Comparison of the binding pockets of two chemically unrelated allosteric antagonists of the mGlu5 receptor and identification of crucial residues involved in the inverse agonism of MPEP
| Autor: | Martin Stahl, Pari Malherbe, Georg Jaeschke, Marie-Thérèse Zenner, Andreas Mühlemann, Paul R. Gerber, Richard H.P. Porter, Christophe Fischer, Nicole A. Kratochwil |
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| Rok vydání: | 2006 |
| Předmět: |
Models
Molecular Pyridines medicine.drug_class Stereochemistry Inositol Phosphates Receptor Metabotropic Glutamate 5 Allosteric regulation Pharmacology Receptors Metabotropic Glutamate Biochemistry Cell Line Cellular and Molecular Neuroscience chemistry.chemical_compound medicine Humans Inverse agonist Fluorometry Receptor Cells Cultured Fenobam Binding Sites Cell Membrane Imidazoles Quisqualic Acid Receptor antagonist Thiazoles Metabotropic receptor chemistry Metabotropic glutamate receptor Mutation Calcium Pharmacophore Excitatory Amino Acid Antagonists Plasmids |
| Zdroj: | Journal of Neurochemistry. 98:601-615 |
| ISSN: | 1471-4159 0022-3042 |
| Popis: | Fenobam [N-(3-chlorophenyl)-N'-(4,5-dihydro-1-methyl-4-oxo-1H-imidazole-2-yl)urea], a clinically validated non-benzodiazepine anxiolytic, has been shown to be a potent and non-competitive metabotropic glutamate (mGlu)-5 receptor antagonist. In the present study, we have used the site-directed mutagenesis coupled with three-dimensional receptor-based pharmacophore modelling to elucidate the interacting mode of fenobam within the seven-transmembrane domain (7TMD) of mGlu5 receptor and its comparison with that of 2-methyl-6-(phenylethynyl)pyridine (MPEP), the prototype antagonist. The common residues involved in the recognition of MPEP and fenobam include Pro654(3.36), Tyr658(3.40), Thr780(6.44), Trp784(6.48), Phe787(6.51), Tyr791(6.55) and Ala809(7.47). The differentiating residues between both modulators' interacting modes are Arg647(3.29), Ser657(3.39) and Leu743(5.47). Our data suggest that these chemically unrelated mGlu5 antagonists act similarly, probing a functionally unique region of the 7TMD. Using [3H]inositol phosphates accumulation assay, we have also identified the critical residues involved in the inverse agonist effect of MPEP. The mutation W784(6.48)A completely blocked the inverse agonist activity of MPEP; two mutations F787(6.51)A and Y791(6.55)A, caused a drastic decrease in the MPEP inverse agonism. Furthermore, these three mutations led to an increased efficacy of quisqualate without having any effect on its potency. The fact that the residues Trp784(6.48) and Phe787(6.51) are essential equally in antagonism and inverse agonism effects emphasizes again the key role of these residues and the involvement of a common transmembrane network in receptor inactivation by MPEP. |
| Databáze: | OpenAIRE |
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