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Activation of mitogen-activated protein kinase during meiotic maturation in mouse oocytes
T Sobajima1, F Aoki, K Kohmoto
1Department of Animal Breeding, Faculty of Agriculture, University of Tokyo, Japan.
Abstract:
Mitogen-activated protein kinase (MAP kinase) plays a role in the cascade of protein kinase activation in cultured cells. To investigate the involvement of MAP kinase in meiotic maturation, we measured MAP kinase activity, using myelin basic protein as a substrate, with histone H1 kinase activity, in mouse oocytes. MAP kinase activity was low 1 h after isolation from follicles (when oocytes lost their germinal vesicle), increased abruptly at 2 h, and remained high until the second metaphase (13 h after isolation from follicles). Histone H1 kinase activity increased gradually from 2 to 7 h after isolation. When immature oocytes were treated with puromycin, MAP kinase activity did not increase after isolation from follicles. In the presence of 3-isobutyl-1-methylxanthine, the treatment of immature oocytes with okadaic acid, a specific inhibitor of protein phosphatase 1 and 2A, induced germinal vesicle breakdown and activation of MAP kinase. These results suggest that MAP kinase is involved in the regulation of meiotic maturation, and that the activation of MAP kinase requires protein synthesis and is inhibited by the protein phosphatase during meiotic maturation in mouse oocytes.
Insights
Mitogen-activated protein kinase (MAP kinase) is crucial for mouse oocyte meiotic maturation. Its activation requires protein synthesis and is regulated by protein phosphatase during this process.
Area of Science:
- Cell Biology
- Developmental Biology
- Molecular Biology
Background:
- Mitogen-activated protein kinase (MAP kinase) is a key component in cellular signaling pathways.
- Understanding MAP kinase's role in oocyte maturation is essential for reproductive biology.
Purpose of the Study:
- To investigate the involvement and regulation of MAP kinase activity during mouse oocyte meiotic maturation.
- To elucidate the factors influencing MAP kinase activation, such as protein synthesis and phosphatase activity.
Main Methods:
- Measurement of MAP kinase activity using myelin basic protein as a substrate.
- Assessment of histone H1 kinase activity in mouse oocytes.
- Inhibition of protein synthesis with puromycin and protein phosphatase with okadaic acid.
Main Results:
- MAP kinase activity increased significantly during meiotic maturation, peaking at the second metaphase.
- Puromycin treatment blocked MAP kinase activation, indicating a requirement for protein synthesis.
- Okadaic acid induced germinal vesicle breakdown and MAP kinase activation, suggesting phosphatase inhibition is involved.
Conclusions:
- MAP kinase plays a critical role in regulating meiotic maturation in mouse oocytes.
- MAP kinase activation during oocyte maturation is dependent on protein synthesis.
- Protein phosphatase activity acts as an inhibitor of MAP kinase activation during this process.