A specific inhibitor of p34(cdc2)/cyclin B suppresses fertilization-induced calcium oscillations in mouse eggs.
Fertilization-induced Ca(2+) oscillations in mouse eggs cease at the time of pronuclear formation when maturation-promoting factor (MPF) is inactivated, but the Ca(2+) oscillations are ceaseless if eggs are arrested at metaphase by colcemid, which maintains the activity of MPF. To determine the possible role of MPF in regulation of cytoplasmic Ca(2+) excitability, roscovitine, a specific inhibitor of p34(cdc2)/cyclin B kinase, was used to inactivate MPF, and its effect on fertilization-induced Ca(2+) oscillations was investigated. Our results showed that roscovitine at >/= 50 microM suppressed fertilization-induced Ca(2+) oscillations in normal and colcemid-treated metaphase II (MII) eggs after the first 1-2 Ca(2+) spikes. Roscovitine inhibition of fertilization-induced Ca(2+) oscillations could be reversed by extensive washing of the eggs. Histone H1 kinase activity in colcemid-treated MII eggs was similarly inhibited by roscovitine, which suggested that the cessation of fertilization-induced Ca(2+) oscillations is due to the inactivation of MPF. Thimerosal-induced Ca(2+) oscillations in Ca(2+)-, Mg(2+)-free medium was also suppressed by roscovitine, suggesting a general inhibitory effect of roscovitine on Ca(2+) oscillations. The inhibition may be achieved by disruption of Ca(2+) release and refilling of the calcium store. Thapsigargin, an inhibitor of the endoplasmic reticulum Ca-ATPase, induced significantly less Ca(2+) release in roscovitine-treated eggs than in the non-drug-treated eggs. Taken together, our results suggest that MPF plays an important role in regulation of the cytoplasmic Ca(2+) excitability in mouse eggs.
Deng
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Department of Zoology & Genetics, Iowa State University, Ames, Iowa 50011-3223, USA. mdeng@ansc1.cag.uconn.edu
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D000818:Animals; D016203:CDC2 Protein Kinase / Q000037:antagonists & inhibitors*; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D019926:Cyclin B / Q000037:antagonists & inhibitors*; D003703:Demecolcine / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D005307:Fertilization in Vitro; D066298:In Vitro Techniques; D008297:Male; D016200:Maturation-Promoting Factor / Q000037:antagonists & inhibitors; D000090204:Mesothelin; D051379:Mice; D008810:Mice, Inbred C57BL; D009865:Oocytes / Q000187:drug effects; D010063:Ovum / Q000187:drug effects*; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases; D011687:Purines / Q000494:pharmacology*; D000077546:Roscovitine; D019284:Thapsigargin / Q000494:pharmacology; D013849:Thimerosal / Q000494:pharmacology
D019926:Cyclin B; D004791:Enzyme Inhibitors; C000715528:Msln protein, mouse; D047428:Protein Kinase Inhibitors; D011687:Purines; D000077546:Roscovitine; D013849:Thimerosal; D019284:Thapsigargin; D011494:Protein Kinases; C102333:histone H1 kinase; D016203:CDC2 Protein Kinase; D016200:Maturation-Promoting Factor; D000252:Calcium-Transporting ATPases; D000090204:Mesothelin; D002118:Calcium; D003703:Demecolcine