title: Cofilin tunes the nucleotide state of actin filaments and severs at bare and decorated segment boundaries.
abstract: Actin-based motility demands the spatial and temporal coordination of numerous regulatory actin-binding proteins (ABPs), many of which bind with affinities that depend on the nucleotide state of actin filament. Cofilin, one of three ABPs that precisely choreograph actin assembly and organization into comet tails that drive motility in vitro, binds and stochastically severs aged ADP actin filament segments of de novo growing actin filaments. Deficiencies in methodologies to track in real time the nucleotide state of actin filaments, as well as cofilin severing, limit the molecular understanding of coupling between actin filament chemical and mechanical states and severing. We engineered a fluorescently labeled cofilin that retains actin filament binding and severing activities. Because cofilin binding depends strongly on the actin-bound nucleotide, direct visualization of fluorescent cofilin binding serves as a marker of the actin filament nucleotide state during assembly. Bound cofilin allosterically accelerates P(i) release from unoccupied filament subunits, which shortens the filament ATP/ADP-P(i) cap length by nearly an order of magnitude. Real-time visualization of filament severing indicates that fragmentation scales with and occurs preferentially at boundaries between bare and cofilin-decorated filament segments, thereby controlling the overall filament length, depending on cofilin binding density.
authors.affiliation: Laboratoire de Physiologie Cellulaire et Végétale, Institut de Recherches en Sciences et Technologies pour le Vivant, CEA/CNRS/INRA/UJF, F-38054 Grenoble, France.
authors.forename: Cristian
authors.initials: C
authors.lastname: Suarez
authors.forename: Jérémy
authors.initials: J
authors.lastname: Roland
authors.forename: Rajaa
authors.initials: R
authors.lastname: Boujemaa-Paterski
authors.forename: Hyeran
authors.initials: H
authors.lastname: Kang
authors.forename: Brannon R
authors.initials: BR
authors.lastname: McCullough
authors.forename: Anne-Cécile
authors.initials: AC
authors.lastname: Reymann
authors.forename: Christophe
authors.initials: C
authors.lastname: Guérin
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Martiel
authors.forename: Enrique M
authors.initials: EM
authors.lastname: De la Cruz
authors.forename: Laurent
authors.initials: L
authors.lastname: Blanchoin
mesh_terms: D000199:Actins / Q000378:metabolism*; D051338:Cofilin 1 / Q000378:metabolism*; D004926:Escherichia coli; D007091:Image Processing, Computer-Assisted; D016018:Least-Squares Analysis; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D009068:Movement / Q000502:physiology*; D009711:Nucleotides / Q000378:metabolism; D015202:Protein Engineering; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: D000199:Actins; C495813:COF1 protein, S cerevisiae; D051338:Cofilin 1; D009711:Nucleotides; D029701:Saccharomyces cerevisiae Proteins