{"gene":"HPS6","run_date":"2026-06-10T01:55:22","timeline":{"discoveries":[{"year":2004,"finding":"HPS6 is a subunit of the stable ~340 kDa BLOC-2 (Biogenesis of Lysosome-related Organelles Complex-2) protein complex, together with HPS3 and HPS5. The endogenous proteins co-immunoprecipitate from HeLa cell extracts and co-fractionate by size-exclusion chromatography and density gradient centrifugation. HPS6 (and BLOC-2) exists in both a soluble pool and as a peripheral membrane protein.","method":"Co-immunoprecipitation from HeLa cell extracts, size-exclusion chromatography, density gradient centrifugation","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP combined with two independent fractionation methods; foundational biochemical characterization paper replicated in subsequent studies","pmids":["15030569"],"is_preprint":false},{"year":2004,"finding":"Fibroblasts deficient in BLOC-2 subunit HPS6 display normal basal secretion of the lysosomal enzyme beta-hexosaminidase, indicating BLOC-2/HPS6 is not required for constitutive lysosomal enzyme secretion.","method":"Beta-hexosaminidase secretion assay in HPS6-deficient fibroblasts","journal":"Traffic (Copenhagen, Denmark)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined cellular phenotype (negative result) in loss-of-function cells, single lab with direct functional assay","pmids":["15030569"],"is_preprint":false},{"year":2014,"finding":"HPS6 directly interacts with the dynactin p150Glued subunit and acts as a cargo adaptor for the dynein-dynactin retrograde motor complex to mediate centripetal transport of lysosomes from the cell periphery to the perinuclear region. siRNA knockdown of HPS6 partially blocks centripetal lysosome movement, impairs lysosomal acidification and degradative capacity, delays lysosome-mediated protein degradation, and impairs fusion between late endosomes/multivesicular bodies and lysosomes.","method":"Co-immunoprecipitation (HPS6–p150Glued interaction), siRNA knockdown in HeLa cells with live-cell imaging of lysosome positioning, lysosomal degradation assays, acidification assays, and late endosome–lysosome fusion assays","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct binding demonstrated by Co-IP, loss-of-function knockdown with multiple orthogonal functional readouts in a single focused study","pmids":["25189619"],"is_preprint":false},{"year":2016,"finding":"HPS6 deficiency in mouse endothelial cells impairs VWF tubulation within Weibel-Palade bodies (WPBs) and reduces regulated VWF release into plasma after desmopressin stimulation, indicating that the BLOC-2 subunit HPS6 is required for proper WPB maturation and VWF tubule formation.","method":"HPS6-deficient mouse model; plasma VWF measurement after DDAVP stimulation; electron microscopy and immunofluorescence of WPBs","journal":"Journal of genetics and genomics = Yi chuan xue bao","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function mouse model with multiple orthogonal readouts (VWF plasma levels, WPB morphology), single lab","pmids":["27889498"],"is_preprint":false},{"year":2022,"finding":"HPS6 interacts with ATP6V0D1 (a subunit of v-ATPase) and is required for trafficking v-ATPase to the WPB limiting membrane. HPS6 knockdown in HUVECs causes misshapen WPBs, decreased WPB number, and impaired VWF tubulation—phenotypes that are recapitulated by ATP6V0D1 knockdown. The model is that HPS6-mediated v-ATPase delivery maintains the acidic luminal pH required for VWF tubule formation during WPB biogenesis.","method":"Co-immunoprecipitation (HPS6–ATP6V0D1 interaction), siRNA knockdown of HPS6 or ATP6V0D1 in HUVECs, electron/fluorescence microscopy of WPB morphology and VWF tubulation","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding by Co-IP plus parallel loss-of-function phenocopy experiment, single lab, two orthogonal methods","pmids":["35252216"],"is_preprint":false}],"current_model":"HPS6 is a subunit of the peripheral membrane protein complex BLOC-2 (with HPS3 and HPS5) that functions in the biogenesis of lysosome-related organelles; it additionally acts as a cargo adaptor linking lysosomes to the dynein-dynactin (p150Glued) retrograde motor for perinuclear positioning required for lysosome maturation and acidification, and facilitates trafficking of the v-ATPase subunit ATP6V0D1 to Weibel-Palade body membranes to maintain luminal acidity necessary for VWF tubulation."