{"gene":"PHETA1","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":2011,"finding":"PHETA1 (IPIP27A) binds to the C-terminal region of OCRL1 and the related 5-phosphatase INPP5B via a conserved motif similar to that found in APPL1; PHETA1 forms homo- and heterodimers with IPIP27B (PHETA2) and localizes to early and recycling endosomes and the trans-Golgi network (TGN); PHETA1 is required for receptor recycling from endosomes both to the TGN and to the plasma membrane.","method":"Co-immunoprecipitation, subcellular localization (imaging), knockdown with receptor recycling assay","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, direct localization, functional knockdown with defined trafficking phenotype, replicated across multiple experimental approaches in one study and subsequently confirmed by independent labs","pmids":["21233288"],"is_preprint":false},{"year":2015,"finding":"PHETA1 (IPIP27A) mediates interaction between OCRL1 and the F-BAR protein pacsin 2; PHETA1-mediated engagement of OCRL1 with pacsin 2 stimulates OCRL1 5-phosphatase activity (which is membrane-curvature sensitive) and promotes scission of mannose 6-phosphate receptor (MPR)-containing carriers; loss of PHETA1 leads to defective MPR carrier biogenesis at the TGN and endosomes.","method":"Co-immunoprecipitation, in vitro 5-phosphatase activity assay, knockdown with trafficking intermediate biogenesis readout, localization (imaging)","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro enzymatic assay plus Co-IP plus loss-of-function with specific trafficking phenotype, multiple orthogonal methods in single study","pmids":["26510499"],"is_preprint":false},{"year":2019,"finding":"In cultured podocytes, PHETA1 (IPIP27A) associates with OCRL1 and with CD2AP, a protein important for maintenance of the podocyte slit diaphragm, placing PHETA1 in a complex relevant to glomerular function.","method":"Co-immunoprecipitation / co-association assay in cultured podocytes","journal":"Pediatric nephrology (Berlin, Germany)","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP in one cell type, single lab, no functional rescue or mutagenesis","pmids":["31811534"],"is_preprint":false},{"year":2019,"finding":"In Dictyostelium discoideum, the OCRL orthologue Dd5P4 binds proteins closely related to IPIP27A/B (Ses1/2) via F&H peptide motifs; these endocytic adaptors function together with Dd5P4 to control membrane deformation at multiple endocytic stations and during fluid-phase micropinocytosis, and OCRL/Dd5P4 also acts at the contractile vacuole; F&H proteins (including the PHETA1/2 homologs) are proposed as key modifiers of Lowe syndrome phenotypes.","method":"Genetic knockout, co-depletion epistasis, live imaging of endocytic compartments in Dictyostelium","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis and live imaging in a model organism with conserved F&H motif binding, single lab but multiple orthogonal approaches","pmids":["31216233"],"is_preprint":false},{"year":2020,"finding":"In vivo loss-of-function of pheta1 and pheta2 in zebrafish disrupts endocytosis and ciliogenesis in renal tissues, and causes reduced jaw size with delayed chondrocyte differentiation; PHETA1/2 deficiency dysregulates cathepsin K, leading to increased type II collagen abundance (immature ECM marker) in craniofacial cartilage; cathepsin K inhibition rescues the craniofacial phenotype; the patient-derived R6C variant of PHETA1, when expressed in zebrafish, exacerbates craniofacial deficits in a dominant-negative manner.","method":"Zebrafish knockout/morphant, live imaging of endocytosis, immunostaining, cathepsin K inhibitor rescue, patient variant overexpression","journal":"Disease models & mechanisms","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic loss-of-function with multiple orthogonal phenotypic readouts, pharmacological rescue, and disease-variant functional validation in a single rigorous study","pmids":["32152089"],"is_preprint":false},{"year":2022,"finding":"Knockout of Ipip27A (PHETA1) in zebrafish phenocopies loss of OCRL in the proximal renal tubule: both fluid-phase and protein cargo uptake are reduced, megalin abundance is decreased, and endosome morphology is altered; rescue and co-depletion experiments establish that Ipip27A functions together with OCRL to support proximal tubule endocytosis.","method":"Zebrafish knockout, endocytic cargo uptake assays, immunostaining, epistasis co-depletion and rescue