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

资助金摘要 许多人类细菌病原体的毒力取决于跨王国的纳米机器，包括类型 III分泌系统(T3SS)，它直接输送数十种毒力蛋白，通常被称为 效应器进入哺乳动物细胞的胞浆。在我们对第三类的理解中存在许多关键的差距 分泌的(T3S)蛋白被称为效应器，被定义并递送到T3S装置(T3SA)。而当 每种病原体向宿主体内注入一组独特的效应器，它们机器的组件共享高 相似程度。几十年来，人们一直认为效应器的分泌依赖于少量的 与其N-末端区域结合的酸性T3S伴侣。这些伴侣控制着分泌物的层次结构 通过调节蛋白质向分选平台的募集，分选平台是一种在胞质和胞浆之间循环的复合体 膜包埋T3SA。有趣的是，大多数同源伴侣还没有被确定。 包括来自沙门氏菌、耶尔森氏菌、志贺氏菌和致病性沙门氏菌的T3S效应因子 Escherichia T3SS.在这里，我们提供的数据支持非规范T3SS伴侣的存在- 独立(CI)途径可能在许多不同的T3SS家族中保守。在这里，使用 福氏志贺氏菌T3SS作为模式系统，我们建议： 1.确定如何将T3S监护人招募到分拣平台。 2.剖析CI效应被识别并传递到T3SA的分子机制。 3.研究是否存在共翻译的非依赖ATPase的III型分泌途径。 总之，拟议的研究表明，不仅提高了我们对T3效应器如何 定义并交付给T3SA，但也导致确定小说发展的目标 针对革兰氏阴性细菌大家族的毒力的抗菌剂，其 毒力依赖于功能正常的T3SS。

Abstract of funded grant 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. 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.