AP-3 regulates PAR1 ubiquitin-independent MVB/lysosomal sorting via an ALIX-mediated pathway Journal Article

Authors: Dores, M. R.; Paing, M. M.; Lin, H; Montagne, W. A.; Marchese, A; Trejo, J.
Article Title: AP-3 regulates PAR1 ubiquitin-independent MVB/lysosomal sorting via an ALIX-mediated pathway
Abstract: The sorting of signaling receptors within the endocytic system is important for appropriate cellular responses. After activation, receptors are trafficked to early endosomes and either recycled or sorted to lysosomes and degraded. Most receptors trafficked to lysosomes are modified with ubiquitin and recruited into an endosomal subdomain enriched in hepatocyte growth factor-regulated tyrosine kinase substrate (HRS), a ubiquitin-binding component of the endosomal-sorting complex required for transport (ESCRT) machinery, and then sorted into intraluminal vesicles (ILVs) of multivesicular bodies (MVBs)/lysosomes. However, not all receptors use ubiquitin or the canonical ESCRT machinery to sort to MVBs/lysosomes. This is exemplified by protease-activated receptor-1 (PAR1), a G protein-coupled receptor for thrombin, which sorts to lysosomes independent of ubiquitination and HRS. We recently showed that the adaptor protein ALIX binds to PAR1, recruits ESCRT-III, and mediates receptor sorting to ILVs of MVBs. However, the mechanism that initiates PAR1 sorting at the early endosome is not known. We now report that the adaptor protein complex-3 (AP-3) regulates PAR1 ubiquitin-independent sorting to MVBs through an ALIX-dependent pathway. AP-3 binds to a PAR1 cytoplasmic tail-localized tyrosine-based motif and mediates PAR1 lysosomal degradation independent of ubiquitination. Moreover, AP-3 facilitates PAR1 interaction with ALIX, suggesting that AP-3 functions before PAR1 engagement of ALIX and MVB/lysosomal sorting.
Journal Title: Molecular biology of the cell
Volume: 23
Issue: 18
ISSN: 1939-4586; 1059-1524
Publisher: Unknown  
Journal Place: United States
Date Published: 2012
Start Page: 3612
End Page: 3623
Language: eng
Notes: LR: 20130712; GR: GM090690/GM/NIGMS NIH HHS/United States; GR: R01 GM090689/GM/NIGMS NIH HHS/United States; JID: 9201390; 0 (Adaptor Protein Complex 3); 0 (Adaptor Protein Complex delta Subunits); 0 (Calcium-Binding Proteins); 0 (Cell Cycle Proteins); 0 (Endosomal Sorting Complexes Required for Transport); 0 (PDCD6IP protein, human); 0 (Receptor, PAR-1); 0 (Ubiquitin); OID: NLM: PMC3442409; 2012/07/25 [aheadofprint]; ppublish