Extracellular loops 1 and 3 and their associated transmembrane regions of the calcitonin receptor-like receptor are needed for CGRP receptor function

Barwell, James; Conner, Alex C.; Poyner, David R.

doi:10.1016/j.bbamcr.2011.06.005

Cited by 37 publications

(53 citation statements)

References 34 publications

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“…Even though the cryo-EM map is limited in resolution, the α-helical nature of the peptide and the stability of its position have allowed us to confidently establish its main interactions with the receptor. The majority of these observations, summarized in Supplementary Table S1, are confirmed through extensive mutagenesis studies on GLP1-R and other Family B GPCRs 20–31 .…”

Section: Glp-1 Recognition By Glp-1rmentioning

confidence: 61%

“…2d). ECL1 has been implicated in peptide binding based on hydrogen-deuterium exchange experiments and MD simulations with GCGR 32 , as well as alanine scanning mutagenesis on the calcitonin receptor-like receptor 31 . We also note that the prominent interactions involving ECLs 1 and 2 with residues past the N-terminal region of the hormone may explain the partial agonist activity of shorter peptide fragments, such as GLP-1(15–36) 34 .…”

Section: Glp-1 Recognition By Glp-1rmentioning

confidence: 99%

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

Zhang

Sun

Feng

et al. 2017

Nature

494

568

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Summary Glucagon-like peptide-1 (GLP-1) is a hormone with essential roles in regulating insulin secretion, carbohydrate metabolism and appetite. GLP-1 effects are mediated through binding to GLP-1R, a family B G protein-coupled receptor (GPCR) signaling primarily through the stimulatory G protein Gs. Family B GPCRs are important therapeutic targets, however our understanding of their mechanism of action is limited by the lack of structural information on activated and full-length receptors. Here we show the electron cryo-microscopy structure of the peptide-activated GLP-1R:Gs complex at near atomic resolution. The peptide is clasped between the N-terminal domain and transmembrane core of the receptor, further stabilized by extracellular loops. Conformational changes in the transmembrane domain result in a sharp kink in the middle of transmembrane helix 6, which pivots its intracellular half outward to accommodate the α5 helix of GαsRas. These results provide a structural framework for understanding family B receptor activation through hormone binding.

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Section: Glp-1 Recognition By Glp-1rmentioning

confidence: 61%

Section: Glp-1 Recognition By Glp-1rmentioning

confidence: 99%

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

Zhang

Sun

Feng

et al. 2017

Nature

494

568

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“…We propose that such negative regulation by the ECD may be a common feature of at least a subset of this receptor family. Recent studies of the calcitonin generelated peptide receptor identified point mutations in ECL3 that also lead to significant increases in both basal and ligand-induced activity (32), although the mechanism for this is unknown. The ECD of class B GPCRs may play a similar role to the well-defined inhibitory ionic lock that keeps many class A GPCRs in an inactive state (33).…”

Section: Discussionmentioning

confidence: 99%

Molecular basis for negative regulation of the glucagon receptor

Koth¹,

Murray²,

Mukund³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

123

179

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Members of the class B family of G protein-coupled receptors (GPCRs) bind peptide hormones and have causal roles in many diseases, ranging from diabetes and osteoporosis to anxiety. Although peptide, small-molecule, and antibody inhibitors of these GPCRs have been identified, structure-based descriptions of receptor antagonism are scarce. Here we report the mechanisms of glucagon receptor inhibition by blocking antibodies targeting the receptor's extracellular domain (ECD). These studies uncovered a role for the ECD as an intrinsic negative regulator of receptor activity. The crystal structure of the ECD in complex with the Fab fragment of one antibody, mAb1, reveals that this antibody inhibits glucagon receptor by occluding a surface extending across the entire hormone-binding cleft. A second antibody, mAb23, blocks glucagon binding and inhibits basal receptor activity, indicating that it is an inverse agonist and that the ECD can negatively regulate receptor activity independent of ligand binding. Biochemical analyses of receptor mutants in the context of a high-resolution ECD structure show that this previously unrecognized inhibitory activity of the ECD involves an interaction with the third extracellular loop of the receptor and suggest that glucagon-mediated structural changes in the ECD accompany receptor activation. These studies have implications for the design of drugs to treat class B GPCR-related diseases, including the potential for developing novel allosteric regulators that target the ECDs of these receptors.T he glucagon receptor (GCGR) is a member of the class B G protein-coupled receptor (GPCR) family (1) that mediates the activity of glucagon, a pancreatic islet-derived peptide hormone that plays a central role in the pathophysiology of diabetes (2). Several GCGR antagonists that improve glycemic control in animal models of diabetes and diabetic patients have been described (3-8). Although biochemical studies of glucagon and GCGR mutants have facilitated the mapping of some elements that contribute to glucagon binding (4, 9-12), the molecular mechanisms of GCGR activation and inhibition remain largely unknown because there are currently no high-resolution structures of GCGR. The current model for activation class B GPCRs proposes a tethering mechanism whereby the C-terminal half of the peptide ligand first binds a large extracellular domain (ECD), thereby enabling a high-affinity interaction of the N-terminal half of the ligand with a cleft formed by the transmembrane α-helical bundle (13,14), termed the juxtamembrane (JM) domain. This interaction induces a structural change in the transmembrane and intracellular face of the receptor that enables G protein coupling, likely similar to that described for the activated form of the β-adrenergic receptor (15). Recent structural studies of several class B GPCR ECDs and ECD-ligand complexes support this model (16)(17)(18)(19)(20)(21). Glucagon likely interacts with GCGR in a similar fashion to the interaction of other peptide ligands with class B GPC...

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“…Nonetheless, several recent studies provided insight into this area using mutagenesis and/or chimeric approaches to explore how the CLR 7TM domain recognizes peptides. Various residues in all three extracellular loops (ECL) of CLR were important for response to CGRP in the CGRP receptor (84; 85) and ECL3 was important for responses to AM in the AM 1 and AM 2 receptors (86). Thr6 in the CGRP peptide, which is also conserved in AM, was shown to be important for agonist activity (87).…”

Section: New Insights From Structural and Molecular Studiesmentioning

confidence: 99%

Receptor Activity-Modifying Proteins (RAMPs): New Insights and Roles

Hay

Pioszak

2016

Annu. Rev. Pharmacol. Toxicol.

149

151

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Once considered as largely independent functional units, G protein-coupled receptors (GPCRs) are now recognized as having a far more diverse molecular architecture. Receptor activity-modifying proteins (RAMPs) provide a major example of proteins that interact with GPCRs to modify their function. RAMPs are able to act as pharmacological switches, chaperones, regulate signaling and/or trafficking in a receptor-dependent manner. This review covers recent discoveries in the RAMP field and summarizes the known GPCR partners and functions of RAMPs. We also discuss the first peptide-bound structures of RAMP-GPCR complexes, which give insight into the molecular mechanisms as to how RAMPs can alter the pharmacology of GPCRs and their signaling.

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Extracellular loops 1 and 3 and their associated transmembrane regions of the calcitonin receptor-like receptor are needed for CGRP receptor function

Cited by 37 publications

References 34 publications

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

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

Molecular basis for negative regulation of the glucagon receptor

Receptor Activity-Modifying Proteins (RAMPs): New Insights and Roles

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