Type-I phosphoinositide 3-kinases (PI3Ks) were characterized as a group of intracellular signalling proteins expressing both protein and lipid kinase activities. Recent studies implicate PI3Ks as mediators of oocyte maturation, but the molecular mechanisms are poorly defined. Here we used the Xenopus oocyte expression system as a model to investigate a possible contribution of the γ-isoform of PI3K (PI3Kγ) in the different pathways leading to cell-cycle progression by monitoring the time course of germinal vesicle breakdown (GVBD). Expression of a constitutive active PI3Kγ (PI3Kγ-CAAX) induced GVBD and increased the levels of phosphorylated Akt/protein kinase B and mitogen-activated protein kinase (MAPK). Furthermore, PI3Kγ-CAAX accelerated progesterone-induced GVBD, but had no effect on GVBD induced by insulin. The effects of PI3Kγ-CAAX could be suppressed by pre-incubation of the oocytes with LY294002, PD98059 or roscovitine, inhibitors of PI3K, MEK (MAPK/extracellular-signal-regulated protein kinase kinase) and cdc2/cyclin B kinase, respectively. Mutants of PI3Kγ-CAAX, in which either lipid kinase or both lipid and protein kinase activities were altered or eliminated, did not induce significant GVBD. Our data demonstrate that expression of PI3Kγ in Xenopus oocytes accelerates their progesterone-induced maturation and that lipid kinase activity is required to induce this effect.
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December 2001
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Research Article|
December 10 2001
Phosphoinositide 3-kinase-γ induces Xenopus oocyte maturation via lipid kinase activity
Solveig HEHL;
Solveig HEHL
∗Molecular and Cellular Biophysics Research Unit, Medical Faculty of the Friedrich Schiller University Jena, Drackendorfer St. 1, D-07747 Jena, Germany
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Borislav STOYANOV;
Borislav STOYANOV
†Molecular Cell Biology Research Unit, Medical Faculty of the Friedrich Schiller University Jena, Drackendorfer St. 1, D-07747 Jena, Germany
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Wolf OEHRL;
Wolf OEHRL
†Molecular Cell Biology Research Unit, Medical Faculty of the Friedrich Schiller University Jena, Drackendorfer St. 1, D-07747 Jena, Germany
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Roland SCHÖNHERR;
Roland SCHÖNHERR
∗Molecular and Cellular Biophysics Research Unit, Medical Faculty of the Friedrich Schiller University Jena, Drackendorfer St. 1, D-07747 Jena, Germany
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Reinhard WETZKER;
Reinhard WETZKER
†Molecular Cell Biology Research Unit, Medical Faculty of the Friedrich Schiller University Jena, Drackendorfer St. 1, D-07747 Jena, Germany
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Stefan H. HEINEMANN
Stefan H. HEINEMANN
1
∗Molecular and Cellular Biophysics Research Unit, Medical Faculty of the Friedrich Schiller University Jena, Drackendorfer St. 1, D-07747 Jena, Germany
1To whom correspondence should be addressed (e-mail Stefan.H.Heinemann@uni-jena.de).
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Publisher: Portland Press Ltd
Received:
June 26 2001
Revision Received:
September 05 2001
Accepted:
October 09 2001
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London ©2001
2001
Biochem J (2001) 360 (3): 691–698.
Article history
Received:
June 26 2001
Revision Received:
September 05 2001
Accepted:
October 09 2001
Citation
Solveig HEHL, Borislav STOYANOV, Wolf OEHRL, Roland SCHÖNHERR, Reinhard WETZKER, Stefan H. HEINEMANN; Phosphoinositide 3-kinase-γ induces Xenopus oocyte maturation via lipid kinase activity. Biochem J 15 December 2001; 360 (3): 691–698. doi: https://doi.org/10.1042/bj3600691
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