experiments","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic KO with multiple cargo uptake assays, epistasis (co-depletion and rescue), independent replication of earlier cell-biology findings in a model organism","pmids":["34673953"],"is_preprint":false}],"current_model":"PHETA1 (IPIP27A/FAM109A) is an endocytic adaptor protein that binds OCRL1 (and INPP5B) via a conserved F&H motif and forms homo/heterodimers with PHETA2; it localizes to early/recycling endosomes and the TGN, where it bridges OCRL1 to the F-BAR protein pacsin 2 to stimulate OCRL1 5-phosphatase activity and drive scission of MPR-containing trafficking intermediates; in vivo, PHETA1 is required for megalin-dependent endocytosis in the renal proximal tubule and for craniofacial chondrocyte maturation (via regulation of cathepsin K), and a patient-derived dominant-negative variant (R6C) exacerbates these phenotypes."},"narrative":{"mechanistic_narrative":"PHETA1 (IPIP27A/FAM109A) is an endocytic adaptor that couples the inositol 5-phosphatase OCRL1 to membrane-remodeling machinery to drive cargo trafficking through endosomes and the trans-Golgi network [PMID:21233288, PMID:26510499]. It binds the C-terminal region of OCRL1 and the related phosphatase INPP5B through a conserved F&H-type motif, self-associates into homo- and heterodimers with PHETA2 (IPIP27B), and localizes to early and recycling endosomes and the TGN, where it is required for receptor recycling [PMID:21233288]. Mechanistically, PHETA1 bridges OCRL1 to the F-BAR protein pacsin 2, stimulating the curvature-sensitive 5-phosphatase activity of OCRL1 and promoting scission of mannose 6-phosphate receptor-containing carriers; its loss blocks biogenesis of these trafficking intermediates [PMID:26510499]. In vivo, PHETA1 acts together with OCRL to support megalin-dependent proximal tubule endocytosis [PMID:34673953] and is required for craniofacial chondrocyte maturation, where it restrains cathepsin K activity, and the patient-derived R6C variant exacerbates these phenotypes in a dominant-negative manner [PMID:32152089].","teleology":[{"year":2011,"claim":"Established PHETA1 as an OCRL1/INPP5B-binding adaptor by defining its physical partners, oligomeric state, compartmental localization, and a functional requirement in receptor recycling.","evidence":"Co-IP, imaging, and knockdown receptor recycling assays in cultured cells","pmids":["21233288"],"confidence":"High","gaps":["Did not define the enzymatic consequence of binding OCRL1","Did not identify membrane-remodeling effectors"]},{"year":2015,"claim":"Answered how PHETA1 acts mechanistically by showing it bridges OCRL1 to pacsin 2, stimulating OCRL1 5-phosphatase activity and enabling scission of MPR carriers.","evidence":"Co-IP, in vitro 5-phosphatase assay, and loss-of-function trafficking biogenesis readouts","pmids":["26510499"],"confidence":"High","gaps":["Structural basis of the OCRL1-PHETA1-pacsin 2 assembly not resolved","In vivo relevance not yet tested"]},{"year":2019,"claim":"Linked PHETA1 to glomerular biology by detecting association with OCRL1 and the slit-diaphragm protein CD2AP in podocytes.","evidence":"Co-IP/co-association in cultured podocytes","pmids":["31811534"],"confidence":"Low","gaps":["Single Co-IP in one cell type without reciprocal validation","No functional rescue or mutagenesis","Functional consequence for slit-diaphragm maintenance untested"]},{"year":2019,"claim":"Demonstrated evolutionary conservation of the adaptor-phosphatase module, showing F&H-motif binding of IPIP27 orthologs to the OCRL ortholog Dd5P4 controls membrane deformation across endocytic stations.","evidence":"Genetic knockout, co-depletion epistasis, and live imaging in Dictyostelium","pmids":["31216233"],"confidence":"Medium","gaps":["Conservation inferred from a model organism","Direct mapping to mammalian PHETA1 functions not established in this study"]},{"year":2020,"claim":"Provided in vivo and disease-relevant function, showing PHETA1/2 loss disrupts renal endocytosis and ciliogenesis and impairs chondrocyte maturation via cathepsin K dysregulation, with the R6C patient variant acting dominant-negatively.","evidence":"Zebrafish knockout/morphant, imaging, cathepsin K inhibitor rescue, and patient-variant overexpression","pmids":["32152089"],"confidence":"High","gaps":["Molecular link between PHETA1 trafficking role and cathepsin K regulation not defined","Mechanism of R6C dominant-negative action