Structural Determinants of Binding the Seven-transmembrane Domain of the Glucagon-like Peptide-1 Receptor (GLP-1R)

Abstract

The glucagon-like peptide 1 receptor (GLP-1R) 6 and the glucagon receptor (GCGR) are class B G protein-coupled receptors (GPCRs) involved in insulin release and glucose homeostasis, respectively. Accordingly, they have attracted extensive attention for their importance as targets for therapeutic intervention of type 2 diabetes (1, 2). Class B GPCRs consist of an N-terminal extracellular domain (ECD) linked to a seven-transmembrane helical (7TM) region. Studies examining truncated, chimeric, and mutated ligand and receptor variants together with multiple ligand-bound ECD crystal structures and two class B 7TM domain crystal structures are consistent with a "two-domain" binding mechanism for peptide hormone ligands to the secretin-like class B GPCRs (3-5). According to this peptide ligand binding mechanism, the C terminus of the peptide hormone forms an initial complex with the ECD, allowing the N terminus of the ligand to interact with the 7TM domain. It is the N-terminal interactions that ultimately result in activation of the receptor and stimulation of downstream coupling to G proteins and other effectors that mediate intra-*

Cryo-EM structure of the activated GLP-1 receptor in complex with a G protein

“…2c). Thus, ECL2 plays a prominent role in GLP-1 binding, in agreement with previous studies 20, 21, 28 . Towards the peptide C-terminus, we observe W31 p interacting with ECL1, packing against residues Q211 and H212 (Fig.…”

Structural insights into ligand efficacy and activation of the glucagon receptor

“…This polar interaction is also present in previously determined GLP-1:G s complex structures and in fact alanine mutation of R378 7.35 completely inhibits GCGR-mediated cAMP signaling (Fig. 2c) 12,13,23 , thus highlighting the importance of this interaction for ligand-dependent activation within receptors of the glucagon family. The altered position of TM7 is accompanied by movement of ECL3 towards the receptor core wherein an hydrogen bond (H-bond) is formed between D370 ECL3 and T5 of ZP3780 (Fig.…”

Differential GLP-1R binding and activation by peptide and non-peptide agonists

“…E21 GLP-1 also interacts with the backbone of the far Nterminus of the receptor. The importance of these key interactions in GLP-1 function are supported by extensive alanine mutagenesis studies ( Figure S5) (Coopman et al, 2010;Dods and Donnelly, 2015;Graaf et al, 2016;Lei et al, 2018;Wootten et al, 2016c;Wootten et al, 2013b;Yang et al, 2016). OWL-833 exhibited a planar pose (parallel to the membrane) in the receptor TM bundle, with overlap with GLP-1 limited to residues F12 GLP-1 -L16 GLP-1 , with the OWL-833 fluoro methyl indazole and dimethyl morpholine arms extending beyond the pocket occupied by peptide and PF 06882961 (Figure 4).…”

“…The GLP-1R is pleiotropically coupled to multiple transducer and regulatory proteins, including G proteins, receptor kinases and b-arrestins (Graaf et al, 2016). Despite their advancement in clinical trials, the pharmacodynamic properties of PF 06882961 and OWL-833 have not been reported and the extent to which these compounds overlap the signalling and regulatory profile of endogenous GLP-1 is unknown.…”