scholarly journals Structural insights into ligand efficacy and activation of the glucagon receptor

2019 ◽  
Author(s):  
Daniel Hilger ◽  
Kaavya Krishna Kumar ◽  
Hongli Hu ◽  
Mie Fabricius Pedersen ◽  
Lise Giehm ◽  
...  
Keyword(s):  
G Protein ◽  
Partial Agonist ◽  
Transmembrane Helix ◽  
Peptide Hormone ◽  
Receptor Activation ◽  
Glucagon Receptor ◽  
Structural Framework ◽  
Class B ◽  
Treatment Of Diabetes ◽  
Sugar Levels

AbstractThe glucagon receptor family comprises Class B G protein-coupled receptors (GPCRs) that play a crucial role in regulating blood sugar levels. Receptors of this family represent important therapeutic targets for the treatment of diabetes and obesity. Despite intensive structural studies, we only have a poor understanding of the mechanism of peptide hormone-induced Class B receptor activation. This process involves the formation of a sharp kink in transmembrane helix 6 that moves out to allow formation of the nucleotide-free G protein complex. Here, we present the cryo-EM structure of the glucagon receptor (GCGR), a prototypical Class B GPCR, in complex with an engineered soluble glucagon derivative and the heterotrimeric G-protein, Gs. Comparison with the previously determined crystal structures of GCGR bound to a partial agonist reveals a structural framework to explain the molecular basis of ligand efficacy that is further supported by mutagenesis data.

scholarly journals The Role of ICL1 and H8 in Class B1 GPCRs; Implications for Receptor Activlation

2022 ◽  
Vol 12 ◽  
Author(s):  
Ian Winfield ◽  
Kerry Barkan ◽  
Sarah Routledge ◽  
Nathan J. Robertson ◽  
Matthew Harris ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
G Protein ◽  
Conformational Changes ◽  
Transmembrane Helix ◽  
Receptor Activation ◽  
Cgrp Receptor ◽  
Intracellular Loop ◽  
Glucagon Receptor ◽  
G Protein Coupled

The first intracellular loop (ICL1) of G protein-coupled receptors (GPCRs) has received little attention, although there is evidence that, with the 8th helix (H8), it is involved in early conformational changes following receptor activation as well as contacting the G protein β subunit. In class B1 GPCRs, the distal part of ICL1 contains a conserved R12.48KLRCxR2.46b motif that extends into the base of the second transmembrane helix; this is weakly conserved as a [R/H]12.48KL[R/H] motif in class A GPCRs. In the current study, the role of ICL1 and H8 in signaling through cAMP, iCa2+ and ERK1/2 has been examined in two class B1 GPCRs, using mutagenesis and molecular dynamics. Mutations throughout ICL1 can either enhance or disrupt cAMP production by CGRP at the CGRP receptor. Alanine mutagenesis identified subtle differences with regard elevation of iCa2+, with the distal end of the loop being particularly sensitive. ERK1/2 activation displayed little sensitivity to ICL1 mutation. A broadly similar pattern was observed with the glucagon receptor, although there were differences in significance of individual residues. Extending the study revealed that at the CRF1 receptor, an insertion in ICL1 switched signaling bias between iCa2+ and cAMP. Molecular dynamics suggested that changes in ICL1 altered the conformation of ICL2 and the H8/TM7 junction (ICL4). For H8, alanine mutagenesis showed the importance of E3908.49b for all three signal transduction pathways, for the CGRP receptor, but mutations of other residues largely just altered ERK1/2 activation. Thus, ICL1 may modulate GPCR bias via interactions with ICL2, ICL4 and the Gβ subunit.

scholarly journals Structural basis for GLP-1 receptor activation by LY3502970, an orally active nonpeptide agonist

2020 ◽  
Vol 117 (47) ◽  
pp. 29959-29967 ◽  
Author(s):  
Takahiro Kawai ◽  
Bingfa Sun ◽  
Hitoshi Yoshino ◽  
Dan Feng ◽  
Yoshiyuki Suzuki ◽  
...  
Keyword(s):  
Oral Administration ◽  
G Protein ◽  
Partial Agonist ◽  
Pharmacokinetic Profile ◽  
Binding Pocket ◽  
Receptor Activation ◽  
Structural Basis ◽  
Protein Activation ◽  
Class B ◽  
Glucagon Like Peptide 1

