Host nutrient uptake and regulation by Toxoplasma

描述（由申请人提供）：目前控制刚地弓形虫感染的治疗需要长期的药物治疗，而且这些药物对长期存在的囊化期无效，而囊化期是免疫功能低下个体危及生命的急性弓形虫病的原因。确定新的药物靶点是当务之急。弓形虫是一种专性细胞内寄生虫，居住在被寄生虫分泌物广泛修饰的液泡中。据推测，液泡寄生虫诱导的修饰主要是为了营养吸收。然而，基本上我们对弓形虫的营养需求一无所知。弓形虫获取宿主营养并调节其供应的策略将通过使用基因组、形态学、生化和遗传学方法来表征。宿主微管延伸到液泡空间，诱导含有营养物质的宿主溶酶体的输送。然后，介导溶酶体递送的小管通过寄生虫分泌的蛋白质外壳的形成而稳定下来。该提案的第一个目标将集中在弓形虫液泡周围宿主微管重组的分子机制。形成外壳的蛋白质的性质及其在宿主溶酶体清除液泡中的作用将被研究。弓形虫甾醇的主要来源是脂蛋白摄取，这一过程在感染细胞中特别增加。第二个目标将解决弓形虫感染细胞中胆固醇稳态的改变，以及弓形虫开发的调节机制，以优化胆固醇获取到适当的细胞器。这些研究的长期目标是揭示营养获取途径的特异性，这可能为选择性治疗干预提供机会，或者篡夺这些药物传递途径。同时，该项目具有广泛的细胞生物学意义，可以深入了解哺乳动物细胞中的胆固醇稳态、微管动力学和膜变形机制。

DESCRIPTION (provided by the applicant): Current treatments for the control of Toxoplasma gondii infections require long-term medication fraught with side effects and they are ineffective against the long-lived encysted stage, which is responsible for life threatening acute toxoplasmosis in immunocompromised individuals. The need for identifying novel drug targets is imperative. T. gondii is an obligate intracellular parasite, residing in a vacuole that is extensively modified by parasite secretions. It is speculated that the vacuolar parasite-induced modifications are largely for the purpose of nutrient uptake. However, essentially nothing is known about the nutritional needs of T. gondii. The strategies employed by Toxoplasma to access host nutrients and to regulate their supply will be characterized by using genomic, morphological, biochemical and genetic approaches. Host microtubules extend into the vacuolar space and induce the delivery of host lysosomes containing nutrients. The tubules mediating the lysosome delivery are then stabilized by the formation of a protein coat secreted by the parasite. A first aim of the proposal will focus on the molecular machinery underlying the reorganization of host microtubules around the Toxoplasma vacuole. The nature of the proteins forming the coat and their role in host lysosome scavenging into the vacuole will be studied. The primary source of T. gondii sterol is from lipoprotein uptake, a process that is specifically increased in infected cells. A second aim will address the alterations in cholesterol homeostasis in T. gondii-infected cells as well as the regulatory mechanisms developed by T. gondii to optimize cholesterol acquisition into proper organelles. The long-term goal of these studies is to reveal specificities in the pathways of nutrient acquisition which may offer opportunities for selective therapeutic intervention or to usurp these pathways for drug delivery. Simultaneously, this project is of broad cell biology interest and may provide insight into cholesterol homeostasis, microtubule dynamics and the mechanisms of membrane deformation in mammalian cells.