Role of STIM1 in E. coli Pneumonia

描述（由申请人提供）：大肠杆菌（E. coli）是院内肺炎的主要原因之一。此外，有糖尿病、酒精中毒和慢性阻塞性肺病等基础疾病的患者也可能是社区获得性大肠杆菌肺炎。尽管不适当的炎症宿主反应在肺炎的发病机制中起着核心作用，但这种疾病发展的确切分子机制仍然知之甚少。钙稳态的改变被认为在炎症中起重要作用。虽然大多数免疫细胞使用的提高细胞内钙的主要机制是储存操作的Ca2+进入（SOCE），其中内质网（ER） Ca2+储存的消耗触发细胞外Ca2+的涌入，但SOCE激活的直接分子基础是未知的，直到最近鉴定基质相互作用分子1 （STIM1）作为关键的ER Ca2+传感器。然而，STIM1和SOCE在体内炎症反应、感染免疫和其他免疫相关疾病中的意义仍然很大程度上未知。利用Cre重组酶- loxp系统，我们最近产生了骨髓细胞中编码STIM1的基因特异性缺失的小鼠（STIM1-/-）。我们的初步数据表明，与WT小鼠（STIM1+/+）相比，STIM1缺乏显著降低了大肠杆菌诱导的支气管肺泡灌洗液（BAL）中IL-6、KC、IL-1b和MCP-1水平和肺中性粒细胞积聚。此外，大肠杆菌刺激的STIM1-/-小鼠显示肺转录因子CCAAT/增强子结合蛋白（C/EBP）激活显著降低（主要是C/EBP -）。我们进一步表明，STIM1与免疫细胞中SOCE的重要Ca2+通道Orai1和TRPC1相互作用。基于这些研究，我们假设STIM1通过与Orai1、TRPC1等信号分子相互作用，在肺对大肠杆菌的炎症反应和宿主对大肠杆菌肺炎的防御中发挥重要的调节作用。因此，本探索性研究旨在确定STIM1在大肠杆菌诱导的肺泡炎中的作用及其潜在的分子机制。为了验证我们的假设，提出了两个具体目标。在第一个目标中，我们将确定STIM1在肺部对抗大肠杆菌感染中的作用。在第二个目标中，我们将阐明STIM1在大肠杆菌肺炎中功能的分子机制。我们的研究结果有望为STIM1在肺部对细菌的炎症反应中的调节作用提供重要的新信息。这一知识将代表一个新的范式接近开发新的治疗靶点治疗肺炎。

DESCRIPTION (provided by applicant): Escherichia coli (E. coli) is one of the major causes of nosocomial pneumonia. Moreover, E. coli pneumonia may also be community-acquired in patients who have underlying disease such as diabetes mellitus, alcoholism, and chronic obstructive pulmonary disease. Although inappropriate inflammatory host responses play a central role in the pathogenesis of pneumonia, the precise molecular mechanisms underlying the development of this disorder remain poorly understood. Altered calcium homeostasis is considered to play an important role in inflammation. Although the predominant mechanisms to raise intracellular calcium used by most immune cells is store-operated Ca2+ entry (SOCE) whereby the depletion of endoplasmic reticulum (ER) Ca2+ stores triggers the influx of extracellular Ca2+, the direct molecular basis of SOCE activation was unknown until the recent identification of stromal interaction molecule 1 (STIM1) as the critical ER Ca2+ sensor. However, the significance of STIM1 and SOCE in in vivo inflammatory responses, immunity to infection, and other immune-related diseases remains largely unknown. Using the Cre recombinase-loxP system, we recently generated mice with specific deletion of the gene encoding STIM1 in myeloid cells (STIM1-/-). Our preliminary data indicate that STIM1 deficiency significantly reduced E. coli-induced IL-6, KC, IL-1b, and MCP-1 levels in bronchoalveolar lavage (BAL) fluids and neutrophil accumulation in the lung compared to WT mice (STIM1+/+). Furthermore, E. coli-stimulated STIM1-/- mice showed significantly reduced lung transcription factors CCAAT/enhancer-binding proteins (C/EBPs) activation (mainly C/EBP�). We further show that STIM1 interacts with Orai1 and TRPC1, important Ca2+ channels for SOCE in immune cells. Based on these studies, we hypothesize that STIM1 plays an important regulatory role in lung inflammatory responses to E. coli and host defense against E. coli pneumonia by interacting with Orai1, TRPC1, and other signaling molecules. Therefore, this exploratory study is designed to define the roles of STIM1 in E. coli- induced pulmonary alveolitis and the underlying molecular mechanisms. Two specific aims are proposed to test our hypothesis. In the first aim, we will determine the role of STIM1 in the lungs against E. coli infection. In the second aim, we will elucidate the molecular mechanisms of STIM1 function in the E. coli pneumonia. The results of our studies are expected to provide important novel information on the regulatory roles of STIM1 in the lung inflammatory responses to bacteria. This knowledge will represent a new paradigm for approaching the development of novel therapeutic targets for treatment of pneumonia.