{"gene":"AP5B1","run_date":"2026-06-09T22:02:43","timeline":{"discoveries":[{"year":2013,"finding":"AP-5 forms a stoichiometric (~1:1:1:1:1:1) complex with SPG11 and SPG15, co-immunoprecipitated from both cytosol and detergent-extracted membranes. Knockdowns of SPG11 or SPG15 phenocopy knockdowns of AP-5 subunits, all causing the cation-independent mannose 6-phosphate receptor (CIMPR) to become trapped in clusters of early endosomes. AP-5, SPG11, and SPG15 colocalize on a late endosomal/lysosomal compartment. The N-terminal β-propeller-like domain of SPG11 interacts in vitro with AP-5.","method":"Co-immunoprecipitation, siRNA knockdown with immunolocalization phenotype, in vitro pull-down, subcellular fractionation","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, genetic epistasis via parallel knockdowns, in vitro pull-down, and localization data across multiple orthogonal methods in one study","pmids":["23825025"],"is_preprint":false},{"year":2018,"finding":"AP-5 functions in a late endosome-to-Golgi retrieval pathway. CRISPR-Cas9 knockout of AP5Z1 in HeLa cells leads to impaired retrieval of CIMPR, GOLIM4, and GOLM1 from endosomes back to the Golgi. The retromer complex shows altered steady-state distribution in AP-5 KO cells, and retromer knockdown exacerbates the AP-5 KO phenotype, placing AP-5 as a backup pathway for retromer. Both CIMPR and sortilin interact with the AP-5-associated protein SPG15 in pull-down assays.","method":"CRISPR-Cas9 knockout, subcellular fractionation profiling with quantitative mass spectrometry, immunolocalization, pull-down assays, siRNA knockdown epistasis","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — CRISPR KO with quantitative proteomics, immunolocalization, pull-down, and genetic epistasis with retromer knockdown; multiple orthogonal methods in one study","pmids":["29381698"],"is_preprint":false},{"year":2015,"finding":"Loss of AP-5 ζ protein (and reduction of AP-5 µ5) in patient-derived fibroblasts causes accumulation of abundant multilamellar endolysosomal structures filled with aberrant storage material (multilamellar whorls, striated belts, fingerprint bodies). This phenotype is replicated by siRNA knockdown of AP-5 ζ in HeLa cells, defining AP-5 deficiency as a new type of lysosomal storage disease.","method":"Patient-derived fibroblast characterization, ultrastructural analysis (electron microscopy), siRNA knockdown in HeLa cells, immunoblotting","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function in both patient cells and cell culture model with defined ultrastructural phenotype; replicated across three independent patient lines plus HeLa knockdown","pmids":["26085577"],"is_preprint":false},{"year":2021,"finding":"Recruitment of the AP-5/SPG11/SPG15 complex to late endosomes/lysosomes requires coincidence detection of phosphatidylinositol 3-phosphate (PI3P) and Rag GTPases. PI3P binding is mediated by the SPG15 FYVE domain. GDP-locked RagC promotes recruitment of the complex, while GTP-locked RagA prevents its recruitment. Recruitment is enhanced in starved cells, revealing interplay between AP-5/SPG11/SPG15 and the mTORC1 pathway.","method":"Live-cell imaging and immunolocalization with PI3P manipulation, dominant-negative/constitutively active Rag GTPase expression, starvation experiments, membrane recruitment assays","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal approaches (PI3P manipulation, Rag GTPase mutants, starvation) with direct localization readouts in a single focused study","pmids":["33464297"],"is_preprint":false},{"year":2016,"finding":"HIV-2 Gag particle release is dependent on AP-5 (and AP-3), but not AP-1 or AP-2, whereas HIV-1 Gag release requires AP-1 and AP-3 but not AP-5. This differential requirement demonstrates that AP-5 participates in an intracellular trafficking pathway used by HIV-2 Gag.","method":"siRNA knockdown of individual AP complexes combined with HIV-2/HIV-1 particle release assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — clean siRNA knockdown with defined viral particle release phenotype, but single lab and limited to a viral cargo context","pmids":["27392064"],"is_preprint":false},{"year":2025,"finding":"Bi-allelic loss-of-function variants in AP5B1 (encoding the β subunit of the AP-5 complex) cause recessive inherited macular dystrophy. Immunostaining of retinal pigment epithelium (RPE) cells shows a punctate pattern of