},"narrative":{"mechanistic_narrative":"HPS6 is a subunit of the stable BLOC-2 complex (with HPS3 and HPS5) that functions in the biogenesis and maturation of lysosome-related organelles, existing as both a soluble pool and a peripheral membrane protein [PMID:15030569]. Beyond its structural role in BLOC-2, HPS6 acts as a cargo adaptor that directly binds the dynactin p150Glued subunit to couple lysosomes to the dynein-dynactin retrograde motor, driving their centripetal transport to the perinuclear region; loss of HPS6 impairs lysosomal acidification, degradative capacity, and late endosome–lysosome fusion [PMID:25189619]. In endothelial cells, HPS6 is required for Weibel-Palade body maturation and von Willebrand factor (VWF) tubulation, in part by binding the v-ATPase subunit ATP6V0D1 and delivering v-ATPase to the WPB limiting membrane to maintain the acidic luminal pH needed for VWF tubule formation [PMID:27889498, PMID:35252216]. HPS6/BLOC-2 is not required for constitutive lysosomal enzyme secretion [PMID:15030569].","teleology":[{"year":2004,"claim":"Established HPS6 as a defined biochemical entity by showing it is a stable subunit of the BLOC-2 complex, framing all later function within the biogenesis of lysosome-related organelles.","evidence":"Reciprocal Co-IP from HeLa extracts plus size-exclusion chromatography and density gradient fractionation","pmids":["15030569"],"confidence":"High","gaps":["Stoichiometry and subunit architecture of BLOC-2 not resolved","Membrane-recruitment mechanism for the peripheral pool not defined"]},{"year":2004,"claim":"Tested whether BLOC-2 governs bulk lysosomal secretion and showed it does not, narrowing HPS6 function to organelle biogenesis rather than constitutive enzyme release.","evidence":"Beta-hexosaminidase secretion assay in HPS6-deficient fibroblasts (negative result)","pmids":["15030569"],"confidence":"Medium","gaps":["A negative result does not exclude roles in regulated secretion","Single assay/single lab"]},{"year":2014,"claim":"Defined a direct mechanistic role by identifying HPS6 as a cargo adaptor linking lysosomes to the dynein-dynactin motor, explaining how lysosome positioning is coupled to maturation and acidification.","evidence":"Co-IP of HPS6 with p150Glued plus siRNA knockdown in HeLa cells with live-cell imaging, acidification, degradation, and fusion assays","pmids":["25189619"],"confidence":"High","gaps":["Whether this adaptor activity requires intact BLOC-2 is unclear","Binding interface on p150Glued not mapped","Knockdown only partially blocks transport, implying redundancy"]},{"year":2016,"claim":"Extended HPS6 function to endothelial Weibel-Palade bodies, showing it is required for WPB maturation and VWF tubulation and thus regulated VWF release.","evidence":"HPS6-deficient mouse model; plasma VWF after DDAVP; EM and immunofluorescence of WPBs","pmids":["27889498"],"confidence":"Medium","gaps":["Molecular mechanism behind the tubulation defect not defined in this study","Single lab"]},{"year":2022,"claim":"Provided the molecular basis for the WPB phenotype by showing HPS6 binds ATP6V0D1 and delivers v-ATPase to the WPB membrane to maintain acidic luminal pH required for VWF tubulation.","evidence":"Co-IP of HPS6 with ATP6V0D1 plus parallel siRNA phenocopy of HPS6 and ATP6V0D1 in HUVECs with WPB/VWF imaging","pmids":["35252216"],"confidence":"Medium","gaps":["Direct demonstration of luminal pH change upon HPS6 loss not shown","Whether trafficking is BLOC-2-dependent or adaptor-dependent unresolved","Single lab, two methods"]},{"year":null,"claim":"How HPS6's BLOC-2 membership, dynein-dynactin adaptor activity, and v-ATPase trafficking roles are mechanistically integrated remains unresolved.","evidence":"No single study connects these functions","pmids":[],"confidence":"Medium","gaps":["No