Lysosomal biogenesis and function in African trypanosomes

性状（由申请方提供）：非洲锥虫（布氏锥虫亚种）非洲锥虫是一种寄生原生动物，可引起人类非洲锥虫病（HAT，昏睡病），以及牛和其他牲畜的长角线虫病。这些疾病在发现采采蝇病媒的撒哈拉以南非洲地区造成了毁灭性的影响，36个国家的约6 000万人面临被采采蝇叮咬的风险，因此也面临传播的风险，就在2000年，世卫组织估计每年有30万或更多的新感染病例。只有少数药物用于治疗HAT，其中最好的（依氟鸟氨酸）价格昂贵，需要一个困难的方案，其中最差的（美拉胂醇）杀死高达10%的受体。如果不进行干预，感染不可避免地是致命的，由于疫苗接种不是一种选择，因此迫切需要开发新药。为此，更好地了解寄生虫的基本生物学是必不可少的，特别是可能适用于治疗的过程。这样的过程是寄生虫溶酶体的生物发生，因为它以多种方式影响宿主-病原体平衡。通过锥虫生命周期对溶酶体活性的表达进行差异调节[1]，并且在必需溶酶体组分的生物合成运输中存在阶段特异性差异[2]。溶酶体是从宿主血清获得的内吞货物的最终储存库，用于营养目的[3]，以及用于从细胞表面去除的潜在溶解性免疫复合物[4]。溶酶体蛋白酶TbCatL（锥虫蛋白酶）的释放是人类感染的标志性事件（穿透中枢神经系统）中的一个因素[5]。溶酶体生理学对先天性人血清抗性性状（锥虫溶解因子）的活性至关重要，锥虫溶解因子限制了锥虫属物种的宿主范围[6]。最后，溶酶体水解活性作为潜在的化疗靶点引起了相当大的关注[7]。锥虫中溶酶体的生物发生和功能与分泌/内吞运输的更大主题密切相关。在定义这些过程方面已经取得了很大进展，特别是关于血流阶段变体表面糖蛋白的输出和回收。然而，我们对通向溶酶体的途径知之甚少，无论是生物合成还是内吞。在上一个资助期，我们启动了基于单个溶酶体膜蛋白p67的研究。在这个提议中，我们打算建立在我们以前对p67的研究（目标#1）的基础上，但也将我们的重点扩展到溶酶体的其他成分（目标#2和3）。这项工作的目的是扩大我们对基本锥虫生物学这一关键方面的理解。我们坚信，这一努力将有助于为未来的药物开发奠定基础，并且不仅将阐明差异，而且还将阐明真核生物进化过程中常见的细胞生物学过程的相似性。 公共卫生相关性：非洲锥虫（布氏锥虫亚种）非洲锥虫是一种寄生原生动物，可引起人类非洲锥虫病（HAT，昏睡病），以及牛和其他牲畜的长角线虫病。目前的药物是有毒的，疫苗接种不是一种选择，因此需要新的化疗靶点。溶酶体是寄生虫生存和致病的关键消化细胞器。对溶酶体的生物发生和功能的基础研究将为后续的寄生虫特异性药物开发提供基础。

DESCRIPTION (provided by applicant): African trypanosomes (Trypanosoma brucei ssp.) are parasitic protozoa that cause human African trypanosomiasis (HAT, sleeping sickness), as well as nagana in cattle and other livestock. These diseases have devastating impact throughout sub-Saharan Africa where the tsetse fly vector is found. Some 60 million people in 36 countries are at risk of tsetse bite, and therefore of transmission, and as recently as 2000 the WHO estimated that there were 300,000 or more new infections per year. Only a handful of drugs are in use for treating HAT, the best of which (eflornithine) is expensive and requires a difficult regimen, the worst of which (melarsoprol) kills up to 10% of recipients. Infection is inevitably fatal without intervention, and since vaccination is not an option there is a critical need for new drug development. Toward this end a better understanding of the basic biology of the parasite is essential, particularly of processes that may be amenable to therapeutics. Such a process is the biogenesis of the parasite lysosome because it impacts the host- pathogen balance in multiple ways. Expression of lysosomal activities is differentially regulated through the trypanosome life cycle [1], and there are stage specific differences in the biosynthetic trafficking of essential lysosomal components [2]. The lysosome is the final repository of endocytic cargo acquired from host serum for nutritional purposes [3], as well as for potentially lytic immune complexes removed from the cell surface [4]. Release of the lysosomal protease TbCatL (trypanopain) is a factor in the signature event of human infection, penetration of the central nervous system [5]. Lysosomal physiology is critical to the activity of an innate human serum resistance trait, trypanolytic factor, which limits the host range of Trypanosoma species [6]. And finally, lysosomal hydrolytic activities have drawn considerable attention as potential chemotherapeutic targets [7]. Lysosomal biogenesis and function in trypanosomes are intimately related to the larger topic of secretory/endocytic trafficking. Much progress has been made in defining these processes, particularly regarding export and recycling of the bloodstream stage variant surface glycoprotein. However, little is known about pathways, either biosynthetic or endocytic, leading to the lysosome. In the previous funding period we initiated studies based on a single lysosomal membrane protein p67. In this proposal we intend to build on our previous studies of p67 (Aim #1), but also to extend our focus to other components of the lysosome (Aims #2 & 3). The purpose of this work is to enlarge our understanding of this critical aspect of basic trypanosome biology. It is our firm belief that this effort will help lay the foundation for future drug development, and will also illuminate not just the differences, but also the similarities of cell biological processes common the full range of eukaryotic evolution. PUBLIC HEALTH RELEVANCE: African trypanosomes (Trypanosoma brucei ssp.) are parasitic protozoa that cause human African trypanosomiasis (HAT, sleeping sickness), as well as nagana in cattle and other livestock. Current drugs are toxic and vaccination is not an option, consequently new chemotherapeutic targets are needed. The lysosome is a digestive organelle critical for parasite viability and pathogenesis. Basic studies of the biogenesis and function of the lysosome will provide a foundation for subsequent parasite-specific drug development.