Notch signaling and functional relevance during Ehrlichia chaffeensis infection

项目摘要 查菲埃里希菌是一种革兰氏阴性、专性胞内细菌，是人类 单核细胞增生性埃立克体病(HME)，一种新出现的威胁生命的人畜共患病。一个主要的知识差距是 在我们对查菲肠杆菌建立细胞内感染的机制的理解中 单核吞噬细胞，避免固有的宿主防御。我们最近证明了查菲埃希氏菌 利用1型分泌系统(T1S)输出与宿主相互作用的串联重复蛋白(TRP)效应器 参与转录和翻译的细胞DNA和一系列功能多样的宿主蛋白 调控、翻译后修饰、信号传递、免疫反应、细胞内运输、细胞骨架 组织和细胞凋亡。两种与TRP120相互作用的宿主蛋白包括Notch激活 金属蛋白酶ADAM17和负性调控因子FBW7。Noch是一种高度保守的真核信号。 在决定细胞生长、分化和功能方面起关键作用的途径，它延伸到免疫 细胞。最近的研究已经确定了Notch通路和负值之间的功能关系 调节Toll样受体(TLR)介导的免疫反应和自噬，两者都是 在查菲埃希氏菌感染期间被抑制。作为这项建议的基础的初步研究 证明查菲乳杆菌激活典型的Notch信号通路以促进生存。激活 该途径通过下调PU1(TLR2/4所需的转录因子)促进埃利希菌存活 表达)和TLR表达，以及抑制溶酶体融合和自噬降解。这个 本研究的目的是确定埃利希菌TRPs在Notch途径激活中的作用，并 证明了色氨酸诱导的Notch介导的PRR表达和自噬的调节。我们假设 查菲乳杆菌通过色氨酸效应器和细胞因子之间的分子相互作用激活Notch途径 缺口受体复合体，以启动一个生存细胞信号程序，抑制先天防御。我们 我将通过以下具体目的来检验这一假说：(1)确定查菲乳杆菌诱导的效果 Notch信号在天然寄主防御中的作用；(2)明确了茶树Trp介导的Notch的机制 途径的激活和调节。这项调查将扩大我们对高度开采的了解 通过查菲氏杆菌效应器保守宿主细胞途径，以促进细菌在细胞内的生存。 此外，开发治疗查菲埃希氏菌感染的新方法的新靶点 将会被确认。

Project Summary Ehrlichia chaffeensis is a gram-negative, obligately intracellular bacterium that is the causative agent of human monocytotropic ehrlichiosis (HME), an emerging life-threatening tick-borne zoonosis. A major knowledge gap is in our understanding of the mechanisms whereby E. chaffeensis establishes intracellular infection of the mononuclear phagocyte and avoids innate host defenses. We recently demonstrated that E. chaffeensis utilizes a type 1 secretion (T1S) system to export tandem repeat protein (TRP) effectors that interact with host cell DNA and a functionally diverse array of host proteins involved in transcriptional and translational regulation, post translational modification, signaling, immune response, intracellular trafficking, cytoskeletal organization and apoptosis. Two TRP120 interacting host proteins include the Notch activating metalloprotease ADAM17, and the negative regulator, FBW7. Notch is a highly conserved eukaryotic signaling pathway that plays a key role in determining cell growth, differentiation and function, which extends to immune cells. Recent studies have identified a functional relationship between the Notch pathway and negative regulation of toll-like receptor (TLR)-mediated immune responses and autophagy, both of which are suppressed during E. chaffeensis infection. Preliminary studies that serve as the basis for this proposal demonstrate that E. chaffeensis activates canonical Notch signaling pathway to promote survival. Activation of this pathway promotes ehrlichial survival by downregulating PU.1 (transcription factor required for TLR2/4 expression) and TLR expression, and by inhibiting of lysosomal fusion and autophagic degradation. The objective of this proposal is to determine the role of Ehrlichia TRPs in Notch pathway activation, and to demonstrate TRP-induced Notch-mediated modulation of PRR expression and autophagy. We hypothesize E. chaffeensis activates the Notch pathway through molecular interactions between TRP effectors and the Notch receptor complex to initiate a prosurvival cell signaling program that suppresses innate defenses. We will test this hypothesis with the following specific aims: (1) Determine the effect of E. chaffeensis induced Notch signaling on innate host defenses; (2) Define the mechanism of E. chaffeensis TRP-mediated Notch pathway activation and regulation. This investigation will expand our knowledge regarding exploitation of highly conserved host cell pathways by E. chaffeensis effectors in order to facilitate bacterial intracellular survival. Moreover, new targets for the development of novel therapeutic approaches against E. chaffeensis infection will be identified.