Role of fascin1 in dendritic cell-mediated immunity against listeria infection

描述(由申请人提供)：本R03申请的目标是在体内确定SENOG1在基于树突状细胞(DC)的免疫中的作用，以对抗单核细胞增多性李斯特菌(Lm)的感染。树突状细胞是最强大的抗原提呈细胞，在先天免疫和获得性免疫中发挥核心作用。当DC遇到病原体时，它们会经历称为成熟的终末分化：它们聚集许多面纱样膜突起，从周围组织移动到引流淋巴结，并将抗原递送给幼稚的T细胞。Fascin1是DC中一种独特的肌动蛋白捆绑蛋白，因为它在DC成熟时被大量和特异地诱导。Fascin1在未成熟的DC或其他血细胞包括巨噬细胞、中性粒细胞和自然杀伤细胞中均不存在，这表明在成熟的DC生物学中，Fezin1具有特定的作用。事实上，我们和其他人已经证明，SENCE1对于成熟相关的功能至关重要，包括肌动蛋白细胞骨架的大规模重组，树突状细胞向引流淋巴结的趋化迁移，T细胞的激活和免疫突触的组装。我们发现，通过对Socor1 KO DC的特征分析，它在DC介导的宿主防御系统中扮演着一个新的角色。有报道称，树突状细胞比巨噬细胞具有更强的细胞内杀伤活性。这种对LM的抵抗被认为是DC主要的抗原提呈功能的关键：DC必须在外围感染后存活，然后移动到引流淋巴结，将抗原信息传递给T细胞。我们发现Enzor1 KO DC对LM介导的杀伤表现出更高的敏感性。重要的是，JONSE1高表达的DC对LM感染具有极强的抵抗力。我们进一步发现，Socor1使被LM包裹的吞噬小体更具酸性，并增加了自噬通量。这些结果表明，SENCE1促进了吞噬小体和自噬小体的溶酶体融合以清除细菌，这解释了为什么DC(SENCE1阳性)比巨噬细胞(SENCE1阴性)更具抵抗力。然而，一个关键的问题仍然有待回答：在体内，基于DC的获得性和先天免疫对于抵抗LM感染是至关重要的吗？我们将通过使用LM小鼠模型来检查ZONECT 1 KO小鼠是否对LM感染表现出适应性和先天免疫反应减弱。该提案可能会提供重要信息，帮助我们开发新的基于DC的针对细菌感染的免疫疗法。 公共卫生相关性：阐明SENSE1在抵抗单核细胞增多性李斯特菌(Lm)感染的先天和获得性免疫中的体内作用，可能会对我们理解宿主对细胞内病原体的防御产生革命性的影响。表达Fascin1的树突状细胞(DCs)通过控制LM和其他病原体的细胞内增殖，有望有效地将病原体信息传递给T细胞，从而清除细菌病原体。因此，我们认为表达Socor1基因的树突状细胞(DCs)可用于DC免疫治疗。

DESCRIPTION (provided by applicant): The goal of this R03 application is to determine in vivo roles of fascin1 in dendritic cell (DC)-based immunity against infection of Listeria monocytogenes (Lm). DCs, the most potent antigen presenting cells, play central roles in both innate and acquired immunity. When DCs encounter pathogens, they undergo terminal differentiation called maturation: they assemble numerous veil-like membrane protrusions, travel from the peripheral tissues to draining lymph nodes, and present antigens to naive T-cells. Fascin1 is a unique actin-bundling protein in DCs because it is greatly and specifically induced upon DC maturation. Fascin1 is absent in immature DCs or in other blood cells including macrophages, neutrophils and natural killer cells, suggesting a specific role for fascin1 in DC biology upon maturation. Indeed, we and others have demonstrated that fascin1 is critical for the maturation-associated functions including massive reorganization of the actin cytoskeleton, chemotactic migration of DCs into draining lymph nodes, T-cell activation and assembly of the immunological synapse. We have found, by characterizing fascin1 KO DCs, that fascin1 plays a novel role in a DC-mediated host defense system. It has been reported that DCs show a stronger intracellular killing activity toward Lm than do macrophages. This resistance to Lm is thought to be crucial for the DCs primary function of antigen presentation: DCs must survive infection at the periphery and then move to draining lymph nodes for transferring antigen information to T-cells. We found that fascin1 KO DCs displayed higher susceptibility to Lm-mediated killing. Importantly, DCs with high fascin1 expression was extremely resistant to Lm infection. We further found that fascin1 made Lm-encapsulated phagosomes more acidic, and increases autophagy flux. These results indicate that fascin1 increases lysosomal fusion of both phagosomes and autophagosomes for bacterial clearance, explaining why DCs (fascin1-positive) are more resistant than macrophages (fascin1-negative). However, a key question remains to be answered: Is fascin1 crucial for DC-based adaptive and innate immunity against Lm infection in vivo? We will examine, by using the Lm mouse model, whether fascin1 KO mice show reduced adaptive and innate immune responses to Lm infection. The proposal is likely to provide vital information that will help us develop new DC-based immunotherapy against bacterial infection. PUBLIC HEALTH RELEVANCE: The elucidation of the in vivo role of fascin1 in innate and adaptive immunity against Listeria monocytogenes (Lm) infection could have a transformative effect on our understanding of host defense toward intracellular pathogens. Fascin1-expressing dendritic cells (DCs), by controlling intracellular proliferation of Lm and possibly other pathogens, are expected to effectively transfer pathogen information to T-cells, thereby leading to clearance of bacterial pathogens. We suggest that fascin1-expressing dendritic cells (DCs) could thus be utilized in DC-based immunotherapy.