Dissecting the means by which type 3 substrates are defined & secreted

许多人类细菌病原体的毒力依赖于跨国界的纳米机器，包括 III型分泌系统（T3SS），其作用是直接递送数十种毒力蛋白，通常称为 进入哺乳动物细胞的胞质溶胶。在我们对第三型糖尿病的理解中， 分泌的（T3S）蛋白，称为效应物，被定义并递送至T3S装置（T3SA）。而 每一种病原体都将自己独特的一套效应物注入宿主，它们的机器组件共享一个高水平的 相似度。几十年来，教条一直是效应物分泌依赖于 与其N末端区域结合的小的酸性T3S分子伴侣。这些伴侣控制着 通过介导蛋白质的募集到分选平台来分泌蛋白质，分选平台是一种在蛋白质之间循环的复合物。 胞质溶胶和膜包埋的T3SA。有趣的是，同源分子伴侣尚未被确定用于 大多数T3S效应子，包括来自深入研究的沙门氏菌、耶尔森氏菌、志贺氏菌和 致病性大肠杆菌T3SS。在这里，我们提出的数据，支持存在一个非典型的T3SS 分子伴侣非依赖性（CI）途径可能在许多遗传学上不同的T3SS中保守 家庭在这里，使用福氏志贺菌T3SS作为模型系统，我们建议： 1.确定T3S分子伴侣是如何被招募到分选平台的。使用蛋白质相互作用 2.剖析CI效应物被识别并递送至T3SA的分子机制。 3.研究是否存在共翻译ATP酶非依赖性III型分泌途径。 总之，所提出的研究不仅促进了我们对T3S效应器如何影响细胞的理解， 定义并递送到T3SA，而且还导致鉴定用于开发新的 靶向革兰氏阴性细菌病原体大家族的毒力的抗微生物剂， 毒力依赖于功能性T3SS。

The virulence of many human bacterial pathogens is dependent on transkingdom nanomachines, including type III secretion systems (T3SSs), which act to directly deliver tens of virulence proteins, often referred to as effectors, into the cytosol of mammalian cells. Many critical gaps exist in our understanding of how type III secreted (T3S) proteins, referred to as effectors, are defined and delivered to the T3S apparatus (T3SA). While each pathogen injects its own unique set of effectors into hosts, components of their machines share a high degree of similarity. For several decades, the dogma has been that the effector secretion is dependent on small acidic T3S chaperones that bind to their N-terminal regions. These chaperones control the hierarchy of secretion of proteins by mediating their recruitment to the sorting platform, a complex that cycles between the cytosol and membrane-embedded T3SA. Interestingly, cognate chaperones have not yet been identified for the majority of T3S effectors, including those from intensively studied Salmonella, Yersinia, Shigella and pathogenic Escherichia T3SSs. Here, we present data that support the existence of a noncanonical T3SS chaperone-independent (CI) pathway likely conserved across numerous phylogenetically distinct T3SS families. Here, using the Shigella flexneri T3SS as a model system, we propose to: 1. Determine how T3S chaperones are recruited to the sorting platform. Using the Protein Interaction 2. Dissect the molecular mechanisms by which CI effectors are recognized and delivered to the T3SA. 3. Investigate the existence of a co-translational ATPase-independent type III secretion pathway. Together the proposed studies shown not only advance our understanding regarding how T3S effectors are defined and delivered to the T3SA, but also result in the identification of targets for the development of novel antimicrobial agents that target the virulence of the large family of Gram-negative bacterial pathogens whose virulence is dependent on a functional T3SS.