SHP-2 tyrosine phosphatase inhibits p73-dependent apoptosis and expression of a subset of p53 target genes induced by EGCG
SHP-2 tyrosine phosphatase inhibits p73-dependent apoptosis and expression of a subset of p53 target genes induced by EGCG
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DOI：
10.1073/pnas.0700642104
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发表时间：
2007-03-27
影响因子：
11.1
通讯作者：
Agarwal, Munna L.
中科院分区：
文献类型：
--
作者：
Amin, A. R. M. Ruhul;Thakur, Vijay S.;Agarwal, Munna L.
绿茶多酚，表没食子儿茶素没食子酸酯(EGCG)通过细胞凋亡和/或细胞周期停滞，以P53依赖的方式差异地调节癌细胞的生长。为了进一步阐明EGCG差异性生长调控的机制，我们研究了酪氨酸磷酸酶SHP-2的作用。比较表达WT和功能失活/截断的SHP-2的小鼠胚胎成纤维细胞(MEF)的反应，我们发现SHP-2的失活显著增强了细胞对EGCG介导的杀伤的敏感性。缺乏功能性SHP-2的MEF在EGCG治疗后会发生大量的细胞凋亡。通过比较基因表达谱，我们已经确定了一组在细胞凋亡过程中差异调节的p53转录靶点。对选定的一组基因进行的Western印迹和实时聚合酶链式反应分析进一步证实，该基因的表达依赖于SHP-2。在缺乏P53的MEF中也有类似的观察，证实这些“P53靶基因”的表达是不依赖于P53的。此外，EGCG可诱导两种细胞p73mRNA和蛋白的表达，但不能诱导p63的表达。在表达无功能的SHP-2的细胞中，p73的失活显著抑制了细胞的凋亡和P53靶基因的表达。尽管SHP2对JNK的磷酸化有不同的调节作用，但对于EGCG诱导的细胞凋亡和p53靶基因的表达来说，JNK的磷酸化是必不可少的。我们的结果发现SHP-2是EGCG诱导的细胞凋亡的负调控因子，并发现了一组p53靶基因的表达，这些基因的表达矛盾地不是由p53介导的，而是由其家族成员之一p73介导的。
Green tea polyphenol, epigallocatechin-3-gallate (EGCG) differentially regulates the cellular growth of cancer cells in a p53-dependent manner through apoptosis and/or cell cycle arrest. In an effort to further elucidate the mechanism of differential growth regulation by EGCG, we have investigated the role of the tyrosine phosphatase, SHP-2. Comparing the responses of mouse embryonic fibroblasts (MEFs), expressing either WT or functionally inactive/truncated SHP-2, we find that inactivation of SHP-2 remarkably sensitizes cells to EGCG-mediated killing. MEFs lacking functional SHP-2 undergo massive apoptosis upon treatment with EGCG. By comparing gene expression profiles, we have identified a set of transcriptional targets of p53 that are differentially modulated in cells undergoing apoptosis. Western blot and real-time PCR analyses of a select group of genes further confirm that the expression is SHP-2-dependent. Similar observations were made in MEFs lacking p53, confirming that the expression of these "p53 target genes" is p53-independent. In addition, EGCG treatment induced the expression of p73 mRNA and protein in both cell types, but not p63. Inactivation of p73 in cells expressing nonfunctional SHP-2 markedly inhibited apoptosis and p53 target gene expression. Although phosphorylation of JNK is differentially regulated by SHP2, it was found to be dispensable for EGCG-induced apoptosis and p53 target gene expression. Our results have identified SHP-2 as a negative regulator of EGCG-induced-apoptosis and have identified a subset of p53 target genes whose expression is paradoxically not mediated by p53 but by one of its family members, p73.