title: Ubiquitylation and activation of a Rab GTPase is promoted by a β₂AR-HACE1 complex.
abstract: We and others have shown that trafficking of G-protein-coupled receptors is regulated by Rab GTPases. Cargo-mediated regulation of vesicular transport has received great attention lately. Rab GTPases, which form the largest branch of the Ras GTPase superfamily, regulate almost every step of vesicle-mediated trafficking. Rab GTPases are well-recognized targets of human diseases but their regulation and the mechanisms connecting them to cargo proteins are still poorly understood. Here, we show by overexpression and depletion studies that HACE1, a HECT-domain-containing ubiquitin ligase, promotes the recycling of the β₂-adrenergic receptor (β₂AR), a prototypical G-protein-coupled receptor, through a Rab11a-dependent mechanism. Interestingly, the β₂AR in conjunction with HACE1 triggered ubiquitylation of Rab11a, as observed by western blot analysis. LC-MS/MS experiments determined that Rab11a is ubiquitylated on Lys145. A Rab11a-K145R mutant failed to undergo β₂AR-HACE1-induced ubiquitylation and inhibited the HACE1-mediated recycling of the β₂AR. Rab11a, but not Rab11a-K145R, was activated by β₂AR-HACE1, indicating that ubiquitylation of Lys145 is involved in activation of Rab11a. Co-expression of β₂AR-HACE1 also potentiated ubiquitylation of Rab6a and Rab8a, but not of other Rab GTPases that were tested. We report a novel regulatory mechanism of Rab GTPases through their ubiquitylation, with associated functional effects demonstrated on Rab11a. This suggests a new pathway whereby a cargo protein, such as a G-protein-coupled receptor, can regulate its own trafficking by inducing the ubiquitylation and activation of a Rab GTPase.
authors.affiliation: Service de Rhumatologie, Département de Médecine, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, the Centre de Recherche Clinique Étienne-Le Bel, Sherbrooke, QC J1H 5N4, Canada.
authors.forename: Véronik
authors.initials: V
authors.lastname: Lachance
authors.forename: Jade
authors.initials: J
authors.lastname: Degrandmaison
authors.forename: Sébastien
authors.initials: S
authors.lastname: Marois
authors.forename: Mélanie
authors.initials: M
authors.lastname: Robitaille
authors.forename: Samuel
authors.initials: S
authors.lastname: Génier
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Nadeau
authors.forename: Stéphane
authors.initials: S
authors.lastname: Angers
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Parent
mesh_terms: D000595:Amino Acid Sequence; D001120:Arginine / Q000378:metabolism; D004789:Enzyme Activation; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D008239:Lysine / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D021381:Protein Transport; D018343:Receptors, Adrenergic, beta-2 / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D044767:Ubiquitin-Protein Ligases / Q000235:genetics* / Q000378:metabolism; D054875:Ubiquitination; D020691:rab GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D000099193:rab11 GTP-Binding Proteins
chemical_list: D001120:Arginine; D008239:Lysine; D018343:Receptors, Adrenergic, beta-2; D044767:Ubiquitin-Protein Ligases; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C094135:Rab6 protein; C497506:HACE1 protein, human; C082377:RAB8A protein, human
keywords: G-protein-coupled receptor; GPCR; Rab; Trafficking