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Shp2 E76K突变体通过上调Bcl-XL赋予TF-1髓系细胞不依赖细胞因子的生存能力。

Shp2E76K mutant confers cytokine-independent survival of TF-1 myeloid cells by up-regulating Bcl-XL.

作者信息

Ren Yuan, Chen Zhengming, Chen Liwei, Woods Nicholas T, Reuther Gary W, Cheng Jin Q, Wang Hong-gang, Wu Jie

机构信息

Molecular Oncology Program, H. Lee Moffitt Cancer Center and Research Institute, Department of Interdisciplinary Oncology, University of South Florida, Tampa 33612, USA.

出版信息

J Biol Chem. 2007 Dec 14;282(50):36463-73. doi: 10.1074/jbc.M705789200. Epub 2007 Oct 17.

Abstract

Shp2 has been known to mediate growth factor-stimulated cell proliferation, but its role in cell survival is less clear. Gain-of-function Shp2 mutants such as Shp2E76K are associated with myeloid leukemias. We found that Shp2E76K could transform cytokine-dependent human TF-1 myeloid cells into cytokine independence and further characterized the Shp2E76K-induced cell survival mechanism in this study. Expression of Shp2E76K suppressed the cytokine withdrawal-induced intrinsic/mitochondrial apoptosis pathway, which is controlled by the Bcl-2 family proteins. Analysis of Bcl-2 family proteins showed that Bcl-XL and Mcl-1 were up-regulated in Shp2E76K-transformed TF-1 (TF-1/Shp2E76K) cells. Knockdown of Bcl-XL but not Mcl-1 with short hairpin RNAs prevented Shp2E76K-induced cytokine-independent survival. Roscovitine, which down-regulated Mcl-1, also did not prevent cytokine-independent survival of TF-1/Shp2E76K cells, whereas the Bcl-XL inhibitor HA14-1 did. Ras and mitogen-activated protein kinases Erk1 and Erk2 (Erk1/2) were constitutively activated in TF-1/Shp2E76K cells, whereas little active Akt was detected under cytokine-free conditions. Shp2E76K-induced Bcl-XL expression was suppressed by Mek inhibitors and by a dominant-negative Mek1 mutant but not by the phosphoinositide 3-phosphate inhibitor LY294002 and the Akt inhibitor API-2. Inhibition of Erk1/2 blocked cytokine-independent survival of TF-1/Shp2E76K cells, whereas inhibition of Akt had a minimal effect on cytokine-independent survival of TF-1/Shp2E76K cells. These results show that Shp2E76K can evoke constitutive Erk1/2 activation in TF-1 cells. Furthermore, Shp2E76K induces cytokine-independent survival of TF-1 cells by a novel mechanism involving up-regulation of Bcl-XL through the Erk1/2 pathway.

摘要

已知Shp2可介导生长因子刺激的细胞增殖,但其在细胞存活中的作用尚不清楚。功能获得性Shp2突变体,如Shp2E76K,与髓系白血病相关。我们发现Shp2E76K可将细胞因子依赖性人TF-1髓系细胞转化为不依赖细胞因子,并在本研究中进一步表征了Shp2E76K诱导的细胞存活机制。Shp2E76K的表达抑制了细胞因子撤除诱导的由Bcl-2家族蛋白控制的内源性/线粒体凋亡途径。对Bcl-2家族蛋白的分析表明,在Shp2E76K转化的TF-1(TF-1/Shp2E76K)细胞中,Bcl-XL和Mcl-1上调。用短发夹RNA敲低Bcl-XL而非Mcl-1可阻止Shp2E76K诱导的不依赖细胞因子的存活。下调Mcl-1的Roscovitine也不能阻止TF-1/Shp2E76K细胞不依赖细胞因子的存活,而Bcl-XL抑制剂HA14-1则可以。Ras和丝裂原活化蛋白激酶Erk1和Erk2(Erk1/2)在TF-1/Shp2E76K细胞中持续活化,而在无细胞因子条件下几乎检测不到活性Akt。Mek抑制剂和显性负性Mek1突变体可抑制Shp2E76K诱导的Bcl-XL表达,但磷酸肌醇3-磷酸抑制剂LY294002和Akt抑制剂API-2则不能。抑制Erk1/2可阻止TF-1/Shp2E76K细胞不依赖细胞因子的存活,而抑制Akt对TF-1/Shp2E76K细胞不依赖细胞因子的存活影响最小。这些结果表明,Shp2E76K可在TF-1细胞中引起持续性Erk1/2活化。此外,Shp2E76K通过一种新机制诱导TF-1细胞不依赖细胞因子存活,该机制涉及通过Erk1/2途径上调Bcl-XL。

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