{"gene":"VPS52","run_date":"2026-06-11T09:02:06","timeline":{"discoveries":[{"year":2003,"finding":"VPS52 (Vps52p) is a core subunit of the tetrameric GARP (Golgi-Associated Retrograde Protein) complex (Vps51/52/53/54), which is required for retrograde transport from both early and late endosomes back to the TGN. Vps51p mediates the interaction between the Vps52/53/54 subcomplex and the late Golgi t-SNARE Tlg1p, providing a molecular link between the tethering and fusion machinery.","method":"Genetic analysis, co-immunoprecipitation, yeast mutant phenotyping","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, genetic epistasis, multiple orthogonal methods in a focused mechanistic study replicated across multiple alleles","pmids":["12686613"],"is_preprint":false},{"year":2012,"finding":"Mouse Vps52, a homolog of yeast VPS52 involved in retrograde endosomal trafficking, is required for pluripotent epiblast differentiation into embryonic ectoderm via cell-cell interactions. The t(w5) mutation was mapped by positional cloning to Vps52, and loss of function in extraembryonic tissues disrupts embryonic ectoderm growth and differentiation before gastrulation.","method":"Positional cloning, loss-of-function mouse genetics, embryological analysis","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — positional cloning plus loss-of-function phenotype, single lab, no biochemical reconstitution","pmids":["23142660"],"is_preprint":false},{"year":2017,"finding":"RNF41, an E3 ubiquitin ligase, interacts with VPS52 via their coiled-coil domains, ubiquitinates VPS52, and redistributes it away from VPS53 (a shared GARP/EARP subunit) toward RNF41 bodies, implicating VPS52 ubiquitination in regulating GARP/EARP complex assembly.","method":"Array MAPPIT protein-protein interaction screen, co-immunoprecipitation, coiled-coil domain mapping, ubiquitination assay","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MAPPIT screen plus Co-IP and ubiquitination assay, single lab, multiple orthogonal methods","pmids":["28542518"],"is_preprint":false},{"year":2017,"finding":"VPS52 overexpression in gastric cancer cells activates the cathepsin D/Bax/cytochrome C/caspase 9/caspase 3 apoptotic pathway, reducing cell viability in vitro and tumor growth in vivo, identifying VPS52 as a regulator of apoptosis through the cathepsin D pathway.","method":"Overexpression in gastric cancer cell lines, xenograft mouse model, western blot pathway analysis, viability and apoptosis assays","journal":"Journal of molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain-of-function with defined pathway readout in vitro and in vivo, single lab, multiple assays","pmids":["28791438"],"is_preprint":false},{"year":2020,"finding":"VPS52 is a novel binding partner of GTP-bound Arf6 (and not other Arf family members), identified by yeast two-hybrid screening. VPS52 is localized to trans-Golgi network and vesicular endomembranes in hippocampal neurons. Knockdown of Vps52 increases total axon and dendrite length; this is rescued by full-length Vps52 but only partially by a mutant lacking Arf6-binding ability, indicating that the Arf6 interaction specifically mediates VPS52's role in regulating dendritic (but not axonal) length.","method":"Yeast two-hybrid screening, shRNA knockdown, rescue with wild-type and Arf6-binding mutant VPS52, immunohistochemistry, neurite length quantification","journal":"Brain research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid plus loss-of-function rescue with domain mutant, single lab, multiple orthogonal methods","pmids":["32473257"],"is_preprint":false},{"year":2021,"finding":"VPS52, as a subunit of the GARP complex, functions as a Rab6 effector responsible for Rab6-dependent secretory cargo trafficking. Knockout of VPS52 phenocopies Rab6 knockout, causing attenuated secretion and lysosomal accumulation of secretory cargos. The C-terminal region of VPS52 is required for restoring these phenotypes and for proper sorting of lysosomal proteins.","method":"CRISPR/Cas9 knockout cell lines, secretion and lysosomal accumulation assays, domain rescue experiments","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockout phenocopy of Rab6 KO plus domain rescue, single lab, multiple functional readouts","pmids":["34023780"],"is_preprint":false},{"year":2025,"finding":"Aphid effectors Mp1 and Mp58 interact with each other in planta and in vitro, forming an oligomeric complex that associates with host VPS52 to form a trimeric Mp1-Mp58-VPS52 complex localizing to vesicle-like