Glucagon-like peptide-1 receptor (GLP-1R) agonists are efficacious antidiabetic medications that work by enhancing glucose-dependent insulin secretion and improving energy balance. Currently approved GLP-1R agonists are peptide based, and it has proven difficult to obtain small-molecule activators possessing optimal pharmaceutical properties. We report the discovery and mechanism of action of LY3502970 (OWL833), a nonpeptide GLP-1R agonist. LY3502970 is a partial agonist, biased toward G protein activation over β-arrestin recruitment at the GLP-1R. The molecule is highly potent and selective against other class B G protein–coupled receptors (GPCRs) with a pharmacokinetic profile favorable for oral administration. A high-resolution structure of LY3502970 in complex with active-state GLP-1R revealed a unique binding pocket in the upper helical bundle where the compound is bound by the extracellular domain (ECD), extracellular loop 2, and transmembrane helices 1, 2, 3, and 7. This mechanism creates a distinct receptor conformation that may explain the partial agonism and biased signaling of the compound. Further, interaction between LY3502970 and the primate-specific Trp33 of the ECD informs species selective activity for the molecule. In efficacy studies, oral administration of LY3502970 resulted in glucose lowering in humanized GLP-1R transgenic mice and insulinotropic and hypophagic effects in nonhuman primates, demonstrating an effect size in both models comparable to injectable exenatide. Together, this work determined the molecular basis for the activity of an oral agent being developed for the treatment of type 2 diabetes mellitus, offering insights into the activation of class B GPCRs by nonpeptide ligands.

scholarly journals Structure and dynamics of the active human parathyroid hormone receptor-1

Science ◽  
2019 ◽  
Vol 364 (6436) ◽  
pp. 148-153 ◽  
Author(s):  
Li-Hua Zhao ◽  
Shanshan Ma ◽  
Ieva Sutkeviciute ◽  
Dan-Dan Shen ◽  
X. Edward Zhou ◽  
...  
Keyword(s):  
Parathyroid Hormone ◽  
G Protein ◽  
Hormone Receptor ◽  
Transmembrane Domain ◽  
Transmembrane Helix ◽  
Receptor Activation ◽  
Structural Basis ◽  
Parathyroid Hormone Receptor ◽  
Class B ◽  
Long Acting

The parathyroid hormone receptor-1 (PTH1R) is a class B G protein–coupled receptor central to calcium homeostasis and a therapeutic target for osteoporosis and hypoparathyroidism. Here we report the cryo–electron microscopy structure of human PTH1R bound to a long-acting PTH analog and the stimulatory G protein. The bound peptide adopts an extended helix with its amino terminus inserted deeply into the receptor transmembrane domain (TMD), which leads to partial unwinding of the carboxyl terminus of transmembrane helix 6 and induces a sharp kink at the middle of this helix to allow the receptor to couple with G protein. In contrast to a single TMD structure state, the extracellular domain adopts multiple conformations. These results provide insights into the structural basis and dynamics of PTH binding and receptor activation.

Activation and conformational dynamics of a class B G-protein-coupled glucagon receptor

2016 ◽  
Vol 18 (18) ◽  
pp. 12642-12650 ◽  
Author(s):  
Yang Li ◽  
Jixue Sun ◽  
Dongmei Li ◽  
Jianping Lin
Keyword(s):  
Hydrogen Bonds ◽  
G Protein ◽  
Conformational Dynamics ◽  
Glucagon Receptor ◽  
Class B ◽  
G Protein Coupled

The binding of the agonist glucagon would induce the conformational dynamics and activation of the GCGR. The activation led to the outward movement of helix VII and breaking of two hydrogen bonds.

scholarly journals Interaction of Glucagon G-Protein Coupled Receptor with Known Natural Antidiabetic Compounds: MultiscoringIn SilicoApproach

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
M. H. Baig ◽  
K. Ahmad ◽  
Q. Hasan ◽  
M. K. A. Khan ◽  
N. S. Rao ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
G Protein ◽  
Scoring Function ◽  
Natural Compounds ◽  
G Protein Coupled Receptors ◽  
Binding Potential ◽  
Glucagon Receptor ◽  
Class B ◽  
G Protein Coupled

