Role of lipid rafts and phosphoinositides in E. histolytica virulence

描述(申请人提供)：溶组织内阿米巴是阿米巴痢疾和肝脓肿的病原体。它在全球致病原因中排名第三，并被列为B类生物恐怖主义制剂。因此，了解这种病原体的生物学并开发创新的检测和治疗策略是当务之急。溶组织型滋养体在感染过程中会遇到多种宿主细胞和大分子。据推测，这些胞外成分触发了寄生虫中的信号级联，从而导致毒力的变化。随着信号通路组件在溶组埃希菌中被发现的速度，新的挑战是理解这些细胞中信号事件的时间和空间调节。在其他真核生物中，脂筏(富含胆固醇和鞘磷脂的质膜结构域)与肌动蛋白细胞骨架和磷脂酰肌醇(PI)一起，将质膜中的信号事件划分为不同的区域。最近发现，溶组织乳杆菌细胞具有RAFT样质膜结构域。RAFT与一个重要的信号/黏附分子--半乳糖/N-乙酰氨基半乳糖(Gal/GalNAc)凝集素的共存表明，RAFT也可能参与了溶组织性肠杆菌的信号转导。在拟议的研究中，将探索溶组织性肠杆菌脂筏以及几种PI的生物学作用。在第一个目标中，将研究RAFT和肌动蛋白之间的关系，以及它们在毒力中的作用。在第二个目标中，将利用突变的遗传学方法评估脂筏、囊泡运输和肌动蛋白之间的联系，在这些突变中，这些细胞成分是解偶联的。最后，在第三个目标中，将研究Pis在寄生虫毒力功能中的作用。这将通过检测PI 3-激酶和PTEN磷酸酶的功能来实现，这两种酶在基于PI的信号转导中具有互补作用。由于囊泡运输，肌动蛋白的细胞骨架重排和信号可能调节毒力；这些研究将有助于了解溶组织埃希氏菌的致病性。公共卫生描述：溶组织内阿米巴是阿米巴痢疾和肝脓肿的致烧剂，在因寄生虫病而死亡的人数中排名世界第三。由于它也被归类为生物恐怖主义制剂，因此了解其毒性具有更高的优先级。这项拟议的研究将检查寄生虫与宿主相互作用期间激活的信号通路。由于信号可能调节毒力，这些研究将对了解溶组织埃希氏菌的生物学意义重大。

DESCRIPTION (provided by applicant): Entamoeba histolytica is the causative agent of amoebic dysentery and liver abscess. It ranks third as a worldwide cause of morbidity and has been classified as a Category B bioterrorism agent. Therefore, there is elevated priority to understand the biology of and develop innovative detection and therapeutic strategies for this pathogen. E. histolytica trophozoites will encounter a variety of host cells and macromolecules during infection. It is postulated that these extracellular components trigger signaling cascades in the parasite that lead to changes in virulence. With the rate at which the components of signaling pathways are being discovered in E. histolytica, the new challenge is to understand the temporal and spatial regulation of signaling events in these cells. In other eukaryotes, lipid rafts (cholesterol- and sphingolipid-rich plasma membrane domains), along with the actin cytoskeleton, and phosphoinositides (Pis), compartmentalize signaling events in the plasma membrane. Recently, E. histolytica cells were shown to possess raft-like plasma membrane domains. The co-localization of rafts with an important signaling/adhesion molecule, the galactose/N-acetylgalactosamine (Gal/GalNAc) lectin, suggests that rafts may also participate in signaling in E. histolytica. In the proposed studies, the biological role of E. histolytica lipid rafts, as well as of several Pis, will be explored. In the first Aim, the relationship between rafts and actin, and their role in virulence will be examined. In the second Aim, the connection between lipid rafts, vesicle trafficking, and actin will be assessed utilizing genetic approaches with mutants in which these cellular components are uncoupled. Finally, in the third Aim, the role of Pis in parasite virulence functions will be examined. This will be achieved by examining the function of PI 3-kinase and PTEN phosphatase, enzymes with complimentary roles in Pi- based signaling. Since vesicle trafficking, actin cytoskeletal rearrangements and signaling likely regulate virulence; these studies will contribute significantly to understanding the pathogenicity of E. histolytica. Public Health Description: Entamoeba histolytica is the causitive agent of amoebic dysentery and liver abscess and ranks third in the world for deaths due to parasitic disease. Since it is also classified as a bioterrorism agent, there is elevated priority to understand its virulence. The proposed studies will examine signaling pathways that are activated during parasite-host interaction. Since signaling likely regulates virulence, these studies will contribute significantly to understanding the biology of E. histolytica.