ROLE OF ESXG-ESXH IN MYCOBACTERIUM TUBERCULOSIS PATHOGENESIS

项目摘要 结核分枝杆菌（Mtb）每年杀死的人比任何其他感染都多。MTB成功了 因为它损害了巨噬细胞和树突细胞的关键功能。结核分枝杆菌在巨噬细胞中存活， 阻止了吞噬体的正常成熟，创造了一个类似于早期 核内体通过损害MHCII类抗原呈递，Mtb破坏CD 4 + T细胞识别 感染的巨噬细胞对结核分枝杆菌如何破坏这些过程缺乏详细的了解。我们 发现Mtb分泌蛋白EsxG和EsxH在这两个过程中起着关键作用。EsxG和EsxH 作为异源二聚体（EsxG-EsxH）分泌。我们确定了EsxG-EsxH的宿主靶点：肝细胞生长 因子调节酪氨酸激酶底物（HGS/HRS）。HRS是内体分选的一个组成部分， 运输机械所需的复杂设备（ESCRT）。ESCRT在贩运细胞中起着众所周知的作用 溶酶体的表面受体进行降解。我们还发现ESCRT是吞噬体所必需的 成熟和最佳抗原呈递。因此，通过抑制ESCRT，EsxG-EsxH可以促进Mtb 以多种方式生存。现在，我们新的初步数据表明，EsxG-EsxH也针对 洛眼脑肾综合征（OCRL）。OCRL是一种具有底物特异性的肌醇5-磷酸酶 磷脂酰肌醇-4，5-二磷酸。与HRS一样，OCRL也参与了内体和吞噬体的作用 功能这项研究的中心假设是EsxG-EsxH损害了OCRL和HRS的功能， 从而阻断吞噬体成熟、抑制抗原呈递和促进Mtb毒力。我们 提出EsxG-EsxH损害OCRL和HRS向分枝杆菌吞噬体的募集。在 对于OCRL，我们假设EsxG阻止了OCRL与其内体结合相互作用的能力 搭档在HRS的情况下，我们假设EsxG-EsxH促进HRS泛素化，从而锁定了HRS的表达。 处于非活性形式的分子。我们将确定EsxG-EsxH是否抑制OCRL，定义它如何损害 HRS，并测试两种EsxG-EsxH靶标对体内感染的贡献。我们之前的工作 这个项目使我们有独特的资格进行这些研究。我们的发现将提供更重要的 对结核分枝杆菌毒力策略的机制性洞察。我们还将阐明OCRL的重要性， 基础巨噬细胞生物学中的ESCRT。揭示结核分枝杆菌破坏宿主细胞的根本基础 功能将导致更好的治疗和疫苗的结核病。

PROJECT SUMMARY Mycobacterium tuberculosis (Mtb) kills more people yearly than any other infection. Mtb is successful because it impairs key functions of macrophages and dendritic cells. Mtb survives in macrophages by preventing the normal maturation of the phagosome, creating a replicative niche that resembles an early endosome. By impairing MHC class II (MHCII) antigen presentation, Mtb undermines CD4+ T cell recognition of infected macrophages. A detailed understanding of how Mtb undermines these processes is lacking. We found that the Mtb secreted proteins, EsxG and EsxH, play a critical role in both processes. EsxG and EsxH are secreted as a heterodimer (EsxG-EsxH). We identified a host target of EsxG-EsxH: hepatocyte growth factor-regulated tyrosine kinase substrate (HGS/HRS). HRS is a component of the endosomal sorting complex required for transport (ESCRT) machinery. ESCRT plays a well-described role in trafficking cell surface receptors to the lysosome for degradation. We also found that ESCRT is required for phagosome maturation and optimal antigen presentation. Therefore, by inhibiting ESCRT, EsxG-EsxH can promote Mtb survival in multiple ways. Now, our new preliminary data suggest that EsxG-EsxH also targets oculocerebrorenal syndrome of Lowe (OCRL). OCRL is an inositol 5-phosphatase with substrate specificity for phosphatidlylinositol-4,5-bisphosphate. Like HRS, OCRL is involved in endosome and phagosome function. The central hypothesis of this grant is that EsxG-EsxH impairs the function of both OCRL and HRS, thereby blocking phagosome maturation, inhibiting antigen presentation, and promoting Mtb virulence. We propose that EsxG-EsxH impairs recruitment of both OCRL and HRS to mycobacterial phagosomes. In the case of OCRL, we hypothesize that EsxG blocks the ability of OCRL to interact with its endosomal binding partner. In the case of HRS, we hypothesize that EsxG-EsxH promote HRS ubiquitination, which locks the molecule in an inactive form. We will determine whether EsxG-EsxH inhibits OCRL, define how it impairs HRS, and test the contribution of both EsxG-EsxH targets to infection in vivo. Our previous work on this project makes us uniquely qualified to carry out these studies. Our findings will provide further important mechanistic insight into Mtb's virulence strategies. We will also elucidate the importance of OCRL and ESCRT in basic macrophage biology. Revealing the fundamental basis by which Mtb sabotages host cellular functions will lead to better therapies and vaccines for Mtb.