"Revealed post-translational regulation of VIPAS39 by EGF-induced Tyr-11 phosphorylation and C-terminal ubiquitination, with VPS33B binding stabilizing it, indicating opposing roles in EGFR downregulation.","evidence":"Phosphorylation/ubiquitination assays, Tyr-11 site-directed mutagenesis, Co-IP, EGFR downregulation in COS-7 cells","pmids":["22677173"],"confidence":"Medium","gaps":["Kinase and E3 ligase not identified","Single-lab, single cell system","Physiological significance of opposing VPS33B/VIPAS39 EGFR roles unclear"]},{"year":2013,"claim":"Clarified how ARC mutations cause disease, showing most mutants preserve the VIPAS39-VPS33B interaction but mislocalize VPS33B and fragment endosomes, pointing to impaired endosomal maturation/fusion rather than complex disruption.","evidence":"Yeast two-hybrid, Co-IP, quantitative fluorescent microscopy of mutant proteins","pmids":["23918659"],"confidence":"Medium","gaps":["Mechanism linking endosome fragmentation to cargo failure unresolved","Single-lab study"]},{"year":2019,"claim":"Demonstrated VPS33B-VIPAS39 forms a discrete heterodimer at recycling endosomes and that VIPAS39 depends on VPS33B for stability, defining the functional unit and showing cargo is degraded in lysosomes when the complex is lost.","evidence":"CRISPR/Cas9 KO in imMKCL megakaryocytes, SEC, recombinant complex purification, cargo immunoblotting and co-localization","pmids":["31501156"],"confidence":"High","gaps":["Higher-order stoichiometry not yet resolved","SNARE engagement not demonstrated directly"]},{"year":2022,"claim":"Confirmed in patient cells that VIPAS39 protein stability requires VPS33B, reinforcing the interdependence of the complex subunits.","evidence":"Immunoblotting and EM of platelets from an ARC patient carrying a homozygous VPS33B nonsense variant","pmids":["35325493"],"confidence":"Medium","gaps":["Single case","Mechanism of VIPAS39 degradation without VPS33B not defined"]},{"year":2023,"claim":"Resolved the architecture of the complex as a ~315 kDa 2:3 VPS33B:VPS16B assembly with two oppositely oriented VPS33B lobes, providing a structural rationale for engaging multiple SNARE bundles and mapping a complex-disrupting ARC variant.","evidence":"SEC-MALS, CD, SAXS, negative-staining EM, truncation and missense (L30P, S243F, H344D) mutagenesis","pmids":["37062417"],"confidence":"High","gaps":["Direct SNARE-binding by the complex not experimentally shown","High-resolution atomic structure absent"]},{"year":2025,"claim":"Extended VIPAS39 function beyond canonical organelle biogenesis by showing it sorts ACSL4 into late endosomes for exosomal export, lowering intracellular ACSL4 to confer ferroptosis resistance in ovarian cancer.","evidence":"IP-MS, CD63-pHuji live-cell imaging, lipid peroxidation and viability assays, CDX/PDX xenografts","pmids":["40088627"],"confidence":"Medium","gaps":["Whether VPS33B is required for ACSL4 sorting untested","Direct VIPAS39-ACSL4 binding mode unresolved","Single-lab study"]},{"year":null,"claim":"How the VPS33B-VIPAS39 complex physically engages SNAREs to catalyze fusion, and how it selects specific cargoes for distinct lysosome-related organelles versus exosomal export, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No direct reconstituted SNARE-fusion assay for the complex","Cargo recognition specificity mechanism undefined","Atomic-resolution structure of the assembly lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1,5]}],"localization":[{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[1,2,3,9]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[2]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[10]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[0,1,2]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[2,7]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[0,4]}],"complexes":["VPS33B-VPS16B (VIPAS39) complex","HOPS-related complex"],"partners":["VPS33B","VPS33A","RAB11A","ACSL4"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9H9C1","full_name":"Spermatogenesis-defective protein 39 homolog","aliases":["VPS33B-interacting protein in apical-basolateral polarity regulator","VPS33B-interacting protein in polarity and apical restriction"],"length_aa":493,"mass_kda":57.0,"function":"Proposed to be involved in endosomal maturation implicating in part VPS33B. In epithelial cells, the VPS33B:VIPAS39 complex may play a role in the apical RAB11A-dependent recycling