title: Arf6 negatively controls the rapid recycling of the β2 adrenergic receptor.
abstract: β2-adrenergic receptor (β2AR), a member of the GPCR (G-protein coupled receptor) family, is internalized in a ligand- and β-arrestin-dependent manner into early endosomes, and subsequently recycled back to the plasma membrane. Here, we report that β-arrestin promotes the activation of the small G protein Arf6, which regulates the recycling and degradation of β2AR. We demonstrate in vitro that the C-terminal region of β-arrestin1 interacts directly and simultaneously with Arf6GDP and its specific exchange factor EFA6, to promote Arf6 activation. Similarly, the ligand-mediated activation of β2AR leads to the formation of Arf6GTP in vivo in a β-arrestin-dependent manner. Expression of either EFA6 or an activated Arf6 mutant caused accumulation of β2AR in the degradation pathway. This phenotype could be rescued by the expression of an activated mutant of Rab4, suggesting that Arf6 acts upstream of Rab4. We propose a model in which Arf6 plays an essential role in β2AR desensitization. The ligand-mediated stimulation of β2AR relocates β-arrestin to the plasma membrane, and triggers the activation of Arf6 by EFA6. The activation of Arf6 leads to accumulation of β2AR in the degradation pathway, and negatively controls Rab4-dependent fast recycling to prevent the re-sensitization of β2AR.
authors.affiliation: Institut de Pharmacologie Moléculaire et Cellulaire, UMR 7275 CNRS-Université de Nice-Sophia Antipolis, 660 route des Lucioles, 06560 Valbonne,  France.
authors.forename: Eric
authors.initials: E
authors.lastname: Macia
authors.forename: Mariagrazia
authors.initials: M
authors.lastname: Partisani
authors.forename: Olivia
authors.initials: O
authors.lastname: Paleotti
authors.forename: Frederic
authors.initials: F
authors.lastname: Luton
authors.forename: Michel
authors.initials: M
authors.lastname: Franco
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D058666:Adrenergic beta-2 Receptor Agonists / Q000494:pharmacology; D000818:Animals; D019390:Arrestins / Q000737:chemistry / Q000378:metabolism; D055162:Biocatalysis / Q000187:drug effects; D002417:Cattle; D002451:Cell Compartmentation / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors; D006160:Guanosine Triphosphate / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D008024:Ligands; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D008954:Models, Biological; D009419:Nerve Tissue Proteins / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism*; D000071557:beta-Arrestins; D020695:rab4 GTP-Binding Proteins / Q000378:metabolism
chemical_list: D000089982:ADP-Ribosylation Factor 6; D058666:Adrenergic beta-2 Receptor Agonists; D019390:Arrestins; D020662:Guanine Nucleotide Exchange Factors; D008024:Ligands; D009419:Nerve Tissue Proteins; C109970:PSD protein, human; D018343:Receptors, Adrenergic, beta-2; D000071557:beta-Arrestins; D049452:Green Fluorescent Proteins; D006160:Guanosine Triphosphate; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; D020695:rab4 GTP-Binding Proteins; D007545:Isoproterenol