unresolved"]},{"year":2022,"claim":"Placed PHETA1 directly in the OCRL pathway in the proximal tubule by phenocopying OCRL loss for fluid-phase and cargo uptake, megalin abundance, and endosome morphology, with epistasis confirming co-function.","evidence":"Zebrafish knockout, cargo uptake assays, immunostaining, and co-depletion/rescue epistasis","pmids":["34673953"],"confidence":"High","gaps":["Mechanism by which PHETA1 loss reduces megalin abundance unresolved","Mammalian proximal tubule confirmation not addressed"]},{"year":null,"claim":"How PHETA1 trafficking function mechanistically connects to its tissue-specific outputs (cathepsin K regulation, megalin stability, slit-diaphragm maintenance) and the structural basis of dominant-negative variants remain open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of the OCRL1-PHETA1-pacsin 2 complex","Causal chain from endosomal scission defects to ECM/cathepsin K phenotypes undefined","Human disease causation rests on a single patient variant"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1]}],"localization":[{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[0]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[0]}],"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":[0,5]}],"complexes":[],"partners":["OCRL","INPP5B","PHETA2","PACSIN2","CD2AP"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8N4B1","full_name":"Sesquipedalian-1","aliases":["27 kDa inositol polyphosphate phosphatase-interacting protein A","IPIP27A","PH domain-containing endocytic trafficking adaptor 1"],"length_aa":249,"mass_kda":27.2,"function":"Plays a role in endocytic trafficking. Required for receptor recycling from endosomes, both to the trans-Golgi network and the plasma membrane","subcellular_location":"Early endosome; Recycling endosome; Golgi apparatus, trans-Golgi network; Cytoplasmic vesicle, clathrin-coated vesicle","url":"https://www.uniprot.org/uniprotkb/Q8N4B1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PHETA1","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"OCRL","stoichiometry":10.0}],"url":"https://opencell.sf.czbiohub.org/search/PHETA1","total_profiled":1310},"omim":[{"mim_id":"615275","title":"ACONITATE DECARBOXYLASE 1; ACOD1","url":"https://www.omim.org/entry/615275"},{"mim_id":"614240","title":"PH DOMAIN-CONTAINING ENDOCYTIC TRAFFICKING ADAPTOR 2; PHETA2","url":"https://www.omim.org/entry/614240"},{"mim_id":"614239","title":"PH DOMAIN-CONTAINING ENDOCYTIC TRAFFICKING ADAPTOR 1; PHETA1","url":"https://www.omim.org/entry/614239"},{"mim_id":"608102","title":"CLN5 INTRACELLULAR TRAFFICKING PROTEIN; CLN5","url":"https://www.omim.org/entry/608102"},{"mim_id":"256731","title":"CEROID LIPOFUSCINOSIS, NEURONAL, 5; CLN5","url":"https://www.omim.org/entry/256731"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"intestine","ntpm":23.3}],"url":"https://www.proteinatlas.org/search/PHETA1"},"hgnc":{"alias_symbol":["FLJ32356","SES1","IPIP27A"],"prev_symbol":["FAM109A"]},"alphafold":{"accession":"Q8N4B1","domains":[{"cath_id":"2.30.29.30","chopping":"6-116","consensus_level":"high","plddt":92.6187,"start":6,"end":116}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8N4B1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8N4B1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8N4B1-F1-predicted_aligned_error_v6.png","plddt_mean":75.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PHETA1","jax_strain_url":"https://www.jax.org/strain/search?query=PHETA1"},"sequence":{"accession":"Q8N4B1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8N4B1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8N4B1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8N4B1"}},"corpus_meta":[{"pmid":"17239033","id":"PMC_17239033","title":"Molecular genetics of bipolar disorder and depression.","date":"2007","source":"Psychiatry and clinical neurosciences","url":"https://pubmed.ncbi.nlm.nih.gov/17239033","citation_count":214,"is_preprint":false},{"pmid":"21233288","id":"PMC_21233288","title":"The PH domain proteins IPIP27A and B link OCRL1 to receptor recycling in the endocytic pathway.","date":"2011","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/21233288","citation_count":59,"is_preprint":false},{"pmid":"26510499","id":"PMC_26510499","title":"OCRL1 engages with the F-BAR protein pacsin 2 to promote biogenesis of membrane-trafficking intermediates.","date":"2015","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/26510499","citation_count":26,"is_preprint":false},{"pmid":"15389760","id":"PMC_15389760","title":"Linkage