Exchange of W39 by A within the N-terminal extracellular domain of the GLP-1 receptor results in a loss of receptor function.
The proglucagon-derived glucagon-like peptide-1 (GLP-1) secreted by the L-cells exerts an insulinotropic effect at pancreatic beta-cells. The GLP-1 receptor belongs to a new subfamily of the superfamily of seven transmembrane, G-protein-coupled receptors (7 TM receptors). We show that a single point mutation within a nonconserved motif of the N-terminal, extracellular domain of the GLP-1 receptor results in a dramatic impairment of receptor function. Thus, substitution of W39 by A or F is followed by a loss of GLP-1 binding. Exchange of K38 with A (mutant K) slightly decreased GLP-1 binding affinity. Replacement of the negatively charged Q37 by K and K38 by A, which is identical with a shift of the positively charged K one position upstream, resulted in a receptor mutant able to bind GLP-1 with higher affinity as the wild-type receptor and mutant K. Therefore, the presence of an imidazol ring structure in the investigated receptor region is necessary for an intact receptor function Furthermore, a positive charge at this location is important for the receptor-ligand interaction.
Van Eyll
B
B
Clinical Research Group for Gastrointestinal Endocrinology, Philipps-University of Marburg, Germany.
Göke
B
B
Wilmen
A
A
Göke
R
R
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D000242:Cyclic AMP / Q000378:metabolism; D005934:Glucagon / Q000378:metabolism / Q000494:pharmacology; D052216:Glucagon-Like Peptide 1; D000067757:Glucagon-Like Peptide-1 Receptor; D007700:Kinetics; D008214:Lymphocytes; D008961:Models, Structural; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology; D017354:Point Mutation; D011498:Protein Precursors / Q000378:metabolism / Q000494:pharmacology; D017433:Protein Structure, Secondary; D018027:Receptors, Glucagon / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D014162:Transfection
D000067757:Glucagon-Like Peptide-1 Receptor; D010446:Peptide Fragments; D011498:Protein Precursors; D018027:Receptors, Glucagon; D011994:Recombinant Proteins; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D000242:Cyclic AMP