title: Contribution of the global subunit structure and stargazin on the maturation of AMPA receptors.
abstract: Subunit assembly governs regulation of AMPA receptor (AMPA-R) synaptic delivery and determines biophysical parameters of the ion channel. However, little is known about the molecular pathways of this process. Here, we present single-particle EM three-dimensional structures of dimeric biosynthetic intermediates of the GluA2 subunit of AMPA-Rs. Consistent with the structures of intact tetramers, the N-terminal domains of the biosynthetic intermediates form dimers. Transmembrane domains also dimerize despite the two ligand-binding domains (LBDs) being separated. A significant difference was detected between the dimeric structures of the wild type and the L504Y mutant, a point mutation that blocks receptor trafficking and desensitization. In contrast to the wild type, whose LBD is separated, the LBD of the L504Y mutant was detected as a single density. Our results provide direct structural evidence that separation of the LBD within the intact dimeric subunits is critical for efficient tetramerization in the endoplasmic reticulum and further trafficking of AMPA-Rs. The contribution of stargazin on the subunit assembly of AMPA-R was examined. Our data suggest that stargazin affects AMPA-R trafficking at a later stage of receptor maturation.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, USA.
authors.forename: Natalie F
authors.initials: NF
authors.lastname: Shanks
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Maruo
authors.forename: Anthony N
authors.initials: AN
authors.lastname: Farina
authors.forename: Mark H
authors.initials: MH
authors.lastname: Ellisman
authors.forename: Terunaga
authors.initials: T
authors.lastname: Nakagawa
mesh_terms: D015220:Calcium Channels / Q000737:chemistry / Q000378:metabolism*; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D049452:Green Fluorescent Proteins / Q000235:genetics; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D007930:Leucine / Q000235:genetics; D018613:Microscopy, Confocal / Q000379:methods; D008855:Microscopy, Electron, Scanning / Q000379:methods; D008958:Models, Molecular; D008968:Molecular Conformation; D009154:Mutation / Q000235:genetics; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D054730:Protein Interaction Domains and Motifs / Q000235:genetics / Q000502:physiology; D017434:Protein Structure, Tertiary; D018091:Receptors, AMPA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D013347:Subcellular Fractions / Q000378:metabolism; D013997:Time Factors; D014162:Transfection / Q000379:methods; D014443:Tyrosine / Q000235:genetics
chemical_list: C491912:CACNG2 protein, human; D015220:Calcium Channels; D018091:Receptors, AMPA; D049452:Green Fluorescent Proteins; D014443:Tyrosine; D007930:Leucine; C104722:glutamate receptor ionotropic, AMPA 2