Involvement of calcium/calmodulin-dependent protein kinase II (CaMKII) in meiotic maturation and activation of pig oocytes.
Calcium signal is important for the regulation of meiotic cell cycle in oocytes, but its downstream mechanism is not well known. The functional roles of calcium/calmodulin-dependent protein kinase II (CaMKII) in meiotic maturation and activation of pig oocytes were studied by drug treatment, Western blot analysis, kinase activity assay, indirect immunostaining, and confocal microscopy. The results indicated that meiotic resumption of both cumulus-enclosed and denuded oocytes was prevented by CaMKII inhibitor KN-93, Ant-AIP-II, or CaM antagonist W7 in a dose-dependent manner, but only germinal vesicle breakdown (GVBD) of denuded oocytes was inhibited by membrane permeable Ca2+ chelator BAPTA-AM. When the oocytes were treated with KN-93, W7, or BAPTA-AM after GVBD, the first polar body emission was inhibited. A quick elevation of CaMKII activity was detected after electrical activation of mature pig oocytes, which could be prevented by the pretreatment of CaMKII inhibitors. Treatment of oocytes with KN-93 or W7 resulted in the inhibition of pronuclear formation. The possible regulation of CaMKII on maturation promoting factor (MPF), mitogen-activated protein kinase (MAPK), and ribosome S6 protein kinase (p90rsk) during meiotic cell cycles of pig oocytes was also studied. KN-93 and W7 prevented the accumulation of cyclin B and the full phosphorylation of MAPK and p90rsk during meiotic maturation. When CaMKII activity was inhibited during parthenogenetic activation, cyclin B, the regulatory subunit of MPF, failed to be degraded, but MAPK and p90rsk were quickly dephosphorylated and degraded. Confocal microscopy revealed that CaM and CaMKII were localized to the nucleus and the periphery of the GV stage oocytes. Both proteins were concentrated to the condensed chromosomes after GVBD. In oocytes at the meiotic metaphase MI or MII stage, CaM distributed on the whole spindle, but CaMKII was localized only on the spindle poles. After transition into anaphase, both proteins were translocated to the area between separating chromosomes. All these results suggest that CaMKII is a multifunctional regulator of meiotic cell cycle and spindle assembly and that it may exert its effect via regulation of MPF and MAPK/p90rsk activity during the meiotic maturation and activation of pig oocytes.
Fan
Heng-Yu
HY
State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, China.
Huo
Li-Jun
LJ
Meng
Xiao-Qian
XQ
Zhong
Zhi-Sheng
ZS
Hou
Yi
Y
Chen
Da-Yuan
DY
Sun
Qing-Yuan
QY
D000818:Animals; D015153:Blotting, Western; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D002467:Cell Nucleus / Q000502:physiology; D002614:Chelating Agents / Q000494:pharmacology; D002875:Chromosomes / Q000187:drug effects; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D016200:Maturation-Promoting Factor / Q000494:pharmacology; D008540:Meiosis / Q000187:drug effects / Q000502:physiology*; D018613:Microscopy, Confocal; D020928:Mitogen-Activated Protein Kinases / Q000096:biosynthesis; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D010312:Parthenogenesis; D011247:Pregnancy; D013347:Subcellular Fractions / Q000378:metabolism; D013552:Swine; D017388:Zygote Intrafallopian Transfer
D002614:Chelating Agents; D004791:Enzyme Inhibitors; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D016200:Maturation-Promoting Factor; D020928:Mitogen-Activated Protein Kinases