UPTAKE OF HOST CELL CHOLESTEROL BY T GONDII

弓形虫对宿主细胞胆固醇的摄取

基本信息

批准号：
6752952
负责人：
KEITH Alan JOINER
金额：
$ 30.1万
依托单位：
UNIVERSITY OF ARIZONA
依托单位国家：
美国
项目类别：
财政年份：
2000
资助国家：
美国
起止时间：
2000-07-01 至 2006-06-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/6752952
关键词：
Toxoplasma gondii cholesterol endocytosis host organism interaction intracellular membranes intracellular parasitism lipid transport low density lipoprotein receptor membrane structure microorganism growth microorganism metabolism nutrient bioavailability nutrition related tag opportunistic infections tissue /cell culture

项目摘要

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.

描述（来自申请人的摘要）：弓形虫是一种专性弓形虫细胞内寄生虫，能够侵入并在所有细胞内复制有核细胞。弓形虫病，特别是累及大脑的弓形虫病，是一种主要的疾病获得性免疫缺陷综合症发病率和死亡率的来源。细胞内寄生虫周围的液泡膜含有功能性孔，允许少量营养物质从宿主细胞扩散进入寄生虫周围的液泡空间。不过本质上没什么已知寄生虫生长所需的宿主细胞来源的大分子，也没有了解寄生虫获取这些营养物质的机制。我们有证明细胞内弓形虫速殖子有效地获得和隔离宿主细胞胆固醇通过宿主细胞内化到细胞中 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。提供受感染细胞中过量的胆固醇会加速弓形虫的生长，表明胆固醇限制寄生虫的生长。弓形虫诱导增加受感染宿主细胞中 LDL 内化，可能是通过激活宿主细胞胆固醇稳态的调节机制。这些都是完全寄生虫的意外发现，它存在于液泡中，而液泡不与宿主内吞级联的细胞器融合。为了追求上述观察，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。分泌的寄生虫蛋白，参与从宿主获取胆固醇细胞将被识别。寄生虫的内吞交通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吸收和递送。这些实验很重要，因为它们阐明了运输机制必需营养胆固醇——依次从宿主细胞到 PVM 和 PV，然后穿过寄生虫质膜，最终到达寄生虫细胞器。同时，他们定义了弓形虫的贡献大分子摄取的内吞途径，并开启了这种可能性途径可用于弓形虫的治疗优势，并有可能用于其他顶复门寄生虫，最著名的是小隐孢子虫。