structural model of HPS6 or its binding interfaces","Unclear whether cargo-adaptor and v-ATPase functions require intact BLOC-2","No defined recruitment signal for the peripheral membrane pool"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[2]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[2]}],"localization":[{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[2]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[3,4]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[2]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[3,4]}],"complexes":["BLOC-2"],"partners":["HPS3","HPS5","DCTN1","ATP6V0D1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q86YV9","full_name":"BLOC-2 complex member HPS6","aliases":["Hermansky-Pudlak syndrome 6 protein","Ruby-eye protein homolog","Ru"],"length_aa":775,"mass_kda":83.0,"function":"May regulate the synthesis and function of lysosomes and of highly specialized organelles, such as melanosomes and platelet dense granules (PubMed:17041891). Acts as a cargo adapter for the dynein-dynactin motor complex to mediate the transport of lysosomes from the cell periphery to the perinuclear region. Facilitates retrograde lysosomal trafficking by linking the motor complex to lysosomes, and perinuclear positioning of lysosomes is crucial for the delivery of endocytic cargos to lysosomes, for lysosome maturation and functioning (PubMed:25189619)","subcellular_location":"Microsome membrane; Cytoplasm, cytosol; Early endosome membrane; Lysosome membrane","url":"https://www.uniprot.org/uniprotkb/Q86YV9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/HPS6","classification":"Not Classified","n_dependent_lines":4,"n_total_lines":1208,"dependency_fraction":0.0033112582781456954},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/HPS6","total_profiled":1310},"omim":[{"mim_id":"614075","title":"HERMANSKY-PUDLAK SYNDROME 6; HPS6","url":"https://www.omim.org/entry/614075"},{"mim_id":"607522","title":"HPS6 BIOGENESIS OF LYSOSOMAL ORGANELLES COMPLEX 2, SUBUNIT 3; HPS6","url":"https://www.omim.org/entry/607522"},{"mim_id":"607521","title":"HPS5 BIOGENESIS OF LYSOSOMAL ORGANELLES COMPLEX 2, SUBUNIT 2; HPS5","url":"https://www.omim.org/entry/607521"},{"mim_id":"607145","title":"DYSTROBREVIN-BINDING PROTEIN 1; DTNBP1","url":"https://www.omim.org/entry/607145"},{"mim_id":"203300","title":"HERMANSKY-PUDLAK SYNDROME 1; HPS1","url":"https://www.omim.org/entry/203300"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"},{"location":"Vesicles","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/HPS6"},"hgnc":{"alias_symbol":["FLJ22501","BLOC2S3"],"prev_symbol":[]},"alphafold":{"accession":"Q86YV9","domains":[{"cath_id":"-","chopping":"14-120","consensus_level":"medium","plddt":83.9334,"start":14,"end":120},{"cath_id":"-","chopping":"127-262","consensus_level":"medium","plddt":79.5176,"start":127,"end":262},{"cath_id":"2.40.10.480","chopping":"270-350_384-390","consensus_level":"medium","plddt":86.0267,"start":270,"end":390},{"cath_id":"-","chopping":"400-444","consensus_level":"high","plddt":75.6253,"start":400,"end":444},{"cath_id":"-","chopping":"652-713_733-744","consensus_level":"medium","plddt":82.8324,"start":652,"end":744}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q86YV9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q86YV9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q86YV9-F1-predicted_aligned_error_v6.png","plddt_mean":77.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=HPS6","jax_strain_url":"https://www.jax.org/strain/search?query=HPS6"},"sequence":{"accession":"Q86YV9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q86YV9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q86YV9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q86YV9"}},"corpus_meta":[{"pmid":"15030569","id":"PMC_15030569","title":"Characterization of BLOC-2, a complex containing the Hermansky-Pudlak syndrome proteins HPS3, HPS5 and HPS6.","date":"2004","source":"Traffic (Copenhagen, Denmark)","url":"https://pubmed.ncbi.nlm.nih.gov/15030569","citation_count":87,"is_preprint":false},{"pmid":"25189619","id":"PMC_25189619","title":"HPS6 