disequilibrium mapping of bipolar affective disorder at 12q23-q24 provides evidence for association at CUX2 and FLJ32356.","date":"2005","source":"American journal of medical genetics. Part B, Neuropsychiatric genetics : the official publication of the International Society of Psychiatric Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/15389760","citation_count":22,"is_preprint":false},{"pmid":"31811534","id":"PMC_31811534","title":"A role for OCRL in glomerular function and disease.","date":"2019","source":"Pediatric nephrology (Berlin, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/31811534","citation_count":15,"is_preprint":false},{"pmid":"34868271","id":"PMC_34868271","title":"Comprehensive Transcriptomic Profiling of Murine Osteoclast Differentiation Reveals Novel Differentially Expressed Genes and LncRNAs.","date":"2021","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/34868271","citation_count":14,"is_preprint":false},{"pmid":"32152089","id":"PMC_32152089","title":"Deficiency in the endocytic adaptor proteins PHETA1/2 impairs renal and craniofacial development.","date":"2020","source":"Disease models & mechanisms","url":"https://pubmed.ncbi.nlm.nih.gov/32152089","citation_count":7,"is_preprint":false},{"pmid":"34673953","id":"PMC_34673953","title":"IPIP27A cooperates with OCRL to support endocytic traffic in the zebrafish pronephric tubule.","date":"2022","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/34673953","citation_count":4,"is_preprint":false},{"pmid":"31216233","id":"PMC_31216233","title":"Lowe syndrome-linked endocytic adaptors direct membrane cycling kinetics with OCRL in Dictyostelium discoideum.","date":"2019","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/31216233","citation_count":3,"is_preprint":false},{"pmid":"30193228","id":"PMC_30193228","title":"Modeling, dynamics and phosphoinositide binding of the pleckstrin homology domain of two novel PLCs: η1 and η2.","date":"2018","source":"Journal of molecular graphics & modelling","url":"https://pubmed.ncbi.nlm.nih.gov/30193228","citation_count":2,"is_preprint":false},{"pmid":"41328997","id":"PMC_41328997","title":"Exploring the Shared Genetic Architectures Between Primary Open-Angle Glaucoma and Visual Pathway Regions in the Brain.","date":"2025","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/41328997","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7721,"output_tokens":1819,"usd":0.025224,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8652,"output_tokens":2343,"usd":0.050917,"stage2_stop_reason":"end_turn"},"total_usd":0.076141,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2011,\n      \"finding\": \"PHETA1 (IPIP27A) binds to the C-terminal region of OCRL1 and the related 5-phosphatase INPP5B via a conserved motif similar to that found in APPL1; PHETA1 forms homo- and heterodimers with IPIP27B (PHETA2) and localizes to early and recycling endosomes and the trans-Golgi network (TGN); PHETA1 is required for receptor recycling from endosomes both to the TGN and to the plasma membrane.\",\n      \"method\": \"Co-immunoprecipitation, subcellular localization (imaging), knockdown with receptor recycling assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, direct localization, functional knockdown with defined trafficking phenotype, replicated across multiple experimental approaches in one study and subsequently confirmed by independent labs\",\n      \"pmids\": [\"21233288\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PHETA1 (IPIP27A) mediates interaction between OCRL1 and the F-BAR protein pacsin 2; PHETA1-mediated engagement of OCRL1 with pacsin 2 stimulates OCRL1 5-phosphatase activity (which is membrane-curvature sensitive) and promotes scission of mannose 6-phosphate receptor (MPR)-containing carriers; loss of PHETA1 leads to defective MPR carrier biogenesis at the TGN and endosomes.\",\n      \"method\": \"Co-immunoprecipitation, in vitro 5-phosphatase activity assay, knockdown with trafficking intermediate biogenesis readout, localization (imaging)\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro enzymatic assay plus Co-IP plus loss-of-function with specific trafficking phenotype, multiple orthogonal methods in single study\",\n      \"pmids\": [\"26510499\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In cultured podocytes, PHETA1 (IPIP27A) associates with OCRL1 and with CD2AP, a protein important for maintenance of the podocyte slit diaphragm, placing PHETA1 in a complex relevant to glomerular function.