{"gene":"CCDC32","run_date":"2026-06-09T22:57:17","timeline":{"discoveries":[{"year":2021,"finding":"C15orf57 (CCDC32) encodes a protein that binds the AP2 complex, localizes to clathrin-coated pits, and enables efficient transferrin uptake, as demonstrated by co-essentiality profiling and functional validation.","method":"Co-essentiality profiling, functional validation (transferrin uptake assay, localization to clathrin-coated pits)","journal":"Nature genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-essentiality prediction validated by functional assay and localization, single lab, two orthogonal methods","pmids":["33859415"],"is_preprint":false},{"year":2020,"finding":"Loss of CCDC32 is required for normal cilia formation in zebrafish embryos and mammalian cell culture, indicating a role in ciliogenesis that contributes to the pathomechanism of the associated congenital syndrome.","method":"Zebrafish ccdc32 morpholino knockdown with cilia formation readout; mammalian cell culture loss-of-function","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function in two model systems (zebrafish and mammalian cells) with specific phenotypic readout, single lab","pmids":["32307552"],"is_preprint":false},{"year":2024,"finding":"CCDC32 acts as a chaperone that recognizes the AAGAB:α:σ2 complex during AP2 assembly, leading to formation of an α:σ2:CCDC32 ternary complex that serves as a template to sequentially recruit µ2 and β2 subunits of AP2, completing assembly with subsequent CCDC32 release. A disease-causing mutation disrupts this function.","method":"Biochemical reconstitution, co-immunoprecipitation, in vitro assembly assays, mutagenesis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution of AP2 assembly, mutagenesis of disease-causing variant, multiple orthogonal biochemical methods in single rigorous study","pmids":["39145939"],"is_preprint":false},{"year":2025,"finding":"CCDC32 interacts with the α-appendage domain (AD) of AP2 in vitro and with full-length AP2 complexes in cells; deletion of aa78-98 (a predicted α-helix) abrogates AP2 binding and CCDC32's function in clathrin-mediated endocytosis. siRNA-mediated knockdown of CCDC32 leads to accumulation of unstable flat clathrin assemblies, demonstrating a role in clathrin-coated pit stabilization and invagination.","method":"siRNA knockdown, quantitative live cell imaging, in vitro binding assay, deletion mutagenesis","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal binding assays in vitro and in cells, deletion mutagenesis, quantitative live imaging, independently reported in preprint and peer-reviewed publication","pmids":["38979322","41489497"],"is_preprint":false},{"year":2025,"finding":"CCDC32 interacts with the appendage domain of the AP-2 α subunit using the same binding site as canonical endocytic regulators plus a novel conserved pocket; CCDC32 contains cargo sorting motifs and binds AP-2 heterodimers at canonical cargo-binding sites; two amphipathic helices bind the α/σ2 heterodimer. In solution, CCDC32 prevents AP-2 complex assembly and actively disassembles AP-2 tetramers (inhibition requires amphipathic helices). PIP2-containing membranes relieve inhibition and stabilize final AP-2 assembly, acting as a molecular switch.","method":"In vitro reconstitution, cryo-EM structural analysis, integrative structural analysis, PIP2-membrane binding assays, AP-2 disassembly assays","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution, cryo-EM structure, multiple orthogonal biochemical assays, replicated across preprint and peer-reviewed publication","pmids":["40799577","42234739"],"is_preprint":false},{"year":2011,"finding":"CCDC32 was identified as a potential interactor of the C-terminal fragment of annexin A2 (A2IC) by yeast two-hybrid screening of a human monocyte cDNA library.","method":"Yeast two-hybrid screen","journal":"Acta pharmacologica Sinica","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single yeast two-hybrid result, not confirmed by orthogonal method, no functional follow-up","pmids":["21963895"],"is_preprint":false}],"current_model":"CCDC32 is a chaperone that functions in clathrin-mediated endocytosis by binding to the AP-2 adaptor complex: it acts downstream of AAGAB to template sequential recruitment of AP-2 subunits, interacts with the α-appendage domain and cargo-binding sites of AP-2, and—through amphipathic helices—actively inhibits AP-2 assembly in solution while PIP2-containing membranes act as a molecular switch to release this inhibition and enable deposition of active AP-2 complexes at the plasma membrane; additionally, CCDC32 is required for normal ciliogenesis, and loss-of-function mutations cause cardiofacioneurodevelopmental syndrome."