Mitogen-activated protein kinase kinase inhibitor suppresses cyclin B1 synthesis and reactivation of p34cdc2 kinase, which improves pronuclear formation rate in matured porcine oocytes activated by Ca2+ ionophore.
To investigate the role of mitogen-activated protein (MAP) kinase kinase (MEK)/MAP kinase cascade on p34cdc2 kinase activity and cyclin B1 levels during parthenogenetic activation of porcine oocytes, MEK activity, MAP kinase activity, p34cdc2 kinase activity, and cyclin B1 levels were assayed in mature porcine oocytes after treatment with different concentrations of Ca2+ ionophore. A high concentration of Ca2+ ionophore (50 microM) rapidly reduced MEK activity in oocytes for up to 8 h of culture. MEK activity in the 10-microM treatment group was significantly higher. The low concentration treatment transiently decreased p34cdc2 kinase activity but did not affect MAP kinase activity and ultimately induced reactivation of p34cdc2 kinase via the synthesis of cyclin B1. On the other hand, treatments of a high concentration of Ca2+ ionophore or a low concentration of Ca2+ ionophore plus MEK inhibitor, U0126, linearly decreased MAP kinase activity following the decrease of p34cdc2 kinase activity; most of these oocytes formed pronuclei. These results suggest that decreasing MAP kinase activity is essential to maintaining low p34cdc2 kinase activity resulting from the degradation of cyclin B via a Ca(2+)-dependent pathway; lower activities of both MAP kinase and p34cdc2 kinase induce normal meiotic completion and pronuclear formation of parthenogenetically activated porcine oocytes.
Ito
Junya
J
Laboratory of Animal Reproduction, Graduate School of Biosphere Sciences, Hiroshima University, Higashi-Hiroshima, 739-8528, Japan.
Shimada
Masayuki
M
Terada
Takato
T
D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002467:Cell Nucleus / Q000502:physiology; D019926:Cyclin B / Q000378:metabolism*; D056744:Cyclin B1; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D007476:Ionophores / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D016200:Maturation-Promoting Factor / Q000378:metabolism; D008540:Meiosis / Q000502:physiology; D009570:Nitriles / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects / Q000201:enzymology*; D010312:Parthenogenesis / Q000502:physiology; D013552:Swine; D000095043:Cyclin-Dependent Kinase-Activating Kinase
D002070:Butadienes; D019926:Cyclin B; D056744:Cyclin B1; D004791:Enzyme Inhibitors; D007476:Ionophores; D009570:Nitriles; C113580:U 0126; D018844:Cyclin-Dependent Kinases; D016200:Maturation-Promoting Factor; D002118:Calcium; D000095043:Cyclin-Dependent Kinase-Activating Kinase