Bacterial Invasion and Trafficking within the Bladder

描述（申请人提供）：尿路致病性大肠杆菌（UPEC）菌株是尿路感染（uti）的主要病原体，一直是最常见的传染病之一。UPEC可以侵入宿主膀胱上皮细胞并随后繁殖，形成类似生物膜的大细胞内包涵体。另外，细胞内UPEC可以在更安静、不复制的状态下维持在低水平，这可能是慢性和复发性急性uti的储存库。越来越多的证据表明，UPEC进入尿路内的宿主细胞和组织可以促进细菌在面对先天和适应性宿主防御以及抗生素治疗时的持久性。几乎所有的UPEC分离株都编码被称为1型毛的丝状粘附细胞器。我们发现1型菌毛粘附素FimH可以以非规范的方式与宿主1321整合素受体结合，从而激活信号级联反应，导致UPEC依赖于动作蛋白的内化。我们的初步数据表明，fimh介导的细菌入侵宿主细胞依赖于肌动蛋白和微管细胞骨架网络之间的串扰，尽管这种串扰的性质尚不明确。进入过程也需要网格蛋白和不同的网格蛋白相关连接蛋白的输入。网格蛋白在吸收小分子（如生长因子）中的作用是其最好的特征，但其促进更大颗粒（如UPEC和其他侵入性病原体）内化的能力直到最近才被认识到，并且仍然知之甚少。本应用程序的主要目的是确定介导UPEC侵袭膀胱上皮细胞的宿主因子，重点关注微管-肌动蛋白串扰和网格蛋白的功能作用。宿主细胞入侵对宿主内UPEC的建立和持续的影响也将被评估。希望这项工作将提供对急性、复发性和慢性尿路感染发病机制的更全面的了解，最终促进治疗和预防这些异常常见感染的改进治疗方法的发展。

DESCRIPTION (provided by applicant): Strains of uropathogenic Escherichia coli (UPEC) are the principal causative agents of urinary tract infections (UTIs), which continuously rank among the most common of infectious diseases. UPEC can invade host bladder epithelial cells and subsequently multiply, forming large intracellular inclusions that resemble biofilms. Alternately, intracellular UPEC can persist at low levels in a more quiescent, non-replicating state that may serve as a reservoir for chronic and recurrent acute UTIs. Mounting evidence indicates that UPEC entry into host cells and tissues within the urinary tract promotes bacterial persistence in the face of both innate and adaptive host defenses, as well as antibiotic treatments. Virtually all UPEC isolates encode filamentous adhesive organelles called type 1 pili. We have found that the type 1 pilus adhesin FimH can engage host 1321 integrin receptors in a non-canonical fashion and thereby activate signaling cascades that result in the actin-dependent internalization of UPEC. Our preliminary data indicate that FimH-mediated bacterial invasion of host cells is dependent upon crosstalk between the actin and microtubule cytoskeletal networks, although the nature of this crosstalk remains undefined. The entry process also requires input from clathrin and distinct clathrin-associated adaptor proteins. Clathrin is best characterized for its role in the uptake of small molecules such as growth factors, but its ability to promote internalization of much larger particles like UPEC and other invasive pathogens has only recently been appreciated and remains poorly understood. The primary objectives of this application are to define the host factors that mediate UPEC invasion of bladder epithelial cells, with a focus on the functional roles of microtubule-actin crosstalk and clathrin. The impact that host cell invasion has on the establishment and persistence of UPEC within the host will also be assessed. It is hoped that the proposed work will provide a more complete understanding of the pathogenesis of acute, recurrent, and chronic UTIs, ultimately facilitating the development of improved therapeutics for treating and preventing these exceptionally common infections.