Different conformational responses of the β2-adrenergic receptor-Gs complex upon binding of the partial agonist salbutamol or the full agonist isoprenaline

Abstract

GPCRs are responsible for most cytoplasmic signaling in response to extracellular ligands with different efficacy profiles. Various spectroscopic techniques have identified that agonists exhibiting varying efficacies can selectively stabilize a specific conformation of the receptor. However, the structural basis for activation of the GPCR-G protein complex by ligands with different efficacies is incompletely understood. To better understand the structural basis underlying the mechanisms by which ligands with varying efficacies differentially regulate the conformations of receptors and G proteins, we determined the structures of β2AR-Gαs$\beta $γ bound with partial agonist salbutamol or bound with full agonist isoprenaline using single-particle cryo-electron microscopy at resolutions of 3.26 Å and 3.80 Å, respectively. Structural comparisons between the β2AR-Gs-salbutamol and β2AR-Gs-isoprenaline complexes demonstrated that the decreased binding affinity and efficacy of salbutamol compared with those of isoprenaline might be attributed to the weakened hydrogen bonding interactions, attenuated hydrophobic interactions in the orthosteric binding pocket and different conformational changes in the rotamer toggle switch in TM6. Moreover, the observed stronger interactions between the intracellular loop 2 or 3 (ICL2 or ICL3) of β2AR and Gαs with the binding of salbutamol versus isoprenaline might decrease phosphorylation in the salbutamol-activated β2AR-Gs complex. From the observed structural differences between these complexes of β2AR, a mechanism of β2AR activation by partial and full agonists is proposed to shed structural insights for β2AR desensitization.

Universal Properties and Specificities of the β2-Adrenergic Receptor-Gs Protein Complex Activation Mechanism Revealed by All-Atom Molecular Dynamics Simulations

“…However, in contrast with the present results, the structure of ICL2 did not demonstrate any dependence on the activation state of the MOP. Nevertheless, the present simulation results are in agreement with extensive experimental data reporting an α-helical structure of ICL2 in the active [ 7 , 8 , 36 , 37 ] and unfolded structure in the inactive state of β 2 AR [ 5 , 11 ].…”

Rapidly identifying bioactive compounds from Zhisou oral liquid by immobilized receptor‐based high‐performance affinity chromatography

“…The binding interaction between the compound and β 2 ‐AR was also investigated by molecular docking. For the simulation study, the crystal structure of β 2 ‐AR was obtained with the reference to the isoprenaline‐bound β 2 ‐AR‐Gs protein complex (PDB ID: 7DHR) at a resolution of 3.80 Å [21]. The structure of the compound was modeled by the software of ChemDraw Ultra 8.0 (Cambridge Soft Corporation, MA, USA) and the conformational energies were minimized by Chem3D Ultra 8.0 (Cambridge Soft Corporation).…”

The Impact of the Secondary Binding Pocket on the Pharmacology of Class A GPCRs

“…Among them, 35 active aminergic GPCR structures have been published in the last 2 years ( Supplementary Table S2 ) ( Kooistra et al, 2021 ). These include 7 serotonin ( Kim et al, 2020 ; Peiyu Xu et al, 2021a ; Huang et al, 2021 ) (5-HTR), 15 dopamine ( Zhuang et al, 2021a ; Xiao et al, 2021 ; Zhuang et al, 2021b ; Yin et al, 2020 ; Peiyu Xu et al, 2021b ) (DR), 1 histamine ( Xia et al, 2021 ) (HR), 1 muscarinic ( Staus et al, 2020 ) (MR) and 11 adrenergic ( Lee et al, 2020 ; Fan Yang et al, 2021 ; Yuan et al, 2020 ; Su et al, 2020 ; Xinyu Xu et al, 2021 ; Zhang et al, 2020 ; Nagiri et al, 2021 ) (AR) receptor structures. Out of these complexes, 20 structures contain allosteric modulators but not obviously in the SBP, while 10 were co-crystallized with bitopic ligands bound both the OBP and the SBP.…”