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Hippocampal N-methyl-D-aspartate receptors (NMDARs) contribute to the expression of certain types of synaptic plasticity, such as long-term potentiation (LTP). It is well documented that tyrosine kinases increase NMDAR phosphorylation and potentiate NMDAR function. However, it is unclear how these phosphorylation changes result in enhanced NMDAR activity. We previously reported that NMDAR surface expression can be increased by LTP-inducing stimulation via tyrosine kinase-dependent mechanisms in the adult hippocampus [D.R. Grosshans, D.A. Clayton, S.J. Coultrap, M.D. Browning, Nat. Neurosci., 5 (2002) 27-33]. We therefore hypothesized that tyrosine phosphorylation of the NMDAR may enhance the trafficking of the receptor to the synaptic membrane. Here, we show that the stoichiometry of NR2A and NR2B tyrosine phosphorylation is significantly higher in synaptosomal membranes than intracellular microsomal/light membranes. Interestingly, NR2B tyrosine-1472, but not NR1 serine-896 or -897, phosphorylation is significantly higher in synaptosomal membranes than intracellular microsomal/light membranes. Furthermore, treatment of hippocampal slices with either a tyrosine phosphatase inhibitor or a tyrosine kinase inhibitor alters NMDAR tyrosine phosphorylation and produces a corresponding change in the concentration of NMDARs in the synaptosomal membrane fraction. Taken together, these data support the hypothesis that tyrosine phosphorylation may enhance NMDAR activity by increasing the number of NMDARs at the synaptic membrane.

Original publication

DOI

10.1016/j.molbrainres.2005.09.012

Type

Journal article

Journal

Brain Res Mol Brain Res

Publication Date

07/12/2005

Volume

142

Pages

65 - 79

Keywords

Animals, Blotting, Western, Calnexin, Disks Large Homolog 4 Protein, Enzyme Inhibitors, Hippocampus, Immunoprecipitation, In Vitro Techniques, Intracellular Signaling Peptides and Proteins, Male, Membrane Proteins, Organometallic Compounds, Phenanthrolines, Phenols, Phosphorylation, Protein Transport, Protein Tyrosine Phosphatases, Rats, Rats, Sprague-Dawley, Receptors, N-Methyl-D-Aspartate, Subcellular Fractions, Synaptic Membranes, Tyrosine