Mobilization of lysosome anti-microbial defenses by the unfolded protein response

描述（申请人提供）：专业吞噬细胞在抗微生物防御中起着至关重要的作用。通过吞噬作用对微生物的吸收导致形成一个动态的囊泡室，称为吞噬溶酶体。吞噬酶体在物理和功能上定义了微生物与宿主细胞的关键分离，使宿主能够在这个有限的空间内靶向降解抗微生物机制。我们发现细菌感染触发未折叠蛋白反应（UPR），这是一种与内质网应激和先天免疫功能相关的细胞程序。UPR的激活增加了细胞降解蛋白质的能力，但这种降解的机制尚不完全清楚。我们的初步研究表明，细菌感染期间UPR的激活导致耐甲氧西林金黄色葡萄球菌（MRSA）与降解溶酶体腔室和细菌杀死的相关性增加。抑制特定的UPR调节因子导致与溶酶体的关联减少和MRSA杀伤减少。该建议的中心假设是，吞噬细胞中UPR的激活导致吞噬溶酶体网络的运输和降解能力增加，从而增强降解，从而增强抗微生物功能。为了验证这一假设，我们将(1)在UPR激活时使用物理和功能标记测量溶酶体网络的动员；(2)明确UPR传感器、Ire1、ATF6和PERK在感染过程中响应先天免疫信号调节溶酶体转运和功能的特定方面的作用。普遍定期审议对细胞降解能力的调节是细胞对蛋白质产生或分泌的扰动作出反应的基本策略。我们的研究现在强调了upr介导的降解和抗微生物功能之间的新联系，并将确定形成巨噬细胞抗微生物武器库的关键药物靶点，以开发抗感染策略。

DESCRIPTION (provided by applicant): Professional phagocytes play a critical role in anti-microbial defense. Uptake of microbes by phagocytosis results in the formation of a dynamic vesicular compartment, termed the phagolysosome. The phagolysosome physically and functionally defines a critical separation of the microbe from the host cell, allowing the host to target degradative anti-microbial mechanisms to this confined space. We find that bacterial infection triggers the unfolded protein response (UPR), a cellular program associated with ER stress and innate immune function. Activation of the UPR increases the capacity of the cell to degrade proteins, but the mechanisms responsible for this degradation are incompletely understood. Our preliminary studies suggest that UPR activation during bacterial infection results in increased association of methicillin resistant Staphylococcus aureus (MRSA) with the degradative lysosomal compartment and bacterial killing. Inhibition of specific UPR regulators results in decreased association with lysosomes and decreased MRSA killing. The central hypothesis of this proposal is that activation of the UPR in phagocytes results in increased trafficking and degradative capacity of the phagolysosomal network, leading to enhanced degradative, and thus anti-microbial, function. To test this hypothesis, we will (1) measure mobilization of the lysosomal network using physical and functional markers upon activation of the UPR; (2) define the role of the UPR sensors, Ire1, ATF6 and PERK in regulating specific aspects of lysosomal trafficking and function in response to innate immune signals during infection. Regulation of the degradative capacity of the cell by the UPR is a fundamental strategy by which cells can respond to perturbations in the production or secretion of proteins. Our studies now highlight a novel connection between UPR-mediated degradation and anti-microbial function, and will define key druggable targets that shape the macrophage anti-microbial arsenal for development of anti-infective strategies. PUBLIC HEALTH RELEVANCE: Virulent pathogens may evade host-antimicrobial defenses and are a major cause of morbidity and mortality worldwide. Our studies have revealed a fundamental cellular stress response that broadly enhances host defense, increasing killing of bacteria such as methicillin-resistant Staphylococcus aureus by immune cells. These findings highlight a new mechanism for anti-microbial defense that may provide potential targets for development of anti-infective therapies.