\",\n      \"method\": \"Co-immunoprecipitation / co-association assay in cultured podocytes\",\n      \"journal\": \"Pediatric nephrology (Berlin, Germany)\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP in one cell type, single lab, no functional rescue or mutagenesis\",\n      \"pmids\": [\"31811534\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In Dictyostelium discoideum, the OCRL orthologue Dd5P4 binds proteins closely related to IPIP27A/B (Ses1/2) via F&H peptide motifs; these endocytic adaptors function together with Dd5P4 to control membrane deformation at multiple endocytic stations and during fluid-phase micropinocytosis, and OCRL/Dd5P4 also acts at the contractile vacuole; F&H proteins (including the PHETA1/2 homologs) are proposed as key modifiers of Lowe syndrome phenotypes.\",\n      \"method\": \"Genetic knockout, co-depletion epistasis, live imaging of endocytic compartments in Dictyostelium\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis and live imaging in a model organism with conserved F&H motif binding, single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"31216233\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In vivo loss-of-function of pheta1 and pheta2 in zebrafish disrupts endocytosis and ciliogenesis in renal tissues, and causes reduced jaw size with delayed chondrocyte differentiation; PHETA1/2 deficiency dysregulates cathepsin K, leading to increased type II collagen abundance (immature ECM marker) in craniofacial cartilage; cathepsin K inhibition rescues the craniofacial phenotype; the patient-derived R6C variant of PHETA1, when expressed in zebrafish, exacerbates craniofacial deficits in a dominant-negative manner.\",\n      \"method\": \"Zebrafish knockout/morphant, live imaging of endocytosis, immunostaining, cathepsin K inhibitor rescue, patient variant overexpression\",\n      \"journal\": \"Disease models & mechanisms\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic loss-of-function with multiple orthogonal phenotypic readouts, pharmacological rescue, and disease-variant functional validation in a single rigorous study\",\n      \"pmids\": [\"32152089\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Knockout of Ipip27A (PHETA1) in zebrafish phenocopies loss of OCRL in the proximal renal tubule: both fluid-phase and protein cargo uptake are reduced, megalin abundance is decreased, and endosome morphology is altered; rescue and co-depletion experiments establish that Ipip27A functions together with OCRL to support proximal tubule endocytosis.\",\n      \"method\": \"Zebrafish knockout, endocytic cargo uptake assays, immunostaining, epistasis co-depletion and rescue experiments\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic KO with multiple cargo uptake assays, epistasis (co-depletion and rescue), independent replication of earlier cell-biology findings in a model organism\",\n      \"pmids\": [\"34673953\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PHETA1 (IPIP27A/FAM109A) is an endocytic adaptor protein that binds OCRL1 (and INPP5B) via a conserved F&H motif and forms homo/heterodimers with PHETA2; it localizes to early/recycling endosomes and the TGN, where it bridges OCRL1 to the F-BAR protein pacsin 2 to stimulate OCRL1 5-phosphatase activity and drive scission of MPR-containing trafficking intermediates; in vivo, PHETA1 is required for megalin-dependent endocytosis in the renal proximal tubule and for craniofacial chondrocyte maturation (via regulation of cathepsin K), and a patient-derived dominant-negative variant (R6C) exacerbates these phenotypes.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PHETA1 (IPIP27A/FAM109A) is an endocytic adaptor that couples the inositol 5-phosphatase OCRL1 to membrane-remodeling machinery to drive cargo trafficking through endosomes and the trans-Golgi network [#0, #1]. It binds the C-terminal region of OCRL1 and the related phosphatase INPP5B through a conserved F&H-type motif, self-associates into homo- and heterodimers with PHETA2 (IPIP27B), and localizes to early and recycling endosomes and the TGN, where it is required for receptor recycling [#0]. Mechanistically, PHETA1 bridges OCRL1 to the F-BAR protein pacsin 2, stimulating the curvature-sensitive 5-phosphatase activity of OCRL1 and promoting scission of mannose 6-phosphate receptor-containing carriers; its loss blocks biogenesis of these trafficking intermediates [#1]. In vivo, PHETA1 acts together with OCRL to support megalin-dependent proximal tubule endocytosis [#5] and is required for craniofacial chondrocyte maturation, where it restrains cathepsin K activity, and the patient-derived R6C variant exacerbates these phenotypes in a dominant-negative manner [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 2011,\n      \"claim\": \"Established PHETA1 as an OCRL1/INPP5B-binding adaptor by defining its physical partners, oligomeric state, compartmental localization, and a functional requirement in receptor recycling.