structures, indicating VPS52 is targeted at endosomal/vesicular compartments during aphid infestation.","method":"Co-immunoprecipitation, in vitro recombinant protein interaction, confocal microscopy, computational structure prediction","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 / Weak — preprint, single lab, Co-IP and imaging but no direct functional mutagenesis of VPS52 itself","pmids":["bio_10.1101_2025.05.12.653458"],"is_preprint":true}],"current_model":"VPS52 is a core subunit of the tetrameric GARP and EARP tethering complexes that mediates retrograde vesicular transport from endosomes to the trans-Golgi network by linking to t-SNAREs (via Vps51p) and functioning as a Rab6 effector; it also interacts with GTP-bound Arf6 to regulate neurite outgrowth, is ubiquitinated and redistributed by the E3 ligase RNF41, and can activate the cathepsin D apoptotic pathway in cancer cells, while in mouse development it is required in extraembryonic tissues for epiblast differentiation via cell-cell interactions."},"narrative":{"mechanistic_narrative":"VPS52 is a core subunit of the tetrameric GARP (Golgi-Associated Retrograde Protein) tethering complex (Vps51/52/53/54) that mediates retrograde vesicular transport from early and late endosomes back to the trans-Golgi network, with Vps51p linking the Vps52/53/54 subcomplex to the late-Golgi t-SNARE Tlg1p to couple tethering with membrane fusion [PMID:12686613]. As part of GARP, VPS52 acts as a Rab6 effector required for Rab6-dependent secretory cargo trafficking; its loss phenocopies Rab6 knockout, attenuating secretion and causing lysosomal accumulation of cargo, and its C-terminal region is required to restore proper sorting [PMID:34023780]. VPS52 also binds GTP-loaded Arf6 specifically, localizing to the TGN and vesicular endomembranes in hippocampal neurons, where the Arf6 interaction mediates control of dendritic length [PMID:32473257]. Its participation in tethering complexes is regulated by the E3 ubiquitin ligase RNF41, which interacts with VPS52 through coiled-coil domains, ubiquitinates it, and redistributes it away from the shared subunit VPS53 [PMID:28542518]. Beyond trafficking, VPS52 is required in extraembryonic tissues for pluripotent epiblast differentiation into embryonic ectoderm via cell-cell interactions [PMID:23142660], and its overexpression activates the cathepsin D/Bax/cytochrome C/caspase 9/caspase 3 apoptotic pathway in gastric cancer cells [PMID:28791438].","teleology":[{"year":2003,"claim":"Established VPS52 as a structural subunit of the GARP tethering complex and defined how that complex bridges to the fusion machinery, answering how endosome-to-TGN retrograde cargo is captured at the Golgi.","evidence":"Genetic analysis, co-immunoprecipitation, and yeast mutant phenotyping of the Vps51/52/53/54 complex","pmids":["12686613"],"confidence":"High","gaps":["No structural model of how VPS52 contributes to the tetramer architecture","Did not define mammalian cargo specificity","EARP complex membership not addressed in this study"]},{"year":2012,"claim":"Connected VPS52 trafficking function to a developmental requirement, showing that retrograde transport in extraembryonic tissues is needed for epiblast differentiation before gastrulation.","evidence":"Positional cloning of the t(w5) mutation and loss-of-function mouse embryological analysis","pmids":["23142660"],"confidence":"Medium","gaps":["Molecular cargo whose mistrafficking drives the phenotype not identified","No biochemical reconstitution linking trafficking defect to differentiation","Mechanism of cell-cell interaction failure unresolved"]},{"year":2017,"claim":"Identified a post-translational regulator of GARP/EARP assembly, showing RNF41 ubiquitinates VPS52 and removes it from the shared VPS53 subunit.","evidence":"Array MAPPIT interaction screen, co-immunoprecipitation, coiled-coil domain mapping, and ubiquitination assay","pmids":["28542518"],"confidence":"Medium","gaps":["Functional consequence of ubiquitination for trafficking flux not measured","Ubiquitin chain type and target lysines not defined","Single lab, no in vivo validation"]},{"year":2017,"claim":"Revealed a trafficking-adjacent role in apoptosis, showing VPS52 overexpression engages the cathepsin D mitochondrial apoptotic cascade in gastric cancer.","evidence":"Overexpression in gastric cancer cell lines, xenograft model, and western blot pathway analysis with viability/apoptosis assays","pmids":["28791438"],"confidence":"Medium","gaps":["Mechanistic link between