title: SynArfGEF is a guanine nucleotide exchange factor for Arf6 and localizes preferentially at post-synaptic specializations of inhibitory synapses.
abstract: SynArfGEF, also known as BRAG3 or IQSEC3, is a member of the brefeldin A-resistant Arf-GEF/IQSEC family and was originally identified by screening for mRNA species associated with the post-synaptic density fraction. In this study, we demonstrate that synArfGEF activates Arf6, using Arf pull down and transferrin incorporation assays. Immunohistochemical analysis reveals that synArfGEF is present in somata and dendrites as puncta in close association with inhibitory synapses, whereas immunoelectron microscopic analysis reveals that synArfGEF localizes preferentially at post-synaptic specializations of symmetric synapses. Using yeast two-hybrid and pull down assays, we show that synArfGEF is able to bind utrophin/dystrophin and S-SCAM/MAGI-2 scaffolding proteins that localize at inhibitory synapses. Double immunostaining reveals that synArfGEF co-localizes with dystrophin and S-SCAM in cultured hippocampal neurons and cerebellar cortex, respectively. Both β-dystroglycan and S-SCAM were immunoprecipitated from brain lysates using anti-synArfGEF IgG. Taken together, these findings suggest that synArfGEF functions as a novel regulator of Arf6 at inhibitory synapses and associates with the dystrophin-associated glycoprotein complex and S-SCAM.
authors.affiliation: Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Fukaya
authors.forename: Akifumi
authors.initials: A
authors.lastname: Kamata
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Hara
authors.forename: Hideaki
authors.initials: H
authors.lastname: Tamaki
authors.forename: Osamu
authors.initials: O
authors.lastname: Katsumata
authors.forename: Naoki
authors.initials: N
authors.lastname: Ito
authors.forename: Shin'ichi
authors.initials: S
authors.lastname: Takeda
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Hata
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Suzuki
authors.forename: Masahiko
authors.initials: M
authors.lastname: Watanabe
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Harvey
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Sakagami
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000235:genetics / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001921:Brain / Q000166:cytology; D002352:Carrier Proteins / Q000378:metabolism; D002461:Cell Line, Transformed; D002522:Chlorocebus aethiops; D016189:Dystrophin / Q000378:metabolism; D005786:Gene Expression Regulation / Q000502:physiology; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D051528:Guanylate Kinases; D006801:Humans; D047468:Immunoprecipitation / Q000379:methods; D051379:Mice; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism; D013569:Synapses / Q000378:metabolism* / Q000648:ultrastructure; D014162:Transfection / Q000379:methods; D020798:Two-Hybrid System Techniques; D050495:Vesicular Inhibitory Amino Acid Transport Proteins / Q000378:metabolism
chemical_list: D000089982:ADP-Ribosylation Factor 6; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D016189:Dystrophin; D020662:Guanine Nucleotide Exchange Factors; C114103:Magi2 protein, rat; D011506:Proteins; D050495:Vesicular Inhibitory Amino Acid Transport Proteins; C492244:Viaat protein, mouse; D006160:Guanosine Triphosphate; D051528:Guanylate Kinases; C485777:MAGI2 protein, human; C405684:Magi2 protein, mouse; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; C000715727:Arf6 protein, mouse; C000715349:Arf6 protein, rat