Multiple endocytic pathways of G protein-coupled receptors delineated by GIT1 sensitivity.
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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.
SubjectAdaptor Proteins, Signal Transducing
Cell Cycle Proteins
Receptor, Angiotensin, Type 1
Receptor, Angiotensin, Type 2
Receptor, Endothelin B
Receptors, Adrenergic, beta
Receptors, Cell Surface
Receptors, Opioid, mu
Receptors, Vasoactive Intestinal Peptide
Recombinant Fusion Proteins
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James B. Duke Distinguished Professor of Medicine
The focus of work in this laboratory is on the elucidation of the molecular properties and regulatory mechanisms controlling the function of G protein-coupled receptors. As model systems we utilize the so called adrenergic receptors for adrenaline and related molecules. The goal is to learn the general principles of signal transduction from the outside to the inside of the cell which are involved in systems as diverse as sensory perception, neuro- transmitter and hormonal signaling. Stud
Associate Professor in Medicine
Critical physiological events throughout the body are controlled by extracellular signals from neurotransmitters and hormones acting on cell surface receptors. Receptors transduce these signals to alter intracellular metabolism and cellular responsiveness through heterotrimeric G protein/second messenger pathways or through small GTP-binding protein/protein kinase cascades. The mechanisms that control the responsiveness of target organ G protein-coupled receptors include receptor ph
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Diversé-Pierluissi, M; Drazner, Mark H; Dyer, SL; Freedman, NJ; Lefkowitz, Robert J; Oppermann, M; Peppel, Karsten C (Proc Natl Acad Sci U S A, 1996-07-23)Guanine nucleotide-binding regulatory protein (G protein)-coupled receptor kinases (GRKs) constitute a family of serine/threonine kinases that play a major role in the agonist-induced phosphorylation and desensitization ...
Daaka, Y; Lefkowitz, Robert J; Pitcher, JA; Richardson, M; Robishaw, JD; Stoffel, RH (Proc Natl Acad Sci U S A, 1997-03-18)The G protein-coupled receptor (GPCR) kinases (GRKs) phosphorylate and desensitize agonist-occupied GPCRs. GRK2-mediated receptor phosphorylation is preceded by the agonist-dependent membrane association of this enzyme. ...
Direct evidence that Gi-coupled receptor stimulation of mitogen-activated protein kinase is mediated by G beta gamma activation of p21ras. Allen, LF; Hawes, BE; Koch, Walter J; Lefkowitz, Robert J (Proc Natl Acad Sci U S A, 1994-12-20)Stimulation of Gi-coupled receptors leads to the activation of mitogen-activated protein kinases (MAP kinases). In several cell types, this appears to be dependent on the activation of p21ras (Ras). Which G-protein subunit(s) ...