Regulation of Innate Immunity by Pyrin Proteins

描述(由申请人提供)：TLR和NLR家族成员对细胞外和细胞内病原体的识别启动了先天免疫和炎症反应。TLRs和NLRs都激活了NF-β和MAPK信号通路，导致多种炎性细胞因子(如TNF1、IL-6和IL-8)的转录和分泌。与TLRs不同，NLRs还可以激活多蛋白炎症体复合体，将proIL-12和proIL-18处理成活性形式。在不到五年的时间里，NLRs与遗传性自身炎症性疾病和对越来越多的病原体的先天性免疫反应有关，包括炭疽杆菌、鼠疫耶尔森菌和图拉氏方济各氏菌。炎症小体组装的结果是含有吡喃的NLR蛋白与ASC(带有卡片的凋亡斑点蛋白)相互作用，随后Caspase-1被招募和激活。炎性小体复合体也可能参与诱导某种形式的caspase-1依赖的细胞凋亡。ASC与NLRs和PYRIN蛋白的相互作用也可以激活NF-βB。最近，PYRIN ONLY蛋白(POPs)的发现同时影响了NLRs和炎症体的功能，为宿主调节促炎反应及其病原体颠覆提供了一条途径。这一建议的长期目标是了解仅依赖于吡咯蛋白的先天免疫反应的分子调控。此外，对炎症小体调节的理解将扩展到宿主与病原体的相互作用，在这些相互作用中，炎症小体的功能或颠覆被证明是免疫或疾病的关键。具体地说，我们已经确定了第二个人类POP(POP2)，它抑制NF-βp65的活性，与ASC相互作用，并阻止一些NLR激活的炎性小体的激活。我们将验证这一假设，即POP2通过干扰炎症体介导的caspase-1激活和减弱NF-β信号来负向调节促炎症反应，从而在先天性免疫反应中抑制有害的炎症反应，防止或减少巨噬细胞死亡。我们将结合广泛的分子和体内方法，解决以下目标：1)建立POP2抑制NF-B的分子基础；2)建立POP2调节炎性小体激活的分子基础。3)确定POP2在体内调节炎性先天免疫反应中的作用。公共卫生相关性：伤害或感染引起的炎症反应是对人类健康的重大威胁。我们建议研究一种名为POP2的小蛋白，它在炎症细胞中表达，可以调节导致炎症的细胞事件。因此，这项研究与广泛的炎症性疾病和条件有关，从感染到心血管疾病。

DESCRIPTION (provided by applicant): Extracellular and intracellular pathogen recognition by members of the TLR and NLR families initiate innate immune and inflammatory responses. TLRs and NLRs both activate the NF-?B and MAPK signaling pathways leading to the transcription and secretion of multiple inflammatory cytokines (e.g. TNF1, IL-6, and IL-8). Unlike TLRs, NLRs can also activate multiprotein inflammasome complexes that processes proIL-12 and proIL-18 to their active forms. In less than five years, NLRs have been linked to hereditary autoinflammatory diseases and innate immune response towards a growing number of pathogens, including Bacillus anthracis, Yersinia pestis, and Francisella tularensis. Inflammasome assembly results from interaction of a pyrin containing NLR protein with ASC (apoptotic speck protein with a CARD) followed by recruitment and activation of Caspase-1. The inflammasome complex may also be involved in inducing a form of caspase-1 dependent apoptosis. ASC interactions with NLRs and the protein Pyrin can also activate NF-?B. Recently, the discovery of pyrin only proteins (POPs) that influence both NF-?B and inflammasome functions has suggested an avenue for host regulation of the proinflammatory response and pathogen subversion thereof. The long-term objective of this proposal is to understand the molecular regulation of innate immune responses dependent upon pyrin only proteins. Further, understanding of inflammasome regulation will be extended to host-pathogen interactions where inflammasome function or subversion is demonstrated to be critical for immunity or disease. Specifically, we have identified a second human POP (POP2) which inhibits NF-?B p65 activity, interacts with ASC, and prevents the activation of a number of NLR activated inflammasomes. We will test the hypothesis that POP2 negatively regulates proinflammatory responses by interfering with both inflammasome-mediated caspase-1 activation and attenuating NF-?B signals, thus dampening harmful inflammation and preventing or reducing macrophage death during innate immune responses. Combining broad based molecular and in vivo approaches, we will address the following aims: 1) Establish the molecular basis for NF-?B inhibition by POP2 2) Establish the molecular basis for POP2 regulation of inflammasome activation. 3) Establish the in vivo role of POP2 in modulating inflammatory innate immune responses. PUBLIC HEALTH RELEVANCE: Inflammatory responses resulting from injury or infection are a significant threat to human health. We propose to study a small protein called POP2 which is expressed in inflammatory cells and can regulate cellular events leading to inflammation. This study is therefore relevant to a wide range of inflammatory diseases and conditions, ranging from infection to cardiovascular disease.