Structure of the Human Glucagon Class B G-Protein-Coupled Receptor

Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
Nature (Impact Factor: 41.46). 07/2013; 499(7459). DOI: 10.1038/nature12393
Source: PubMed


Binding of the glucagon peptide to the glucagon receptor (GCGR) triggers the release of glucose from the liver during fasting; thus GCGR plays an important role in glucose homeostasis. Here we report the crystal structure of the seven transmembrane helical domain of human GCGR at 3.4 Å resolution, complemented by extensive site-specific mutagenesis, and a hybrid model of glucagon bound to GCGR to understand the molecular recognition of the receptor for its native ligand. Beyond the shared seven transmembrane fold, the GCGR transmembrane domain deviates from class A G-protein-coupled receptors with a large ligand-binding pocket and the first transmembrane helix having a 'stalk' region that extends three alpha-helical turns above the plane of the membrane. The stalk positions the extracellular domain (∼12 kilodaltons) relative to the membrane to form the glucagon-binding site that captures the peptide and facilitates the insertion of glucagon's amino terminus into the seven transmembrane domain.

    • "org), 54 correspond to unique sequences of 30 different nonrhodopsin receptors (e.g., the turkey b 1 adrenergic receptor [b 1 AR] has been solved using three different constructs ; see Supplemental Table 1). Of these sequences, 51 have some form of receptor truncation (Supplemental Table 1): 43 constructs have been crystallized with C-terminal truncations , 32 have been truncated at the N terminus, sometimes removing whole domains (Hollenstein et al., 2013; Siu et al., 2013; Doré et al., 2014; Wu et al., 2014), and 35 were crystallized with shortened ICLs (Warne et al., 2008; Zou et al., 2012; Egloff et al., 2014). Mutagenesis and Conformational Stabilization. "
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    ABSTRACT: G protein-coupled receptor (GPCR) structural biology has progressed dramatically in the last decade. There are now over 120 GPCR crystal structures deposited in the Protein Data Bank of 32 different receptors from families scattered across the phylogenetic tree, including Class B, C, and Frizzled GPCRs. These structures have been obtained in combination with a wide variety of ligands, and captured in a range of conformational states. This surge in structural knowledge has enlightened research into the molecular recognition of biologically active molecules, the mechanisms of receptor activation, the dynamics of functional selectivity, and fuelled structure- based drug design efforts for GPCRs. Here we summarize the innovations in both protein engineering/molecular biology and crystallography techniques that have led to these advances in GPCR structural biology, and discuss how they may influence the resulting structural models. We also provide a brief molecular pharmacologist's guide to GPCR X-ray crystallography, outlining some key aspects in the process of structure determination, with the goal to encourage non-crystallographers to interrogate structures at the molecular level. Finally we show how chemogenomics approaches can be used to marry the wealth of existing receptor pharmacology data with the expanding repertoire of structures, providing a deeper understanding of the mechanistic details of GPCR function. The American Society for Pharmacology and Experimental Therapeutics.
    No preview · Article · Jul 2015 · Molecular pharmacology
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    • "Questions remain regarding the secondary structure and regional stability of class B GPCR peptide ligands in the environment around a cell membrane. Recent advances in crystallography have used nonionic n-dodecyl-β-D-maltoside (DDM) and cholesterol hemisuccinate (CHS) and derivatives of these lipids to obtain near-full length GPCR structures in micelles, including two class B GPCRs, the human glucagon receptor (GCGR) and human corticotropin-releasing factor receptor 1 (CRF1) [13], [14]. These nonionic lipids are milder denaturants compared to their ionic counterparts and represent a more biologically relevant lipid membrane environment. "
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    ABSTRACT: Activation of the glucagon-like peptide-1 receptor (GLP-1R) in pancreatic β-cells potentiates insulin production and is a current therapeutic target for the treatment of type 2 diabetes mellitus (T2DM). Like other class B G protein-coupled receptors (GPCRs), the GLP-1R contains an N-terminal extracellular ligand binding domain. N-terminal truncations on the peptide agonist generate antagonists capable of binding to the extracellular domain, but not capable of activating full length receptor. The main objective of this study was to use Hydrogen/deuterium exchange (HDX) to identify how the amide hydrogen bonding network of peptide ligands and the extracellular domain of GLP-1R (nGLP-1R) were altered by binding interactions and to then use this platform to validate direct binding events for putative GLP-1R small molecule ligands. The HDX studies presented here for two glucagon-like peptide-1 receptor (GLP-1R) peptide ligands indicates that the antagonist exendin-4[9-39] is significantly destabilized in the presence of nonionic detergents as compared to the agonist exendin-4. Furthermore, HDX can detect stabilization of exendin-4 and exendin-4[9-39] hydrogen bonding networks at the N-terminal helix [Val19 to Lys27] upon binding to the N-terminal extracellular domain of GLP-1R (nGLP-1R). In addition we show hydrogen bonding network stabilization on nGLP-1R in response to ligand binding, and validate direct binding events with the extracellular domain of the receptor for putative GLP-1R small molecule ligands.
    Full-text · Article · Sep 2014 · PLoS ONE
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    • "While in vivo data may be confounded by differential levels of circulating insulin, OXM was described as a more potent regulator than glucagon in stimulating intestinal glucose absorption in the isolated small intestine despite being 1-2 orders of magnitude less potent at the GCGR than glucagon [61]. Because GLP-1 does not stimulate glucose absorption and an increase in hexose transport has been previously described for glucagon-like peptide-2 (GLP-2) and glucose-dependent insulinotropic peptide (GIP) [62] [63], OXM could engage additional G-protein-coupled receptors (GPCR) of the secretin like (class B) family such as GLP-2 and GIP receptors [64] [65]. Treatment of BHK-GIPR or BHK-GLP2R rat cells with OXM had no effect on cAMP production, whereas BHK cells that express the rat GLP-1 or glucagon receptors exhibited significant increases in cAMP accumulation in response to treatment with OXM [30]. "
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    ABSTRACT: Oxyntomodulin (OXM) is a peptide hormone released from the gut in post-prandial state that activates both the glucagon-like peptide-1 receptor (GLP1R) and the glucagon receptor (GCGR) resulting in superior body weight lowering to selective GLP1R agonists. OXM reduces food intake and increases energy expenditure in humans. While activation of the GCGR increases glucose production posing a hyperglycemic risk, the simultaneous activation of the GLP1R counteracts this effect. Acute OXM infusion improves glucose tolerance in T2DM patients making dual agonists of the GCGR and GLP1R new promising treatments for diabetes and obesity with the potential for weight loss and glucose lowering superior to that of GLP1R agonists.
    Full-text · Article · Jun 2014 · Molecular Metabolism
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