Regulation of proteins in the apical junctional complex by Citrobacter rodentium

描述（由申请人提供）： 这是我的第一个优异奖申请的第三次提交，目的是表征来自革兰氏阴性菌的大毒素的作用及其对体外和体内肠上皮屏障功能的作用。淋巴细胞抑制因子A（lifA）是革兰氏阴性菌中的一个大基因，存在于肠出血性大肠杆菌（EHEC）、肠致病性大肠杆菌（E.大肠杆菌和啮齿类柠檬酸杆菌。lifA已被确定为与EPEC引起的腹泻和由EHEC引起的溶血性尿毒症综合征具有最强统计学关联的单个基因。lifA编码与微生物发病机制有关的关键酶活性：1.6 kb的葡糖基转移酶基序。我们已经产生了新的稳定的，特定的框内插入-缺失突变失活这个主题。我们的初步数据表明，LS参与上皮屏障功能的分解。看来糖基转移酶活性通过阻止Cdc 42的活化而负责ZO-1和闭合蛋白从紧密连接（TJ）的解离。假设1：LS对于形成TJ的蛋白质的分解至关重要，导致细胞旁渗透性增加，促进细菌移位和系统性传播。目的1：探讨淋巴抑素葡萄糖基转移酶基序对肠上皮屏障功能的影响。此外，LS对TJ蛋白成员的影响似乎是通过引起Rho GT3活化的不平衡来介导的。我们表明，葡萄糖基转移酶参与Cdc 42途径的抑制。假设2：LS中存在的葡萄糖基转移酶活性通过调节Rho GT3 Cdc 42途径对TJ组分的分解至关重要。目的2：探讨C.啮齿动物lifA葡萄糖基转移酶基序对小GTdR Cdc 42信号级联的影响。最后，我们计划在动物模型中测试淋巴抑制素葡糖基转移酶活性与TJ完整性的相关性。假设3：LS诱导体内TJ分解，导致粘膜、粘膜下层和肠外器官的侵袭和定殖。目的3：探讨葡萄糖基转移酶基序对肠上皮屏障功能的影响机制。拟议的研究项目将有助于我们了解早期病理生理事件，阐明细菌如何在肠道感染过程中调节肠上皮屏障功能，并进入粘膜和粘膜下层，最终造成毁灭性的全身性后果。

DESCRIPTION (provided by applicant): This is the third submission for my first Merit Award application with the goal to characterize the effect of a large toxin from Gram negative bacteria and its effect on intestinal epithelial barrier function in vitro and in vivo. Lymphostatin (LS) is encoded by lymphocyte inhibitory factor A (lifA), a large gene present in Gram negative bacteria including Enterohemorrhagic (EHEC), Enteropathogenic E. coli, and Citrobacter rodentium. lifA has been identified as the single gene with the strongest statistical association with EPEC induced diarrhea and hemolytic-uremic syndrome caused by EHEC. lifA encodes for a critical enzymatic activity that have been implicated in microbial pathogenesis: a glucosyltransferase motif at 1.6 kb. We have generated new stable, specific in-frame insertion-deletion mutations inactivating this motif. Our preliminary data suggest that LS is involved in disassembly of epithelial barrier function. It appears that the glycosyltransferase activity is responsible for the dissociation of ZO-1 and occludin from tight junctions (TJs) by preventing activation of Cdc42. Hypothesis 1: LS is critical for the disassembly of proteins forming the TJs, resulting in increased paracellular permeability, promoting bacterial translocation and systemic dissemination. Aim 1: To define the mechanisms by which the lymphostatin glucosyltransferase motif impairs intestinal epithelial barrier function in vitro. Further, the effect of LS on TJs protein members appears to be mediated by causing an imbalance in Rho GTPase activation. We show that the glucosyltransferase is involved in inhibition of the Cdc42 pathway. Hypothesis 2: The glucosyltransferase activity present in LS is critical for the disassembly of TJs components by regulating Rho GTPase Cdc42 pathway. Aim 2: To investigate the effect of C. rodentium lifA glucosyltransferase motif on the small GTPase Cdc42 signaling cascade in vitro. Finally, we plan to test the relevance of lymphostatin glucosyltransferase activity for TJs integrity in an animal model. Hypothesis 3: LS induces disassembly of TJs in vivo, leading to invasion and colonization of mucosa, submucosa and extra-intestinal organs. Aim 3: To investigate the mechanism by which glucosyltransferase motif compromises intestinal epithelial barrier function in vivo. The proposed research project will contribute to our understanding of early pathophysiological events that clarify in how bacteria regulate intestinal epithelial barrier function during enteric infection and gain access to mucosa and submucosa with eventually devastating systemic consequences.