},"narrative":{"mechanistic_narrative":"CCDC32 is an assembly chaperone for the heterotetrameric AP-2 adaptor complex and thereby a regulator of clathrin-mediated endocytosis [PMID:39145939, PMID:38979322, PMID:41489497]. It functions in the AP-2 biogenesis pathway downstream of AAGAB, recognizing the AAGAB:α:σ2 intermediate to form an α:σ2:CCDC32 ternary complex that templates sequential recruitment of the µ2 and β2 subunits, after which CCDC32 is released to yield the complete adaptor [PMID:39145939]. CCDC32 engages AP-2 through multiple contacts: a predicted α-helix (aa78–98) required for AP-2 binding and endocytic function, the α-appendage domain at sites shared with canonical endocytic regulators plus a novel conserved pocket, and cargo-binding sites engaged via its own cargo sorting motifs [PMID:38979322, PMID:41489497, PMID:40799577, PMID:42234739]. Two amphipathic helices bind the α/σ2 heterodimer and actively prevent AP-2 assembly—and disassemble AP-2 tetramers—in solution, an inhibition relieved by PIP2-containing membranes that act as a molecular switch to deposit assembled AP-2 at the plasma membrane; consistent with this role, loss of CCDC32 produces unstable flat clathrin assemblies and impairs coated-pit invagination and transferrin uptake [PMID:33859415, PMID:38979322, PMID:41489497, PMID:40799577, PMID:42234739]. CCDC32 is additionally required for normal ciliogenesis, and a disease-causing mutation that disrupts its AP-2 chaperone function underlies the associated congenital syndrome [PMID:32307552, PMID:39145939].","teleology":[{"year":2011,"claim":"Before any functional assignment, an unbiased interaction screen offered the first candidate binding partner for the uncharacterized CCDC32 protein.","evidence":"Yeast two-hybrid screen of a human monocyte cDNA library against an annexin A2 C-terminal fragment","pmids":["21963895"],"confidence":"Low","gaps":["Single yeast two-hybrid result not confirmed by an orthogonal method","No functional follow-up linking this interaction to a cellular role","Relationship of this interaction to the later-established endocytic function is unestablished"]},{"year":2020,"claim":"The question of what physiological process CCDC32 supports was first answered by showing it is required for cilia formation, connecting the gene to a congenital syndrome.","evidence":"Zebrafish morpholino knockdown with cilia readout plus mammalian cell loss-of-function","pmids":["32307552"],"confidence":"Medium","gaps":["Molecular mechanism by which CCDC32 supports ciliogenesis not defined","Relationship between the ciliary role and endocytic role not resolved","Morpholino-based knockdown not corroborated by genetic deletion"]},{"year":2021,"claim":"An unbiased genetic approach placed CCDC32 in the endocytic machinery, establishing AP-2 binding and a functional requirement for cargo uptake.","evidence":"Co-essentiality profiling validated by transferrin uptake assay and localization to clathrin-coated pits","pmids":["33859415"],"confidence":"Medium","gaps":["Did not define which AP-2 subunits or domains are contacted","Mechanism of action within the coated pit not addressed","Single lab, correlative localization"]},{"year":2024,"claim":"Reconstitution revealed CCDC32's mechanism as an AP-2 assembly chaperone acting downstream of AAGAB, explaining how disease mutations impair function.","evidence":"Biochemical reconstitution, co-immunoprecipitation, in vitro assembly assays, and disease-variant mutagenesis","pmids":["39145939"],"confidence":"High","gaps":["Structural basis of the ternary template not resolved at this stage","Trigger for CCDC32 release after assembly not defined","Link to the ciliary phenotype not addressed"]},{"year":2025,"claim":"Cell-based and structural studies mapped the AP-2 binding interfaces and showed CCDC32 stabilizes coated pits, while defining a PIP2-gated inhibitory mechanism.","evidence":"siRNA knockdown with live imaging, deletion mutagenesis, in vitro binding, cryo-EM, and PIP2-membrane and AP-2 disassembly assays","pmids":["38979322","41489497","40799577","42234739"],"confidence":"High","gaps":["How the membrane switch is coordinated with cargo loading in vivo not fully defined","Whether the cargo sorting motifs in CCDC32 engage physiological cargo unresolved","Quantitative kinetics of inhibition relief at native plasma membranes not established"]},{"year":null,"claim":"Whether CCDC32's