Manipulation of the host NF-kappa B pathway by Toxopla

描述(申请人提供)：弓形虫是一种专性的细胞内原生动物寄生虫，可引起免疫缺陷个体的机会性疾病和新生儿的先天性疾病。弓形虫被广泛认为是地球上最成功的寄生虫之一，因为它的宿主范围广泛，并且能够在免疫能力强的人群中建立无症状的终生慢性感染。弓形虫用来避免被感染的宿主细胞破坏的策略之一是抑制细胞凋亡。候选人进行的研究表明，弓形虫通过依赖于核因子-kappa B上调抗凋亡基因，在感染细胞中诱导生存反应。值得注意的是，弓形虫通过一种不依赖于宿主I-kappa B激酶(Ikk)的非常规机制来激活NF-kappa B途径。此外，证据表明存在一种能够劫持和磷酸化I-kappa B的寄生虫衍生因子(S)。鉴定该因子(S)将有助于深入了解弓形虫对宿主细胞信号事件的调控，并揭示潜在的治疗靶点。这项拟议中的研究将应用生化和分子遗传学方法来表征弓形虫中假定的I-kappa B激酶的活性，并解决以下假设：“弓形虫通过一种可以独立于宿主ikk发挥作用的寄生虫编码因子(S)，通过招募和磷酸化I-kappa B来操纵宿主细胞的核因子-kappaB途径。”为了实现这一假设，申请者将：(1)确定一种能够在弓形虫亚细胞部分中磷酸化I-kappa B的寄生虫激酶的活性；以及(2)通过蛋白质组学和基因组分析确定弓形虫中具有I-kappa B激酶活性的候选蛋白。

DESCRIPTION (provided by applicant): Toxoplasma gondii is an obligate intracellular protozoan parasite, which causes opportunistic disease in immunodeficient individuals and congenital disease in newborns. T. gondii is widely regarded as one of the most successful parasites on earth because of its broad host range and capability to establish an asymptomatic life-long chronic infection in immunocompetent populations. One of the strategies used by T. gondii to avoid destruction by the infected host cell is the inhibition of apoptosis. Studies performed by the candidate have shown that T. gondii induces a survival response in infected cells via NF-kappa B-dependent up-regulation of anti-apoptotic genes. Remarkably, activation of the NF-kappa B pathway by T. gondii occurs through an unconventional mechanism, which is independent of the host I-kappa B kinase (IKK). In addition, the evidence suggests the presence of a parasite-derived factor(s) capable of hijacking and phosphorylating I-kappa B. Identification of this factor(s) would provide insight into the modulation of host cell signaling events by Toxoplasma and reveal potential therapeutic targets. The proposed studies in this proposal will apply biochemical and molecular genetic approaches to characterize the putative I-kappa B kinase activity in T. gondii and address the following hypothesis: "Toxoplasma gondii manipulates the NF-kappa B pathway of the host cell by recruiting and phosphorylating I-kappa B via a parasite encoded factor(s) that can function autonomously from host IKK." To fulfill this hypothesis, the applicant will: (1) determine the activity of a parasite kinase capable of phosphorylating I-kappa B in subcellular fractions of T. gondii; and (2) identify protein candidates in T. gondii with I-kappa B kinase activity by proteomic and genomic analyses.