Dectin-1 Signaling Mechanisms

描述（由申请人提供）：Dectin-1是一种由骨髓吞噬细胞（如巨噬细胞和树突细胞）表达的先天性免疫受体，对于有效的宿主防御真菌感染至关重要。Dectin-1识别β-1，3-葡聚糖多糖，其构成真菌细胞壁干重的一半，并且受体的激活触发吞噬作用、杀微生物活性氧物质的产生和促炎细胞因子的宿主的产生。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，因此它已成为了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。我们以前已经表明，在结合到真菌细胞Dectin-1被集中到一个“吞噬突触”，允许激活炎症信号。我们进一步表明，Dectin-1信号传导导致吞噬体的形成，吞噬体招募LC 3，LC 3是一种众所周知的参与自噬的蛋白质，但其对传统吞噬体的作用尚不清楚。我们已经表明，LC 3招募到吞噬体增强了MHCII上这些隔室的抗原的加工和呈递，其他研究人员已经表明这些吞噬体更具杀微生物性。此外，我们和其他人已经观察到Dectin-1信号传导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。该信号需要CARD 9和半胱天冬酶-8活性，这似乎是Dectin-1所独有的特征。在这个项目中，我们将从三个方面来定义这个模型信号通路。在目标一中，我们将定义Dectin-1信号传导和LC 3影响吞噬体成熟的机制，以促进体外和体内抗原的有效呈递。在目标二中，我们将确定Dectin-1信号传导和吞噬作用导致激活不寻常的Card 9相关炎性体以产生炎性细胞因子的机制，并探索该过程在体外和体内免疫应答激活中的作用。在aim中 3我们将探讨“LC 3相关吞噬作用”和Card 9相关炎性小体激活在人类流行真菌病原体白色念珠菌和烟曲霉感染小鼠过程中的作用。

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.