ciliary requirement reflects its AP-2 chaperone activity or a distinct molecular function remains unresolved.","evidence":"No timeline study connects the ciliogenesis phenotype to the endocytic mechanism","pmids":[],"confidence":"Medium","gaps":["No mechanistic bridge between AP-2 assembly and ciliogenesis","No structural model of CCDC32 outside the AP-2-bound state","Tissue-specific requirements underlying the syndrome not defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0044183","term_label":"protein folding chaperone","supporting_discovery_ids":[2]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[4]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[4]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[2,3]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,4]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[0,3]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[0,3]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[2]}],"complexes":[],"partners":["AP2A1","AP2S1","AP2M1","AP2B1","AAGAB"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9BV29","full_name":"Coiled-coil domain-containing protein 32","aliases":[],"length_aa":185,"mass_kda":20.7,"function":"Regulates clathrin-mediated endocytsois of cargos such as transferrin probably through the association and modulation of adaptor protein complex 2 (AP-2) (PubMed:33859415). Has a role in ciliogenesis (By similarity). Required for proper cephalic and left/right axis development (PubMed:32307552)","subcellular_location":"Membrane, coated pit","url":"https://www.uniprot.org/uniprotkb/Q9BV29/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CCDC32","classification":"Not Classified","n_dependent_lines":40,"n_total_lines":1208,"dependency_fraction":0.033112582781456956},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"AP2S1","stoichiometry":10.0}],"url":"https://opencell.sf.czbiohub.org/search/CCDC32","total_profiled":1310},"omim":[{"mim_id":"619123","title":"CARDIOFACIONEURODEVELOPMENTAL SYNDROME; CFNDS","url":"https://www.omim.org/entry/619123"},{"mim_id":"618941","title":"COILED-COIL DOMAIN-CONTAINING PROTEIN 32; CCDC32","url":"https://www.omim.org/entry/618941"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Microtubules","reliability":"Additional"},{"location":"Primary cilium","reliability":"Additional"},{"location":"Centrosome","reliability":"Additional"},{"location":"Basal body","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/CCDC32"},"hgnc":{"alias_symbol":["MGC20481"],"prev_symbol":["C15orf57"]},"alphafold":{"accession":"Q9BV29","domains":[{"cath_id":"-","chopping":"75-121","consensus_level":"medium","plddt":89.5957,"start":75,"end":121}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BV29","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BV29-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BV29-F1-predicted_aligned_error_v6.png","plddt_mean":68.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CCDC32","jax_strain_url":"https://www.jax.org/strain/search?query=CCDC32"},"sequence":{"accession":"Q9BV29","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9BV29.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9BV29/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BV29"}},"corpus_meta":[{"pmid":"33859415","id":"PMC_33859415","title":"A genome-wide atlas of co-essential modules assigns function to uncharacterized genes.","date":"2021","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/33859415","citation_count":155,"is_preprint":false},{"pmid":"32307552","id":"PMC_32307552","title":"Loss of function mutations in CCDC32 cause a congenital syndrome characterized by craniofacial, cardiac and neurodevelopmental anomalies.","date":"2020","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32307552","citation_count":14,"is_preprint":false},{"pmid":"39145939","id":"PMC_39145939","title":"An AAGAB-to-CCDC32 handover mechanism controls the assembly of the AP2 adaptor complex.","date":"2024","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/39145939","citation_count":13,"is_preprint":false},{"pmid":"33172452","id":"PMC_33172452","title":"Genomic profile of MYCN non-amplified neuroblastoma and potential for immunotherapeutic strategies in neuroblastoma.","date":"2020","source":"BMC medical genomics","url":"https://pubmed.ncbi.nlm.nih.gov/33172452","citation_count":13,"is_preprint":false},{"pmid":"25499959","id":"PMC_25499959","title":"Identification of a novel gene fusion (BMX-ARHGAP) in gastric cardia adenocarcinoma.","date":"2014","source":"Diagnostic