Yuan Liangping, Yu Wen-Mei, Xu Min, Qu Cheng-Kui
Department of Medicine, Division of Hematology/Oncology, Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, Ohio 44106, USA.
J Biol Chem. 2005 Dec 30;280(52):42701-6. doi: 10.1074/jbc.M506768200. Epub 2005 Oct 31.
SHP-2, a tyrosine phosphatase implicated in diverse signaling pathways induced by growth factors and cytokines, is also involved in DNA damage-triggered signaling and cellular responses. We previously demonstrated that SHP-2 played an important role in DNA damage-induced apoptosis and G2/M cell cycle checkpoint. In the present studies, we have provided evidence that SHP-2 functions in DNA damage apoptosis and G2/M arrest in catalytically dependent and independent manners, respectively. Mutant embryonic fibroblasts with the Exon 3 deletion mutation in SHP-2 showed decreased apoptosis and diminished G2/M arrest in response to cisplatin treatment. Wild type (WT), but not catalytically inactive mutant SHP-2 (SHP-2 C459S), rescued the apoptotic response of the mutant cells. Interestingly, both WT and SHP-2 C459S efficiently restored the G2/M arrest response. Furthermore, inhibition of the catalytic activity of endogenous SHP-2 in WT cells by overexpression of SHP-2 C459S greatly decreased cell death but not G2/M arrest induced by cisplatin. Biochemical analyses revealed that activation of c-Abl kinase was decreased in SHP-2 C459S-overexpressing cells. However, DNA damage-induced translocation of Cdc25C from the nucleus to the cytoplasm was fully restored in both WT and SHP-2 C459S "rescued" cells. Additionally, we demonstrated that the role of SHP-2 in DNA damage-induced cellular responses was independent of the tumor suppressor p53. Embryonic stem cells with the SHP-2 deletion mutation showed markedly decreased sensitivity to cisplatin-induced apoptosis, attributed to impaired induction of p73 but not p53. In agreement with these results, DNA damage-induced apoptosis and G2/M arrest were also decreased in SHP-2/p53 double mutant embryonic fibroblasts. Collectively, these studies have further defined the mechanisms by which SHP-2 phosphatase regulates DNA damage responses.
SHP-2是一种参与生长因子和细胞因子诱导的多种信号通路的酪氨酸磷酸酶，也参与DNA损伤引发的信号传导和细胞反应。我们之前证明SHP-2在DNA损伤诱导的细胞凋亡和G2/M细胞周期检查点中起重要作用。在本研究中，我们提供了证据表明SHP-2分别以催化依赖和独立的方式在DNA损伤凋亡和G2/M期阻滞中发挥作用。SHP-2中具有外显子3缺失突变的突变胚胎成纤维细胞对顺铂治疗的凋亡反应降低，G2/M期阻滞减弱。野生型（WT）而非催化失活的突变型SHP-2（SHP-2 C459S）挽救了突变细胞的凋亡反应。有趣的是，WT和SHP-2 C459S均有效地恢复了G2/M期阻滞反应。此外，通过过表达SHP-2 C459S抑制WT细胞中内源性SHP-2的催化活性，可大大降低顺铂诱导的细胞死亡，但不会降低G2/M期阻滞。生化分析表明，在过表达SHP-2 C459S的细胞中，c-Abl激酶的激活降低。然而，在WT和SHP-2 C459S“挽救”的细胞中，DNA损伤诱导的Cdc25C从细胞核向细胞质的转位均完全恢复。此外，我们证明SHP-2在DNA损伤诱导的细胞反应中的作用独立于肿瘤抑制因子p53。具有SHP-2缺失突变的胚胎干细胞对顺铂诱导的凋亡敏感性明显降低，这归因于p73而非p53的诱导受损。与这些结果一致，在SHP-2/p53双突变胚胎成纤维细胞中，DNA损伤诱导的凋亡和G2/M期阻滞也降低。总的来说，这些研究进一步明确了SHP-2磷酸酶调节DNA损伤反应的机制。
