Molecular Analysis of Trypanosome Infection

描述（由申请人提供）：克氏锥虫是一种血液和组织寄生虫，影响数百万人，造成重大的人类发病率和死亡率。对参与克氏锥虫感染第一步的关键表面分子的作用的基本了解可能为治疗提供新的靶点。我们的长期目标是了解允许克氏锥虫感染哺乳动物细胞并引起疾病的分子机制，以便开发针对克氏锥虫感染的特定分子干预策略。本应用程序的目的是确定哪些宿主细胞受体介导克氏锥虫与哺乳动物细胞结合，当受体介导的信号通路有助于感染。这一应用的假设是，T. cruzi gp83是一种寄生虫用来附着在哺乳动物细胞上的配体分子，它与哺乳动物宿主细胞的凝集素样氧化低密度脂蛋白受体（LOX-1）结合，介导锥虫附着，从而激活导致初始感染和发病的信号事件。我们基于强有力的初步结果提出了这一假设，表明通过基因捕获或RNAi沉默LOX-1基因来中断LOX-1基因可以抑制克氏锥虫与细胞的结合和感染，而细胞中LOX-1的过表达会导致锥虫过度附着于细胞并增加感染。我们的研究结果也支持了这一假设，表明gp83特异性地与LOX-1结合，并且我们已经确定了gp83和LOX-1上的关键区域，这些区域相互作用，明显地介导了T.克氏体的附着，导致寄生虫进入。

DESCRIPTION (provided by applicant): Trypanosoma cruzi is a blood and tissue parasite that affects millions of individuals causing significant human morbidity and mortality. Basic understanding of the role of the critical surface molecules that participate in the first step of T. cruzi infection may provide novel targets for therapy. Our long-range goal is to understand the molecular mechanisms that allow T. cruzi to infect mammalian cells and cause disease, so that specific molecular intervention strategies can be developed against T. cruzi infection. The objective of this application is to identify which host cell receptors mediate T. cruzi binding to mammalian cells, when receptor-mediated signaling pathways contribute to infection. The hypothesis of this application is that T. cruzi gp83, a ligand molecule that the parasite uses to attach to mammalian cells, binds to the lectin-like oxidized low-density lipoprotein receptor (LOX-1) of mammalian host cells to mediate trypanosome attachment, thereby activating signaling events leading to initial infection and pathogenesis. We have formulated this hypothesis based on strong preliminary results, showing that interruption of LOX-1 gene by gene trapping or silencing LOX-1 gene by RNAi inhibits T. cruzi binding to cells and infection, whereas over-expression of LOX-1 in cells causes over-attachment of trypanosomes to cells and increased infection. Supporting also this hypothesis are our findings showing that gp83 specifically binds to LOX-1 and that we have identified critical regions on gp83 and LOX-1 that interact with each other to apparently mediate T. cruzi attachment leading to parasite entry. We will test our central hypothesis by pursuing the following specific aims: (1) to determine the structural-function relationships of the LOX-1-gp83 interaction; (2) to determine the LOX-1- dependent signaling pathways that mediate trypanosome gp83-dependent infection; and (3) to determine the in vivo role of the LOX-1 gene in the process of T. cruzi infection and pathogenesis using a novel LOX-1 knock out mouse model and a novel transgenic mouse model over-expressing LOX-1. Mutations, deletions and substitutions in critical regions of LOX-1 and gp83 will be performed to identify the motifs in each interacting molecule involved in T. cruzi binding to cells. Computational modeling of the trypanosome gp83 and the interacting peptide loop from the extracellular domain of LOX-1 will be determined. The mechanism underlying the novel gp83-LOX-1 signal transduction pathway leading to regulation of laminin ?-1 expression and infection will be elucidated using LOX-1(-/-) cells and LOX(+/+) cells. We will use our novel mouse models that over-express LOX-1 or that are null for LOX-1 expression to provide definitive in vivo tools to understand the other complementary mechanisms that contribute to trypanosome infection (in the LOX-1 null animals) and the mechanisms by which LOX-1 mediates infection (in the over-expressing animals).