title: Cortical actin dynamics driven by formins and myosin V.
abstract: Cell morphogenesis requires complex and rapid reorganization of the actin cytoskeleton. The budding yeast Saccharomyces cerevisiae is an invaluable model system for studying molecular mechanisms driving actin dynamics. Actin cables in yeast are formin-generated linear actin arrays that serve as tracks for directed intracellular transport by type V myosins. Cables are constantly reorganized throughout the cell cycle but the molecular basis for such dynamics remains poorly understood. By combining total internal reflection microscopy, quantitative image analyses and genetic manipulations we identify kinetically distinct subpopulations of cables that are differentially driven by formins and myosin. Bni1 drives elongation of randomly oriented actin cables in unpolarized cells, whereas both formins Bnr1 and Bni1 mediate slower polymerization of cables in polarized cells. Type V myosin Myo2 surprisingly acts as a motor for translational cable motility along the cell cortex. During polarization, cells change from fast to slow cable dynamics through spatio-temporal regulation of Bni1, Bnr1 and Myo2. In summary, we identify molecular mechanisms for the regulation of cable dynamics and suggest that fast actin reorganization is necessary for fidelity of cell polarization.
authors.affiliation: AG Cellular Dynamics and Cell Patterning, Max Planck Institute of Biochemistry, Martinsried, Germany.
authors.forename: Jerry H
authors.initials: JH
authors.lastname: Yu
authors.forename: Alvaro H
authors.initials: AH
authors.lastname: Crevenna
authors.forename: Mario
authors.initials: M
authors.lastname: Bettenbühl
authors.forename: Tina
authors.initials: T
authors.lastname: Freisinger
authors.forename: Roland
authors.initials: R
authors.lastname: Wedlich-Söldner
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism*; D016764:Cell Polarity / Q000235:genetics / Q000502:physiology; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism*; D024701:Myosin Type V / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; C106463:BNR1 protein, S cerevisiae; C105191:Bni1 protein, S cerevisiae; D003598:Cytoskeletal Proteins; C077512:MYO2 protein, S cerevisiae; D008840:Microfilament Proteins; D029701:Saccharomyces cerevisiae Proteins; D024701:Myosin Type V; D018995:Myosin Heavy Chains