trafficking function and cathepsin D activation unclear","Gain-of-function only; endogenous loss-of-function effect on apoptosis untested","Direct molecular target of VPS52 in the pathway not identified"]},{"year":2020,"claim":"Defined a small-GTPase partner and a neuronal function, showing VPS52 binds GTP-Arf6 specifically and uses that interaction to regulate dendritic length.","evidence":"Yeast two-hybrid screening, shRNA knockdown with wild-type and Arf6-binding mutant rescue, and neurite length quantification in hippocampal neurons","pmids":["32473257"],"confidence":"Medium","gaps":["Whether Arf6 binding occurs within the GARP/EARP context unknown","Axonal regulation appears Arf6-independent and mechanistically unexplained","No structural definition of the Arf6-binding interface"]},{"year":2021,"claim":"Placed VPS52/GARP downstream of Rab6 in secretory trafficking, showing VPS52 acts as a Rab6 effector whose loss phenocopies Rab6 knockout.","evidence":"CRISPR/Cas9 knockout cell lines, secretion and lysosomal accumulation assays, and C-terminal domain rescue","pmids":["34023780"],"confidence":"Medium","gaps":["Direct Rab6-VPS52 binding interface not mapped","How the same subunit serves both Rab6 and Arf6 functions unresolved","Single lab, mammalian cell lines only"]},{"year":2025,"claim":"Implicated VPS52 as a host target during plant-aphid interaction, showing it is recruited into a trimeric complex with aphid effectors at vesicular compartments.","evidence":"Co-immunoprecipitation, in vitro recombinant interaction, and confocal microscopy (preprint)","pmids":["bio_10.1101_2025.05.12.653458"],"confidence":"Low","gaps":["Preprint; no functional mutagenesis of VPS52 itself","Consequence of effector binding for host trafficking unknown","Relevance to mammalian VPS52 biology unclear"]},{"year":null,"claim":"How a single VPS52 subunit integrates Rab6- and Arf6-dependent inputs, GARP versus EARP assembly, and RNF41 ubiquitination into coordinated trafficking decisions remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of mammalian GARP/EARP with VPS52","Regulatory logic coupling ubiquitination to complex assembly undefined","Cargo repertoire and tissue-specific functions incompletely mapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0]}],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[4]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[4,6]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[0,5]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[5]}],"complexes":["GARP complex","EARP complex"],"partners":["VPS53","VPS51","VPS54","RNF41","ARF6","RAB6"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8N1B4","full_name":"Vacuolar protein sorting-associated protein 52 homolog","aliases":["SAC2 suppressor of actin mutations 2-like protein"],"length_aa":723,"mass_kda":82.2,"function":"Acts as a component of the GARP complex that is involved in retrograde transport from early and late endosomes to the trans-Golgi network (TGN). The GARP complex is required for the maintenance of the cycling of mannose 6-phosphate receptors between the TGN and endosomes, this cycling is necessary for proper lysosomal sorting of acid hydrolases such as CTSD (PubMed:15878329, PubMed:18367545). Acts as a component of the EARP complex that is involved in endocytic recycling. The EARP complex associates with Rab4-positive endosomes and promotes recycling of internalized transferrin receptor (TFRC) to the plasma membrane (PubMed:25799061)","subcellular_location":"Golgi apparatus, trans-Golgi network membrane; Endosome membrane; Recycling endosome","url":"https://www.uniprot.org/uniprotkb/Q8N1B4/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/VPS52","classification":"Not Classified","n_dependent_lines":425,"n_total_lines":1208,"dependency_fraction":0.3518211920529801},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/VPS52","total_profiled":1310},"omim":[{"mim_id":"616465","title":"VPS50, EARP/GARPII COMPLEX SUBUNIT; VPS50","url":"https://www.omim.org/entry/616465"},{"mim_id":"615850","title":"VPS53 SUBUNIT OF GARP COMPLEX; VPS53","url":"https://www.omim.org/entry/615850"},{"mim_id":"615738","title":"VPS51 SUBUNIT OF GARP COMPLEX; VPS51","url":"https://www.omim.org/entry/615738"},{"mim_id":"614633","title":"VPS54 SUBUNIT OF GARP COMPLEX; VPS54","url":"https://www.omim.org/entry/614633"},{"mim_id":"603443","title":"VPS52 SUBUNIT OF GARP COMPLEX; VPS52","url":"https://www.omim.org/entry/603443"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/VPS52"},"hgnc":{"alias_symbol":["ARE1"],"prev_symbol":["SACM2L"]},"alphafold":{"accession":"Q8N1B4","domains":[{"cath_id":"-","chopping":"178-276","consensus_level":"high","plddt":92.0921,"start":178,"end":276},{"cath_id":"-","chopping":"307-326_339-478","consensus_level":"high","plddt":93.721,"start":307,"end":478},{"cath_id":"-","chopping":"607-718","consensus_level":"high","plddt":90.3438,"start":607,"end":718}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8N1B4","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8N1B4-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8N1B4-F1-predicted_aligned_error_v6.png","plddt_mean":85.