title: Flightless I is a focal adhesion-associated actin-capping protein that regulates cell migration.
abstract: The role of adhesion-associated actin-binding proteins in cell migration is not well defined. In mouse fibroblasts we screened for focal adhesion-associated proteins that were isolated with collagen-coated beads and detected by tandem mass spectrometry. We identified flightless I (FliI) as an actin-binding protein in focal adhesion fractions, which was verified by immunoblotting. By confocal microscopy most FliI was distributed throughout the cytosol and in focal adhesions. By sedimentation assays and in vitro binding assays, we found that FliI associates with actin filaments and actin monomers. Assays using purified proteins showed that FliI inhibits actin polymerization and caps but does not sever actin filaments. Cells with FliI knockdown or cells overexpressing FliI migrated more or less rapidly, respectively, than wild-type controls. Compared with controls, cells with FliI knockdown were less adherent than wild-type cells, exhibited reduced numbers of focal adhesions containing activated β1 integrins and vinculin, and exhibited increased incorporation of actin monomers into nascent filaments at focal adhesions. These data indicate that FliI regulates cell migration through its localization to focal adhesions and its ability to cap actin filaments, which collectively affect focal adhesion maturation.
authors.affiliation: Matrix Dynamics Group, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Mohammad
authors.forename: Pamma D
authors.initials: PD
authors.lastname: Arora
authors.forename: Yeganeh
authors.initials: Y
authors.lastname: Naghibzadeh
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Wang
authors.forename: Jeff
authors.initials: J
authors.lastname: Li
authors.forename: Wendall
authors.initials: W
authors.lastname: Mascarenhas
authors.forename: Paul A
authors.initials: PA
authors.lastname: Janmey
authors.forename: John F
authors.initials: JF
authors.lastname: Dawson
authors.forename: Christopher A
authors.initials: CA
authors.lastname: McCulloch
mesh_terms: D051344:Actin Capping Proteins / Q000378:metabolism*; D000199:Actins / Q000502:physiology; D000818:Animals; D002352:Carrier Proteins; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D003598:Cytoskeletal Proteins / Q000502:physiology*; D022001:Focal Adhesions / Q000378:metabolism*; D051379:Mice; D008840:Microfilament Proteins; D015534:Trans-Activators
chemical_list: D051344:Actin Capping Proteins; D000199:Actins; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; C000609263:FlII protein, mouse; D008840:Microfilament Proteins; D015534:Trans-Activators