AP5B1 staining co-localizing with markers of late endosomes and the Golgi, supporting a role for AP-5 in RPE lysosomal/endosomal homeostasis.","method":"Human genetics (whole-genome/exome sequencing), immunostaining with co-localization of late endosome and Golgi markers in RPE cells","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — human genetic evidence replicated across 19 families in 9 countries plus direct immunolocalization in RPE, but functional cellular mechanism inferred from co-localization rather than direct mechanistic assay","pmids":["40081374"],"is_preprint":false},{"year":2012,"finding":"AP-5 is an evolutionarily ancient heterotetrameric adaptor protein complex associated with endosomal dynamics. Its deficiency (mutations in AP5Z1) causes hereditary spastic paraplegia, implicating AP-5 in neuronal endosomal trafficking and homeostasis.","method":"Review synthesizing biochemical identification of the complex and human genetic studies","journal":"Traffic (Copenhagen, Denmark)","confidence":"Low","confidence_rationale":"Tier 4 / Moderate — review article summarizing prior findings without new primary mechanistic experiments; included only for the summary of AP-5 complex identity and disease association","pmids":["23167973"],"is_preprint":false}],"current_model":"AP5B1 encodes the β subunit of the AP-5 heterotetrameric adaptor protein complex, which assembles with SPG11 and SPG15 in a ~1:1:1:1:1:1 stoichiometry to form a coat-like complex on late endosomes/lysosomes; this complex is recruited by coincidence detection of PI3P (via the SPG15 FYVE domain) and Rag GTPases in an mTORC1-linked, starvation-enhanced manner, and functions in a retromer-backup pathway mediating retrieval of cargoes (including CIMPR, GOLIM4, GOLM1) from late endosomes to the Golgi—loss of AP-5 causes accumulation of aberrant multilamellar endolysosomes resembling lysosomal storage disease, and bi-allelic variants in AP5B1 specifically cause recessive macular degeneration associated with disrupted RPE lysosomal homeostasis."},"narrative":{"mechanistic_narrative":"AP5B1 encodes the β subunit of AP-5, an evolutionarily ancient heterotetrameric adaptor protein complex that assembles in a stoichiometric (~1:1:1:1:1:1) complex with SPG11 and SPG15 on late endosomes/lysosomes and mediates retrieval of cargoes back to the Golgi [PMID:23825025]. AP-5 functions as a backup to the retromer pathway: CRISPR knockout of an AP-5 subunit impairs retrieval of CIMPR, GOLIM4, and GOLM1 from endosomes to the Golgi, the phenotype is exacerbated by retromer knockdown, and CIMPR and sortilin bind the AP-5-associated protein SPG15 [PMID:29381698]. Recruitment of the AP-5/SPG11/SPG15 complex to late endosomes/lysosomes requires coincidence detection of PI3P (via the SPG15 FYVE domain) and Rag GTPases, with GDP-locked RagC promoting and GTP-locked RagA preventing recruitment, and is enhanced upon starvation, linking the complex to the mTORC1 pathway [PMID:33464297]. Loss of AP-5 function produces accumulation of aberrant multilamellar endolysosomal storage structures, defining AP-5 deficiency as a lysosomal storage disorder [PMID:26085577]. Bi-allelic loss-of-function variants in AP5B1 cause recessive inherited macular dystrophy, with AP5B1 localizing to puncta marked by late endosome and Golgi markers in retinal pigment epithelium [PMID:40081374].","teleology":[{"year":2013,"claim":"Established that AP-5 is not a free-standing adaptor but a stable partner of SPG11 and SPG15 acting in endosomal cargo sorting, answering what molecular assembly AP-5 belongs to and where it acts.","evidence":"Reciprocal co-immunoprecipitation, parallel siRNA knockdowns with CIMPR localization readout, in vitro pull-down, and subcellular fractionation","pmids":["23825025"],"confidence":"High","gaps":["Did not define the directionality of the sorting step or the destination compartment","Specific contribution of the β subunit (AP5B1) versus other subunits not dissected","No structural model of the assembled complex"]},{"year":2015,"claim":"Connected AP-5 loss to a defined cellular pathology, showing that AP-5 deficiency produces multilamellar endolysosomal storage and constitutes a lysosomal storage disease.","evidence":"Patient-derived fibroblast ultrastructural analysis by electron microscopy plus siRNA knockdown in HeLa cells","pmids":["26085577"],"confidence":"High","gaps":["The molecular cargo whose mistrafficking