Autophagy and Nod2 Function in Crohn's Disease

克罗恩病中的自噬和 Nod2 功能

基本信息

批准号：
8587008
负责人：
CHRISTINE L MCDONALD
金额：
$ 0.1万
依托单位：
CLEVELAND CLINIC LERNER COM-CWRU
依托单位国家：
美国
项目类别：
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

项目摘要

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.

克罗恩病（CD）是一种慢性且令人衰弱的炎症性肠病，病因未知。然而，显然，遗传成分既有遗传成分又有环境因素发展。最近在理解CD的遗传学方面已取得了巨大进步。尽管几个染色体基因座与IBD敏感性有关，但直到去年，只有一个基因最终被鉴定为CD敏感性基因。该基因是NOD2（核苷酸结合，寡聚结构域2），它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鉴定出多个新型CD易感基因。其中许多新的CD敏感性基因还调节免疫反应，表明免疫失调途径而不是单个基因在CD发病机理中可能很重要。这些过程之一是自噬。自噬（从字面上是“自我吃”）是响应于响应的细胞存活机制饥饿，细胞器分解并回收以提供营养。这种机制也发挥了先天免疫系统在清除细胞内细菌中的关键作用。细菌和细菌组件诱导自噬，将先天免疫微生物传感器与自噬联系起来。这些微生物之一传感器是NOD2，它检测到称为Muramyl二肽（MDP）的细菌细胞壁的特定成分。我们的初步数据表明，用MDP刺激细胞不仅激活自噬，而且激活建议自噬也可能参与MDP激活NOD2。这些结果提供了联系 CD中突变的两种单独的分子类别，并导致我们提出以下中心假设：CD- 自噬基因，ATG16L1（自噬相关16种蛋白1）和IRGM的相关突变（与免疫相关的GTPase家族，M），NOD2损害了同样的关键先天免疫途径和该途径的损害有助于CD发病机理。我们假设自噬和nod2 通过两种非排他性的方式一起功能：（1）NOD2的MDP刺激激活自噬作为必不可少的抗微生物反应，（2）自噬参与MDP内在化和NOD2激活。这假设将通过以下三个特定目的使用原代细胞和细胞系进行检验：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？，2）表征MDP内在化机制 - 是自噬吗？，3）分析 CD患者吞噬细胞自噬的改变。我们提出的研究的结果可能会受益通过识别CD中的关键过程来改变CD的个体，导致设计和使用更多针对此途径的特定CD疗法。