title: Pharmacological characterization and identification of amino acids involved in the positive modulation of metabotropic glutamate receptor subtype 2.
abstract: In the present study, we describe the characterization of a positive allosteric modulator at metabotropic glutamate subtype 2 receptors (mGluR2). N-(4-(2-Methoxyphenoxy)-phenyl-N-(2,2,2-trifluoroethylsulfonyl)-pyrid-3-ylmethylamine (LY487379) is a selective positive allosteric modulator at human mGluR2 and is without activity at human mGluR3. Furthermore, LY487379 has no intrinsic agonist or antagonist activity at hmGluR2, as determined by functional guanosine 5'(gamma-[35S]thio)triphosphate ([35S]GTPgammaS) binding, single-cell Ca2+ imaging, and electrophysiological studies. However, LY487379 markedly potentiated glutamate-stimulated [35S]GTPgammaS binding in a concentration-dependent manner at hmGluR2, shifting the glutamate dose-response curve leftward by 3-fold and increasing the maximum levels of [35S]GTPgammaS stimulation. This effect of LY487479 was also observed to a greater extent on the concentration-response curves to selective hmGluR2/3 agonists. In radioligand binding studies to rat cortical membranes, LY487379 increased the affinity of the radiolabeled agonist, [3H]DCG-IV, without affecting the binding affinity of the radiolabeled antagonist, [3H]LY341495. In rat hippocampal slices, coapplication of LY487379 potentiated synaptically evoked mGluR2 responses. Finally, to elucidate the site of action, we systematically exchanged segments and single amino acids between hmGluR2 and hmGluR3. Substitution of Ser688 and/or Gly689 in transmembrane IV along with Asn735 located in transmembrane segment V, with the homologous amino acids of hmGluR3, completely eliminated LY487379 allosteric modulation of hmGluR2. We propose that this allosteric binding site defines a pocket that is different from the orthosteric site located in the amino terminal domain.
mesh_terms: D000494:Allosteric Regulation; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002540:Cerebral Cortex / Q000166:cytology; D006224:Cricetinae; D003521:Cyclopropanes / Q000494:pharmacology; D018891:Dentate Gyrus / Q000187:drug effects / Q000378:metabolism; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D019580:Perforant Pathway / Q000187:drug effects / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011725:Pyridines / Q000494:pharmacology*; D051381:Rats; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013449:Sulfonamides / Q000494:pharmacology*; D014316:Tritium; D014966:Xanthenes / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D003521:Cyclopropanes; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; C114624:LY 341495; C476436:N-(4-(2-methoxyphenoxy)phenyl)-N-(2,2,2-trifluoroethylsulfonyl)pyrid-3-ylmethylamine; D011725:Pyridines; D018094:Receptors, Metabotropic Glutamate; D013449:Sulfonamides; D014966:Xanthenes; C108822:metabotropic glutamate receptor 2; C102718:metabotropic glutamate receptor 3; D014316:Tritium; C082313:2-(2,3-dicarboxycyclopropyl)glycine; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002118:Calcium; D005998:Glycine