Protein phosphatase-1 is involved in Xenopus oocyte maturation

Huchon, Denise; Ozon, René; Demaille, Jacques

doi:10.1038/294358a0

Cited by 88 publications

(49 citation statements)

References 13 publications

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“…Margolis and co-workers have reported that PP1 is responsible for dephosphorylating Ser287 of Cdc25 (Margolis et al, 2003). This result is consistent with a previous report indicating that injection of Xenopus oocytes with the PP1 inhibitor-1 (I-1) impedes Cdc2 activation and oocyte maturation (Huchon et al, 1981). Cdc25 activation would therefore depend on Ser287 dephosphorylation by PP1 but also on several activatory phosphorylations by Cdc2 and Plx1 at other sites that are negatively regulated by an unidentified okadaic acid-sensitive phosphatase.…”

Section: Introductionsupporting

confidence: 81%

Differential regulation of Cdc2 and Aurora-A in Xenopus oocytes: a crucial role of phosphatase 2A

Maton

Lorca

Girault

et al. 2005

Journal of Cell Science

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The success of cell division relies on the activation of its master regulator Cdc2-cyclin B, and many other kinases controlling cellular organization, such as Aurora-A. Most of these kinase activities are regulated by phosphorylation. Despite numerous studies showing that okadaic acidsensitive phosphatases regulate both Cdc2 and Aurora-A activation, their identity has not yet been established in Xenopus oocytes and the importance of their regulation has not been evaluated. Using an oocyte cell-free system, we demonstrate that PP2A depletion is sufficient to lead to Cdc2 activation, whereas Aurora-A activation depends on Cdc2 activity. The activity level of PP1 does not affect Cdc2 kinase activation promoted by PP2A removal. PP1 inhibition is also not sufficient to lead to Aurora-A activation in the absence of active Cdc2. We therefore conclude that in Xenopus oocytes, PP2A is the key phosphatase that negatively regulates Cdc2 activation. Once this negative regulator is removed, endogenous kinases are able to turn on the activator Cdc2 system without any additional stimulation. In contrast, Aurora-A activation is indirectly controlled by Cdc2 activity independently of either PP2A or PP1. This strongly suggests that in Xenopus oocytes, Aurora-A activation is mainly controlled by the specific stimulation of kinases under the control of Cdc2 and not by downregulation of phosphatase.

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Section: Introductionsupporting

confidence: 81%

Differential regulation of Cdc2 and Aurora-A in Xenopus oocytes: a crucial role of phosphatase 2A

Maton

Lorca

Girault

et al. 2005

Journal of Cell Science

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“…Therefore it seems that in the mouse the CaM antagonist W7 inhibits oocyte maturation at the G2-to Mphase border and the first cleavage at the G1-to S-phase transition. In murine (Kaplan et al, 1982;Bornslaeger et al, 1984) and Xenopus oocytes (Cartaud et al, 1980;Wasserman and Smith, 1981) as in somatic tissues (Means et al, 1982) (Huchon et al, 1981;Foulkes and Maller, 1982;Rime et al, 1990). In contrast to the findings in the mouse, W7 at concentrations up to 200 fl M had no effect on pig oocyte maturation in vitro (table IV).…”

Section: Gel Electrophoresismentioning

confidence: 45%

Effects of protein kinase inhibitors on pig oocyte maturation in vitro

Jung

Lee²,

Moor³

1992

Reprod. Nutr. Dev.

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“…In a recent report, Margolis et al (Margolis et al, 2003) showed that Cdc25C, which is phosphorylated on Ser287 in Xenopus prophase oocytes, is dephosphorylated by type 1 phosphatase (PP1) at GVBD. Since the PP1 inhibitor I prevents meiotic maturation (Huchon et al, 1981), PP1 could participate to the regulation of the MPF autoamplification loop by catalyzing the removal of the inhibitory Ser287 phosphate, and could therefore be involved in the regulation of Cdc25 during oogenesis.…”

Section: Discussionmentioning

confidence: 99%

Polo-like kinase confers MPF autoamplification competence to growingXenopusoocytes

et al. 2004

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During oogenesis, the Xenopus oocyte is blocked in prophase of meiosis I. It becomes competent to resume meiosis in response to progesterone at the end of its growing period (stage VI of oogenesis). Stage IV oocytes contain a store of inactive pre-MPF (Tyr15-phosphorylated Cdc2 bound to cyclin B2); the Cdc25 phosphatase that catalyzes Tyr15 dephosphorylation of Cdc2 is also present. However, the positive feedback loop that allows MPF autoamplification is not functional at this stage of oocyte growth. We report that when cyclin B is overexpressed in stage IV oocytes, MPF autoamplification does not occur and the newly formed cyclin B-Cdc2 complexes are inactivated by Tyr15 phosphorylation, indicating that Myt1 kinase remains active and that Cdc25 is prevented to be activated. Plx1 kinase (or polo-like kinase), which is required for Cdc25 activation and MPF autoamplification in full grown oocytes is not expressed at the protein level in small stage IV oocytes. In order to determine if Plx1 could be the missing regulator that prevents MPF autoamplification, polo kinase was overexpressed in stage IV oocytes. Under these conditions, the MPF-positive feedback loop was restored. Moreover, we show that acquisition of autoamplification competence does not require the Mos/MAPK pathway.

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Protein phosphatase-1 is involved in Xenopus oocyte maturation

Cited by 88 publications

References 13 publications

Differential regulation of Cdc2 and Aurora-A in Xenopus oocytes: a crucial role of phosphatase 2A

Differential regulation of Cdc2 and Aurora-A in Xenopus oocytes: a crucial role of phosphatase 2A

Effects of protein kinase inhibitors on pig oocyte maturation in vitro

Polo-like kinase confers MPF autoamplification competence to growingXenopusoocytes

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