QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: mol.107.040097v1 73/3/909    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Chen, Y. Articles by Conn, P. J. Search for Related Content PubMed PubMed Citation Articles by Chen, Y. Articles by Conn, P. J.

N-{4-Chloro-2-[(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)methyl]phenyl}-2-hydroxybenzamide (CPPHA) Acts through a Novel Site as a Positive Allosteric Modulator of Group 1 Metabotropic Glutamate Receptors

Brain Institute, Vanderbilt University Medical Center, Nashville, Tennessee (Y.C.); Department of Pharmacology and Vanderbilt Program in Drug Discovery, Vanderbilt University Medical Center, Nashville, Tennessee (Y.C., P.J.C); and Institut de Génomique Fonctionnelle, Centre National de la Recherche Scientifique Unité Mixte de Recherche 5203, Institut National de la Santé et de la Recherche Médicale, U661, and Université de Montpellier (IFR3), Montpellier, France (C.G., J.-P.P.).

Recent studies suggest that a novel positive allosteric modulator (PAM) of the metabotropic glutamate receptor (mGluRs), mGluR5, termed 4-nitro-N-(1,3-diphenyl-1H-pyrazol-5-yl)benzamide (VU-29), potentiates mGluR5 responses by actions at a site that is overlapping with the binding site of 2-methyl-6-(phenylethynyl)pyridine (MPEP), a previously identified negative allosteric modulator of this receptor. It is interesting that a structurally distinct PAM, N-{4-Chloro-2-[(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)methyl]phenyl}-2-hydroxybenzamide (CPPHA), does not to bind to the MPEP site. We now report that CPPHA potentiates mGluR5 responses by a mechanism that is distinct from that of VU-29. VU-29- and CPPHA-induced potentiation of mGluR5 responses are blocked by a neutral ligand at the MPEP allosteric site termed 5-methyl-2-(phenylethynyl)pyridine (5MPEP). However, increasing concentrations of 5MPEP induce parallel rightward shifts in the VU-29 concentration-response curve, whereas 5MPEP inhibits CPPHA potentiation in a noncompetitive manner. Consistent with this, a mutation (A809V/mGluR5) that reduces binding of ligands to the MPEP site eliminates the effect of VU-29 but has no effect on the response to CPPHA. On the other hand, a mutation (F585I/mGluRs) that eliminates the effect of CPPHA does not alter the response to VU-29. CPPHA is also a PAM at mGluR1. It is interesting that the corresponding mutation of F585I/mGluR5 in mGluR1 (F599I/mGluR1) eliminates CPPHA's effect without altering the potentiation of a known PAM of mGluR1, (S)-2-(4-fluorophenyl)-1-(toluene-4-sulfonyl)pyrrolidine (Ro 67-7476). Likewise, another mutation (V757L/mGluR1) that abolishes potentiation of Ro 67-7476 has no effect on CPPHA. Finally, CPPHA does not displace binding of a radioligand for the mGluR1 allosteric antagonist characterized previously. Together, these data suggest that CPPHA acts at a novel allosteric site on both mGluR1 and -5 to potentiate responses to activation of these receptors.

Address correspondence to: Dr. P. Jeffrey Conn, Department of Pharmacology, Vanderbilt University Medical Center, 23rd Avenue South at Pierce, 417-D Preston Research Building, Nashville, TN 37232-6600. E-mail: jeff.conn{at}vanderbilt.edu