Glucagon receptor (GCGR) is a secretin-like (class B) family of G-protein coupled receptors (GPCRs) in humans that plays an important role in elevating the glucose concentration in blood and has thus become one of the promising therapeutic targets for treatment of type 2 diabetes mellitus. GCGR based inhibitors for the treatment of type 2 diabetes are either glucagon neutralizers or small molecular antagonists. Management of diabetes without any side effects is still a challenge to the medical system, and the search for a new and effective natural GCGR antagonist is an important area for the treatment of type 2 diabetes. In the present study, a number of natural compounds containing antidiabetic properties were selected from the literature and their binding potential against GCGR was determined using molecular docking and otherin silicoapproaches. Among all selected natural compounds, curcumin was found to be the most effective compound against GCGR followed by amorfrutin 1 and 4-hydroxyderricin. These compounds were rescored to confirm the accuracy of binding using another scoring function (x-score). The final conclusions were drawn based on the results obtained from the GOLD andx-score. Further experiments were conducted to identify the atomic level interactions of selected compounds with GCGR.

scholarly journals Probing the β2 Adrenoceptor Binding Site with Catechol Reveals Differences in Binding and Activation by Agonists and Partial Agonists

2005 ◽  
Vol 280 (23) ◽  
pp. 22165-22171 ◽  
Author(s):  
Gayathri Swaminath ◽  
Xavier Deupi ◽  
Tae Weon Lee ◽  
Wen Zhu ◽  
Foon Sun Thian ◽  
...  
Keyword(s):  
Binding Site ◽  
Aromatic Ring ◽  
Partial Agonist ◽  
Transmembrane Helix ◽  
Receptor Activation ◽  
Molecular Probe ◽  
Toggle Switch ◽  
Partial Agonists ◽  
Gpcr Activation ◽  
Multistep Process

The β2 adrenergic receptor (β2AR) is a prototypical family A G protein-coupled receptor (GPCR) and an excellent model system for studying the mechanism of GPCR activation. The β2AR agonist binding site is well characterized, and there is a wealth of structurally related ligands with functionally diverse properties. In the present study, we use catechol (1,2-benzenediol, a structural component of catecholamine agonists) as a molecular probe to identify mechanistic differences between β2AR activation by catecholamine agonists, such as isoproterenol, and by the structurally related non-catechol partial agonist salbutamol. Using biophysical and pharmacologic approaches, we show that the aromatic ring of salbutamol binds to a different site on the β2AR than the aromatic ring of catecholamines. This difference is important in receptor activation as it has been hypothesized that the aromatic ring of catecholamines plays a role in triggering receptor activation through interactions with a conserved cluster of aromatic residues in the sixth transmembrane segment by a rotamer toggle switch mechanism. Our experiments indicate that the aromatic ring of salbutamol does not activate this mechanism either directly or indirectly. Moreover, the non-catechol ring of partial agonists does not interact optimally with serine residues in the fifth transmembrane helix that have been shown to play an important role in activation by catecholamines. These results demonstrate unexpected differences in binding and activation by structurally similar agonists and partial agonists. Moreover, they provide evidence that activation of a GPCR is a multistep process that can be dissected into its component parts using agonist fragments.

scholarly journals Mechanisms of adhesion G protein–coupled receptor activation

2020 ◽  
Vol 295 (41) ◽  
pp. 14065-14083 ◽  
Author(s):  
Alexander Vizurraga ◽  
Rashmi Adhikari ◽  
Jennifer Yeung ◽  
Maiya Yu ◽  
Gregory G. Tall
Keyword(s):  
G Protein ◽  
Receptor Activation ◽  
G Protein Signaling ◽  
Protein Signaling ◽  
Physiological Processes ◽  
Class B ◽  
Peptide Agonist ◽  
G Protein Coupled ◽  
Existing Structure

