Liu Xiangjun, Pan Zhi, Zhang Lingqiang, Sun Qiao, Wan Jinghong, Tian Chunyan, Xing Guichun, Yang Juntao, Liu Xiaolin, Jiang Jizhi, He Fuchu
State Key Laboratory of Proteomics, Beijing Proteomics Research Center, Beijing Institute of Radiation Medicine, 27 Taiping Road, Beijing 100850, China.
Cell Signal. 2008 Jan;20(1):230-40. doi: 10.1016/j.cellsig.2007.10.012. Epub 2007 Oct 16.
The Bcl-2 family of proteins is the key regulators of cell apoptosis at the mitochondria level. The BH3-only pro-apoptotic member BclGs was unique among the family due to its highly specific expression in human testis and has been demonstrated to induce apoptosis dependent on the BH3 domain. However, the molecular mechanism of BclGs-induced apoptosis remains unclear. Here we show that overexpression of BclGs could induce Bax expression upregulation and translocation to mitochondria, cytochrome c release and activation of caspase-3. Moreover, we identified JAB1 as a novel BclGs-specific binding protein through a yeast two-hybrid screening in a human testis cDNA library. BclGs interacts with JAB1 both in vitro and in vivo. N-terminal region of BclGs (aa 1-67) was required for the interaction. Importantly, JAB1 and BclGs co-expression synergistically induces apoptosis. JAB1 could compete with Bcl-XL/Bcl-2 to bind to BclGs; thus, promote the apoptosis. RNAi-mediated knock-down of JAB1 results in the reduced proapoptotic activity of BclGs. Taken together, our results provided the first evidence that JAB1 is involved in the regulation of mitochondrial apoptotic pathway through specific interaction with BclGs.
Bcl-2蛋白家族是线粒体水平细胞凋亡的关键调节因子。仅含BH3结构域的促凋亡成员BclGs在该家族中独具特色，因其在人类睾丸中具有高度特异性表达，且已证明其诱导的凋亡依赖于BH3结构域。然而，BclGs诱导凋亡的分子机制仍不清楚。在此我们表明，BclGs的过表达可诱导Bax表达上调并转位至线粒体，导致细胞色素c释放及caspase-3激活。此外，我们通过在人类睾丸cDNA文库中进行酵母双杂交筛选，鉴定出JAB1是一种新的BclGs特异性结合蛋白。BclGs在体外和体内均与JAB1相互作用。BclGs的N端区域（氨基酸1 - 67）参与这种相互作用。重要的是，JAB1与BclGs共表达可协同诱导凋亡。JAB1可与Bcl-XL/Bcl-2竞争结合BclGs，从而促进凋亡。RNA干扰介导的JAB1敲低导致BclGs的促凋亡活性降低。综上所述，我们的结果首次证明JAB1通过与BclGs的特异性相互作用参与线粒体凋亡途径的调控。
