Oncogenic KRAS and BRAF activation of the MEK/ERK signaling pathway promotes expression of dual-specificity phosphatase 4 (DUSP4/MKP2) resulting in nuclear ERK1/2 inhibition
Oncogenic KRAS and BRAF activation of the MEK/ERK signaling pathway promotes expression of dual-specificity phosphatase 4 (DUSP4/MKP2) resulting in nuclear ERK1/2 inhibition
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DOI：
10.1038/onc.2012.88
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发表时间：
2013-01-31
期刊：
影响因子：
8
通讯作者：
Rivard, N.
中科院分区：
文献类型：
--
作者：
Cagnol, S.;Rivard, N.
在高达50%的结直肠癌中发现了KRAS和BRAF基因的功能获得性突变。这些突变导致BRAF/MEK信号通路的激活，最终刺激ERK 1/2促分裂原活化蛋白激酶。一旦激活，ERK 1/2从细胞质易位到细胞核。这一过程已被证明是诱导许多细胞反应所必需的，尽管调节ERK核功能的分子机制，特别是在致癌刺激下，仍有待探索。在此，我们研究了正常肠上皮隐窝细胞（IEC）中KRAS（G12 V）和BRAF（V600 E）致癌激活后ERK 12活性的时空调节。结果表明，这些癌基因的表达显着刺激ERK 1/2活性和形态转化的IEC。然而，重要的是，在细胞核中未观察到ERK磷酸化，而仅限于KRAS（G12 V）和BRAF（V600 E）转化的IEC的细胞质。细胞核ERK磷酸化的缺乏是由于钒酸敏感的磷酸酶活性。细胞核ERK去磷酸化与MEK依赖性DUSP 4磷酸酶的快速表达密切相关。此外，T361、T363、S390和S395残基的MEK依赖性磷酸化高度稳定DUSP 4蛋白。最后，在人结直肠癌细胞中，ERK 1/2活性也被限制在细胞质中，并且用过钒酸盐处理重新激活细胞核中的ERK 1/2。因此，发现DUSP 4 mRNA在分析的所有结肠直肠癌细胞中以MEK依赖性方式高度表达。这些发现表明，DUSP 4作为负反馈机制的一部分，在肠道肿瘤发生期间控制核ERK激活的持续时间和幅度。Oncogene（2013）32，564-576; doi：10.1038/onc.2012.88; 2012年3月19日在线发表
Gain-of-function mutations in KRAS and BRAF genes are found in up to 50% of colorectal cancers. These mutations result in the activation of the BRAF/MEK signaling pathway culminating in the stimulation of ERK1/2 mitogen-activated protein kinases. Upon activation, ERK1/2 translocate from the cytoplasm to the nucleus. This process has been shown to be required for the induction of many cellular responses, although the molecular mechanisms regulating ERK nuclear function, especially under oncogenic stimulation, remain to be explored. Herein, we examined the spatiotemporal regulation of ERK1/2 activity upon oncogenic activation of KRAS(G12V) and BRAF(V600E) in normal intestinal epithelial crypt cells (IECs). Results demonstrate that expression of these oncogenes markedly stimulated ERK1/2 activities and morphologically transformed IECs. Importantly however, ERK phosphorylation was not observed in the nucleus, but restricted to the cytoplasm of KRAS(G12V)- and BRAF(V600E)-transformed IECs. The absence of nuclear ERK phosphorylation was due to a vanadate-sensitive phosphatase activity. Nuclear ERK dephosphorylation was found to be tightly correlated with the rapid expression of DUSP4 phosphatase induced in an MEK-dependent manner. In addition, MEK-dependent phosphorylation of T361, T363, S390 and S395 residues highly stabilized DUSP4 protein. Finally, in human colorectal cancer cells, ERK1/2 activities were also confined to the cytoplasm and treatment with pervanadate reactivated ERK1/2 in the nucleus. Accordingly, DUSP4 mRNAs were found to be highly expressed, in an MEK-dependent manner, in all colorectal cancer cells analyzed. These findings indicate that DUSP4 functions as part of a negative feedback mechanism in the control of the duration and magnitude of nuclear ERK activation during intestinal tumorigenesis. Oncogene (2013) 32, 564-576; doi:10.1038/onc.2012.88; published online 19 March 2012