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cAMP-Dependent PKA negatively regulates polyadenylation of c-mos mRNA in rat oocytes
Shlomi Lazar1, Dalia Galiani, Nava Dekel
1Department of Biological Regulation, The Weizmann Institute of Science, Rehovot 76100, Israel.
Abstract:
Activation of members of the MAPK family, Erk 1 and 2, in oocytes resuming meiosis is regulated by Mos. The cAMP-dependent PKA-mediated cAMP action that inhibits the resumption of meiosis also prevents MAPK activation. We hypothesized that PKA interferes with the MAPK signaling pathways at the level of Mos. We also assumed that this regulatory cascade may involve p34cdc2. To test our hypothesis we explored the role of PKA and p34cdc2 in regulating Mos expression. Rat oocytes that resume meiosis spontaneously served as our experimental model. We found that meiotically arrested rat oocytes express the c-mos mRNA with no detectable Mos protein. The presence of Mos was initially demonstrated at 6 h after meiosis reinitiation and was associated with its mRNA polyadenylation. (Bu)(2)cAMP inhibited Mos expression as well as c-mos mRNA polyadenylation. Both these cAMP actions were reversed by the highly selective inhibitor of the catalytic subunit of PKA, 4-cyano-3-methylisoquinoline. Polyadenylation of c-mos mRNA was also prevented by roscovitine, which is a potent inhibitor of p34cdc2. Ablation of MAPK activity by two specific MAPK signaling pathway inhibitors, either PD 98059 or U0126, did not interfere with Mos accumulation. Our results suggest that translation of Mos in rat oocytes is negatively regulated by a PKA-mediated cAMP action that inhibits c-mos mRNA polyadenylation and involves suppressed activity of p34cdc2. We also demonstrate that stimulation of Mos synthesis in the rat does not require an active MAPK.
Insights
Protein kinase A (PKA) and p34cdc2 regulate Mos expression in oocytes. PKA-mediated cAMP inhibits Mos translation by preventing c-mos mRNA polyadenylation, a process involving p34cdc2.
Area of Science:
- Cellular biology
- Molecular biology
- Reproductive biology
Background:
- Meiosis resumption in oocytes is tightly regulated by signaling pathways.
- Mitogen-activated protein kinase (MAPK) family members, Erk 1 and 2, play crucial roles in this process.
- cAMP-dependent protein kinase A (PKA) inhibits meiosis resumption and MAPK activation.
Purpose of the Study:
- To investigate the role of PKA and p34cdc2 in regulating Mos expression during oocyte meiosis.
- To determine if PKA interferes with MAPK signaling at the level of Mos.
- To elucidate the regulatory cascade involving PKA, p34cdc2, and Mos.
Main Methods:
- Utilized spontaneously meiotically arrested rat oocytes as an experimental model.
- Assessed c-mos mRNA and Mos protein levels.
- Employed inhibitors of PKA (4-cyano-3-methylisoquinoline), p34cdc2 (roscovitine), and MAPK (PD 98059, U0126).
- Investigated the effect of cAMP and its analogs on Mos expression and mRNA polyadenylation.
Main Results:
- Meiotically arrested oocytes expressed c-mos mRNA but not Mos protein.
- Mos protein appeared 6 hours after meiosis reinitiation, coinciding with c-mos mRNA polyadenylation.
- cAMP inhibited Mos expression and c-mos mRNA polyadenylation, effects reversed by a PKA inhibitor.
- p34cdc2 inhibition also prevented c-mos mRNA polyadenylation.
- MAPK inhibitors did not affect Mos accumulation.
Conclusions:
- Mos translation in rat oocytes is negatively regulated by PKA-mediated cAMP action.
- This regulation involves inhibition of c-mos mRNA polyadenylation and suppressed p34cdc2 activity.
- Active MAPK signaling is not required for Mos synthesis stimulation in rat oocytes.
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