title: High potency antagonists of the pancreatic glucagon-like peptide-1 receptor.
abstract: GLP-1-(7-36)-amide and exendin-4-(1-39) are glucagon-like peptide-1 (GLP-1) receptor agonists, whereas exendin-(9-39) is the only known antagonist. To analyze the transition from agonist to antagonist and to identify the amino acid residues involved in ligand activation of the GLP-1 receptor, we used exendin analogs with successive N-terminal truncations. Chinese hamster ovary cells stably transfected with the rat GLP-1 receptor were assayed for changes in intracellular cAMP caused by the test peptides in the absence or presence of half-maximal stimulatory doses of GLP-1. N-terminal truncation of a single amino acid reduced the agonist activity of the exendin peptide, whereas N-terminal truncation of 3-7 amino acids produced antagonists that were 4-10-fold more potent than exendin-(9-39). N-terminal truncation of GLP-1 by 2 amino acids resulted in weak agonist activity, but an 8-amino acid N-terminal truncation inactivated the peptide. Binding studies performed using 125I-labeled GLP-1 confirmed that all bioactive peptides specifically displaced tracer with high potency. In a set of exendin/GLP-1 chimeric peptides, substitution of GLP-1 sequences into exendin-(3-39) produced loss of antagonist activity with conversion to a weak agonist. The results show that receptor binding and activation occur in separate domains of exendin, but they are more closely coupled in GLP-1.
authors.affiliation: Laboratory of Clinical Physiology, NIA, National Institutes of Health, Baltimore, Maryland 21224, USA.
authors.forename: C
authors.initials: C
authors.lastname: Montrose-Rafizadeh
authors.forename: H
authors.initials: H
authors.lastname: Yang
authors.forename: B D
authors.initials: BD
authors.lastname: Rodgers
authors.forename: A
authors.initials: A
authors.lastname: Beday
authors.forename: L A
authors.initials: LA
authors.lastname: Pritchette
authors.forename: J
authors.initials: J
authors.lastname: Eng
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D016466:CHO Cells; D006224:Cricetinae; D000242:Cyclic AMP / Q000378:metabolism; D000077270:Exenatide; D005768:Gastrointestinal Hormones / Q000737:chemistry*; D005934:Glucagon; D052216:Glucagon-Like Peptide 1; D000067757:Glucagon-Like Peptide-1 Receptor; D004763:Glucagon-Like Peptides; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D051381:Rats; D018027:Receptors, Glucagon / Q000819:agonists* / Q000037:antagonists & inhibitors*; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D017384:Sequence Deletion; D013329:Structure-Activity Relationship; D014162:Transfection; D014688:Venoms / Q000737:chemistry*
chemical_list: D005768:Gastrointestinal Hormones; C000593835:Glp1r protein, rat; D000067757:Glucagon-Like Peptide-1 Receptor; D010446:Peptide Fragments; D010455:Peptides; D018027:Receptors, Glucagon; D011993:Recombinant Fusion Proteins; D014688:Venoms; C055453:glucagon-like peptide 1 (7-36)amide; C083773:exendin (9-39); D004763:Glucagon-Like Peptides; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D000077270:Exenatide; D000242:Cyclic AMP