Dectin-1 Signaling Mechanisms

描述（由申请人提供）：Dectin-1是一种天然免疫受体，由骨髓吞噬细胞（如巨噬细胞和树突状细胞）表达，对宿主有效防御真菌感染至关重要。Dectin-1识别构成真菌细胞壁干重一半的-1,3-葡聚糖多糖，受体的激活触发吞噬作用，产生杀微生物活性氧，并产生大量促炎性细胞因子。Dectin-1是迄今为止被证明足以触发吞噬作用的少数受体之一，因此它已成为理解此类受体如何工作的重要模型。这个更新项目的重点是进一步了解Dectin-1信号传导的机制。我们之前已经证明，在与真菌细胞结合后，Dectin-1被浓缩成一个“吞噬突触”，允许炎症信号的激活。我们进一步表明，Dectin-1信号传导导致吞噬体的形成，并招募LC3， LC3是一种众所周知参与自噬的蛋白质，但其在传统吞噬体中的作用尚不清楚。我们已经证明LC3招募到吞噬体增强了MHCII上这些隔室抗原的加工和呈递，其他研究人员已经证明这些吞噬体具有更强的杀微生物能力。此外，我们和其他人已经观察到Dectin-1信号驱动炎性小体的激活，炎性小体是一种促进促炎细胞因子IL-1的加工和分泌的复合物。这个信号需要CARD9和caspase-8的活性，这些特征似乎是Dectin-1独有的。在本项目中，我们将从三个方面定义该模型信号通路。在第一个目标中，我们将定义Dectin-1信号和LC3影响吞噬体成熟的机制，以促进抗原在体外和体内的有效呈递。在目标二中，我们将确定Dectin-1信号传导和吞噬导致一种不寻常的card9相关炎症小体激活炎症细胞因子产生的机制，并探索这一过程在体外和体内免疫反应激活中的作用。在目标

DESCRIPTION (provided by applicant): Dectin-1 is an innate immune receptor expressed by myeloid phagocytes such as macrophages and dendritic cells that is essential for effective host defense against fungal infections. Dectin-1 recognizes the ¿-1,3-glucan polysaccharide that makes up as much as half the dry weight of fungal cell walls, and activation of the receptor triggers phagocytosis, production of microbicidal reactive oxygen species, and production of a host of pro- inflammatory cytokines. Dectin-1 is one of only a few receptors so far shown to be sufficient for triggering phagocytosis, and it has thus become an important model for understanding how such receptors work. This renewal project focuses on further understanding the mechanisms of Dectin-1 signaling. We have previously shown that upon binding to fungal cells Dectin-1 is concentrated into a "phagocytic synapse" that permits activation of inflammatory signaling. We have further shown that Dectin-1 signaling leads to formation of phagosomes that recruit LC3, a protein that is well-known to participate in autophagy, but its role on traditional phagosomes is less clear. We have shown that LC3 recruitment to phagosomes enhances processing and presentation of antigens from these compartments on MHCII, and other investigators have shown that these phagosomes are more microbicidal. In addition, we and others have observed that Dectin-1 signaling drives activation of the inflammasome, a complex that facilitates processing and secretion of the pro- inflammatory cytokine IL-1¿. This signal requires CARD9 and caspase-8 activity, features that appear to be unique to Dectin-1. In this project, we will define this model signaling pathway in three aims. In aim one, we will define the mechanisms by which Dectin-1 signaling and LC3 influence phagosome maturation in order to favor efficient presentation of antigens in vitro and in vivo. In aim two we will determine the mechanisms by which Dectin-1 signaling and phagocytosis lead to activation of an unusual Card9-related inflammasome for inflammatory cytokine production and explore the role of this process in activation of immune responses in vitro and in vivo. In aim 3 we will explore the role of "LC3-associated phagocytosis" and Card9-related inflammasome activation during infection of mice with the prevalent human fungal pathogens Candida albicans and Aspergillus fumigatus.