Ubiquitin-proteasome pathway modulates mouse oocyte meiotic maturation and fertilization via regulation of MAPK cascade and cyclin B1 degradation.
Degradation of proteins mediated by ubiquitin-proteasome pathway (UPP) plays important roles in the regulation of eukaryotic cell cycle. In this study, the functional roles and regulatory mechanisms of UPP in mouse oocyte meiotic maturation, fertilization, and early embryonic cleavage were studied by drug-treatment, Western blot, antibody microinjection, and confocal microscopy. The meiotic resumption of both cumulus-enclosed oocytes and denuded oocytes was stimulated by two potent, reversible, and cell-permeable proteasome inhibitors, ALLN and MG-132. The metaphase I spindle assembly was prevented, and the distribution of ubiquitin, cyclin B1, and polo-like kinase 1 (Plk1) was also distorted. When UPP was inhibited, mitogen-activated protein kinase (MAPK)/p90rsk phosphorylation was not affected, but the cyclin B1 degradation that occurs during normal metaphase-anaphase transition was not observed. During oocyte activation, the emission of second polar body (PB2) and the pronuclear formation were inhibited by ALLN or MG-132. In oocytes microinjected with ubiquitin antibodies, PB2 emission and pronuclear formation were also inhibited after in vitro fertilization. The expression of cyclin B1 and the phosphorylation of MAPK/p90rsk could still be detected in ALLN or MG-132-treated oocytes even at 8 h after parthenogenetic activation or insemination, which may account for the inhibition of PB2 emission and pronuclear formation. We also for the first time investigated the subcellular localization of ubiquitin protein at different stages of oocyte and early embryo development. Ubiquitin protein was accumulated in the germinal vesicle (GV), the region between the separating homologous chromosomes, the midbody, the pronuclei, and the region between the separating sister chromatids. In conclusion, our results suggest that the UPP plays important roles in oocyte meiosis resumption, spindle assembly, polar body emission, and pronuclear formation, probably by regulating cyclin B1 degradation and MAPK/p90rsk phosphorylation.
State Key Laboratory of Reproductive Biology, Institute of Zoology, Graduate School of the Chinese Academy of Sciences, Beijing 100080, China.
Li-Jun
LJ
Huo
Heng-Yu
HY
Fan
Zhi-Sheng
ZS
Zhong
Da-Yuan
DY
Chen
Heide
H
Schatten
Qing-Yuan
QY
Sun
D000818:Animals; D000906:Antibodies / Q000008:administration & dosage; D018797:Cell Cycle Proteins; D019926:Cyclin B / Q000378:metabolism*; D056744:Cyclin B1; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D005260:Female; D005307:Fertilization in Vitro; D007976:Leupeptins / Q000494:pharmacology; D020935:MAP Kinase Signaling System; D008540:Meiosis / Q000187:drug effects; D051379:Mice; D009865:Oocytes / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D010312:Parthenogenesis; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D013347:Subcellular Fractions / Q000378:metabolism; D025801:Ubiquitin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000097869:Polo-Like Kinase 1
D000906:Antibodies; D018797:Cell Cycle Proteins; D019926:Cyclin B; D056744:Cyclin B1; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D046988:Proteasome Endopeptidase Complex; D061988:Proteasome Inhibitors; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D025801:Ubiquitin; D000097869:Polo-Like Kinase 1; C534700:Ccnb1 protein, mouse; C063261:acetylleucyl-leucyl-norleucinal; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde