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Metabotropic glutamate (mGlu) receptors are promising targets to treat numerous brain disorders. So far, allosteric modulators are the only subtype selective ligands, but pure agonists still have strong therapeutic potential. Here, we aimed at investigating the possibility of developing subtype-selective agonists by extending the glutamate-like structure to hit a nonconsensus binding area. We report the properties of the first mGlu4-selective orthosteric agonist, derived from a virtual screening hit, LSP4-2022 using cell-based assays with recombinant mGlu receptors [EC(50): 0.11 ± 0.02, 11.6 ± 1.9, 29.2 ± 4.2 μM (n>19) in calcium assays on mGlu4, mGlu7, and mGlu8 receptors, respectively, with no activity at the group I and -II mGlu receptors at 100 μM]. LSP4-2022 inhibits neurotransmission in cerebellar slices from wild-type but not mGlu4 receptor-knockout mice. In vivo, it possesses antiparkinsonian properties after central or systemic administration in a haloperidol-induced catalepsy test, revealing its ability to cross the blood-brain barrier. Site-directed mutagenesis and molecular modeling was used to identify the LSP4-2022 binding site, revealing interaction with both the glutamate binding site and a variable pocket responsible for selectivity. These data reveal new approaches for developing selective, hydrophilic, and brain-penetrant mGlu receptor agonists, offering new possibilities to design original bioactive compounds with therapeutic potential.

Original publication

DOI

10.1096/fj.11-195941

Type

Journal article

Journal

FASEB J

Publication Date

04/2012

Volume

26

Pages

1682 - 1693

Keywords

Animals, Antiparkinson Agents, Binding Sites, Dose-Response Relationship, Drug, Excitatory Amino Acid Agonists, HEK293 Cells, Humans, Ligands, Male, Mice, Mice, Knockout, Molecular Structure, Mutagenesis, Site-Directed, Patch-Clamp Techniques, Phosphinic Acids, Rats, Rats, Wistar, Receptors, Metabotropic Glutamate, Recombinant Proteins, Structure-Activity Relationship, Synaptic Transmission