title: The two Caenorhabditis elegans actin-depolymerizing factor/cofilin proteins differently enhance actin filament severing and depolymerization.
abstract: Actin-depolymerizing factor (ADF)/cofilin enhances the turnover of actin filaments by two separable activities: filament severing and pointed-end depolymerization. Multicellular organisms express multiple ADF/cofilin isoforms in a tissue-specific manner, and the vertebrate proteins are grouped into ADFs and cofilins on the basis of their biochemical activity. A recent comparative study has shown that ADF has greater severing and depolymerizing activities than cofilin [Chen, H., Bernstein, B. W., Sneider, J. M., Boyle, J. A., Minamide, L. S., and Bamburg, J. R. (2004) Biochemistry 43, 7127-7142]. Here, we show that the two Caenorhabditis elegans ADF/cofilin isoforms exhibit different activities for severing and depolymerizing actin filaments. The ADF-like non-muscle isoform UNC-60A had greater activities to cause net depolymerization and inhibit polymerization than the cofilin-like muscle isoform UNC-60B. Surprisingly, UNC-60B exhibited much stronger severing activity than UNC-60A, which was the opposite of what was observed for vertebrate counterparts. Moreover, UNC-60B induced much faster pointed-end depolymerization of rabbit muscle actin than UNC-60A, while UNC-60A caused slightly faster depolymerization of C. elegans actin than UNC-60B. These results suggest that cofilin-like UNC-60B is kinetically more efficient in enhancing actin turnover than ADF-like UNC-60A, while ADF-like UNC-60A is suitable for maintaining higher concentrations of monomeric actin. These functional differences might be specifically adapted for different actin dynamics in muscle and non-muscle cells.
authors.affiliation: Department of Pathology, Emory University, Atlanta, Georgia 30322, USA.
authors.forename: Sawako
authors.initials: S
authors.lastname: Yamashiro
authors.forename: Kurato
authors.initials: K
authors.lastname: Mohri
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Ono
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D051339:Actin Depolymerizing Factors / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D000818:Animals; D017173:Caenorhabditis elegans / Q000737:chemistry* / Q000166:cytology; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism; D007700:Kinetics; D008840:Microfilament Proteins / Q000378:metabolism; D011108:Polymers / Q000378:metabolism*; D011485:Protein Binding; D020033:Protein Isoforms / Q000378:metabolism; D011817:Rabbits
chemical_list: D051339:Actin Depolymerizing Factors; D000199:Actins; D029742:Caenorhabditis elegans Proteins; D008840:Microfilament Proteins; D011108:Polymers; D020033:Protein Isoforms; C495209:UNC-60 protein, C elegans