Molecular cloning and characterization of a novel member of the MAP kinase superfamily
Molecular cloning and characterization of a novel member of the MAP kinase superfamily
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DOI：
10.1046/j.1365-2443.1999.00261.x
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发表时间：
1999-05-01
期刊：
影响因子：
2.1
通讯作者：
Nishida, E
中科院分区：
文献类型：
--
作者：
Miyata, Y;Akashi, M;Nishida, E
背景：MAP激酶超家族的成员在多种信号转导途径中发挥重要作用，并且已经确定了几个成员。然而，哺乳动物系统中细胞反应的多样性和复杂性可能意味着MAP激酶超家族中迄今未被识别的成员的存在。结果：我们报道了MAP激酶超家族新成员的分子克隆和特征。我们分离了全长的小鼠和人类cdna，编码一种新型蛋白激酶的完整开放阅读框，称为MOK。MOK由419个氨基酸（人）和420个氨基酸（小鼠）组成，计算分子量为48kDa。MOK包含所有丝氨酸/苏氨酸激酶共识基序，与MAP激酶超家族成员、MAK和MAK相关激酶（MRK）有一定的相似性。此外，与经典的MAP激酶一样，MOK在激活环域中具有Thr-Glu-Tyr （TEY）基序。MOK在正常组织和器官中广泛表达，并定位于细胞质。MOK能够磷酸化几种已知的MAP激酶底物并进行自磷酸化。AEF的TEY基序突变使MOK的激酶活性消失，而用磷酸酶抑制剂冈田酸处理细胞可增强MOK的激酶活性，这表明存在上游激酶。佛波酯TPA可以刺激MOK的激酶活性，而血清刺激、渗透休克或大霉素治疗不能显著激活MOK。结论：这些结果表明，MOK与MAP激酶超家族的已知亚家族成员有远亲关系，因此可以将其归类为新成员。
Background: Members of the MAP kinase superfamily play important roles in a wide variety of signal transduction pathways, and several members have been identified. However, the diversity and complexity of cellular responses in mammalian systems may imply existence of hitherto unidentified members of the MAP kinase superfamily.Results: We report the molecular cloning and characterization of a novel member of the MAP kinase superfamily. We isolated full-length mouse and human cDNAs that encode complete open reading frames of a novel protein kinase, termed MOK. MOK consists of 419 (human) and 420 (mouse) amino acids, with a calculated molecular weight of 48kDa. MOK contains all of the protein serine/threonine kinase consensus motifs and shows a modest similarity to members of the MAP kinase superfamily and MAK and MAK-related kinase (MRK). In addition, MOK possesses a Thr-Glu-Tyr (TEY) motif in the activation loop domain, as do classical MAP kinases. MOK is widely expressed in normal tissues and organs and localizes to the cytoplasm. MOK is able to phosphorylate several known MAP kinase substrates and to undergo autophosphorylation. A mutation in the TEY motif to AEF abolished the kinase activity of MOK, and the treatment of cells with a phosphatase inhibitor, okadaic acid, enhanced the kinase activity of MOK, suggesting the existence of an upstream kinase. Phorbol ester TPA was found to stimulate the kinase activity of MOK, whereas serum stimulation, osmotic shock, or anisomycin treatment did not significantly activate MOK.Conclusion: These results indicate that MOK is distantly related to members of known subfamilies of the MAP kinase superfamily and can therefore be classified as a novel member.