Molecular determinants of allosteric modulation at the M1 muscarinic acetylcholine receptor

Abdul-Ridha, Alaa; L�pez, Laura; Keov, Peter; Thal, David M.; Mistry, Shailesh N.; Sexton, Patrick M.; Lane, J. Robert; Canals, Meritxell; Christopoulos, Arthur

Abstract

Benzylquinolone carboxylic acid (BQCA) is an unprecedented example of a selective positive allosteric modulator of acetylcholine at the M1 muscarinic acetylcholine receptor (mAChR). To probe the structural basis underlying its selectivity, we utilized site-directed mutagenesis, analytical modeling, and molecular dynamics to delineate regions of the M1 mAChR that govern modulator binding and transmission of cooperativity. We identified Tyr-852.64 in transmembrane domain 2 (TMII), Tyr-179 and Phe-182 in the second extracellular loop (ECL2), and Glu-3977.32 and Trp-4007.35 in TMVII as residues that contribute to the BQCA binding pocket at the M1 mAChR, as well as to the transmission of cooperativity with the orthosteric agonist carbachol. As such, the BQCA binding pocket partially overlaps with the previously described "common" allosteric site in the extracellular vestibule of the M1 mAChR, suggesting that its high subtype selectivity derives from either additional contacts outside this region or through a subtype-specific cooperativity mechanism. Mutation of amino acid residues that form the orthosteric binding pocket caused a loss of carbachol response that could be rescued by BQCA. Two of these residues (Leu-1023.29 and Asp-1053.32) were also identified as indirect contributors to the binding affinity of the modulator. This new insight into the structural basis of binding and function of BQCA can guide the design of new allosteric ligands with tailored pharmacological properties. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

Citation

Abdul-Ridha, A., López, L., Keov, P., Thal, D. M., Mistry, S. N., Sexton, P. M., …Christopoulos, A. (2014). Molecular determinants of allosteric modulation at the M1 muscarinic acetylcholine receptor. Journal of Biological Chemistry, 289(9), 6067-6079. https://doi.org/10.1074/jbc.M113.539080

• Journal Article Type: Article
• Acceptance Date: Jan 16, 2014
• Online Publication Date: Jan 17, 2014
• Publication Date: Feb 28, 2014
• Deposit Date: Oct 9, 2015
• Publicly Available Date: Oct 9, 2015
• Journal: Journal of Biological Chemistry
• Electronic ISSN: 0021-9258
• Publisher: American Society for Biochemistry and Molecular Biology
• Peer Reviewed: Peer Reviewed
• Volume: 289
• Issue: 9
• Pages: 6067-6079
• DOI: https://doi.org/10.1074/jbc.M113.539080
• Keywords: Allosteric modulation; Molecular determinants; Muscarinic acetylcholine receptors; Muscarinic acetylcholine receptors (machr); Pharmacological properties; Positive allosteric modulator; Site directed mutagenesis; Trans-membrane domains; Activation analysi
• Public URL: https://nottingham-repository.worktribe.com/output/721457
• Publisher URL: http://www.jbc.org/content/289/9/6067
• Additional Information: This research was originally published in Journal of Biological Chemistry. Alaa Abdul-Ridha, Laura López, Peter Keov, David M. Thal, Shailesh N. Mistry, Patrick M. Sexton, Meritxell Canals and Arthur Christopoulos. Molecular determinants of allosteric modulation at the M1 muscarinic acetylcholine receptor. Journal of Biological Chemistry. 2014. 289:6067-6079. © the American Society for Biochemistry and Molecular Biology.