Hormone-induced cortical maturation ensures the slow block to polyspermy and does not couple with meiotic maturation in starfish
Hormone-induced cortical maturation ensures the slow block to polyspermy and does not couple with meiotic maturation in starfish
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DOI：
10.1016/j.ydbio.2008.03.029
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发表时间：
2008-06-01
影响因子：
2.7
通讯作者：
Chiba, Kazuyoshi
中科院分区：
文献类型：
--
作者：
Hirohashi, Noritaka;Harada, Kaori;Chiba, Kazuyoshi
海星卵母细胞的减数分裂过程被一种称为1-甲基腺嘌呤(1-Meade)的成熟诱导激素重新启动。除了减数分裂成熟外，1-Meade还诱导皮质成熟，皮质颗粒在单个精子融合后有能力排出，这导致受精膜的形成。我们发现，亚阈值浓度的1-MEADE可以诱导皮质成熟，而不会导致生发泡破裂(GVBD)。在皮质成熟过程中，钙库对IP3的敏感性增加，减数分裂成熟过程中也是如此。当只在卵母细胞的一个半球上用1-Meade暴露时，皮质区的IP3敏感性仅在暴露的半球增加，这表明参与皮质成熟的信号和成分不容易在细胞质中扩散。尽管LY294002是磷脂酰肌醇-3激酶的特异性抑制剂，但它同时阻止了GVBD和皮质成熟，而CDC2激酶抑制剂罗斯科维汀并不阻止皮质成熟。通过注射Akt磷酸化和膜募集的竞争对手来抑制Akt的激活也阻止了皮质的成熟。这些结果表明，导致Akt激活的信号通路在皮质成熟和减数分裂成熟中是普遍存在的，而CDc2激活不是皮质成熟所必需的。(C)2008 Elsevier Inc.保留所有权利。
Meiotic progression in starfish oocytes is reinitiated by a maturation-inducing hormone called 1-methyladenine (1-MeAde). In addition to meiotic maturation, 1-MeAde induces cortical maturation in which cortical granules become competent to discharge in response to fusion of a single sperm, which results in the formation of the fertilization envelope. We found that subthreshold concentrations of 1-MeAde induce cortical maturation without germinal vesicle breakdown (GVBD). During cortical maturation, the IP3 sensitivity of calcium stores was increased as well as during meiotic maturation. When oocytes were exposed with 1-MeAde only on a hemisphere of oocytes, the IP3 sensitivity of the cortical region was increased only in the exposed hemisphere, suggesting that signals and components involved in cortical maturation do not readily spread in the cytoplasm. Although a specific inhibitor of phosphatidylinositol-3 kinase, LY294002 blocked both GVBD and cortical maturation, a Cdc2 kinase inhibitor, roscovitine did not block cortical maturation. Inhibition of Akt activation by injecting the competitors for Akt phosphorylation and membrane recruitment also blocked cortical maturation. These results suggest that the signaling pathway leading to Akt activation is common in cortical maturation and meiotic maturation, and Cdc2 activation was not required for cortical maturation. (C) 2008 Elsevier Inc. All rights reserved.