Allosterism at Muscarinic Receptors: Ligands and Mechanisms

Birdsall, N. J. M.; Lazareno, Sebastian

doi:10.2174/1389557054023251

Cited by 104 publications

(102 citation statements)

References 126 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Many GPCRs, including mAChRs (12), have allosteric binding sites bound by small molecules that activate the receptor in the absence of ligand (allosteric agonist) or enhance the response to native ligand (positive allosteric modulator) (13). As allosteric sites are theoretically under less evolutionary constraint, targeting them affords opportunities for selectivity.…”

mentioning

confidence: 99%

Selective activation of the M ₁ muscarinic acetylcholine receptor achieved by allosteric potentiation

Ma¹,

Seager²,

Wittmann³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

256

314

View full text Add to dashboard Cite

The forebrain cholinergic system promotes higher brain function in part by signaling through the M1 muscarinic acetylcholine receptor (mAChR). During Alzheimer's disease (AD), these cholinergic neurons degenerate, therefore selectively activating M1 receptors could improve cognitive function in these patients while avoiding unwanted peripheral responses associated with non-selective muscarinic agonists. We describe here benzyl quinolone carboxylic acid (BQCA), a highly selective allosteric potentiator of the M1 mAChR. BQCA reduces the concentration of ACh required to activate M1 up to 129-fold with an inflection point value of 845 nM. No potentiation, agonism, or antagonism activity on other mAChRs is observed up to 100 μM. Furthermore studies in M1−/− mice demonstrates that BQCA requires M1 to promote inositol phosphate turnover in primary neurons and to increase c-fos and arc RNA expression and ERK phosphorylation in the brain. Radioligand-binding assays, molecular modeling, and site-directed mutagenesis experiments indicate that BQCA acts at an allosteric site involving residues Y179 and W400. BQCA reverses scopolamine-induced memory deficits in contextual fear conditioning, increases blood flow to the cerebral cortex, and increases wakefulness while reducing delta sleep. In contrast to M1 allosteric agonists, which do not improve memory in scopolamine-challenged mice in contextual fear conditioning, BQCA induces β-arrestin recruitment to M1, suggesting a role for this signal transduction mechanism in the cholinergic modulation of memory. In summary, BQCA exploits an allosteric potentiation mechanism to provide selectivity for the M1 receptor and represents a promising therapeutic strategy for cognitive disorders.

show abstract

mentioning

confidence: 99%

Selective activation of the M ₁ muscarinic acetylcholine receptor achieved by allosteric potentiation

Ma¹,

Seager²,

Wittmann³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

256

314

View full text Add to dashboard Cite

show abstract

“…Activation of M1 muscarinic receptors has been shown to occur with orthosteric agonists and allosteric potentiators requiring the presence of orthosteric agonists to produce activation (Matsui et al, 1995;Lazareno et al, 1998;Birdsall and Lazareno, 2005;Ma et al, 2009;Marlo et al, 2009). Furthermore, selective M1 receptor allosteric agonists, exemplified by AC-42 (Spalding et al, 2002; and TBPB (Jones et al, 2008), modulate receptor activation without requirement for orthosteric agonists.…”

Section: Discussionmentioning

confidence: 99%

The M1 Muscarinic Receptor Allosteric Agonists AC-42 and 1-[1′-(2-Methylbenzyl)-1,4′-bipiperidin-4-yl]-1,3-dihydro-2H-benzimidazol-2-one Bind to a Unique Site Distinct from the Acetylcholine Orthosteric Site

Jacobson¹,

Kreatsoulas²,

Pascarella³

et al. 2010

Mol Pharmacol

View full text Add to dashboard Cite

Activation of M1 muscarinic receptors occurs through orthosteric and allosteric binding sites. To identify critical residues, site-directed mutagenesis and chimeric receptors were evaluated in functional calcium mobilization assays to compare orthosteric agonists, acetylcholine and xanomeline, M1 allosteric agonists AC-42, and the clozapine metabolite N-desmethylclozapine. A minimal epitope has been defined for AC-42 that comprises the first 45 amino acids, the third extracellular loop, and seventh transmembrane domain (Mol Pharmacol 61:1297-1302, 2002). Using chimeric M1 and M3 receptor constructs, the AC-42 minimal epitope has been extended to also include transmembrane II. Phe77 was identified as a critical residue for maintenance of AC-42 and TBPB agonist activity. In contrast, the functional activity of N-desmethylclozapine did not require Phe77. To further map the binding site of AC-42, TBPB, and N-desmethylclozapine, point mutations previously reported to affect activities of M1 orthosteric agonists and antagonists were studied. Docking into an M1 receptor homology model revealed that AC-42 and TBPB share a similar binding pocket adjacent to the orthosteric binding site at the opposite face of Trp101. In contrast, the activity of N-desmethylclozapine was generally unaffected by the point mutations studied, and the docking indicated that N-desmethylclozapine bound to a site distinct from AC-42 and TBPB overlapping with the orthosteric site. These results suggest that structurally diverse allosteric agonists AC-42, TBPB, and N-desmethylclozapine may interact with different subsets of residues, supporting the hypothesis that M1 receptor activation can occur through at least three different binding domains.

