An Insight into the Proteome of Crithidia fasciculata Choanomastigotes as a Comparative Approach to Axenic Growth, Peanut Lectin Agglutination and Differentiation of Leishmania spp. Promastigotes

The life cycle of the trypanosomatid Crithidia fasciculata is monogenetic, as the unique hosts of these parasites are different species of culicids. The comparison of these non-pathogenic microorganisms evolutionary close to other species of trypanosomatids that develop digenetic life cycles and cause chronic severe sickness to millions of people worldwide is of outstanding interest. A ground-breaking analysis of differential protein abundance in Crithidia fasciculata is reported herein. The comparison of the outcome with previous gene expression profiling studies developed in the related human pathogens of the genus Leishmania has revealed substantial differences between the motile stages of these closely related organisms in abundance of proteins involved in catabolism, redox homeostasis, intracellular signalling, and gene expression regulation. As L. major and L. infantum agglutinate with peanut lectin and non-agglutinating parasites are more infective, the agglutination properties were evaluated in C. fasciculata. The result is that choanomastigotes are able to agglutinate with peanut lectin and a non-agglutinating subpopulation can be also isolated. As a difference with L. infantum, the non-agglutinating subpopulation over-expresses the whole machinery for maintenance of redox homeostasis and the translation factors eIF5a, EF1α and EF2, what suggests a relationship between the lack of agglutination and a differentiation process.锥虫体（trypanosomatid）短膜虫（Crithidia fasciculata）的生命周期为单宿主型，该寄生虫的唯一宿主为不同种类的蚊科昆虫（culicids）。对这类非致病性微生物与其他锥虫体物种开展比较研究具有极高的科研价值——这类非致病性微生物在进化上与那些具备双宿主生命周期、并导致全球数百万人口罹患慢性重症疾病的锥虫体物种亲缘关系紧密。本文报道了一项针对短膜虫差异蛋白丰度的突破性分析研究。将本研究结果与此前在利什曼原虫属（Leishmania）相关人类病原体中开展的基因表达谱分析研究进行对比后发现，这些亲缘关系密切的生物体的运动阶段，在分解代谢、氧化还原稳态、细胞内信号转导以及基因表达调控相关蛋白的丰度上存在显著差异。由于硕大利什曼原虫（L. major）和婴儿利什曼原虫（L. infantum）可与花生凝集素（peanut lectin）发生凝集反应，且不发生凝集的寄生虫感染力更强，因此本研究对短膜虫的凝集特性进行了评估。研究结果显示，短膜虫型鞭毛体（choanomastigotes）可与花生凝集素发生凝集反应，同时也可分离得到不发生凝集的亚群。与婴儿利什曼原虫不同，该不发生凝集的亚群会过表达维持氧化还原稳态的全套蛋白系统以及翻译因子eIF5a、EF1α与EF2，这表明凝集缺陷与分化过程之间存在关联。