pathway and in the maintenance of the apical-basolateral polarity (PubMed:20190753). May play a role in lysosomal trafficking, probably via association with the core HOPS complex in a discrete population of endosomes; the functions seems to be independent of VPS33B (PubMed:19109425). May play a role in vesicular trafficking during spermatogenesis (By similarity). May be involved in direct or indirect transcriptional regulation of E-cadherin (By similarity)","subcellular_location":"Cytoplasm; Cytoplasmic vesicle; Early endosome; Recycling endosome; Late endosome","url":"https://www.uniprot.org/uniprotkb/Q9H9C1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/VIPAS39","classification":"Not Classified","n_dependent_lines":6,"n_total_lines":1208,"dependency_fraction":0.004966887417218543},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"WASF2","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/VIPAS39","total_profiled":1310},"omim":[{"mim_id":"616700","title":"COMM DOMAIN-CONTAINING PROTEIN 3; COMMD3","url":"https://www.omim.org/entry/616700"},{"mim_id":"613404","title":"ARTHROGRYPOSIS, RENAL DYSFUNCTION, AND CHOLESTASIS 2; ARCS2","url":"https://www.omim.org/entry/613404"},{"mim_id":"613401","title":"VPS33B-INTERACTING PROTEIN, APICAL-BASOLATERAL POLARITY REGULATOR, SPE39 HOMOLOG; VIPAS39","url":"https://www.omim.org/entry/613401"},{"mim_id":"608552","title":"VPS33B LATE ENDOSOME AND LYSOSOME ASSOCIATED; VPS33B","url":"https://www.omim.org/entry/608552"},{"mim_id":"606892","title":"SYNTAXIN 12; STX12","url":"https://www.omim.org/entry/606892"}],"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/VIPAS39"},"hgnc":{"alias_symbol":["VIPAR","VPS16B","SPE-39","SPE39","hSPE-39"],"prev_symbol":["C14orf133"]},"alphafold":{"accession":"Q9H9C1","domains":[{"cath_id":"-","chopping":"250-338","consensus_level":"medium","plddt":94.33,"start":250,"end":338},{"cath_id":"-","chopping":"382-440","consensus_level":"medium","plddt":95.6241,"start":382,"end":440},{"cath_id":"-","chopping":"446-493","consensus_level":"medium","plddt":95.0413,"start":446,"end":493},{"cath_id":"1.25.10","chopping":"156-248","consensus_level":"high","plddt":93.7766,"start":156,"end":248}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H9C1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H9C1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H9C1-F1-predicted_aligned_error_v6.png","plddt_mean":78.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=VIPAS39","jax_strain_url":"https://www.jax.org/strain/search?query=VIPAS39"},"sequence":{"accession":"Q9H9C1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9H9C1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9H9C1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H9C1"}},"corpus_meta":[{"pmid":"20190753","id":"PMC_20190753","title":"Mutations in VIPAR cause an arthrogryposis, renal dysfunction and cholestasis syndrome phenotype with defects in epithelial polarization.","date":"2010","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/20190753","citation_count":139,"is_preprint":false},{"pmid":"23002115","id":"PMC_23002115","title":"The VPS33B-binding protein VPS16B is required in megakaryocyte and platelet α-granule biogenesis.","date":"2012","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/23002115","citation_count":65,"is_preprint":false},{"pmid":"19109425","id":"PMC_19109425","title":"SPE-39 family proteins interact with the HOPS complex and function in lysosomal delivery.","date":"2008","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/19109425","citation_count":56,"is_preprint":false},{"pmid":"29409756","id":"PMC_29409756","title":"VPS33B and VIPAR are essential for epidermal lamellar body biogenesis and function.","date":"2018","source":"Biochimica et biophysica acta. Molecular basis of disease","url":"https://pubmed.ncbi.nlm.nih.gov/29409756","citation_count":30,"is_preprint":false},{"pmid":"23918659","id":"PMC_23918659","title":"Vps33b pathogenic mutations preferentially affect VIPAS39/SPE-39-positive endosomes.","date":"2013","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/23918659","citation_count":23,"is_preprint":false},{"pmid":"14504223","id":"PMC_14504223","title":"The Caenorhabditis elegans spe-39 gene is required for intracellular membrane reorganization during spermatogenesis.","date":"2003","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/14504223","citation_count":22,"is_preprint":false},{"pmid":"31501156","id":"PMC_31501156","title":"Mechanism