title: Different domains of the glucagon and glucagon-like peptide-1 receptors provide the critical determinants of ligand selectivity.
abstract: (1) Glucagon and glucagon-like peptide-1 (GLP-1) are homologous peptide hormones with important functions in glucose metabolism. The receptors for glucagon and GLP-1 are homologous family B G-protein coupled receptors. The GLP-1 receptor amino-terminal extracellular domain is a major determinant of glucagon/GLP-1 selectivity of the GLP-1 receptor. However, the divergent residues in glucagon and GLP-1 that determine specificity for the GLP-1 receptor amino-terminal extracellular domain are not known. Less is known about how the glucagon receptor distinguishes between glucagon and GLP-1. (2) We analysed chimeric glucagon/GLP-1 peptides for their ability to bind and activate the glucagon receptor, the GLP-1 receptor and chimeric glucagon/GLP-1 receptors. The chimeric peptide GLP-1(7-20)/glucagon(15-29) was unable to bind and activate the glucagon receptor. Substituting the glucagon receptor core domain with the GLP-1 receptor core domain (chimera A) completely rescued the affinity and potency of GLP-1(7-20)/glucagon(15-29) without compromising the affinity and potency of glucagon. Substituting transmembrane segment 1 (TM1), TM6, TM7, the third extracellular loop and the intracellular carboxy-terminus of chimera A with the corresponding glucagon receptor segments re-established the ability to distinguish GLP-1(7-20)/glucagon(15-29) from glucagon. Corroborant results were obtained with the opposite chimeric peptide glucagon(1-14)/GLP-1(21-37). (3) The results suggest that the glucagon and GLP-1 receptor amino-terminal extracellular domains determine specificity for the divergent residues in the glucagon and GLP-1 carboxy-terminals respectively. The GLP-1 receptor core domain is not a critical determinant of glucagon/GLP-1 selectivity. Conversely, the glucagon receptor core domain contains two or more sub-segments which strongly determine specificity for divergent residues in the glucagon amino-terminus.
authors.affiliation: Molecular Pharmacology, Novo Nordisk, DK-2760 Maaloev, Denmark.
authors.forename: S
authors.initials: S
authors.lastname: Runge
authors.forename: B S
authors.initials: BS
authors.lastname: Wulff
authors.forename: K
authors.initials: K
authors.lastname: Madsen
authors.forename: H
authors.initials: H
authors.lastname: Bräuner-Osborne
authors.forename: L B
authors.initials: LB
authors.lastname: Knudsen
mesh_terms: D000595:Amino Acid Sequence; D001667:Binding, Competitive / Q000235:genetics / Q000502:physiology; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D000067757:Glucagon-Like Peptide-1 Receptor; D006801:Humans; D008024:Ligands; D008969:Molecular Sequence Data; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D017434:Protein Structure, Tertiary; D018027:Receptors, Glucagon / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: C000593833:GLP1R protein, human; D000067757:Glucagon-Like Peptide-1 Receptor; D008024:Ligands; D018027:Receptors, Glucagon; D011993:Recombinant Fusion Proteins