Activation of ADF/cofilin by phosphorylation-regulated Slingshot phosphatase is required for the meiotic spindle assembly in Xenopus laevis oocytes

• Type of Material: Article
• Authors: Shohei Iwase, Chiba University; Ryuhei Sato, Chiba University; Pieter-Jan De Bock, Ghent University; Kris Gevaert, Ghent University; Saburo Fujiki, Chiba University; Toshinobu Tawada, Chiba University; Miyako Kuchitsu, Chiba University; Yuka Yamagishi, Chiba University; Shoichiro Ono, Emory University; Hiroshi Abe, Chiba University
• Language: English
• Date: 2013-06-15
• Publisher: American Society for Cell Biology
• Publication Version: Final Published Version
• Copyright Statement: © 2013 Iwase et al.
• License: Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported
• Final Published Version (URL): http://dx.doi.org/10.1091/mbc.E12-12-0851
• Title of Journal or Parent Work: Molecular Biology of the Cell
• ISSN: 1059-1524
• Volume: 24
• Issue: 12
• Start Page: 1933
• End Page: 1946
• Grant/Funding Information: S.O. was supported by National Institutes of Health Grant R01 AR48615.
• Keywords: NUCLEAR-ENVELOPE; Life Sciences & Biomedicine; MOUSE OOCYTES; Cell Biology; CORTICAL POLARITY; Science & Technology; POLAR BODY EXTRUSION; FUNCTIONAL INVOLVEMENT; MICROTUBULE ORGANIZATION; LIM-KINASE; ACTIN-DEPOLYMERIZING FACTOR; COFILIN PHOSPHORYLATION; F-ACTIN
• Research Categories: Health Sciences, Public Health; Biology, Microbiology

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.