drives storage accumulation was not identified","Did not establish the trafficking step disrupted upstream of storage"]},{"year":2016,"claim":"Demonstrated that AP-5 serves a specific intracellular trafficking route exploited by HIV-2 Gag, distinguishing it from AP-1/AP-2/AP-3 requirements.","evidence":"siRNA knockdown of individual AP complexes with HIV-1/HIV-2 particle release assays","pmids":["27392064"],"confidence":"Medium","gaps":["Single-lab result limited to a viral cargo context","The host trafficking step and direct cargo interaction were not defined"]},{"year":2018,"claim":"Defined the directionality and pathway context of AP-5, showing it mediates late endosome-to-Golgi retrieval of specific cargoes and acts as a backup to retromer.","evidence":"CRISPR-Cas9 knockout with quantitative mass spectrometry fractionation profiling, immunolocalization, pull-down, and retromer knockdown epistasis","pmids":["29381698"],"confidence":"High","gaps":["Cargo recognition was attributed to SPG15 rather than to AP5B1 directly","How AP-5 is mechanistically coordinated with retromer was not resolved"]},{"year":2021,"claim":"Resolved how the AP-5/SPG11/SPG15 complex is recruited to membranes, identifying PI3P and Rag GTPase coincidence detection as the targeting mechanism and linking it to mTORC1/nutrient status.","evidence":"Live-cell imaging with PI3P manipulation, dominant-negative/constitutively active Rag GTPase mutants, and starvation experiments","pmids":["33464297"],"confidence":"High","gaps":["The physical Rag GTPase contact surface on the complex was not mapped","The role of the β subunit in recruitment versus the SPG15 FYVE domain was not separated"]},{"year":2025,"claim":"Tied AP5B1 directly to human disease, showing bi-allelic loss-of-function variants cause recessive macular dystrophy and implicating AP-5 in RPE endolysosomal homeostasis.","evidence":"Whole-genome/exome sequencing across families plus immunostaining co-localizing AP5B1 with late endosome and Golgi markers in RPE cells","pmids":["40081374"],"confidence":"Medium","gaps":["Cellular mechanism inferred from co-localization rather than direct functional assay in RPE","Why AP5B1 loss manifests in the macula specifically is unexplained"]},{"year":null,"claim":"How AP5B1 itself contributes to cargo selection, complex assembly, and membrane deformation within the AP-5 coat remains undefined.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structure of the assembled AP-5 coat or the β subunit","Direct cargo-binding role of AP5B1 versus SPG15 not established","Mechanism linking endosome-to-Golgi retrieval failure to macular versus neuronal phenotypes unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1]}],"localization":[{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[0,1,3,5]},{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[2,3]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[1,5]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[1]}],"complexes":["AP-5 adaptor complex","AP-5/SPG11/SPG15 complex"],"partners":["SPG11","SPG15","AP5Z1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q2VPB7","full_name":"AP-5 complex subunit beta-1","aliases":["Adaptor-related protein complex 5 beta subunit","Beta5"],"length_aa":878,"mass_kda":93.9,"function":"As part of AP-5, a probable fifth adaptor protein complex it may be involved in endosomal transport","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q2VPB7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/AP5B1","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/AP5B1","total_profiled":1310},"omim":[{"mim_id":"614824","title":"ADAPTOR-RELATED PROTEIN COMPLEX 5, SIGMA-1 SUBUNIT; AP5S1","url":"https://www.omim.org/entry/614824"},{"mim_id":"614367","title":"ADAPTOR-RELATED PROTEIN COMPLEX 5, BETA-1 SUBUNIT; AP5B1","url":"https://www.omim.org/entry/614367"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Vesicles","reliability":"Approved"},{"location":"Golgi apparatus","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"bone marrow","ntpm":41.5}],"url":"https://www.proteinatlas.org/search/AP5B1"},"hgnc":{"alias_symbol":["PP1030","AP-5","DKFZp761E198"],"prev_symbol":[]},"alphafold":{"accession":"Q2VPB7","domains":[{"cath_id":"-","chopping":"551-632","consensus_level":"medium","plddt":81.2422,"start":551,"end":632},{"cath_id":"2.60.40.1230","chopping":"653-765","consensus_level":"high","plddt":85.198,"start":653,"end":765},{"cath_id":"3.30.310.10","chopping":"768-878","consensus_level":"high","plddt":83.9074,"start":768,"end":878},{"cath_id":"1.10.1240","chopping":"308-381","consensus_level":"medium","plddt":84.0778,"start":308,"end":381},{"cath_id":"1.20.1310","chopping":"398-427_436-498","consensus_level":"medium","plddt":85.6676,"start":398,"end":498}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q2VPB7","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q2VPB7-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q2VPB7-F1-predicted_aligned_error_v6.png","plddt_mean":79.