The Journal of Neuroscience, March 26, 2008, 28(13):3500-3509; doi:10.1523/JNEUROSCI.5239-07.2008
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Cellular/Molecular
Masking of the Endoplasmic Reticulum Retention Signals during Assembly of the NMDA Receptor
Martin Horak,
Kai Chang, and
Robert J. Wenthold
Laboratory of Neurochemistry, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892
Correspondence should be addressed to Martin Horak, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, 50 South Drive, Room 4146, Bethesda, Maryland 20892. Email: horakm{at}nidcd.nih.gov
NMDA receptors are glutamate-gated ion channels that play important roles in synaptic transmission and excitotoxicity. The functional NMDA receptor is thought to be a heterotetramer composed mainly of two NR1 and two NR2 subunits. Although it is generally accepted that only correctly assembled NMDA receptors can pass the ER quality control, the mechanism underlying this process is not well understood. Using truncated and chimeric NMDA receptor subunits expressed in heterologous cells and cortical neurons, we found that the third membrane domains (M3) of both NR1 and NR2B contain signals that cause the unassembled subunits to be retained in the ER. M3 of both NR1 and NR2B and, M4 of NR1, are necessary for masking ER retention signals found in M3. Thus, our data reveal a critical role of the membrane domains in the assembly of functional NMDA receptors.
Key words: glutamate receptors; ion channel assembly; subunit interaction; ER retention; masking; intracellular trafficking
Received Nov. 26, 2007;
revised Feb. 19, 2008;
accepted Feb. 21, 2008.
Correspondence should be addressed to Martin Horak, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, 50 South Drive, Room 4146, Bethesda, Maryland 20892. Email: horakm{at}nidcd.nih.gov