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MAPK interacts with XGef and is required for CPEB activation during meiosis in Xenopus oocytes

Brian T Keady1, Peiwen Kuo, Susana E Martínez

  • 1Biology Department, Boston College, Chestnut Hill, MA 02467, USA.

Journal of Cell Science
|March 9, 2007
PubMed

Insights

Meiotic resumption in Xenopus oocytes relies on CPE-binding protein (CPEB) phosphorylation. Mitogen-activated protein kinase (MAPK) directly phosphorylates CPEB, while Rho-family GTPases and Aurora kinases are not involved in early meiotic events.

Area of Science:

  • Cell Biology
  • Developmental Biology
  • Molecular Biology

Background:

  • Meiotic progression in oocytes depends on polyadenylation-induced translation of maternal mRNAs.
  • Phosphorylation of CPE-binding protein (CPEB) is crucial for this process during meiotic resumption.
  • Xenopus Gef (XGef) was previously thought to influence CPEB phosphorylation, suggesting Rho-family GTPase involvement.

Purpose of the Study:

  • To investigate the role of Xenopus Gef (XGef) and Rho-family GTPases in early meiotic events.
  • To identify the specific kinases involved in CPEB phosphorylation during meiotic resumption.
  • To elucidate the mechanism by which XGef interacts with CPEB phosphorylation pathways.

Main Methods:

  • Utilized Clostridium difficile Toxin B to inhibit Rho-family GTPases.
  • Employed U0126 (MAPK inhibitor) and ZM447439 (Aurora kinase inhibitor).
  • Performed immunoprecipitation to identify interacting proteins and kinase assays to assess phosphorylation activity.

Main Results:

  • Clostridium difficile Toxin B did not affect CPEB phosphorylation or meiotic progression, ruling out Toxin-B-sensitive GTPase involvement.
  • Mitogen-activated protein kinase (MAPK) is required for CPEB phosphorylation, whereas Aurora kinases A and B are not.
  • MAPK directly phosphorylates CPEB at specific residues (T22, T164, S184, S248) and interacts with XGef.
  • MAPK activation is transient and occurs independently of Mos protein expression.

Conclusions:

  • Xenopus Gef (XGef) does not mediate CPEB phosphorylation through Toxin-B-sensitive Rho-GTPases.
  • Mitogen-activated protein kinase (MAPK) is the primary kinase responsible for CPEB phosphorylation in early Xenopus oocyte meiosis.
  • MAPK directly phosphorylates CPEB and may interact with XGef to regulate this process, potentially priming CPEB for further modification.

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