title: Activation of ADF/cofilin by phosphorylation-regulated Slingshot phosphatase is required for the meiotic spindle assembly in Xenopus laevis oocytes.
abstract: We identify Xenopus ADF/cofilin (XAC) and its activator, Slingshot phosphatase (XSSH), as key regulators of actin dynamics essential for spindle microtubule assembly during Xenopus oocyte maturation. Phosphorylation of XSSH at multiple sites within the tail domain occurs just after germinal vesicle breakdown (GVBD) and is accompanied by dephosphorylation of XAC, which was mostly phosphorylated in immature oocytes. This XAC dephosphorylation after GVBD is completely suppressed by latrunculin B, an actin monomer-sequestering drug. On the other hand, jasplakinolide, an F-actin-stabilizing drug, induces dephosphorylation of XAC. Effects of latrunculin B and jasplakinolide are reconstituted in cytostatic factor-arrested extracts (CSF extracts), and XAC dephosphorylation is abolished by depletion of XSSH from CSF extracts, suggesting that XSSH functions as an actin filament sensor to facilitate actin filament dynamics via XAC activation. Injection of anti-XSSH antibody, which blocks full phosphorylation of XSSH after GVBD, inhibits both meiotic spindle formation and XAC dephosphorylation. Coinjection of constitutively active XAC with the antibody suppresses this phenotype. Treatment of oocytes with jasplakinolide also impairs spindle formation. These results strongly suggest that elevation of actin dynamics by XAC activation through XSSH phosphorylation is required for meiotic spindle assembly in Xenopus laevis.
authors.affiliation: Department of Nanobiology, Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Iwase
authors.forename: Ryuhei
authors.initials: R
authors.lastname: Sato
authors.forename: Pieter-Jan
authors.initials: PJ
authors.lastname: De Bock
authors.forename: Kris
authors.initials: K
authors.lastname: Gevaert
authors.forename: Saburo
authors.initials: S
authors.lastname: Fujiki
authors.forename: Toshinobu
authors.initials: T
authors.lastname: Tawada
authors.forename: Miyako
authors.initials: M
authors.lastname: Kuchitsu
authors.forename: Yuka
authors.initials: Y
authors.lastname: Yamagishi
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Ono
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Abe
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D051339:Actin Depolymerizing Factors / Q000235:genetics / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D047630:Depsipeptides / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D015151:Immunoblotting; D008540:Meiosis; D008856:Microscopy, Fluorescence; D009154:Mutation; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D008941:Spindle Apparatus / Q000378:metabolism*; D053778:Thiazolidines / Q000494:pharmacology; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis / Q000235:genetics / Q000378:metabolism*
chemical_list: D051339:Actin Depolymerizing Factors; D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D047630:Depsipeptides; D053778:Thiazolidines; D029867:Xenopus Proteins; C057531:jasplakinolide; D010749:Phosphoprotein Phosphatases; C037068:latrunculin B