show abstract

“…In most cases, only an allosteric modulator should affect the dissociation kinetics of the radioligand. In situations in which the modulator acts at both the allosteric and orthosteric sites, it may be impossible to determine kinetically to which site the modulator binds with higher affinity (Birdsall and Lazareno, 2005). At muscarinic receptors, the problem is confounded because occupancy of the allosteric site often prevents the transit of radioligands to the orthosteric site (Proska and Tucek, 1994).…”

Section: Introductionmentioning

confidence: 99%

Mutagenesis of Nucleophilic Residues near the Orthosteric Binding Pocket of M₁and M₂Muscarinic receptors: Effect on the Binding of Nitrogen Mustard Analogs of Acetylcholine and McN-A-343

Suga¹,

Sawyer²,

Ehlert³

2010

Mol Pharmacol

View full text Add to dashboard Cite

Investigating how a test drug alters the reaction of a sitedirected electrophile with a receptor is a powerful method for determining whether the drug acts competitively or allosterically, provided that the binding site of the electrophile is known. In this study, therefore, we mutated nucleophilic residues near and within the orthosteric pockets of M 1 and M 2 muscarinic receptors to identify where acetylcholine mustard and 4-[(2-bromoethyl)methyl-amino]-2-butynyl-N-(3-chlorophenyl)carbamate (BR384) bind covalently. BR384 is the nitrogen mustard analog of [4-[[N-(3-chlorophenyl)carbamoyl]oxy]-2-butynyl]trimethylammonium chloride (McN-A-343). Mutation of the highly conserved aspartic acid in M 1 (Asp105) and M 2 (Asp103) receptors to asparagine largely prevented receptor alkylation by acetylcholine mustard, although modest alkylation still occurred at M 2 D103N at high concentrations of the mustard. Receptor alkylation by BR384 was also greatly inhibited in the M 1 D105N mutant, but some alkylation still occurred at high concentrations of the compound. In contrast, BR384 rapidly alkylated the M 2 D103N mutant. Its affinity was reduced to one tenth, however. The alkylation of M 2 D103N by BR384 was competitively inhibited by N-methylscopolamine and allosterically inhibited by gallamine. Mutation of a variety of other nucleophilic residues, some in combination with D103N, had little effect on M 2 receptor alkylation by BR384. Our results suggest that BR384 alkylates at least one residue other than the conserved aspartic acid at the ligand-binding site of M 1 and M 2 receptors. This additional residue seems to be located within or near the orthosteric-binding pocket and is not part of the allosteric site for gallamine.

show abstract

Allosterism at Muscarinic Receptors: Ligands and Mechanisms

Cited by 104 publications

References 126 publications

Selective activation of the M ₁ muscarinic acetylcholine receptor achieved by allosteric potentiation

Selective activation of the M ₁ muscarinic acetylcholine receptor achieved by allosteric potentiation

The M1 Muscarinic Receptor Allosteric Agonists AC-42 and 1-[1′-(2-Methylbenzyl)-1,4′-bipiperidin-4-yl]-1,3-dihydro-2H-benzimidazol-2-one Bind to a Unique Site Distinct from the Acetylcholine Orthosteric Site

Mutagenesis of Nucleophilic Residues near the Orthosteric Binding Pocket of M₁and M₂Muscarinic receptors: Effect on the Binding of Nitrogen Mustard Analogs of Acetylcholine and McN-A-343

Contact Info

Product

Resources

About

Allosterism at Muscarinic Receptors: Ligands and Mechanisms

Cited by 104 publications

References 126 publications

Selective activation of the M 1 muscarinic acetylcholine receptor achieved by allosteric potentiation

Selective activation of the M 1 muscarinic acetylcholine receptor achieved by allosteric potentiation

The M1 Muscarinic Receptor Allosteric Agonists AC-42 and 1-[1′-(2-Methylbenzyl)-1,4′-bipiperidin-4-yl]-1,3-dihydro-2H-benzimidazol-2-one Bind to a Unique Site Distinct from the Acetylcholine Orthosteric Site

Mutagenesis of Nucleophilic Residues near the Orthosteric Binding Pocket of M1and M2Muscarinic receptors: Effect on the Binding of Nitrogen Mustard Analogs of Acetylcholine and McN-A-343

Contact Info

Product

Resources

About

Selective activation of the M ₁ muscarinic acetylcholine receptor achieved by allosteric potentiation

Selective activation of the M ₁ muscarinic acetylcholine receptor achieved by allosteric potentiation

Mutagenesis of Nucleophilic Residues near the Orthosteric Binding Pocket of M₁and M₂Muscarinic receptors: Effect on the Binding of Nitrogen Mustard Analogs of Acetylcholine and McN-A-343