The Polo-like Kinase Plx1 Is Required for Activation of the Phosphatase Cdc25C and Cyclin B-Cdc2 in Xenopus Oocytes
AUTOR(ES)
Qian, Yue-Wei
FONTE
The American Society for Cell Biology
RESUMO
In the Xenopus oocyte system mitogen treatment triggers the G2/M transition by transiently inhibiting the cAMP-dependent protein kinase (PKA); subsequently, other signal transduction pathways are activated, including the mitogen-activated protein kinase (MAPK) and polo-like kinase pathways. To study the interactions between these pathways, we have utilized a cell-free oocyte extract that carries out the signaling events of oocyte maturation after addition of the heat-stable inhibitor of PKA, PKI. PKI stimulated the synthesis of Mos and activation of both the MAPK pathway and the Plx1/Cdc25C/cyclin B-Cdc2 pathway. Activation of the MAPK pathway alone by glutathione S-transferase (GST)-Mos did not lead to activation of Plx1 or cyclin B-Cdc2. Inhibition of the MAPK pathway in the extract by the MEK1 inhibitor U0126 delayed, but did not prevent, activation of the Plx1 pathway, and inhibition of Mos synthesis by cycloheximide had a similar effect, suggesting that MAPK activation is the only relevant function of Mos. Immunodepletion of Plx1 completely inhibited activation of Cdc25C and cyclin B-Cdc2 by PKI, indicating that Plx1 is necessary for Cdc25C activation. In extracts containing fully activated Plx1 and Cdc25C, inhibition of cyclin B-Cdc2 by p21Cip1 had no significant effect on either the phosphorylation of Cdc25C or the activity of Plx1. These results demonstrate that maintenance of Plx1 and Cdc25C activity during mitosis does not require cyclin B-Cdc2 activity.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=37341Documentos Relacionados
- Activated Polo-Like Kinase Plx1 Is Required at Multiple Points during Mitosis in Xenopus laevis
- Xenopus polo-like kinase Plx1 regulates XErp1, a novel inhibitor of APC/C activity
- Mitotic Effects of a Constitutively Active Mutant of the Xenopus Polo-Like Kinase Plx1
- The Polo-like kinase Plx1 interacts with and inhibits Myt1 after fertilization of Xenopus eggs
- Mitogen-activated protein kinase activation down-regulates a mechanism that inactivates cyclin B-cdc2 kinase in G2-arrested oocytes.