Adhesion G protein–coupled receptors (AGPCRs) are a thirty-three-member subfamily of Class B GPCRs that control a wide array of physiological processes and are implicated in disease. AGPCRs uniquely contain large, self-proteolyzing extracellular regions that range from hundreds to thousands of residues in length. AGPCR autoproteolysis occurs within the extracellular GPCR autoproteolysis-inducing (GAIN) domain that is proximal to the N terminus of the G protein–coupling seven-transmembrane–spanning bundle. GAIN domain–mediated self-cleavage is constitutive and produces two-fragment holoreceptors that remain bound at the cell surface. It has been of recent interest to understand how AGPCRs are activated in relation to their two-fragment topologies. Dissociation of the AGPCR fragments stimulates G protein signaling through the action of the tethered-peptide agonist stalk that is occluded within the GAIN domain in the holoreceptor form. AGPCRs can also signal independently of fragment dissociation, and a few receptors possess GAIN domains incapable of self-proteolysis. This has resulted in complex theories as to how these receptors are activated in vivo, complicating pharmacological advances. Currently, there is no existing structure of an activated AGPCR to support any of the theories. Further confounding AGPCR research is that many of the receptors remain orphans and lack identified activating ligands. In this review, we provide a detailed layout of the current theorized modes of AGPCR activation with discussion of potential parallels to mechanisms used by other GPCR classes. We provide a classification means for the ligands that have been identified and discuss how these ligands may activate AGPCRs in physiological contexts.

scholarly journals Regulation of G protein-coupled cAMP receptor activation by a hydrophobic residue in transmembrane helix 3

2007 ◽  
Vol 65 (2) ◽  
pp. 508-520 ◽  
Author(s):  
Minghang Zhang ◽  
Mousumi Goswami ◽  
Satoshi Sawai ◽  
Edward C. Cox ◽  
Dale Hereld
Keyword(s):  
G Protein ◽  
Transmembrane Helix ◽  
Receptor Activation ◽  
Hydrophobic Residue ◽  
Camp Receptor ◽  
G Protein Coupled

scholarly journals Correlated motions of conserved polar motifs lay out a plausible mechanism of G protein-coupled receptor activation.

2020 ◽  
Author(s):  
Argha Mitra ◽  
Arijit Sarkar ◽  
Marton Richard Szabo ◽  
Attila Borics
Keyword(s):  
G Protein ◽  
Intracellular Signaling ◽  
Transmembrane Helix ◽  
Receptor Activation ◽  
Current Theory ◽  
Activation Mechanism ◽  
Structural Basis ◽  
Binding Interface ◽  
Gpcr Activation ◽  
G Protein Coupled

Recent advancements in the field of experimental structural biology have provided high-resolution structures of active and inactive state G protein-coupled receptors (GPCRs), a highly important pharmaceutical target family, but the process of transition between these states is poorly understood. According to the current theory, GPCRs exist in structurally distinct, dynamically interconverting functional states of which populations are shifted upon binding of ligands and intracellular signaling proteins. However, explanation of the activation mechanism on an entirely structural basis gets complicated when multiple activation pathways and active receptor states are considered. Our unbiased, atomistic molecular dynamics simulations of the mu-opioid receptor in a physiological environment revealed that external stimulus is propagated to the intracellular surface of the receptor through subtle, concerted movements of highly conserved polar amino acid side chains along the 7th transmembrane helix. To amend the widely accepted theory we suggest that the initiation event of GPCR activation is the shift of macroscopic polarization between the ortho- and allosteric binding pockets and the intracellular G protein-binding interface.

scholarly journals Universal activation mechanism of class A GPCRs

2019 ◽  
Author(s):  
Qingtong Zhou ◽  
Dehua Yang ◽  
Meng Wu ◽  
Yu Guo ◽  
Wangjing Guo ◽  
...  
Keyword(s):  
Ligand Binding ◽  
G Protein ◽  
Transmembrane Helix ◽  
Binding Pocket ◽  
Receptor Activation ◽  
Activation Mechanism ◽  
Coupling Region ◽  
Activation Pathway ◽  
Class A ◽  
Gpcr Activation

AbstractClass A G protein-coupled receptors (GPCRs) influence virtually every aspect of human physiology. GPCR activation is an allosteric process that links agonist binding to G protein recruitment, with the hallmark outward movement of transmembrane helix 6 (TM6). However, what leads to TM6 movement and the key residue-level changes of this trigger remain less well understood. Here, by analyzing over 230 high-resolution structures of class A GPCRs, we discovered a modular, universal GPCR activation pathway that unites previous findings into a common activation mechanism, directly linking the bottom of ligand-binding pocket with G protein-coupling region. We suggest that the modular nature of the universal GPCR activation pathway allowed for the decoupling of the evolution of the ligand binding site, G protein binding region and the residues important for receptor activation. Such an architecture might have facilitated GPCRs to emerge as a highly successful family of proteins for signal transduction in nature.

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