Possible Involvement of Nemo-like Kinase 1 in Xenopus Oocyte Maturation As a Kinase Responsible for Pumilio1, Pumilio2, and CPEB Phosphorylation
Possible Involvement of Nemo-like Kinase 1 in Xenopus Oocyte Maturation As a Kinase Responsible for Pumilio1, Pumilio2, and CPEB Phosphorylation
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DOI：
10.1021/bi2002696
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发表时间：
2011-06-28
期刊：
影响因子：
2.9
通讯作者：
Yamashita, Masakane
中科院分区：
文献类型：
--
作者：
Ota, Ryoma;Kotani, Tomoya;Yamashita, Masakane
丝裂原活化蛋白激酶（MAPK）家族成员在非洲爪蟾卵母细胞成熟过程中起重要作用。Nemo-like kinase（NLK）是一种非典型的MAPK，已知在脊椎动物和无脊椎动物的多种发育过程中发挥作用，但其在配子发生和配子成熟中的作用尚不清楚。在这项研究中，我们生化检查NLK 1在非洲爪蟾卵母细胞成熟。NLK 1在未成熟卵母细胞中表达，其蛋白水平在成熟过程中保持恒定。NLK 1在未成熟的卵母细胞中是无活性的，但在成熟过程中被激活，这取决于Mos蛋白的合成，而不是p42 MAPK的激活。通过注射5 ng mRNA过表达NLK 1，通过其mRNA的翻译激活增强细胞周期蛋白B1蛋白的合成，加速孕酮诱导的卵母细胞成熟，这与Pumilio 1（Pum 1）、Pumilio 2（Pum 2）和细胞质多聚腺苷酸化元件结合蛋白（CPEB）的过早磷酸化一致，CPEB是卵母细胞中储存的mRNA翻译控制的关键调节因子。通过注射50 ng mRNA的较高水平的NLK 1表达诱导Pum 1/Pum 2/CPEB磷酸化、CPEB降解、细胞周期蛋白B1蛋白合成以及在不存在孕酮的情况下的卵母细胞成熟。NLK 1在体外磷酸化Pum 1、Pum 2和CPEB。这些发现提供了第一个证据NLK 1参与非洲爪蟾卵母细胞成熟。我们认为NLK 1作为Mos下游的激酶，催化Pum 1、Pum 2和CPEB的磷酸化，以调节卵母细胞中储存的mRNA（包括细胞周期蛋白B1 mRNA）的翻译。
Members of the mitogen-activated protein kinase (MAPK) family play important roles in Xenopus oocyte maturation. Nemo-like kinase (NLK), an atypical MAPK, is known to function in multiple developmental processes in vertebrates and invertebrates, but its involvement in gametogenesis and gamete maturation is unknown. In this study, we biochemically examined NLK1 during Xenopus oocyte maturation. NLK1 is expressed in immature oocytes, and its protein level remains constant during maturation. NLK1 is inactive in immature oocytes but is activated during maturation, depending on Mos protein synthesis but not on p42 MAPK activation. Overexpression of NLK1 by injection of 5 ng of mRNA accelerates progesterone-induced oocyte maturation by enhancing Cyclin B1 protein synthesis through the translational activation of its mRNA, in accordance with precocious phosphorylation of Pumilio1 (Pum1), Pumilio2 (Pum2), and cytoplasmic polyadenylation element-binding protein (CPEB), key regulators of the translational control of mRNAs stored in oocytes. A higher level of NLK1 expression by injection of 50 ng of mRNA induces Pum1/Pum2/CPEB phosphorylation, CPEB degradation, Cyclin B1 protein synthesis, and oocyte maturation in the absence of progesterone. NLK1 phosphorylates Pum1, Pum2, and CPEB in vitro. These findings provide the first evidence for the involvement of NLK1 in Xenopus oocyte maturation. We suggest that NLK1 acts as a kinase downstream of Mos and catalyzes phosphorylation of Pum1, Pum2, and CPEB to regulate the translation of mRNAs, including Cyclin B1 mRNA, stored in oocytes.