UPTAKE OF HOST CELL CHOLESTEROL BY T GONDII

描述（来自申请人摘要）：弓形虫是一种专性 细胞内的寄生虫，这是能够入侵和复制的所有 有核细胞弓形虫病，特别是累及大脑的弓形虫病， 获得性免疫缺陷综合症发病率和死亡率的来源。 围绕细胞内寄生虫的空泡膜含有一种 功能孔，允许小营养物质从宿主细胞中扩散 进入寄生虫周围的空泡空间然而，基本上没有什么 已知寄生虫生长所需的宿主细胞来源的大分子， 也不了解寄生虫获取这些营养物质的机制。我们有 表明细胞内T.弓形虫速殖子有效地获得和 隔离通过宿主细胞内化到细胞中的宿主细胞胆固醇 LDL受体途径。这个过程需要活的寄生虫， 可能涉及分泌的寄生虫甾醇结合蛋白。提供 过量的胆固醇会加速T.弓形虫生长，表明 胆固醇限制了寄生虫的生长t.弓形虫引起 在感染宿主细胞LDL内化中，可能通过激活宿主细胞 胆固醇稳态的调节机制。这些都是完全 一种寄生虫的意外发现，它存在于一个空泡中， 与宿主内吞级联的细胞器融合。为了追求上述目标， 观察，寄生虫调节宿主表达的机制 将确定参与甾醇摄取和生物合成的基因。分泌 寄生虫蛋白，参与从宿主获取胆固醇 细胞将被识别。寄生虫的内吞运输将受到干扰 使用药理学和分子操作，以及对胆固醇的影响 将评估寄生虫细胞器的摄取和递送。这些实验 是重要的，因为它们阐明了运输的机制， 必需营养素胆固醇-依次从宿主细胞到PVM， PV，然后穿过寄生虫质膜，最终到达寄生虫 细胞器同时，它们定义了T.弓形虫 大分子摄取的内吞途径，并打开了这种可能性， 途径可用于T.弓形虫和潜在的 其他顶复门寄生虫，最著名的是隐孢子虫。

DESCRIPTION (from applicant's abstract): Toxoplasma gondii is an obligate intracellular parasite, which is capable of invading and replicating within all nucleated cells. Toxoplasmosis, particularly involving the brain, is a major source of morbidity and mortality in the Acquired Immune Deficiency Syndrome. The vacuole membrane surrounding the intracellular parasite contains a functional pore, which allows diffusion of small nutrients from the host cell into the vacuolar space surrounding the parasite. However, essentially nothing is known about macromolecules of host cell origin required for parasite growth, nor of mechanisms for parasite acquisition of these nutrients. We have demonstrated that intracellular T. gondii tachyzoites efficiently acquire and sequester host cell cholesterol internalized into cells through the host cell LDL receptor pathway. Viable parasites are required for this process, potentially implicating a secreted parasite sterol binding protein. Providing excess cholesterol to infected cells accelerates T. gondii growth, suggesting that cholesterol is limiting for parasite growth. T. gondii induces an increase in LDL internalization in infected host cells, possibly by activating host cell regulatory mechanisms of cholesterol homeostasis. These are all completely unexpected findings for a parasite, which resides in a vacuole, which does not fuse with organelles of the host endocytic cascade. To pursue the above observations, the mechanism by which the parasite regulates expression of host genes involved in sterol uptake and biosynthesis will be determined. Secreted parasite proteins, which participate in cholesterol acquisition from the host cell will be identified. Endocytic traffic in the parasite will be perturbed using pharmacologic and molecular manipulations, and effects on cholesterol uptake and delivery to parasite organelles will be assessed. These experiments are important because they elucidate the mechanisms of transport of an essential nutrient cholesterol - sequentially from the host cell to the PVM and PV, then across the parasite plasma membrane an ultimately to parasite organelles. Simultaneously, they define the contribution of the T. gondii endocytic pathway to macromolecule uptake, and open the possibility that this pathway can be used for therapeutic advantage in T. gondii and potentially in other Apicomplexan parasites, most notably Cryptosporidium parvum.