title: Cofilin cooperates with fascin to disassemble filopodial actin filaments.
abstract: Cells use a large repertoire of proteins to remodel the actin cytoskeleton. Depending on the proteins involved, F-actin is organized in specialized protrusions such as lamellipodia or filopodia, which serve diverse functions in cell migration and sensing. Although factors responsible for directed filament assembly in filopodia have been extensively characterized, the mechanisms of filament disassembly in these structures are mostly unknown. We investigated how the actin-depolymerizing factor cofilin-1 affects the dynamics of fascincrosslinked actin filaments in vitro and in live cells. By multicolor total internal reflection fluorescence microscopy and fluorimetric assays, we found that cofilin-mediated severing is enhanced in fascin-crosslinked bundles compared with isolated filaments, and that fascin and cofilin act synergistically in filament severing. Immunolabeling experiments demonstrated for the first time that besides its known localization in lamellipodia and membrane ruffles, endogenous cofilin can also accumulate in the tips and shafts of filopodia. Live-cell imaging of fluorescently tagged proteins revealed that cofilin is specifically targeted to filopodia upon stalling of protrusion and during their retraction. Subsequent electron tomography established filopodial actin filament and/or bundle fragmentation to precisely correlate with cofilin accumulation. These results identify a new mechanism of filopodium disassembly involving both fascin and cofilin.
authors.affiliation: Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany.
authors.forename: Dennis
authors.initials: D
authors.lastname: Breitsprecher
authors.forename: Stefan A
authors.initials: SA
authors.lastname: Koestler
authors.forename: Igor
authors.initials: I
authors.lastname: Chizhov
authors.forename: Maria
authors.initials: M
authors.lastname: Nemethova
authors.forename: Jan
authors.initials: J
authors.lastname: Mueller
authors.forename: Bruce L
authors.initials: BL
authors.lastname: Goode
authors.forename: J Victor
authors.initials: JV
authors.lastname: Small
authors.forename: Klemens
authors.initials: K
authors.lastname: Rottner
authors.forename: Jan
authors.initials: J
authors.lastname: Faix
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D051339:Actin Depolymerizing Factors / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D010590:Phalloidine / Q000378:metabolism; D055503:Protein Multimerization; D011554:Pseudopodia / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D059008:Time-Lapse Imaging
chemical_list: D051339:Actin Depolymerizing Factors; D002352:Carrier Proteins; D008840:Microfilament Proteins; D011993:Recombinant Fusion Proteins; C020324:fascin; D049452:Green Fluorescent Proteins; D010590:Phalloidine