A developmental change in NMDA receptor-associated proteins at hippocampal synapses.
The membrane-associated guanylate kinases [Chapsyn-110/postsynaptic density-93 (PSD-93), synapse-associated protein-90 (SAP-90)/PSD-95, and SAP-102] are believed to cluster and anchor NMDA receptors at the synapse and to play a role in signal transduction. We have investigated the developmental changes in expression of these proteins in rat hippocampus using biochemical analyses and quantitative immunogold electron microscopy. At postnatal day 2 (P2), SAP-102 was highly expressed, whereas PSD-93 and PSD-95 were low. SAP-102 expression increased during the first week, stayed stable through P35, and showed a reduced expression at 6 months. From P2 through 6 months, PSD-93 and PSD-95 increased. For PSD-95, the percent of labeled synapses increased almost threefold with age, whereas the number of gold particles per labeled synapse did not change significantly, suggesting that the increase in PSD-95 is attributable primarily to an increase in the number of synapses containing PSD-95. In contrast, for SAP-102, both percent labeled synapses and the number of gold particles per labeled synapse decreased during this time. From Western blots of hippocampus and immunogold analysis of CA1 synapses, the high expression of NR2B at P2 coincides with the high level of SAP-102 at synapses, whereas the later expression of NR2A coincides with that of PSD-93 and PSD-95. To determine whether the changes in PSD-93/95 and SAP-102 reflect preferred associations with NR2A and NR2B, respectively, we measured co-immunoprecipitation in the adult hippocampus. These studies suggest that there is a preference for complexes of NR2A/PSD-93/95 and NR2B/SAP-102. These results indicate that individual receptor-associated proteins may have specific functions that are critical to synapse development.
Sans
N
N
Laboratory of Neurochemistry, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892, USA. sansn@nidcd.nih.gov
Petralia
R S
RS
Wang
Y X
YX
Blahos
J
J
Hell
J W
JW
Wenthold
R J
RJ
D000375:Aging / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D000076122:Disks Large Homolog 4 Protein; D051528:Guanylate Kinases; D006624:Hippocampus / Q000254:growth & development / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009479:Neuropeptides / Q000378:metabolism; D009687:Nuclear Proteins; D009703:Nucleoside-Phosphate Kinase / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism*; D014157:Transcription Factors
C116869:DLG3 protein, human; D000076122:Disks Large Homolog 4 Protein; C101195:Dlg3 protein, rat; C501449:Dlg4 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C501451:Mpp2 protein, rat; D009419:Nerve Tissue Proteins; D009479:Neuropeptides; D009687:Nuclear Proteins; D020033:Protein Isoforms; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D014157:Transcription Factors; C033652:postsynaptic density proteins; D009703:Nucleoside-Phosphate Kinase; D051528:Guanylate Kinases