title: Neuronal enriched endosomal protein of 21 kDa colocalizes with glutamate receptor subunit GLUR2/3 at the postsynaptic membrane.
abstract: Functional evidence suggests that neuronal enriched endosomal protein of 21 kDa (NEEP21) takes part in facilitating transport of AMPA receptors (AMPAR) in the synapse. To explore the anatomical basis for a role in this synaptic trafficking, we investigated the ultrastructural localization of NEEP21 in rodent brain. Using immunogold electron microscopy, we show that NEEP21 is colocalized with the AMPAR subunits GluR2/3 in postsynaptic spines. Quantitative analysis of gold particle distribution along an axis perpendicular to the postsynaptic specialization indicated that NEEP21 occurs in the postsynaptic membrane but also in the interior of the spines. NEEP21 positive endosomes/multivesicular bodies were found throughout cell bodies and dendrites. In light microscopical preparations, the NEEP21 antibody produced a labeling pattern in the neocortex, hippocampus and cerebellum that mimicked that of GluR2/3 and not that of GluR1 or 4. Our findings are consistent with a role for NEEP21 in facilitating vesicular transport of GluR2 between intracellular compartments and the postsynaptic plasma membrane.
authors.affiliation: Institute of Basic Medical Sciences, Department of Anatomy, University of Oslo, P.O. Box 1105 Blindern, 0317 Oslo, Norway.
authors.forename: J K
authors.initials: JK
authors.lastname: Utvik
authors.forename: C
authors.initials: C
authors.lastname: Haglerød
authors.forename: M N I
authors.initials: MN
authors.lastname: Mylonakou
authors.forename: T
authors.initials: T
authors.lastname: Holen
authors.forename: M
authors.initials: M
authors.lastname: Kropf
authors.forename: H
authors.initials: H
authors.lastname: Hirling
authors.forename: O
authors.initials: O
authors.lastname: Skare
authors.forename: P
authors.initials: P
authors.lastname: Laake
authors.forename: O P
authors.initials: OP
authors.lastname: Ottersen
authors.forename: F-M S
authors.initials: FM
authors.lastname: Haug
authors.forename: S
authors.initials: S
authors.lastname: Davanger
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism / Q000648:ultrastructure; D002478:Cells, Cultured; D049229:Dendritic Spines / Q000378:metabolism* / Q000648:ultrastructure; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism / Q000648:ultrastructure; D005260:Female; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016253:Microscopy, Immunoelectron; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D018091:Receptors, AMPA / Q000378:metabolism*; D013570:Synaptic Membranes / Q000378:metabolism* / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000502:physiology
chemical_list: D009419:Nerve Tissue Proteins; C461339:Nsg1 protein, rat; D018091:Receptors, AMPA; C104723:glutamate receptor ionotropic, AMPA 3; C104722:glutamate receptor ionotropic, AMPA 2