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=AP5B1","jax_strain_url":"https://www.jax.org/strain/search?query=AP5B1"},"sequence":{"accession":"Q2VPB7","fasta_url":"https://rest.uniprot.org/uniprotkb/Q2VPB7.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q2VPB7/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q2VPB7"}},"corpus_meta":[{"pmid":"2876450","id":"PMC_2876450","title":"Intrastriatal 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Knockdowns of SPG11 or SPG15 phenocopy knockdowns of AP-5 subunits, all causing the cation-independent mannose 6-phosphate receptor (CIMPR) to become trapped in clusters of early endosomes. AP-5, SPG11, and SPG15 colocalize on a late endosomal/lysosomal compartment. The N-terminal β-propeller-like domain of SPG11 interacts in vitro with AP-5.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown with immunolocalization phenotype, in vitro pull-down, subcellular fractionation\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, genetic epistasis via parallel knockdowns, in vitro pull-down, and localization data across multiple orthogonal methods in one study\",\n      \"pmids\": [\"23825025\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"AP-5 functions in a late endosome-to-Golgi retrieval pathway. CRISPR-Cas9 knockout of AP5Z1 in HeLa cells leads to impaired retrieval of CIMPR, GOLIM4, and GOLM1 from endosomes back to the Golgi. The retromer complex shows altered steady-state distribution in AP-5 KO cells, and retromer knockdown exacerbates the AP-5 KO phenotype, placing AP-5 as a backup pathway for retromer. Both CIMPR and sortilin interact with the AP-5-associated protein SPG15 in pull-down assays.\",\n      \"method\": \"CRISPR-Cas9 knockout, subcellular fractionation profiling with quantitative mass spectrometry, immunolocalization, pull-down assays, siRNA knockdown epistasis\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — CRISPR KO with quantitative proteomics, immunolocalization, pull-down, and genetic epistasis with retromer knockdown; multiple orthogonal methods in one study\",\n      \"pmids\": [\"29381698\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Loss of AP-5 ζ protein (and reduction of AP-5 µ5) in patient-derived fibroblasts causes accumulation of abundant multilamellar endolysosomal structures filled with aberrant storage material (multilamellar whorls, striated belts, fingerprint bodies). This phenotype is replicated by siRNA knockdown of AP-5 ζ in HeLa cells, defining AP-5 deficiency as a new type of lysosomal storage disease.\",\n      \"method\": \"Patient-derived fibroblast characterization, ultrastructural analysis (electron microscopy), siRNA knockdown in HeLa cells, immunoblotting\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function in both patient cells and cell culture model with defined ultrastructural phenotype; replicated across three independent patient lines plus HeLa knockdown\",\n      \"pmids\": [\"26085577\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Recruitment of the AP-5/SPG11/SPG15 complex to late endosomes/lysosomes requires coincidence detection of phosphatidylinositol 3-phosphate (PI3P) and Rag GTPases. PI3P binding is mediated by the SPG15 FYVE domain. GDP-locked RagC promotes recruitment of the complex, while GTP-locked RagA prevents its recruitment. Recruitment is enhanced in starved cells, revealing interplay between AP-5/SPG11/SPG15 and the mTORC1 pathway.\",\n      \"method\": \"Live-cell imaging and immunolocalization with PI3P manipulation, dominant-negative/constitutively active Rag GTPase expression, starvation experiments, membrane recruitment assays\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal approaches (PI3P manipulation, Rag GTPase mutants, starvation) with direct localization readouts in a single focused study\",\n      \"pmids\": [\"33464297\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"HIV-2 Gag particle release is dependent on AP-5 (and AP-3), but not AP-1 or AP-2, whereas HIV-1 Gag release requires AP-1 and AP-3 but not AP-5. This differential requirement demonstrates that AP-5 participates in an intracellular trafficking pathway used by HIV-2 Gag.