Chiusolo Valentina, Jacquemin Guillaume, Yonca Bassoy Esen, Vinet Laurent, Liguori Lavinia, Walch Michael, Kozjak-Pavlovic Vera, Martinvalet Denis
Department of Cell Physiology and Metabolism, University of Geneva, Rue Michel-Servet-1, Geneva, Switzerland.
Department of Radiology and Medical Informatics, Geneva University Hospital, Geneva, Switzerland.
Cell Death Differ. 2017 Apr;24(4):747-758. doi: 10.1038/cdd.2017.3. Epub 2017 Mar 24.
We have found that granzyme B (GB)-induced apoptosis also requires reactive oxygen species resulting from the alteration of mitochondrial complex I. How GB, which does not possess a mitochondrial targeting sequence, enter this organelle is unknown. We show that GB enters the mitochondria independently of the translocase of the outer mitochondrial membrane complex, but requires instead Sam50, the central subunit of the sorting and assembly machinery that integrates outer membrane β-barrel proteins. Moreover, GB breaches the inner membrane through Tim22, the metabolite carrier translocase pore, in a mitochondrial heat-shock protein 70 (mtHsp70)-dependent manner. Granzyme A (GA) and caspase-3 use a similar route to the mitochondria. Finally, preventing GB from entering the mitochondria either by mutating lysine 243 and arginine 244 or depleting Sam50 renders cells more resistant to GB-mediated reactive oxygen species and cell death. Similarly, Sam50 depletion protects cells from GA-, GM- and caspase-3-mediated cell death. Therefore, cytotoxic molecules enter the mitochondria to induce efficiently cell death through a noncanonical Sam50-, Tim22- and mtHsp70-dependent import pathway.
我们发现，颗粒酶B（GB）诱导的细胞凋亡还需要线粒体复合体I改变产生的活性氧。不具有线粒体靶向序列的GB如何进入该细胞器尚不清楚。我们发现GB独立于线粒体外膜复合体转位酶进入线粒体，但需要分选与组装机器的核心亚基Sam50，该机器负责整合外膜β-桶蛋白。此外，GB通过代谢物载体转位酶孔Tim22以依赖线粒体热休克蛋白70（mtHsp70）的方式突破内膜。颗粒酶A（GA）和半胱天冬酶-3采用类似的途径进入线粒体。最后，通过突变赖氨酸243和精氨酸244或耗尽Sam50来阻止GB进入线粒体，会使细胞对GB介导的活性氧和细胞死亡更具抗性。同样，耗尽Sam50可保护细胞免受GA、GM和半胱天冬酶-3介导的细胞死亡。因此，细胞毒性分子通过非经典的依赖Sam50、Tim22和mtHsp70的导入途径进入线粒体以有效诱导细胞死亡。
