ALIX Regulates the Ubiquitin-Independent Lysosomal Sorting of the P2Y1 Purinergic Receptor via a YPX3L Motif.
Endocytic sorting and lysosomal degradation are integral to the regulation of G protein-coupled receptor (GPCR) function. Upon ligand binding, classical GPCRs are activated, internalized and recycled or sorted to lysosomes for degradation, a process that requires receptor ubiquitination. However, recent studies have demonstrated that numerous GPCRs are sorted to lysosomes independent of receptor ubiquitination. Here, we describe an ubiquitin-independent lysosomal sorting pathway for the purinergic GPCR P2Y1. After activation, P2Y1 sorts to lysosomes for degradation independent of direct ubiquitination that is mediated by a YPX3L motif within the second intracellular loop that serves as a binding site for the adaptor protein ALIX. Depletion of ALIX or site-directed mutation of the YPX3L motif inhibits P2Y1 sorting into the lumen of multivesicular endosomes/lysosomes and degradation. These findings confirm the function of YPX3L motifs as lysosomal targeting sequences for GPCRs and demonstrate that ALIX mediates the ubiquitin-independent degradation of certain GPCRs.
Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA 92093, United States of America.|Department of Biology, Hofstra University, Hempstead, NY 11549, United States of America.
Michael R
MR
Dores
Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA 92093, United States of America.
Neil J
NJ
Grimsey
Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA 92093, United States of America.
Francisco
F
Mendez
Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA 92093, United States of America.
JoAnn
J
Trejo
D000074183:ATPases Associated with Diverse Cellular Activities; D020816:Amino Acid Motifs; D000818:Animals; D002135:Calcium-Binding Proteins / Q000032:analysis / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000032:analysis / Q000378:metabolism*; D056827:Endosomal Sorting Complexes Required for Transport / Q000032:analysis / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008247:Lysosomes / Q000378:metabolism*; D011489:Protein Denaturation; D058472:Receptors, Purinergic P2Y1 / Q000032:analysis / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*; D054875:Ubiquitination; D025262:Vacuolar Proton-Translocating ATPases / Q000032:analysis / Q000378:metabolism
D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D056827:Endosomal Sorting Complexes Required for Transport; C117020:PDCD6IP protein, human; D058472:Receptors, Purinergic P2Y1; D025801:Ubiquitin; D025262:Vacuolar Proton-Translocating ATPases; D000074183:ATPases Associated with Diverse Cellular Activities; C490305:VPS4A protein, human