Role of mTOR signaling in endothelial responses to Rickettsia rickettsii infection.

项目总结/摘要 立克次体病作为一种传染病，对全球人类具有历史性和持续性的影响。 健康由蜱传立克次体（Rr）引起的落基山斑疹热，一种革兰氏阴性专性 胞内α-变形杆菌，是最严重的立克次体病之一，在美国是一种必须报告的疾病。一个 人类疾病发病机理和已建立的实验室感染模型的重要决定因素是 血管微血管内皮细胞衬里的播散性感染，导致“立克次体血管炎” 其由脉管系统的炎症和受损的血管渗透性定义， 重要器官的失衡和水肿。RR诱导的内皮反应包括获得促粘附， 促凝血和促炎表型以及主转录调节因子核因子的激活， κB，但决定先天性免疫应答和宿主细胞命运的机制代表了一种新的免疫学机制。 被忽视的重要领域。值得注意的是，自噬作为“双刃”宿主的潜在作用 防御机制能够支持细胞内病原体，抗炎内皮细胞反应， 最大限度地减少血管损伤和功能障碍，并平衡促炎信号维斯抗炎信号， 立克次氏体毒力的生物学基础是尚未探索的科学研究领域。我们目前的证据 表明信号转导和转录激活蛋白STAT 3的磷酸化增加， 与自噬和雷帕霉素机制靶点（mTOR）激活的发生相一致的反应 Rr感染人内皮细胞期间的复合物C1和C2。我们有趣的初步发现， 广泛发表的关于RR诱导的转录激活的工作作为我们假设的基础， mTOR作为促炎/促粘附相对于细胞因子的平衡的中心调节决定因素发挥作用。 RR感染的内皮的抗炎性先天免疫应答。考虑到mTOR信号传导 涉及两个结构和功能不同的复合物，目标1将解决根本重要的 在用Rr菌株的内皮感染过程中mTORC 1和mTORC 2的活化状态的定义 不同的毒力，并确定其对宿主细胞自噬和立克次体复制的抑制作用。 目的2将解释mTORC 1和C2在感染诱导的炎症反应中的潜在差异作用。 发信号。我们将战略性地采用当代，尖端和跨学科的细胞和 分子生物学，以获得新的和独特的见解宿主mTORC 1/C2激活与 立克次体毒力及其在通过调节自噬和促免疫应答控制先天免疫应答中的作用 /使用体外和体内感染模型的抗炎信号传导。拟定的病原体分析 与能够调节有益和/或有害宿主反应的新型信号传导检查点的相互作用 将指导创新的治疗策略，以打击与（重新）出现立克次体病相关的后遗症。

PROJECT SUMMARY/ABSTRACT Rickettsioses as infectious diseases stand out for their historic and continued impact on the global human health. Rocky Mountain spotted fever due to tick-transmitted Rickettsia rickettsii (Rr), a Gram-negative obligate intracellular α-proteobacterium, is one of the most severe rickettsioses and a notifiable illness in the USA. An important determinant of disease pathogenesis in humans and established laboratory models of infection is disseminated infection of microvascular endothelial cell lining of blood vessels, resulting in ‘rickettsial vasculitis’ defined by inflammation of the vasculature and compromised vascular permeability leading to tissue fluid imbalance and edema of vital organs. Rr-induced endothelial responses include acquisition of pro-adhesive, pro-coagulant, and pro-inflammatory phenotypes and activation of master transcription regulator nuclear factor- κB, yet the mechanisms underlying determination of innate immune responses and host cell fate represent a neglected area of fundamental relevance. Notably, potential roles of autophagy as a ‘double-edged’ host defense mechanism capable of supporting intracellular pathogens, anti-inflammatory endothelial responses to minimize vascular damage and dysfunction, and the balance of pro- vis-à-vis anti-inflammatory signaling as the biological basis of rickettsial virulence represent unexplored arenas of scientific enquiry. We present evidence suggesting increased phosphorylation of signal transducer and activator of transcription protein STAT3, a response coinciding with the onset of autophagy and activation of mechanistic target of rapamycin (mTOR) complexes C1 and C2 during Rr infection of human endothelial cells. Our intriguing preliminary findings and extensive published work on Rr-induced transcriptional activation serve as the basis of our hypothesis that mTOR functions as a central regulatory determinant of the balance of pro-inflammatory/pro-adhesive vis-a-vis anti-inflammatory innate immune responses of Rr-infected endothelium. Considering that mTOR signaling involves two structurally and functionally distinct complexes, Aim 1 will address the fundamentally important definition of the activation status of mTORC1 and mTORC2 during endothelial infection with Rr strains of varying virulence and determine the effects of their inhibition on host cell autophagy and rickettsial replication. Aim 2 will then decipher potentially differential roles of mTORC1 and C2 in infection-induced inflammatory signaling. We will strategically employ contemporary, cutting-edge, and interdisciplinary approaches of cell and molecular biology to gain new and unique insights into host mTORC1/C2 activation in correlation with rickettsial virulence and their roles in governing innate immune responses via regulation of autophagy and pro- /anti-inflammatory signaling using in vitro and in vivo models of infection. The proposed analysis of pathogen interactions with novel signaling checkpoints capable of regulating beneficial and/or detrimental host responses will guide innovative therapeutic strategies to combat the sequelae associated with (re)emerging rickettsioses.