Daniel Swarovski Research Laboratory, Department of Visceral-, Transplant- and Thoracic Surgery, Innsbruck Medical University, Austria.
Exp Cell Res. 2013 Oct 15;319(17):2728-38. doi: 10.1016/j.yexcr.2013.07.029. Epub 2013 Aug 7.
We have shown previously that mitochondrial ROS production is essential to turn growth factor (GF) removal into cell death. Activated RAF, AKT, Bcl-2 and antioxidants protected equally well against ROS accumulation and subsequent death. Here we investigated whether protection by survival signaling and antioxidants utilizes shared or distinct targets. Using serum deprivation from NIH 3T3 fibroblasts and IL-3 withdrawal from promyeloid 32D cells, we showed that pro-survival signaling by activated RAF but not AKT prevented the decline in Mcl-1 following GF abrogation. GF starvation increased levels of Bim in both model systems, which was prevented by RAF in 32D cells but not in NIH 3T3 fibroblasts. RAF and AKT suppressed activation and mitochondrial translocation of BAX. Also, antioxidant treatment efficiently prevented BAX activation and death of 32D cells but showed little effect on its mitochondrial translocation. No significant impact of antioxidant treatment on Bim or Mcl-1 expression was observed. ROS produced during GF abrogation also did not alter the activity of intracellular signaling pathways, which have been implicated previously in cell killing by pro-oxidants. Together these data suggest Bcl-2 family proteins as convergence point for RAF and ROS in life and death decisions.
我们之前已经表明，线粒体 ROS 的产生对于将生长因子（GF）去除转化为细胞死亡是必不可少的。激活的 RAF、AKT、Bcl-2 和抗氧化剂同样能很好地防止 ROS 积累和随后的死亡。在这里，我们研究了生存信号和抗氧化剂的保护是否利用了共同或不同的靶点。我们使用 NIH 3T3 成纤维细胞的血清剥夺和髓样前体细胞 32D 细胞的 IL-3 撤出，表明激活的 RAF 而不是 AKT 的生存信号可以防止 GF 去除后 Mcl-1 的下降。GF 饥饿在这两个模型系统中均增加了 Bim 的水平，这种增加在 32D 细胞中被 RAF 阻止，但在 NIH 3T3 成纤维细胞中未被阻止。RAF 和 AKT 抑制了 BAX 的激活和线粒体易位。此外，抗氧化剂处理能有效地防止 BAX 激活和 32D 细胞死亡，但对其线粒体易位几乎没有影响。抗氧化剂处理对 Bim 或 Mcl-1 的表达也没有显著影响。GF 去除过程中产生的 ROS 也没有改变先前被认为参与促氧化剂细胞杀伤的细胞内信号通路的活性。这些数据表明，Bcl-2 家族蛋白是 RAF 和 ROS 在生死决策中的交汇点。
