title: Agonist-mediated endocytosis of rat somatostatin receptor subtype 3 involves beta-arrestin and clathrin coated vesicles.
abstract: Agonist-induced endocytosis of somatostatin receptors determines subsequent cellular responsiveness to peptide agonist and influences somatostatin receptor scintigraphy, a technique to image various tumours. We examined the internalization of sst3HSV, an epitope-tagged type 3 somatostatin receptor, in transfected rat neuroendocrine insulinoma cells. Stimulation of these cells with somatostatin induced trafficking of coexpressed enhanced green fluorescence protein/beta-arrestin1 fusion protein and sst3HSV to colocalize in the same endocytic vesicles. Coexpression of a dominant negative mutant of the arrestin fusion protein with the receptor blocked the internalization of sst3HSV. Stimulation with somatostatin also induced the transient translocation of alpha-adaptin, a component of the adaptor protein complex 2, to the plasma membrane. alpha-adaptin and clathrin colocalized with the receptor. By electron microscopy, we observed internalized sst3 in clathrin coated pits, endosomes and at the limiting membrane of multivesicular bodies, a location typical for receptors being recycled. Concordantly, we observed sst3HSV colocalized with Rab11 in a perinuclear compartment which is likely to correspond to the pericentriolar recycling endosome. Thus, agonist-induced endocytosis of sst3 depends on its interaction with beta-arrestin, involves the adaptor protein complex 2 and proceeds via clathrin coated vesicles to the recycling compartment.
authors.affiliation: Deutsches Institut für Ernährungsforschung, Abteilung Molekulare Genetik und Universität Potsdam, Arthur-Schuenert-Allee 114-116, D-14558 Potsdam-Rehbrücke, Germany.
authors.forename: O J
authors.initials: OJ
authors.lastname: Kreuzer
authors.forename: B
authors.initials: B
authors.lastname: Krisch
authors.forename: O
authors.initials: O
authors.lastname: Déry
authors.forename: N W
authors.initials: NW
authors.lastname: Bunnett
authors.forename: W
authors.initials: W
authors.lastname: Meyerhof
mesh_terms: D033965:Adaptor Protein Complex alpha Subunits; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D019390:Arrestins / Q000235:genetics / Q000502:physiology*; D022163:Clathrin-Coated Vesicles / Q000502:physiology*; D004705:Endocytosis / Q000187:drug effects*; D011992:Endosomes / Q000737:chemistry / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D049452:Green Fluorescent Proteins; D007150:Immunohistochemistry; D007340:Insulinoma; D008164:Luminescent Proteins / Q000235:genetics; D008565:Membrane Proteins / Q000378:metabolism; D008854:Microscopy, Electron; D008870:Microtubules / Q000378:metabolism / Q000648:ultrastructure; D009154:Mutation; D010190:Pancreatic Neoplasms; D051381:Rats; D017481:Receptors, Somatostatin / Q000032:analysis / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013004:Somatostatin / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured; D000071557:beta-Arrestins; D020691:rab GTP-Binding Proteins / Q000032:analysis; D000099193:rab11 GTP-Binding Proteins
chemical_list: D033965:Adaptor Protein Complex alpha Subunits; D033942:Adaptor Proteins, Vesicular Transport; D019390:Arrestins; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D008565:Membrane Proteins; D017481:Receptors, Somatostatin; D011993:Recombinant Fusion Proteins; D013004:Somatostatin; D000071557:beta-Arrestins; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C103631:somatostatin receptor 3