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=VPS52","jax_strain_url":"https://www.jax.org/strain/search?query=VPS52"},"sequence":{"accession":"Q8N1B4","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8N1B4.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8N1B4/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8N1B4"}},"corpus_meta":[{"pmid":"12686613","id":"PMC_12686613","title":"Vps51p mediates the association of the GARP (Vps52/53/54) complex with the late Golgi t-SNARE Tlg1p.","date":"2003","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/12686613","citation_count":153,"is_preprint":false},{"pmid":"29467406","id":"PMC_29467406","title":"Genetic variations in ARE1 mediate grain yield by modulating nitrogen utilization in rice.","date":"2018","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/29467406","citation_count":96,"is_preprint":false},{"pmid":"28100451","id":"PMC_28100451","title":"An Aphid Effector Targets Trafficking Protein VPS52 in a Host-Specific Manner to Promote Virulence.","date":"2017","source":"Plant physiology","url":"https://pubmed.ncbi.nlm.nih.gov/28100451","citation_count":80,"is_preprint":false},{"pmid":"34270164","id":"PMC_34270164","title":"Increasing yield potential through manipulating of an ARE1 ortholog related to nitrogen use efficiency in wheat by CRISPR/Cas9.","date":"2021","source":"Journal of integrative plant biology","url":"https://pubmed.ncbi.nlm.nih.gov/34270164","citation_count":55,"is_preprint":false},{"pmid":"12210484","id":"PMC_12210484","title":"Linkage between polymorphisms in the prostate specific antigen ARE1 gene region, prostate cancer risk, and circulating tumor cells.","date":"2002","source":"The Prostate","url":"https://pubmed.ncbi.nlm.nih.gov/12210484","citation_count":55,"is_preprint":false},{"pmid":"33930508","id":"PMC_33930508","title":"The Ghd7 transcription factor represses ARE1 expression to enhance nitrogen utilization and grain yield in rice.","date":"2021","source":"Molecular plant","url":"https://pubmed.ncbi.nlm.nih.gov/33930508","citation_count":52,"is_preprint":false},{"pmid":"23142660","id":"PMC_23142660","title":"Molecular identification of t(w5): Vps52 promotes pluripotential cell differentiation through cell-cell interactions.","date":"2012","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/23142660","citation_count":29,"is_preprint":false},{"pmid":"31443450","id":"PMC_31443450","title":"The GATA-Type Transcriptional Factor Are1 Modulates the Expression of Extracellular Proteases and Cellulases in Trichoderma reesei.","date":"2019","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/31443450","citation_count":25,"is_preprint":false},{"pmid":"24120453","id":"PMC_24120453","title":"Phosphatidic acid and phosphoinositides facilitate liposome association of Yas3p and potentiate derepression of ARE1 (alkane-responsive element one)-mediated transcription control.","date":"2013","source":"Fungal genetics and biology : FG & B","url":"https://pubmed.ncbi.nlm.nih.gov/24120453","citation_count":19,"is_preprint":false},{"pmid":"28791438","id":"PMC_28791438","title":"VPS52 induces apoptosis via cathepsin D in gastric cancer.","date":"2017","source":"Journal of molecular medicine (Berlin, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/28791438","citation_count":14,"is_preprint":false},{"pmid":"28542518","id":"PMC_28542518","title":"RNF41 interacts with the VPS52 subunit of the GARP and EARP complexes.","date":"2017","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/28542518","citation_count":13,"is_preprint":false},{"pmid":"32473257","id":"PMC_32473257","title":"The Vps52 subunit of the GARP and EARP complexes is a novel Arf6-interacting protein that negatively regulates neurite outgrowth of hippocampal neurons.","date":"2020","source":"Brain research","url":"https://pubmed.ncbi.nlm.nih.gov/32473257","citation_count":10,"is_preprint":false},{"pmid":"34023780","id":"PMC_34023780","title":"Knockout