Molecular mechanisms of host cell escape by Mycobacterium tuberculosis

摘要 结核分枝杆菌(Mtb)可引起人类肺结核(TB)。仅在2015年，就有1040万人 报告了新病例，导致约140万人死亡。目前还没有有效的结核病疫苗 而且只存在次优的化疗药物。MTB，在细胞内复制和宿主抑制一段时间后 细胞凋亡，离开吞噬小体，触发细胞裂解以离开宿主细胞。我们有一条鸿沟 了解结核分枝杆菌如何利用宿主细胞信号来调节这些事件。我们发现了一个 新的转录抑制因子Rv3167c，对抑制宿主细胞吞噬小体逃逸很重要 坏死和巨型自噬(自噬)诱导。这种活性是通过抑制基因来实现的。 编码合成和运输外细胞膜脂质邻苯三酚的基因的转录 二霉油酸盐(PDIM)。在目前的应用中，我们建议利用发现的一组独特的结核分枝杆菌突变株 本实验室旨在阐明结核分枝杆菌介导的宿主细胞坏死的分子机制。 在AIM1中，我们将描述吞噬后宿主细胞的坏死和自噬信号通路 Mtb出口。AIM1.1。将测试Mtb如何介导宿主激酶AKT的调节。AIMS 1.2和1.3将 探索AKT下游分别导致坏死或自噬诱导的细胞信号事件。这些 将使用方法来确定信令网络中最感兴趣的中央信令中枢 用于宿主指导的治疗方法。在AIM2中，我们将描述宿主细胞逃逸途径的相关性 结核分枝杆菌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 小鼠将被用来证实体外发现的选择宿主细胞信号蛋白的重要性 体内感染。在Aim 2.2中，我们将利用我们对宿主细胞坏死信号组件的发现来测试其 小鼠气溶胶感染期间结核分枝杆菌毒力的相关性，从而确定其作为新的潜在的 使用小鼠结核病模型进行宿主靶向治疗的候选对象。 我们相信，我们的发现将具有巨大的翻译潜力，因为抑制了结核分枝杆菌介导的坏死。 应降低细菌的毒力，减少宿主肺的病理改变。

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.