The role of curli fibrils in modulating immune responses in the gut

描述（由申请人提供）：淀粉样蛋白是具有保守的纤维状交叉折叠四元结构的蛋白质沉积物。在人类中产生超过60种不同的淀粉样蛋白。虽然这些蛋白质中的一些蛋白质的功能已被证实，包括胰岛淀粉样多肽和几种肽激素，但许多其他淀粉样蛋白的作用仍然未知。有趣的是，很少有细菌能产生淀粉样蛋白。在包括大肠杆菌在内的肠道细菌的生物膜中发现卷曲纤维 和肠道沙门氏菌血清型。鼠伤寒杆菌是迄今为止最具特征的细菌淀粉样蛋白。最近，我们发现Toll样受体（TLR）2识别<$-淀粉样蛋白1-42（一种宿主淀粉样蛋白）和卷曲淀粉样蛋白纤维，因为它们具有保守的共同<$-折叠结构（19，20）。此外，我们和其他人证明了TLR 2与TLR 1的二聚化对于识别戊型淀粉样蛋白1-42和卷曲淀粉样蛋白纤维是必要的（21）。由肠上皮细胞表达的TLR 2有助于调节肠屏障功能（5）。尽管如此，淀粉样蛋白对肠上皮屏障的影响仍然未知。通过这种应用，我们将研究细菌和宿主淀粉样蛋白对肠道免疫反应的贡献。我们的中心假设是，通过TLR 2/TLR 1复合物检测淀粉样蛋白在肠上皮中产生保护性免疫应答，从而通过激活PI 3 K途径加强肠上皮屏障。这反过来又导致了 紧密连接蛋白增加。我们将用浮游生物E检验我们的假设。coli Nissle，以及纯化的卷曲纤维和血清淀粉样蛋白A1（SAA 1），一种炎症时肠道中产生的宿主淀粉样蛋白。拟议研究的基本原理是，更好地了解尼氏卷曲纤维或宿主淀粉样蛋白SAA促进上皮屏障功能的机制，将有助于更好地了解免疫系统在稳态和炎症过程中如何调节肠上皮屏障。

DESCRIPTION (provided by applicant): Amyloids are protein deposits that possess a conserved fibrillar cross-¿ sheet quartenary structure. More than 60 different amyloidogenic proteins are produced in humans. While the function of few of these proteins has been demonstrated including, islet-amyloid polypeptide and several peptide hormones, the role of many other amyloids remain unknown. Interestingly, few bacteria have been shown to produce amyloids. Curli fibers found in the biofilms of enteric bacteria including Escherichia coli and Salmonella enterica serovar. Typhimurium are the best-characterized bacterial amyloid to date. Recently, we discovered that Toll-like receptor (TLR) 2 recognizes both ¿-amyloid 1-42, a host amyloid, and curli amyloid fibers due to their conserved common ¿-sheet structure (19, 20). Moreover, we and others demonstrated that the dimerization of TLR2 with TLR1 is necessary for the recognition of ¿-amyloid 1-42 and curli amyloid fibers (21). TLR2 expressed by the intestinal epithelial cells contribute to the regulation of the intestinal barrier function (5). Nonetheless, the affects of amyloids on the intestinal epithelial barrier remain unknown. With this application we will investigate the contribution of bacterial and host amyloids to intestinal immune responses. Our central hypothesis is that the detection of amyloids via the TLR2/TLR1 complex generates a protective immune response in the gut epithelium leading to reinforcement of the intestinal epithelial barrier via activation of the PI3K pathway. This, in turn, leads to an increase in tight junction proteins. We will test our hypothesis using the commensal organism E. coli Nissle, as well as purified curli fibers and serum amyloid A1 (SAA1), a host amyloid produced in the gut upon inflammation. The rationale for the proposed research is that a better understanding of the mechanisms by which curli fibers of Nissle or host amyloid SAA promote epithelial barrier function will lead to a better mechanistic understanding of how intestinal epithelial barrier is regulated by the immune system during homeostasis and inflammation.