Notch signaling and functional relevance during Ehrlichia chaffeensis infection

项目摘要 查菲埃里希体是一种革兰氏阴性专性胞内细菌，其是人类腹泻的病原体。 嗜单核细胞埃立克体病（HME），一种新出现的威胁生命的蜱传人畜共患病。一个主要的知识差距是 在我们对E. chaffeensis建立了细胞内感染 单核吞噬细胞，避免先天宿主防御。我们最近证明了E.恰菲 利用1型分泌（T1 S）系统输出与宿主相互作用的串联重复蛋白（TRP）效应物 细胞DNA和参与转录和翻译的功能多样的宿主蛋白质阵列 调节，翻译后修饰，信号传导，免疫应答，细胞内运输，细胞骨架 组织和凋亡。两种TRP 120相互作用的宿主蛋白包括Notch激活蛋白。 金属蛋白酶ADAM 17和负调节因子FBW 7。Notch是一种高度保守的真核生物信号转导蛋白 在决定细胞生长、分化和功能方面起关键作用的一种途径，其延伸到免疫系统。 细胞最近的研究已经确定了Notch途径与负性细胞因子之间的功能关系。 调节toll样受体（TLR）介导的免疫应答和自噬，这两者都是 在E.查菲线虫感染作为本建议基础的初步研究 证明E. chaffeensis激活经典Notch信号通路以促进存活。激活 该途径通过下调PU.1（TLR 2/4所需的转录因子）促进埃里希体存活 表达）和TLR表达，以及通过抑制溶酶体融合和自噬降解。的 本提案的目的是确定埃里希体TRP在Notch途径激活中的作用， 证明TRP诱导的Notch介导的PRR表达和自噬的调节。我们假设 E. Chaffeensis通过TRP效应子和Notch信号通路之间的分子相互作用激活Notch信号通路。 Notch受体复合物启动抑制先天防御的促生存细胞信号程序。我们 本文将从以下几个方面对这一假说进行检验：（1）确定E.查菲诱导 Notch信号在宿主天然防御中的作用;茶咖啡TRP-mediated Notch 途径激活和调节。这项调查将扩大我们对高度剥削的认识。 保守的宿主细胞途径。chaffeensis效应子，以促进细菌细胞内存活。 此外，新的目标，为开发新的治疗方法，对E。查菲菌感染 将被识别。

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.