title: Phosphorylation of glutamate receptor interacting protein 1 regulates surface expression of glutamate receptors.
abstract: The number of synaptic alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)-type glutamate receptors (AMPARs) controls the strength of excitatory transmission. AMPARs cycle between internal endosomal compartments and the plasma membrane. Interactions between the AMPAR subunit GluR2, glutamate receptor interacting protein 1 (GRIP1), and the endosomal protein NEEP21 are essential for correct GluR2 recycling. Here we show that an about 85-kDa protein kinase phosphorylates GRIP1 on serine 917. This kinase is present in NEEP21 immunocomplexes and is activated in okadaic acid-treated neurons. Pulldown assays and atomic force microscopy indicate that phosphorylated GRIP shows reduced binding to NEEP21. AMPA or N-methyl-D-aspartate stimulation of hippocampal neurons induces delayed phosphorylation of the same serine 917. A wild type carboxy-terminal GRIP1 fragment expressed in hippocampal neurons interferes with GluR2 surface expression. On the contrary, a S917D mutant fragment does not interfere with GluR2 surface expression. Likewise, coexpression of GluR2 together with full-length wild type GRIP1 enhances GluR2 surface expression in fibroblasts, whereas full-length GRIP1-S917D had no effect. This indicates that this serine residue is implicated in AMPAR cycling. Our results identify an important regulatory mechanism in the trafficking of AMPAR subunits between internal compartments and the plasma membrane.
authors.affiliation: Brain Mind Institute, Faculté des Sciences de la Vie, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland.
authors.forename: Karina
authors.initials: K
authors.lastname: Kulangara
authors.forename: Michel
authors.initials: M
authors.lastname: Kropf
authors.forename: Liliane
authors.initials: L
authors.lastname: Glauser
authors.forename: Sarah
authors.initials: S
authors.lastname: Magnin
authors.forename: Stefano
authors.initials: S
authors.lastname: Alberi
authors.forename: Alexandre
authors.initials: A
authors.lastname: Yersin
authors.forename: Harald
authors.initials: H
authors.lastname: Hirling
mesh_terms: D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004705:Endocytosis; D047908:Intracellular Signaling Peptides and Proteins; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D010766:Phosphorylation; D021122:Protein Subunits / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017470:Receptors, Glutamate / Q000096:biosynthesis*; D015398:Signal Transduction; D009435:Synaptic Transmission
chemical_list: D002352:Carrier Proteins; C491308:Grip1 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; C461339:Nsg1 protein, rat; D021122:Protein Subunits; D017470:Receptors, Glutamate