Type III effector regulation of host signal transduction systems

 描述（由申请人提供）：革兰氏阴性细菌病原体的III型分泌系统在病原体与其宿主之间形成最直接的界面之一。这些“针状”分子机器将细菌效应蛋白直接注入宿主 细胞，以破坏先天免疫应答并促进细菌复制、传播和疾病进展。效应蛋白是独特的毒力因子，因为它们经常捕获或模拟宿主信号转导分子的特性。本研究的重点是三个重要的细菌III型效应家族。首先，我们将询问沙门氏菌、志贺氏菌和肠出血性大肠杆菌所需的细菌鸟嘌呤核苷酸交换因子（GEFs）的大家族。大肠杆菌的致病性，分别通过其共同的能力，激活Rho家族GT3信号级联。这里描述的研究将推进最近的高通量遗传筛选方法，以确定宿主细胞环境中的细菌效应蛋白定位。这些初步研究的结果将被应用于揭示负责志贺氏菌入侵的宿主-病原体相互作用的系统动力学，特别是宿主酸性磷脂对细菌GEF信号传导功能的作用（目的1）。其次，我们将表征细菌半胱氨酸蛋白酶的侵入质粒抗原J（IpaJ）家族的新酶促机制，该家族催化宿主ARF GTdR细胞底物上的N-肉豆蔻酰修饰的蛋白水解消除。从这些研究中收集的见解将通过对志贺氏菌先天免疫途径逃避的详细分析，特别是蛋白质去豆蔻酰化在这一过程中的作用（目的2）。最后，我们将研究志贺氏菌E3-泛素连接酶超家族的孤儿成员，特别是他们通过蛋白质泛素化调节宿主免疫成分的能力（目的3）。开发针对细菌和宿主酶复合物的新药将是对抗新兴抗生素耐药微生物的创新方法。因此，通过揭示III型效应子家族功能的分子细节，从生物化学到系统生物学，我们将发现可能用于治疗干预的细菌病原体的潜在弱点。重要的是，这些研究还将为许多传染病病原体的致病机制以及人类宿主的生物学提供新的见解。

 DESCRIPTION (provided by applicant): The type III secretion system of Gram-negative bacterial pathogens creates one of the most direct interfaces between pathogens and their hosts. These `needle-like' molecular machines inject bacterial effector proteins directly into host cells for the purpose of destroying an innate immune response and facilitating bacterial replication, dissemination, and disease progression. Effector proteins are unique virulence factors in that they often capture or mimic the properties of host signal transduction molecules. The present study focuses on three important bacterial type III effector families. First, we will interrogate a large family of bacterial Guanine-nucleotide exchange factors (GEFs) required for Salmonella, Shigella, and enterohaemorrhagic E. coli pathogenesis, respectively, through their common ability to activate Rho-family GTPase signaling cascades. The studies described here will advance recent high-throughput genetic screening approaches to identify bacterial effector protein localization within the host cellular environment. Findings from these preliminary studies will be applied to uncover the system dynamics of host-pathogen interactions responsible for Shigella invasion, and particularly the role of host acidic phospholipids on bacterial GEF signaling functions (Aim 1). Second, we will characterize the novel enzymatic mechanism of the Invasion plasmid antigen J (IpaJ) family of bacterial cysteine proteases that catalyze the proteolytic elimination of N-myristoyl modifications on host ARF GTPase cellular substrates. Insights gleaned from these studies will be advanced through a detailed analysis of Shigella innate immune pathway evasion, and specifically the role of protein demyristoylation in this process (Aim 2). Finally, we will investigate orphan members of the Shigella E3-ubiquitin ligase superfamily, and specifically their ability to modulate host immune components through protein ubiquitylation (Aim 3). Developing new drugs that target bacterial and host enzyme complexes would be an innovative approach to combat emerging antibiotic resistant microbes. Therefore, by revealing molecular details of type III effector family functions, from biochemistry to systems biology, we will uncover sites of potential weakness in bacterial pathogens that may be exploited for therapeutic intervention. Importantly, these studies will also provide new insights into the pathogenic mechanisms of numerous infectious disease agents and also into the biology of the human host.