盐诱导激酶2对放射损伤后细胞周期检查点中的调节作用

摘要

目的 了解盐诱导激酶2(SIK2)在电离辐射诱发G2/M细胞周期阻滞中的作用,并探讨其作用机制.方法 60Coγ射线照射HeLa细胞,慢病毒载体(pSicoR)构建SIK2的小干扰RNA(shRNA)表达载体,Lipofectamine 2000介导转染构建SIK2敲低表达细胞模型.Western blot检测SIK2的蛋白表达含量,流式细胞术检测细胞周期,磷酸化组蛋白3(pH3 Ser10)作为流式细胞检测分子标记物分析G2/M期检测点功能.结果 γ射线照射能诱发HeLa细胞SIK2蛋白表达增加.成功构建shRNA敲低HeLa细胞SIK2表达的细胞模型,并通过该细胞模型观察到在不同剂量照射后(1、2、4、6 Gy)降低SIK2蛋白表达水平导致细胞的放射敏感性增高(t=-3.445、-2.581、-3.251、-2.553,P＜0.05),γ射线诱发的细胞周期G2/M边界阻滞在照后5、6h被提前解除(=4.341、6.500,P＜0.05).Western blot检测结果表明,SIK2敲低细胞与对照细胞相比,放射损伤诱发的磷酸化CHK2蛋白提前消退.结论 SIK2在细胞放射损伤反应中参与细胞的G2/M检查点功能的调节,影响细胞的放射敏感性.%Objective To investigate the effect of salt-induced kinase 2 (SIK2) in the G2/M checkpoint in response to ionizing radiation and the possible mechanism.Methods HeLa cells were irradiated with 60Co γ-rays.The cell model of knockdown SIK2 expression was constrcuted by transfecting HeLa cells with a pSicoR-based lentivirus vector of expressing SIK2 shRNA by lipofectamin 2000.Western blot and flow cytometry were performed to measure the changes of SIK2 protein level and cell cycle distribution.The phosphorylated histone protein H3 on Ser 10 was used as a molecular marker of mitotic cells for detecting the function of G2/M checkpoint.Results The expression level of SIK2 protein increased in HeLa cells after 60Co γ-ray irradiation.A cell model of knockdown SIK2 expression was successfully generated by transfecting the specific shRNA against SIK2.Depression of SIK2 significantly increased the cellular sensitivity at 1,2,4,6 Gy post-irradiation (t =-3.445,-2.581,-3.251,-2.553,P ＜0.05),and led cells to release earlier from the G2/M boundary arrest compared to control cells at 5,6 h post-irradiation (t =4.341,6.500,P ＜ 0.05).Western blot analysis indicated that the irradiation-induced phosphorylated CHK2/T68 in SIK2 knock-down cells was earlier than that in control cells.Conclusions salt-induced kinase 2 (SIK2) participates in the regulation of G2/M checkpoint induced by ionizing radiation and affects cellular radiosensitivity.