Elsevier

Neuropharmacology

Volume 36, Issue 1, January 1997, Pages 1-11
Neuropharmacology

LY354740 is a Potent and Highly Selective Group II Metabotropic Glutamate Receptor Agonist in Cells Expressing Human Glutamate Receptors

https://doi.org/10.1016/S0028-3908(96)00160-8Get rights and content

Abstract

The novel compound LY354740 is a conformationally constrained analog of glutamate, which was designed for interaction at metabotropic glutamate (mGlu) receptors. In this paper the selectivity of LY354740 for recombinant human mGlu receptor subtypes expressed in non-neuronal (RGT) cells is described. At human mGlu2 receptors, LY354740 produced >90% suppression of forskolin-stimulated cAMP formation with an ec50 of 5.1 ± 0.3 nM. LY354740 was six-fold less potent in activating human mGlu3 receptors (ec50 = 24.3 ± 0.5 nM). LY354740 inhibition of forskolin-stimulated cAMP formation in human mGlu2 receptor-expressing cells was blocked by competitive mGlu receptor antagonists, including (+)-α-methyl-4-carboxyphenylglycine (MCPG) and LY307452 ((2S,4S0-2-amino-4-(4,4-diphenylbut-1-yl)-pentane-1,5-dioic acid). LY354740 had no agonist or antagonist activities at cells expressing human mGlu4 or mGlu7 (group III mGlu receptors) (ec50s > 100 000 nM). When tested at group I phosphoinositide-coupled human mGlu receptors (mGlu1a and mGlu5a), LY354740 did not activate or inhibit mGlu receptor agonist-evoked phosphoinositide hydrolysis at up to 100 000 nM. Electrophysiological experiments also demonstrated that LY354740 also had no appreciable activity in cells expressing human recombinant AMPA (GluR4) and kainate (GluR6) receptors. Thus, LY354740 is a highly potent, efficacious and selective group II (mGlu2/3) receptor agonist, useful to explore the functions of these receptors in situ. © 1997 Elsevier Science Ltd. All rights reserved.

Section snippets

Second messenger assays in cloned human mGlu receptors

Cloned human mGlu receptors mGlu1a, mGlu2, mGlu3, mGlu4a, mGlu5a and mGlu7 were each expressed in “RGT” cells. RGT cells are AV12-664 cells (American Type Culture Collection, accession number CRL 9595) which have been stably transfected with a glutamate transporter (GLAST, Storck et al., 1992) to prevent the accumulation of glutamate into the cell media (Desai et al., 1995; Kingston et al., 1995; Schoepp et al., 1996). RGT cells expressing human mGlu receptors were seeded into 24-well culture

Activity of LY354740 at cAMP coupled human mGlu receptors

As shown in Fig. 2, LY354740 most potently inhibited forskolin-stimulated cAMP formation in cells expressing human mGlu2 receptors, producing >90% inhibition at a maximally effective concentration of 100 nM and an ec50 value of 5.1 ± 0.3 nM. LY354740 was also a full-agonist at the human mGluR3 receptor, but was about six-fold less potent than when compared to the human mGlu2 receptor (see Table 1). No appreciable agonist activity (<50% inhibition of forskolin-stimulated cAMP) was noted at group

DISCUSSION

The relatively recent cloning of a highly heterogeneous family of G-protein coupled (metabotropic) receptors has created a tremendous gap between the knowledge of the mGlu receptor subtypes versus an understanding about their cellular functions. The discovery of potent subtype selective mGlu receptor compounds is needed to further explore mGlu receptor functions and the therapeutic opportunities that may arise from selective modulation of these receptors. The availability of cell lines

Acknowledgements

We would like to thank Allelix Biopharmaceuticals for providing the human GluR4- and GluR6-expressing cells.

References (34)

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