HSPGs in Alpha-toxin-induced Tissue Injury

细菌病原体精心制作了各种各样的毒素，破坏宿主组织的稳态。毒素 可直接破坏宿主细胞，但有几种通过失调宿主反应增强毒力， 炎性组织损伤。此外，在许多传染病中，越来越多的证据表明， 病原微生物的定殖引发疾病，但疾病进展主要由病原微生物介导。 宿主对感染的反应失调这项R21提案的中心目标是探索乙酰肝素 硫酸蛋白多糖（HSPGs）调节宿主对金黄色葡萄球菌α-毒素（一种外毒素）的反应 与许多葡萄球菌疾病有关的毒力因子。我们在初步研究中发现syndecan-1 null（Sdc 1-/-）小鼠在鼻内（i.n.）与 S.金黄色葡萄球菌α毒素Syndecan-1是肺II型上皮细胞的主要细胞表面HSPG，α-毒素 是S.金黄色肺炎重要的是，肺损伤表型是 被拯救的I. N施用纯化的多配体蛋白聚糖-1胞外域、硫酸乙酰肝素（HS）或硫酸化的HS 片段，但不被硫酸软骨素（CS）、缺乏HS和CS链的核心蛋白或低硫酸化HS 片段，表明syndecan-1 HS中的硫酸化结构域保护免受α-毒素诱导的肺损伤。 然而，使syndecan-1 HS以这种方式发挥作用的关键结构特征和其分子机制是不确定的。 syndecan-1在α-毒素诱导的肺损伤中的生物学靶点尚不清楚。该项目将填补这些 通过精确定义HS硫酸化代码，使Sdc 1能够突出和具体地 抑制α-毒素诱导的肺损伤（目的1），并通过探索Sdc 1与先天免疫相互作用的作用， 细胞和细胞因子在宿主对α-毒素反应失调中的作用。最终目标是提供一个 HSPGs在毒素诱导的肺损伤中的分子、糖生物学和细胞基础 开发细菌性肺炎的新诊断和治疗方法。

Bacterial pathogens elaborate a diverse array of toxins that disrupt the homeostasis of host tissues. Toxins can directly damage host cells, but several enhance virulence by dysregulating the host response and causing inflammatory tissue injury. Furthermore, in many infectious diseases, accumulating evidence suggests that colonization of pathogenic organisms instigates disease, but disease progression is largely mediated by the dysregulated host response to infection. The central goal of this R21 proposal is to explore how heparan sulfate proteoglycans (HSPGs) modulate the host response to Staphylococcus aureus α-toxin, an exotoxin virulence factor implicated in many staphylococcal diseases. We found in preliminary studies that syndecan-1 null (Sdc1-/-) mice show significantly increased inflammatory lung injury when challenged intranasally (i.n.) with S. aureus α-toxin. Syndecan-1 is the major cell surface HSPG of type II epithelial cells in the lung, and α-toxin is an established virulence factor for S. aureus pneumonia. Importantly, the lung injury phenotypes were rescued by i.n. administration of purified syndecan-1 ectodomains, heparan sulfate (HS) or sulfated HS fragments, but not by chondroitin sulfate (CS), core protein devoid of HS and CS chains or low sulfated HS fragments, indicating that sulfated domains in syndecan-1 HS protect against α-toxin-induced lung injury. However, the critical structural features that enable syndecan-1 HS to function in this manner and the biological target of syndecan-1 in α-toxin-induced lung injury are unknown. This project will fill these mechanistic gaps by precisely defining the HS sulfation code that enables Sdc1 to prominently and specifically inhibit α-toxin-induced lung injury (aim 1), and by exploring the role of Sdc1 interactions with innate immune cells and cytokines in the dysregulated host response to α-toxin. The culminating goal is to provide a molecular, glycobiological, and cellular basis for HSPGs in toxin-induced lung injury for the translational development of new diagnostics and therapeutics for bacterial pneumonia.