aph-1 encodes the Drosophila anterior pharynx-defective 1 protein, a seven-transmembrane subunit of gamma-secretase, the intramembrane aspartyl protease complex formed with Presenilin (Psn), Nicastrin (Nct) and pen-2. Aph-1 acts as an assembly scaffold that associates with Nicastrin and stabilises the Presenilin holoprotein within the nascent complex before pen-2-dependent endoproteolytic activation. As a required subunit of gamma-secretase, aph-1 is needed for the intramembrane cleavage of ligand-activated Notch that releases the Notch intracellular domain and for gamma-secretase cleavage of other type I membrane proteins such as human APP expressed in fly cells.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005770 late endosome | IDA PMID:20421416 In vivo reconstitution of gamma-secretase in Drosophila resu... | KEEP AS NON CORE | Summary: Aph-1, as part of reconstituted gamma-secretase, localises to late endosomes. Reason: Gamma-secretase is distributed across the plasma membrane and endolysosomal compartments where substrates are cleaved; the in vivo reconstitution study reports a distribution matching endogenous gamma-secretase. Accurate but not the defining location. Supporting Evidence: PMID:20421416 has biochemical properties and a subcellular distribution resembling those of endogenous gamma-secretase |
| GO:0005886 plasma membrane | NAS PMID:12110170 aph-1 and pen-2 are required for Notch pathway signaling, ga... | KEEP AS NON CORE | Summary: Aph-1 at the plasma membrane (non-traceable author statement). Reason: Gamma-secretase acts at the plasma membrane and in endosomes; accurate but non-defining location. |
| GO:0006509 membrane protein ectodomain proteolysis | IDA PMID:20421416 In vivo reconstitution of gamma-secretase in Drosophila resu... | MODIFY | Summary: Annotation to membrane protein ectodomain proteolysis from in vivo reconstitution of gamma-secretase. Reason: Gamma-secretase performs the intramembrane (S3/epsilon) cleavage that releases the intracellular domain of substrates whose ectodomain has already been shed by ADAM-family sheddases such as Kuzbanian. Ectodomain shedding is not a gamma-secretase reaction, so the appropriate process is membrane protein intracellular domain proteolysis. Proposed replacements: membrane protein intracellular domain proteolysis Supporting Evidence: PMID:20421416 coexpression of these four components promotes the efficient assembly of mature, proteolytically active gamma-secretase PMID:20421416 markedly reduced cleavage of some APP family members compared to cleavage of the Notch receptor |
| GO:0007219 Notch signaling pathway | IBA GO_REF:0000033 | ACCEPT | Summary: Aph-1 is required for Notch signal transduction as a subunit of gamma-secretase. Reason: The S3 intramembrane cleavage by gamma-secretase releases the Notch intracellular domain and is an obligatory step of Notch signaling; the subunit is part of the enzyme that executes that step. Supporting Evidence: PMID:12110170 RNAi-mediated inactivation of aph-1, pen-2, or nicastrin in cultured Drosophila cells reduces gamma-secretase cleavage of betaAPP and Notch substrates and reduces the levels of processed presenilin. PMID:12110170 aph-1 and pen-2, like nicastrin, are required for the activity and accumulation of gamma-secretase. |
| GO:0007219 Notch signaling pathway | IGI PMID:20421416 In vivo reconstitution of gamma-secretase in Drosophila resu... | ACCEPT | Summary: Aph-1 is required for Notch signal transduction as a subunit of gamma-secretase. Reason: The S3 intramembrane cleavage by gamma-secretase releases the Notch intracellular domain and is an obligatory step of Notch signaling; the subunit is part of the enzyme that executes that step. Supporting Evidence: PMID:12110170 RNAi-mediated inactivation of aph-1, pen-2, or nicastrin in cultured Drosophila cells reduces gamma-secretase cleavage of betaAPP and Notch substrates and reduces the levels of processed presenilin. PMID:12110170 aph-1 and pen-2, like nicastrin, are required for the activity and accumulation of gamma-secretase. |
