Neonatal hypoxia-ischemia differentially upregulates MAGUKs and associated proteins in PSD-93-deficient mouse brain.
OBJECTIVE
Postsynaptic density (PSD)-93 and PSD-95 are the major membrane-associated guanylate kinases (MAGUKs) at excitatory synapses of the brain linking the N-methyl-d-aspartate receptor (NMDAR) with neuronal nitric oxide synthase (nNOS), which contributes to cell death after neonatal hypoxia-ischemia (HI). We investigated whether deletion of PSD-93 would dissociate the NMDAR from nNOS and be neuroprotective.


METHODS
Postnatal day 7 wild-type (+/+), heterozygous (+/-), and homozygous (-/-) PSD-93 knockout mice were subjected to HI by permanent ligation of the right carotid artery, followed by exposure to 8% O2/92% N2 for 1 hour. Brains were scored 5 days later for damage with cresyl violet and iron stains. Western blot and coimmunoprecipitation were used to determine the expression and association of the major PSD proteins.


RESULTS
There was no significant difference between PSD-93 (-/-) and (+/+) mice in mortality or degree of brain injury. In the absence of PSD-93, PSD-95 still interacted with NR2B and nNOS. Under physiological conditions, PSD-95, nNOS, NR2A, and NR2B were unaltered in the (-/-) pups. However, at 24 hours after HI, protein expression of PSD-95, nNOS, and NR2A but not NR2B was markedly higher in the (-/-) than in the (+/+) pups. In (+/+) pups, HI resulted in decreased expression of NR2A but not NR2B in cortex and decreased NR2A and NR2B expression in hippocampus, but this reduction was not observed in (-/-) pups.


CONCLUSIONS
PSD-93 is not essential for baseline synaptic function but may participate in regulation of NMDAR-associated signaling pathways after HI injury. Deletion of PSD-93 alone does not provide neuroprotection after neonatal HI, possibly a result, in part, of upregulation of PSD-95. MAGUKs may substitute for one another, allowing normal NMDAR function in the postnatal period.
Jiang
Xiangning
X
Department of Neurology, University of California, San Francisco 94143-0663, USA.
Mu
Dezhi
D
Sheldon
R Ann
RA
Glidden
David V
DV
Ferriero
Donna M
DM
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism* / Q000473:pathology; D000074288:Discs Large Homolog 1 Protein; D000076122:Disks Large Homolog 4 Protein; D051528:Guanylate Kinases; D006579:Heterozygote; D006720:Homozygote; D020925:Hypoxia-Ischemia, Brain / Q000378:metabolism* / Q000473:pathology; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000172:deficiency* / Q000378:metabolism; D009479:Neuropeptides / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I; D009703:Nucleoside-Phosphate Kinase / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D012720:Severity of Illness Index; D015996:Survival Rate; D015854:Up-Regulation
D048868:Adaptor Proteins, Signal Transducing; D000074288:Discs Large Homolog 1 Protein; D000076122:Disks Large Homolog 4 Protein; C000614189:Dlg1 protein, mouse; C501447:Dlg4 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C120997:NR2A NMDA receptor; C121001:NR2B NMDA receptor; D009419:Nerve Tissue Proteins; D009479:Neuropeptides; D016194:Receptors, N-Methyl-D-Aspartate; C033652:postsynaptic density proteins; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496321:Nos1 protein, mouse; D009703:Nucleoside-Phosphate Kinase; C501445:Dlg2 protein, mouse; C491075:Dlgh3 protein, mouse; D051528:Guanylate Kinases