HSPGs in Ocular Surface Diseases

描述（由申请方提供）：微生物性角膜炎是一种威胁视力的感染性疾病，与显著的眼部发病率相关。据估计，全世界微生物角膜炎的年发病率约为500，000例，仅美国就有30，000例。眼表面通常适合微生物病原体居住，因为解剖学屏障阻碍微生物定殖，机械系统不断清除病原体，以及协调的防御反应，快速安装以有效根除入侵病原体。当这些机制中的一个或几个受到损害并且宿主-病原体相互作用的平衡转向有利于致病机制时，就会发生感染。因此，更好地了解宿主-病原体相互作用是一个主要的公共卫生优先事项，但细菌和宿主的机制，有助于微生物性角膜炎的发病机制是不完全了解。本申请的中心目标是确定syndecan- 1（一种主要的细胞表面硫酸肝素蛋白聚糖（HSPG））如何促进细菌性角膜炎的发病机制。Syndecan-1在角膜上皮中大量表达，但其在角膜中的功能仍不清楚。多配体蛋白聚糖-1作为细胞表面上的受体起作用，并且还作为细胞外环境中的可溶性HSPG起作用，因为其细胞外胞外域可以在某些病理条件下脱落。初步研究表明，syndecan-1缺陷的小鼠显著抵抗金黄色葡萄球菌的角膜感染，表明syndecan-1是促进金黄色葡萄球菌感染的重要宿主因子。金黄色角膜炎syndecan-1以这种方式发挥作用的潜在机制尚不清楚，但初步数据也表明S。金黄色葡萄球菌诱导角膜上皮细胞中的多配体蛋白聚糖-1脱落，并利用多配体蛋白聚糖-1胞外域的能力以硫酸肝素（HS）依赖性方式抵消嗜中性粒细胞介导的防御机制。基于这些数据，本建议将在3个特定目的中检验细菌对HSPG的颠覆是细菌性角膜炎发病机制中的重要毒力机制的总体假设。目的1将定义多配体蛋白聚糖-1脱落是如何在S.金黄色角膜炎目的2阐明多配体蛋白聚糖-1胞外结构域HS的结构特征，阐明其对S. Aim 3将确定syndecan-1胞外结构域如何抑制金黄色葡萄球菌角膜炎的生物学机制。嗜中性粒细胞对金黄色葡萄球菌的杀伤作用。拟议的研究将使用新的和已建立的遗传、生化和细胞生物学方法，结合细菌性角膜炎的体内模型。这些研究有望揭示角膜上皮HSPGs以前未知的生物学功能，并增加我们对细菌性角膜炎发病机制的分子和细胞过程的理解。

DESCRIPTION (provided by applicant): Microbial keratitis is a sight-threatening infectious disease associated with significant ocular morbidity. By one estimate, the annual incidence of microbial keratitis is approximately 500,000 patients worldwide and 30,000 patients in the US alone. The ocular surface is generally inhabitable for microbial pathogens because of anatomical barriers that impede microbial colonization, mechanical systems that constantly clear pathogens, and coordinated defense responses that are rapidly mounted to effectively eradicate invading pathogens. Infection occurs when one or several of these mechanisms are compromised and the balance of host-pathogen interactions shifts to favor pathogenic mechanisms. Thus, a better understanding of host-pathogen interactions is a major public health priority, but the bacterial and host mechanisms that contribute to the pathogenesis of microbial keratitis are incompletely understood. The central goal of this application is to define how syndecan- 1, a major cell surface heparin sulfate proteoglycan (HSPG), promotes the pathogenesis of bacterial keratitis. Syndecan-1 is abundantly expressed in the corneal epithelium, but much remains unknown of its functions in the cornea. Syndecan-1 functions as receptors on the cell surface and also as soluble HSPGs in the extracellular environment because its extracellular ectodomain can be shed under certain pathological conditions. Preliminary studies showed that mice deficient in syndecan-1 significantly resist corneal infection by Staphylococcus aureus, suggesting that syndecan-1 is an important host factor that promotes S. aureus keratitis. The underlying mechanisms of how syndecan-1 functions in this manner are not understood, but preliminary data also suggested that S. aureus induces syndecan-1 shedding in corneal epithelial cells and exploits the capacity of syndecan-1 ectodomains to counteract neutrophil-mediated defense mechanisms in a heparin sulfate (HS)-dependent manner. Based on these data, this proposal will examine the overall hypothesis that bacterial subversion of HSPGs is an important virulence mechanism in the pathogenesis of bacterial keratitis in 3 Specific Aims. Aim 1 will define how syndecan-1 shedding is induced in S. aureus keratitis. Aim 2 will elucidate the structural features of syndecan-1 ectodomain HS that promote S. aureus keratitis, and Aim 3 will determine the biological mechanism of how syndecan-1 ectodomains inhibit S. aureus killing by neutrophils. The proposed studies will use both novel and established genetic, biochemical, and cell biological approaches in conjunction with in vivo models of bacterial keratitis. The proposed studies are anticipated to uncover previously unknown biological functions of corneal epithelial HSPGs and to increase our understanding of molecular and cellular processes that are central to the pathogenesis of bacterial keratitis.