analysis of Rab6 effector proteins revealed the role of VPS52 in the secretory pathway.","date":"2021","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/34023780","citation_count":9,"is_preprint":false},{"pmid":"39348793","id":"PMC_39348793","title":"Are1-mediated nitrogen metabolism is associated with iron regulation in the mycoparasite Trichoderma atroviride.","date":"2024","source":"Microbiological research","url":"https://pubmed.ncbi.nlm.nih.gov/39348793","citation_count":2,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.05.12.653458","title":"The highly conserved aphid effector pair Mp1-Mp58 associates to form an effector complex that targets host trafficking protein VPS52","date":"2025-05-13","source":"bioRxiv","url":"https://doi.org/10.1101/2025.05.12.653458","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8770,"output_tokens":1908,"usd":0.027465,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8761,"output_tokens":2926,"usd":0.058478,"stage2_stop_reason":"end_turn"},"total_usd":0.085943,"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\": 2003,\n      \"finding\": \"VPS52 (Vps52p) is a core subunit of the tetrameric GARP (Golgi-Associated Retrograde Protein) complex (Vps51/52/53/54), which is required for retrograde transport from both early and late endosomes back to the TGN. Vps51p mediates the interaction between the Vps52/53/54 subcomplex and the late Golgi t-SNARE Tlg1p, providing a molecular link between the tethering and fusion machinery.\",\n      \"method\": \"Genetic analysis, co-immunoprecipitation, yeast mutant phenotyping\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, genetic epistasis, multiple orthogonal methods in a focused mechanistic study replicated across multiple alleles\",\n      \"pmids\": [\"12686613\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Mouse Vps52, a homolog of yeast VPS52 involved in retrograde endosomal trafficking, is required for pluripotent epiblast differentiation into embryonic ectoderm via cell-cell interactions. The t(w5) mutation was mapped by positional cloning to Vps52, and loss of function in extraembryonic tissues disrupts embryonic ectoderm growth and differentiation before gastrulation.\",\n      \"method\": \"Positional cloning, loss-of-function mouse genetics, embryological analysis\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — positional cloning plus loss-of-function phenotype, single lab, no biochemical reconstitution\",\n      \"pmids\": [\"23142660\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"RNF41, an E3 ubiquitin ligase, interacts with VPS52 via their coiled-coil domains, ubiquitinates VPS52, and redistributes it away from VPS53 (a shared GARP/EARP subunit) toward RNF41 bodies, implicating VPS52 ubiquitination in regulating GARP/EARP complex assembly.\",\n      \"method\": \"Array MAPPIT protein-protein interaction screen, co-immunoprecipitation, coiled-coil domain mapping, ubiquitination assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MAPPIT screen plus Co-IP and ubiquitination assay, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"28542518\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"VPS52 overexpression in gastric cancer cells activates the cathepsin D/Bax/cytochrome C/caspase 9/caspase 3 apoptotic pathway, reducing cell viability in vitro and tumor growth in vivo, identifying VPS52 as a regulator of apoptosis through the cathepsin D pathway.\",\n      \"method\": \"Overexpression in gastric cancer cell lines, xenograft mouse model, western blot pathway analysis, viability and apoptosis assays\",\n      \"journal\": \"Journal of molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain-of-function with defined pathway readout in vitro and in vivo, single lab, multiple assays\",\n      \"pmids\": [\"28791438\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"VPS52 is a novel binding partner of GTP-bound Arf6 (and not other Arf family members), identified by yeast two-hybrid screening. VPS52 is localized to trans-Golgi network and vesicular endomembranes in hippocampal neurons. Knockdown of Vps52 increases total axon and dendrite length; this is rescued by full-length Vps52 but only partially by a mutant lacking Arf6-binding ability, indicating that the Arf6 interaction specifically mediates VPS52's role in regulating dendritic (but not axonal) length.