Mammalian twinfilin sequesters ADP-G-actin and caps filament barbed ends: implications in motility

• Published in: The EMBO journal Vol. 25; no. 6; pp. 1184 - 1195
• Main Authors: Helfer, E, Nevalainen, E.M, Naumanen, P, Romero, S, Didry, D, Pantaloni, D, Lappalainen, P, Carlier, M.F
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 22-03-2006; Blackwell Publishing Ltd; EMBO Press
• Subjects: actin; Actin Cytoskeleton - metabolism; actin depolymerizing factor homology domains; actin-binding proteins; Actins - metabolism; Adenosine diphosphate; Adenosine Diphosphate - analogs & derivatives; Adenosine Diphosphate - metabolism; ADF homology domains; ADP-G-actin; Animals; binding proteins; Biochemistry; Biochemistry, Molecular Biology; Biomimetics; Biophysics; capping proteins; Cell Movement; Data Interpretation, Statistical; Destrin - metabolism; Drosophila melanogaster; Drosophila melanogaster - genetics; Drosophila melanogaster - growth & development; Drosophila melanogaster - metabolism; Drosophila Proteins - genetics; Drosophila Proteins - metabolism; Endosomes; Gelsolin - metabolism; Life Sciences; Mammals; Mice; Microfilament Proteins - genetics; Microfilament Proteins - metabolism; motility; protein-protein interactions; Proteins; Saccharomyces cerevisiae; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - growth & development; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; twinfilin; yeasts; motility; actin; ADF homology domains; capping proteins; twinfilin
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1038/sj.emboj.7601019

Twinfilins are conserved actin‐binding proteins composed of two actin depolymerizing factor homology (ADF‐H) domains. Twinfilins are involved in diverse morphological and motile processes, but their mechanism of action has not been elucidated. Here, we show that mammalian twinfilin both sequesters ADP‐G‐actin and caps filament barbed ends with preferential affinity for ADP‐bound ends. Twinfilin replaces capping protein and promotes motility of N‐WASP functionalized beads in a biomimetic motility assay, indicating that the capping activity supports twinfilin's function in motility. Consistently, in vivo twinfilin localizes to actin tails of propelling endosomes. The ADP‐actin‐sequestering activity cooperates with the filament capping activity of twinfilin to finely regulate motility due to processive filament assembly catalyzed by formin‐functionalized beads. The isolated ADF‐H domains do not cap barbed ends nor promote motility, but sequester ADP‐actin, the C‐terminal domain showing the highest affinity. A structural model for binding of twinfilin to barbed ends is proposed based on the similar foldings of twinfilin ADF‐H domains and gelsolin segments.