AP-4 adaptor complex
An AP-type membrane coat adaptor complex that consists of beta4, epsilon, mu4 and sigma4 subunits and is found associated with membranes in the trans-Golgi network; it is not clear whether AP-4 forms clathrin coats in vivo. [GO:0030124]
Components
| Component | Type | Part of / acts on | Grounding | Genes | Stoichiometry | Essential | Role |
|---|---|---|---|---|---|---|---|
| AP-4 beta4 subunit | Protein | part of | Reviewed label only (reviewed name; no accession asserted) | UNKNOWN | Large beta4 subunit of the heterotetrameric AP-4 adaptor complex.
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| AP-4 epsilon subunit | Protein | part of | Reviewed label only (reviewed name; no accession asserted) | UNKNOWN | Large epsilon subunit of the heterotetrameric AP-4 adaptor complex.
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| AP-4 mu4 subunit | Protein | part of | Reviewed label only (reviewed name; no accession asserted) | UNKNOWN | Medium mu4 subunit of the heterotetrameric AP-4 adaptor complex.
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| AP-4 sigma4 subunit | Protein | part of | Reviewed label only (reviewed name; no accession asserted) | UNKNOWN | Small sigma4 subunit of the heterotetrameric AP-4 adaptor complex.
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Functions
- AP-4-associated trans-Golgi network cargo sorting — AP-4 is a trans-Golgi-network-associated adaptor complex implicated in recognition and sorting of cargo proteins with tyrosine-based motifs.
DOI:10.1091/mbc.10.8.2787Hirst et al. 1999 identified AP-4, localized it to nonclathrin-coated vesicles near the trans-Golgi network, and reported that its mu4 subunit specifically interacts with a tyrosine-based sorting signal.
Mechanism graphs
Beta4, epsilon, mu4 and sigma4 subunits form AP-4 (FUNCTION)
The AP-4 adaptor complex is a heterotetramer associated with trans-Golgi-network membranes and implicated in cargo sorting.
| Subject | Predicate | Object | Evidence |
|---|---|---|---|
| AP-4 beta4 subunit | is part of | AP-4 adaptor complex |
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| AP-4 epsilon subunit | is part of | AP-4 adaptor complex |
|
| AP-4 mu4 subunit | is part of | AP-4 adaptor complex |
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| AP-4 sigma4 subunit | is part of | AP-4 adaptor complex |
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| AP-4 adaptor complex | associates with | trans-Golgi network membrane |
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| AP-4 adaptor complex | is implicated in | trans-Golgi network cargo sorting |
|
Discussions
- INTERPRETATION (RESOLVED): Avoid modeling AP-4 as a constitutive clathrin-coat adaptor. GO:0030124 makes AP-4 a child of AP-type membrane coat adaptor complex but explicitly notes that it is unclear whether AP-4 forms clathrin coats in vivo. This record therefore keeps AP-4 under the AP-type parent while avoiding a universal AP-4-to-clathrin-coat edge or a clathrin-coat part_of assertion.
- CURATION_TODO (OPEN): Resolve exact source-neutral groundings for the AP-4 beta4, epsilon, mu4 and sigma4 subunit classes. GO gives the exact AP-4 complex identity and names its subunit classes, but exact source-neutral InterPro, Pfam or NCBIfam CURIEs for those AP-4-specific classes were not curated in this pass.
Evidence
GO:0030124Gene Ontology cellular-component term for the AP-4 adaptor complex.GO:0030119Gene Ontology cellular-component parent term for AP-type membrane coat adaptor complexes.DOI:10.1091/mbc.10.8.2787Hirst, Bright, Rous and Robinson 1999, Characterization of a Fourth Adaptor-related Protein Complex, Molecular Biology of the Cell.
Curation history
2026-09-16T13:57:07Zcodex · CREATED_RECORD — Scaffolded by scripts/new_record.py2026-09-16T13:58:17Zcodex · EXPANDED_RECORD — Added AP-type parentage, reviewed-label-only beta4/epsilon/mu4/sigma4 subunits, an AP-4 cargo-sorting function, GO/DOI evidence, a nonmechanistic AP-4 topology graph, and clathrin-scope and subunit-grounding discussions.2026-09-16T14:10:30Zcodex · ADDRESSED_PR_REVIEW — Softened AP-4 cargo-sorting wording to match the Hirst et al. 1999 discovery evidence; addresses PR #1100 review issue #1101.