Mechanism of Infectivity Acquisition in African Trypanosomes

描述（由申请人提供）：阐明人类病原体的生物学对于理解发病机制和识别宿主生存必需的基因至关重要。该应用重点关注原生动物寄生虫布氏锥虫，这种寄生虫会导致撒哈拉以南非洲地区的人类和动物遭受毁灭性的​​疾病。目前还没有疫苗，治疗药物副​​作用严重，疗效下降。布氏锥虫在哺乳动物宿主和吸血采采蝇载体（双翅目：舌蝇科）之间经历了复杂的生命周期，其中涉及细胞形态、代谢、信号传导途径和基因表达的变化。因此，这些寄生虫已经进化出适应能力，使其能够在采采蝇的肠道和唾液腺以及哺乳动物宿主的血液中生存。采采蝇以受感染的宿主为食后，会形成细长、中间和粗短的血流形态。在果蝇中肠中，短节形式分化为非感染性原循环形式。感染性的重新获得是通过复杂的发育程序实现的，该程序最终在采采唾液腺中产生感染性后循环。尽管一个多世纪以来，人们已经认识到果蝇锥虫发育的复杂性，但其分子机制仍然是神秘的，部分原因是采采蝇带来的实验挑战。我们发现，在培养的非感染性原环形式中过度表达布氏锥虫RNA结合蛋白RBP6会启动分化为采采蝇中发现的发育阶段，并最终产生表达变异表面糖蛋白（VSG）外壳的感染性后环细胞。我们的首要目标是描述 RBP6 的作用机制。由于 RBP6 似乎是触发一系列事件的“主调节器”，因此确定 RBP6 的主要 mRNA 靶标至关重要。这将提供有关参与分化早期阶段的基因产物的重要信息，并用于制定有关从前循环到上鞭毛体形式转变过程中发生的细胞适应的可检验假设。我们的第二个目标是提供上鞭毛体和后循环生物的转录组和蛋白质组图谱，并解码后循环发生的生物学。最后，除了 VSG 之外，元循环分化所需的新基因的发现将是破译感染性获得过程如何发生的重大突破。总而言之，我们的研究计划提供了独特的机会来阐明从原循环到后循环的分化程序，并揭示重要 RNA 结合蛋白的作用模式。

DESCRIPTION (provided by applicant): Unraveling the biology of human pathogens is fundamental toward understanding mechanisms of pathogenesis and identifying genes essential for survival in the host. This application focuses on the protozoan parasite Trypanosoma brucei, which causes devastating diseases in humans and animals in sub-Saharan Africa. There are no vaccines, and therapeutic drugs have serious side effects and decreasing efficacy. T. brucei undergoes a complex life cycle between the mammalian host and the blood-feeding tsetse fly vector (Diptera: Glossinidae), which among others involves changes in cell morphology, metabolism, signaling pathways and gene expression. Consequently, these parasites have evolved adaptations to allow for their survival in both the gut and salivary glands of the tsetse fly, as well as in the bloodstream of their mammalian host. Upon feeding on an infected host, the tsetse fly takes up slender, intermediate and stumpy bloodstream forms. In the fly midgut stumpy forms differentiate into non-infectious procyclic forms. Reacquisition of infectivity is achieved through a complex developmental program that culminates in the tsetse salivary glands with the generation of infectious metacyclics. Although the intricate nature of trypanosome development in the fly has been recognized for more than a century, the molecular mechanisms are still mysterious, due in part to the experimental challenges posed by the tsetse fly. We found that overexpression of the T. brucei RNA-binding protein RBP6 in cultured non-infectious procyclic forms initiates differentiation into the developmental stages found in tsetse flies and culminates with the generation of infective metacyclics expressing the variant surface glycoprotein (VSG) coat. Our first goal will be to delineate the mechanism of action of RBP6. As RBP6 appears to be a "master regulator" triggering a cascade of events, it will be critical to identify the primary mRNA targets of RBP6. This will provide crucial information about gene products involved in the early stages of differentiation and for formulating a testable hypothesis about the cellular adaptations occurring in the transition from procyclic to epimastigotes forms. Our second goal will be to provide a transcriptomic and proteomic map of epimastigotes and metacyclics and to decode the biology of metacyclogenesis. Finally, the discovery of novel genes, besides VSG, required for metacyclic differentiation will be a major breakthrough toward deciphering how the process of acquisition of infectivity is brought about. Taken together our research plan provides unique opportunities to illuminate the differentiation program from procyclic to metacyclic and reveal the mode of action of an important RNA binding protein.