pathology","url":"https://pubmed.ncbi.nlm.nih.gov/25499959","citation_count":12,"is_preprint":false},{"pmid":"21963895","id":"PMC_21963895","title":"Yeast two-hybrid screening of proteins interacting with plasmin receptor subunit: C-terminal fragment of annexin A2.","date":"2011","source":"Acta pharmacologica Sinica","url":"https://pubmed.ncbi.nlm.nih.gov/21963895","citation_count":9,"is_preprint":false},{"pmid":"35451546","id":"PMC_35451546","title":"Cardiofacioneurodevelopmental syndrome: Report of a novel patient and expansion of the phenotype.","date":"2022","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/35451546","citation_count":8,"is_preprint":false},{"pmid":"35888078","id":"PMC_35888078","title":"NSD1 Mutations in Sotos Syndrome Induce Differential Expression of Long Noncoding RNAs, miR646 and Genes Controlling the G2/M Checkpoint.","date":"2022","source":"Life (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/35888078","citation_count":8,"is_preprint":false},{"pmid":"33231893","id":"PMC_33231893","title":"Statistical methods with exhaustive search in the identification of gene-gene interactions for colorectal cancer.","date":"2020","source":"Genetic epidemiology","url":"https://pubmed.ncbi.nlm.nih.gov/33231893","citation_count":4,"is_preprint":false},{"pmid":"40799577","id":"PMC_40799577","title":"CCDC32 collaborates with the membrane to assemble the AP-2 clathrin adaptor complex.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/40799577","citation_count":3,"is_preprint":false},{"pmid":"38979322","id":"PMC_38979322","title":"CCDC32 stabilizes clathrin-coated pits and drives their invagination.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/38979322","citation_count":2,"is_preprint":false},{"pmid":"41489497","id":"PMC_41489497","title":"CCDC32 stabilizes clathrin-coated pits and drives their invagination.","date":"2026","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/41489497","citation_count":2,"is_preprint":false},{"pmid":"35114952","id":"PMC_35114952","title":"PΨFinder: a practical tool for the identification and visualization of novel pseudogenes in DNA sequencing data.","date":"2022","source":"BMC bioinformatics","url":"https://pubmed.ncbi.nlm.nih.gov/35114952","citation_count":2,"is_preprint":false},{"pmid":"41639596","id":"PMC_41639596","title":"Two siblings with CCDC32-related cardiofacioneurodevelopmental syndrome diagnosed by clinical RNA-sequencing and review of literature.","date":"2026","source":"European journal of human genetics : EJHG","url":"https://pubmed.ncbi.nlm.nih.gov/41639596","citation_count":1,"is_preprint":false},{"pmid":"42234739","id":"PMC_42234739","title":"CCDC32 collaborates with the membrane to assemble the AP-2 clathrin adaptor complex.","date":"2026","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/42234739","citation_count":0,"is_preprint":false},{"pmid":"41661231","id":"PMC_41661231","title":"RNAseq-based meta-analyses revealed tumor suppressor-inducer fusion events in liver, oral, and ovarian cancer in the Indian population: a cancer cell surviving mechanism.","date":"2026","source":"Nucleosides, nucleotides & nucleic acids","url":"https://pubmed.ncbi.nlm.nih.gov/41661231","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9868,"output_tokens":1583,"usd":0.026675,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8384,"output_tokens":2394,"usd":0.050885,"stage2_stop_reason":"end_turn"},"total_usd":0.07756,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2021,\n      \"finding\": \"C15orf57 (CCDC32) encodes a protein that binds the AP2 complex, localizes to clathrin-coated pits, and enables efficient transferrin uptake, as demonstrated by co-essentiality profiling and functional validation.\",\n      \"method\": \"Co-essentiality profiling, functional validation (transferrin uptake assay, localization to clathrin-coated pits)\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-essentiality prediction validated by functional assay and localization, single lab, two orthogonal methods\",\n      \"pmids\": [\"33859415\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Loss of CCDC32 is required for normal cilia formation in zebrafish embryos and mammalian cell culture, indicating a role in ciliogenesis that contributes to the pathomechanism of the associated congenital syndrome.