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The Journal of Neuroscience, April 4, 2007, 27(14):3768-3779; doi:10.1523/JNEUROSCI.4356-06.2007

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Cellular/Molecular
Altered NMDA Receptor Trafficking in a Yeast Artificial Chromosome Transgenic Mouse Model of Huntington's Disease

Mannie M. Y. Fan,^1 * Herman B. Fernandes,^1 * Lily Y. J. Zhang,² Michael R. Hayden,^3,4,5,6 and Lynn A. Raymond^2,6,7,8

¹Graduate Program in Neuroscience, ²Department of Psychiatry, ³Centre for Molecular Medicine and Therapeutics, ⁴Department of Medical Genetics, ⁵Child and Family Research Institute, ⁶Brain Research Centre, ⁷Department of Medicine, and ⁸Kinsmen Laboratories of Neurological Research, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3

Correspondence should be addressed to Dr. Lynn A. Raymond, Department of Psychiatry, University of British Columbia, Room 4834-2255 Wesbrook Mall, Vancouver, British Columbia, Canada V6T 1Z3. Email: lynnr{at}interchange.ubc.ca

Overactivation of NMDA receptors (NMDARs) is believed to play a role in degeneration of striatal medium-sized spiny neurons (MSNs) in Huntington's disease (HD). This hereditary disorder is caused by an expansion >35 in the polyglutamine (polyQ) region of the protein huntingtin (htt). Previous work has shown that NMDAR current, calcium signaling, and/or toxicity are enhanced in striatal MSNs in a variety of transgenic mice and cellular models of HD, but whether the enhancement is specific for MSNs or correlated with mutant htt (mhtt) polyQ length is not known. Furthermore, the mechanism underlying the increase in NMDAR activity has not been elucidated. Here we report polyQ length-dependent enhancement of peak NMDAR current density by mhtt in cultured MSNs, but not cortical neurons, from the yeast artificial chromosome (YAC) transgenic HD mouse model. We also observed a shift of NMDAR subunits NR1 and NR2B from internal pools to the plasma membrane and a significantly faster rate of NMDAR insertion to the surface in YAC72 MSNs. In comparing YAC72 with wild-type striatal tissue, subcellular fractionation revealed a relative enrichment of NR1 C2'-containing NMDARs in the vesicle/microsome-enriched fraction, and coimmunoprecipitation experiments demonstrated an increased proportion of NR1 C2' isoforms associated with NR2 subunits, which may contribute to faster forward trafficking of these receptors. Our results suggest that altered NMDAR trafficking may underlie potentiation of NMDAR-mediated current and toxicity in the YAC72 HD mouse model. This polyQ length-dependent, neuronal-specific change in NMDAR activity induced by mhtt may contribute to selective neuronal degeneration in HD.

Key words: Huntington's disease; huntingtin; polyglutamine; NMDA receptor; trafficking; transgenic

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Received Oct. 5, 2006; revised Feb. 15, 2007; accepted Feb. 27, 2007.

Correspondence should be addressed to Dr. Lynn A. Raymond, Department of Psychiatry, University of British Columbia, Room 4834-2255 Wesbrook Mall, Vancouver, British Columbia, Canada V6T 1Z3. Email: lynnr{at}interchange.ubc.ca

This article has been cited by other articles:

				J. Wang, C.-E. Wang, A. Orr, S. Tydlacka, S.-H. Li, and X.-J. Li Impaired ubiquitin-proteasome system activity in the synapses of Huntington's disease mice J. Cell Biol., March 24, 2008; 180(6): 1177 - 1189. [Abstract] [Full Text] [PDF]

				A. J. Milnerwood and L. A. Raymond Corticostriatal synaptic function in mouse models of Huntington's disease: early effects of huntingtin repeat length and protein load J. Physiol., December 15, 2007; 585(3): 817 - 831. [Abstract] [Full Text] [PDF]

				H. B. Fernandes, K. G. Baimbridge, J. Church, M. R. Hayden, and L. A. Raymond Mitochondrial Sensitivity and Altered Calcium Handling Underlie Enhanced NMDA-Induced Apoptosis in YAC128 Model of Huntington's Disease J. Neurosci., December 12, 2007; 27(50): 13614 - 13623. [Abstract] [Full Text] [PDF]

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