Subversion of Syndecan-1 Functions in Listeriosis

这项R21提案的主要目标是了解单核细胞增生李斯特菌（Lm）如何颠覆 多配体蛋白聚糖-1（syndecan-1，Sdc 1）的功能促进其发病。宿主-病原体相互作用在很大程度上决定了发病， 传染病的进展和结果。许多病原体，包括病毒、细菌和寄生虫， 在体外与硫酸乙酰肝素（HS）蛋白聚糖（HSPG）的HS部分结合，这种活性被认为是 在宿主细胞的附着和入侵中至关重要。然而，令人惊讶的是， 支持了HSP-病原体相互作用在体内微生物发病机制中的重要性。此外 HSPG在不同的细胞和组织中以不同的时间和水平表达，并且它们被认为是 HSPGs的功能特异，但促进附着和入侵的HSPGs的身份对于大多数人来说是未知的。 肝素结合病原体。此外，虽然HSPG是多功能分子，但大多数研究都是如此。 目前，研究人员只关注它们作为依恋/内化受体的作用，而在很大程度上忽视了它们可能 HSPGs在微生物致病机制中可能具有其他功能。我们的建议旨在解决这些问题 我们对细菌感染中HSPG生物学的理解存在差距，使用Lm作为肝素结合模型， 细菌病原体Lm是一种食源性革兰氏阳性细菌病原体，可引起一种罕见的 与高住院率和死亡率相关的重大传染病。初步研究 表明Sdc 1 null（Sdc 1-/-）小鼠对胃内和静脉内Lm的敏感性显著降低 与野生型（Wt）小鼠相比，在Sdc 3-/-或Sdc 4-/-小鼠中未观察到这种表型，表明 Sdc 1的消融导致特定的功能增益，使小鼠能够抵抗阿尔茨海默病。然而，SDC 1 不支持Lm附着或侵入宿主细胞，表明Sdc 1不促进发病 作为细胞表面Lm受体。相反，Sdc 1在细菌获得进入前抑制Lm的清除。 它的细胞内生态位。中性粒细胞和中性粒细胞胞外陷阱（NET）的大血管内聚集体 在Sdc 1-/-肝脏中形成嵌入有抗菌化合物的颗粒，其捕获并杀死Lm。Lm感染 诱导Sdc 1在Wt小鼠肝组织中脱落，这与肝细胞大小的减少直接相关。 血管内聚集的NET。此外，施用纯化的Sdc 1胞外域或DNA酶抑制了 血管内聚集的中性粒细胞和NET的形成，并显着增加肝脏细菌 Sdc 1-/-小鼠中的负荷。基于这些初步数据，该提案将探索Lm如何 诱导Sdc 1脱落（Aim 1）以及Sdc 1胞外域如何抑制淋病中的NET（Aim 2）。

The major goal of this R21 proposal is to understand how Listeria monocytogenes (Lm) subverts syndecan-1 (Sdc1) functions to promote its pathogenesis. Host-pathogen interactions largely dictate the onset, progression, and outcome of infectious diseases. Many pathogens, including viruses, bacteria and parasites, bind to the heparan sulfate (HS) moiety of HS proteoglycans (HSPGs) in vitro, and this activity is thought to be critical in the attachment and invasion of host cells. However, there are surprisingly very few examples supporting the importance of HSPG-pathogen interactions in microbial pathogenesis in vivo. Furthermore HSPGs are expressed in different cells and tissues at different times and levels, and they are thought to function specifically, but the identity of HSPGs that facilitate attachment and invasion is unknown for most heparin-binding pathogens. In addition, although HSPGs are multi-functional molecules, most studies have so far focused on their role as attachment/internalization receptors, and have largely overlooked the possibility that HSPGs may have other functions in microbial pathogenesis. Our proposal is designed to address these gaps in our understanding of HSPG biology in bacterial infections, using Lm as a model heparin-binding bacterial pathogen. Lm is a food-borne Gram-positive bacterial pathogen that causes listeriosis, a rare but significant infectious disease associated with a high rate of hospitalization and mortality. Preliminary studies showed that Sdc1 null (Sdc1-/-) mice are significantly less susceptible to both intragastric and intravenous Lm infection compared to wild type (Wt) mice. This phenotype is not seen in Sdc3-/- or Sdc4-/- mice, indicating that ablation of Sdc1 causes a specific gain of function that enables mice to resist listeriosis. However, Sdc1 does not support Lm attachment or invasion of host cells, indicating that Sdc1 does not promote pathogenesis as a cell surface Lm receptor. Instead, Sdc1 inhibits the clearance of Lm before the bacterium gains access to its intracellular niche. Large intravascular aggregates of neutrophils and neutrophil extracellular traps (NETs) embedded with antimicrobial compounds are formed in Sdc1-/- livers, which trap and kill Lm. Lm infection induces Sdc1 shedding in hepatic tissues of Wt mice, which is directly associated with the decrease in size of intravascular aggregated NETs. Furthermore, administration of purified Sdc1 ectodomains or DNase inhibits the formation of intravascular aggregated neutrophils and NETs and significantly increases the liver bacterial burden in Sdc1-/- mice. Based on these preliminary data, this proposal will explore key pathways of how Lm induces Sdc1 shedding (Aim 1) and how Sdc1 ectodomains inhibit NETs in listeriosis (Aim 2).