A regulatory mechanism for RSK2 NH(2)-terminal kinase activity.
A regulatory mechanism for RSK2 NH(2)-terminal kinase activity.
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DOI：
10.1158/0008-5472.can-08-4959
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发表时间：
2009-05-15
期刊：
影响因子：
11.2
通讯作者：
Dong Z
中科院分区：
文献类型：
--
作者：
Cho YY;Yao K;Pugliese A;Malakhova ML;Bode AM;Dong Z
我们以前的研究结果表明，RSK 2在肿瘤促进剂（如表皮生长因子或12-O-十四烷酰基佛波醇-13-乙酸酯）诱导的增殖和细胞转化中起着关键作用，而可食用植物中发现的天然化合物山奈酚选择性抑制RSK 2活性。然而，RSK 2激活的分子机制尚不清楚。在此，我们提供的证据表明，NH 2-末端激酶结构域（NTD）的RSK 2的激活是需要的细胞外信号调节激酶介导的COOH-末端激酶结构域（CTD）的激活。我们还发现，NTD在底物磷酸化中起着关键作用，山奈酚与NTD结合，但不与活性和非活性形式的CTD结合。同源建模的RSK 2 NH 2-末端结构域和小分子对接，通过诱变实验验证，清楚地表明，Val 82和Lys 100是山奈酚结合和RSK 2活性的关键氨基酸。此外，荧光和Western印迹结果表明，与非恶性细胞系或正常组织相比，RSK 2蛋白水平在癌细胞系以及癌组织中显著更高。此外，山奈酚抑制恶性人类癌细胞系的增殖，包括A431、SK-MEL-5和SK-MEL-28以及HCT-116。这些结果表明，用天然化合物如山奈酚靶向RSK 2可能是化学预防或化学治疗应用的良好策略。
Our previous findings indicated that RSK2 plays a critical role in proliferation and cell transformation induced by tumor promoters, such as epidermal growth factor or 12-O-tetradecanoylphorbol-13-acetate, and that kaempferol, a natural compound found in edible plants, selectively inhibits RSK2 activity. However, the molecular mechanism for RSK2 activation is unclear. Herein, we provide evidence showing that NH2-terminal kinase domain (NTD) activation of RSK2 is required for the activation of the extracellular signal-regulated kinase–mediated COOH-terminal kinase domain (CTD). We also found that the NTD plays a key role in substrate phosphorylation and that kaempferol binds with the NTD but not the CTD in both the active and inactive forms. Homology modeling of the RSK2 NH2-terminal domain and small-molecule docking, validated by mutagenesis experiments, clearly showed that Val82 and Lys100 are critical amino acids for kaempferol binding and RSK2 activity. Furthermore, immunohistofluorescence and Western blot results indicated that the RSK2 protein level is markedly higher in cancer cell lines as well as cancer tissues compared with nonmalignant cell lines or normal tissues. In addition, kaempferol inhibited proliferation of malignant human cancer cell lines, including A431, SK-MEL-5 and SK-MEL-28, and HCT-116. These results indicate that targeting RSK2 with natural compounds, such as kaempferol, might be a good strategy for chemopreventive or chemotherapeutic application.