of platelet α-granule biogenesis: study of cargo transport and the VPS33B-VPS16B complex in a model system.","date":"2019","source":"Blood advances","url":"https://pubmed.ncbi.nlm.nih.gov/31501156","citation_count":20,"is_preprint":false},{"pmid":"37062417","id":"PMC_37062417","title":"The Sec1-Munc18 protein VPS33B forms a uniquely bidirectional complex with VPS16B.","date":"2023","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/37062417","citation_count":11,"is_preprint":false},{"pmid":"26808426","id":"PMC_26808426","title":"Novel VIPAS39 mutation in a syndromic patient with arthrogryposis, renal tubular dysfunction and intrahepatic cholestasis.","date":"2016","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/26808426","citation_count":11,"is_preprint":false},{"pmid":"35325493","id":"PMC_35325493","title":"Platelet VPS16B is dependent on VPS33B expression, as determined in two siblings with arthrogryposis, renal dysfunction, and cholestasis syndrome.","date":"2022","source":"Journal of thrombosis and haemostasis : JTH","url":"https://pubmed.ncbi.nlm.nih.gov/35325493","citation_count":6,"is_preprint":false},{"pmid":"40088627","id":"PMC_40088627","title":"VIPAS39 confers ferroptosis resistance in epithelial ovarian cancer through exporting ACSL4.","date":"2025","source":"EBioMedicine","url":"https://pubmed.ncbi.nlm.nih.gov/40088627","citation_count":5,"is_preprint":false},{"pmid":"22677173","id":"PMC_22677173","title":"Inhibitory effect of SPE-39 due to tyrosine phosphorylation and ubiquitination on the function of Vps33B in the EGF-stimulated cells.","date":"2012","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/22677173","citation_count":4,"is_preprint":false},{"pmid":"39736737","id":"PMC_39736737","title":"VIPAS39 related arthrogryposis-renal dysfunction-cholestasis syndrome-case report and systematic review.","date":"2024","source":"Orphanet journal of rare diseases","url":"https://pubmed.ncbi.nlm.nih.gov/39736737","citation_count":2,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.06.04.657864","title":"Mechanobiological proximal tubular defects in ARC syndrome: A  <i>VPS33B</i>  CRISPR knockout study","date":"2025-06-04","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.04.657864","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8975,"output_tokens":3674,"usd":0.041017,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":11297,"output_tokens":3684,"usd":0.074292,"stage2_stop_reason":"end_turn"},"total_usd":0.115309,"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\": 2010,\n      \"finding\": \"VIPAR (VIPAS39) forms a functional complex with VPS33B that interacts with RAB11A. Knockdown of vipar in zebrafish caused biliary excretion and E-cadherin defects. In Vipar- and Vps33b-deficient mouse mIMDC-3 cells, membrane proteins were expressed abnormally, tight junctions were structurally and functionally defective, Ceacam5 was mis-sorted toward lysosomal degradation, and E-cadherin was transcriptionally downregulated, establishing that the VPS33B-VIPAR complex regulates apical-basolateral polarity in liver and kidney.\",\n      \"method\": \"Co-immunoprecipitation (VPS33B-VIPAR-RAB11A complex), zebrafish vipar knockdown with biliary/E-cadherin readouts, Vipar/Vps33b-deficient mouse cell lines with tight junction functional assays, immunofluorescence, and protein sorting assays\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, multiple model systems (zebrafish, mouse cells), multiple orthogonal functional readouts, replicated across labs\",\n      \"pmids\": [\"20190753\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The human SPE-39 orthologue (C14orf133/VIPAS39) interacts with VPS33 homologues and co-immunoprecipitates and co-sediments with other HOPS complex subunits. SPE-39 knockdown in human cells altered morphology of syntaxin 7-, syntaxin 8-, and syntaxin 13-positive endosomes and delayed mannose 6-phosphate receptor-mediated cathepsin D delivery and EGF receptor degradation, establishing VIPAS39 as a regulator of lysosomal delivery via the HOPS complex. C. elegans SPE-39 interacts in vitro with both VPS33A and VPS33B, and RNAi of VPS33B phenocopies spe-39 spermatogenesis defects.