Mammalian twinfilin sequesters ADP-G-actin and caps filament barbed ends: implications in motility.
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.
Helfer
Emmanuèle
E
Cytoskeleton Dynamics and Motility, LEBS, CNRS, Gif-sur-Yvette, France.
Nevalainen
Elisa M
EM
Naumanen
Perttu
P
Romero
Stéphane
S
Didry
Dominique
D
Pantaloni
Dominique
D
Lappalainen
Pekka
P
Carlier
Marie-France
MF
D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000031:analogs & derivatives* / Q000378:metabolism; D000818:Animals; D002465:Cell Movement; D003627:Data Interpretation, Statistical; D051345:Destrin / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D011992:Endosomes; D018260:Gelsolin / Q000378:metabolism; D051379:Mice; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
D000199:Actins; D000244:Adenosine Diphosphate; D051345:Destrin; D029721:Drosophila Proteins; D018260:Gelsolin; D008840:Microfilament Proteins; D029701:Saccharomyces cerevisiae Proteins; C042634:ADP-G-actin; C485190:Twf1 protein, mouse; C113980:TWF1 protein, S cerevisiae; C442839:twf protein, Drosophila