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Mechanism of ?-arrestin recruitment by the ?-opioid G protein-coupled receptor.

ABSTRACT: Agonists to the ?-opioid G protein-coupled receptor (?OR) can alleviate pain through activation of G protein signaling, but they can also induce ?-arrestin activation, leading to such side effects as respiratory depression. Biased ligands to ?OR that induce G protein signaling without inducing ?-arrestin signaling can alleviate pain while reducing side effects. However, the mechanism for stimulating ?-arrestin signaling is not known, making it difficult to design optimum biased ligands. We use extensive molecular dynamics simulations to determine three-dimensional (3D) structures of activated ?-arrestin2 stabilized by phosphorylated ?OR bound to the morphine and D-Ala², N-MePhe⁴, Gly-ol]-enkephalin (DAMGO) nonbiased agonists and to the TRV130 biased agonist. For nonbiased agonists, we find that the ?-arrestin2 couples to the phosphorylated ?OR by forming strong polar interactions with intracellular loop 2 (ICL2) and either the ICL3 or cytoplasmic region of transmembrane (TM6). Strikingly, Gi protein makes identical strong bonds with these same ICLs. Thus, the Gi protein and ?-arrestin2 compete for the same binding site even though their recruitment leads to much different outcomes. On the other hand, we find that TRV130 has a greater tendency to bind the extracellular portion of TM2 and TM3, which repositions TM6 in the cytoplasmic region of ?OR, hindering ?-arrestin2 from making polar anchors to the ICL3 or to the cytosolic end of TM6. This dramatically reduces the affinity between ?OR and ?-arrestin2.

SUBMITTER: Mafi A

PROVIDER: S-EPMC7368253 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Mechanism of β-arrestin recruitment by the μ-opioid G protein-coupled receptor.

Mafi Amirhossein A Kim Soo-Kyung SK Goddard William A WA

Proceedings of the National Academy of Sciences of the United States of America 20200629 28

Agonists to the μ-opioid G protein-coupled receptor (μOR) can alleviate pain through activation of G protein signaling, but they can also induce β-arrestin activation, leading to such side effects as respiratory depression. Biased ligands to μOR that induce G protein signaling without inducing β-arrestin signaling can alleviate pain while reducing side effects. However, the mechanism for stimulating β-arrestin signaling is not known, making it difficult to design optimum biased ligands. We use e ...[more]

PMID: 32601232

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Project description:G-protein-coupled receptors (GPCRs) are critically regulated by ?-arrestins, which not only desensitize G-protein signalling but also initiate a G-protein-independent wave of signalling. A recent surge of structural data on a number of GPCRs, including the ?2 adrenergic receptor (?2AR)-G-protein complex, has provided novel insights into the structural basis of receptor activation. However, complementary information has been lacking on the recruitment of ?-arrestins to activated GPCRs, primarily owing to challenges in obtaining stable receptor-?-arrestin complexes for structural studies. Here we devised a strategy for forming and purifying a functional human ?2AR-?-arrestin-1 complex that allowed us to visualize its architecture by single-particle negative-stain electron microscopy and to characterize the interactions between ?2AR and ?-arrestin 1 using hydrogen-deuterium exchange mass spectrometry (HDX-MS) and chemical crosslinking. Electron microscopy two-dimensional averages and three-dimensional reconstructions reveal bimodal binding of ?-arrestin 1 to the ?2AR, involving two separate sets of interactions, one with the phosphorylated carboxy terminus of the receptor and the other with its seven-transmembrane core. Areas of reduced HDX together with identification of crosslinked residues suggest engagement of the finger loop of ?-arrestin 1 with the seven-transmembrane core of the receptor. In contrast, focal areas of raised HDX levels indicate regions of increased dynamics in both the N and C domains of ?-arrestin 1 when coupled to the ?2AR. A molecular model of the ?2AR-?-arrestin signalling complex was made by docking activated ?-arrestin 1 and ?2AR crystal structures into the electron microscopy map densities with constraints provided by HDX-MS and crosslinking, allowing us to obtain valuable insights into the overall architecture of a receptor-arrestin complex. The dynamic and structural information presented here provides a framework for better understanding the basis of GPCR regulation by arrestins.

Dataset Information

Mechanism of ?-arrestin recruitment by the ?-opioid G protein-coupled receptor.

Publications

Mechanism of β-arrestin recruitment by the μ-opioid G protein-coupled receptor.

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