title: Rapostlin is a novel effector of Rnd2 GTPase inducing neurite branching.
abstract: Rho family GTPases are central regulators of neuronal morphology. Recently, Rnd proteins, Rnd1, Rnd2, and Rnd3/RhoE, have been identified as new members of Rho family GTPases. Of these, Rnd2 is specifically expressed in neurons in brain; however, the signaling pathways of Rnd2 are not known. Here we have performed a yeast two-hybrid screen using Rnd2 as a bait and identified a novel Rnd2-effector protein, expressed predominantly in brain. We named it Rapostlin (apostle of Rnd2). Rapostlin has two functional domains, Fer-CIP4 homology (FCH) domain at the amino terminus and SH3 (Src homology 3) domain at the carboxyl terminus. In in vitro binding assays, Rapostlin specifically binds to Rnd2 among the Rho family GTPases in a GTP-dependent manner, and the Rnd2-binding domain of Rapostlin is localized between FCH and SH3 domains. Rapostlin directly binds to microtubules, and the amino-terminal region containing the FCH domain of Rapostlin is essential for this interaction. In PC12 cells, Rapostlin induces neurite branching in response to Rnd2, and at least the amino-terminal region of Rapostlin is necessary for this activity. Therefore, Rapostlin is the first effector of Rnd2, regulating neurite branch formation.
authors.affiliation: Laboratory of Molecular Neurobiology, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Hirotada
authors.initials: H
authors.lastname: Fujita
authors.forename: Hironori
authors.initials: H
authors.lastname: Katoh
authors.forename: Yukio
authors.initials: Y
authors.lastname: Ishikawa
authors.forename: Kazutoshi
authors.initials: K
authors.lastname: Mori
authors.forename: Manabu
authors.initials: M
authors.lastname: Negishi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001923:Brain Chemistry; D002460:Cell Line; D048429:Cell Size; D003001:Cloning, Molecular; D003599:Cytoskeleton / Q000378:metabolism; D017930:Genes, Reporter; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008870:Microtubules / Q000378:metabolism; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D016501:Neurites / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction / Q000502:physiology*; D020798:Two-Hybrid System Techniques; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C470009:Fnbp1 protein, rat; D009419:Nerve Tissue Proteins; D011993:Recombinant Fusion Proteins; D006160:Guanosine Triphosphate; C470010:Rnd2 protein, rat; D020741:rho GTP-Binding Proteins