| GO:0007219 Notch signaling pathway | IMP PMID:12110170 aph-1 and pen-2 are required for Notch pathway signaling, ga... | ACCEPT | Summary: Aph-1 is required for Notch signal transduction as a subunit of gamma-secretase. Reason: The S3 intramembrane cleavage by gamma-secretase releases the Notch intracellular domain and is an obligatory step of Notch signaling; the subunit is part of the enzyme that executes that step. Supporting Evidence: PMID:12110170 RNAi-mediated inactivation of aph-1, pen-2, or nicastrin in cultured Drosophila cells reduces gamma-secretase cleavage of betaAPP and Notch substrates and reduces the levels of processed presenilin. PMID:12110170 aph-1 and pen-2, like nicastrin, are required for the activity and accumulation of gamma-secretase. |
| GO:0007220 Notch receptor processing | IBA GO_REF:0000033 | ACCEPT | Summary: Aph-1 is required for gamma-secretase cleavage of Notch. Reason: Gamma-secretase executes the S3 intramembrane cleavage of Notch; as an essential subunit of the protease complex, this subunit directly participates in Notch receptor processing. The IBA reflects the conserved function of the gamma-secretase subunit family. Supporting Evidence: PMID:12110170 RNAi-mediated inactivation of aph-1, pen-2, or nicastrin in cultured Drosophila cells reduces gamma-secretase cleavage of betaAPP and Notch substrates and reduces the levels of processed presenilin. |
| GO:0007220 Notch receptor processing | NAS PMID:10206646 Presenilin is required for activity and nuclear access of No... | ACCEPT | Summary: Early statement (Struhl and Greenwald) that presenilin-dependent cleavage releases the Notch intracellular domain. Reason: The cited paper concerns Presenilin, but the process is executed by the gamma-secretase complex of which Aph-1 is an essential subunit; consistent with direct experimental evidence for this subunit. Supporting Evidence: PMID:10206646 presenilin is required for the proteolytic release of the intracellular domain from the membrane following activation of Notch by ligand PMID:12110170 RNAi-mediated inactivation of aph-1, pen-2, or nicastrin in cultured Drosophila cells reduces gamma-secretase cleavage of betaAPP and Notch substrates and reduces the levels of processed presenilin. |
| GO:0016020 membrane | IEA GO_REF:0000120 | MODIFY | Summary: Aph-1 is an integral membrane protein. Reason: Correct but general; the informative cellular component is the membrane-embedded gamma-secretase complex, so MODIFY to gamma-secretase complex, which aph-1 already carries (IBA, IDA, IPI). Proposed replacements: gamma-secretase complex |
| GO:0016020 membrane | NAS PMID:12660785 The role of presenilin cofactors in the gamma-secretase comp... | MODIFY | Summary: Aph-1 is an integral membrane protein. Reason: Correct but general; the informative cellular component is the membrane-embedded gamma-secretase complex, so MODIFY to gamma-secretase complex, which aph-1 already carries (IBA, IDA, IPI). Proposed replacements: gamma-secretase complex |
| GO:0016485 protein processing | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Protein processing by the gamma-secretase complex. Reason: Gamma-secretase processes membrane proteins by intramembrane cleavage; general but correct (more specific terms such as membrane protein intracellular domain proteolysis are also annotated). Supporting Evidence: PMID:12110170 RNAi-mediated inactivation of aph-1, pen-2, or nicastrin in cultured Drosophila cells reduces gamma-secretase cleavage of betaAPP and Notch substrates and reduces the levels of processed presenilin. |
| GO:0016485 protein processing | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Protein processing by the gamma-secretase complex. Reason: Gamma-secretase processes membrane proteins by intramembrane cleavage; general but correct (more specific terms such as membrane protein intracellular domain proteolysis are also annotated). Supporting Evidence: PMID:12110170 RNAi-mediated inactivation of aph-1, pen-2, or nicastrin in cultured Drosophila cells reduces gamma-secretase cleavage of betaAPP and Notch substrates and reduces the levels of processed presenilin. |
| GO:0030674 protein-macromolecule adaptor activity | IBA GO_REF:0000033 | ACCEPT | Summary: Aph-1 acts as a scaffold for gamma-secretase assembly. Reason: Aph-1 associates with Nicastrin and stabilises the Presenilin holoprotein, bringing the subunits together into the nascent complex; protein-macromolecule adaptor activity is an appropriate MF for this scaffolding role and is consistent with the human APH1A annotations. The IBA is phylogenetically sound. Supporting Evidence: PMID:12660785 Here we show that Drosophila APH-1 (Aph-1) increases the stability of Drosophila presenilin (Psn) holoprotein in the complex. PMID:12110170 encoding multipass transmembrane proteins, that interact strongly with sel-12/presenilin and aph-2/nicastrin |