interacts with dynactin p150Glued to mediate retrograde trafficking and maturation of lysosomes.","date":"2014","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/25189619","citation_count":31,"is_preprint":false},{"pmid":"27889498","id":"PMC_27889498","title":"BLOC-2 subunit HPS6 deficiency affects the tubulation and secretion of von Willebrand factor from mouse endothelial cells.","date":"2016","source":"Journal of genetics and genomics = Yi chuan xue bao","url":"https://pubmed.ncbi.nlm.nih.gov/27889498","citation_count":22,"is_preprint":false},{"pmid":"35252216","id":"PMC_35252216","title":"HPS6 Regulates the Biogenesis of Weibel-Palade Body in Endothelial Cells Through Trafficking v-ATPase to Its Limiting Membrane.","date":"2022","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/35252216","citation_count":14,"is_preprint":false},{"pmid":"27917594","id":"PMC_27917594","title":"A novel two-nucleotide deletion in HPS6 affects mepacrine uptake and platelet dense granule secretion in a family with Hermansky-Pudlak syndrome.","date":"2016","source":"Pediatric blood & cancer","url":"https://pubmed.ncbi.nlm.nih.gov/27917594","citation_count":12,"is_preprint":false},{"pmid":"27225848","id":"PMC_27225848","title":"Novel HPS6 mutations identified by whole-exome sequencing in two Japanese sisters with suspected ocular albinism.","date":"2016","source":"Journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/27225848","citation_count":11,"is_preprint":false},{"pmid":"27641950","id":"PMC_27641950","title":"Identification of a novel mutation in HPS6 in a patient with hemophilia B and oculocutaneous albinism.","date":"2016","source":"Molecular genetics and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/27641950","citation_count":8,"is_preprint":false},{"pmid":"30369044","id":"PMC_30369044","title":"Severe bleeding with subclinical oculocutaneous albinism in a patient with a novel HPS6 missense variant.","date":"2018","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/30369044","citation_count":7,"is_preprint":false},{"pmid":"33878481","id":"PMC_33878481","title":"Hermansky-Pudlak syndrome: Five Chinese patients with novel variants in HPS1 and HPS6.","date":"2021","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/33878481","citation_count":3,"is_preprint":false},{"pmid":"38091959","id":"PMC_38091959","title":"Novel Variants of HPS6 Cause Suspected Ocular Albinism: A Report of 2 Cases and the Profile of HPS6 Variants.","date":"2023","source":"Ophthalmic research","url":"https://pubmed.ncbi.nlm.nih.gov/38091959","citation_count":2,"is_preprint":false},{"pmid":"35054407","id":"PMC_35054407","title":"Two Novel Homozygous HPS6 Mutations (Double Mutant) Identified by Whole-Exome Sequencing in a Saudi Consanguineous Family Suspected for Oculocutaneous Albinism.","date":"2021","source":"Life (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/35054407","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7789,"output_tokens":1494,"usd":0.022888,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8233,"output_tokens":2139,"usd":0.04732,"stage2_stop_reason":"end_turn"},"total_usd":0.070208,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2004,\n      \"finding\": \"HPS6 is a subunit of the stable ~340 kDa BLOC-2 (Biogenesis of Lysosome-related Organelles Complex-2) protein complex, together with HPS3 and HPS5. The endogenous proteins co-immunoprecipitate from HeLa cell extracts and co-fractionate by size-exclusion chromatography and density gradient centrifugation. HPS6 (and BLOC-2) exists in both a soluble pool and as a peripheral membrane protein.\",\n      \"method\": \"Co-immunoprecipitation from HeLa cell extracts, size-exclusion chromatography, density gradient centrifugation\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP combined with two independent fractionation methods; foundational biochemical characterization paper replicated in subsequent studies\",\n      \"pmids\": [\"15030569\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Fibroblasts deficient in BLOC-2 subunit HPS6 display normal basal secretion of the lysosomal enzyme beta-hexosaminidase, indicating BLOC-2/HPS6 is not required for constitutive lysosomal enzyme secretion.