Mechanism and importance of mitochondrial import of BH3-only proteins during apoptosis

细胞线粒体释放细胞色素c是线粒体凋亡的关键步骤。虽然很明显，Bcl2蛋白家族的成员调节细胞色素c的释放，但如何实现这一点仍存在争议。目前在文献中讨论了两种模型；两种模型都认为仅BH3-Only的BH3家族蛋白质组触发了释放，然后依赖于BH3-Only蛋白质对Bax和Bak的激活。然而，对于分子的存在，这些模型几乎是完全不一致的。我们最近发现，在酵母和哺乳动物的线粒体凋亡模型中，BH3-Only蛋白BIMS的线粒体输入/插入到线粒体膜外膜对于其促凋亡功能是必不可少的。在这个项目中，我们的目标是了解线粒体输入BH3-Only蛋白对细胞凋亡的分子细节和一般重要性。已知的BH3-Only蛋白的线粒体插入和线粒体输入机制的要求将进行测试。Bax和Bak的激活是否在相同程度上依赖于只有BH3的蛋白质进口的问题将被分析。这一假说将被进一步检验，即线粒体插入BH3-Only蛋白是线粒体易位的触发因素，从而激活Bax。最后，我们将研究BH3-Only蛋白在细胞凋亡过程中的线粒体插入。

The release of cytochrome c from a cell’s mitochondria is a key step in mitochondrial apoptosis. Although it is clear that the members of the Bcl-2 protein family regulate cytochrome c-release, it is still under dispute how this is achieved. Two models are presently discussed in the literature; both agree that the BH3-only group of Bcl-2 family proteins trigger the release, which then depends on the BH3-only protein dependent activation of the Bcl-2 family proteins Bax and Bak. However, the models are in almost complete disagreement as to the molecular occurrences. We have recently found that mitochondrial import/insertion of the BH3-only protein BimS into the outer mitochondrial membrane is essential for its pro-apoptotic function in yeast and mammalian models of mitochondrial apoptosis. In this project, we aim at understanding the molecular details and the general importance of mitochondrial import of BH3-only proteins for apoptosis. Mitochondrial insertion of the known BH3-only proteins and requirement of the mitochondrial import machinery will be tested. The question whether the activation of Bax and Bak relies on BH3-only protein import to the same degree will be analysed. The hypothesis will further be tested that mitochondrial insertion of BH3-only proteins is the trigger of mitochondrial translocation and thus activation of Bax. Finally, mitochondrial insertion of BH3-only proteins in cells undergoing apoptosis will be investigated.