Cryo-electron microscopy structure of the glucagon receptor with a dual-agonist peptide

Rulue Chang,Xin Zhang,Anna Qiao,Antao Dai,Matthew J Belousoff,Qiuxiang Tan,Lijun Shao,Li Zhong,Guangyao Lin,Yi-Lynn Liang,Limin Ma,Shuo Han,Dehua Yang,Radostin Danev,Ming-Wei Wang,Denise Wootten,Beili Wu,Patrick M Sexton

doi:10.1074/jbc.ra120.013793

Abstract

Unimolecular dual agonists of the glucagon (GCG) receptor (GCGR) and glucagon-like peptide-1 receptor (GLP-1R) are a new class of drugs that are potentially superior to GLP-1R-specific agonists for the management of metabolic disease. The dual-agonist, peptide 15 (P15), is a glutamic acid 16 analog of GCG with GLP-1 peptide substitutions between amino acids 17 and 24 that has potency equivalent to those of the cognate peptide agonists at the GCGR and GLP-1R. Here, we have used cryo-EM to solve the structure of an active P15-GCGR-Gs complex and compared this structure to our recently published structure of the GCGR-Gs complex bound to GCG. This comparison revealed that P15 has a reduced interaction with the first extracellular loop (ECL1) and the top of transmembrane segment 1 (TM1) such that there is increased mobility of the GCGR extracellular domain and at the C terminus of the peptide compared with the GCG-bound receptor. We also observed a distinct conformation of ECL3 and could infer increased mobility of the far N-terminal His-1 residue in the P15-bound structure. These regions of conformational variance in the two peptide-bound GCGR structures were also regions that were distinct between GCGR structures and previously published peptide-bound structures of the GLP-1R, suggesting that greater conformational dynamics may contribute to the increased efficacy of P15 in activation of the GLP-1R compared with GCG. The variable domains in this receptor have previously been implicated in biased agonism at the GLP-1R and could result in altered signaling of P15 at the GCGR compared with GCG.

Highlights

The G protein-coupled receptor (GPCR) superfamily is one of the largest membrane protein families and GPCRs are widely distributed in the human body where they are involved in most physiological activities [1]
Glucagon is a key regulator of carbohydrate, lipid and amino acid metabolism that is recognized for its counter-regulatory role to the actions of insulin, and is responsible for glycogen and glycolipid decomposition resulting in elevation of blood glucose [6]
Oxyntomodulin is a related peptide that, like GLP-1, is secreted from the intestine following meal ingestion that is a dual agonist of GLP-1 receptor (GLP-1R) and GCG receptor (GCGR) but with lower potency in canonical cAMP signalling assays than the “cognate” agonists of these receptors [21]

Summary

Introduction

The G protein-coupled receptor (GPCR) superfamily is one of the largest membrane protein families and GPCRs are widely distributed in the human body where they are involved in most physiological activities [1]. We report the cryoelectron microscopy (cryo-EM) structure of GCGR in complex with heterotrimeric Gs protein and a dual agonist, peptide 15 (P15) [11], at a global resolution of 3.4 Å.

Results

Conclusion