title: Functional consequences of glucagon-like peptide-1 receptor cross-talk and trafficking.
abstract: The signaling capacity of seven-transmembrane/G-protein-coupled receptors (7TM/GPCRs) can be regulated through ligand-mediated receptor trafficking. Classically, the recycling of internalized receptors is associated with resensitization, whereas receptor degradation terminates signaling. We have shown previously that the incretin glucagon-like peptide-1 receptor (GLP-1R) internalizes fast and is primarily resensitized through recycling back to the cell surface. GLP-1R is expressed in pancreatic islets together with the closely related glucose-dependent insulinotropic polypeptide (GIPR) and glucagon (GCGR) receptors. The interaction and cross-talk between coexpressed receptors is a wide phenomenon of the 7TM/GPCR superfamily. Numerous reports show functional consequences for signaling and trafficking of the involved receptors. On the basis of the high structural similarity and tissue coexpression, we here investigated the potential cross-talk between GLP-1R and GIPR or GCGR in both trafficking and signaling pathways. Using a real-time time-resolved FRET-based internalization assay, we show that GLP-1R, GIPR, and GCGR internalize with differential properties. Remarkably, upon coexpression of the internalizing GLP-1R and the non-internalizing GIPR, GLP-1-mediated GLP-1R internalization was impaired in a GIPR concentration-dependent manner. As a functional consequence of such impaired internalization capability, GLP-1-mediated GLP-1R signaling was abrogated. A similar compromised signaling was found when GLP-1R internalization was abrogated by a dominant-negative version of dynamin (dynamin-1 K44E), which provides a mechanistic link between GLP-1R trafficking and signaling. This study highlights the importance of receptor internalization for full functionality of GLP-1R. Moreover, cross-talk between the two incretin receptors GLP-1R and GIPR is shown to alter receptor trafficking with functional consequences for GLP-1R signaling.
authors.affiliation: From the Department of Incretin Biology, Novo Nordisk A/S, 2760 Maaloev and snro@novonordisk.com sarah_roed@hotmail.com.
authors.forename: Sarah Noerklit
authors.initials: SN
authors.lastname: Roed
authors.affiliation: the Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, DK-1165 Copenhagen, Denmark.
authors.forename: Anne Cathrine
authors.initials: AC
authors.lastname: Nøhr
authors.affiliation: From the Department of Incretin Biology, Novo Nordisk A/S, 2760 Maaloev and.
authors.forename: Pernille
authors.initials: P
authors.lastname: Wismann
authors.affiliation: From the Department of Incretin Biology, Novo Nordisk A/S, 2760 Maaloev and.
authors.forename: Helle
authors.initials: H
authors.lastname: Iversen
authors.affiliation: the Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, DK-1165 Copenhagen, Denmark.
authors.forename: Hans
authors.initials: H
authors.lastname: Bräuner-Osborne
authors.affiliation: From the Department of Incretin Biology, Novo Nordisk A/S, 2760 Maaloev and.
authors.forename: Sanne Moeller
authors.initials: SM
authors.lastname: Knudsen
authors.affiliation: From the Department of Incretin Biology, Novo Nordisk A/S, 2760 Maaloev and.
authors.forename: Maria
authors.initials: M
authors.lastname: Waldhoer
mesh_terms: D003924:Diabetes Mellitus, Type 2 / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D034284:Dynamin I / Q000378:metabolism; D005749:Gastric Inhibitory Polypeptide / Q000378:metabolism; D005786:Gene Expression Regulation; D005934:Glucagon / Q000378:metabolism; D000067757:Glucagon-Like Peptide-1 Receptor; D057809:HEK293 Cells; D006801:Humans; D054795:Incretins / Q000378:metabolism; D007515:Islets of Langerhans / Q000378:metabolism / Q000473:pathology; D008024:Ligands; D021381:Protein Transport; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D018027:Receptors, Glucagon / Q000096:biosynthesis / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics
chemical_list: C000593833:GLP1R protein, human; D000067757:Glucagon-Like Peptide-1 Receptor; D054795:Incretins; D008024:Ligands; D043562:Receptors, G-Protein-Coupled; D018027:Receptors, Glucagon; C450520:seven-transmembrane G-protein-coupled receptor; D005749:Gastric Inhibitory Polypeptide; D005934:Glucagon; D034284:Dynamin I
keywords: Fluorescence Resonance Energy Transfer (FRET); G-protein-coupled Receptor (GPCR); Glucagon-like Peptide-1; Glucose-dependent Insulinotropic Polypeptide; Intracellular Trafficking; Receptor Cross-talk; Receptor Internalization; Seven Transmembrane-spanning Receptor; Signal Transduction; Type 2 Diabetes