\",\n      \"method\": \"Zebrafish ccdc32 morpholino knockdown with cilia formation readout; mammalian cell culture loss-of-function\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function in two model systems (zebrafish and mammalian cells) with specific phenotypic readout, single lab\",\n      \"pmids\": [\"32307552\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CCDC32 acts as a chaperone that recognizes the AAGAB:α:σ2 complex during AP2 assembly, leading to formation of an α:σ2:CCDC32 ternary complex that serves as a template to sequentially recruit µ2 and β2 subunits of AP2, completing assembly with subsequent CCDC32 release. A disease-causing mutation disrupts this function.\",\n      \"method\": \"Biochemical reconstitution, co-immunoprecipitation, in vitro assembly assays, mutagenesis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution of AP2 assembly, mutagenesis of disease-causing variant, multiple orthogonal biochemical methods in single rigorous study\",\n      \"pmids\": [\"39145939\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CCDC32 interacts with the α-appendage domain (AD) of AP2 in vitro and with full-length AP2 complexes in cells; deletion of aa78-98 (a predicted α-helix) abrogates AP2 binding and CCDC32's function in clathrin-mediated endocytosis. siRNA-mediated knockdown of CCDC32 leads to accumulation of unstable flat clathrin assemblies, demonstrating a role in clathrin-coated pit stabilization and invagination.\",\n      \"method\": \"siRNA knockdown, quantitative live cell imaging, in vitro binding assay, deletion mutagenesis\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal binding assays in vitro and in cells, deletion mutagenesis, quantitative live imaging, independently reported in preprint and peer-reviewed publication\",\n      \"pmids\": [\"38979322\", \"41489497\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CCDC32 interacts with the appendage domain of the AP-2 α subunit using the same binding site as canonical endocytic regulators plus a novel conserved pocket; CCDC32 contains cargo sorting motifs and binds AP-2 heterodimers at canonical cargo-binding sites; two amphipathic helices bind the α/σ2 heterodimer. In solution, CCDC32 prevents AP-2 complex assembly and actively disassembles AP-2 tetramers (inhibition requires amphipathic helices). PIP2-containing membranes relieve inhibition and stabilize final AP-2 assembly, acting as a molecular switch.\",\n      \"method\": \"In vitro reconstitution, cryo-EM structural analysis, integrative structural analysis, PIP2-membrane binding assays, AP-2 disassembly assays\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution, cryo-EM structure, multiple orthogonal biochemical assays, replicated across preprint and peer-reviewed publication\",\n      \"pmids\": [\"40799577\", \"42234739\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"CCDC32 was identified as a potential interactor of the C-terminal fragment of annexin A2 (A2IC) by yeast two-hybrid screening of a human monocyte cDNA library.\",\n      \"method\": \"Yeast two-hybrid screen\",\n      \"journal\": \"Acta pharmacologica Sinica\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single yeast two-hybrid result, not confirmed by orthogonal method, no functional follow-up\",\n      \"pmids\": [\"21963895\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CCDC32 is a chaperone that functions in clathrin-mediated endocytosis by binding to the AP-2 adaptor complex: it acts downstream of AAGAB to template sequential recruitment of AP-2 subunits, interacts with the α-appendage domain and cargo-binding sites of AP-2, and—through amphipathic helices—actively inhibits AP-2 assembly in solution while PIP2-containing membranes act as a molecular switch to release this inhibition and enable deposition of active AP-2 complexes at the plasma membrane; additionally, CCDC32 is required for normal ciliogenesis, and loss-of-function mutations cause cardiofacioneurodevelopmental syndrome.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CCDC32 is an assembly chaperone for the heterotetrameric AP-2 adaptor complex and thereby a regulator of clathrin-mediated endocytosis [#2, #3]. It functions in the AP-2 biogenesis pathway downstream of AAGAB, recognizing the AAGAB:\\u03b1:\\u03c32 intermediate to form an \\u03b1:\\u03c32:CCDC32 ternary complex that templates sequential recruitment of the \\u00b52 and \\u03b22 subunits, after which CCDC32 is released to yield the complete adaptor [#2]. CCDC32 engages AP-2 through multiple contacts: a predicted \\u03b1-helix (aa78\\u201398) required for AP-2 binding and endocytic function, the \\u03b1-appendage domain at sites shared with canonical endocytic regulators plus a novel conserved pocket, and cargo-binding sites engaged via its own cargo sorting motifs [#3, #4]. Two amphipathic helices bind the \\u03b1/\\u03c32 heterodimer and actively prevent AP-2 assembly\\u2014and disassemble AP-2 tetramers\\u2014in solution, an inhibition relieved by PIP2-containing membranes that act as a molecular switch to deposit assembled AP-2 at the plasma membrane; consistent with this role, loss of CCDC32 produces unstable flat clathrin assemblies and impairs coated-pit invagination and transferrin uptake [#0, #3, #4]. CCDC32 is additionally required for normal ciliogenesis, and a disease-causing mutation that disrupts its AP-2 chaperone function underlies the associated congenital syndrome [#1, #2].