title: SWAP-70 identifies a transitional subset of actin filaments in motile cells.
abstract: Functionally different subsets of actin filament arrays contribute to cellular organization and motility. We report the identification of a novel subset of loose actin filament arrays through regulated association with the widely expressed protein SWAP-70. These loose actin filament arrays were commonly located behind protruding lamellipodia and membrane ruffles. Visualization of these loose actin filament arrays was dependent on lamellipodial protrusion and the binding of the SWAP-70 PH-domain to a 3'-phosphoinositide. SWAP-70 with a functional pleckstrin homology-domain lacking the C-terminal 60 residues was targeted to the area of the loose actin filament arrays, but it did not associate with actin filaments. The C-terminal 60 residues were sufficient for actin filament association, but they provided no specificity for the subset of loose actin filament arrays. These results identify SWAP-70 as a phosphoinositide 3-kinase signaling-dependent marker for a distinct, hitherto unrecognized, array of actin filaments. Overexpression of SWAP-70 altered the actin organization and lamellipodial morphology. These alterations were dependent on a proper subcellular targeting of SWAP-70. We propose that SWAP-70 regulates the actin cytoskeleton as an effector or adaptor protein in response to agonist stimulated phosphatidylinositol (3,4)-bisphosphate production and cell protrusion.
authors.affiliation: Institut für Allgemeine Zoologie und Genetik, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany.
authors.forename: Pirta
authors.initials: P
authors.lastname: Hilpelä
authors.forename: Pia
authors.initials: P
authors.lastname: Oberbanscheidt
authors.forename: Penelope
authors.initials: P
authors.lastname: Hahne
authors.forename: Martin
authors.initials: M
authors.lastname: Hund
authors.forename: Georg
authors.initials: G
authors.lastname: Kalhammer
authors.forename: J Victor
authors.initials: JV
authors.lastname: Small
authors.forename: Martin
authors.initials: M
authors.lastname: Bähler
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000818:Animals; D002465:Cell Movement / Q000502:physiology*; D002478:Cells, Cultured; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D015778:Minor Histocompatibility Antigens; D009154:Mutation; D009218:Myosins / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011554:Pseudopodia / Q000378:metabolism; D041701:Swiss 3T3 Cells; D020798:Two-Hybrid System Techniques
chemical_list: D004268:DNA-Binding Proteins; D020662:Guanine Nucleotide Exchange Factors; D015778:Minor Histocompatibility Antigens; D009687:Nuclear Proteins; C491873:SWAP70 protein, human; C113365:Swap70 protein, mouse; C113469:myosin IXB; D019869:Phosphatidylinositol 3-Kinases; D009218:Myosins