title: A palmitoylation switch mechanism regulates Rac1 function and membrane organization.
abstract: The small GTPase Rac1 plays important roles in many processes, including cytoskeletal reorganization, cell migration, cell-cycle progression and gene expression. The initiation of Rac1 signalling requires at least two mechanisms: GTP loading via the guanosine triphosphate (GTP)/guanosine diphosphate (GDP) cycle, and targeting to cholesterol-rich liquid-ordered plasma membrane microdomains. Little is known about the molecular mechanisms governing this specific compartmentalization. We show that Rac1 can incorporate palmitate at cysteine 178 and that this post-translational modification targets Rac1 for stabilization at actin cytoskeleton-linked ordered membrane regions. Palmitoylation of Rac1 requires its prior prenylation and the intact C-terminal polybasic region and is regulated by the triproline-rich motif. Non-palmitoylated Rac1 shows decreased GTP loading and lower association with detergent-resistant (liquid-ordered) membranes (DRMs). Cells expressing no Rac1 or a palmitoylation-deficient mutant have an increased content of disordered membrane domains, and markers of ordered membranes isolated from Rac1-deficient cells do not correctly partition in DRMs. Importantly, cells lacking Rac1 palmitoylation show spreading and migration defects. These data identify palmitoylation as a mechanism for Rac1 function in actin cytoskeleton remodelling by controlling its membrane partitioning, which in turn regulates membrane organization.
authors.affiliation: Department of Vascular Biology, Integrin Signaling Laboratory, Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain.
authors.forename: Inmaculada
authors.initials: I
authors.lastname: Navarro-Lérida
authors.forename: Sara
authors.initials: S
authors.lastname: Sánchez-Perales
authors.forename: María
authors.initials: M
authors.lastname: Calvo
authors.forename: Carles
authors.initials: C
authors.lastname: Rentero
authors.forename: Yi
authors.initials: Y
authors.lastname: Zheng
authors.forename: Carlos
authors.initials: C
authors.lastname: Enrich
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Del Pozo
mesh_terms: D000595:Amino Acid Sequence; D001704:Biopolymers / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D008969:Molecular Sequence Data; D019308:Palmitic Acid / Q000378:metabolism*; D017368:Protein Prenylation; D017386:Sequence Homology, Amino Acid; D020830:rac1 GTP-Binding Protein / Q000502:physiology*
chemical_list: D001704:Biopolymers; D019308:Palmitic Acid; D006160:Guanosine Triphosphate; D020830:rac1 GTP-Binding Protein