Molecular mechanism of Mincle mediated NET formation:Implications for pneumonic sepsis

 描述（由申请人提供）：中性粒细胞协调对损伤或感染性损伤的早期免疫应答。中性粒细胞的抗微生物功能包括吞噬作用、脱粒作用和最近描述的中性粒细胞胞外陷阱或NET的形成。NET构成装饰有抗微生物蛋白/颗粒酶的去脱氧染色质原纤维，所述抗微生物蛋白/颗粒酶可以捕获和杀死细胞外微生物。肺部感染是脓毒症的主要原因，在全球范围内造成严重的医疗负担。越来越多的证据表明，异常的中性粒细胞功能和受损的能力，以消除感染的基础之一，炎症过度的特点，脓毒症。尽管有越来越多的证据表明NET在清除微生物和调节许多炎症性疾病的免疫应答方面具有有利的特性，但NET形成的病理生理相关性和分子机制尚未得到很好的理解。我们实验室最近的研究报告，在肺炎克雷伯氏菌（KPn）肺部感染引起的肺炎脓毒症期间，缺乏哺乳动物C型凝集素受体（C-type lectin receptor，C-Mincle）的Mincle-/-小鼠在其肺部表现出NET形成受损。此外，我们在此提供的初步数据显示，Mincle-/-中性粒细胞在响应于几种离体活化刺激的NET形成中存在缺陷，尽管它们能够以与野生型（WT）中性粒细胞相似的水平产生ROS（据报道对于NET形成是必需的）。相反，有缺陷的NET形成与Mincle-/-中性粒细胞自噬活化受损相关。这些令人兴奋的观察结果表明Mincle参与了自噬激活，并为理解导致NET形成的信号通路提供了机会。在这方面，我们发现siRNA敲低含有SH2结构域的衔接蛋白，信号淋巴细胞活化分子（SLAM）相关蛋白（SAP或SH2D1A）导致NET形成受损，并且SAP在活化的中性粒细胞中与Mincle形成复合物。这些新的观察结果使我们假设Mincle是嗜中性粒细胞介导的反应的关键组成部分，该反应通过SAP的信号传导调节自噬来驱动NET形成。为了检验这一假设，我们将采取以下具体目标：首先，我们将建立明克尔作为一个 NET形成的离体（在鼠骨髓嗜中性粒细胞中）和体内（在KPn感染的肺炎小鼠中）的中枢调节因子。我们将证明NET的形成依赖于Mincle介导的自噬及其与ROS的关系，这些自噬反应通过siRNA敲低或过表达以及Mincle-/-和WT中性粒细胞的过继转移来响应不同的刺激。第二，我们将阐明Mincle介导的自噬通路在NET形成中的作用，通过描述Mincle激活的自噬通路的分子组成部分，以及通过检查它们在WT、Mincle-/-和Mincle过度表达拯救的中性粒细胞中的表达和抑制作用来研究它们在NET形成中的参与。第三，我们将阐明一种新的Mincle/SAP轴自噬和NET的形成及其在小鼠和人类肺炎脓毒症的生物学相关性。在这里，我们将确定SAP可以促进自噬，从而促进NET的形成，并且Mincle提供了通过SAP信号传导诱导自噬和NET形成的上游信号。我们还将确定该途径在KPn诱导的肺炎性脓毒症的临床相关模型以及脓毒症患者中活化的后果。总之，该提议提出了一个新的概念，即Mincle通过SAP信号转导调节自噬来调节NET形成。这些研究一旦完成，将为精细调节NET形成提供新的靶点，以在脓毒症和可能的与缺陷性自噬和/或失调的NET形成相关的其他疾病状况中获得治疗益处。

 DESCRIPTION (provided by applicant): Neutrophils orchestrate early immune response to an injury or infectious insult. The antimicrobial functions of neutrophils constitute phagocytosis, degranulation and a recently described formation of Neutrophil Extracellular Traps or NETs. NETs constitute decondenesed chromatin fibrils decorated with antimicrobial proteins/granular enzymes that can trap and kill extracellular microbes. Pulmonary infections are a major cause of sepsis that poses a serious healthcare burden worldwide. Accumulating evidence implicates aberrant neutrophil function and an impaired ability to eradicate the infections as one of the underpinnings for hyperinflammation characteristic of sepsis. Despite accumulating evidence showing advantageous properties of NETs in clearance of microbes and in regulation of immune response in many inflammatory diseases, the pathophysiological relevance and molecular mechanisms underlying NET formation are not well understood. Recent studies from our lab have reported that Mincle-/- mice lacking a mammalian C-type lectin receptor (CLR) Mincle exhibit impaired NET formation in their lungs during pneumonic sepsis caused by pulmonary infection with Klebsiella pneumoniae (KPn). Further, our preliminary data presented here, shows that Mincle-/- neutrophils are defective in NET formation in response to several activation stimuli ex-vivo, despite their ability to produce ROS (reported to be essential for NET formation) at similar levels as wild-type (WT) neutrophils. Instead, the defective NET formation correlated with an impaired activation of autophagy in Mincle-/- neutrophils. These exciting observations implicated Mincle in autophagy activation and presented an opportunity to understand the signaling pathway that leads to NET formation. In this regard, we found that siRNA knockdown of an SH2 domain containing adaptor protein, Signaling lymphocyte-activation molecule (SLAM)-Associated Protein (SAP or SH2D1A) causes impaired NET formation and that SAP forms a complex with Mincle in activated neutrophils. These novel observations led us to hypothesize that Mincle is a critical component of neutrophil-mediated response that drives NET formation by regulating autophagy via signaling through SAP. To test this hypothesis we will undertake the following specific aims: First, we will establish Mincle as a central regulator of NET formation ex-vivo (in murine bone marrow neutrophils) and in-vivo (in KPn infected pneumonic mice). We will show that NET formation is dependent on Mincle-mediated autophagy and its relation with ROS in response to diverse stimuli by siRNA knockdown or overexpression and adoptive transfer of Mincle-/- and WT neutrophils. Second, we will elucidate Mincle mediated autophagy pathway in NET formation by delineating molecular components of autophagy pathway activated by Mincle and their involvement in NET formation by examining their expression and effect of inhibition in WT, Mincle-/- and Mincle rescued neutrophils by overexpression. Third, we will elucidate a novel Mincle/SAP axis in autophagy and NET formation and its biological relevance in murine and human pneumonic sepsis. Here we will establish that SAP can promote autophagy and hence the NET formation and that Mincle provides the upstream signal that induces autophagy and NET formation via SAP signaling. We will also determine the consequence of activation of this pathway in clinically relevant model of KPn induced pneumonic sepsis as well as in sepsis patients. Altogether this proposal puts forth a novel concept that Mincle regulates NET formation by modulating autophagy via signaling through SAP. These studies, when accomplished will provide novel targets for fine tuning the NET formation for therapeutic benefits in sepsis and likely other disease conditions that are associated with a defective autophagy and/or deregulated NET formation.