A role of osteopontin in innate immunity against fungal infection

描述（由申请人提供）：机会性真菌感染是免疫功能低下个体严重发病和死亡的常见原因，包括艾滋病患者、化疗下的癌症患者和免疫抑制移植患者。机会性真菌感染的一个关键诱发因素是适应性免疫受损。然而，在缺乏适应性免疫的情况下，我们发现骨桥蛋白（OPN）在防御机会性真菌肺囊虫（肺囊虫肺炎，PCP）中起关键作用。这一发现表明，先天免疫本身可以在抵抗真菌方面产生显著差异。以前的一些研究表明，OPN参与抗真菌免疫，但其机制尚不清楚。虽然OPN已被研究为细胞外分子（分泌的OPN； sOPN），但我们的初步数据强烈表明，一种新的细胞内OPN异构体（iOPN）是OPN介导的抗真菌反应的主要参与者。本研究的目的是阐明OPN保护免疫功能低下的宿主免受肺囊虫感染的机制。为了实现这一目标，我们将在本提案中验证以下中心假设：iOPN通过参与真菌模式识别受体（PRR）簇的形成以及作为细胞质适配蛋白从受体转导信号来增强抗真菌先天免疫。在这里，我们将追求以下具体目标：（Aim 1）阐明iOPN参与真菌PRR簇形成的机制；（Aim 2）阐明iOPN在真菌PRR信号转导中发挥作用的机制；（Aim 3）确定表达iOPN的dc和巨噬细胞是否增强真菌清除。在目标1和目标2中，我们将使用生化和细胞生物学方法来阐明iOPN如何参与真菌检测时的细胞反应。在目标3中，我们将使用体外和体内方法来测试iOPN介导的肺囊虫清除。本研究的成功完成将对宿主病原识别的研究领域产生重要的积极影响。OPN是一种被充分研究的蛋白质，但过去几乎所有关于OPN的研究都集中在sOPN上。因此，了解新型OPN亚型iOPN的生物学特性对免疫学领域具有重要意义。此外，本研究的结果将有助于更好地理解天然免疫检测真菌的分子机制。

DESCRIPTION (provided by applicant): Opportunistic fungal infection is a common cause of serious morbidity and mortality in immunocompromised individuals, including AIDS patients, cancer patients under chemotherapy, and immunosuppressed transplant recipients. A key predisposing factor for opportunistic fungal infections is impaired adaptive immunity. However, in the absence of adaptive immunity, we found that osteopontin (OPN) plays a critical role in defense against an opportunistic fungus, Pneumocystis, which causes Pneumocystis pneumonia (PCP). The finding suggested that innate immunity alone can make a significant difference in resistance against fungi. Involvement of OPN in anti-fungal immunity was suggested by several previous studies, but the mechanism is not known. Although OPN has been studied as an extracellular molecule (secreted OPN; sOPN), our preliminary data strongly suggested that a novel intracellular OPN isoform (iOPN) is the main player in OPN-mediated anti-fungal responses. The goal of this proposed research is to elucidate the mechanism by which OPN protects immunocompromised hosts from Pneumocystis infection. To achieve the goal, we will test the following central hypothesis in this proposal: iOPN enhances anti-fungal innate immunity, and it does so by participating in forming fungal pattern recognition receptor (PRR) clusters and in transducing signals from the receptors as a cytoplasmic adaptor protein. Here, we will pursue the following specific aims: (Aim 1) Elucidate the mechanism by which iOPN participates in fungal PRR cluster formation, (Aim 2) Elucidate the mechanism by which iOPN plays a role in signal transduction of fungal PRRs, and (Aim 3) Determine whether fungal clearance is enhanced by DCs and macrophages that express iOPN. In Aim 1 and 2, we will use biochemical and cell biological approaches to elucidate how iOPN is involved in cellular responses upon fungal detection. In Aim 3, we will use in vitro and in vivo approaches to test the iOPN- mediated clearance of Pneumocystis. Upon successful completion, our study will have an important positive impact on the research field of pathogen recognition by hosts. OPN is a well-studied protein, but virtually all the studies of OPN in the past focused on sOPN. Thus, understanding the biology of iOPN, a novel OPN isoform, has a great impact on the field of immunology. Furthermore, results from this study will provide better understanding in molecular mechanisms of fungal detection by innate immunity.