An Allosteric Modulator of α7 Nicotinic Receptors, N-(5-Chloro-2,4-dimethoxyphenyl)-Nâ²-(5-methyl-3-isoxazolyl)-urea (PNU-120596), Causes Conformational Changes in the Extracellular Ligand Binding Domain Similar to Those Caused by Acetylcholine
Nicotinic acetylcholine receptors are implicated in several neuropsychiatric disorders, including nicotine addiction, Alzheimer's, schizophrenia, and depression. Therefore, they represent a critical molecular target for drug development and targeted therapeutic intervention. Understanding the m...
Saved in:
Published in | Molecular pharmacology Vol. 76; no. 2; p. 253 |
---|---|
Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
American Society for Pharmacology and Experimental Therapeutics
01.08.2009
|
Online Access | Get full text |
Cover
Loading…
Summary: | Nicotinic acetylcholine receptors are implicated in several neuropsychiatric disorders, including nicotine addiction, Alzheimer's,
schizophrenia, and depression. Therefore, they represent a critical molecular target for drug development and targeted therapeutic
intervention. Understanding the molecular mechanisms by which allosteric modulators enhance activation of these receptors
is crucial to the development of new drugs. We used the substituted cysteine accessibility method to study conformational
changes induced by the positive allosteric modulator N -(5-chloro-2,4-dimethoxyphenyl)- N â²-(5-methyl-3-isoxazolyl)-urea (PNU-120596) in the extracellular ligand binding domain of α7 nicotinic receptors carrying
the L247T mutation. PNU-120596 caused changes in cysteine accessibility at the inner beta sheet, transition zone, and agonist
binding site. These changes in accessibility are similar to but not identical to those caused by ACh alone. In particular,
PNU-120596 induced changes in MTSEA accessibility at N170C (in the transition zone) that were substantially different from
those evoked by acetylcholine (ACh). We found that PNU-120596 induced changes at position E172C in the absence of allosteric
modulation. We identified a cysteine mutation of the agonist binding site (W148C) that exhibited an unexpected phenotype in
which PNU-120596 acts as a full agonist. In this mutant, ACh-evoked currents were more sensitive to thiol modification than
PNU-evoked currents, suggesting that PNU-120596 does not bind at unoccupied agonist-binding sites. Our results provide evidence
that binding sites for PNU-120596 are not in the agonist-binding sites and demonstrate that positive allosteric modulators
such as PNU-120596 enhance agonist-evoked gating of nicotinic receptors by eliciting conformational effects that are similar
but nonidentical to the gating conformations promoted by ACh. |
---|---|
ISSN: | 0026-895X 1521-0111 |
DOI: | 10.1124/mol.109.056226 |