title: Spatial and temporal activation of the small GTPases RhoA and Rac1 by the netrin-1 receptor UNC5a during neurite outgrowth.
abstract: Netrin-1 attracts or repels growing axons during development. The UNC5 receptors mediate the repulsive response, either alone or in complex with DCC receptors. The signaling mechanisms activated by UNC5 are poorly understood. Here, we examined the role of Rho GTPases in UNC5a signaling. We found that UNC5a induced neurite outgrowth in N1E-115 neuroblastoma cells in a netrin-1- and Rac1-dependent manner. UNC5a lacking its cytoplasmic tail also mediated this effect. In fibroblasts, UNC5a was able to activate RhoA and to a lower extent Rac1 and Cdc42 in response to netrin-1. Using Fluorescence Resonance Energy Transfer (FRET) intermolecular probes, we visualized the spatial and temporal activation of Rac1, Cdc42 and RhoA in live N1E-115 cells expressing UNC5a during neurite outgrowth. We found that Rac1 but not Cdc42 was transiently activated at the leading edge of the cell during neurite initiation. However, at later times when well-developed neurites were formed, active RhoA was found in the cell body and at the base of the neuronal leading process in UNC5a-expressing cells. Together, these findings demonstrate that the netrin-1 receptor UNC5a is able to induce neurite outgrowth and to differentially activate RhoA and Rac1 during neurite extension in a spatial and temporal manner.
authors.affiliation: Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada H3A 2B2.
authors.forename: Mariêve
authors.initials: M
authors.lastname: Picard
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Petrie
authors.forename: Judith
authors.initials: J
authors.lastname: Antoine-Bertrand
authors.forename: Etienne
authors.initials: E
authors.lastname: Saint-Cyr-Proulx
authors.forename: Josée-France
authors.initials: JF
authors.lastname: Villemure
authors.forename: Nathalie
authors.initials: N
authors.lastname: Lamarche-Vane
mesh_terms: D000818:Animals; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D005347:Fibroblasts / Q000378:metabolism; D009414:Nerve Growth Factors / Q000378:metabolism; D000075386:Netrin Receptors; D000075388:Netrin-1; D016501:Neurites / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000032:analysis / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000032:analysis / Q000378:metabolism*
chemical_list: D009414:Nerve Growth Factors; D000075386:Netrin Receptors; D011956:Receptors, Cell Surface; D025521:Tumor Suppressor Proteins; D000075388:Netrin-1; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein