Pharmacological hallmarks of allostery at the M4 muscarinic receptor elucidated through structure and dynamics

Ziva Vuckovic, Jinan Wang, Vi Pham, Jesse I. Mobbs, Matthew J. Belousoff, Apurba Bhattarai, Wessel A.C. Burger, Geoff Thompson, Mahmuda Yeasmin, Vindhya Nawaratne, Katie Leach, Emma T. van der Westhuizen, Elham Khajehali, Yi Lynn Liang, Alisa Glukhova, Denise Wootten, Craig W. Lindsley, Andrew Tobin, Patrick Sexton, Radostin DanevCeline Valant, Yinglong Miao, Arthur Christopoulos, David M. Thal

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Abstract

Allosteric modulation of G protein-coupled receptors (GPCRs) is a major paradigm in drug discovery. Despite decades of research, a molecular-level understanding of the general principles that govern the myriad pharmacological effects exerted by GPCR allosteric modulators remains limited. The M4 muscarinic acetylcholine receptor (M4 mAChR) is a validated and clinically relevant allosteric drug target for several major psychiatric and cognitive disorders. In this study, we rigorously quantified the affinity, efficacy, and magnitude of modulation of two different positive allosteric modu-lators, LY2033298 (LY298) and VU0467154 (VU154), combined with the endogenous agonist acetyl-choline (ACh) or the high-affinity agonist iperoxo (Ipx), at the human M4 mAChR. By determining the cryo-electron microscopy structures of the M4 mAChR, bound to a cognate Gi1 protein and in complex with ACh, Ipx, LY298-Ipx, and VU154-Ipx, and applying molecular dynamics simulations, we determine key molecular mechanisms underlying allosteric pharmacology. In addition to delineating the contri-bution of spatially distinct binding sites on observed pharmacology, our findings also revealed a vital role for orthosteric and allosteric ligand–receptor–transducer complex stability, mediated by confor-mational dynamics between these sites, in the ultimate determination of affinity, efficacy, cooperativity, probe dependence, and species variability. There results provide a holistic framework for further GPCR mechanistic studies and can aid in the discovery and design of future allosteric drugs.

Original languageEnglish
Article numbere83477
Number of pages52
JournaleLife
Volume12
DOIs
Publication statusPublished - 30 May 2023

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