\",\n      \"method\": \"Yeast two-hybrid screening, shRNA knockdown, rescue with wild-type and Arf6-binding mutant VPS52, immunohistochemistry, neurite length quantification\",\n      \"journal\": \"Brain research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid plus loss-of-function rescue with domain mutant, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"32473257\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"VPS52, as a subunit of the GARP complex, functions as a Rab6 effector responsible for Rab6-dependent secretory cargo trafficking. Knockout of VPS52 phenocopies Rab6 knockout, causing attenuated secretion and lysosomal accumulation of secretory cargos. The C-terminal region of VPS52 is required for restoring these phenotypes and for proper sorting of lysosomal proteins.\",\n      \"method\": \"CRISPR/Cas9 knockout cell lines, secretion and lysosomal accumulation assays, domain rescue experiments\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockout phenocopy of Rab6 KO plus domain rescue, single lab, multiple functional readouts\",\n      \"pmids\": [\"34023780\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Aphid effectors Mp1 and Mp58 interact with each other in planta and in vitro, forming an oligomeric complex that associates with host VPS52 to form a trimeric Mp1-Mp58-VPS52 complex localizing to vesicle-like structures, indicating VPS52 is targeted at endosomal/vesicular compartments during aphid infestation.\",\n      \"method\": \"Co-immunoprecipitation, in vitro recombinant protein interaction, confocal microscopy, computational structure prediction\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — preprint, single lab, Co-IP and imaging but no direct functional mutagenesis of VPS52 itself\",\n      \"pmids\": [\"bio_10.1101_2025.05.12.653458\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"VPS52 is a core subunit of the tetrameric GARP and EARP tethering complexes that mediates retrograde vesicular transport from endosomes to the trans-Golgi network by linking to t-SNAREs (via Vps51p) and functioning as a Rab6 effector; it also interacts with GTP-bound Arf6 to regulate neurite outgrowth, is ubiquitinated and redistributed by the E3 ligase RNF41, and can activate the cathepsin D apoptotic pathway in cancer cells, while in mouse development it is required in extraembryonic tissues for epiblast differentiation via cell-cell interactions.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"VPS52 is a core subunit of the tetrameric GARP (Golgi-Associated Retrograde Protein) tethering complex (Vps51/52/53/54) that mediates retrograde vesicular transport from early and late endosomes back to the trans-Golgi network, with Vps51p linking the Vps52/53/54 subcomplex to the late-Golgi t-SNARE Tlg1p to couple tethering with membrane fusion [#0]. As part of GARP, VPS52 acts as a Rab6 effector required for Rab6-dependent secretory cargo trafficking; its loss phenocopies Rab6 knockout, attenuating secretion and causing lysosomal accumulation of cargo, and its C-terminal region is required to restore proper sorting [#5]. VPS52 also binds GTP-loaded Arf6 specifically, localizing to the TGN and vesicular endomembranes in hippocampal neurons, where the Arf6 interaction mediates control of dendritic length [#4]. Its participation in tethering complexes is regulated by the E3 ubiquitin ligase RNF41, which interacts with VPS52 through coiled-coil domains, ubiquitinates it, and redistributes it away from the shared subunit VPS53 [#2]. Beyond trafficking, VPS52 is required in extraembryonic tissues for pluripotent epiblast differentiation into embryonic ectoderm via cell-cell interactions [#1], and its overexpression activates the cathepsin D/Bax/cytochrome C/caspase 9/caspase 3 apoptotic pathway in gastric cancer cells [#3].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Established VPS52 as a structural subunit of the GARP tethering complex and defined how that complex bridges to the fusion machinery, answering how endosome-to-TGN retrograde cargo is captured at the Golgi.\",\n      \"evidence\": \"Genetic analysis, co-immunoprecipitation, and yeast mutant phenotyping of the Vps51/52/53/54 complex\",\n      \"pmids\": [\"12686613\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No structural model of how VPS52 contributes to the tetramer architecture\",\n        \"Did not define mammalian cargo specificity\",\n        \"EARP complex membership not addressed in this study\"\n      ]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Connected VPS52 trafficking function to a developmental requirement, showing that retrograde transport in extraembryonic tissues is needed for epiblast differentiation before gastrulation.