Agonist binding by the β2-adrenergic receptor: an effect of receptor conformation on ligand association–dissociation characteristics

Abstract

The β2-adrenergic receptor (β2-AR), a G protein-coupled receptor (GPCR), is a physiologically important transmembrane protein that is a target for drugs used for treatment of asthma and cardiovascular diseases. Study of the first steps of ligand recognition and the molecular basis of ligand binding to the orthosteric site is essential for understanding the pharmacological properties of the receptor. In this work we investigated the characteristic features of the agonist association–dissociation process to and from the different conformational forms of β2-AR by use of advanced molecular modeling techniques. The investigation was focused on estimating the free energy profiles (FEPs) corresponding to the process of a full agonist ((R,R)-fenoterol) and an inverse agonist (carazolol) binding and unbinding to and from β2-AR. The two different conformational forms of β2-AR, i.e. active β2-AR–PDB: 3P0G and inactive β2-AR–PDB: 2RH1 were included in this stage of the study. We revealed several significant qualitative differences between FEPs characteristic of both conformational forms. Both FEPs suggest the existence of three transient binding sites in the extracellular domain of β2-AR. Comparison of the residues surrounding these transient binding sites in both β2-AR states revealed the importance of the aromatic residues F194, H932.64, H2966.58, and H178 (extracellular part of β2-AR) in the early stages of the binding process. In addition, slightly different exit and entry paths are preferred by the ligand molecule in the extracellular part of β2-AR, depending on the conformation of the receptor.Electronic supplementary materialThe online version of this article (doi:10.1007/s00249-015-1010-4) contains supplementary material, which is available to authorized users.

Exploring the kinetic selectivity of drugs targeting the β1‐adrenoceptor

“…Mutational, crystal modeling and docking studies have highlighted the key role that specific regions of these receptors forming the entrance to the binding pocket, play in dictating overall drug–receptor affinity 3 , 23 , 24 , 25 , 26 , 27 , 28 , 29 and kinetics. 10 A comparison of the residues of both β‐adrenoceptor subtypes has suggested the importance of non‐conserved electrostatic interactions as well as conserved aromatic contacts in the early steps of the binding process.…”

Exploring the kinetic selectivity of drugs targeting the β1-adrenoceptor

“…Mutational, crystal modelling and docking studies have highlighted the key role that specific regions of these receptors forming the entrance to the binding pocket, play in dictating overall drug-receptor affinity (Baker et al, 2015;Dror et al, 2011;Isogaya et al, 1999;Kaszuba et al, 2010;Kikkawa et al, 1998;Plazinska et al, 2013;Plazinska et al, 2015;Warne et al, 2008) and kinetics (Xu et al, 2020). A comparison of the residues of both β-adrenoceptor subtypes has suggested the importance of nonconserved electrostatic interactions as well as conserved aromatic contacts in the early steps of the binding process (Selvam et al, 2012;Xu et al, 2020).…”

Predicting phenotype from genotype: Improving accuracy through more robust experimental and computational modeling

“…Both groups (ΔEA >±1STD) demonstrated significant structural clustering (P < 0.00001), and these clusters were found at sites of particular relevance to GPCRs. Residues identified as higher scoring and of greater importance when using the narrow ADRB2 alignment clustered near the predicted dimerization interfaces of close homologs (Lee, O'Dowd, Rajaram, Nguyen, & George, 2003;Milligan, 2004), as well as the ligand-binding pocket, with several residues (F290, Y308) previously shown to be in direct contact with the ligand of ADRB2 (Plazinska, Plazinski, & Jozwiak, 2015;Rosenbaum et al, 2007). On the other hand, residues that were more important to the rest of the Class A GPCRs clustered significantly (P < 0.00001) around the extracellular loop structure, which directly binds ligand in more distant Class A GPCRs like Rhodopsin but which evolved to interact indirectly and be less essential in ADRB2 (Wheatley et al, 2011).…”