Reverse engineering of the selective agonist TBPB unveils both orthosteric and allosteric modes of action at the M1 muscarinic acetylcholine receptor

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Recent interest in the M1 muscarinic acetylcholine (ACh) receptor (mAChR) has led to the discovery of various selective agonists for the receptor. The novel selective agonist, 1-(1 -(2-methylbenzyl)-1,4 -bipiperidin-4-yl)-1H-benzo[d]imidazol-2(3H)-one (TBPB), displays unprecedented functional selectivity at the M1 mAChR. This functional selectivity has been described to stem from sole interaction with an allosteric site, although the evidence for such a mechanism is equivocal. To delineate TBPB s mechanism of action, several truncated variants of TBPB were synthesised and characterised. Binding experiments with [3H]-N-methylscopolamine ([3H]-NMS) at the M1, M2, M3 and M4 mAChRs revealed radioligand displacement in a manner consistent with a competitive binding mode at the orthosteric site by TBPB and fragment derivatives. Cell-based functional assays of fragment derivatives of TBPB identified both agonistic and antagonistic moieties, one of which, VCP794, lost agonistic selectivity for the M1 mAChR. Further interaction experiments between TBPB or its antagonist fragments with ACh also indicated a mechanism consistent with competitive binding at mAChRs. However, interaction with an allosteric site by an antagonist fragment of TBPB was demonstrated via its ability to retardation radioligand dissociation. To reconcile this dual orthosteric/allosteric pharmacological behaviour, we propose that TBPB is a bitopic ligand, interacting with both the orthosteric site and an allosteric site, at the M1 mAChR. This mechanism may also be the case for other selective agonists for mAChRs, and should be taken into consideration in the profiling and classification of new novel selective agonists for this receptor family.
Original languageEnglish
Pages (from-to)425 - 437
Number of pages13
JournalMolecular Pharmacology
Volume84
Issue number3
DOIs
Publication statusPublished - 2013

Cite this

@article{8ea8993d25bb40e481a68e3e9846ca7f,
title = "Reverse engineering of the selective agonist TBPB unveils both orthosteric and allosteric modes of action at the M1 muscarinic acetylcholine receptor",
abstract = "Recent interest in the M1 muscarinic acetylcholine (ACh) receptor (mAChR) has led to the discovery of various selective agonists for the receptor. The novel selective agonist, 1-(1 -(2-methylbenzyl)-1,4 -bipiperidin-4-yl)-1H-benzo[d]imidazol-2(3H)-one (TBPB), displays unprecedented functional selectivity at the M1 mAChR. This functional selectivity has been described to stem from sole interaction with an allosteric site, although the evidence for such a mechanism is equivocal. To delineate TBPB s mechanism of action, several truncated variants of TBPB were synthesised and characterised. Binding experiments with [3H]-N-methylscopolamine ([3H]-NMS) at the M1, M2, M3 and M4 mAChRs revealed radioligand displacement in a manner consistent with a competitive binding mode at the orthosteric site by TBPB and fragment derivatives. Cell-based functional assays of fragment derivatives of TBPB identified both agonistic and antagonistic moieties, one of which, VCP794, lost agonistic selectivity for the M1 mAChR. Further interaction experiments between TBPB or its antagonist fragments with ACh also indicated a mechanism consistent with competitive binding at mAChRs. However, interaction with an allosteric site by an antagonist fragment of TBPB was demonstrated via its ability to retardation radioligand dissociation. To reconcile this dual orthosteric/allosteric pharmacological behaviour, we propose that TBPB is a bitopic ligand, interacting with both the orthosteric site and an allosteric site, at the M1 mAChR. This mechanism may also be the case for other selective agonists for mAChRs, and should be taken into consideration in the profiling and classification of new novel selective agonists for this receptor family.",
author = "Peter Keov and Celine Valant and Shane Devine and Lane, {Jonathan Robert} and Scammells, {Peter John} and Patrick Sexton and Arthur Christopoulos",
year = "2013",
doi = "10.1124/mol.113.087320",
language = "English",
volume = "84",
pages = "425 -- 437",
journal = "Molecular Pharmacology",
issn = "1521-0111",
publisher = "ACS Books",
number = "3",