\",\n      \"method\": \"Co-immunoprecipitation, co-sedimentation, in vitro binding assay, siRNA knockdown with fluorescence microscopy and trafficking assays (cathepsin D delivery, EGFR degradation), C. elegans genetic epistasis (RNAi)\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (Co-IP, co-sedimentation, in vitro binding, functional trafficking assays, genetic epistasis) in two organisms\",\n      \"pmids\": [\"19109425\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"VPS16B (VIPAS39) was identified as a VPS33B-binding protein by yeast two-hybrid and mass spectrometry, confirmed by co-immunoprecipitation. In platelets from an ARC patient with C14orf133/VPS16B mutations, α-granules were completely absent while δ-granules were present. GFP-VPS16B in Dami megakaryocytic cells co-localized with markers of the trans-Golgi network, late endosomes, and α-granules, establishing that VPS16B is essential for platelet α-granule biogenesis.\",\n      \"method\": \"Yeast two-hybrid, mass spectrometry, co-immunoprecipitation, electron microscopy of patient platelets, immunofluorescence microscopy of GFP-VPS16B in Dami cells\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — yeast two-hybrid, MS, Co-IP, patient cell EM, and localization studies with multiple orthogonal methods\",\n      \"pmids\": [\"23002115\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Disease-causing mutations in VIPAS39/SPE-39 and VPS33B were investigated by yeast two-hybrid, immunoprecipitation, and quantitative fluorescent microscopy. Although few mutations prevent VIPAS39-VPS33B interaction, some mutants fragment VIPAS39-positive endosomes, and all mutants alter the subcellular localization of VPS33B to VIPAS39-positive endosomes, suggesting ARC syndrome results from impaired VIPAS39/SPE-39 and VPS33B-dependent endosomal maturation or fusion.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, quantitative fluorescent microscopy of mutant proteins in cells\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple methods in single lab, clear functional readout of endosomal fragmentation and mislocalization\",\n      \"pmids\": [\"23918659\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"VPS33B and VPS16B (VIPAS39) form a small, distinct complex in megakaryocytes with the same hydrodynamic radius as the recombinant VPS33B-VPS16B heterodimer purified from bacteria. The complex localizes to recycling endosomes. VPS33B deficiency (CRISPR/Cas9 KO) causes α-granule cargo (platelet factor 4, von Willebrand factor, P-selectin) degradation in lysosomes rather than correct trafficking, and VPS16B steady-state levels are significantly lower in VPS33B-KO cells, indicating VPS16B is destabilized without VPS33B.\",\n      \"method\": \"CRISPR/Cas9 knockout in imMKCL megakaryocytes, size-exclusion chromatography, recombinant protein purification, immunofluorescence co-localization, immunoblotting for cargo proteins\",\n      \"journal\": \"Blood advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — CRISPR KO with defined cargo trafficking phenotype, recombinant complex purification, and SEC analysis in one rigorous study\",\n      \"pmids\": [\"31501156\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Human VPS33B-VPS16B forms a high molecular weight complex (~315 kDa) with a VPS33B:VPS16B stoichiometry of 2:3. Structural analysis by CD, SAXS, and negative-staining EM revealed a well-folded α-helical, two-lobed shape, with each lobe containing one VPS33B molecule oriented in opposite directions. Truncated VPS16B (amino acids 143–316) is sufficient for complex formation with VPS33B. ARC-causing VPS33B missense variant L30P disrupts complex formation, whereas S243F and H344D do not. The bidirectional orientation of VPS33B molecules suggests the complex can interact with separate SNARE bundles/SNAREpins.\",\n      \"method\": \"Size-exclusion chromatography-multiangle light scattering (SEC-MALS), circular dichroism, small-angle X-ray scattering (SAXS), negative-staining EM, quantitative immunoblotting, avidin tagging, truncation/mutagenesis analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple structural methods (SAXS, EM, CD, SEC-MALS) combined with mutagenesis and stoichiometric analysis in one rigorous study\",\n      \"pmids\": [\"37062417\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Tyrosine phosphorylation of SPE-39 (VIPAS39) following EGF stimulation promotes its ubiquitination at the C-terminal region, reducing SPE-39 stability. Ubiquitination is regulated by phosphorylation of Tyr-11. Association of VPS33B with SPE-39 inhibits EGF-stimulated ubiquitination of SPE-39, stabilizing it. SPE-39 and VPS33B have an opposing functional relationship in downregulation of the EGF receptor in EGF-stimulated COS-7 cells.