Bacterial amyloids: interactions with DNA and pathogenicity

总结 淀粉样蛋白是具有保守的β折叠结构的复杂蛋白质。细菌利用淀粉样蛋白 来装饰它们生物膜的细胞外基质，高度结构化的多细胞群落。 Curli是由肠道细菌表达的淀粉样蛋白，包括鼠伤寒沙门氏菌和沙门氏菌。 大肠埃希菌我们的研究小组已经表明卷曲淀粉样纤维也被TLR 2/1识别 NLRP 3炎性小体。这一发现具有广泛的相关性，因为淀粉样蛋白的检测 由先天免疫系统驱动的阿尔茨海默病和朊病毒疾病的发病机制。 最近的一项研究表明，人工形成的淀粉样蛋白可以在体外结合DNA 这种复合物在小鼠体内引发自身免疫反应。由于生物膜细胞外基质 天然含有淀粉样蛋白和DNA，我们探索了这两种分子之间的相互作用， 并确定在生物膜形成过程中释放的细菌DNA被不可逆地掺入 卷曲纤维表达curli或纯化curli/DNA复合物的细菌引发自身免疫性疾病 体内反应。 本申请的主要目的是阐明细菌通过其引起细胞凋亡的机制。 淀粉样蛋白被免疫系统识别，导致其在宿主中的致病作用。 我们的中心假设是细菌淀粉样蛋白/DNA复合物是致病分子， 通过进入多个细胞区室并参与多个模式识别 受体，包括TLR 2、TLR 9和NLRP 3，导致炎症和自身免疫 应答我们期望，拟议研究的成功完成将确定 细菌淀粉样蛋白作为一种新的强大的病原体相关分子模式（PAMP）， 通过多种受体被免疫系统识别，并建立一种新的范式， 表达淀粉样蛋白的细菌感染不仅是SLE的主要环境诱因， 也适用于其他几种复杂的人类疾病。

Summary Amyloids are complex proteins with a conserved beta sheet structure. Bacteria use amyloids to decorate the extracellular matrix of their biofilms, highly structured multicellular communities. Curli are amyloids expressed by enteric bacteria, including Salmonella Typhimurium and Escherichia coli. Our group has shown that curli amyloid fibers are recognized by TLR2/1 as well as the NLRP3 inflammasome. This finding is of broad relevance, because detection of amyloids by the innate immune system drives the pathogenesis of Alzheimer's disease and prion diseases. A recent study demonstrated that an artificially formed amyloid protein can bind DNA in vitro and this complex elicits an autoimmune response in mice. Since the biofilm extracellular matrix naturally harbors amyloids and DNA, we explored the interactions between these two molecules and determined that bacterial DNA released during biofilm formation was irreversibly incorporated into curli fibers. Bacteria expressing curli or purified curli/DNA complex triggered autoimmune responses in vivo. The primary objective of this application is to elucidate the mechanism by which bacterial amyloids are recognized by the immune system, leading to their pathogenic effects in the host. Our central hypothesis is that bacterial amyloid/DNA complexes are pathogenic molecules that act by accessing multiple cellular compartments and engaging several Pattern Recognition Receptors, including, TLR2, TLR9 and NLRP3 resulting in inflammation and autoimmune responses. It is our expectation that successful completion of the proposed studies will identify bacterial amyloids as a novel powerful Pathogen-Associated Molecular Pattern (PAMP) that is recognized by the immune system via multiple receptors and establish a new paradigm that infections with amyloid-expressing bacteria are major environmental triggers not only for SLE but also for several other complex human diseases.