\",\n      \"method\": \"siRNA knockdown of individual AP complexes combined with HIV-2/HIV-1 particle release assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — clean siRNA knockdown with defined viral particle release phenotype, but single lab and limited to a viral cargo context\",\n      \"pmids\": [\"27392064\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Bi-allelic loss-of-function variants in AP5B1 (encoding the β subunit of the AP-5 complex) cause recessive inherited macular dystrophy. Immunostaining of retinal pigment epithelium (RPE) cells shows a punctate pattern of AP5B1 staining co-localizing with markers of late endosomes and the Golgi, supporting a role for AP-5 in RPE lysosomal/endosomal homeostasis.\",\n      \"method\": \"Human genetics (whole-genome/exome sequencing), immunostaining with co-localization of late endosome and Golgi markers in RPE cells\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — human genetic evidence replicated across 19 families in 9 countries plus direct immunolocalization in RPE, but functional cellular mechanism inferred from co-localization rather than direct mechanistic assay\",\n      \"pmids\": [\"40081374\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"AP-5 is an evolutionarily ancient heterotetrameric adaptor protein complex associated with endosomal dynamics. Its deficiency (mutations in AP5Z1) causes hereditary spastic paraplegia, implicating AP-5 in neuronal endosomal trafficking and homeostasis.\",\n      \"method\": \"Review synthesizing biochemical identification of the complex and human genetic studies\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Moderate — review article summarizing prior findings without new primary mechanistic experiments; included only for the summary of AP-5 complex identity and disease association\",\n      \"pmids\": [\"23167973\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"AP5B1 encodes the β subunit of the AP-5 heterotetrameric adaptor protein complex, which assembles with SPG11 and SPG15 in a ~1:1:1:1:1:1 stoichiometry to form a coat-like complex on late endosomes/lysosomes; this complex is recruited by coincidence detection of PI3P (via the SPG15 FYVE domain) and Rag GTPases in an mTORC1-linked, starvation-enhanced manner, and functions in a retromer-backup pathway mediating retrieval of cargoes (including CIMPR, GOLIM4, GOLM1) from late endosomes to the Golgi—loss of AP-5 causes accumulation of aberrant multilamellar endolysosomes resembling lysosomal storage disease, and bi-allelic variants in AP5B1 specifically cause recessive macular degeneration associated with disrupted RPE lysosomal homeostasis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"AP5B1 encodes the β subunit of AP-5, an evolutionarily ancient heterotetrameric adaptor protein complex that assembles in a stoichiometric (~1:1:1:1:1:1) complex with SPG11 and SPG15 on late endosomes/lysosomes and mediates retrieval of cargoes back to the Golgi [#0]. AP-5 functions as a backup to the retromer pathway: CRISPR knockout of an AP-5 subunit impairs retrieval of CIMPR, GOLIM4, and GOLM1 from endosomes to the Golgi, the phenotype is exacerbated by retromer knockdown, and CIMPR and sortilin bind the AP-5-associated protein SPG15 [#1]. Recruitment of the AP-5/SPG11/SPG15 complex to late endosomes/lysosomes requires coincidence detection of PI3P (via the SPG15 FYVE domain) and Rag GTPases, with GDP-locked RagC promoting and GTP-locked RagA preventing recruitment, and is enhanced upon starvation, linking the complex to the mTORC1 pathway [#3]. Loss of AP-5 function produces accumulation of aberrant multilamellar endolysosomal storage structures, defining AP-5 deficiency as a lysosomal storage disorder [#2]. Bi-allelic loss-of-function variants in AP5B1 cause recessive inherited macular dystrophy, with AP5B1 localizing to puncta marked by late endosome and Golgi markers in retinal pigment epithelium [#5].