}

TY - JOUR

T1 - Reverse engineering of the selective agonist TBPB unveils both orthosteric and allosteric modes of action at the M1 muscarinic acetylcholine receptor

AU - Keov, Peter

AU - Valant, Celine

AU - Devine, Shane

AU - Lane, Jonathan Robert

AU - Scammells, Peter John

AU - Sexton, Patrick

AU - Christopoulos, Arthur

PY - 2013

Y1 - 2013

N2 - Recent interest in the M1 muscarinic acetylcholine (ACh) receptor (mAChR) has led to the discovery of various selective agonists for the receptor. The novel selective agonist, 1-(1 -(2-methylbenzyl)-1,4 -bipiperidin-4-yl)-1H-benzo[d]imidazol-2(3H)-one (TBPB), displays unprecedented functional selectivity at the M1 mAChR. This functional selectivity has been described to stem from sole interaction with an allosteric site, although the evidence for such a mechanism is equivocal. To delineate TBPB s mechanism of action, several truncated variants of TBPB were synthesised and characterised. Binding experiments with [3H]-N-methylscopolamine ([3H]-NMS) at the M1, M2, M3 and M4 mAChRs revealed radioligand displacement in a manner consistent with a competitive binding mode at the orthosteric site by TBPB and fragment derivatives. Cell-based functional assays of fragment derivatives of TBPB identified both agonistic and antagonistic moieties, one of which, VCP794, lost agonistic selectivity for the M1 mAChR. Further interaction experiments between TBPB or its antagonist fragments with ACh also indicated a mechanism consistent with competitive binding at mAChRs. However, interaction with an allosteric site by an antagonist fragment of TBPB was demonstrated via its ability to retardation radioligand dissociation. To reconcile this dual orthosteric/allosteric pharmacological behaviour, we propose that TBPB is a bitopic ligand, interacting with both the orthosteric site and an allosteric site, at the M1 mAChR. This mechanism may also be the case for other selective agonists for mAChRs, and should be taken into consideration in the profiling and classification of new novel selective agonists for this receptor family.

AB - Recent interest in the M1 muscarinic acetylcholine (ACh) receptor (mAChR) has led to the discovery of various selective agonists for the receptor. The novel selective agonist, 1-(1 -(2-methylbenzyl)-1,4 -bipiperidin-4-yl)-1H-benzo[d]imidazol-2(3H)-one (TBPB), displays unprecedented functional selectivity at the M1 mAChR. This functional selectivity has been described to stem from sole interaction with an allosteric site, although the evidence for such a mechanism is equivocal. To delineate TBPB s mechanism of action, several truncated variants of TBPB were synthesised and characterised. Binding experiments with [3H]-N-methylscopolamine ([3H]-NMS) at the M1, M2, M3 and M4 mAChRs revealed radioligand displacement in a manner consistent with a competitive binding mode at the orthosteric site by TBPB and fragment derivatives. Cell-based functional assays of fragment derivatives of TBPB identified both agonistic and antagonistic moieties, one of which, VCP794, lost agonistic selectivity for the M1 mAChR. Further interaction experiments between TBPB or its antagonist fragments with ACh also indicated a mechanism consistent with competitive binding at mAChRs. However, interaction with an allosteric site by an antagonist fragment of TBPB was demonstrated via its ability to retardation radioligand dissociation. To reconcile this dual orthosteric/allosteric pharmacological behaviour, we propose that TBPB is a bitopic ligand, interacting with both the orthosteric site and an allosteric site, at the M1 mAChR. This mechanism may also be the case for other selective agonists for mAChRs, and should be taken into consideration in the profiling and classification of new novel selective agonists for this receptor family.

UR - http://molpharm.aspetjournals.org/content/84/3/425.full.pdf+html

U2 - 10.1124/mol.113.087320

DO - 10.1124/mol.113.087320

M3 - Article

VL - 84

SP - 425

EP - 437

JO - Molecular Pharmacology

JF - Molecular Pharmacology

SN - 1521-0111

IS - 3

ER -