title: Effect of enucleation on inactivation of cytostatic factor activity in matured rat oocytes.
abstract: In mammals, matured oocytes are arrested at the MII stage until fertilization, which is regulated by cytostaticfactor (CSF) activity. Maturation-promoting factor (MPF) and the mitogen-activated protein kinase (MAPK) pathway are known as candidates for CSF. Despite of the results that nuclear and perinuclear materials were dispensable for activation of MPF and MAPK in other species, our previous study in rats demonstrated that MPF activity was rapidly decreased after enucleation. We showed here for the first time that nuclear and perinuclear materials were indispensable for CSF activity in matured rat oocytes. In both cytoplasm-removed and enucleated oocytes, high activity of p34(cdc2) kinase was observed immediately after manipulation, but the activity of enucleated oocytes was dramatically reduced within 1 h. Cyclin B level was also decreased, corresponding with inactivation of p34(cdc2) kinase. In enucleated oocytes, the Mos level was dramatically decreased, and both MEK and MAPK dephosphorylation were also induced. A combined treatment with a proteasome inhibitor, MG132, and a protein phosphatase inhibitor, okadaic acid, dramatically improved both levels of p-MAPK and cyclin B in these enucleated oocytes. These data suggest that nuclear and perinuclear materials of matured rat oocytes suppress proteasome and protein phosphatase activation, which is indispensable for stability of CSF.
authors.affiliation: Section of Molecular Genetics, Center for Brain Experiment, National Institute for Physiological Sciences, Okazaki, Aichi, Japan. jito@vasci.umass.edu
authors.forename: Junya
authors.initials: J
authors.lastname: Ito
authors.forename: Megumi
authors.initials: M
authors.lastname: Kato
authors.forename: Shinichi
authors.initials: S
authors.lastname: Hochi
authors.forename: Masumi
authors.initials: M
authors.lastname: Hirabayashi
mesh_terms: D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D002467:Cell Nucleus / Q000502:physiology*; D019926:Cyclin B / Q000378:metabolism; D003593:Cytoplasm / Q000502:physiology*; D004789:Enzyme Activation; D005260:Female; D005326:Fetal Proteins / Q000378:metabolism*; D016258:Genes, mos / Q000502:physiology; D066298:In Vitro Techniques; D007976:Leupeptins / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D019319:Okadaic Acid / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D051381:Rats
chemical_list: D019926:Cyclin B; D005326:Fetal Proteins; D007976:Leupeptins; D061988:Proteasome Inhibitors; C084728:cytostatic factor protein, rat; D019319:Okadaic Acid; D016203:CDC2 Protein Kinase; D010749:Phosphoprotein Phosphatases; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde