Toxoplasma proteins that modulate the host cell

 描述（由申请方提供）：弓形虫是一种专性细胞内寄生虫，可导致免疫抑制患者和胎儿严重疾病以及其他健康个体视力丧失。宿主先天免疫的激活对于早期发现 弓形虫，但先天免疫反应的过度激活也可导致病理性炎症。在上一个资助期间，我们已经确定，在检测到弓形虫感染时，炎性小体的激活是一种重要的先天免疫防御机制。在这次更新申请中，我们将确定弓形虫激活炎性小体和NFκB转录因子的分子机制，这对激活先天免疫很重要。炎性小体是参与白细胞介素（IL）-1 β和IL-18产生的多蛋白复合物，这些细胞因子在对许多病原体（包括弓形虫）的免疫应答中起重要作用。炎性小体激活还可以诱导一种称为焦亡的快速细胞死亡形式，其可以去除细胞内病原体复制所需的小生境。有两种信号参与活性IL-1 β的分泌：1）转录因子NFκB的激活，导致IL-1 β原的表达; 2）细胞溶质受体（称为NLR）检测微生物和环境危险信号，导致其与caspase-1原沿着多聚化（统称为炎性体）。当炎性小体组装时，胱天蛋白酶原-1被自动催化加工，并且可以诱导焦亡，但也切割IL-18原和IL-18原，导致其随后的分泌。弓形虫在其棒状体和致密颗粒细胞器中分别分泌一种名为ROP和GRA的效应分子，以与宿主细胞共适应。我们已经确定弓形虫GRA 15可以激活NFkB通路，从而提供信号1。我们还发现弓形虫激活了刘易斯大鼠NLRP 1-炎性小体，从而导致焦亡和抑制弓形虫生长。除了炭疽致命毒素，弓形虫是唯一已知的NLRP 1-炎性体的其他激活剂。因此，重要的是要确定宿主和寄生虫的蛋白质，决定弓形虫-炎性体的相互作用。在我们的第一个目标中，我们将确定弓形虫GRA 15调节NFκB转录因子的确切机制。在我们的第二个目标中，我们将集中于识别参与弓形虫炎性体激活的寄生虫分子。这些先天性免疫反应在决定人类对弓形虫病的易感性方面发挥作用，并且对于防御许多其他病原体很重要。这项研究的结果将有助于更好地理解弓形虫-先天免疫系统的相互作用，并将为NLRP 1的激活提供新的见解。这将有助于开发针对弓形虫病和其他致病性疾病的改进治疗方法。

 DESCRIPTION (provided by applicant): Toxoplasma gondii is an obligate intracellular parasite that can cause serious disease in immune-suppressed patients and fetuses and vision loss in otherwise healthy individuals. Activation of host innate immunity is crucial for early detection of Toxoplasma but an over-activation of innate immune responses can also lead to pathological inflammation. During the previous funding period we have determined that activation of the inflammasome upon detection of Toxoplasma infection is an important innate immune defense mechanism. In this renewal application we will identify the molecular mechanisms by which Toxoplasma activates the inflammasome and the NFκB transcription factor, which is important for activating innate immunity. Inflammasomes are multiprotein complexes that participate in the production of interleukin (IL)-1ß and IL-18, which are cytokines that play important roles in the immune response to many pathogens, including Toxoplasma. Inflammasome activation can also induce a form of rapid cell death known as pyroptosis, which can remove the niche that intracellular pathogens need for replication. There are two signals involved in the secretion of active IL-1ß: 1) the activation of the transcription factor NFκB, which leads to the expression o pro-IL-1ß and 2) the detection of microbial and environmental danger signals by cytosolic receptors (named NLRs) leading to their multimerization along with pro-caspase-1 (together called the inflammasome). Pro-caspase-1 is auto catalytically processed when the inflammasome is assembled and can induce pyroptosis but also cleave pro-IL-1ß and pro-IL-18 leading to their subsequent secretion. To co-opt the host cell, Toxoplasma secretes effector molecules named ROPs and GRAs from its rhoptry and dense granule organelles, respectively. We have determined that Toxoplasma GRA15 can activate the NFkB pathway and thereby provide signal 1. We have also shown that Toxoplasma activates the Lewis rat NLRP1-inflammasome, which leads to pyroptosis and inhibition of Toxoplasma growth. Besides Anthrax lethal toxin, Toxoplasma is the only known other activator of the NLRP1-inflammasome. It is therefore important to identify the host and parasite proteins that determine Toxoplasma-inflammasome interactions. In our first aim we will determine the exact mechanism by which Toxoplasma GRA15 modulates the NFκB transcription factor. In our second aim we will focus on identifying the parasite molecules involved in inflammasome activation by Toxoplasma. These innate immune responses play a role in determining human susceptibility to toxoplasmosis, and are important for defense against numerous other pathogens. Results from this research should lead to a better understanding of Toxoplasma-innate immune system interactions and will provide novel insights into NLRP1 activation in general. This will help the development of improved treatments against toxoplasmosis and other pathogenic diseases.