\",\n  \"teleology\": [\n    {\n      \"year\": 2013,\n      \"claim\": \"Established that AP-5 is not a free-standing adaptor but a stable partner of SPG11 and SPG15 acting in endosomal cargo sorting, answering what molecular assembly AP-5 belongs to and where it acts.\",\n      \"evidence\": \"Reciprocal co-immunoprecipitation, parallel siRNA knockdowns with CIMPR localization readout, in vitro pull-down, and subcellular fractionation\",\n      \"pmids\": [\"23825025\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the directionality of the sorting step or the destination compartment\", \"Specific contribution of the β subunit (AP5B1) versus other subunits not dissected\", \"No structural model of the assembled complex\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Connected AP-5 loss to a defined cellular pathology, showing that AP-5 deficiency produces multilamellar endolysosomal storage and constitutes a lysosomal storage disease.\",\n      \"evidence\": \"Patient-derived fibroblast ultrastructural analysis by electron microscopy plus siRNA knockdown in HeLa cells\",\n      \"pmids\": [\"26085577\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The molecular cargo whose mistrafficking drives storage accumulation was not identified\", \"Did not establish the trafficking step disrupted upstream of storage\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstrated that AP-5 serves a specific intracellular trafficking route exploited by HIV-2 Gag, distinguishing it from AP-1/AP-2/AP-3 requirements.\",\n      \"evidence\": \"siRNA knockdown of individual AP complexes with HIV-1/HIV-2 particle release assays\",\n      \"pmids\": [\"27392064\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab result limited to a viral cargo context\", \"The host trafficking step and direct cargo interaction were not defined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Defined the directionality and pathway context of AP-5, showing it mediates late endosome-to-Golgi retrieval of specific cargoes and acts as a backup to retromer.\",\n      \"evidence\": \"CRISPR-Cas9 knockout with quantitative mass spectrometry fractionation profiling, immunolocalization, pull-down, and retromer knockdown epistasis\",\n      \"pmids\": [\"29381698\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cargo recognition was attributed to SPG15 rather than to AP5B1 directly\", \"How AP-5 is mechanistically coordinated with retromer was not resolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Resolved how the AP-5/SPG11/SPG15 complex is recruited to membranes, identifying PI3P and Rag GTPase coincidence detection as the targeting mechanism and linking it to mTORC1/nutrient status.\",\n      \"evidence\": \"Live-cell imaging with PI3P manipulation, dominant-negative/constitutively active Rag GTPase mutants, and starvation experiments\",\n      \"pmids\": [\"33464297\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The physical Rag GTPase contact surface on the complex was not mapped\", \"The role of the β subunit in recruitment versus the SPG15 FYVE domain was not separated\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Tied AP5B1 directly to human disease, showing bi-allelic loss-of-function variants cause recessive macular dystrophy and implicating AP-5 in RPE endolysosomal homeostasis.\",\n      \"evidence\": \"Whole-genome/exome sequencing across families plus immunostaining co-localizing AP5B1 with late endosome and Golgi markers in RPE cells\",\n      \"pmids\": [\"40081374\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cellular mechanism inferred from co-localization rather than direct functional assay in RPE\", \"Why AP5B1 loss manifests in the macula specifically is unexplained\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How AP5B1 itself contributes to cargo selection, complex assembly, and membrane deformation within the AP-5 coat remains undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structure of the assembled AP-5 coat or the β subunit\", \"Direct cargo-binding role of AP5B1 versus SPG15 not established\", \"Mechanism linking endosome-to-Golgi retrieval failure to macular versus neuronal phenotypes unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [0, 1, 3, 5]},\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [1, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"complexes\": [\"AP-5 adaptor complex\", \"AP-5/SPG11/SPG15 complex\"],\n    \"partners\": [\"SPG11\", \"SPG15\", \"AP5Z1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}