Lysosomal biogenesis and function in African trypanosomes

描述(申请人提供)：非洲锥虫(Trypanosoma brucei SSP.)是导致人类非洲锥虫病(HAT、昏睡病)的寄生原虫，以及牛和其他牲畜的Nagana。这些疾病在发现采采蝇媒介的撒哈拉以南非洲地区造成毁灭性影响。36个国家的约6000万人面临采采咬伤的风险，因此有传播的风险，最近在2000年，世卫组织估计每年有30万或更多的新感染病例。目前仅有少数药物用于治疗HAT，其中最好的药物(依氟鸟氨酸)价格昂贵，需要困难的治疗方案，最糟糕的药物(美拉索洛尔)可导致高达10%的接受者死亡。如果不进行干预，感染不可避免地是致命的，而且由于接种疫苗不是一种选择，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，特别是对可能适用于治疗的过程。这一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-病原体的平衡。溶酶体活性的表达在锥虫体的生命周期中受到不同的调节[1]，并且在必需的溶酶体成分的生物合成运输方面存在阶段特异性的差异[2]。溶酶体是从宿主血清中获得的内吞物质的最终储存库，用于营养目的[3]，以及从细胞表面移除的潜在的裂解免疫复合体[4]。溶酶体蛋白TbCatL(锥虫酶)的释放是人类感染中枢神经系统的标志性事件的一个因素[5]。溶酶体生理学对于一种固有的人类血清抵抗特性--胰酶溶解因子的活性至关重要，它限制了锥虫物种的寄主范围[6]。最后，溶酶体的水解活性作为潜在的化疗靶点引起了相当大的关注[7]。锥体中溶酶体的生物发生和功能与分泌/内吞转运这一更大的主题密切相关。在确定这些过程方面已经取得了很大进展，特别是在血流阶段变异表面糖蛋白的出口和回收方面。然而，人们对导致溶酶体的途径知之甚少，无论是生物合成的还是内吞的。在之前的资助期间，我们启动了基于单个溶酶体膜蛋白p67的研究。在这项提案中，我们打算在我们以前对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组成部分(目标2和3)。这项工作的目的是扩大我们对基础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，并不仅将阐明差异，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之处。

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.