\",\n      \"method\": \"Ubiquitination and phosphorylation assays (immunoprecipitation/immunoblotting), site-directed mutagenesis (Tyr-11), co-immunoprecipitation, EGF receptor downregulation assay in COS-7 cells\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — site-directed mutagenesis combined with Co-IP and functional EGFR downregulation assay, single lab\",\n      \"pmids\": [\"22677173\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"VPS33B and VIPAR (VIPAS39) are essential for epidermal lamellar body biogenesis and function. Mouse knockouts of Vps33b or Vipas39 develop ichthyosis with abnormal lamellar body morphology, disrupted localization of lamellar body cargo, increased corneocyte thickness, decreased cornified envelope thickness, and reduced lipid deposition in stratum corneum, establishing a role for the VPS33B-VIPAR complex in lysosome-related organelle biogenesis in skin.\",\n      \"method\": \"Mouse knockout (Vps33b and Vipas39), histology, immunofluorescence, electron microscopy of skin biopsies and primary cells\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular basis of disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two knockout mouse models with orthogonal microscopy methods, single lab\",\n      \"pmids\": [\"29409756\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Stable expression of VPS16B (VIPAS39) in platelets, megakaryocytes, and other primary cells is dependent on VPS33B expression. A novel homozygous nonsense VPS33B variant in ARC syndrome patients caused loss of expression of both VPS33B and VPS16B in platelets, indicating VPS16B protein stability requires its partner VPS33B.\",\n      \"method\": \"Patient platelet protein expression analysis by immunoblotting, electron microscopy, confirmatory genetic testing\",\n      \"journal\": \"Journal of thrombosis and haemostasis : JTH\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — primary patient cell analysis with immunoblotting and EM, single case/lab, confirms findings from CRISPR KO study (PMID:31501156)\",\n      \"pmids\": [\"35325493\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"VIPAS39 was identified by IP-MS as a pivotal regulator that sorts ACSL4 into late endosomes, facilitating its release as exosomes. In ferroptosis-resistant ovarian cancer cells, VIPAS39 mediates exosomal export of ACSL4, reducing intracellular ACSL4 protein levels and conferring resistance to ferroptosis. Targeting VIPAS39 overcomes ferroptosis resistance and suppresses tumor growth in CDX and PDX models.\",\n      \"method\": \"Immunoprecipitation-mass spectrometry (IP-MS), live-cell imaging with pH-sensitive CD63-pHuji reporter, protein binding assays, cell viability and lipid peroxidation assays, CDX and PDX xenograft models\",\n      \"journal\": \"EBioMedicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — IP-MS identification validated with live-cell reporter assay and in vivo xenograft, multiple orthogonal methods in single lab\",\n      \"pmids\": [\"40088627\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"C. elegans SPE-39 (ortholog of VIPAS39) encodes a novel hydrophilic protein required for intracellular membrane reorganization during spermatogenesis. In spe-39 mutants, membranous organelles (MOs) are absent and fibrous bodies are disorganized, replaced by small vesicles with internal membranes. SPE-39 protein is distributed throughout the cytoplasm and not specifically associated with FB-MOs. The gene has orthologs in Drosophila and humans but no yeast homolog, suggesting a metazoan-specific membrane biogenesis function.\",\n      \"method\": \"Genetic analysis (spe-39 mutants), electron microscopy of spermatocytes, immunofluorescence with SPE-39-specific antiserum, gene identification/sequencing\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function with EM ultrastructural phenotype and immunofluorescence localization in C. elegans ortholog, single lab\",\n      \"pmids\": [\"14504223\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"VIPAS39 (VPS16B/VIPAR/SPE-39) forms a stoichiometric, bidirectional heteromeric complex with VPS33B (2 VPS33B : 3 VPS16B, ~315 kDa) that functions as a metazoan-specific component of the HOPS-related endosomal trafficking machinery, facilitating vesicular fusion via SNARE interactions; the complex localizes to RAB11A-positive recycling endosomes, late endosomes, and trans-Golgi network, where it directs cargo sorting for lysosome-related organelle biogenesis (platelet α-granules, epidermal lamellar bodies), maintains apical-basolateral epithelial polarity, and regulates EGFR downregulation—with VPS33B required for VPS16B protein stability, and VIPAS39 additionally mediating exosomal export of ACSL4 to modulate ferroptosis sensitivity.