Human GLP-1 receptor transmembrane domain structure in complex with allosteric modulators

Abstract

The glucagon-like peptide-1 receptor (GLP-1R) and the glucagon receptor (GCGR) are members of the secretin-like class B family of G-protein-coupled receptors (GPCRs) and have opposing physiological roles in insulin release and glucose homeostasis. The treatment of type 2 diabetes requires positive modulation of GLP-1R to inhibit glucagon secretion and stimulate insulin secretion in a glucose-dependent manner. Here we report crystal structures of the human GLP-1R transmembrane domain in complex with two different negative allosteric modulators, PF-06372222 and NNC0640, at 2.7 and 3.0 Å resolution, respectively. The structures reveal a common binding pocket for negative allosteric modulators, present in both GLP-1R and GCGR and located outside helices V-VII near the intracellular half of the receptor. The receptor is in an inactive conformation with compounds that restrict movement of the intracellular tip of helix VI, a movement that is generally associated with activation mechanisms in class A GPCRs. Molecular modelling and mutagenesis studies indicate that agonist positive allosteric modulators target the same general region, but in a distinct sub-pocket at the interface between helices V and VI, which may facilitate the formation of an intracellular binding site that enhances G-protein coupling.

A free‐energy landscape for the glucagon‐like peptide 1 receptor GLP1R

“…GLP1R in its active state was taken from PDB ID 5VAI . The inactive conformation was taken from PDB ID 5VEX (Reference ; monomer A).The G‐protein subunits were taken from 5VAI. The modeling of the G‐protein α subunit conformations, considering the relative orientation of the AHD and the RD, as well as the folded state of the α5‐β6 region were taken from our previous study, and in the current work will be referred to as open/closed and ordered/disordered , respectively.…”

“…Briefly, different components of the system (described below) were joined using RMSD alignment, and missing connectors were constructed de‐novo. For the receptor, active and inactive conformations were taken from PDB 5VAI and 5VEX (monomer A), respectively. For the G‐protein: open‐ordered, open‐disordered, and closed states were based on 3SN6, 5JS8, and 1GP2, respectively (see our previous study for more details).…”

An Overview, Advantages and Therapeutic Potential of Nonpeptide Positive Allosteric Modulators of Glucagon‐Like Peptide‐1 Receptor

“…The complex behavior of allosteric ligands requires modified screening methods with detection and quantification of saturability, selectivity, effects on the affinity of orthosteric ligands, and the existence of potential hybrid orthosteric/allosteric ligands . To date, few crystal structures of GPCRs have been revealed, but, together with homology models, allow interpretation of structure–activity relationships, selectivity, and class B GPCR modulation primarily by small molecules . Structurally, class B GPCRs are composed of an N‐terminal extracellular domain, seven‐transmembrane α‐helix domains with three extra‐ and intracellular loops, and a C‐terminal helix.…”

“…The extracellular domain represents a unique site for ligand recognition in class B GPCRs . The activation of class B GPCRs involves movement of transmembrane helices VI and VII to enable G‐protein binding . Reported structural and mechanistic information provides a springboard for the design and discovery of allosteric modulators …”

PAC1 Receptors: Shapeshifters in Motion

“…Perhaps not surprisingly, nearly 40% of all pharmaceutical drugs target class A receptors (Luttrell et al 2015; Zhang et al 2015). The structural solutions to the class B receptors, which encompass 15 members including CRH, glucagon, GLP-1, secretin, vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating polypeptide (PACAP) receptors, have lagged and the 7TM structures of only 4 members have become available only within the last 5 years (Hollenstein et al 2013; Siu et al 2013; Yang et al 2015; Jazayeri et al 2016; Jazayeri et al 2017; Liang et al 2017; Song et al 2017; Zhang et al 2017a; Zhang et al 2018). Although class B receptors are fewer in number, these receptors are increasingly being recognized as mediating some of the most critical physiological functions, including feeding and energy balance, sensory mechanisms, bone metabolism and stress responses (Harmar et al 2012; Culhane et al 2015).…”