Department of Biological Sciences, Graduate School of Science and Technology, Kumamoto University, Kumamoto, Japan.
J Cell Biochem. 2018 Jul;119(7):5734-5749. doi: 10.1002/jcb.26757. Epub 2018 Mar 30.
The RNA-binding protein RBM3, a cold shock protein whose expression is elevated under hypothermic conditions, plays an important role in cell survival; however, little is known about the mechanism underlying the mild hypothermia-mediated regulation of RBM3 expression and apoptosis. Here we show that the transcription factor NF-κB p65 is phosphorylated at Ser276 and activates RBM3 gene transcription via binding to a particular element within the promoter region in response to induced hypothermia, elevating the protein expression, and suppressing apoptosis. Treatment with caffeic acid phenethyl ester (CAPE), a potent and specific inhibitor that suppresses the translocation of NF-κB p65 from the cytoplasm to the nucleus, resulted in decreased levels of RBM3 mRNA and protein and increased incidence of apoptosis despite cells were cultured under hypothermic conditions. Overexpression of RBM3 abolished the induction of apoptosis in cells treated with CAPE, indicating that NF-κB p65-upregulated RBM3 expression is necessary for the suppression of apoptosis. In addition, experiments with cells overexpressing RBM3 supported the finding demonstrating that the mild hypothermia-mediated higher expression of RBM3 suppressed the induction of apoptosis. Conversely, experiments with cells deficient in RBM3 supported the finding demonstrating that the CAPE-mediated loss of RBM3 induced apoptosis. These results suggest that NF-κB p65 is a critical mediator of mild hypothermia, to which cells are exposed as an extracellular environment, and a central inducer of RBM3 expression, which is responsible for preventing cells from apoptosis. Moreover, CAPE may have a potential for the application to a therapeutic agent for the treatment of cancers.
RNA 结合蛋白 RBM3 是一种冷休克蛋白，其表达在低温条件下升高，在细胞存活中发挥重要作用；然而，低温介导的 RBM3 表达和细胞凋亡调节的机制知之甚少。在这里，我们表明转录因子 NF-κB p65 在 Ser276 处发生磷酸化，并通过结合启动子区域内的特定元件响应诱导的低温而激活 RBM3 基因转录，从而提高蛋白质表达并抑制细胞凋亡。用咖啡酸苯乙酯（CAPE）处理，一种有效的、特异性抑制 NF-κB p65 从细胞质易位到细胞核的抑制剂，导致 RBM3 mRNA 和蛋白质水平降低，尽管细胞在低温条件下培养，凋亡的发生率增加。尽管细胞在低温条件下培养，CAPE 处理的细胞中 RBM3 的过表达消除了细胞凋亡的诱导，表明 NF-κB p65 上调 RBM3 的表达对于抑制细胞凋亡是必需的。此外，用过表达 RBM3 的细胞进行的实验支持了这样的发现，即低温介导的 RBM3 高表达抑制了细胞凋亡的诱导。相反，用缺乏 RBM3 的细胞进行的实验支持了这样的发现，即 CAPE 介导的 RBM3 缺失诱导了细胞凋亡。这些结果表明，NF-κB p65 是细胞作为细胞外环境暴露的低温的关键介质，并且是 RBM3 表达的中心诱导剂，其负责防止细胞凋亡。此外，CAPE 可能具有作为治疗癌症的治疗剂的应用潜力。
