title: Multiple endocytic pathways of G protein-coupled receptors delineated by GIT1 sensitivity.
abstract: Recently, we identified a GTPase-activating protein for the ADP ribosylation factor family of small GTP-binding proteins that we call GIT1. This protein initially was identified as an interacting partner for the G protein-coupled receptor kinases, and its overexpression was found to affect signaling and internalization of the prototypical beta(2)-adrenergic receptor. Here, we report that GIT1 overexpression regulates internalization of numerous, but not all, G protein-coupled receptors. The specificity of the GIT1 effect is not related to the type of G protein to which a receptor couples, but rather to the endocytic route it uses. GIT1 only affects the function of G protein-coupled receptors that are internalized through the clathrin-coated pit pathway in a beta-arrestin- and dynamin-sensitive manner. Furthermore, the GIT1 effect is not limited to G protein-coupled receptors because overexpression of this protein also affects internalization of the epidermal growth factor receptor. However, constitutive agonist-independent internalization is not regulated by GIT1, because transferrin uptake is not affected by GIT1 overexpression. Thus, GIT1 is a protein involved in regulating the function of signaling receptors internalized through the clathrin pathway and can be used as a diagnostic tool for defining the endocytic pathway of a receptor.
authors.affiliation: The Howard Hughes Medical Institute and Departments of Medicine, Biochemistry, and Cell Biology, Box 3821, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: A
authors.initials: A
authors.lastname: Claing
authors.forename: S J
authors.initials: SJ
authors.lastname: Perry
authors.forename: M
authors.initials: M
authors.lastname: Achiriloaie
authors.forename: J K
authors.initials: JK
authors.lastname: Walker
authors.forename: J P
authors.initials: JP
authors.lastname: Albanesi
authors.forename: R J
authors.initials: RJ
authors.lastname: Lefkowitz
authors.forename: R T
authors.initials: RT
authors.lastname: Premont
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D019556:COS Cells; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D000242:Cyclic AMP / Q000502:physiology; D004705:Endocytosis / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000502:physiology*; D020690:GTPase-Activating Proteins / Q000502:physiology*; D006801:Humans; D010750:Phosphoproteins; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D044023:Receptor, Endothelin B; D011943:Receptors, Adrenergic, beta / Q000502:physiology; D011945:Receptors, Angiotensin / Q000502:physiology; D011956:Receptors, Cell Surface / Q000502:physiology*; D017466:Receptors, Endothelin / Q000502:physiology; D011976:Receptors, Muscarinic / Q000502:physiology; D017450:Receptors, Opioid, mu / Q000502:physiology; D018005:Receptors, Vasoactive Intestinal Peptide / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000502:physiology; D014162:Transfection
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; C485647:GIT1 protein, human; D020690:GTPase-Activating Proteins; D010750:Phosphoproteins; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D044023:Receptor, Endothelin B; D011943:Receptors, Adrenergic, beta; D011945:Receptors, Angiotensin; D011956:Receptors, Cell Surface; D017466:Receptors, Endothelin; D011976:Receptors, Muscarinic; D017450:Receptors, Opioid, mu; D018005:Receptors, Vasoactive Intestinal Peptide; D011993:Recombinant Fusion Proteins; D000242:Cyclic AMP; D019204:GTP-Binding Proteins