Shields Ben J, Court Naomi W, Hauser Christine, Bukczynska Patricia E, Tiganis Tony
Department of Biochemistry and Molecular Biology, Monash University, Victoria, Australia.
Cell Cycle. 2008 Nov 1;7(21):3405-16. doi: 10.4161/cc.7.21.6950. Epub 2008 Nov 8.
Janus-activated kinases (JAKs) and Src family kinases (SFKs) and their common substrate signal transducer and activator of transcription (STAT)-3 are frequently hyperactivated in human cancer contributing to the proliferative drive by promoting G(1)/S and G(2)/M progression. Previous studies have established that the protein tyrosine phosphatase TCPTP can dephosphorylate and inactivate the SFK and JAK protein tyrosine kinases (PTKs) to attenuate cytokine signalling in vivo. In this study we determined whether TCPTP regulates SFK and JAK signalling during the cell cycle. We used primary mouse embryonic fibroblasts (MEFs) isolated from TCPTP(-/-) versus +/+ mice, immortalised TCPTP(-/-) MEFs versus those reconstituted with physiological levels of TCPTP and HeLa cells in which TCPTP protein levels had been suppressed by RNA interference, to establish TCPTP as a negative regulator of SFK, JAK1 and STAT3 signalling during the cell cycle. We found that the progression of TCPTP-deficient MEFs after the G(1) restriction point into S-phase was enhanced. We used RNA interference and pharmacological inhibitors to demonstrate that elevated SFK and downstream phosphatidylinositol 3-kinase signalling but not JAK1 or STAT3 signalling were required for the enhanced G(1)/S transition. These results identify TCPTP as a negative regulator of the cell cycle.
Janus 激酶（JAKs）、Src 家族激酶（SFKs）及其共同底物信号转导子和转录激活子（STAT）-3 在人类癌症中常常过度激活，通过促进 G(1)/S 和 G(2)/M 期进程推动细胞增殖。先前的研究已证实，蛋白酪氨酸磷酸酶 TCPTP 可使 SFK 和 JAK 蛋白酪氨酸激酶（PTKs）去磷酸化并使其失活，从而在体内减弱细胞因子信号传导。在本研究中，我们确定了 TCPTP 在细胞周期中是否调节 SFK 和 JAK 信号传导。我们使用从 TCPTP(-/-) 与 +/+ 小鼠分离的原代小鼠胚胎成纤维细胞（MEFs）、永生化的 TCPTP(-/-) MEFs 与用生理水平的 TCPTP 重建的 MEFs，以及通过 RNA 干扰抑制了 TCPTP 蛋白水平的 HeLa 细胞，来确定 TCPTP 是细胞周期中 SFK、JAK1 和 STAT3 信号传导的负调节因子。我们发现，TCPTP 缺陷的 MEFs 在 G(1) 限制点之后进入 S 期的进程加快。我们使用 RNA 干扰和药理学抑制剂证明，增强的 G(1)/S 期转换需要升高的 SFK 和下游磷脂酰肌醇 3-激酶信号传导，但不需要 JAK1 或 STAT3 信号传导。这些结果确定 TCPTP 是细胞周期的负调节因子。
