Our long-term goal is to address molecular determinants of brain disorders. Fast synaptic transmission in the brain is mediated by ion channels that are directly activated by a chemical neurotransmitter. NMDA and AMPA receptors are glutamate-gated ion channels that convert the presynaptic release of glutamate, the predominant excitatory neurotransmitter in the brain, into a postsynaptic signal. By defining the operation of NMDA and AMPA receptors, we will gain a better understanding of how they control brain function. We will also learn how to modulate their function with greater precision and specificity to help understand, and potentially treat, brain disroders such as schizophrenia, epilepsy, and the excitotoxicity associated with acute and chronic brain disorders. Our experiments will focus on a eukaryotic transmembrane segment, the M4 segment, which is positioned around the pore domain. Recent published and preliminary data from our lab has indicated that the M4 segments act in novel ways to regulate core synaptic functions of NMDA and AMPA receptors. Highlighting their significance is that inherited and de novo mutations in the M4 segments induce neurodevelopmental disorders and epileptic encephalopathies.
Aim 1 will address the novel hypothesis that the unique kinetics of NMDA receptors at synapses are due to two kinetically distinct gates and that the M4 segments regulate these gates in a subunit-specific manner. We will address this hypothesis using cysteine cross-linking, rigorous single channel analysis, and molecular dynamic simulations.
Aim 2 will address the hypothesis that the M4 segments in NMDA receptors are a major allosteric conduit coupling external domains to transmembrane and internal domains. Here, we will test this hypothesis by decoupling external domains from transmembrane and internal domains and assay this decoupling using electrophysiological and FRET based measurements.
Aim 3 will address the hypothesis that the M4 segments in AMPA receptors carry out distinct functional roles including acting as a conduit for auxiliary proteins found at synapses. Here, we will compare functional properties between the M4 segments in NMDA and AMPA receptors using electrophysiological recordings and molecular dynamic simulations. Our experiments will delineate molecular features of NMDA and AMPA receptors that contribute to synaptic function. This information will aid in developing specific therapies to target these receptors in nervous system disorders.

Public Health Relevance

Neurodevelopmental disorders such as autism and epilepsy and the cell death associated with acute (stroke) and chronic (Alzheimer?s Disease) brain disorders have a devasting impact on human lives and society. Our experiments will address the operation of NMDA and AMPA receptors, glutamate-gated ion channels found throughout the nervous system. The outcome of our experiments will aid in defining how these receptors contribute to devasting brain disorders and how to selectively target them in the clinic.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS088479-06
Application #
9927688
Study Section
Biophysics of Neural Systems Study Section (BPNS)
Program Officer
Silberberg, Shai D
Project Start
2015-04-01
Project End
2024-03-31
Budget Start
2020-04-01
Budget End
2021-03-31
Support Year
6
Fiscal Year
2020
Total Cost
Indirect Cost
Name
State University New York Stony Brook
Department
Neurosciences
Type
Schools of Medicine
DUNS #
804878247
City
Stony Brook
State
NY
Country
United States
Zip Code
11794
Hansen, Kasper B; Yi, Feng; Perszyk, Riley E et al. (2018) Structure, function, and allosteric modulation of NMDA receptors. J Gen Physiol 150:1081-1105
Amin, Johansen B; Leng, Xiaoling; Gochman, Aaron et al. (2018) A conserved glycine harboring disease-associated mutations permits NMDA receptor slow deactivation and high Ca2+ permeability. Nat Commun 9:3748
Wollmuth, Lonnie P (2018) Ion permeation in ionotropic glutamate receptors: Still dynamic after all these years. Curr Opin Physiol 2:36-41
Amin, Johansen B; Salussolia, Catherine L; Chan, Kelvin et al. (2017) Divergent roles of a peripheral transmembrane segment in AMPA and NMDA receptors. J Gen Physiol 149:661-680
Zhou, Huan-Xiang; Wollmuth, Lonnie P (2017) Advancing NMDA Receptor Physiology by Integrating Multiple Approaches. Trends Neurosci 40:129-137
Alsaloum, Matthew; Kazi, Rashek; Gan, Quan et al. (2016) A Molecular Determinant of Subtype-Specific Desensitization in Ionotropic Glutamate Receptors. J Neurosci 36:2617-22
Gan, Quan; Dai, Jian; Zhou, Huan-Xiang et al. (2016) The Transmembrane Domain Mediates Tetramerization of ?-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptors. J Biol Chem 291:6595-606
Dai, Jian; Wollmuth, Lonnie P; Zhou, Huan-Xiang (2015) Mechanism-Based Mathematical Model for Gating of Ionotropic Glutamate Receptors. J Phys Chem B 119:10934-40