Mechanisms of peptidoglycan-induced modulation of metabolic and inflammatory responses to bacteria

摘要 吞噬细胞的免疫监视在通过内化细菌控制感染中起重要作用， 通过酶降解过程杀死它们。降解也会释放细菌分子， 先天性免疫受体和抗原最终呈递给适应性免疫系统 协调对微生物的整体免疫反应。革兰氏阳性菌的细胞壁， 金黄色葡萄球菌，主要由肽聚糖，一种氨基酸交联糖组成 聚合物的我们最近证明，在体内释放的单糖，n-乙酰葡糖胺， 肽聚糖降解是炎症性的。N-乙酰葡糖胺与糖酵解酶相互作用 己糖激酶，抑制其功能。因此，己糖激酶与线粒体外膜的相互作用 细胞膜被破坏，这种解离启动了负责细胞膜组装的信号级联反应。 多蛋白NLRP3炎性体复合物，其是激活蛋白酶半胱天冬酶-1所必需的。半胱天冬酶- 1负责裂解和激活几种关键的炎症细胞因子，包括IL-1b和 IL-18，对炎性细胞募集和活化很重要。我们的结果表明吞噬细胞 已经调整了它们正常的糖酵解调节，以感知异常高水平的细菌糖， 危险为了逃避免疫监视，细菌通过修饰肽聚糖层来抵抗降解， 吞噬细胞和限制先天性炎症信号，包括N-乙酰葡糖胺的可用性。 影响己糖激酶功能和糖酵解的N-乙酰葡糖胺的量将取决于转运 穿过吞噬体膜进入细胞质。初步证据表明，IL- 由吞噬细胞产生的1b，特别是对肽聚糖的反应，依赖于 糖转运蛋白GLUT家族。此外，我们已经产生了一种小鼠模型， 吞噬细胞表达的三种己糖激酶，并观察到对糖酵解的不同影响， 炎症反应。该建议旨在定义三种己糖激酶的作用， 吞噬细胞对革兰氏阳性菌肽聚糖的炎症反应，以及表征 肽聚糖衍生的N-乙酰葡糖胺的转运和对代谢的影响， 吞噬细胞的炎症反应。我们假设，炎症诱导的总体程度 由革兰氏阳性菌的数量和N-乙酰葡糖胺产生的可用性的影响 在细菌肽聚糖降解过程中，部分由于N-乙酰葡糖胺抑制糖酵解， 新陈代谢.

ABSTRACT Immune surveillance by phagocytic cells plays a vital role in controlling infections by internalize bacteria and kill them by a process of enzymatic degradation. Degradation also releases bacterial molecules that activate innate immune receptors and antigens for presentation to the adaptive immune system ultimately orchestrating the overall immune response to a microbe. The cell wall of gram-positive bacteria, like Staphylococcus aureus, is predominantly composed peptidoglycan, an amino acid-crosslinked sugar polymer. We recently demonstrated that the monomeric sugar, n-acetylglucosamine, released during peptidoglycan degradation, is inflammatory. N-acetylglucosamine interacts with the glycolytic enzyme hexokinase, inhibiting its function. As a consequence, hexokinase’s interaction with the mitochondrial outer membrane is disrupted and this dissociation initiates a signaling cascade responsible for assembly of the multi-protein NLRP3 inflammasome complex necessary for activation of the protease caspase-1. Caspase- 1 is responsible for the cleavage and activation of several key inflammatory cytokines, including IL-1b and IL-18, important for inflammatory cell recruitment and activation. Our results suggest that phagocytic cells have adapted their normal glycolytic regulation to sense abnormally high levels of a bacterial sugar as danger. To evade immune surveillance, bacteria modify their peptidoglycan layer to resist degradation by phagocytic cells and limiting the availability of innate inflammatory signals, including n-acetylglucosamine. The amount of n-acetylglucosamine impacting hexokinase function and glycolysis will depend on transport across the phagosomal membrane into the cytosol. Preliminary evidence suggests that the amount of IL- 1b produced by phagocytic cells, specifically in response to peptidoglycan, is dependent on the function of the GLUT family of sugar transports. In addition, we have generated a mouse model deficient for one of the three hexokinases expressed by phagocytic cells and observed differential impacts on glycolysis and inflammatory responses. This proposal aims to define the roles of the three hexokinases expressed by phagocytic cell in the inflammatory response to gram-positive bacteria peptidoglycan, as well characterize the transport and impact of peptidoglycan-derived n-acetylglucosamine on the metabolism and inflammatory responses of phagocytic cells. We hypothesize that the overall degree of inflammation induced by gram-positive bacteria is impacted by the amount and availability of n-acetylglucosamine generating during bacterial peptidoglycan degradation due in part to n-acetylglucosamine’s inhibition of glycolytic metabolism.