title: Intracellular trafficking of interleukin-1 receptor I requires Tollip.
abstract: Interleukin-1 receptor (IL-1RI) is a master regulator of inflammation and innate immunity. When triggered by IL-1beta, IL-1RI aggregates with IL-1R-associated protein (IL-1RAcP) and forms a membrane proximal signalosome that potently activates downstream signaling cascades. IL-1beta also rapidly triggers endocytosis of IL-1RI. Although internalization of IL-1RI significantly impacts signaling, very little is known about trafficking of IL-1RI and therefore about precisely how endocytosis modulates the overall cellular response to IL-1beta. Upon internalization, activated receptors are often sorted through endosomes and delivered to lysosomes for degradation. This is a highly regulated process that requires ubiquitination of cargo proteins as well as protein-sorting complexes that specifically recognize ubiquitinated cargo. Here, we show that IL-1beta induces ubiquitination of IL-1RI and that via these attached ubiquitin groups, IL-1RI interacts with the ubiquitin-binding protein Tollip. By using an assay to follow trafficking of IL-1RI from the cell surface to late endosomes and lysosomes, we demonstrate that Tollip is required for sorting of IL-1RI at late endosomes. In Tollip-deficient cells and cells expressing only mutated Tollip (incapable of binding IL-1RI and ubiquitin), IL-1RI accumulates on late endosomes and is not efficiently degraded. Furthermore, we show that IL-1RI interacts with Tom1, an ubiquitin-, clathrin-, and Tollip-binding protein, and that Tom1 knockdown also results in the accumulation of IL-1RI at late endosomes. Our findings suggest that Tollip functions as an endosomal adaptor linking IL-1RI, via Tom1, to the endosomal degradation machinery.
authors.affiliation: Department of Biochemistry, University of Lausanne, BIL Biomedical Research Center, Chemin des Boveresses 155, CH-1066 Epalinges, Switzerland.
authors.forename: Brian
authors.initials: B
authors.lastname: Brissoni
authors.forename: Laetitia
authors.initials: L
authors.lastname: Agostini
authors.forename: Michel
authors.initials: M
authors.lastname: Kropf
authors.forename: Fabio
authors.initials: F
authors.lastname: Martinon
authors.forename: Valentin
authors.initials: V
authors.lastname: Swoboda
authors.forename: Saskia
authors.initials: S
authors.lastname: Lippens
authors.forename: Helen
authors.initials: H
authors.lastname: Everett
authors.forename: Natalia
authors.initials: N
authors.lastname: Aebi
authors.forename: Sophie
authors.initials: S
authors.lastname: Janssens
authors.forename: Etienne
authors.initials: E
authors.lastname: Meylan
authors.forename: Michela
authors.initials: M
authors.lastname: Felberbaum-Corti
authors.forename: Harald
authors.initials: H
authors.lastname: Hirling
authors.forename: Jean
authors.initials: J
authors.lastname: Gruenberg
authors.forename: Jürg
authors.initials: J
authors.lastname: Tschopp
authors.forename: Kimberly
authors.initials: K
authors.lastname: Burns
mesh_terms: D000818:Animals; D015180:Electrophoresis, Gel, Two-Dimensional; D004705:Endocytosis / Q000502:physiology*; D066246:ErbB Receptors / Q000378:metabolism; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D047468:Immunoprecipitation; D053583:Interleukin-1beta / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008856:Microscopy, Fluorescence; D021381:Protein Transport / Q000502:physiology; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D053573:Receptors, Interleukin-1 Type I / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D053583:Interleukin-1beta; D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; D053573:Receptors, Interleukin-1 Type I; C410602:TOLLIP protein, human; C120296:TOM1 protein, human; D025801:Ubiquitin; D066246:ErbB Receptors