| GO:0031293 membrane protein intracellular domain proteolysis | IDA PMID:12660785 The role of presenilin cofactors in the gamma-secretase comp... | ACCEPT | Summary: Aph-1 is required for intramembrane cleavage that releases substrate intracellular domains. Reason: This is the core process executed by gamma-secretase, and Drosophila gamma-secretase subunits are required for, and sufficient in combination to reconstitute, this activity. Supporting Evidence: PMID:12660785 Co-expression of Drosophila Pen-2 with Aph-1 and nicastrin increases the formation of Psn fragments as well as gamma-secretase activity. |
| GO:0034205 amyloid-beta formation | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Gamma-secretase subunit required for cleavage of (human) betaAPP to generate amyloid-beta. Reason: The gamma-secretase complex does perform the cleavage that generates amyloid-beta, so the subunit participates; however, in Drosophila the assays use human APP as a reporter substrate and the fly APP-like protein (Appl) is poorly processed by reconstituted fly gamma-secretase. Retained as non-core. Supporting Evidence: PMID:12110170 RNAi-mediated inactivation of aph-1, pen-2, or nicastrin in cultured Drosophila cells reduces gamma-secretase cleavage of betaAPP and Notch substrates and reduces the levels of processed presenilin. PMID:20421416 markedly reduced cleavage of some APP family members compared to cleavage of the Notch receptor |
| GO:0034205 amyloid-beta formation | IDA PMID:20421416 In vivo reconstitution of gamma-secretase in Drosophila resu... | KEEP AS NON CORE | Summary: Gamma-secretase subunit required for cleavage of (human) betaAPP to generate amyloid-beta. Reason: The gamma-secretase complex does perform the cleavage that generates amyloid-beta, so the subunit participates; however, in Drosophila the assays use human APP as a reporter substrate and the fly APP-like protein (Appl) is poorly processed by reconstituted fly gamma-secretase. Retained as non-core. Supporting Evidence: PMID:12110170 RNAi-mediated inactivation of aph-1, pen-2, or nicastrin in cultured Drosophila cells reduces gamma-secretase cleavage of betaAPP and Notch substrates and reduces the levels of processed presenilin. PMID:20421416 markedly reduced cleavage of some APP family members compared to cleavage of the Notch receptor |
| GO:0034205 amyloid-beta formation | IMP PMID:12110170 aph-1 and pen-2 are required for Notch pathway signaling, ga... | KEEP AS NON CORE | Summary: Gamma-secretase subunit required for cleavage of (human) betaAPP to generate amyloid-beta. Reason: The gamma-secretase complex does perform the cleavage that generates amyloid-beta, so the subunit participates; however, in Drosophila the assays use human APP as a reporter substrate and the fly APP-like protein (Appl) is poorly processed by reconstituted fly gamma-secretase. Retained as non-core. Supporting Evidence: PMID:12110170 RNAi-mediated inactivation of aph-1, pen-2, or nicastrin in cultured Drosophila cells reduces gamma-secretase cleavage of betaAPP and Notch substrates and reduces the levels of processed presenilin. PMID:20421416 markedly reduced cleavage of some APP family members compared to cleavage of the Notch receptor |
| GO:0035333 Notch receptor processing, ligand-dependent | IGI PMID:20421416 In vivo reconstitution of gamma-secretase in Drosophila resu... | ACCEPT | Summary: Aph-1 participates in ligand-dependent Notch processing in vivo. Reason: Reconstituted gamma-secretase (Psn, Nct, Aph-1, Pen-2) cleaves ligand-activated Notch in vivo; accurate and appropriately specific. Supporting Evidence: PMID:20421416 coexpression of these four components promotes the efficient assembly of mature, proteolytically active gamma-secretase |
| GO:0050821 protein stabilization | IMP PMID:12660785 The role of presenilin cofactors in the gamma-secretase comp... | ACCEPT | Summary: Aph-1 stabilises the Presenilin holoprotein in the gamma-secretase complex. Reason: Directly shown for Drosophila Aph-1 by Takasugi et al.; this stabilisation is the mechanism by which Aph-1 contributes to gamma-secretase assembly. Supporting Evidence: PMID:12660785 Here we show that Drosophila APH-1 (Aph-1) increases the stability of Drosophila presenilin (Psn) holoprotein in the complex. |
