Molecular Mechanism of Disease-Associated Mutations in the Pre-M1 Helix of NMDA Receptors and Potential Rescue Pharmacology.

• Type of Material: Article
• Authors: Kevin K. Ogden, Emory University; Wenjuan Chen, Emory University; Sharon A. Swanger, Emory University; Miranda J. McDaniel, Emory University; Linlin Z. Fan, Harvard University; Chun Hu, Emory University; Anel Tankovic, Emory University; Hirofumi Kusumoto, Emory University; Gabrielle J. Kosobucki, University of Pittsburgh; Anthony J. Schulien, University of Pittsburgh; Zhuocheng Su, Emory University; Joseph Pecha, Emory University; Subhrajit Bhattacharya, Emory University; Slavé Petrovski, The University of Melbourne; Adam E. Cohen, Harvard University; Elias Aizenman, University of Pittsburgh; Stephen Traynelis, Emory University; Hongjie Yuan, Emory University
• Language: English
• Date: 2017-01-17
• Publisher: Public Library of Science
• Publication Version: Final Published Version
• Copyright Statement: © 2017 Ogden et al
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1371/journal.pgen.1006536
• Title of Journal or Parent Work: PLoS Genetics
• ISSN: 1553-7390
• Volume: 13
• Issue: 1
• Start Page: e1006536
• End Page: e1006536
• Grant/Funding Information: LZF and AEC are supported by the Howard Hughes Medical Institute; This work was supported by the Eunice Kennedy Shriver National Institute Of Child Health & Human Development (NICHD) of the National Institutes of Health (NIH) under award number R01HD082373 to HY, by the National Institute of Neurological Disorders and Stroke (NINDS) of the NIH under award number R01NS036654 to SFT, award number R24NS092989 to SFT, and award number R01NS043277 to EA, by the Xiangya-Emory Medical Schools Visiting Student Program to WC, by Emory+Children’s Pediatric Center Seed Grant Program to HY, and by the National Center for Advancing Translational Sciences of the National Institutes of Health under Award Number UL1TR000454 to HY.; SP is supported by the National Health and Medical Research Council of Australia.
• Keywords: Transfection; Single channel recordings; Excitatory postsynaptic potentials; Complementary DNA; Neuronal dendrites; Neurons; Glycine; Glutamate

Abstract

N-methyl-D-aspartate receptors (NMDARs), ligand-gated ionotropic glutamate receptors, play key roles in normal brain development and various neurological disorders. Here we use standing variation data from the human population to assess which protein domains within NMDAR GluN1, GluN2A and GluN2B subunits show the strongest signal for being depleted of missense variants. We find that this includes the GluN2 pre-M1 helix and linker between the agonist-binding domain (ABD) and first transmembrane domain (M1). We then evaluate the functional changes of multiple missense mutations in the NMDAR pre-M1 helix found in children with epilepsy and developmental delay. We find mutant GluN1/GluN2A receptors exhibit prolonged glutamate response time course for channels containing 1 or 2 GluN2A-P552R subunits, and a slow rise time only for receptors with 2 mutant subunits, suggesting rearrangement of one GluN2A pre-M1 helix is sufficient for rapid activation. GluN2A-P552R and analogous mutations in other GluN subunits increased the agonist potency and slowed response time course, suggesting a functionally conserved role for this residue. Although there is no detectable change in surface expression or open probability for GluN2A-P552R, the prolonged response time course for receptors that contained GluN2A-P552R increased charge transfer for synaptic-like activation, which should promote excitotoxic damage. Transfection of cultured neurons with GluN2A-P552R prolonged EPSPs, and triggered pronounced dendritic swelling in addition to excitotoxicity, which were both attenuated by memantine. These data implicate the pre-M1 region in gating, provide insight into how different subunits contribute to gating, and suggest that mutations in the pre-M1 helix can compromise neuronal health. Evaluation of FDA-approved NMDAR inhibitors on the mutant NMDAR-mediated current response and neuronal damage provides a potential clinical path to treat individuals harboring similar mutations in NMDARs.