AP1S3 encodes σ1C, a sigma subunit of the AP-1 clathrin adaptor complex that governs endosomal membrane trafficking in keratinocytes, where its loss drives cutaneous autoinflammation [PMID:24791904, PMID:27388993]. AP1S3 is required for endosomal translocation of TLR3, and its depletion mislocalizes TLR3 and blunts downstream TLR3 signaling PMID:24791904. Independently, AP1S3 loss-of-function disrupts keratinocyte autophagy, causing accumulation of the autophagy adaptor p62, which activates NF-κB and drives overexpression of IL-36α; this cascade is recapitulated by pharmacological autophagy inhibition and reversed by IL-36 blockade in patient keratinocytes, defining the mechanistic route from adaptor dysfunction to autoinflammatory disease PMID:27388993. Beyond its keratinocyte role, AP1S3 physically binds the HCV E2 envelope protein and shields it from E6AP-mediated ubiquitin-dependent proteasomal degradation, and a synthetic peptide carrying the AP1S3-recognized motif inhibits HCV infection PMID:27079945.
| Year | Confidence | Finding | PMIDs | Journal |
|---|---|---|---|---|
| 2014 | Medium | AP1S3 (encoding AP-1 complex subunit σ1C) is required for endosomal translocation of TLR3 in keratinocytes; AP1S3 knockdown disrupted TLR3 trafficking to endosomes and markedly inhibited downstream TLR3 signaling | PMID:24791904 | American journal of human genetics |
| 2016 | High | AP1S3 loss-of-function disrupts keratinocyte autophagy, causing abnormal accumulation of the autophagy adaptor p62, which in turn activates NF-κB signaling and leads to overexpression of IL-36α; this autoinflammatory cascade was recapitulated by pharmacological autophagy inhibition and reversed by IL-36 blockade in patient keratinocytes | PMID:27388993 | The Journal of investigative dermatology |
| 2016 | Medium | AP1S3 interacts physically with HCV E2 protein (shown by co-immunoprecipitation) and protects E2 from ubiquitin-mediated proteasomal degradation; the E3 ligase E6AP was identified as mediating E2 ubiquitylation; a synthetic peptide containing the AP1S3-recognized motif inhibited HCV infection | PMID:27079945 | Antiviral research |
| 2016 | Low | AP-1/σ1A (AP1S1) and AP-1/σ1B (AP1S2) complexes differentially regulate neuronal early endosome maturation: σ1A binds ArfGAP1 (with higher affinity for brain-specific ArfGAP1), which recruits Rabex-5 to endosomes, enhancing Rab5(GTP)-stimulated Vps34 PI3-kinase activity required for multivesicular body formation; σ1B (AP1S2) binding of Rabex-5 prevents this complex and reduces endosomal Rabex-5. (Note: this paper characterizes σ1A and σ1B isoforms but not σ1C/AP1S3 directly.) | PMID:27411398 | Scientific reports |
| 2025 | Low | AP1S3 knockdown in breast cancer cells (MDA-MB-231 and MDA-MB-436) inhibited proliferation and migration; mechanistically, AP1S3 activates the PI3K/AKT/mTOR pathway to facilitate lipid metabolism, and its silencing reduced lipid droplet accumulation, free fatty acid levels, total cholesterol, and downregulated lipid metabolism-related genes | PMID:40555003 | Biochemical and biophysical research communications |
| 2008 | Low | Sigma subunits (σ1A, σ1B, σ1C) are essential for stability of human AP-1 complexes, demonstrated using the AP-2 complex as a model; however, no major alteration of stability, subcellular localization, or function of the AP-1 complex was observed in fibroblasts from a patient carrying an AP1S2 mutation, suggesting functional redundancy among AP-1 sigma subunit isoforms (σ1A/AP1S1, σ1B/AP1S2, σ1C/AP1S3) in peripheral tissues | PMID:18428203 | Human mutation |