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Inhibition of mos-induced oocyte maturation by protein kinase A
I Daar1, N Yew, G F Vande Woude
1ABL-Basic Research Program, NCI-Frederick Cancer Research and Development Center, Maryland 21702.
Abstract:
The relationship between the mos protooncogene protein and cAMP-dependent protein kinase (PKA) during the maturation of Xenopus oocytes was investigated. Microinjection of the PKA catalytic subunit (PKAc) into Xenopus oocytes inhibited oocyte maturation induced by the mos product but did not markedly affect the autophosphorylation activity of injected mos protein. By contrast, PKAc did not inhibit maturation promoting factor (MPF) activation or germinal vesicle breakdown (GVBD) that was initiated by injecting crude MPF preparations. In addition, inhibiting endogenous PKA activity by microinjecting the PKA regulatory subunit (PKAr) induced oocyte maturation that was dependent upon the presence of the endogenous mos product. Moreover, PKAr potentiated mos protein-induced MPF activation in the absence of progesterone and protein synthesis. These data are consistent with the hypothesis that progesterone-induced release from G2/M is regulated via PKAc and that PKAc negatively regulates a downstream target that is positively regulated by mos.
Insights
cAMP-dependent protein kinase (PKA) negatively regulates mos protooncogene protein activity, controlling Xenopus oocyte maturation. Inhibiting PKA promotes maturation, suggesting PKA is a key regulator in this process.
Area of Science:
- Cellular and Developmental Biology
- Molecular Endocrinology
- Signal Transduction Pathways
Background:
- Oocyte maturation is a critical process in Xenopus reproduction.
- The mos protooncogene protein and cAMP-dependent protein kinase (PKA) are implicated in regulating oocyte maturation.
- Understanding their interplay is crucial for deciphering cell cycle control.
Purpose of the Study:
- To investigate the relationship between the mos protooncogene protein and PKA during Xenopus oocyte maturation.
- To elucidate the role of PKA in mos-mediated oocyte maturation.
- To determine how PKA activity influences maturation promoting factor (MPF) activation and germinal vesicle breakdown (GVBD).
Main Methods:
- Microinjection of PKA subunits (PKAc and PKAr) into Xenopus oocytes.
- Assessment of oocyte maturation, MPF activation, and GVBD.
- Analysis of mos protein autophosphorylation activity.
Main Results:
- Microinjected PKA catalytic subunit (PKAc) inhibited mos-induced oocyte maturation but not mos autophosphorylation.
- PKAc did not inhibit MPF activation or GVBD induced by crude MPF.
- Inhibiting endogenous PKA with PKAr induced maturation dependent on mos and potentiated mos-induced MPF activation.
Conclusions:
- Progesterone-induced G2/M transition is regulated by PKAc.
- PKAc negatively regulates a downstream target that is positively regulated by mos.
- PKA acts as a negative regulator in the mos-driven pathway controlling Xenopus oocyte maturation.