title: N-terminal tyrosine modulation of the endocytic adaptor function of the beta-arrestins.
abstract: The highly homologous beta-arrestin1 and -2 adaptor proteins play important roles in the function of G protein-coupled receptors. Either beta-arrestin variant can function as a molecular chaperone for clathrin-mediated receptor internalization. This role depends primarily upon two distinct, contiguous C-terminal beta-arrestin motifs recognizing clathrin and the beta-adaptin subunit of AP2. However, a molecular basis is lacking to explain the different endocytic efficacies of the two beta-arrestin isoforms and the observation that beta-arrestin N-terminal substitution mutants can act as dominant negative inhibitors of receptor endocytosis. Despite the near identity of the beta-arrestins throughout their N termini, sequence variability is present at a small number of residues and includes tyrosine to phenylalanine substitutions. Here we show that corresponding N-terminal (Y/F)VTL sequences in beta-arrestin1 and -2 differentially regulate mu-adaptin binding. Our results indicate that the beta-arrestin1 Tyr-54 lessens the interaction with mu-adaptin and moreover is a Src phosphorylation site. A gain of endocytic function is obtained with the beta-arrestin1 Y54F substitution, which improves both the beta-arrestin1 interaction with mu-adaptin and the ability to enhance beta2-adrenergic receptor internalization. These data indicate that beta-arrestin2 utilizes mu-adaptin as an endocytic partner, and that the inability of beta-arrestin1 to sustain a similar degree of interaction with mu-adaptin may result from coordination of Tyr-54 by neighboring residues or its modification by Src kinase. Additionally, these naturally occurring variations in beta-arrestins may also differentially regulate the composition of the signaling complexes organized on the receptor.
authors: Department of Cell Biology, Duke University, Durham, North Carolina 27710, USA.
authors: Sébastien
authors: S
authors: Marion
authors: Gregory B
authors: GB
authors: Fralish
authors: Stéphane
authors: S
authors: Laporte
authors: Marc G
authors: MG
authors: Caron
authors: Larry S
authors: LS
authors: Barak
mesh_terms: D033983:Adaptor Protein Complex mu Subunits / Q000378:metabolism; D033942:Adaptor Proteins, Vesicular Transport / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D019390:Arrestins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002460:Cell Line; D022163:Clathrin-Coated Vesicles / Q000378:metabolism*; D006801:Humans; D007668:Kidney / Q000166:cytology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010649:Phenylalanine / Q000235:genetics; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D051381:Rats; D022161:Transport Vesicles / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism*; D000071557:beta-Arrestins; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D033983:Adaptor Protein Complex mu Subunits; D033942:Adaptor Proteins, Vesicular Transport; D019390:Arrestins; D000071557:beta-Arrestins; D014443:Tyrosine; D010649:Phenylalanine; D019061:src-Family Kinases