Structural and functional dissection of the molecular machinery responsible for singular antigen expression and immune evasion in African trypanosomes

在宿主-病原体的军备竞赛中，抗原变异是最复杂的毒力机制之一。一些最致命的寄生虫，如非洲锥虫和疟疾寄生虫，能够系统地改变向宿主免疫系统展示的蛋白质的身份，导致世界上最贫穷人口的高死亡率和发病率。锥虫是伪装的大师，从数千个可能的基因中以单基因的方式表达它们的变异表面糖蛋白--这是极端生物学的一个很好的例子，也是一个很好的模型系统。对负责单一抗原表达的机制的追求已经是50年的长期追求，并且在每个生物体中仍然难以捉摸。它最近在锥虫（PMID：31289266; 33432154）中的鉴定为破解这个长期存在的谜团提供了一个及时的机会。该项目旨在：-纯化这种新型蛋白质复合物，并通过cryoEM解决其三维结构，这对于了解其作用机制至关重要。鉴定关键翻译后修饰并确定其功能/调节作用。因此，成功的申请人将接受几项尖端技术的培训，包括基因编辑（CRISPR/Cas9），质谱，下一代测序，天然条件下的蛋白质纯化和cryoEM。值得注意的是，了解抗原变异的分子机制是非常宝贵的，因为它极大地挑战了针对几种生物体的疫苗开发。

In the host-pathogen arms race, antigenic variation is one of the most sophisticated virulence mechanisms. Some of the deadliest parasites, like African trypanosomes and malaria parasites, are able to systematically alter the identity of proteins displayed to the host immune system, causing high mortality and morbidity among the world's poorest populations. Trypanosomes are masters of disguise, expressing their variant-surface-glycoprotein in a monogenic fashion from thousands of possible genes - a fine example of extreme biology and a great model system. The pursuit for the machinery responsible for singular-antigen-expression has been a 50-year long quest and had remained elusive in every organism. Its recent identification in trypanosomes ((PMID: 31289266; 33432154) represents a timely opportunity to crack this long-standing mystery. This project aims to:-purify this novel protein complex and solve its tridimensional structure by cryoEM, which will be critical to understand its mechanism of action.-identify key post-translational modifications and characterise their functional/regulatory role. Therefore, the successful applicant will be trained on several cutting-edge technologies, including gene editing (CRISPR/Cas9), mass-spectrometry, next-generation sequencing, protein purification in native conditions and cryoEM. Notably, understanding the molecular mechanisms underpinning antigenic variation is invaluable, as it greatly challenges vaccine development against several organisms.