| GO:0055037 recycling endosome | IDA PMID:20421416 In vivo reconstitution of gamma-secretase in Drosophila resu... | KEEP AS NON CORE | Summary: Aph-1, as part of reconstituted gamma-secretase, localises to recycling endosomes. Reason: As for late endosome: one of several membrane compartments where gamma-secretase resides; retained as non-core. Supporting Evidence: PMID:20421416 has biochemical properties and a subcellular distribution resembling those of endogenous gamma-secretase |
| GO:0070765 gamma-secretase complex | IBA GO_REF:0000033 | ACCEPT | Summary: Aph-1 is a core subunit of the gamma-secretase complex. Reason: Co-expression of the four Drosophila subunits reconstitutes active gamma-secretase, and the subunits co-purify; this is the defining complex membership. Supporting Evidence: PMID:20421416 coexpression of these four components promotes the efficient assembly of mature, proteolytically active gamma-secretase PMID:12660785 Co-expression of Drosophila Pen-2 with Aph-1 and nicastrin increases the formation of Psn fragments as well as gamma-secretase activity. |
| GO:0070765 gamma-secretase complex | IDA PMID:12660785 The role of presenilin cofactors in the gamma-secretase comp... | ACCEPT | Summary: Aph-1 is a core subunit of the gamma-secretase complex. Reason: Co-expression of the four Drosophila subunits reconstitutes active gamma-secretase, and the subunits co-purify; this is the defining complex membership. Supporting Evidence: PMID:20421416 coexpression of these four components promotes the efficient assembly of mature, proteolytically active gamma-secretase PMID:12660785 Co-expression of Drosophila Pen-2 with Aph-1 and nicastrin increases the formation of Psn fragments as well as gamma-secretase activity. |
| GO:0070765 gamma-secretase complex | IPI PMID:12660785 The role of presenilin cofactors in the gamma-secretase comp... | ACCEPT | Summary: Aph-1 is a core subunit of the gamma-secretase complex. Reason: Co-expression of the four Drosophila subunits reconstitutes active gamma-secretase, and the subunits co-purify; this is the defining complex membership. Supporting Evidence: PMID:20421416 coexpression of these four components promotes the efficient assembly of mature, proteolytically active gamma-secretase PMID:12660785 Co-expression of Drosophila Pen-2 with Aph-1 and nicastrin increases the formation of Psn fragments as well as gamma-secretase activity. |
| GO:0070765 gamma-secretase complex | IPI PMID:20421416 In vivo reconstitution of gamma-secretase in Drosophila resu... | ACCEPT | Summary: Aph-1 is a core subunit of the gamma-secretase complex. Reason: Co-expression of the four Drosophila subunits reconstitutes active gamma-secretase, and the subunits co-purify; this is the defining complex membership. Supporting Evidence: PMID:20421416 coexpression of these four components promotes the efficient assembly of mature, proteolytically active gamma-secretase PMID:12660785 Co-expression of Drosophila Pen-2 with Aph-1 and nicastrin increases the formation of Psn fragments as well as gamma-secretase activity. |
Loading supporting content…
Download this section (compressed HTML)Q: Does Drosophila, which has a single aph-1 gene, use alternative aph-1 isoforms to tune gamma-secretase substrate preference in the way mammalian APH1A and APH1B complexes differ?
Experiment: Express aph-1 point mutants in an aph-1 null background in vivo and measure Psn holoprotein levels, Notch S3 cleavage, and cleavage of non-Notch substrates.
Hypothesis: Aph-1 transmembrane residues contacting Presenilin are required for holoprotein stabilisation but separable from substrate selectivity.
Loading supporting content…
Download this section (compressed HTML)anterior pharynx defective 1 (aph-1) encodes a scaffolding subunit of the gamma-secretase complex together with the products of Psn, Nct and pen-2. It is involved in several Notch related processes such as differentiation, cellular organization and developmental patterning via gamma-secretase proteolitic function.
Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)