The mitochondrial apoptosis apparatus in the detection of microbial infection.

细胞凋亡是细胞死亡的一种明确的机制。然而，最近的文献数据表明，凋亡途径也可以被激活到一个较低的水平；然后这个过程就被‘中止’，细胞保持存活。进一步的研究表明，如果caspase不存在或被实验抑制，线粒体的凋亡可以诱导细胞因子的分泌。结合这两个观察，我们提供了证据，低水平的，‘流产’的细胞凋亡诱导上皮细胞分泌白介素6和白介素8。我们进一步发现，感染了许多病毒和细菌的上皮细胞诱导了“流产的细胞凋亡”，这被认为是在没有凋亡的情况下对基因组DNA的破坏，但依赖于凋亡装置的组件。相应地，线粒体凋亡缺陷的细胞在感染多种感染剂时分泌较少的IL-6和IL-8。我们建议研究流产的细胞凋亡是人类细胞识别病原体的一种机制的概念。在项目的第一部分，我们将测试模式识别受体(PRR)可以诱导流产的细胞凋亡的假设，以及这种信号是它们在感染病毒(我们将使用痘苗病毒衍生物MVA)和细菌(沙眼衣原体)感染期间的活动的一部分。以前已经描述过PRRs的促凋亡活性；我们认为流产的细胞凋亡可能是这一信号的功能之一。我们要么特异性地触发单个PRR并检测流产的细胞凋亡，要么去除单个PRR或信号成分并测试对MVA或沙眼衣原体诱导的流产细胞凋亡的影响。化学抑制Bc l-2可以触发流产的细胞凋亡。在这里，我们将测试各种促和抗凋亡的Bcl2家族成员在调节流产细胞凋亡中的作用。在该项目的第二部分，我们将努力了解线粒体下游流产细胞凋亡接受过程中的信号事件。我们发现信号分子刺痛在流产的细胞凋亡中起作用，并且文献数据涉及线粒体DNA。我们进一步显示，在流产的细胞凋亡过程中，线粒体分子Smac被释放到胞浆中。我们将跟进这些观察，研究Smac的释放及其后果，并将其与细胞色素c的释放进行比较。我们还将测试线粒体DNA的作用，并将分析一些可能涉及细胞因子诱导的核心信号事件。流产细胞凋亡是一个新的概念，证明其在微生物识别中的应用将是理解和建立这一概念的重要一步。

Apoptosis is a well-defined mechanism of cell death. However, recent literature data indicate that the apoptosis-pathway can also be activated to only a low level; the process is then ‘aborted’ and the cell stays alive. It has further been shown that mitochondrial apoptosis can induce cytokine secretion if apoptotic caspases are absent or experimentally inhibited. Combining these two observations, we provide evidence that low-level, ‘abortive’ apoptosis induces the secretion of interleukin (IL) 6 and IL-8 from epithelial cells. We further find that infection of epithelial cells with a number of viruses and bacteria induces ‘abortive apoptosis’, identified as damage to the genomic DNA in the absence of apoptosis but dependent on components of the apoptosis apparatus. Accordingly, cells with defects in mitochondrial apoptosis secreted less IL-6 and IL-8 upon infection with a number of infectious agents. We here propose to study the concept that abortive apoptosis serves as a mechanism of pathogen recognition by human cells. In the first part of the project we will test the hypothesis that pattern recognition receptors (PRR) can induce abortive apoptosis, and that this signaling is part of their activity during infection with a virus (we will use the vaccinia virus derivative MVA) and a bacterium (Chlamydia trachomatis). Pro-apoptotic activity of PRRs has been described before; we believe that abortive apoptosis may be a function of this signaling. We will either specifically trigger individual PRR and test for abortive apoptosis, or take away individual PRR or signaling components and test for the effect on abortive apoptosis induced by MVA or C. trachomatis. Chemical inhibition of Bcl-2 can trigger abortive apoptosis. We will here test the roles of the various pro- and anti-apoptotic Bcl-2-family members in the regulation of abortive apoptosis. In the second part of the project we will endeavor to understand signaling events in the reception of abortive apoptosis downstream of mitochondria. We find a role of the signaling molecule STING in abortive apoptosis, and literature data implicate mitochondrial DNA. We further show the release of the mitochondrial molecule Smac into the cytosol during abortive apoptosis. We will follow up on these observations, investigate Smac-release and its consequences and compare it to the release of cytochrome c. We will also test for the role of mitochondrial DNA and will analyse some of the core signaling events that are likely involved in cytokine induction. Abortive apoptosis is a novel concept, and the demonstration of its use in microbe recognition would be an important step to understand and to establish this concept.