Protease triggers dephosphorylation of cdc2 kinase during starfish oocyte maturation

Sawada, Hitoshi; Yokoyama, Kaoru; Morinaga, Chikako; Yokosawa, Hideyoshi; Sawada, Minoru

doi:10.1080/15216549700201951

Cited by 5 publications

(3 citation statements)

References 15 publications

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“…In toad and starfish oocytes, inhibition of proteasomal proteolytic activity prevented GV breakdown (GVBD) [19,20]. Inhibition of GVBD was also observed with microinjection of antiproteasome ␣ subunit antibodies into the starfish oocytes [21][22][23][24].…”

Section: Introductionmentioning

confidence: 72%

Regulation of Ubiquitin-Proteasome Pathway on Pig Oocyte Meiotic Maturation and Fertilization1

Huo

Fan

Liang

et al. 2004

Biology of Reproduction

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Degradation of proteins mediated by the ubiquitin-proteasome pathway (UPP) plays essential roles in the eukaryotic cell cycle. The main aim of the present study was to analyze the functional roles and regulatory mechanisms of the UPP in pig oocyte meiotic maturation, activation, and early embryo mitosis by drug treatment, Western blot analysis, and confocal microscopy. By using the hypoxanthine-maintained meiotic arrest model, we showed that the meiotic resumption of both cumulus-enclosed oocytes and denuded oocytes was stimulated in a dose- and time-dependent manner by two potent and cell-permeable proteasome inhibitors. Both the mitogen-activated protein kinase (MAPK) kinase inhibitor U0126 and the maturation-promoting factor inhibitor roscovitine overcame the stimulation of germinal vesicle breakdown induced by proteasome inhibitors. The phosphorylation of MAPK and p90rsk and the expression of cyclin B1 increased in a dose- and time-dependent manner when treated with proteasome inhibitors during oocyte in vitro-maturation culture. Both U0126 and roscovitine inhibited the phosphorylation of MAPK and p90rsk, and the synthesis of cyclin B1 stimulated by proteasome inhibitors. When matured oocytes were pretreated with proteasome inhibitors and then fertilized or artificially activated, the second polar body emission and the pronuclear formation were inhibited, and the dephosphorylation of MAPK and p90rsk as well as the degradation of cyclin B1 that should occur after oocyte activation were also inhibited. We also investigated, to our knowledge for the first time, the subcellular localization of 20S proteasome alpha subunits at different stages of oocyte and early embryo development. The 20S proteasome alpha subunits were accumulated in the germinal vesicle, around the condensed chromosomes at prometaphase, with spindle at metaphase I and II, the region between the separating chromosomes, and especially the midbody at anaphase I and telophase I, the pronucleus, and the nucleus in early embryonic cells. In conclusion, our results suggest that the UPP is important at multiple steps of pig oocyte meiosis, fertilization, and early embryonic mitosis and that it may play its roles by regulating cyclin B1 degradation and MAPK/p90rsk phosphorylation.

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Section: Introductionmentioning

confidence: 72%

Regulation of Ubiquitin-Proteasome Pathway on Pig Oocyte Meiotic Maturation and Fertilization1

Huo

Fan

Liang

et al. 2004

Biology of Reproduction

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“…In 2-, 3-, and 4-cell embryos, the localization of ubiquitin protein could be detected in the nucleus (F-L). Murray et al, 1989;Sawada et al, 1997;Suzumori et al, 2003;Takagi Sawada et al, 1997;Takahashi et al, 1994;Tokumoto et al, 1997), our understanding of the roles and the regulatory mechanisms of UPP in mammalian oocyte meiosis, fertilization and early embryonic mitosis was limited.…”

Section: Discussionmentioning

confidence: 99%

Ubiquitin–proteasome pathway modulates mouse oocyte meiotic maturation and fertilization via regulation of MAPK cascade and cyclin B1 degradation

Huo

Fan

Zhong

et al. 2004

Mechanisms of Development

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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.

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“…CPEB is degraded coincident with GVBD, which occurs ϳ4 h into the ϳ6-h maturation process. To avoid perturbing early events in maturation that may require proteasome activity (Sawada et al, 1997), we attempted to block CPEB degradation by injecting inhibitors into oocytes in which maturation had been initiated but had not yet advanced to GVBD. We found that non-GVBD oocytes taken from a batch of maturing oocytes where 50% had achieved GVBD (GVBD 50 ) were suitable for these studies.…”

Section: Cpeb Is Degraded By the Proteasome Pathwaymentioning

confidence: 99%

CPEB Degradation during Xenopus Oocyte Maturation Requires a PEST Domain and the 26S Proteasome

Reverte

Ahearn

Hake

2001

Developmental Biology

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Cytoplasmic poly(A) elongation is widely utilized during the early development of many organisms as a mechanism for translational activation. Targeting of mRNAs for this mechanism requires the presence of a U-rich element, the cytoplasmic polyadenylation element (CPE), and its binding protein, CPEB. Blocking cytoplasmic polyadenylation by interfering with the CPE or CPEB prevents the translational activation of mRNAs that are crucial for oocyte maturation. The CPE sequence and CPEB are also important for translational repression of mRNAs stored in the Xenopus oocyte during oogenesis. To understand the contribution of protein metabolism to these two roles for CPEB, we have examined the mechanisms influencing the expression of CPEB during oogenesis and oocyte maturation. Through a comparison of CPEB mRNA levels, protein synthesis, and accumulation, we find that CPEB is synthesized during oogenesis and stockpiled in the oocyte. Minimal synthesis of CPEB, <3.6%, occurs during oocyte maturation. In late oocyte maturation, 75% of CPEB is degraded coincident with germinal vesicle breakdown. Using proteasome and ubiquitination inhibitors, we demonstrate that CPEB degradation occurs via the proteasome pathway, most likely through ubiquitin-conjugated intermediates. In addition, we demonstrate that degradation requires a 14 amino acid PEST domain.

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Protease triggers dephosphorylation of cdc2 kinase during starfish oocyte maturation

Cited by 5 publications

References 15 publications

Regulation of Ubiquitin-Proteasome Pathway on Pig Oocyte Meiotic Maturation and Fertilization1

Regulation of Ubiquitin-Proteasome Pathway on Pig Oocyte Meiotic Maturation and Fertilization1

Ubiquitin–proteasome pathway modulates mouse oocyte meiotic maturation and fertilization via regulation of MAPK cascade and cyclin B1 degradation

CPEB Degradation during Xenopus Oocyte Maturation Requires a PEST Domain and the 26S Proteasome

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