title: Ena/VASP proteins enhance actin polymerization in the presence of barbed end capping proteins.
abstract: Ena/VASP proteins influence the organization of actin filament networks within lamellipodia and filopodia of migrating cells and in actin comet tails. The molecular mechanisms by which Ena/VASP proteins control actin dynamics are unknown. We investigated how Ena/VASP proteins regulate actin polymerization at actin filament barbed ends in vitro in the presence and absence of barbed end capping proteins. Recombinant His-tagged VASP increased the rate of actin polymerization in the presence of the barbed end cappers, heterodimeric capping protein (CP), CapG, and gelsolin-actin complex. Profilin enhanced the ability of VASP to protect barbed ends from capping by CP, and this required interactions of profilin with G-actin and VASP. The VASP EVH2 domain was sufficient to protect barbed ends from capping, and the F-actin and G-actin binding motifs within EVH2 were required. Phosphorylation by protein kinase A at sites within the VASP EVH2 domain regulated anti-capping and F-actin bundling by VASP. We propose that Ena/VASP proteins associate at or near actin filament barbed ends, promote actin assembly, and restrict the access of barbed end capping proteins.
authors.affiliation: Department of Biology, University of Virginia, Charlottesville, Virginia 22903, USA.
authors.forename: Melanie
authors.initials: M
authors.lastname: Barzik
authors.forename: Tatyana I
authors.initials: TI
authors.lastname: Kotova
authors.forename: Henry N
authors.initials: HN
authors.lastname: Higgs
authors.forename: Larnele
authors.initials: L
authors.lastname: Hazelwood
authors.forename: Dorit
authors.initials: D
authors.lastname: Hanein
authors.forename: Frank B
authors.initials: FB
authors.lastname: Gertler
authors.forename: Dorothy A
authors.initials: DA
authors.lastname: Schafer
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D019281:Dimerization; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D011994:Recombinant Proteins / Q000378:metabolism; D013049:Spectrin / Q000378:metabolism
chemical_list: D000199:Actins; D004268:DNA-Binding Proteins; C092744:ENA-VASP proteins; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D013049:Spectrin