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PSD‐95 regulates NMDA receptors in developing cerebellar granule neurons of the rat
Author(s) -
Losi Gabriele,
Prybylowski Kate,
Fu Zhanyan,
Luo Jianhong,
Wenthold Robert J.,
Vicini Stefano
Publication year - 2003
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2003.00021.x
Subject(s) - ampa receptor , nmda receptor , excitatory postsynaptic potential , microbiology and biotechnology , glutamate receptor , protein subunit , biology , synapse , synaptogenesis , postsynaptic density , chemistry , neuroscience , biophysics , receptor , biochemistry , gene
We transfected a green fluorescent protein‐tagged PSD‐95 (PSD‐95gfp) into cultured rat cerebellar granule cells (CGCs) to investigate the role of PSD‐95 in excitatory synapse maturation. Cells were grown in low potassium to favour functional synapse formation in vitro . Transfected cells displayed clear clusters of PSD‐95gfp, often at the extremities of the short dendritic trees. We recorded NMDA and AMPA miniature excitatory postsynaptic currents (NMDA‐ and AMPA‐mESPCs) in the presence of TTX and bicuculline. At days in vitro ( DIV) 7–8 PSD‐95gfp‐transfected cells had NMDA‐mEPSCs with faster decay and smaller amplitudes than matching controls. In contrast, AMPA‐mEPSC frequencies and amplitudes were increased. Whole‐cell current density and ifenprodil sensitivity were reduced in PSD‐95gfp cells, indicating a reduction of NR2B subunits containing NMDA receptors. No changes were observed compared to control when cells were transfected with cDNA for PSD‐95gfp with palmitoylation site mutations that prevent targeting to the synapse. Overexpression of the NMDA receptor NR2A subunit, but not the NR2B subunit, prevented NMDA‐mEPSC amplitude reduction when cotransfected with PSD‐95gfp. PSD‐95gfp overexpression produced faster NMDA‐mEPSC decay when transfected alone or with either NR2 subunit. Surface staining of the epitope‐tagged NR2 subunits revealed that colocalization with PSD‐95gfp was higher for flag‐tagged NR2A subunit clusters than for flag‐tagged NR2B subunit clusters. These data suggest that PSD‐95 overexpression in CGCs favours synaptic maturation by allowing synaptic insertion of NR2A and depressing expression of NR2B subunits.