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Inhibiting MAP kinase activity prevents calcium transients and mitosis entry in early sea urchin embryos

Lookup NU author(s): Dr Radka Philipova, Mark Larman, Patrick Harrison, Emeritus Professor Michael Whitaker

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Abstract

A transient calcium increase triggers nuclear envelope breakdown (mitosis entry) in sea urchin embryos. Cdk1/cyclin B kinase activation is also known to be required for mitosis entry. More recently, MAP kinase activity has also been shown to increase during mitosis. In sea urchin embryos, both kinases show a similar activation profile, peaking at the time of mitosis entry. We tested whether the activity of both kinases is required for mitosis entry and whether either kinase controls mitotic calcium signals. We found that reducing the activity of either mitotic kinase prevents nuclear envelope breakdown, despite the presence of a calcium transient, when cdk1/cyclin B kinase activity is alone inhibited. When MAP kinase activity alone was inhibited, the calcium signal was absent, suggesting that MAP kinase activity is required to generate the calcium transient that triggers nuclear envelope breakdown. However, increasing intracellular free calcium by microinjection of calcium buffers or InsP 3 while MAP kinase was inhibited did not itself induce nuclear envelope breakdown, indicating that additional MAP kinase-regulated events are necessary. After MAP kinase inhibition early in the cell cycle, the early events of the cell cycle (pronuclear migration/fusion and DNA synthesis) were unaffected, but chromosome condensation and spindle assembly are prevented. These data indicate that in sea urchin embryos, MAP kinase activity is part of a signaling complex alongside two components previously shown to be essential for entry into mitosis: the calcium transient and the increase in cdk1/cyclinB kinase activity. © 2005 by The American Society for Biochemistry and Molecular Biology, Inc.

Publication metadata

Author(s): Philipova R, Larman MG, Leckie CP, Harrison PK, Groigno L, Whitaker M

Publication type: Article

Publication status: Published

Journal: Journal of Biological Chemistry

Year: 2005

Volume: 280

Issue: 26

Pages: 24957-24967

ISSN (print): 0021-9258

ISSN (electronic): 1083-351X

Publisher: American Society for Biochemistry and Molecular Biology, Inc.

URL: http://dx.doi.org/10.1074/jbc.M414437200

DOI: 10.1074/jbc.M414437200

PubMed id: 15843380

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