AP-2 adaptor complex
A heterotetrameric AP-type membrane coat adaptor complex that consists of alpha, beta2, mu2 and sigma2 subunits, and links clathrin to the membrane surface of a vesicle, and the cargo receptors during receptor/clathrin mediated endocytosis. Vesicles with AP-2-containing coats are normally found primarily near the plasma membrane, on endocytic vesicles. In at least humans, the AP-2 complex can be heterogeneric due to the existence of multiple subunit isoforms encoded by different alpha genes (alphaA and alphaC). [GO:0030122]
Part of: clathrin coat of endocytic vesicle (GO:0030128); clathrin coat of coated pit (GO:0030132)
Components
| Component | Type | Part of / acts on | Grounding | Genes | Stoichiometry | Essential | Role |
|---|---|---|---|---|---|---|---|
| AP-2 alpha subunit | Protein | part of | Reviewed label only (reviewed name; no accession asserted) | UNKNOWN | Large alpha subunit of the heterotetrameric AP-2 adaptor complex.
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| AP-2 beta2 subunit | Protein | part of | Reviewed label only (reviewed name; no accession asserted) | UNKNOWN | Large beta2 subunit of the heterotetrameric AP-2 adaptor complex.
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| AP-2 mu2 subunit | Protein | part of | Reviewed label only (reviewed name; no accession asserted) | UNKNOWN | Medium mu2 subunit of the heterotetrameric AP-2 adaptor complex.
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| AP-2 sigma2 subunit | Protein | part of | Reviewed label only (reviewed name; no accession asserted) | UNKNOWN | Small sigma2 subunit of the heterotetrameric AP-2 adaptor complex.
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Functions
- clathrin-dependent endocytosis
GO:0072583— AP-2 links clathrin to endocytic vesicle membranes and cargo receptors during clathrin-dependent endocytosis.GO:0030122GO:0030122 defines AP-2 by its clathrin-, membrane- and cargo-receptor-linking role during receptor/clathrin-mediated endocytosis.DOI:10.1016/j.cell.2010.05.006Jackson et al. 2010 analyze AP-2 membrane recruitment and cargo binding.
Mechanism graphs
Alpha, beta2, mu2 and sigma2 subunits form AP-2 (FUNCTION)
The AP-2 adaptor complex is a plasma-membrane clathrin adaptor and heterotetrameric part of endocytic and coated-pit clathrin coats.
| Subject | Predicate | Object | Evidence |
|---|---|---|---|
| AP-2 alpha subunit | is part of | AP-2 adaptor complex |
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| AP-2 beta2 subunit | is part of | AP-2 adaptor complex |
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| AP-2 mu2 subunit | is part of | AP-2 adaptor complex |
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| AP-2 sigma2 subunit | is part of | AP-2 adaptor complex |
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| AP-2 adaptor complex | is part of | clathrin coat of endocytic vesicle |
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| AP-2 adaptor complex | is part of | clathrin coat of coated pit |
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| AP-2 adaptor complex | supports | clathrin-dependent endocytosis |
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Discussions
- INTERPRETATION (RESOLVED): Represent AP-2 as an adaptor complex within endocytic clathrin coats, not as a complete clathrin coat. GO:0030122 is a clathrin adaptor complex and plasma membrane protein complex that is part of GO:0030128 clathrin coat of endocytic vesicle and GO:0030132 clathrin coat of coated pit. This record therefore represents the AP-2 adaptor heterotetramer and links it to those containing coats through part_of.
- INTERPRETATION (RESOLVED): Represent alphaA and alphaC as isoforms of one AP-2 alpha subunit class. The GO definition notes that human AP-2 can be heterogeneric because alphaA and alphaC isoforms are encoded by different genes. The taxon-agnostic component list therefore keeps one AP-2 alpha subunit class rather than making human paralogs separate core component classes.
- CURATION_TODO (OPEN): Resolve exact source-neutral groundings for the AP-2 alpha, beta2, mu2 and sigma2 subunit classes. GO gives the exact AP-2 complex identity and names its subunit classes, but exact source-neutral InterPro, Pfam or NCBIfam CURIEs for those AP-2-specific classes were not curated in this pass.
Evidence
GO:0030122Gene Ontology cellular-component term for the AP-2 adaptor complex.GO:0030131Gene Ontology cellular-component parent term for clathrin adaptor complexes.GO:0098797Gene Ontology cellular-component parent term for plasma membrane protein complexes.GO:0030128Gene Ontology cellular-component term for the endocytic-vesicle clathrin coat containing AP-2.GO:0030132Gene Ontology cellular-component term for the coated-pit clathrin coat containing AP-2.DOI:10.1016/S0092-8674(02)00735-3Collins, McCoy, Kent, Evans and Owen 2002, Molecular Architecture and Functional Model of the Endocytic AP2 Complex, Cell.DOI:10.1016/j.cell.2010.05.006Jackson et al. 2010, A Large-Scale Conformational Change Couples Membrane Recruitment to Cargo Binding in the AP2 Clathrin Adaptor Complex, Cell.
Curation history
2026-09-16T13:22:29Zcodex · CREATED_RECORD — Scaffolded by scripts/new_record.py2026-09-16T13:23:12Zcodex · EXPANDED_RECORD — Added clathrin-adaptor and plasma-membrane-complex parentage, endocytic-vesicle and coated-pit clathrin-coat parthood, reviewed-label-only alpha/beta2/mu2/sigma2 subunits, GO/DOI evidence, a nonmechanistic AP-2 topology graph, and coat-boundary, alpha-isoform and subunit-grounding discussions.2026-09-16T13:30:22Zcodex · CURATED_ID_LABEL_CORRESPONDENCE — Changed the GO:0072583-grounded AP-2 function label to the canonical GO label clathrin-dependent endocytosis2026-09-16T13:38:05Zcodex · ADDRESSED_PR_REVIEW — Aligned the AP-2 alpha isoform boundary discussion with GO's alphaA/alphaC nomenclature; addresses PR #1098 review issue #1099.