title: Two N-glycosylation Sites in the GluN1 Subunit Are Essential for Releasing N-methyl-d-aspartate (NMDA) Receptors from the Endoplasmic Reticulum.
abstract: NMDA receptors (NMDARs) comprise a subclass of neurotransmitter receptors whose surface expression is regulated at multiple levels, including processing in the endoplasmic reticulum (ER), intracellular trafficking via the Golgi apparatus, internalization, recycling, and degradation. With respect to early processing, NMDARs are regulated by the availability of GluN subunits within the ER, the presence of ER retention and export signals, and posttranslational modifications, including phosphorylation and palmitoylation. However, the role of N-glycosylation, one of the most common posttranslational modifications, in regulating NMDAR processing has not been studied in detail. Using biochemistry, confocal and electron microscopy, and electrophysiology in conjunction with a lentivirus-based molecular replacement strategy, we found that NMDARs are released from the ER only when two asparagine residues in the GluN1 subunit (Asn-203 and Asn-368) are N-glycosylated. Although the GluN2A and GluN2B subunits are also N-glycosylated, their N-glycosylation sites do not appear to be essential for surface delivery of NMDARs. Furthermore, we found that removing N-glycans from native NMDARs altered the receptor affinity for glutamate. Our results suggest a novel mechanism by which neurons ensure that postsynaptic membranes contain sufficient numbers of functional NMDARs.
authors.affiliation: From the Institute of Physiology, Academy of Sciences of the Czech Republic v.v.i., Videnska 1083, 14220 Prague 4, Czech Republic, the Department of Physiology, Faculty of Science, Charles University in Prague, Albertov 6, 12843 Prague 2, Czech Republic.
authors.forename: Katarina
authors.initials: K
authors.lastname: Lichnerova
authors.affiliation: From the Institute of Physiology, Academy of Sciences of the Czech Republic v.v.i., Videnska 1083, 14220 Prague 4, Czech Republic.
authors.forename: Martina
authors.initials: M
authors.lastname: Kaniakova
authors.affiliation: the Department of Biomedical Sciences, Neuroscience Research Institute, Seoul National University College of Medicine, Seoul 110-799, South Korea, and.
authors.forename: Seung Pyo
authors.initials: SP
authors.lastname: Park
authors.affiliation: From the Institute of Physiology, Academy of Sciences of the Czech Republic v.v.i., Videnska 1083, 14220 Prague 4, Czech Republic.
authors.forename: Kristyna
authors.initials: K
authors.lastname: Skrenkova
authors.affiliation: the Advanced Imaging Core, NIDCD/National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Ya-Xian
authors.initials: YX
authors.lastname: Wang
authors.affiliation: the Advanced Imaging Core, NIDCD/National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Ronald S
authors.initials: RS
authors.lastname: Petralia
authors.affiliation: the Department of Biomedical Sciences, Neuroscience Research Institute, Seoul National University College of Medicine, Seoul 110-799, South Korea, and suhyho@snu.ac.kr.
authors.forename: Young Ho
authors.initials: YH
authors.lastname: Suh
authors.affiliation: From the Institute of Physiology, Academy of Sciences of the Czech Republic v.v.i., Videnska 1083, 14220 Prague 4, Czech Republic, mhorak@biomed.cas.cz.
authors.forename: Martin
authors.initials: M
authors.lastname: Horak
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D016202:N-Methylaspartate / Q000737:chemistry / Q000378:metabolism*; D009474:Neurons / Q000737:chemistry / Q000378:metabolism*; D011134:Polysaccharides / Q000378:metabolism; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000737:chemistry / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism; D009435:Synaptic Transmission
chemical_list: D011134:Polysaccharides; D016194:Receptors, N-Methyl-D-Aspartate; D016202:N-Methylaspartate
keywords: endoplasmic reticulum (ER); glutamate receptor; glycosylation; neuron; synapse; trafficking