title: Cycling of NMDA receptors during trafficking in neurons before synapse formation.
abstract: The trafficking of glutamate receptors in neurons is of the utmost importance for synapse formation and synaptic plasticity. Recently, we demonstrated that both NMDA and AMPA receptors reside in mobile transport packets that are recruited rapidly and independently to nascent synapses. Here, we show that a large proportion of the glutamate receptor clusters in young cortical neurons are present on the surface of dendrites before synapses are formed and these surface-exposed transport packets are mobile. Exocytosis of glutamate receptors to the dendritic surface occurs via a SNARE [soluble n-ethylmaleimide-sensitive factor attachment protein (SNAP) receptor]-dependent SNAP-23-mediated mechanism. Endocytosis occurs rapidly after surface exposure; >50% of surface-labeled NMDA receptors (NMDARs) are endocytosed within 5 min. NMDARs are transported along microtubules on large tubulovesicular organelles, as indicated by immunoelectron microscopy, and are associated with EEA1 (early endosomal antigen 1) and SAP102 (synapse-associated protein 102), as indicated by immunocytochemistry. Most surprisingly, a large proportion of these transport packets cycle through the dendritic plasma membrane before synapse formation. These results suggest a novel model in which NMDARs cycle with the plasma membrane during pauses of movement along microtubules while trafficking.
authors.affiliation: Center for Neuroscience, University of California Davis, Davis, California 95616, USA.
authors.forename: Philip
authors.initials: P
authors.lastname: Washbourne
authors.forename: Xiao-Bo
authors.initials: XB
authors.lastname: Liu
authors.forename: Edward G
authors.initials: EG
authors.lastname: Jones
authors.forename: A Kimberley
authors.initials: AK
authors.lastname: McAllister
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003712:Dendrites / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology; D005089:Exocytosis / Q000502:physiology; D049452:Green Fluorescent Proteins; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D016253:Microscopy, Immunoelectron; D008870:Microtubules / Q000378:metabolism / Q000648:ultrastructure; D008959:Models, Neurological; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D051381:Rats; D017470:Receptors, Glutamate / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D050600:SNARE Proteins; D013569:Synapses / Q000378:metabolism*; D014162:Transfection; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C101195:Dlg3 protein, rat; D008565:Membrane Proteins; C409466:NR1 NMDA receptor; D009479:Neuropeptides; D017470:Receptors, Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D011993:Recombinant Fusion Proteins; D050600:SNARE Proteins; C498858:Snap23 protein, rat; D033921:Vesicular Transport Proteins; C093846:early endosome antigen 1; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins