MAPK interacts with XGef and is required for CPEB activation during meiosis in Xenopus oocytes
MAPK interacts with XGef and is required for CPEB activation during meiosis in Xenopus oocytes
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DOI：
10.1242/jcs.03416
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发表时间：
2007-03-15
影响因子：
4
通讯作者：
Hake, Laura E.
中科院分区：
文献类型：
--
作者：
Keady, Brian T.;Kuo, Peiwen;Hake, Laura E.
非洲爪蟾卵母细胞和所有其他研究的卵母细胞的减数分裂进程依赖于多聚腺苷酸化诱导的储存的母体mRNA的翻译。在减数分裂恢复的早期，CPE结合蛋白（CPEB）的磷酸化是多聚腺苷酸化诱导的编码细胞周期调节因子的mRNA翻译所必需的。非洲爪蟾GEF（XGEF），Rho家族的鸟嘌呤交换因子，影响CPEB的活化磷酸化。XGef的交换缺陷版本没有，因此暗示Rho家族GTdR在早期减数分裂中的功能。我们在此发现，艰难梭菌毒素B，一种Rho家族GT3抑制剂，不会损害早期CPEB磷酸化或进展为Germinal囊泡破裂，表明XGef不会通过激活毒素B敏感性GT3来影响这些事件。使用丝裂原活化蛋白激酶（MAPK）抑制剂U0126和Aurora激酶A和Aurora激酶B抑制剂ZM 447439，我们发现MAPK是CPEB磷酸化所必需的，而Aurora激酶不是。此外，我们没有检测到活跃的极光激酶A在早期减数分裂。相比之下，我们观察到一个早期的，短暂的激活MAPK，独立的Mos蛋白的表达。MAPK直接磷酸化CPEB的四个残基（T22、T164、S184、S248），但不磷酸化激活CPEB功能的关键残基S174。值得注意的是，XGef免疫沉淀物含有MAPK，并且该复合物可以磷酸化CPEB。MAPK可能通过一种尚未鉴定的激酶引发CPEB对S174的磷酸化，或者可能激活这种激酶。
Meiotic progression in Xenopus oocytes, and all other oocytes investigated, is dependent on polyadenylation-induced translation of stockpiled maternal mRNAs. Early during meiotic resumption, phosphorylation of CPE-binding protein (CPEB) is required for polyadenylation-induced translation of mRNAs encoding cell cycle regulators. Xenopus Gef (XGef), a Rho-family guanine-exchange factor, influences the activating phosphorylation of CPEB. An exchange-deficient version of XGef does not, therefore implicating Rho-family GTPase function in early meiosis. We show here that Clostridium difficile Toxin B, a Rho-family GTPase inhibitor, does not impair early CPEB phosphorylation or progression to germinal vesicle breakdown, indicating that XGef does not influence these events through activation of a Toxin-B-sensitive GTPase. Using the inhibitors U0126 for mitogen-activated protein kinase (MAPK), and ZM447439 for Aurora kinase A and Aurora kinase B, we found that MAPK is required for phosphorylation of CPEB, whereas Aurora kinases are not. Furthermore, we do not detect active Aurora kinase A in early meiosis. By contrast, we observe an early, transient activation of MAPK, independent of Mos protein expression. MAPK directly phosphorylates CPEB on four residues (T22, T164, S184, S248), but not on S174, a key residue for activating CPEB function. Notably, XGef immunoprecipitates contain MAPK, and this complex can phosphorylate CPEB. MAPK may prime CPEB for phosphorylation on S174 by an as-yet-unidentified kinase or may activate this kinase.