Editors' ChoiceFertilization

Calcium Turns Off MAP Kinase

Science's STKE  01 Feb 2000:
Vol. 2000, Issue 17, pp. tw2
DOI: 10.1126/stke.2000.17.tw2

The MAP kinase pathway is active in unfertilized oocytes where it inhibits progression through the cell cycle prior to fertilization. Fertilization inhibits the MAP kinase cascade and allows entry into the S phase of the cell cycle. Carroll et al. demonstrated that Ca2+ was necessary and sufficient to inhibit MAP kinase and permit DNA replication in sea urchin eggs. MAP kinase was dephosphorylated and its kinase activity was inhibited in a Ca2+-dependent manner, which could be mimicked by the addition of calcium ionophore and blocked by calcium chelators. DNA synthesis could be stimulated by fertilization, treatment with a MAP kinase inhibitor, or treatment with calcium ionophore. Their data suggest that one role for the rise in intracellular calcium following fertilization is to release the brake on mitosis through inhibition of MAP kinase.

Carroll, D.J., Albay, D.T., Hoang, K.M., O'Neill, F.J., Kumano, M., and Foltz, K.R. (2000) The relationship between calcium, mAP kinase, and DNA synthesis in the sea urchin egg at fertilization. Dev. Biol. 217: 179-191. [Abstract]

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