apb-1 encodes the single large beta-adaptin of Caenorhabditis elegans, a subunit shared between the AP-1 and AP-2 clathrin adaptor complexes (mammals use separate beta1 and beta2 paralogues). Beta-adaptin forms one half of the adaptor trunk, pairs with the mu subunit as a hemicomplex, and through its hinge and appendage domains recruits clathrin and accessory endocytic proteins to nascent coated pits. Within AP-2, APB-1 localises with mu2 to presynaptic regions of the nerve ring and to the oocyte plasma membrane and is required for clathrin-mediated uptake of yolk by oocytes and for clathrin- and AP-2-dependent engulfment and phagosome maturation of apoptotic cell corpses downstream of the CED-1/CED-6 receptor pathway. Within AP-1 it participates in clathrin-coated sorting at the trans-Golgi network of polarised epithelia such as the intestine. Depletion of apb-1 blocks yolk endocytosis and is embryonic lethal.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005515 protein binding | IPI PMID:23696751 Clathrin and AP2 are required for phagocytic receptor-mediat... | REMOVE | Summary: IPI protein binding with CED-6: 35S-labelled APB-1 bound GST-CED-6, GST-DYN-1 and GST-LST-4 directly in vitro in the apoptotic-cell-clearance study. Reason: The interaction is credible but generic protein binding carries no functional information; the biology (AP-2 coupling the CED-1/CED-6 phagocytic receptor complex to clathrin) is represented by the clathrin-binding and endocytosis rows. Removal does not dispute the reported interaction. Supporting Evidence: PMID:23696751 GST-CED-6 directly interacted with 35S-labeled APA-2, APB-1 and DPY-23, and His6-tagged CHC-1C (Figure 4A). |
| GO:0005737 cytoplasm | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA machine-learning mapping to cytoplasm. Adaptor complexes are cytosolic and cycle onto the cytoplasmic face of membranes; APB-1::GFP is seen in cell bodies as well as at synapses and the oocyte plasma membrane. Reason: Correct though general; the informative locations are the plasma membrane (AP-2) and trans-Golgi network (AP-1). Supporting Evidence: PMID:23482940 Tagged β-adaptin and μ2-adaptin are localized to synaptic regions of the nerve ring (the major neuropil of the worm, Figure 6B,C) and at the plasma membrane in oocytes (Figure 6—figure supplement 1). |
| GO:0005802 trans-Golgi network | IBA GO_REF:0000033 | ACCEPT | Summary: IBA trans-Golgi network from the beta-adaptin family node PTN000123671 (plant, fly and mammalian beta-adaptins). Because the worm has a single beta-adaptin shared between AP-1 and AP-2, the AP-1 (TGN) localisation applies: beta remains in AP-1 complexes when mu2 is lost, and GFP-APB-1 labels TGN-associated intestinal puncta with SMAP-1 in the deep-research literature. Reason: Correct for this gene: APB-1 is the beta subunit of worm AP-1 as well as AP-2, so the TGN location inherited from the beta-adaptin family is a genuine site of activity. Supporting Evidence: PMID:23482940 Beta levels are reduced in apm-2 mutants compared to apa-2 mutants; however, beta is still present and stable in AP1 complexes in apm-2 mutants. file:worm/apb-1/apb-1-deep-research-falcon.md GFP–APB-1 labels punctate structures and colocalizes with SMAP-1, an Arf-family GAP implicated in TGN coat assembly and polarized secretion. |
| GO:0006886 intracellular protein transport | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro adaptin-domain mapping to intracellular protein transport; beta-adaptin-containing AP-1 and AP-2 coats move membrane proteins between plasma membrane, endosomes and TGN. Reason: Correct general parent of the AP-2 endocytic and AP-1 TGN sorting roles. Supporting Evidence: PMID:10588660 elegans clathrin heavy chain, α-adaptin, and β-adaptin RNAi all produced similar defects in oocytes and embryos. |
| GO:0006898 receptor-mediated endocytosis | IBA GO_REF:0000033 | ACCEPT | Summary: IBA receptor-mediated endocytosis from the AP-2 beta node PTN000875440 (human AP2B1, rodent Ap2b1 and the worm gene itself). Beta-adaptin RNAi abolishes yolk-receptor-mediated uptake of YP170::GFP by oocytes. Reason: Core AP-2 function of the beta subunit, with direct worm experimental grounding; the presence of apb-1 among the node's sources reflects that grounding. Supporting Evidence: PMID:10588660 elegans clathrin heavy chain, α-adaptin, and β-adaptin RNAi all produced similar defects in oocytes and embryos. PMID:19047463 RNA interference against clathrin, α adaptin, or β2 adaptin each abolished uptake of a GFP-tagged vitellogenin (YP170-GFP) into oocytes. |
| GO:0006898 receptor-mediated endocytosis | IMP PMID:10588660 Receptor-mediated endocytosis in the Caenorhabditis elegans ... | ACCEPT | Summary: RNAi of beta-adaptin (Y71H2) in the yolk-uptake screen produced the same loss of YP170::GFP endocytosis and embryonic defects as clathrin heavy chain and alpha-adaptin RNAi, whereas mu2 and sigma2 RNAi did not. Reason: Direct genetic evidence that APB-1 is required for receptor-mediated yolk endocytosis, consistent with the beta subunit's role in linking AP-2 to clathrin. Supporting Evidence: PMID:10588660 elegans clathrin heavy chain, α-adaptin, and β-adaptin RNAi all produced similar defects in oocytes and embryos. PMID:10588660 These results are consistent with the proposed roles of clathrin, α-adaptin, and β-adaptin in coated pit and coated vesicle formation. |
