N-Methyl-d-aspartate (NMDA) Receptor NR2 Subunit Selectivity of a Series of Novel Piperazine-2,3-dicarboxylate Derivatives: Preferential Blockade of Extrasynaptic NMDA Receptors in the Rat Hippocampal CA3-CA1 Synapse

Abstract

N-Methyl-d-aspartate (NMDA) receptor antagonists that are highly selective for specific NMDA receptor 2 (NR2) subunits have several potential therapeutic applications; however, to date, only NR2B-selective antagonists have been described. Whereas most glutamate binding site antagonists display a common pattern of NR2 selectivity, NR2A> NR2B > NR2C > NR2D (high to low affinity), (2S*,3R*)-1-(phenanthrene-2-carbonyl)piperazine-2,3-dicarboxylic acid (PPDA) has a low selectivity for NR2C- and NR2D-containing NMDA receptors. A series of PPDA derivatives were synthesized and then tested at recombinant NMDA receptors expressed in Xenopus laevis oocytes. In addition, the optical isomers of PPDA were resolved; the (-) isomer displayed a 50- to 80-fold greater potency than the (+) isomer. Replacement of the phenanthrene moiety of PPDA with naphthalene or anthracene did not improve selectivity. However, phenylazobenzoyl (UBP125) or phenylethynylbenzoyl (UBP128) substitution significantly improved selectivity for NR2B-, NR2C-, and NR2D-containing receptors over NR2A-containing NMDA receptors. Phenanthrene attachment at the 3 position [(2R*,3S*)-1-(phenanthrene-3-carbonyl)piperazine-2,3-dicarboxylic acid (UBP141); (2R*,3S*)-1-(9-bromophenanthrene-3-carbonyl)piperazine-2,3-dicarboxylic acid (UBP145); (2R*,3S*)-1-(9-chlorophenanthrene-3-carbonyl)piperazine-2,3-dicarboxylic acid (UBP160); and (2R*,3S*)-1-(9-iodophenanthrene-3-carbonyl)piperazine-2,3-dicarboxylic acid (UBP161)] displayed improved NR2D selectivity. UBP141 and its 9-brominated homolog (UBP145) both display a 7- to 10- fold selectivity for NR2D-containing receptors over NR2B- or NR2A-containing receptors. Schild analysis indicates that these two compounds are competitive glutamate binding site antagonists. Consistent with a physiological role for NR2D-containing receptors in the hippocampus, UBP141 (5 muM) displayed greater selectivity than PPDA for inhibiting the slow-decaying component of the NMDA receptor-mediated CA3-CA1 synaptic response in rat hippocampal slices. UBP125, UBP128, UBP141, and UBP145 may be useful tools for determining the function of NMDA receptor subtypes.

Structural basis of subunit selectivity for competitive NMDA receptor antagonists with preference for GluN2A over GluN2B subunits

“…The 15-fold preference of ST3 for inhibition of GluN1/2A over GluN1/2B receptors is improved compared with described GluN2A-preferring competitive antagonists (15,(41)(42)(43). However, our kinetic modeling and fast-application patch-clamp recordings suggest that 15-fold subunit preference is not sufficient to fully distinguish between GluN1/2A and GluN1/2B receptors under conditions relevant to synaptic transmission (Fig.…”

Glutamate Receptor Ion Channels: Structure, Regulation, and Function

“…Subsequent determination of K B from Schild analysis suggested that the selectivity was only ϳ5-fold, precluding its use as a selective tool (Frizelle et al, 2006;Neyton and Paoletti, 2006). Antagonists with bulky, hydrophobic substituents, such as phenanthrene-piperazine dicarboxylic acid analogs (2S,3R)-1-(phenanthren-2-carbonyl)piperazine-2,3-dicarboxylic acid and (2R,3S)-1-(phenanthrenyl-3-carbonyl)piperazine-2,3-dicarboxylic acid (UBP141), show only modest 10-fold higher affinity for GluN2C-and GluN2D-containing receptors over GluN2A andGluN2B (Feng et al, 2004, 2005;Morley et al, 2005;Costa et al, 2009) (Table 11). Subunit selectivity for competitive antagonists may be difficult to achieve because of high homology among GluN2 subunit LBDs.…”

GluN2D Subunit-Containing NMDA Receptors Control Tissue Plasminogen Activator-Mediated Spatial Memory

“…Neurons were washed, and NMDA treatment (25 M for 30 s) was applied using a peristaltic pump. Neurons were then treated for 45 min with the GluN2D antagonist (2R*, 3S*)-1-(9-bromophenanthrene-3-carbonyl) piperazine-2, 3-dicarboxylic acid (UBP145; 0.2 M) (Costa et al, 2009), ␣ATD-GluN1 (0.01 mg/ml), and tPA (20 g/ml) either alone or in combination (directly applied in the bathing medium), and again, neurons were exposed to NMDA (25 M for 30 s). Fura-2 (excitation, 340 and 380 nm; emission, 510 nm) ratio images were acquired with a CCD camera (Princeton Instruments) and digitized (256 ϫ 512 pixels) using Metafluor 4.11 software (Universal Imaging Corporation).…”