Site within N-Methyl-D-aspartate receptor pore modulates channel gating

Chen, N., Li, B., Murphy, T. H., Raymond, L. A. (January 2004) Site within N-Methyl-D-aspartate receptor pore modulates channel gating. Molecular Pharmacology, 65 (1). pp. 157-64. ISSN 0026-895X (Print)0026-895x

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URL: http://www.ncbi.nlm.nih.gov/pubmed/14722247
DOI: 10.1124/mol.65.1.157

Abstract

N-methyl-d-aspartate-type glutamate receptors (NMDARs) are ligand-gated ion channels activated by coagonists glutamate and glycine. NMDARs play a critical role in synaptic plasticity and excitotoxicity, largely because of their high calcium permeability and slow deactivation and desensitization kinetics. NR1 is an obligate subunit in all NMDAR complexes, where it combines with NR2A, 2B, 2C, and/or 2D. NR1 binds glycine, and residue Asn598 in the re-entrant membrane loop M2 largely determines NMDAR calcium permeability. In contrast, NR2 subunits bind glutamate and contain regions that regulate receptor desensitization and deactivation. Here, we report that mutations of NR1(Asn598) in combination with wild-type NR2A, expressed in human embryonic kidney 293 cells, exhibit altered glycine-independent desensitization. In the absence of extracellular calcium, substitution of Arg for Asn598 (NR1R) slowed desensitization by 2- to 3-fold compared with wild-type NR1/NR2A, and glutamate-evoked peak current EC50 and deactivation rate were also affected. Replacement of Asn by Gln (NR1Q) produced two distinct rates of calcium- and glycine-independent desensitization. Moreover, in the presence of extracellular calcium, the voltage-dependent pore block by calcium for the NR1Q mutant mimicked the effects of the positively charged Arg at this site in NR1R on slowing desensitization and deactivation. A kinetic model of the NMDA receptor-channel suggests that these results can be explained by altered gating and not ligand binding. Our data increase understanding of the role that amino acids within the NMDAR pore play in channel gating.

Item Type: Paper
Uncontrolled Keywords: Asparagine/genetics Calcium/metabolism Cells, Cultured Glutamic Acid/*metabolism Humans Ion Channels/genetics/*physiology Mutagenesis, Site-Directed Mutation Protein Structure, Secondary Receptors, N-Methyl-D-Aspartate/chemistry/genetics/*metabolism Transfection Tyrosine/genetics
Subjects: bioinformatics > genomics and proteomics > genetics & nucleic acid processing > protein structure, function, modification > protein types > NMDA receptor
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > protein structure, function, modification > protein types > ion channel
CSHL Authors:
Communities: CSHL labs > Li lab
Depositing User: Matt Covey
Date: January 2004
Date Deposited: 12 Dec 2014 15:55
Last Modified: 12 Dec 2014 15:55
Related URLs:
URI: http://repository.cshl.edu/id/eprint/30968

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