Allosteric coupling from G protein to the agonist-binding pocket in GPCRs

• Published in: Nature (London) 2016-07, Vol.535 (7610), p.182-186
• Main Authors: DeVree, Brian T., Mahoney, Jacob P., Vélez-Ruiz, Gisselle A., Rasmussen, Soren G. F., Kuszak, Adam J., Edwald, Elin, Fung, Juan-Jose, Manglik, Aashish, Masureel, Matthieu, Du, Yang, Matt, Rachel A., Pardon, Els, Steyaert, Jan, Kobilka, Brian K., Sunahara, Roger K.
• Format: Article
• Language: English
• Subjects: 101/1; 631/45/612/194; 82; 82/1; 82/80; 82/83; 96; 96/95; Adrenergic beta-2 Receptor Agonists - metabolism; Adrenergic beta-2 Receptor Antagonists - metabolism; Allosteric Regulation - drug effects; Allosteric Site - drug effects; Binding sites; Cells; Cellular biology; G proteins; GTP-Binding Protein alpha Subunits, Gs - metabolism; GTP-Binding Protein alpha Subunits, Gs - pharmacology; Guanine - metabolism; Guanine - pharmacology; Health aspects; Humanities and Social Sciences; Humans; Kinetics; letter; Ligands; Models, Molecular; multidisciplinary; Observations; Protein Binding - drug effects; Protein Conformation - drug effects; Protein-protein interactions; Proteins; Receptors, Adrenergic, beta-2 - chemistry; Receptors, Adrenergic, beta-2 - immunology; Receptors, Adrenergic, beta-2 - metabolism; Science; Single-Chain Antibodies - immunology; Single-Chain Antibodies - pharmacology
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature18324

Here, pharmacological and biochemical evidence is provided that shows that G-protein coupling to the β 2 -adrenergic receptor stabilizes a ‘closed’ conformation of the G-protein-coupled receptor (GPCR) and that that the effects of the G protein on the ligand-binding site of the GPCR are observed even in the absence of a bound agonist. Agonist binding in GPCRs Signalling via G-protein-coupled receptors (GPCRs) is the primary mechanism by which cells detect environmental stimuli and communicate with each other. Upon activation by extracellular agonists, these membrane proteins interact with intracellular G proteins to regulate downstream second messenger and/or protein kinase cascades. This study presents pharmacological and biochemical evidence to shows that G-protein coupling to the β 2 -adrenergic receptor (β 2 AR) stabilizes a 'closed' conformation of the GPCR. The effects of the G protein on the ligand-binding site of the GPCR are observed even in the absence of a bound agonist. This means that binding of the G protein to the GPCR can prevent any ligand — agonists, partial agonists, antagonists and inverse agonists — from interacting with the GPCR. Ligands that have already bound to the GPCR are unable to dissociate from the receptor when the G protein is present. The effects of nucleotide-free G protein on ligand-binding kinetics are shared by other GPCRs, suggesting that a common mechanism may underlie G-protein-mediated enhancement of agonist affinity. G-protein-coupled receptors (GPCRs) remain the primary conduit by which cells detect environmental stimuli and communicate with each other 1 . Upon activation by extracellular agonists, these seven-transmembrane-domain-containing receptors interact with heterotrimeric G proteins to regulate downstream second messenger and/or protein kinase cascades 1 . Crystallographic evidence from a prototypic GPCR, the β 2 -adrenergic receptor (β 2 AR), in complex with its cognate G protein, Gs, has provided a model for how agonist binding promotes conformational changes that propagate through the GPCR and into the nucleotide-binding pocket of the G protein α-subunit to catalyse GDP release, the key step required for GTP binding and activation of G proteins 2 . The structure also offers hints about how G-protein binding may, in turn, allosterically influence ligand binding. Here we provide functional evidence that G-protein coupling to the β 2 AR stabilizes a ‘closed’ receptor conformation characterized by restricte