| GO:0012505 endomembrane system | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location mapping (endomembrane system, peripheral membrane protein, cytoplasmic side). APB-1 acts on the cytoplasmic face of the plasma membrane (AP-2) and of the TGN (AP-1). Reason: Correct but very general; retained as an umbrella for the two specific membrane sites. Supporting Evidence: PMID:23482940 Tagged β-adaptin and μ2-adaptin are localized to synaptic regions of the nerve ring (the major neuropil of the worm, Figure 6B,C) and at the plasma membrane in oocytes (Figure 6—figure supplement 1). |
| GO:0015031 protein transport | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro AP-complex beta subunit (IPR016342) mapping to protein transport. Reason: Correct general parent; the specific transport processes are the endocytosis rows. Supporting Evidence: PMID:10588660 These results are consistent with the proposed roles of clathrin, α-adaptin, and β-adaptin in coated pit and coated vesicle formation. |
| GO:0016192 vesicle-mediated transport | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro mapping to vesicle-mediated transport; clathrin-coated vesicle formation at the plasma membrane and TGN is vesicle-mediated transport. Reason: Correct high-level parent. Supporting Evidence: PMID:10588660 These results are consistent with the proposed roles of clathrin, α-adaptin, and β-adaptin in coated pit and coated vesicle formation. |
| GO:0030117 membrane coat | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro adaptin mapping to membrane coat; AP-1 and AP-2 adaptors are integral parts of clathrin coats. Reason: Correct: the adaptor is part of the clathrin membrane coat, though the clathrin adaptor complex terms are more specific. Supporting Evidence: PMID:10588660 The β-adaptin subunit is thought to connect the AP2 complex to clathrin ( Pearse and Robinson, 1990 ). |
| GO:0030121 AP-1 adaptor complex | IBA GO_REF:0000033 | ACCEPT | Summary: IBA AP-1 adaptor complex from node PTN000123672 (yeast, fission yeast and Dictyostelium beta1). In C. elegans the single beta-adaptin is shared by AP-1 and AP-2: it persists in AP-1 complexes when mu2 is lost, and the deep-research literature places GFP-APB-1 in the intestinal AP-1/SMAP-1 TGN sorting machinery. Reason: Not an over-propagation: the worm lacks a separate beta1, so APB-1 is genuinely a subunit of AP-1 as well as of AP-2. Supporting Evidence: PMID:23482940 The β subunit is shared by AP1 and AP2 in C PMID:23482940 Beta levels are reduced in apm-2 mutants compared to apa-2 mutants; however, beta is still present and stable in AP1 complexes in apm-2 mutants. file:worm/apb-1/apb-1-deep-research-falcon.md APB-1 is explicitly described as shared with AP-1. The AP-1 complex contains APG-1/γ1, APS-1/σ1, APB-1/β1, and one of the μ1 chains APM-1 or UNC-101. |
| GO:0030131 clathrin adaptor complex | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro mapping to clathrin adaptor complex; APB-1 is a subunit of both clathrin adaptor complexes AP-1 and AP-2. Reason: Correct parent of the AP-1 and AP-2 complex terms. Supporting Evidence: PMID:23482940 The β subunit is shared by AP1 and AP2 in C |
| GO:0030276 clathrin binding | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro mapping of the AP-complex beta subunit (IPR016342) to clathrin binding. The beta-adaptin hinge is the principal clathrin-recruiting element of AP-2, and the worm literature invokes this role directly. Reason: This is the defining molecular function of the beta subunit (clathrin box in the hinge plus appendage interactions), correctly assigned by the family mapping and consistent with the requirement for APB-1 in coated-pit-dependent yolk uptake. Supporting Evidence: PMID:10588660 The β-adaptin subunit is thought to connect the AP2 complex to clathrin ( Pearse and Robinson, 1990 ). PMID:23482940 Although clathrin is largely recruited to AP2 by the β subunit, even in the absence of β, it could still be recruited indirectly to the complex via AP180 |
| GO:0030122 AP-2 adaptor complex | IDA PMID:23482940 AP2 hemicomplexes contribute independently to synaptic vesic... | NEW | Summary: APB-1 is the beta2 subunit of the worm AP-2 complex: in alpha-adaptin (apa-2) mutants a stable beta/mu2 hemicomplex remains and APB-1::GFP stays at nerve-ring synapses and the oocyte plasma membrane, whereas in mu2 (apm-2) mutants beta is reduced; the apoptotic-cell-clearance study names apb-1 as the beta2 subunit alongside apa-2 and dpy-23. Reason: GOA carries AP-1 adaptor complex (by IBA) but not AP-2 adaptor complex for apb-1, because the family node for the shared worm beta-adaptin is the beta1 clade. The experimental data show APB-1 acting as the beta subunit of AP-2 in vivo, so the AP-2 complex membership should be recorded alongside AP-1. Supporting Evidence: PMID:23482940 Here we demonstrate that in the absence of α-adaptin that a μ2-β hemicomplex remains, and that in the absence of μ2-adaptin that a α-σ2 complex remains in vivo. PMID:23482940 Tagged β-adaptin and μ2-adaptin are localized to synaptic regions of the nerve ring (the major neuropil of the worm, Figure 6B,C) and at the plasma membrane in oocytes (Figure 6—figure supplement 1). PMID:23696751 RNAi of apa-2, apb-1 and dpy-23, which encode the α, β2 and μ2 subunits of the AP2 complex, respectively |
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