Positive Modulatory Interactions of NMDA Receptor GluN1/2B Ligand Binding Domains Attenuate Antagonists Activity

Abstract

N-methyl D-aspartate receptors (NMDAR) play crucial role in normal brain function and pathogenesis of neurodegenerative and psychiatric disorders. Functional tetra-heteromeric NMDAR contains two obligatory GluN1 subunits and two identical or different non-GluN1 subunits that include six different gene products; four GluN2 (A–D) and two GluN3 (A–B) subunits. The heterogeneity of subunit combination facilities the distinct function of NMDARs. All GluN subunits contain an extracellular N-terminal Domain (NTD) and ligand binding domain (LBD), transmembrane domain (TMD) and an intracellular C-terminal domain (CTD). Interaction between the GluN1 and co-assembling GluN2/3 subunits through the LBD has been proven crucial for defining receptor deactivation mechanisms that are unique for each combination of NMDAR. Modulating the LBD interactions has great therapeutic potential. In the present work, by amino acid point mutations and electrophysiology techniques, we have studied the role of LBD interactions in determining the effect of well-characterized pharmacological agents including agonists, competitive antagonists, and allosteric modulators. The results reveal that agonists (glycine and glutamate) potency was altered based on mutant amino acid sidechain chemistry and/or mutation site. Most antagonists inhibited mutant receptors with higher potency; interestingly, clinically used NMDAR channel blocker memantine was about three-fold more potent on mutated receptors (N521A, N521D, and K531A) than wild type receptors. These results provide novel insights on the clinical pharmacology of memantine, which is used for the treatment of mild to moderate Alzheimer's disease. In addition, these findings demonstrate the central role of LBD interactions that can be exploited to develop novel NMDAR based therapeutics.

A glutamate concentration‐biased allosteric modulator potentiates NMDA‐induced ion influx in neurons

“…In this study, through ongoing computational and experimental screening efforts, 31 , 32 , 33 , 34 , 35 we have identified a compound from the NIH PubChem database (CID# 3794169) that contains 111 million unique chemical structures. Previously known biological effects of this compound can be obtained from PubChem .…”

Three-dimensional missense tolerance ratio analysis

“…Previously published NMDAR wild-type and point mutation construct glutamate EC 50 values were obtained from the literature (Laube et al 1993;Kuryatov et al 1994;Wafford et al 1995;Williams et al 1995Williams et al , 1998Hirai et al 1996;Kashiwagi et al 1996Kashiwagi et al , 1997Anson et al 1998;Fayyazuddin et al 2000;Low et al 2000;Wittekindt et al 2001;Laube et al 2004;Chen et al 2005Chen et al , 2017Furukawa et al 2005;Inanobe et al 2005;Erreger et al 2007;Maier et al 2007;Ren et al 2013;Yuan et al 2014;Serraz et al 2016;Swanger et al 2016;Addis et al 2017;Bledsoe et al 2017;Ogden et al 2017;Wang et al 2017;Li et al 2019;Hrcka Krausova et al 2020;McDaniel et al 2020;Skrenkova et al 2020). The residue numbers were modified so that the initiating methionine was always one.…”