MAP kinase activity increases during mitosis in early sea urchin embryos

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Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development
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Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development

Published on: June 15, 2017

R Philipova1, M Whitaker

  • 1Department of Physiological Sciences, University of Newcastle upon Tyne Medical School, Framlington Place, Newcastle upon Tyne NE1 2HH, UK.

Journal of Cell Science
|August 14, 1998
PubMed

Insights

Mitogen-activated protein kinase (MAPK) activity rises during mitosis in early sea urchin embryonic cell cycles. Calcium signals, like fertilization, activate MAPK, indicating its role in early embryonic development.

Area of Science:

  • Cell Biology
  • Developmental Biology
  • Molecular Biology

Background:

  • Mitogen-activated protein kinase (MAPK) is crucial in cellular signaling pathways.
  • MAPK activation is known to occur during meiosis, but its role in mitosis is less understood.
  • Early embryonic cell cycles involve complex regulatory mechanisms for cell division.

Purpose of the Study:

  • To investigate the activity profile of MAPK during the early mitotic cell cycles of the sea urchin embryo.
  • To determine the molecular identity and activation mechanisms of MAPK in early sea urchin development.
  • To explore the role of calcium signaling in MAPK activation during fertilization and early development.

Main Methods:

  • Assessed MBP kinase activity in whole cell extracts and immunoprecipitates using an anti-MAPK antibody.
  • Performed in-gel assays to confirm MBP kinase activity and associated protein size.
  • Utilized anti-phosphotyrosine and specific anti-MAPK antibodies for protein characterization and purification.
  • Conducted peptide sequencing to confirm protein homology.
  • Stimulated unfertilized eggs with a calcium ionophore to investigate calcium-dependent activation.

Main Results:

  • MBP kinase activity, associated with a 44 kDa protein recognized by anti-MAPK antibodies, increased during mitosis in the first two embryonic cell cycles.
  • The 44 kDa protein showed phosphorylation consistent with MAPK activation.
  • MAPK activity increased post-fertilization, correlating with interphase, and was stimulated by calcium ionophore treatment.
  • Peptide sequencing confirmed the 44 kDa protein is homologous to known MAPKs.

Conclusions:

  • MAPK activation occurs not only during meiosis but also during mitotic cell cycles in early sea urchin development.
  • Fertilization-induced calcium increase activates MAPK in the sea urchin egg, suggesting a role for calcium signaling in early embryonic progression.
  • The findings highlight MAPK as a key regulator in early embryonic cell division and development.

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