title: The F-BAR protein Rapostlin regulates dendritic spine formation in hippocampal neurons.
abstract: Pombe Cdc15 homology proteins, characterized by Fer/CIP4 homology Bin-Amphiphysin-Rvs/extended Fer/CIP4 homology (F-BAR/EFC) domains with membrane invaginating property, play critical roles in a variety of membrane reorganization processes. Among them, Rapostlin/formin-binding protein 17 (FBP17) has attracted increasing attention as a critical coordinator of endocytosis. Here we found that Rapostlin was expressed in the developing rat brain, including the hippocampus, in late developmental stages when accelerated dendritic spine formation and maturation occur. In primary cultured rat hippocampal neurons, knockdown of Rapostlin by shRNA or overexpression of Rapostlin-QQ, an F-BAR domain mutant of Rapostlin that has no ability to induce membrane invagination, led to a significant decrease in spine density. Expression of shRNA-resistant wild-type Rapostlin effectively restored spine density in Rapostlin knockdown neurons, whereas expression of Rapostlin deletion mutants lacking the protein kinase C-related kinase homology region 1 (HR1) or Src homology 3 (SH3) domain did not. In addition, knockdown of Rapostlin or overexpression of Rapostlin-QQ reduced the uptake of transferrin in hippocampal neurons. Knockdown of Rnd2, which binds to the HR1 domain of Rapostlin, also reduced spine density and the transferrin uptake. These results suggest that Rapostlin and Rnd2 cooperatively regulate spine density. Indeed, Rnd2 enhanced the Rapostlin-induced tubular membrane invagination. We conclude that the F-BAR protein Rapostlin, whose activity is regulated by Rnd2, plays a key role in spine formation through the regulation of membrane dynamics.
authors.affiliation: Laboratory of Molecular Neurobiology, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Wakita
authors.forename: Tetsuhiro
authors.initials: T
authors.lastname: Kakimoto
authors.forename: Hironori
authors.initials: H
authors.lastname: Katoh
authors.forename: Manabu
authors.initials: M
authors.lastname: Negishi
mesh_terms: D000818:Animals; D021961:Cell Membrane Structures / Q000235:genetics / Q000378:metabolism*; D049229:Dendritic Spines / Q000235:genetics / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D006367:HeLa Cells; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D014168:Transferrin / Q000235:genetics / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D018909:src Homology Domains
chemical_list: C470009:Fnbp1 protein, rat; D009419:Nerve Tissue Proteins; D014168:Transferrin; C470010:Rnd2 protein, rat; C508704:RND2 protein, human; D020741:rho GTP-Binding Proteins