title: Actin depolymerizing factor (ADF/cofilin) enhances the rate of filament turnover: implication in actin-based motility.
abstract: Actin-binding proteins of the actin depolymerizing factor (ADF)/cofilin family are thought to control actin-based motile processes. ADF1 from Arabidopsis thaliana appears to be a good model that is functionally similar to other members of the family. The function of ADF in actin dynamics has been examined using a combination of physical-chemical methods and actin-based motility assays, under physiological ionic conditions and at pH 7.8. ADF binds the ADP-bound forms of G- or F-actin with an affinity two orders of magnitude higher than the ATP- or ADP-Pi-bound forms. A major property of ADF is its ability to enhance the in vitro turnover rate (treadmilling) of actin filaments to a value comparable to that observed in vivo in motile lamellipodia. ADF increases the rate of propulsion of Listeria monocytogenes in highly diluted, ADF-limited platelet extracts and shortens the actin tails. These effects are mediated by the participation of ADF in actin filament assembly, which results in a change in the kinetic parameters at the two ends of the actin filament. The kinetic effects of ADF are end specific and cannot be accounted for by filament severing. The main functionally relevant effect is a 25-fold increase in the rate of actin dissociation from the pointed ends, while the rate of dissociation from the barbed ends is unchanged. This large increase in the rate-limiting step of the monomer-polymer cycle at steady state is responsible for the increase in the rate of actin-based motile processes. In conclusion, the function of ADF is not to sequester G-actin. ADF uses ATP hydrolysis in actin assembly to enhance filament dynamics.
authors.affiliation: Dynamique du Cytosquelette, Laboratoire d'Enzymologie et Biochimie Structurales, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France. carlier@lebs.cnrs-gif.fr
authors.forename: M F
authors.initials: MF
authors.lastname: Carlier
authors.forename: V
authors.initials: V
authors.lastname: Laurent
authors.forename: J
authors.initials: J
authors.lastname: Santolini
authors.forename: R
authors.initials: R
authors.lastname: Melki
authors.forename: D
authors.initials: D
authors.lastname: Didry
authors.forename: G X
authors.initials: GX
authors.lastname: Xia
authors.forename: Y
authors.initials: Y
authors.lastname: Hong
authors.forename: N H
authors.initials: NH
authors.lastname: Chua
authors.forename: D
authors.initials: D
authors.lastname: Pantaloni
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism* / Q000648:ultrastructure; D051339:Actin Depolymerizing Factors; D000199:Actins / Q000737:chemistry / Q000502:physiology*; D000255:Adenosine Triphosphate / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000235:genetics; D001704:Biopolymers; D001792:Blood Platelets / Q000166:cytology; D002465:Cell Movement / Q000187:drug effects; D051345:Destrin; D006801:Humans; D007700:Kinetics; D008089:Listeria monocytogenes / Q000166:cytology / Q000187:drug effects; D008840:Microfilament Proteins / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D010766:Phosphorylation; D010940:Plant Proteins / Q000235:genetics; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D011817:Rabbits; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D051339:Actin Depolymerizing Factors; D000199:Actins; D001704:Biopolymers; C495824:DSTN protein, human; D051345:Destrin; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; D010940:Plant Proteins; D000255:Adenosine Triphosphate