\",\n      \"evidence\": \"Positional cloning of the t(w5) mutation and loss-of-function mouse embryological analysis\",\n      \"pmids\": [\"23142660\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Molecular cargo whose mistrafficking drives the phenotype not identified\",\n        \"No biochemical reconstitution linking trafficking defect to differentiation\",\n        \"Mechanism of cell-cell interaction failure unresolved\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identified a post-translational regulator of GARP/EARP assembly, showing RNF41 ubiquitinates VPS52 and removes it from the shared VPS53 subunit.\",\n      \"evidence\": \"Array MAPPIT interaction screen, co-immunoprecipitation, coiled-coil domain mapping, and ubiquitination assay\",\n      \"pmids\": [\"28542518\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Functional consequence of ubiquitination for trafficking flux not measured\",\n        \"Ubiquitin chain type and target lysines not defined\",\n        \"Single lab, no in vivo validation\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Revealed a trafficking-adjacent role in apoptosis, showing VPS52 overexpression engages the cathepsin D mitochondrial apoptotic cascade in gastric cancer.\",\n      \"evidence\": \"Overexpression in gastric cancer cell lines, xenograft model, and western blot pathway analysis with viability/apoptosis assays\",\n      \"pmids\": [\"28791438\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanistic link between trafficking function and cathepsin D activation unclear\",\n        \"Gain-of-function only; endogenous loss-of-function effect on apoptosis untested\",\n        \"Direct molecular target of VPS52 in the pathway not identified\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Defined a small-GTPase partner and a neuronal function, showing VPS52 binds GTP-Arf6 specifically and uses that interaction to regulate dendritic length.\",\n      \"evidence\": \"Yeast two-hybrid screening, shRNA knockdown with wild-type and Arf6-binding mutant rescue, and neurite length quantification in hippocampal neurons\",\n      \"pmids\": [\"32473257\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether Arf6 binding occurs within the GARP/EARP context unknown\",\n        \"Axonal regulation appears Arf6-independent and mechanistically unexplained\",\n        \"No structural definition of the Arf6-binding interface\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Placed VPS52/GARP downstream of Rab6 in secretory trafficking, showing VPS52 acts as a Rab6 effector whose loss phenocopies Rab6 knockout.\",\n      \"evidence\": \"CRISPR/Cas9 knockout cell lines, secretion and lysosomal accumulation assays, and C-terminal domain rescue\",\n      \"pmids\": [\"34023780\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct Rab6-VPS52 binding interface not mapped\",\n        \"How the same subunit serves both Rab6 and Arf6 functions unresolved\",\n        \"Single lab, mammalian cell lines only\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Implicated VPS52 as a host target during plant-aphid interaction, showing it is recruited into a trimeric complex with aphid effectors at vesicular compartments.\",\n      \"evidence\": \"Co-immunoprecipitation, in vitro recombinant interaction, and confocal microscopy (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.05.12.653458\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Preprint; no functional mutagenesis of VPS52 itself\",\n        \"Consequence of effector binding for host trafficking unknown\",\n        \"Relevance to mammalian VPS52 biology unclear\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a single VPS52 subunit integrates Rab6- and Arf6-dependent inputs, GARP versus EARP assembly, and RNF41 ubiquitination into coordinated trafficking decisions remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No structural model of mammalian GARP/EARP with VPS52\",\n        \"Regulatory logic coupling ubiquitination to complex assembly undefined\",\n        \"Cargo repertoire and tissue-specific functions incompletely mapped\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [4, 6]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"complexes\": [\"GARP complex\", \"EARP complex\"],\n    \"partners\": [\"VPS53\", \"VPS51\", \"VPS54\", \"RNF41\", \"ARF6\", \"RAB6\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":5,"faith_pct":80.0}}