\",\n      \"method\": \"Beta-hexosaminidase secretion assay in HPS6-deficient fibroblasts\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined cellular phenotype (negative result) in loss-of-function cells, single lab with direct functional assay\",\n      \"pmids\": [\"15030569\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"HPS6 directly interacts with the dynactin p150Glued subunit and acts as a cargo adaptor for the dynein-dynactin retrograde motor complex to mediate centripetal transport of lysosomes from the cell periphery to the perinuclear region. siRNA knockdown of HPS6 partially blocks centripetal lysosome movement, impairs lysosomal acidification and degradative capacity, delays lysosome-mediated protein degradation, and impairs fusion between late endosomes/multivesicular bodies and lysosomes.\",\n      \"method\": \"Co-immunoprecipitation (HPS6–p150Glued interaction), siRNA knockdown in HeLa cells with live-cell imaging of lysosome positioning, lysosomal degradation assays, acidification assays, and late endosome–lysosome fusion assays\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding demonstrated by Co-IP, loss-of-function knockdown with multiple orthogonal functional readouts in a single focused study\",\n      \"pmids\": [\"25189619\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"HPS6 deficiency in mouse endothelial cells impairs VWF tubulation within Weibel-Palade bodies (WPBs) and reduces regulated VWF release into plasma after desmopressin stimulation, indicating that the BLOC-2 subunit HPS6 is required for proper WPB maturation and VWF tubule formation.\",\n      \"method\": \"HPS6-deficient mouse model; plasma VWF measurement after DDAVP stimulation; electron microscopy and immunofluorescence of WPBs\",\n      \"journal\": \"Journal of genetics and genomics = Yi chuan xue bao\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function mouse model with multiple orthogonal readouts (VWF plasma levels, WPB morphology), single lab\",\n      \"pmids\": [\"27889498\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"HPS6 interacts with ATP6V0D1 (a subunit of v-ATPase) and is required for trafficking v-ATPase to the WPB limiting membrane. HPS6 knockdown in HUVECs causes misshapen WPBs, decreased WPB number, and impaired VWF tubulation—phenotypes that are recapitulated by ATP6V0D1 knockdown. The model is that HPS6-mediated v-ATPase delivery maintains the acidic luminal pH required for VWF tubule formation during WPB biogenesis.\",\n      \"method\": \"Co-immunoprecipitation (HPS6–ATP6V0D1 interaction), siRNA knockdown of HPS6 or ATP6V0D1 in HUVECs, electron/fluorescence microscopy of WPB morphology and VWF tubulation\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding by Co-IP plus parallel loss-of-function phenocopy experiment, single lab, two orthogonal methods\",\n      \"pmids\": [\"35252216\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"HPS6 is a subunit of the peripheral membrane protein complex BLOC-2 (with HPS3 and HPS5) that functions in the biogenesis of lysosome-related organelles; it additionally acts as a cargo adaptor linking lysosomes to the dynein-dynactin (p150Glued) retrograde motor for perinuclear positioning required for lysosome maturation and acidification, and facilitates trafficking of the v-ATPase subunit ATP6V0D1 to Weibel-Palade body membranes to maintain luminal acidity necessary for VWF tubulation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"HPS6 is a subunit of the stable BLOC-2 complex (with HPS3 and HPS5) that functions in the biogenesis and maturation of lysosome-related organelles, existing as both a soluble pool and a peripheral membrane protein [#0]. Beyond its structural role in BLOC-2, HPS6 acts as a cargo adaptor that directly binds the dynactin p150Glued subunit to couple lysosomes to the dynein-dynactin retrograde motor, driving their centripetal transport to the perinuclear region; loss of HPS6 impairs lysosomal acidification, degradative capacity, and late endosome\\u2013lysosome fusion [#2]. In endothelial cells, HPS6 is required for Weibel-Palade body maturation and von Willebrand factor (VWF) tubulation, in part by binding the v-ATPase subunit ATP6V0D1 and delivering v-ATPase to the WPB limiting membrane to maintain the acidic luminal pH needed for VWF tubule formation [#3, #4]. HPS6/BLOC-2 is not required for constitutive lysosomal enzyme secretion [#1].