Autophagy and Nod2 Function in Crohn's Disease

克罗恩病中的自噬和 Nod2 功能

• 批准号: 7845615
• 负责人: CHRISTINE L MCDONALD
• 金额: $ 38.86万
• 依托单位: CLEVELAND CLINIC LERNER COM-CWRU
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2014-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7845615
• 关键词: Acetylmuramyl-Alanyl-Isoglutamine; Anti-Bacterial Agents; Autophagocytosis; Bacteria; Binding; Cell Line; Cell Survival; Cell Wall; Cells; Chronic; Crohn' s disease; Data; Defect; Development; Disease; Disease susceptibility; Eating; Environmental Risk Factor; Etiology; Family; Figs - dietary; Genes; Genetic; Guanosine Triphosphate Phosphohydrolases; Immune; Immune response; Immune system; Immunity; Impairment; Individual; Inflammation Mediators; Inflammatory; Inflammatory Bowel Diseases; Lead; Link; Lysosomes; Modeling; Mutate; Mutation; Nucleotides; Nutrient; Organelles; Pathogenesis; Pathway interactions; Patients; Phagocytes; Play; Process; Production; Proteins; Recycling; Role; Signal Pathway; Signal Transduction; Starvation; Susceptibility Gene; Testing; Vacuole; antimicrobial; design; genome wide association study; microbial; novel; public health relevance; response; sensor

DESCRIPTION (provided by applicant): Crohn's disease (CD) is a chronic and debilitating inflammatory bowel disease with unknown etiology; however, it is clear that there are both genetic components as well as environmental factors that are required for its development. Tremendous advances have been made recently in understanding the genetics of CD. Although several chromosomal loci have been associated with IBD susceptibility, until last year, only one gene had been conclusively identified as a CD susceptibility gene. This gene is NOD2 (nucleotide-binding, oligomerization domain 2), which encodes an intracellular sensor of bacteria in the innate immune system. Recent genome-wide association scans have identified multiple, novel CD susceptibility genes. Many of these new CD susceptibility genes also modulate immune responses, suggesting that dysregulation of an immune pathway rather than a single gene may be important in CD pathogenesis. One of these processes is autophagy. Autophagy (literally "self-eating") is best known as a cell survival mechanism in response to starvation, where organelles are broken down and recycled to provide nutrients. This mechanism also plays a crucial role in the clearance of intracellular bacteria by the innate immune system. Bacteria and bacterial components induce autophagy, linking innate immune microbial sensors to autophagy. One of these microbial sensors is Nod2, which detects a specific component of the bacterial cell wall called muramyl dipeptide (MDP). Our preliminary data demonstrates that stimulation of cells with MDP not only activates autophagy, but suggests autophagy may also be involved in activation of Nod2 by MDP. These results provide a link between two separate classes of molecules mutated in CD and lead us to propose the following central hypothesis: CD- associated mutations in the autophagy genes, ATG16L1 (autophagy related 16-like protein 1) and IRGM (immunity-related GTPase family, M), and NOD2 impair the same critical innate immune pathway and impairment of this pathway contributes to CD pathogenesis. We hypothesize autophagy and Nod2 function together in two non-exclusive ways: (1) MDP stimulation of Nod2 activates autophagy as an essential anti-microbial response, and (2) autophagy is involved in MDP internalization and Nod2 activation. This hypothesis will be tested by the following three specific aims using both primary cells and cell lines: 1) Determine the role of Nod2 in activation of autophagy - is autophagy a component of Nod2 stimulated anti- microbial responses?, 2) Characterize the mechanism of MDP internalization - is it autophagy?, 3) Analyze alterations in autophagy in phagocytic cells of CD patients. The results of our proposed studies may benefit individuals with CD by identifying a crucial processes altered in CD, leading to the design and use of more specific CD therapies targeting this pathway. PUBLIC HEALTH RELEVANCE: Recent advances in the genetics of Crohn's disease (CD) indicate that alterations in an immune pathway rather than a single gene may be important in CD pathogenesis. We propose to study the interactions of three genes associated with CD susceptibility and define if they are a part of the same innate immune system pathway. The results of our proposed studies may benefit individuals with CD by identifying a crucial process altered in the disease, leading to the design and use of more specific therapies targeting this pathway.

描述（由申请人提供）：克罗恩病（CD）是一种病因不明的慢性、衰弱性炎症性肠病；然而，很明显，其发展既需要遗传成分，也需要环境因素。最近在了解 CD 遗传学方面取得了巨大进展。尽管多个染色体位点与 IBD 易感性相关，但直到去年，只有一个基因被最终确定为 CD 易感性基因。该基因是 NOD2（核苷酸结合寡聚结构域 2），编码先天免疫系统中细菌的细胞内传感器。最近的全基因组关联扫描已经鉴定出多个新型 CD 易感基因。许多新的 CD 易感基因也调节免疫反应，这表明免疫途径的失调而不是单个基因的失调在 CD 发病机制中可能很重要。这些过程之一是自噬。自噬（字面意思是“自食”）最出名的是一种响应饥饿的细胞生存机制，其中细胞器被分解并回收以提供营养。这种机制在先天免疫系统清除细胞内细菌方面也发挥着至关重要的作用。细菌和细菌成分诱导自噬，将先天免疫微生物传感器与自噬联系起来。其中一种微生物传感器是 Nod2，它可以检测细菌细胞壁的一种特定成分，称为胞壁酰二肽 (MDP)。我们的初步数据表明，用 MDP 刺激细胞不仅会激活自噬，而且表明自噬也可能参与 MDP 对 Nod2 的激活。这些结果提供了 CD 中突变的两类不同分子之间的联系，并引导我们提出以下中心假设：自噬基因 ATG16L1（自噬相关 16 样蛋白 1）和 IRGM（免疫相关 GTP 酶）中与 CD 相关的突变家族（M）和 NOD2 损害相同的关键先天免疫途径，并且该途径的损害导致 CD 发病机制。我们假设自噬和Nod2以两种非排他性的方式共同发挥作用：（1）Nod2的MDP刺激激活自噬作为一种重要的抗微生物反应，（2）自噬参与MDP内化和Nod2激活。该假设将使用原代细胞和细胞系通过以下三个具体目标进行检验：1) 确定 Nod2 在自噬激活中的作用 - 自噬是 Nod2 刺激的抗微生物反应的一个组成部分吗？ 2) 表征MDP 内化 - 是自噬吗？, 3) 分析 CD 患者吞噬细胞自噬的变化。我们提出的研究结果可能会通过确定 CD 中改变的关键过程而使 CD 患者受益，从而设计和使用针对该途径的更具体的 CD 疗法。公共卫生相关性：克罗恩病 (CD) 遗传学的最新进展表明，免疫途径的改变而不是单个基因的改变可能在克罗恩病发病机制中发挥重要作用。我们建议研究与 CD 易感性相关的三个基因的相互作用，并确定它们是否属于同一先天免疫系统途径的一部分。我们提出的研究结果可能会通过确定疾病中改变的关键过程而使克罗恩病患者受益，从而设计和使用针对该途径的更具体的疗法。