Second extracellular loop of human glucagon-like peptide-1 receptor (GLP-1R) differentially regulates orthosteric but not allosteric agonist binding and function


The glucagon-like peptide-1 receptor (GLP-1R) is a prototypical family B G protein-coupled receptor that exhibits physiologically important pleiotropic coupling and ligand-dependent signal bias. In our accompanying article (Koole, C., Wootten, D., Simms, J., Miller, L. J., Christopoulos, A., and Sexton, P. M. (2012) J. Biol. Chem. 287, 3642-3658), we demonstrate, through alanine-scanning mutagenesis, a key role for extracellular loop (ECL) 2 of the receptor in propagating activation transition mediated by GLP-1 peptides that occurs in a peptide- and pathway-dependent manner for cAMP formation, intracellular (Ca 2+ i) mobilization, and phosphorylation of extracellular signal-regulated kinases 1 and 2 (pERK1/2). In this study, we examine the effect of ECL2 mutations on the binding and signaling of the peptide mimetics, exendin-4 and oxyntomodulin, as well as small molecule allosteric agonist 6,7-dichloro-2-methylsulfonyl-3-tert-butylaminoquinoxaline (compound 2). Lys-288, Cys-296, Trp-297, and Asn-300 were globally important for peptide signaling and also had critical roles in governing signal bias of the receptor. Peptide-specific effects on relative efficacy and signal bias were most commonly observed for residues 301-305, although R299A mutation also caused significantly different effects for individual peptides. Met-303 was more important for exendin-4 and oxyntomodulin action than those of GLP-1 peptides. Globally, ECL2 mutation was more detrimental to exendin-4-mediated Ca 2+ i release than GLP-1(7-36)-NH 2, providing additional evidence for subtle differences in receptor activation by these two peptides. Unlike peptide activation of the GLP-1R, ECL2 mutations had only limited impact on compound 2 mediated cAMP and pERK responses, consistent with this ligand having a distinct mechanism for receptor activation. These data suggest a critical role of ECL2 of the GLP-1R in the activation transition of the receptor by peptide agonists.

Publication DOI:
Divisions: College of Health & Life Sciences > School of Biosciences
College of Health & Life Sciences
Additional Information: © 2012 by The American Society for Biochemistry and Molecular Biology, Inc.
Uncontrolled Keywords: Biochemistry,Molecular Biology,Cell Biology
Publication ISSN: 1083-351X
Last Modified: 20 May 2024 07:33
Date Deposited: 05 Sep 2019 11:00
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Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL)
http://www.jbc. ... tent/287/6/3659 (Publisher URL)
PURE Output Type: Article
Published Date: 2012-02-03
Authors: Koole, Cassandra
Wootten, Denise
Simms, John (ORCID Profile 0000-0002-4675-0902)
Savage, Emilia E.
Miller, Laurence J.
Christopoulos, Arthur
Sexton, Patrick M.



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