Department of Medicine, Evans Biomedical Research Center, Boston, MA, USA.
Mol Cell Biol. 2013 May;33(10):1916-24. doi: 10.1128/MCB.00015-13. Epub 2013 Mar 4.
We hypothesized that nucleophosmin (NPM), a nucleolar phosphoprotein, is critical for Bax-mediated cell death. To test this hypothesis, Bax activation was induced by metabolic stress. During stress, nucleolar NPM translocated into the cytosol, NPM-Bax complexes formed, and both NPM and Bax accumulated in mitochondria. Expression of a cytosol-restricted NPM mutant (NPM-ΔNLS), but not a nucleus-restricted NPM mutant, increased NPM-Bax complex formation, mitochondrial NPM and Bax accumulation, mitochondrial membrane injury, caspase 3 activation, and ischemia-induced cell death. Coexpression of NPM-ΔNLS with constitutively active Bax mutants caused nearly universal cell death in the absence of metabolic stress, whereas expression of active Bax or NPM-ΔNLS alone did not. A Bax peptide that disrupts NPM-Bax interaction significantly reduced cell death caused by exposure to metabolic inhibitors in vitro and preserved kidney function after ischemia in vivo. Thus, NPM-Bax interaction enhances mitochondrial Bax accumulation, organelle injury, and cell death. NPM-Bax complex formation is a novel target for preventing ischemic tissue injury.
我们假设核仁磷酸蛋白（NPM），一种核仁磷酸蛋白，对 Bax 介导的细胞死亡至关重要。为了验证这一假设，通过代谢应激诱导 Bax 的激活。在应激过程中，核仁 NPM 易位到细胞质中，NPM-Bax 复合物形成，NPM 和 Bax 均在线粒体中积累。表达细胞质限制的 NPM 突变体（NPM-ΔNLS），而不是核限制的 NPM 突变体，增加了 NPM-Bax 复合物的形成、线粒体 NPM 和 Bax 的积累、线粒体膜损伤、半胱天冬酶 3 的激活和缺血诱导的细胞死亡。NPM-ΔNLS 与组成型活性 Bax 突变体共表达，在没有代谢应激的情况下几乎会导致普遍的细胞死亡，而单独表达活性 Bax 或 NPM-ΔNLS 则不会。一种破坏 NPM-Bax 相互作用的 Bax 肽可显著减少体外代谢抑制剂暴露引起的细胞死亡，并在体内缺血后保留肾功能。因此，NPM-Bax 相互作用增强了线粒体 Bax 的积累、细胞器损伤和细胞死亡。NPM-Bax 复合物的形成是预防缺血性组织损伤的一个新靶点。
