title: Transmembrane α-helix 2 and 7 are important for small molecule-mediated activation of the GLP-1 receptor.
abstract: Glucagon-like peptide-1 (GLP-1) activates the GLP-1 receptor (GLP-1R), which belongs to family B of the G-protein-coupled receptors. We previously identified a selective small molecule ligand, compound 2, that acted as a full agonist and allosteric modulator of GLP-1R. In this study, the structurally related small molecule, compound 3, stimulated cAMP production from GLP-1R, but not from the homologous glucagon receptor (GluR). The receptor selectivity encouraged a chimeric receptor approach to identify domains important for compound 3-mediated activation of GLP-1R. A subsegment of the GLP-1R transmembrane domain containing TM2 to TM5 was sufficient to transfer compound 3 responsiveness to GluR. Therefore, divergent residues in this subsegment of GLP-1R and GluR are responsible for the receptor selectivity of compound 3. Functional analyses of other chimeric receptors suggested that the existence of a helix-helix interface between TM1 and TM7 is important for the compound 3 response. Furthermore, site-directed mutagenesis revealed that a Phe195-Leu substitution in TM2 and a Thr391-Ala substitution in TM7 increased and decreased the efficacy of compound 3 without disturbing the potency or efficacy of GLP-1. Collectively, differential effects of receptor mutations suggest that TM2 and/or TM7 are important for compound 3-mediated activation of GLP-1R.
authors: Department of Incretin Biology, Novo Nordisk, Gentofte, Denmark.
authors: Christina
authors: C
authors: Rye Underwood
authors: Sanne
authors: S
authors: Møller Knudsen
authors: Birgitte
authors: B
authors: Schjellerup Wulff
authors: Hans
authors: H
authors: Bräuner-Osborne
authors: Jesper
authors: J
authors: Lau
authors: Lotte Bjerre
authors: LB
authors: Knudsen
authors: Günther H
authors: GH
authors: Peters
authors: Steffen
authors: S
authors: Reedtz-Runge
mesh_terms: D000242:Cyclic AMP / Q000378:metabolism; D005934:Glucagon / Q000378:metabolism; D052216:Glucagon-Like Peptide 1 / Q000378:metabolism; D000067757:Glucagon-Like Peptide-1 Receptor; D057809:HEK293 Cells; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D010446:Peptide Fragments / Q000378:metabolism; D017433:Protein Structure, Secondary; D018027:Receptors, Glucagon / Q000819:agonists* / Q000737:chemistry* / Q000378:metabolism
chemical_list: C000593833:GLP1R protein, human; D000067757:Glucagon-Like Peptide-1 Receptor; D008024:Ligands; D010446:Peptide Fragments; D018027:Receptors, Glucagon; C055453:glucagon-like peptide 1 (7-36)amide; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D000242:Cyclic AMP; C051322:glucagon-like peptide 1 (7-37)