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"VIPAS39 (VPS16B/VIPAR/SPE-39) is a metazoan-specific endosomal trafficking factor that operates as an obligate stoichiometric partner of VPS33B, together forming a HOPS-related complex that directs vesicular fusion and cargo sorting for the biogenesis of lysosome-related organelles [#1, #2]. The two proteins assemble into a defined ~315 kDa heteromer with a 2:3 VPS33B:VPS16B stoichiometry adopting a two-lobed, bidirectional architecture in which each lobe contains an oppositely oriented VPS33B, an arrangement compatible with engaging separate SNARE bundles during membrane fusion [#5]. The complex acts at recycling endosomes, late endosomes, and the trans-Golgi network, where it controls lysosomal cargo delivery, EGF receptor degradation, and apical-basolateral epithelial polarity—loss of VIPAS39 fragments endosomes, mis-sorts membrane cargo toward lysosomal degradation, and disrupts tight junctions in liver and kidney models [#0, #1, #3]. Through this sorting activity VIPAS39 and VPS33B are required for platelet α-granule and epidermal lamellar body biogenesis, and mutations in VIPAS39/VPS33B cause ARC (arthrogryposis–renal dysfunction–cholestasis) syndrome [#2, #7, #3]. VPS16B protein stability is strictly dependent on VPS33B, with VPS33B loss destabilizing VIPAS39 in megakaryocytes and patient cells [#4, #8]. Beyond its core trafficking role, VIPAS39 sorts ACSL4 into late endosomes for exosomal export, lowering intracellular ACSL4 and conferring ferroptosis resistance in ovarian cancer [#9].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Established that the VIPAS39 ortholog encodes a novel, metazoan-specific cytoplasmic protein required for intracellular membrane reorganization, defining a membrane-biogenesis function distinct from yeast trafficking machinery.\",\n      \"evidence\": \"Genetic loss-of-function and EM ultrastructure of spe-39 mutant C. elegans spermatocytes with immunofluorescence localization\",\n      \"pmids\": [\"14504223\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No molecular partners identified at this stage\", \"Biochemical activity undefined\", \"Mammalian relevance not yet established\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Connected VIPAS39 to the HOPS machinery and lysosomal delivery by showing it binds VPS33 homologues and that its loss perturbs endosomal trafficking, identifying the molecular system in which it acts.\",\n      \"evidence\": \"Co-IP, co-sedimentation, in vitro binding, siRNA knockdown with cathepsin D and EGFR trafficking assays in human cells, plus C. elegans RNAi epistasis\",\n      \"pmids\": [\"19109425\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and complex architecture unknown\", \"Whether VIPAS39 acts with VPS33A or VPS33B in vivo unresolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defined the VPS33B-VIPAS39 complex as a regulator of epithelial apical-basolateral polarity via RAB11A-associated trafficking, linking trafficking defects to organ-level (liver/kidney) phenotypes.\",\n      \"evidence\": \"Reciprocal Co-IP for VPS33B-VIPAR-RAB11A, zebrafish knockdown, Vipar/Vps33b-deficient mouse cells with tight junction and cargo-sorting readouts\",\n      \"pmids\": [\"20190753\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct mechanism of cargo selection not resolved\", \"How polarity defects arise from endosomal fusion failure not defined at molecular level\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showed the complex is essential for platelet α-granule biogenesis, establishing VIPAS39's role in lysosome-related organelle formation and its disease relevance to ARC syndrome.