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和它们的宿主之间建立了最直接的接口之一。这些“针状”分子机器将细菌效应物蛋白直接注入宿主体内 破坏先天免疫反应并促进细菌复制、传播和疾病发展的细胞。效应蛋白是独特的毒力因子，因为它们经常捕捉或模仿宿主信号转导分子的性质。目前的研究集中在三个重要的细菌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致病所需的一大类细菌鸟嘌呤核苷酸交换因子(GEF)，它们通过共同激活Rho家族GTPase信号级联反应。这里描述的研究将推进最近的高通量遗传筛选方法，以确定细菌效应蛋白在宿主细胞环境中的定位。这些初步研究的结果将用于揭示导致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全球环境基金信号功能的作用(目标1)。其次，我们将描述细菌半胱氨酸蛋白酶的侵袭质粒抗原J(IpaJ)家族的新的酶机制，该家族催化宿主ARF GTPase细胞底物上N-肉豆蔻酰基修饰的蛋白水解性消除。从这些研究中收集到的见解将通过对志贺氏菌先天免疫途径规避的详细分析来推进，特别是蛋白质脱髓鞘在这一过程中的作用(目标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(目标3)。开发针对细菌和宿主酶复合体的新药将是对抗新出现的抗药性微生物的创新方法。因此，通过揭示从生物化学到系统生物学的III型效应器家族功能的分子细节，我们将揭示细菌病原体中潜在的弱点，这些部位可能被用于治疗干预。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.