title: Glutamate receptor composition of the post-synaptic density is altered in genetic mouse models of NMDA receptor hypo- and hyperfunction.
abstract: The N-methyl-d-aspartate receptor (NMDAR) and α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptor (AMPAR) are ionotropic glutamate receptors responsible for excitatory neurotransmission in the brain. These excitatory synapses are found on dendritic spines, with the abundance of receptors concentrated at the postsynaptic density (PSD). We utilized two genetic mouse models, the serine racemase knockout (SR-/-) and the glycine transporter subtype 1 heterozygote mutant (GlyT1+/-), to determine how constitutive NMDAR hypo- and hyperfunction, respectively, affect the glutamate receptor composition of the PSD in the hippocampus and prefrontal cortex (PFC). Using cellular fractionation, we found that SR-/- mice had elevated protein levels of NR1 and NR2A NMDAR subunits specifically in the PSD-enriched fraction from the hippocampus, but not from the PFC. There were no changes in the amounts of AMPAR subunits (GluR1, GluR2), or PSD protein of 95 kDa (PSD95) in either brain region. GlyT1+/- mice also had elevated protein expression of NR1 and NR2A subunits in the PSD, as well as an increase in total protein. Moreover, GlyT1+/- mice had elevated amounts of GluR1 and GluR2 in the PSD, and higher total amounts of GluR1. Similar to SR-/- mice, there were no protein changes observed in the PFC. These findings illustrate the complexity of synaptic adaptation to altered NMDAR function.
authors: Department of Psychiatry, Harvard Medical School, Belmont, MA, USA.
authors: Darrick T
authors: DT
authors: Balu
authors: Joseph T
authors: JT
authors: Coyle
mesh_terms: D000818:Animals; D002458:Cell Fractionation / Q000379:methods; D000076122:Disks Large Homolog 4 Protein; D005786:Gene Expression Regulation / Q000235:genetics; D050487:Glycine Plasma Membrane Transport Proteins / Q000172:deficiency; D051528:Guanylate Kinases; D006624:Hippocampus / Q000378:metabolism / Q000648:ultrastructure*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D057907:Post-Synaptic Density / Q000235:genetics* / Q000378:metabolism*; D017397:Prefrontal Cortex / Q000378:metabolism / Q000648:ultrastructure*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D019998:Racemases and Epimerases / Q000172:deficiency; D018091:Receptors, AMPA / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D000099300:Serine Racemase
chemical_list: D000076122:Disks Large Homolog 4 Protein; D050487:Glycine Plasma Membrane Transport Proteins; D051528:Guanylate Kinases; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D021122:Protein Subunits; D019998:Racemases and Epimerases; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D000099300:Serine Racemase; C501447:Dlg4 protein, mouse; C493267:Slc6a9 protein, mouse