\",\n      \"evidence\": \"Yeast two-hybrid, MS, Co-IP, EM of ARC patient platelets, GFP-VPS16B localization in Dami megakaryocytes\",\n      \"pmids\": [\"23002115\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cargo routing mechanism into nascent α-granules not detailed\", \"δ-granule independence not mechanistically explained\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Revealed post-translational regulation of VIPAS39 by EGF-induced Tyr-11 phosphorylation and C-terminal ubiquitination, with VPS33B binding stabilizing it, indicating opposing roles in EGFR downregulation.\",\n      \"evidence\": \"Phosphorylation/ubiquitination assays, Tyr-11 site-directed mutagenesis, Co-IP, EGFR downregulation in COS-7 cells\",\n      \"pmids\": [\"22677173\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Kinase and E3 ligase not identified\", \"Single-lab, single cell system\", \"Physiological significance of opposing VPS33B/VIPAS39 EGFR roles unclear\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Clarified how ARC mutations cause disease, showing most mutants preserve the VIPAS39-VPS33B interaction but mislocalize VPS33B and fragment endosomes, pointing to impaired endosomal maturation/fusion rather than complex disruption.\",\n      \"evidence\": \"Yeast two-hybrid, Co-IP, quantitative fluorescent microscopy of mutant proteins\",\n      \"pmids\": [\"23918659\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking endosome fragmentation to cargo failure unresolved\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstrated VPS33B-VIPAS39 forms a discrete heterodimer at recycling endosomes and that VIPAS39 depends on VPS33B for stability, defining the functional unit and showing cargo is degraded in lysosomes when the complex is lost.\",\n      \"evidence\": \"CRISPR/Cas9 KO in imMKCL megakaryocytes, SEC, recombinant complex purification, cargo immunoblotting and co-localization\",\n      \"pmids\": [\"31501156\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Higher-order stoichiometry not yet resolved\", \"SNARE engagement not demonstrated directly\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Confirmed in patient cells that VIPAS39 protein stability requires VPS33B, reinforcing the interdependence of the complex subunits.\",\n      \"evidence\": \"Immunoblotting and EM of platelets from an ARC patient carrying a homozygous VPS33B nonsense variant\",\n      \"pmids\": [\"35325493\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single case\", \"Mechanism of VIPAS39 degradation without VPS33B not defined\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Resolved the architecture of the complex as a ~315 kDa 2:3 VPS33B:VPS16B assembly with two oppositely oriented VPS33B lobes, providing a structural rationale for engaging multiple SNARE bundles and mapping a complex-disrupting ARC variant.\",\n      \"evidence\": \"SEC-MALS, CD, SAXS, negative-staining EM, truncation and missense (L30P, S243F, H344D) mutagenesis\",\n      \"pmids\": [\"37062417\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct SNARE-binding by the complex not experimentally shown\", \"High-resolution atomic structure absent\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extended VIPAS39 function beyond canonical organelle biogenesis by showing it sorts ACSL4 into late endosomes for exosomal export, lowering intracellular ACSL4 to confer ferroptosis resistance in ovarian cancer.\",\n      \"evidence\": \"IP-MS, CD63-pHuji live-cell imaging, lipid peroxidation and viability assays, CDX/PDX xenografts\",\n      \"pmids\": [\"40088627\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether VPS33B is required for ACSL4 sorting untested\", \"Direct VIPAS39-ACSL4 binding mode unresolved\", \"Single-lab study\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the VPS33B-VIPAS39 complex physically engages SNAREs to catalyze fusion, and how it selects specific cargoes for distinct lysosome-related organelles versus exosomal export, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct reconstituted SNARE-fusion assay for the complex\", \"Cargo recognition specificity mechanism undefined\", \"Atomic-resolution structure of the assembly lacking\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [1, 2, 3, 9]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [10]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [2, 7]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"complexes\": [\"VPS33B-VPS16B (VIPAS39) complex\", \"HOPS-related complex\"],\n    \"partners\": [\"VPS33B\", \"VPS33A\", \"RAB11A\", \"ACSL4\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}