Molecular mechanisms of host cell escape by Mycobacterium tuberculosis

摘要 结核分枝杆菌（Mtb）在人类中引起肺结核（TB）。仅2015年， 报告了新的病例，导致约140万人死亡。没有有效的结核病疫苗 并且仅存在次优的化疗剂。结核分枝杆菌，经过一段时间的细胞内复制和抑制宿主 细胞凋亡，离开吞噬体并触发细胞裂解以离开宿主细胞。在我们的世界里， 了解Mtb如何利用宿主细胞信号传导来介导这些事件。我们已经发现了一种 一种新的转录抑制因子Rv3167c对抑制宿主细胞吞噬体逃逸具有重要作用 坏死和大自噬（自噬）诱导。这种活性是通过抑制基因 编码合成和转运外细胞膜脂质酞菁的基因的转录 二枝蜡藻（PDIM）。在本申请中，我们提出利用一组独特的Mtb突变体， 在我们的实验室，以阐明结核分枝杆菌介导的宿主细胞坏死诱导的分子机制。 在AIM1中，我们将描述吞噬体后宿主细胞坏死和自噬信号通路的特征。 Mtb出口目标1.1.将测试Mtb如何介导宿主激酶AKT的调节。目标1.2和1.3将 探索分别导致坏死或自噬诱导的AKT下游的细胞信号传导事件。这些 将使用各种方法来确定信令网络中最感兴趣的中央信令集线器 针对宿主的治疗方法。在AIM 2中，我们将描述宿主细胞逃逸途径的相关性。 Mtb的毒力及其作为治疗方法靶点的潜力。在Aim 2.1中，敲除或敲入 小鼠将被用于证实选择的宿主细胞信号传导蛋白的重要性的离体发现， 体内感染。在目标2.2中，我们发现的宿主细胞坏死信号传导组分将被用来测试它们的功能。 在小鼠气溶胶感染期间Mtb毒力的相关性，从而确定它们作为新的 使用结核病小鼠模型的宿主靶向治疗的候选者。 我们相信，我们的研究结果将有很大的翻译潜力，因为抑制结核分枝杆菌介导的坏死， 应降低细菌的毒力并减少宿主肺部病变。

Abstract Mycobacterium tuberculosis (Mtb) causes pulmonary tuberculosis (TB) in humans. In 2015 alone,10.4 million new cases were reported, leading to approximately 1.4 million deaths. There are no effective vaccines for TB and only sub-optimal chemotherapeutics exist. Mtb, after a period of intracellular replication and inhibition of host cell apoptosis, leaves the phagosome and triggers cell lysis in order to exit the host cell. There is a gap in our understanding of how Mtb exploits host cell signaling in order to mediate these events. We have discovered a novel transcriptional repressor, Rv3167c, that is important for suppression of phagosomal escape, host cell necrosis and of macroautophagy (autophagy) induction. This activity is mediated via suppression of gene transcription of genes encoding for synthesis and transport of the outer cell membrane lipid phthiocerol dimycocerosates (PDIM). In the current application we propose to utilize a unique set of Mtb mutants discovered in our lab to elucidate the molecular mechanisms of Mtb-mediated host cell necrosis induction. In AIM1 we will characterize the host cell necrosis and autophagy signaling pathways engaged after phagosomal exit of Mtb. AIM1.1. will test how Mtb mediates the regulation of the host kinase AKT. The Aims 1.2 and 1.3 will explore cell signaling events downstream of AKT leading to necrosis or autophagy induction, respectively. These approaches will be used to identify central signaling hubs within the signaling network that will be most interesting for host directed therapeutic approaches. In AIM2 we will characterize the relevance of host cell escape pathway for virulence of Mtb and its potential as a target for therapeutic approaches. In Aim 2.1, knock-out or knock-in mice will be used to corroborate the ex vivo findings of the importance of select host cell signaling proteins during in vivo infection. In Aim 2.2 our discovery of host cell necrosis signaling components will be exploited to test their relevance for Mtb virulence during aerosol infection of mice and thus determine their potential as novel candidates for host-targeted therapeutics using the mouse model of tuberculosis. We believe that our findings will have great translational potential since inhibition of Mtb-mediated necrosis should reduce virulence of the bacteria and decrease host lung pathology.