Concerted conformational dynamics and water movements in the ghrelin G protein-coupled receptor.

Maxime Louet,Antoniel As Gomes,Khoubaib Ben Haj Salah,David Perahia,Pedro Renault,Jean-Louis Banères,Laurent J Catoire,Jean-Alain Fehrentz,Sophie Mary,Mauricio Gs Costa,Paulo M Bisch,Marina Casiraghi,Severine Denoyelle,Marjorie Damian,Sonia Cantel,Nicolas Floquet,Céline M'Kadmi,Paulo R Batista

doi:10.7554/elife.63201

Abstract

There is increasing support for water molecules playing a role in signal propagation through G protein-coupled receptors (GPCRs). However, exploration of the hydration features of GPCRs is still in its infancy. Here, we combined site-specific labeling with unnatural amino acids to molecular dynamics to delineate how local hydration of the ghrelin receptor growth hormone secretagogue receptor (GHSR) is rearranged upon activation. We found that GHSR is characterized by a specific hydration pattern that is selectively remodeled by pharmacologically distinct ligands and by the lipid environment. This process is directly related to the concerted movements of the transmembrane domains of the receptor. These results demonstrate that the conformational dynamics of GHSR are tightly coupled to the movements of internal water molecules, further enhancing our understanding of the molecular bases of GPCR-mediated signaling.

Highlights

G protein-coupled receptors (GPCRs) are major players in many central biological processes (Lagerstrom and Schioth, 2008)
Using the emission properties of a particular unnatural amino acids (UAAs) whose fluorescence emission properties are related to its hydration (Amaro et al, 2015; Choudhury et al, 2008), we found here that the ghrelin receptor hydration pattern is likely remodeled by orthosteric ligands and the lipid environment
We used L-(7-hydroxycoumarin-4-yl)-ethylglycine as a reporter of receptor local hydration. This UAA contains the L-(7-hydroxycoumarin-4-yl) (7H4MC) moiety whose emission properties are correlated to the presence of water molecules in its vicinity (Amaro et al, 2015). 7H4MC-ethylglycine was synthesized as described in the Materials and methods section and introduced in growth hormone secretagogue receptor (GHSR) using codon suppression technology (Wang et al, 2006)

Summary

Introduction

G protein-coupled receptors (GPCRs) are major players in many central biological processes (Lagerstrom and Schioth, 2008). The diversity in the signaling properties of GPCRs indicates that this process cannot be fully described by the limited number of conformational states captured by X-ray crystallography and cryoelectron microscopy (cryo-EM). GPCRs likely explore complex conformational landscapes, characterized by several meta-stable structural states. The relative distribution of these states is controlled by ligands, signaling proteins, and the environment, dictating the signaling output (Casiraghi et al, 2019; Hilger et al, 2018; Wingler and Lefkowitz, 2020). The conformational dynamics of GPCRs and its modulation by the receptor’s environment are under intense scrutiny, as this should illuminate how signal transduction occurs. Many GPCR experimental structures indicate the occurrence of water molecules within their transmembrane (TM) regions

Methods

Results

Conclusion