One-carbon metabolism and immune cell function in tuberculosis

摘要结核病的免疫代谢为控制这一致命疾病提供了新的机遇。 传染病。我们和其他人在多种动物模型中描述了免疫代谢的变化 发现对HIF-1介导的Warburg效应的代谢重塑是对 结核病的病原体--结核分枝杆菌感染。最近，使用多种方法 包括代谢组学和转录图谱，我们确定了新的核心代谢途径，这些途径在 结核分枝杆菌感染的M1样巨噬细胞和小鼠肺内。这些包括谷氨酰胺分解和一碳 新陈代谢。一碳代谢分解丝氨酸衍生的一碳(1C)单位转移到 产生四氢叶酸甲酯(THF)中间体，然后用于核苷酸合成和 甲硫氨酸循环中的甲基化反应。一碳代谢也参与氧化还原平衡。 通过产生NADH/NADPH和甘氨酸和半胱氨酸来合成谷胱甘肽(GSH)。我们也 发现抑制亚甲基四氢叶酸脱氢酶2(MTHFD2)会导致M1样蛋白减少 极化，包括线粒体功能失调和mTORC1/ATF4信号在M1- 就像巨噬细胞。MTHFD2是由Mthfd2编码的一碳代谢的关键线粒体酶， 在结核分枝杆菌感染的M-样巨噬细胞和小鼠肺中高度诱导。基于这些观察，我们 假设线粒体MTHFD2介导的一碳代谢参与代谢重塑 通过为核苷酸合成和甲基化反应生成1C单位来激活免疫细胞的程序， 以及降低当量和GSH以实现氧化还原动态平衡。因为结核病经常与缺乏联系在一起 对于1C载体THF的前体叶酸，我们还假设在结核分枝杆菌期间叶酸缺乏 感染抑制一碳代谢，导致激活、分化和效应器功能减弱 宿主免疫细胞。此外，由于体内MTHFD2的升高与炎症性疾病的严重程度有关， 我们进一步假设，一碳代谢的长时间和高表达有助于肺 结核分枝杆菌感染慢性期的病理学。为了检验我们的假设，在目标1中，我们将描绘MTHFD2是如何- 介导的单碳代谢调节类M1巨噬细胞的免疫代谢特性， 线粒体生物学，丝氨酸代谢途径，以及Mthfd2上调的机制。在目标2中，我们将 建立髓系细胞和T细胞系中缺乏Mthfd2的条件性KO小鼠品系以描述其影响 Mthfd2缺乏对疾病进展和免疫细胞和/或亚群的免疫代谢特性的影响。 在目标3中，我们将使用易感结核病的小鼠模型来评估叶酸饮食对 表达宿主免疫以控制结核分枝杆菌感染。我们还将确定抑制剂的治疗作用。 在慢性感染阶段的抗结核治疗中以单碳代谢为目标。我们的研究是 有望推动急需的宿主导向疗法(HDTS)的发展，以增强 免疫细胞清除结核分枝杆菌感染和/或防止病理发展。

Abstract The immunometabolism of tuberculosis (TB) offers new opportunities for controlling this deadly infectious disease. We and others have characterized the immunometabolic changes in multiple animal models of TB and found that metabolic remodeling to the HIF-1-mediated Warburg effect is a general response to infection by Mycobacterium tuberculosis, the causative agent of TB. Recently, using multiple approaches that include metabolomics and transcriptomic profiling, we identified novel core metabolic pathways that are found in both Mtb-infected M1-like macrophages and in mouse lungs. These include glutaminolysis and one-carbon metabolism. One-carbon metabolism catabolizes the transfer of serine-derived one-carbon (1C) units to generate methyl-tetrahydrofolate (THF) intermediates that are then utilized for nucleotide synthesis and for methylation reactions through the methionine cycle. One-carbon metabolism is also involved in redox balancing through the generation of NADH/NADPH and of glycine and cysteine for glutathione (GSH) synthesis. We also found that inhibition of methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) leads to diminished M1-like polarization that includes dysregulated mitochondrial function and dampened mTORC1/ATF4 signaling in M1- like macrophages. MTHFD2 is a key mitochondrial enzyme of one-carbon metabolism that is encoded by Mthfd2, which is highly induced in Mtb infected M-like macrophages and mouse lungs. Based on these observations, we hypothesize that mitochondrial MTHFD2-mediated, one-carbon metabolism contributes to metabolic remodeling programs of activating immune cells by generating 1C units for nucleotide synthesis and methylation reactions, as well as reducing equivalents and GSH for redox homeostasis. Since TB is often associated with a deficiency of folic acid, the precursor of the 1C carrier THF, we also hypothesize that folic acid deficiency during Mtb infection dampens one-carbon metabolism, leading to diminished activation, differentiation, and effector function of host immune cells. Moreover, since elevated MTHFD2 in vivo is associated with inflammatory disease severity, we further hypothesize that prolonged and elevated expression of one-carbon metabolism contributes to lung pathology at the chronic stage of Mtb infection. To test our hypothesis, in Aim 1, we will delineate how MTHFD2- mediated, one-carbon metabolism regulates immunometabolic properties of M1-like macrophages, mitochondrial biology, serine metabolic pathways, and the mechanism of Mthfd2 upregulation. In Aim 2, we will generate conditional KO mouse strains lacking Mthfd2 in myeloid cells and T cell lineage to delineate the impact of Mthfd2 deficiency on disease progression and immunometabolic properties of immune cells and/or subsets. With Aim 3, we will use a susceptible mouse model of TB to evaluate the effects of folic acid dietary intake on the expression of host immunity to control Mtb infection. We will also define the therapeutic role of inhibitors targeting one-carbon metabolism during anti-TB treatment at chronic stages of the infection. Our study is expected to advance the development of urgently needed host-directed therapies (HDTs) to enhance the ability of immune cells to clear Mtb infection and/or to prevent the development of pathology.