title: The importance of the nine-amino acid C-terminal sequence of exendin-4 for binding to the GLP-1 receptor and for biological activity.
abstract: Exendin-4, a 39-amino acid (AA) peptide, is a long-acting agonist at the glucagon-like peptide-1 (GLP-1) receptor. Consequently, it may be preferable to GLP-1 as a long-term treatment for type 2 diabetes mellitus. Exendin-4 (Ex-4), unlike GLP-1, is not degraded by dipeptidyl peptidase IV (DPP IV), is less susceptible to degradation by neutral endopeptidase, and possesses a nine-AA C-terminal sequence absent from GLP-1. Here we examine the importance of these nine AAs for biological activity of Ex-4, a sequence of truncated Ex-4 analogs, and native GLP-1 and GLP-1 analogs to which all or parts of the C-terminal sequence have been added. We found that removing these AAs from Ex-4 to produce Ex (1-30) reduced the affinity for the GLP-1 receptor (GLP-1R) relative to Ex-4 (IC50: Ex-4, 3.22+/-0.9 nM; Ex (1-30), 32+/-5.8 nM) but made it comparable to that of GLP-1 (IC50: 44.9+/-3.2 nM). The addition of this nine-AA sequence to GLP-1 improved the affinity of both GLP-1 and the DPP IV resistant analog GLP-1 8-glycine for the GLP-1 receptor (IC50: GLP-1 Gly8 [GG], 220+/-23 nM; GLP-1 Gly8 Ex (31-39), 74+/-11 nM). Observations of the cAMP response in an insulinoma cell line show a similar trend for biological activity.
authors.affiliation: Diabetes Section, #23, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA.
authors.forename: Máire E
authors.initials: ME
authors.lastname: Doyle
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Theodorakis
authors.forename: Harold W
authors.initials: HW
authors.lastname: Holloway
authors.forename: Michel
authors.initials: M
authors.lastname: Bernier
authors.forename: Nigel H
authors.initials: NH
authors.lastname: Greig
authors.forename: Josephine M
authors.initials: JM
authors.lastname: Egan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D000077270:Exenatide; D000067757:Glucagon-Like Peptide-1 Receptor; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D018027:Receptors, Glucagon / Q000378:metabolism*; D014688:Venoms / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000067757:Glucagon-Like Peptide-1 Receptor; D007328:Insulin; D010455:Peptides; D018027:Receptors, Glucagon; D014688:Venoms; D000077270:Exenatide