Ehrlichia Notch SLiM-activated oncoprotein inhibition of apoptosis

摘要 查菲埃立克体（Ehrlichia chaffeensis）; ch.）是一种革兰氏阴性、专性胞内细菌， 人类嗜单核细胞埃立克体病（HME），一种新出现的、危及生命的、蜱媒人畜共患病。E. ch. 优先感染单核吞噬细胞，并通过破坏先天性免疫防御在细胞内存活 部分由串联重复蛋白（TRP）效应子介导。在过去的十年里，我们的实验室已经确定了 大量的分子Ehrlichial TRP-宿主相互作用，许多是新的科学，照亮呼吸 以及感染期间发生的病原体-宿主相互作用动力学的复杂性。我们证明了E. ch.是 依赖于包括Notch和Wnt在内的保守的真核细胞信号传导途径的激活来进行感染。 然而，理解Notch激活事件的分子基础，即E. ch. repurposes Notch 感染信号仍然是我们知识中的一个主要空白。因此，本次调查的目的是确定 分子和细胞机制E.已经进化到重新利用Notch信号来感染。我们提出 大肠ch.TRP120具有不同的真核蛋白相互作用模块，称为短线性基序（SLiM）， 模拟Notch配体功能并直接接合同源受体以利用Notch信号传导进行感染。这 研究将解决我们对蛋白质相互作用模块的功能多样性作用的有限理解 在宿主-病原体相互作用和细胞重编程的连续体中。这项研究的长期目标是 是确定埃里希体宿主细胞拟态的分子基础，以及感染和 免疫逃避本提案的目的是确定所涉及的分子相互作用和功能 E. ch.TRP120 Notch配体模拟通过抑制宿主 细胞凋亡我们假设E. ch.TRP120具有激活Notch信号传导的Notch SLiM模拟物， 上调抗凋亡调节因子（MCL 1和NICD），从而抑制线粒体凋亡信号传导， 半胱天冬酶激活。目标1将定义E。ch.TRP120 Notch SLiM模拟物并研究受体结合 和信号;目标2将检查E。ch.TRP120 Notch上调的MCL 1对线粒体凋亡的抑制; Aim 3将探讨E. ch. XIAP的Notch稳定化和半胱天冬酶活化的抑制。这 研究将扩展我们对E. ch.TRP120表面蛋白 利用Notch信号来抑制细胞凋亡并促进宿主细胞存活和感染。其意义 研究正在确定机制策略，从而使具有小基因组和有限的细胞内病原体 许多效应蛋白，已经进化出宿主模拟模块，以重新利用宿主细胞信号传导来操纵 下游宿主防御机制的感染。对E.病理生物学也将 促进埃立克体属的新型治疗方法的开发。和细胞内的病原体 SLiM模拟或利用保守的细胞途径进行感染和免疫逃避。

ABSTRACT Ehrlichia chaffeensis (E. ch.) is a gram-negative, obligately intracellular bacterium and the etiologic agent of human monocytotropic ehrlichiosis (HME), an emerging, life-threatening, tick-borne zoonosis. E. ch. preferentially infects mononuclear phagocytes and survives intracellularly by subverting innate immune defenses mediated in part by tandem repeat protein (TRP) effectors. Within the last decade, our laboratory has identified a multitude of molecular ehrlichial TRP-host interactions, many that are new to science, illuminating the breath and complexity of pathogen-host interaction dynamics that occur during infection. We have shown that E. ch. is dependent on activation of conserved eukaryotic signaling pathways including Notch and Wnt for infection. However, understanding the molecular basis of Notch activation events, whereby E. ch. repurposes Notch signaling for infection remains a major gap in our knowledge. Thus, the purpose of this investigation is to define the molecular and cellular mechanisms E. ch. has evolved to repurpose Notch signaling for infection. We propose that E. ch. TRP120 has distinct eukaryotic protein interaction modules known as short linear motifs (SLiMs) that mimic Notch ligand function and directly engage cognate receptors to exploit Notch signaling for infection. This investigation will address our limited understanding of the functionally diverse roles of protein interaction modules in the continuum of host-pathogen interactions and cellular reprogramming. The long-term goal of this research is to define the molecular basis of Ehrlichia host cell mimicry, and the mechanisms involved in infection and immune evasion. The objective of this proposal is to determine the molecular interactions involved and functional mechanisms whereby E. ch. TRP120 Notch ligand mimicry establishes and promotes infection by inhibiting host cell apoptosis. We hypothesize that E. ch. TRP120 has a Notch SLiM mimetic that activates Notch signaling to upregulate anti-apoptotic regulators (MCL1 and NICD), thereby inhibiting mitochondrial apoptotic signaling and caspase activation. Aim 1 will define the E. ch. TRP120 Notch SLiM mimetic and investigate receptor binding and signaling; Aim 2 will examine E. ch. TRP120 Notch-upregulated MCL1 inhibition of mitochondrial apoptosis; and Aim 3 will investigate the role of E. ch. Notch stabilization of XIAP and inhibition of caspase activation. This investigation will extend our knowledge of the molecular interactions by which E. ch. TRP120 surface protein exploits Notch signaling to inhibit apoptosis and promote host cell survival and infection. The significance of this research is defining the mechanistic strategies whereby intracellular pathogens with small genomes and a limited number of effector proteins, have evolved host mimicry modules to repurpose host cell signaling to manipulate downstream host defense mechanisms for infection. A molecular understanding of E. ch. pathobiology will also facilitate development of novel therapeutic approaches for Ehrlichia spp. and intracellular pathogens that utilize SLiM mimicry or exploit conserved cellular pathways for infection and immune evasion.