title: Recruitment of Cdc42 through the GAP domain of RLIP participates in remodeling of the actin cytoskeleton and is involved in Xenopus gastrulation.
abstract: The transduction pathways that branch out of fibroblast growth factor signaling are essential for the induction of the mesoderm and the specification of the vertebrate body plan. One of these pathways is thought to control remodeling of the actin cytoskeleton through the Ral binding protein (RLIP also known as RalBP1), an effector of the small G protein Ral. RLIP contains a region of homology with the GTPase-activating protein (GAP) domain involved in the regulation of GTPases of the Rho family. We demonstrate here that the GAP domain of RLIP is responsible for the stability of the actin cytoskeleton in Xenopus laevis embryos. We also demonstrate that the complete N-terminal domain of RLIP containing the mu2 binding domain (mu2BD) and the GAP domain induces disruption of the actin cytoskeleton when targeted to the plasma membrane. Neither domain, however, has any effect on the actin cytoskeleton when individually targeted to the plasma membrane. We also determined that Cdc42-GDP, but neither Rac-GDP nor Rho-GDP, rescues the effect of expression of the membrane-localized Xenopus RLIP on the actin cytoskeleton. We show that the GAP domain of RLIP interacts in vivo with Cdc42-GTP and Cdc42-GDP. Finally, a single mutation (K244A) in the GAP sequence prevented embryos from gastrulating. These results demonstrate that to participate in the control of the actin cytoskeleton, RLIP needs its complete N-terminal region coding for the mu2BD and the GAP domain. We suggest that RLIP, by coordinating two complementary mechanisms, the endocytosis of clathrin-coated pits and the remodeling of cortical actin, participates in the gastrulation process.
authors.affiliation: Mécanismes Moléculaires du Développement, Institut Jacques Monod, CNRS UMR 7592, Universités Paris VI et Paris VII, 2 place Jussieu, 75251 Paris Cedex 05, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Boissel
authors.forename: Nathalie
authors.initials: N
authors.lastname: Houssin
authors.forename: Anissa
authors.initials: A
authors.lastname: Chikh
authors.forename: Alla
authors.initials: A
authors.lastname: Rynditch
authors.forename: Lucie
authors.initials: L
authors.lastname: Van Hove
authors.forename: Jacques
authors.initials: J
authors.lastname: Moreau
mesh_terms: D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002465:Cell Movement; D003599:Cytoskeleton / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism; D005775:Gastrula / Q000166:cytology / Q000378:metabolism; D054262:Gastrulation; D005799:Genes, Dominant; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion; D013329:Structure-Activity Relationship; D029867:Xenopus Proteins / Q000737:chemistry* / Q000378:metabolism*; D014982:Xenopus laevis / Q000196:embryology* / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D000199:Actins; D008565:Membrane Proteins; C500422:Ralbp1 protein, Xenopus; D029867:Xenopus Proteins; D020764:cdc42 GTP-Binding Protein