Maintenance of Meiotic Arrest by a Phosphorylated p34cdc2 is Independent of Cyclic Adenosine 3′,5′-Monophosphate
| Autor: | Nava Dekel, Sari Goren |
|---|---|
| Rok vydání: | 1994 |
| Předmět: |
G2 Phase
medicine.medical_specialty IBMX Blotting Western Protein tyrosine phosphatase Biology Dephosphorylation chemistry.chemical_compound 1-Methyl-3-isobutylxanthine Internal medicine CDC2 Protein Kinase Cyclic AMP medicine Animals Phosphorylation Rats Wistar Tyrosine Phosphodiesterase inhibitor Cells Cultured Cell Biology General Medicine Oocyte Rats Cell biology Meiosis medicine.anatomical_structure Endocrinology Reproductive Medicine chemistry Oocytes Female Protein Tyrosine Phosphatases Vanadates |
| Zdroj: | Biology of Reproduction. 51:956-962 |
| ISSN: | 1529-7268 0006-3363 |
| DOI: | 10.1095/biolreprod51.5.956 |
| Popis: | The meiotic division in oocytes is arrested in the G, phase of the cell cycle. Resumption of meiosis, also known as oocyte maturation, entails a G 2 to M transition and is associated with a drop in intraoocyte concentrations of cAMP. Recent studies imply that tyrosine dephosphorylation of p 3 4Cdc2 is a prerequisite for entry into the M-phase of the cell cycle. Our study was designed to test the involvement of protein tyrosine phosphatase (PTPase)-regulated dephosphorylation of p34cdC 2 in resumption of meiosis in rat oocytes and to explore the possible control of this event by the intraoocyte concentrations of cAMP. Isolated rat oocytes undergoing meiotic maturation spontaneously in vitro served as our experimental model. We found that sodium metavanadate, an inhibitor of PTPase, reversibly blocked the spontaneous maturation in vitro of rat oocytes (ED50 = 0.26 mM). We further demonstrated that the vanadate-sensitive event is completed by 2 h after reinitiation of meiosis. Immunoblot analysis using specific antiphosphotyrosine antibodies revealed that vanadate caused accumulation of phosphotyrosine on a 34-kDa protein, also recognized by anti-p34 ° at2 antibodies. The phosphorylated form of p34Cd c2 was also detected in oocytes arrested in the G, phase by the phosphodiesterase inhibitor isobutyl methylxanthine (IBMX). Intraoocyte concentrations of cAMP in vanadateinhibited oocytes were similar to those in oocytes that resumed meiosis spontaneously in vitro and lower than those in oocytes maintained in meiotic arrest by IBMX (0.073 0.08, 0.84 ± 0.09, and 1.42 0.3 fmol/oocyte, respectively). We conclude that a PTPase that regulates the phosphorylation state of p34cdc 2 participates in the control of meiosis in rat oocytes. Furthermore, maintenance of meiotic arrest by a phosphorylated p34cdc 2 that is independent of cAMP suggests that the above-mentioned PTPase activity occurs downstream to the oocyte maturation-associated drop of intracellular concentrations of cAMP. |
| Databáze: | OpenAIRE |
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