title: Cofilin, but not profilin, is required for myosin-I-induced actin polymerization and the endocytic uptake in yeast.
abstract: Mutations in the budding yeast myosins-I (MYO3 and MYO5) cause defects in the actin cytoskeleton and in the endocytic uptake. Robust evidence also indicates that these proteins induce Arp2/3-dependent actin polymerization. Consistently, we have recently demonstrated, using fluorescence microscopy, that Myo5p is able to induce cytosol-dependent actin polymerization on the surface of Sepharose beads. Strikingly, we now observed that, at short incubation times, Myo5p induced the formation of actin foci that resembled the yeast cortical actin patches, a plasma membrane-associated structure that might be involved in the endocytic uptake. Analysis of the machinery required for the formation of the Myo5p-induced actin patches in vitro demonstrated that the Arp2/3 complex was necessary but not sufficient in the assay. In addition, we found that cofilin was directly involved in the process. Strikingly though, the cofilin requirement seemed to be independent of its ability to disassemble actin filaments and profilin, a protein that closely cooperates with cofilin to maintain a rapid actin filament turnover, was not needed in the assay. In agreement with these observations, we found that like the Arp2/3 complex and the myosins-I, cofilin was essential for the endocytic uptake in vivo, whereas profilin was dispensable.
authors.affiliation: Biochemiezentrum of the University of Heidelberg (BZH), D-69120 Heidelberg, Germany.
authors.forename: Fatima-Zahra
authors.initials: FZ
authors.lastname: Idrissi
authors.forename: Bianka L
authors.initials: BL
authors.lastname: Wolf
authors.forename: M Isabel
authors.initials: MI
authors.lastname: Geli
mesh_terms: D051339:Actin Depolymerizing Factors; D000199:Actins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D003285:Contractile Proteins; D004705:Endocytosis / Q000502:physiology*; D006801:Humans; D046911:Macromolecular Substances; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D024461:Myosin Type I / Q000235:genetics / Q000378:metabolism*; D051304:Profilins; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D051339:Actin Depolymerizing Factors; D000199:Actins; D003285:Contractile Proteins; C100412:MYO5 protein, S cerevisiae; D046911:Macromolecular Substances; D008840:Microfilament Proteins; C495738:PFN1 protein, human; D051304:Profilins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D024461:Myosin Type I