Structure-Based Discovery of Negative Allosteric Modulators of the Metabotropic Glutamate Receptor 5

Abstract

Recently determined structures of class C G protein-coupled receptors (GPCRs) revealed the location of allosteric binding sites and opened new opportunities for the discovery of novel modulators. In this work, molecular docking screens for allosteric modulators targeting the metabotropic glutamate receptor 5 (mGlu5) were performed. The mGlu5 receptor is activated by the main excitatory neurotransmitter of the nervous central system, L-glutamate, and mGlu5 receptor activity can be allosterically modulated by negative or positive allosteric modulators. The mGlu5 receptor is a promising target for the treatment of psychiatric and neurodegenerative diseases, and several allosteric modulators of this GPCR have been evaluated in clinical trials. Chemical libraries containing fragment- (1.6 million molecules) and lead-like (4.6 million molecules) compounds were docked to an allosteric binding site of mGlu5 identified in X-ray crystal structures. Among the top-ranked compounds, 59 fragments and 59 lead-like compounds were selected for experimental evaluation. Of these, four fragment- and seven lead-like compounds were confirmed to bind to the allosteric site with affinities ranging from 0.43 to 8.6 μM, corresponding to a hit rate of 9%. The four compounds with the highest affinities were demonstrated to be negative allosteric modulators of mGlu5 signaling in functional assays. The results demonstrate that virtual screens of fragment- and lead-like chemical libraries have complementary advantages and illustrate how access to high-resolution structures of GPCRs in complex with allosteric modulators can accelerate lead discovery.

Small molecule allosteric modulation of the adenosine A1 receptor

“…Such structural determination has provided key insights into allosteric binding across various GPCRs, which in turns aids the discovery of new allosteric modulators using the structure-based drug discovery (SBDD) approach. Several SBDD studies have successfully employed to find new allosteric modulators for GPCRs, including M2 muscarinic acetylcholine receptors ( 144 , 145 ), glucagon-like peptide 1 receptor ( 146 – 148 ), metabotropic glutamate receptor 5 ( 149 ), and proton-sensing receptors GPR68 and GPR65 ( 150 ). These studies demonstrate the power of SBDD to identify new allosteric modulators for GPCRs, paving the way for the development of novel therapeutics with improved selectivity and reduced side effects.…”

A novel heuristic of rigid docking scores positively correlates with full-length nuclear receptor LRH-1 regulation.

“…Still, the speed, accessibility and low cost of computational docking provides an attractive way to prioritize compounds [21,22]. Thus, there is a need for docking approaches that have been validated with wet-lab data, correlating docking scores with compound activity in cell-based assays [2][3][4]23,24] particularly for allosterically-regulated targets [5,20,22]. Here, we discovered and validated one such approach, retrospectively correlating published cell-based functional data [1] with new rigidbody docking of compounds to Liver Receptor Homolog-1 (LRH-1, NR5A2), an allosterically regulated nuclear receptor and drug target for several human diseases.…”

“…Computational docking has been used to help prioritize compounds [14], which can improve the hit rate from secondary assays [2][3][4][5][6]15]. However, little wet-lab data are available validating direct relationships between docking scores and functional regulation in cells [16][17][18], particularly for non-enzyme allosterically-regulated target proteins [19,20]. Still, the speed, accessibility and low cost of computational docking provides an attractive way to prioritize compounds [21,22].…”

The novel peptide LCGM-10 attenuates metabotropic glutamate receptor 5 activity and demonstrates behavioral effects in animal models

“…mGluR5 is expressed at high levels in several brain regions ( Brain tissue expression of GRM5, n.d. ) and is involved in a multitude of brain-related illnesses ( Su et al, 2022 ) including fragile X syndrome (FXS) ( Bear et al, 2004 ; Brašić et al, 2022 ), depression ( Pilc et al, 2008 ; Esterlis et al, 2022 ), Parkinson’s disease ( Pisani et al, 2003 ; Azam et al, 2022 ), Alzheimer’s disease ( Sokol et al, 2011 ), attention deficit hyperactivity disorder (ADHD) ( Elia et al, 2010 ), and addictions ( Niedzielska-Andres et al, 2021 ). Because direct-acting agonists produce substantial adverse effects and eventually lead to profound receptor desensitization, the development of allosteric modulators has been at the forefront of G protein–coupled receptor (GPCR) drug development ( Marino and Conn, 2006 ; Kampen et al, 2022 ). Negative allosteric modulators (NAMs) and positive allosteric modulators (PAMs) will only modulate receptor activity in the presence of the endogenous agonist, which is not possible with orthosteric ligands and enables more specific control of the tissue response ( Wood et al, 2011 ; Stansley and Conn, 2019 ).…”