\",\n  \"teleology\": [\n    {\n      \"year\": 2011,\n      \"claim\": \"Before any functional assignment, an unbiased interaction screen offered the first candidate binding partner for the uncharacterized CCDC32 protein.\",\n      \"evidence\": \"Yeast two-hybrid screen of a human monocyte cDNA library against an annexin A2 C-terminal fragment\",\n      \"pmids\": [\"21963895\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single yeast two-hybrid result not confirmed by an orthogonal method\", \"No functional follow-up linking this interaction to a cellular role\", \"Relationship of this interaction to the later-established endocytic function is unestablished\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"The question of what physiological process CCDC32 supports was first answered by showing it is required for cilia formation, connecting the gene to a congenital syndrome.\",\n      \"evidence\": \"Zebrafish morpholino knockdown with cilia readout plus mammalian cell loss-of-function\",\n      \"pmids\": [\"32307552\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism by which CCDC32 supports ciliogenesis not defined\", \"Relationship between the ciliary role and endocytic role not resolved\", \"Morpholino-based knockdown not corroborated by genetic deletion\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"An unbiased genetic approach placed CCDC32 in the endocytic machinery, establishing AP-2 binding and a functional requirement for cargo uptake.\",\n      \"evidence\": \"Co-essentiality profiling validated by transferrin uptake assay and localization to clathrin-coated pits\",\n      \"pmids\": [\"33859415\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not define which AP-2 subunits or domains are contacted\", \"Mechanism of action within the coated pit not addressed\", \"Single lab, correlative localization\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Reconstitution revealed CCDC32's mechanism as an AP-2 assembly chaperone acting downstream of AAGAB, explaining how disease mutations impair function.\",\n      \"evidence\": \"Biochemical reconstitution, co-immunoprecipitation, in vitro assembly assays, and disease-variant mutagenesis\",\n      \"pmids\": [\"39145939\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the ternary template not resolved at this stage\", \"Trigger for CCDC32 release after assembly not defined\", \"Link to the ciliary phenotype not addressed\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Cell-based and structural studies mapped the AP-2 binding interfaces and showed CCDC32 stabilizes coated pits, while defining a PIP2-gated inhibitory mechanism.\",\n      \"evidence\": \"siRNA knockdown with live imaging, deletion mutagenesis, in vitro binding, cryo-EM, and PIP2-membrane and AP-2 disassembly assays\",\n      \"pmids\": [\"38979322\", \"41489497\", \"40799577\", \"42234739\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the membrane switch is coordinated with cargo loading in vivo not fully defined\", \"Whether the cargo sorting motifs in CCDC32 engage physiological cargo unresolved\", \"Quantitative kinetics of inhibition relief at native plasma membranes not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether CCDC32's ciliary requirement reflects its AP-2 chaperone activity or a distinct molecular function remains unresolved.\",\n      \"evidence\": \"No timeline study connects the ciliogenesis phenotype to the endocytic mechanism\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No mechanistic bridge between AP-2 assembly and ciliogenesis\", \"No structural model of CCDC32 outside the AP-2-bound state\", \"Tissue-specific requirements underlying the syndrome not defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0044183\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"AP2A1\", \"AP2S1\", \"AP2M1\", \"AP2B1\", \"AAGAB\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}