title: IQ-ArfGEF/BRAG1 is a guanine nucleotide exchange factor for Arf6 that interacts with PSD-95 at postsynaptic density of excitatory synapses.
abstract: ADP ribosylation factor 6 (Arf6) is a small GTPase that regulates dendritic differentiation possibly through the organization of actin cytoskeleton and membrane traffic. Here, we characterized IQ-ArfGEF/BRAG1, a guanine nucleotide exchange factor (GEF) for Arf6, in the mouse brain. In vivo Arf pull down assay demonstrated that IQ-ArfGEF/BRAG1 activated Arf6 more potently than Arf1. IQ-ArfGEF/BRAG1 mRNA was abundantly expressed in the brain with higher levels in forebrain structures and cerebellar granule cells. In hippocampal neurons, IQ-ArfGEF/BRAG1 mRNA was localized not only at neuronal cell bodies but also at dendritic processes, indicating its dendritic transport and localization. Immunoprecipitation and in vitro binding experiments revealed that IQ-ArfGEF/BRAG1 formed a protein complex with N-methyl-d-aspartate (NMDA)-type glutamate receptors through the interaction with a postsynaptic density (PSD) scaffold protein, PSD-95. Immunohistochemical analysis demonstrated that IQ-ArfGEF/BRAG1 was localized preferentially at the postsynaptic density of asymmetrical synapses on dendritic spines, but was lacking at GABAa receptor-carrying inhibitory synapses. Taken together, IQ-ArfGEF/BRAG1 forms a postsynaptic protein complex containing PSD-95 and NMDA receptors at excitatory synapses, where it may function as a GEF for Arf6.
authors.affiliation: Department of Anatomy, Kitasato University School of Medicine, Sagamihara 228-8555, Japan. sakagami@med.kitasato-u.ac.jp
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Sakagami
authors.forename: Masashi
authors.initials: M
authors.lastname: Sanda
authors.forename: Masahiro
authors.initials: M
authors.lastname: Fukaya
authors.forename: Taisuke
authors.initials: T
authors.lastname: Miyazaki
authors.forename: Jun
authors.initials: J
authors.lastname: Sukegawa
authors.forename: Teruyuki
authors.initials: T
authors.lastname: Yanagisawa
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Suzuki
authors.forename: Kohji
authors.initials: K
authors.lastname: Fukunaga
authors.forename: Masahiko
authors.initials: M
authors.lastname: Watanabe
authors.forename: Hisatake
authors.initials: H
authors.lastname: Kondo
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000166:cytology / Q000378:metabolism; D019556:COS Cells; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular / Q000379:methods; D000076122:Disks Large Homolog 4 Protein; D024202:Electrophoretic Mobility Shift Assay; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D051528:Guanylate Kinases; D006168:Guinea Pigs; D047468:Immunoprecipitation / Q000379:methods; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000378:metabolism; D011817:Rabbits; D011963:Receptors, GABA-A / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism* / Q000648:ultrastructure; D014162:Transfection
chemical_list: D000089982:ADP-Ribosylation Factor 6; D000076122:Disks Large Homolog 4 Protein; C501447:Dlg4 protein, mouse; D020662:Guanine Nucleotide Exchange Factors; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D011963:Receptors, GABA-A; D016194:Receptors, N-Methyl-D-Aspartate; D051528:Guanylate Kinases; D020727:ADP-Ribosylation Factors; C000715727:Arf6 protein, mouse