Faculty of Medical Sciences, Institute for Cell and Molecular Biosciences (ICaMB), Newcastle University, Newcastle Upon Tyne, U.K.
Biosci Rep. 2019 Sep 16;39(9). doi: 10.1042/BSR20192101. Print 2019 Sep 30.
The nuclear factor-κB (NF-κB) family of transcription factors can directly or indirectly regulate many important areas of biology, including immunity, inflammation and cell survival. One intriguing aspect of NF-κB crosstalk with other cell signalling pathways is its regulation of mitochondrial biology, including biogenesis, metabolism and apoptosis. In addition to regulating the expression of mitochondrial genes encoded in the nucleus, NF-κB signalling components are also found within mitochondria themselves and associated with mitochondrial DNA. However, complete biochemical analysis of mitochondrial and sub-mitochondrial localisation of all NF-κB subunits has not been undertaken. Here, we show that only the RelA NF-κB subunit and its inhibitor IκBα reside within mitochondria, whilst p50 is found in the endoplasmic reticulum (ER). Fractionation of mitochondria revealed that only RelA was found in the mitoplast, the location of the mtDNA. We demonstrate that hypoxia leads to a very rapid but transient accumulation of RelA and IκBα in mitochondria. This effect required reactive oxygen species (ROS) but was not dependent on the hypoxia sensing transcription factor subunit HIF1α or intracellular Ca release. We also observed rapid mitochondrial localisation of transcription factor STAT3 following hypoxia. Inhibition of STAT3 blocked RelA and IκBα mitochondrial localisation revealing a previously unknown aspect of crosstalk between these key cellular regulators.
核因子-κB（NF-κB）转录因子家族可以直接或间接地调节生物学的许多重要领域，包括免疫、炎症和细胞存活。NF-κB 与其他细胞信号通路相互作用的一个有趣方面是其对线粒体生物学的调节，包括生物发生、代谢和细胞凋亡。除了调节核编码的线粒体基因的表达外，NF-κB 信号成分也存在于线粒体本身及其与线粒体 DNA 的关联中。然而，尚未对所有 NF-κB 亚基的线粒体和亚线粒体定位进行完整的生化分析。在这里，我们表明只有 RelA NF-κB 亚基及其抑制剂 IκBα存在于线粒体中，而 p50 存在于内质网（ER）中。线粒体的分级分离表明，只有 RelA 存在于线粒体中，即 mtDNA 的位置。我们证明缺氧会导致 RelA 和 IκBα在短时间内快速但短暂地积累在线粒体中。这种效应需要活性氧（ROS），但不依赖于缺氧感应转录因子亚基 HIF1α 或细胞内 Ca 释放。我们还观察到缺氧后转录因子 STAT3 在线粒体中的快速定位。STAT3 的抑制阻止了 RelA 和 IκBα 的线粒体定位，揭示了这些关键细胞调节剂之间相互作用的一个以前未知的方面。
