title: Carboxyl-terminal domains in the avian beta 1-adrenergic receptor that regulate agonist-promoted endocytosis.
abstract: Most G protein-coupled receptors, including the mammalian beta 2-adrenergic receptor, are endocytosed to an intracellular, vesicular compartment upon continued exposure to agonist. The long form of the avian beta 1-adrenergic receptor, which contains a carboxyl-terminal 59-amino acid extension, does not undergo agonist-promoted endocytosis. We constructed and expressed turkey beta 1-adrenergic receptor cDNAs with regularly spaced carboxyl-terminal truncations and studied their agonist-promoted endocytosis. Removal of 34-86 amino acids from the carboxyl terminus of the turkey receptor allowed its efficient endocytosis, with optimal endocytosis observed upon removal of 59 residues. Removal of only 18 residues allowed some endocytosis. A receptor that lacks the entire carboxyl-terminal region (124 residues) was not endocytosed. We also constructed a chimeric hamster beta 2-adrenergic receptor with the added 59-residue carboxyl-terminal domain of the turkey receptor. The chimera was not significantly endocytosed. These data indicate that residues 450-465 in the carboxyl-terminal region of the beta 1-adrenergic receptor can act independently to block agonist-promoted endocytosis and that other carboxyl-terminal structures nearer to the seventh membrane span are required for endocytosis.
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas 75235-9041.
authors.forename: E M
authors.initials: EM
authors.lastname: Parker
authors.forename: P
authors.initials: P
authors.lastname: Swigart
authors.forename: M H
authors.initials: MH
authors.lastname: Nunnally
authors.forename: J P
authors.initials: JP
authors.lastname: Perkins
authors.forename: E M
authors.initials: EM
authors.lastname: Ross
mesh_terms: D000818:Animals; D004705:Endocytosis; D020120:Iodocyanopindolol; D007545:Isoproterenol / Q000494:pharmacology; D051379:Mice; D010446:Peptide Fragments / Q000502:physiology*; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D011412:Propanolamines / Q000378:metabolism; D018342:Receptors, Adrenergic, beta-1 / Q000502:physiology*; D014422:Turkeys
chemical_list: D010446:Peptide Fragments; D011412:Propanolamines; D018342:Receptors, Adrenergic, beta-1; D020120:Iodocyanopindolol; D010869:Pindolol; D007545:Isoproterenol; C033394:CGP 12177