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  • Interaction of postsynaptic density protein-95 with NMDA receptors influences excitotoxicity in the yeast artificial chromosome mouse model of Huntington's disease.

Interaction of postsynaptic density protein-95 with NMDA receptors influences excitotoxicity in the yeast artificial chromosome mouse model of Huntington's disease.

The Journal of neuroscience : the official journal of the Society for Neuroscience (2009-09-04)
Jing Fan, Catherine M Cowan, Lily Y J Zhang, Michael R Hayden, Lynn A Raymond
ABSTRACT

Evidence suggests that NMDA-type glutamate receptors contribute to degeneration of striatal medium-sized spiny neurons (MSNs) in Huntington's disease (HD). Previously, we demonstrated that NMDA receptor (NMDAR)-mediated current and/or toxicity is increased in MSNs from the yeast artificial chromosome (YAC) transgenic mouse model expressing polyglutamine (polyQ)-expanded (mutant) full-length human huntingtin (htt). Others have shown that membrane-associated guanylate kinases (MAGUKs), such as PSD-95 and SAP102, modulate NMDAR surface expression and excitotoxicity in hippocampal and cortical neurons and that htt interacts with PSD-95. Here, we tested the hypothesis that an altered association between MAGUKs and NMDARs in mutant huntingtin-expressing cells contributes to increased susceptibility to excitotoxicity. We show that htt coimmunoprecipitated with SAP102 in HEK293T cells and striatal tissue from wild-type and YAC transgenic mice; however, the association of SAP102 with htt or the NMDAR NR2B subunit was unaffected by htt polyQ length, whereas association of PSD-95 with NR2B in striatal tissue was enhanced by increased htt polyQ length. Treatment of cultured MSNs with Tat-NR2B9c peptide blocked binding of NR2B with SAP102 and PSD-95 and reduced NMDAR surface expression by 20% in both YAC transgenic and wild-type MSNs, and also restored susceptibility to NMDAR excitoxicity in YAC HD MSNs to levels observed in wild-type MSNs; a similar effect on excitotoxicity was observed after knockdown of PSD-95 by small interfering RNA. Unlike previous findings in cortical and hippocampal neurons, rescue of NMDA toxicity by Tat-NR2B9c occurred independently of any effect on neuronal nitric oxide synthase activity. Our results elucidate further the mechanisms underlying enhanced excitotoxicity in HD.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Anti-Huntingtin Protein Antibody, a.a. 181-810, clone 1HU-4C8, ascites fluid, clone 1HU-4C8, Chemicon®
Sigma-Aldrich
Anti-Myc Tag Antibody, clone 4A6, clone 4A6, Upstate®, from mouse
Sigma-Aldrich
Anti-NMDAR1 Antibody, clone 54.1, clone 54.1, Chemicon®, from mouse
Sigma-Aldrich
Anti-NR2B Antibody, Upstate®, from rabbit
Sigma-Aldrich
Anti-NR2A Antibody, Upstate®, from rabbit