Liang Bin, Song Xuhong, Liu Gefei, Li Rui, Xie Jianping, Xiao Lifeng, Du Mudan, Zhang Qiaoxia, Xu Xiaoyuan, Gan Xueqiong, Huang Dongyang
Center for Molecular Biology, Shantou University Medical College, Shantou, Guangdong, China.
Exp Cell Res. 2007 Aug 1;313(13):2833-44. doi: 10.1016/j.yexcr.2007.04.032. Epub 2007 May 10.
Nuclear orphan receptor TR3/Nur77/NGFI-B is a novel apoptotic effector protein that initiates apoptosis largely by translocating from the nucleus to the mitochondria, causing the release of cytochrome c. However, it is possible that TR3 translocates to other organelles. The present study was designed to determine the intracellular localization of TR3 following CD437-induced nucleocytoplasmic translocation and the mechanisms involved in TR3-induced apoptosis. In human neuroblastoma SK-N-SH cells and human esophageal squamous carcinoma EC109 and EC9706 cells, 5 microM CD437 induced translocation of TR3 to the endoplasmic reticulum (ER). This distribution was confirmed by immunofluorescence analysis, subcellular fractionation analysis and coimmunoprecipitation analysis. The translocated TR3 interacted with ER-targeting Bcl-2; initiated an early release of Ca(2+) from ER; resulted in ER stress and induced apoptosis through ER-specific caspase-4 activation, together with induction of mitochondrial stress and subsequent activation of caspase-9. Our results identified a novel distribution of TR3 in the ER and defined two parallel mitochondrial- and ER-based pathways that ultimately result in apoptotic cell death.
核孤儿受体TR3/Nur77/NGFI-B是一种新型凋亡效应蛋白，主要通过从细胞核转位至线粒体，引发细胞色素c的释放来启动细胞凋亡。然而，TR3也有可能转位至其他细胞器。本研究旨在确定CD437诱导的核质转位后TR3在细胞内的定位以及TR3诱导细胞凋亡的相关机制。在人神经母细胞瘤SK-N-SH细胞以及人食管鳞状细胞癌EC109和EC9706细胞中，5微摩尔的CD437诱导TR3转位至内质网（ER）。这种分布通过免疫荧光分析、亚细胞分级分离分析和免疫共沉淀分析得以证实。转位后的TR3与靶向内质网的Bcl-2相互作用；引发内质网中Ca(2+)的早期释放；导致内质网应激，并通过内质网特异性半胱天冬酶-4的激活诱导细胞凋亡，同时诱导线粒体应激及随后半胱天冬酶-9的激活。我们的研究结果确定了TR3在内质网中的一种新分布，并明确了两条平行的基于线粒体和内质网的途径，最终导致凋亡性细胞死亡。
