title: ALIX binds a YPX(3)L motif of the GPCR PAR1 and mediates ubiquitin-independent ESCRT-III/MVB sorting.
abstract: The sorting of signaling receptors to lysosomes is an essential regulatory process in mammalian cells. During degradation, receptors are modified with ubiquitin and sorted by endosomal sorting complex required for transport (ESCRT)-0, -I, -II, and -III complexes into intraluminal vesicles (ILVs) of multivesicular bodies (MVBs). However, it remains unclear whether a single universal mechanism mediates MVB sorting of all receptors. We previously showed that protease-activated receptor 1 (PAR1), a G protein-coupled receptor (GPCR) for thrombin, is internalized after activation and sorted to lysosomes independent of ubiquitination and the ubiquitin-binding ESCRT components hepatocyte growth factor-regulated tyrosine kinase substrate and Tsg101. In this paper, we report that PAR1 sorted to ILVs of MVBs through an ESCRT-III-dependent pathway independent of ubiquitination. We further demonstrate that ALIX, a charged MVB protein 4-ESCRT-III interacting protein, bound to a YPX(3)L motif of PAR1 via its central V domain to mediate lysosomal degradation. This study reveals a novel MVB/lysosomal sorting pathway for signaling receptors that bypasses the requirement for ubiquitination and ubiquitin-binding ESCRTs and may be applicable to a subset of GPCRs containing YPX(n)L motifs.
authors.affiliation: Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA 92093, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Dores
authors.forename: Buxin
authors.initials: B
authors.lastname: Chen
authors.forename: Huilan
authors.initials: H
authors.lastname: Lin
authors.forename: Unice J K
authors.initials: UJ
authors.lastname: Soh
authors.forename: May M
authors.initials: MM
authors.lastname: Paing
authors.forename: William A
authors.initials: WA
authors.lastname: Montagne
authors.forename: Timo
authors.initials: T
authors.lastname: Meerloo
authors.forename: JoAnn
authors.initials: J
authors.lastname: Trejo
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D020816:Amino Acid Motifs; D015153:Blotting, Western; D002135:Calcium-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D056827:Endosomal Sorting Complexes Required for Transport / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011992:Endosomes / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D008247:Lysosomes / Q000378:metabolism; D057146:Multivesicular Bodies / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D044463:Receptor, PAR-1 / Q000235:genetics / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*; D054875:Ubiquitination; D025262:Vacuolar Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism
chemical_list: C481529:CHMP4A protein, human; C478397:CHMP4B protein, human; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D056827:Endosomal Sorting Complexes Required for Transport; C117020:PDCD6IP protein, human; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D044463:Receptor, PAR-1; D025801:Ubiquitin; D000251:Adenosine Triphosphatases; D025262:Vacuolar Proton-Translocating ATPases; D000074183:ATPases Associated with Diverse Cellular Activities; C490305:VPS4A protein, human; C490304:VPS4B protein, human