\",\n      \"evidence\": \"Co-IP, imaging, and knockdown receptor recycling assays in cultured cells\",\n      \"pmids\": [\"21233288\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the enzymatic consequence of binding OCRL1\", \"Did not identify membrane-remodeling effectors\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Answered how PHETA1 acts mechanistically by showing it bridges OCRL1 to pacsin 2, stimulating OCRL1 5-phosphatase activity and enabling scission of MPR carriers.\",\n      \"evidence\": \"Co-IP, in vitro 5-phosphatase assay, and loss-of-function trafficking biogenesis readouts\",\n      \"pmids\": [\"26510499\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the OCRL1-PHETA1-pacsin 2 assembly not resolved\", \"In vivo relevance not yet tested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Linked PHETA1 to glomerular biology by detecting association with OCRL1 and the slit-diaphragm protein CD2AP in podocytes.\",\n      \"evidence\": \"Co-IP/co-association in cultured podocytes\",\n      \"pmids\": [\"31811534\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single Co-IP in one cell type without reciprocal validation\", \"No functional rescue or mutagenesis\", \"Functional consequence for slit-diaphragm maintenance untested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstrated evolutionary conservation of the adaptor-phosphatase module, showing F&H-motif binding of IPIP27 orthologs to the OCRL ortholog Dd5P4 controls membrane deformation across endocytic stations.\",\n      \"evidence\": \"Genetic knockout, co-depletion epistasis, and live imaging in Dictyostelium\",\n      \"pmids\": [\"31216233\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Conservation inferred from a model organism\", \"Direct mapping to mammalian PHETA1 functions not established in this study\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Provided in vivo and disease-relevant function, showing PHETA1/2 loss disrupts renal endocytosis and ciliogenesis and impairs chondrocyte maturation via cathepsin K dysregulation, with the R6C patient variant acting dominant-negatively.\",\n      \"evidence\": \"Zebrafish knockout/morphant, imaging, cathepsin K inhibitor rescue, and patient-variant overexpression\",\n      \"pmids\": [\"32152089\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link between PHETA1 trafficking role and cathepsin K regulation not defined\", \"Mechanism of R6C dominant-negative action unresolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Placed PHETA1 directly in the OCRL pathway in the proximal tubule by phenocopying OCRL loss for fluid-phase and cargo uptake, megalin abundance, and endosome morphology, with epistasis confirming co-function.\",\n      \"evidence\": \"Zebrafish knockout, cargo uptake assays, immunostaining, and co-depletion/rescue epistasis\",\n      \"pmids\": [\"34673953\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which PHETA1 loss reduces megalin abundance unresolved\", \"Mammalian proximal tubule confirmation not addressed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PHETA1 trafficking function mechanistically connects to its tissue-specific outputs (cathepsin K regulation, megalin stability, slit-diaphragm maintenance) and the structural basis of dominant-negative variants remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of the OCRL1-PHETA1-pacsin 2 complex\", \"Causal chain from endosomal scission defects to ECM/cathepsin K phenotypes undefined\", \"Human disease causation rests on a single patient variant\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [0, 5]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"OCRL\", \"INPP5B\", \"PHETA2\", \"PACSIN2\", \"CD2AP\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":4,"faith_pct":100.0}}