title: Surface expression of GluR-D AMPA receptor is dependent on an interaction between its C-terminal domain and a 4.1 protein.
abstract: Dynamic regulation of the number and activity of AMPA receptors is believed to underlie many forms of synaptic plasticity and is presumably mediated by specific protein-protein interactions involving the C-terminal domain of the receptor. Several proteins interacting with the C-terminal tails of the glutamate receptor (GluR)-A and GluR-B subunits have been identified and implicated in the regulation of endocytosis and exocytosis, clustering, and anchoring of AMPA receptors to the cytoskeleton. In contrast, little is known of the molecular interactions of the GluR-D subunit, or of the mechanisms regulating the traffic of GluR-D-containing AMPA receptors. We analyzed the subcellular localization of homomeric GluR-D receptors carrying C-terminal deletions in transfected human embryonic kidney (HEK) 293 cells and in primary neurons by immunofluorescence microscopy and ELISA. A minimal requirement for a 14-residue cytoplasmic segment for the surface expression of homomeric GluR-D receptors was identified. Previously, a similar region in the GluR-A subunit was implicated in an interaction with 4.1 family proteins. Coimmunoprecipitation demonstrated that GluR-D associated with 4.1 protein(s) in both HEK293 cells and rat brain. Moreover, glutathione S-transferase pull-down experiments showed that the same 14-residue segment is critical for 4.1 binding to GluR-A and GluR-D. Point mutations within this segment dramatically decreased the surface expression of GluR-D in HEK293 cells, with a concomitant loss of the 4.1 interaction. Our findings demonstrate a novel molecular interaction for the GluR-D subunit and suggest that the association with the 4.1 family protein(s) plays an essential role in the transport to and stabilization of GluR-D-containing AMPA receptors at the cell surface.
authors.affiliation: Department of Biosciences, Division of Biochemistry, University of Helsinki, Helsinki, Finland FIN-00014.
authors.forename: Sarah K
authors.initials: SK
authors.lastname: Coleman
authors.forename: Chunlin
authors.initials: C
authors.lastname: Cai
authors.forename: David G
authors.initials: DG
authors.lastname: Mottershead
authors.forename: Jukka-Pekka
authors.initials: JP
authors.lastname: Haapalahti
authors.forename: Kari
authors.initials: K
authors.lastname: Keinänen
mesh_terms: D019943:Amino Acid Substitution / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D006624:Hippocampus / Q000166:cytology; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D008565:Membrane Proteins; D016297:Mutagenesis, Site-Directed; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D009479:Neuropeptides / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D011506:Proteins / Q000378:metabolism; D018091:Receptors, AMPA / Q000235:genetics / Q000378:metabolism*; D017470:Receptors, Glutamate / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D014162:Transfection
chemical_list: D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D009479:Neuropeptides; D011506:Proteins; D018091:Receptors, AMPA; D017470:Receptors, Glutamate; C028841:erythrocyte membrane band 4.1 protein; C120557:erythrocyte membrane protein band 4.1-like 1; C115953:glutamate receptor type B; C109433:glutamate receptor type D