AP3D1 encodes the δ subunit of the AP-3 adaptor protein complex and is essential for assembly and stability of both the ubiquitous and neuronal forms of AP-3, which direct vesicle-mediated trafficking of cargo to late endosomal and lysosomal compartments PMID:26744459. Through its δ subunit, AP3D1 selects specific cargo for lysosomal delivery: it binds S-palmitoylated IFNGR1 (Cys122) to route the receptor for lysosomal degradation PMID:33627378, and it captures DRAM2 in a phosphorylation-dependent manner, requiring RSK2-mediated phosphorylation at Ser263, such that the non-phosphorylatable DRAM2(S263A) loses AP3D1 binding and is instead diverted to the plasma membrane to enhance exosome secretion PMID:42059423. AP3D1 also participates in TGFβ2 secretion via an AP-3-dependent late endosomal/exosomal route PMID:34166600 and governs the endolysosomal trafficking and lysosomal localization of cargo such as RNF13 PMID:34831286. Consistent with its role in lysosome-related organelle biogenesis, loss-of-function mutations in AP3D1 destabilize the complex and cause a Hermansky-Pudlak-type disorder featuring immunodeficiency with defective T-cell degranulation PMID:26744459 and abnormal platelet dense granule storage PMID:30472485. In the nervous system, AP3D1 loss perturbs neurotransmitter vesicle turnover and synaptic transmission and is required for proper retinal progenitor differentiation [PMID:19032734, PMID:19631730].
| Year | Confidence | Finding | PMIDs | Journal |
|---|---|---|---|---|
| 2016 | High | AP3D1 encodes the AP3δ subunit essential for both the ubiquitous and neuronal forms of the AP-3 complex; homozygous loss-of-function mutation in AP3D1 destabilizes the entire AP-3 complex, and retroviral reconstitution with wild-type AP3D1 restores AP-3 complex formation and rescues the T-cell degranulation defect in patient cells. | PMID:26744459 | Blood |
| 2018 | Medium | Homozygous frameshift mutation in AP3D1 (c.1978delG, p.Ala660Argfs*54) causes loss of AP-3 complex function, leading to abnormal platelet storage pathway, confirming AP3D1/AP3δ is required for lysosome-related organelle biogenesis including platelet dense granules. | PMID:30472485 | European journal of medical genetics |
| 2021 | High | AP3D1 binds palmitoylated IFNGR1 (S-palmitoylated on Cys122) and sorts it to the lysosome for degradation; optineurin interacts with AP3D1 to prevent this palmitoylation-dependent lysosomal sorting, thereby maintaining IFNGR1 surface expression and IFNγ/MHC-I signaling. | PMID:33627378 | Cancer discovery |
| 2021 | Medium | AP3D1 forms a cellular protein complex with FAM13A and TGFβ2; this complex mediates secretion of TGFβ2 through an AP-3-dependent pathway involving delivery to late endosomal compartments for exosomal secretion, with FAM13A acting as a negative regulator targeting a late stage of coat-cargo dissociation. | PMID:34166600 | American journal of respiratory cell and molecular biology |
| 2021 | Medium | Knockdown of AP3D1 (AP-3 complex subunit) alters the lysosomal localization of wild-type RNF13 and causes abnormal enlargement of endosomal vesicles, placing AP3D1 upstream of RNF13 endolysosomal trafficking. | PMID:34831286 | Cells |
| 2009 | Medium | Loss of Ap3d1 in mocha mice (10,639 bp deletion covering exons 2–6) results in deficiency in vesicle transport and storage, affecting neurotransmitter vesicle turnover; Ap3d1-null hippocampal neurons show higher input resistance and faster, stronger depression of glutamatergic autaptic EPSCs compared to controls. | PMID:19032734 | BMC research notes |
| 2009 | Medium | Ap3d1 loss in mocha mice causes complete absence of cholinergic amacrine cells and reduction of parvalbumin-expressing and other amacrine cell subtypes in the retina without affecting overall retinal layering, cell number, proliferation, or apoptosis, indicating AP3D1 regulates retinal progenitor cell competence and differentiation. | PMID:19631730 | International journal of developmental neuroscience |
| 2009 | Medium | The Nxf1(CAST) allele suppresses the Ap3d1(mh2J) IAP retrovirus insertion mutation by approximately 2-fold increase in correctly-spliced Ap3d1 mRNA and decrease in mutant-specific alternatively-processed RNA, demonstrating that Ap3d1 expression can be rescued at a functional threshold through modulation of pre-mRNA splicing. | PMID:19436707 | PLoS genetics |
| 2022 | Medium | Loss of ap3d1 in zebrafish (crasher mutant and ap3d1 knockout) causes reduced expression of melanogenesis genes dct and tyrp1b (but not tyr), and autophagy pathway genes are upregulated; treatment with autophagy inhibitor bafilomycin A1 significantly decreases melanophore number in ap3d1 mutants, indicating ap3d1 promotes melanophore survival by limiting excessive autophagy. | PMID:35816398 | Pigment cell & melanoma research |
| 2026 | High | AP3D1/AP-3 is required for RPS6KA3/RSK2-phosphorylation-dependent trafficking of DRAM2 to the late endosomal-lysosomal pathway; phosphorylation of DRAM2 at Ser263 enables its binding to AP3D1, and the non-phosphorylatable DRAM2(S263A) mutant fails to bind AP3D1, exhibits defective lysosomal trafficking, and is instead redirected toward the plasma membrane where it enhances exosome secretion. | PMID:42059423 | Autophagy |
| 2018 | Low | Bovine AP3D1 (boAP3D1) interacts in vitro with the N-terminal domain of BLV envelope glycoprotein gp51; key amino acids on AP3D1 (Lys925, Asp807, Asp695, Arg800) and gp51 were identified as probable interaction residues, and recombinant N-terminal gp51 binding to MDBK cells was sensitive to trypsin and chymotrypsin treatment. | PMID:29928016 | PloS one |