\"\n,\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Established HPS6 as a defined biochemical entity by showing it is a stable subunit of the BLOC-2 complex, framing all later function within the biogenesis of lysosome-related organelles.\",\n      \"evidence\": \"Reciprocal Co-IP from HeLa extracts plus size-exclusion chromatography and density gradient fractionation\",\n      \"pmids\": [\"15030569\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and subunit architecture of BLOC-2 not resolved\", \"Membrane-recruitment mechanism for the peripheral pool not defined\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Tested whether BLOC-2 governs bulk lysosomal secretion and showed it does not, narrowing HPS6 function to organelle biogenesis rather than constitutive enzyme release.\",\n      \"evidence\": \"Beta-hexosaminidase secretion assay in HPS6-deficient fibroblasts (negative result)\",\n      \"pmids\": [\"15030569\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"A negative result does not exclude roles in regulated secretion\", \"Single assay/single lab\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined a direct mechanistic role by identifying HPS6 as a cargo adaptor linking lysosomes to the dynein-dynactin motor, explaining how lysosome positioning is coupled to maturation and acidification.\",\n      \"evidence\": \"Co-IP of HPS6 with p150Glued plus siRNA knockdown in HeLa cells with live-cell imaging, acidification, degradation, and fusion assays\",\n      \"pmids\": [\"25189619\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether this adaptor activity requires intact BLOC-2 is unclear\", \"Binding interface on p150Glued not mapped\", \"Knockdown only partially blocks transport, implying redundancy\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Extended HPS6 function to endothelial Weibel-Palade bodies, showing it is required for WPB maturation and VWF tubulation and thus regulated VWF release.\",\n      \"evidence\": \"HPS6-deficient mouse model; plasma VWF after DDAVP; EM and immunofluorescence of WPBs\",\n      \"pmids\": [\"27889498\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism behind the tubulation defect not defined in this study\", \"Single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Provided the molecular basis for the WPB phenotype by showing HPS6 binds ATP6V0D1 and delivers v-ATPase to the WPB membrane to maintain acidic luminal pH required for VWF tubulation.\",\n      \"evidence\": \"Co-IP of HPS6 with ATP6V0D1 plus parallel siRNA phenocopy of HPS6 and ATP6V0D1 in HUVECs with WPB/VWF imaging\",\n      \"pmids\": [\"35252216\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct demonstration of luminal pH change upon HPS6 loss not shown\", \"Whether trafficking is BLOC-2-dependent or adaptor-dependent unresolved\", \"Single lab, two methods\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How HPS6's BLOC-2 membership, dynein-dynactin adaptor activity, and v-ATPase trafficking roles are mechanistically integrated remains unresolved.\",\n      \"evidence\": \"No single study connects these functions\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of HPS6 or its binding interfaces\", \"Unclear whether cargo-adaptor and v-ATPase functions require intact BLOC-2\", \"No defined recruitment signal for the peripheral membrane pool\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [3, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [3, 4]}\n    ],\n    \"complexes\": [\"BLOC-2\"],\n    \"partners\": [\"HPS3\", \"HPS5\", \"DCTN1\", \"ATP6V0D1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":4,"faith_pct":100.0}}