title: Cell cycle-associated changes in Slingshot phosphatase activity and roles in cytokinesis in animal cells.
abstract: During cytokinesis the actomyosin-based contractile ring is formed at the equator, constricted, and then disassembled prior to cell abscission. Cofilin stimulates actin filament disassembly and is implicated in the regulation of contractile ring dynamics. However, little is known about the mechanism controlling cofilin activity during cytokinesis. Cofilin is inactivated by phosphorylation on Ser-3 by LIM-kinase-1 (LIMK1) and is reactivated by a protein phosphatase Slingshot-1 (SSH1). Here we show that the phosphatase activity of SSH1 decreases in the early stages of mitosis and is elevated in telophase and cytokinesis in HeLa cells, a time course correlating with that of cofilin dephosphorylation. SSH1 co-localizes with F-actin and accumulates onto the cleavage furrow and the midbody. Expression of a phosphatase-inactive SSH1 induces aberrant accumulation of F-actin and phospho-cofilin near the midbody in the final stage of cytokinesis and frequently leads to the regression of the cleavage furrow and the formation of multinucleate cells. Co-expression of cofilin rescued the inhibitory effect of phosphatase-inactive SSH1 on cytokinesis. These results suggest that SSH1 plays a critical role in cytokinesis by dephosphorylating and reactivating cofilin in later stages of mitosis.
authors.affiliation: Department of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Kaji
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Ohashi
authors.forename: Mika
authors.initials: M
authors.lastname: Shuin
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Niwa
authors.forename: Tadashi
authors.initials: T
authors.lastname: Uemura
authors.forename: Kensaku
authors.initials: K
authors.lastname: Mizuno
mesh_terms: D051339:Actin Depolymerizing Factors; D000199:Actins / Q000378:metabolism; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics* / Q000502:physiology*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D054461:Lim Kinases; D008164:Luminescent Proteins / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008938:Mitosis; D010749:Phosphoprotein Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D013692:Telophase; D013997:Time Factors
chemical_list: D051339:Actin Depolymerizing Factors; D000199:Actins; D001426:Bacterial Proteins; D029721:Drosophila Proteins; D018840:HSP70 Heat-Shock Proteins; D008164:Luminescent Proteins; D008840:Microfilament Proteins; C054562:yellow fluorescent protein, Bacteria; D011494:Protein Kinases; C515892:LIMK1 protein, human; D054461:Lim Kinases; C448559:ssh protein, Drosophila; D010749:Phosphoprotein Phosphatases; D010744:Phosphoric Monoester Hydrolases