Protein kinase B/Akt induces resumption of meiosis in Xenopus oocytes
Protein kinase B/Akt induces resumption of meiosis in Xenopus oocytes
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DOI：
10.1074/jbc.273.30.18705
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发表时间：
1998-07-24
影响因子：
4.8
通讯作者：
Conti, M
中科院分区：
文献类型：
--
作者：
Andersen, CB;Roth, RA;Conti, M
蛋白激酶B/Akt的活化被认为是调节细胞生长和分化的磷酸肌醇3-激酶途径中的关键步骤。由于胰岛素样生长因子1刺激非洲爪蟾卵母细胞减数分裂的恢复，通过磷酸肌醇3-激酶激活，我们调查了Akt参与这一过程。注射编码非洲爪蟾卵母细胞中的组成型活性Akt的mRNA诱导了与孕酮或胰岛素治疗相同程度的生殖囊泡破裂（GVBD）。注射编码野生型Akt激酶的mRNA在刺激GVBD方面效果较差，而在催化结构域中具有消除激酶活性的赖氨酸突变的Akt没有效果。缺乏膜靶向序列的突变体Akt尽管具有高水平的表达和活性，但不诱导GVBD。如先前关于胰岛素所报道的，通过将卵母细胞与西洛酰胺孵育来防止Akt诱导GVBD，对3型磷酸二酯酶（PDE 8）具有特异性的抑制剂，表明PDE的活性是Akt作用所必需的。活性PDE蛋白的表达证实了卵母细胞中PDE活性的增加足以诱导减数分裂恢复。此外，组成型活性Akt引起内源性PDE活性的S倍增加。这些数据表明，Akt是在控制非洲爪蟾卵母细胞减数分裂的恢复的途径和PDE 3的活性的调节是一个步骤远的激酶活化。
The activation of protein kinase B/Akt is thought to be a critical step in the phosphoinositide 3-kinase pathway that regulates cell growth and differentiation. Because insulin-like growth factor 1 stimulates the resumption of meiosis in Xenopus laevis oocytes via phosphoinositide 3-kinase activation, we investigated the Akt involvement in this process. Injection of mRNA coding for a constitutively active Akt in Xenopus oocytes induced germinal vesicle breakdown (GVBD) to the same extent as progesterone or insulin treatment. Injection of mRNA coding for the wild type Akt kinase was less effective in stimulating GVBD, whereas Akt bearing a lysine mutation in the catalytic domain that abolishes the kinase activity had no effect, A mutant Akt lacking a membrane-targeting sequence did not induce GVBD, despite high levels of expression and activity, As previously reported for insulin, induction of GVBD by Akt was prevented by incubating the oocytes with cilostamide, an inhibitor specific for the type 3 phosphodiesterase (PDE8), suggesting that the activity of a PDE is required for Akt action. That an increase in PDE activity in the oocyte is sufficient to induce meiotic resumption was demonstrated by expression of an active PDE protein. In addition, the constitutively active Akt caused a S-fold increase in the activity of the endogenous PDE. These data demonstrate that Akt is in the pathway controlling resumption of meiosis in the Xenopus oocyte and that regulation of the activity of a PDE3 is a step distal to the kinase activation.