title: Ena/VASP proteins have an anti-capping independent function in filopodia formation.
abstract: Filopodia have been implicated in a number of diverse cellular processes including growth-cone path finding, wound healing, and metastasis. The Ena/VASP family of proteins has emerged as key to filopodia formation but the exact mechanism for how they function has yet to be fully elucidated. Using cell spreading as a model system in combination with small interfering RNA depletion of Capping Protein, we determined that Ena/VASP proteins have a role beyond anticapping activity in filopodia formation. Analysis of mutant Ena/VASP proteins demonstrated that the entire EVH2 domain was the minimal domain required for filopodia formation. Fluorescent recovery after photobleaching data indicate that Ena/VASP proteins rapidly exchange at the leading edge of lamellipodia, whereas virtually no exchange occurred at filopodial tips. Mutation of the G-actin-binding motif (GAB) partially compromised stabilization of Ena/VASP at filopodia tips. These observations led us to propose a model where the EVH2 domain of Ena/VASP induces and maintains clustering of the barbed ends of actin filaments, which putatively corresponds to a transition from lamellipodial to filopodial localization. Furthermore, the EVH1 domain, together with the GAB motif in the EVH2 domain, helps to maintain Ena/VASP at the growing barbed ends.
authors.affiliation: Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
authors.forename: Derek A
authors.initials: DA
authors.lastname: Applewhite
authors.forename: Melanie
authors.initials: M
authors.lastname: Barzik
authors.forename: Shin-Ichiro
authors.initials: S
authors.lastname: Kojima
authors.forename: Tatyana M
authors.initials: TM
authors.lastname: Svitkina
authors.forename: Frank B
authors.initials: FB
authors.lastname: Gertler
authors.forename: Gary G
authors.initials: GG
authors.lastname: Borisy
mesh_terms: D051344:Actin Capping Proteins / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D000818:Animals; D019556:COS Cells; D015815:Cell Adhesion Molecules / Q000737:chemistry / Q000378:metabolism*; D002460:Cell Line; D002465:Cell Movement; D016764:Cell Polarity; D002522:Chlorocebus aethiops; D003598:Cytoskeletal Proteins / Q000378:metabolism; D036681:Fluorescence Recovery After Photobleaching; D006801:Humans; D051379:Mice; D008840:Microfilament Proteins / Q000737:chemistry / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D011554:Pseudopodia / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D000098662:Vasodilator-Stimulated Phosphoprotein
chemical_list: D051344:Actin Capping Proteins; D000199:Actins; D015815:Cell Adhesion Molecules; D003598:Cytoskeletal Proteins; C102176:Enah protein, mouse; D008840:Microfilament Proteins; D010750:Phosphoproteins; D000098662:Vasodilator-Stimulated Phosphoprotein; D012694:Serine