Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA.
Department of Bioengineering, University of California Los Angeles, Los Angeles, CA, 90095, USA.
Nat Commun. 2023 Aug 26;14(1):5225. doi: 10.1038/s41467-023-40230-z.
Motility of pathogenic protozoa depends on flagella (synonymous with cilia) with axonemes containing nine doublet microtubules (DMTs) and two singlet microtubules. Microtubule inner proteins (MIPs) within DMTs influence axoneme stability and motility and provide lineage-specific adaptations, but individual MIP functions and assembly mechanisms are mostly unknown. Here, we show in the sleeping sickness parasite Trypanosoma brucei, that FAP106, a conserved MIP at the DMT inner junction, is required for trypanosome motility and functions as a critical interaction hub, directing assembly of several conserved and lineage-specific MIPs. We use comparative cryogenic electron tomography (cryoET) and quantitative proteomics to identify MIP candidates. Using RNAi knockdown together with fitting of AlphaFold models into cryoET maps, we demonstrate that one of these candidates, MC8, is a trypanosome-specific MIP required for parasite motility. Our work advances understanding of MIP assembly mechanisms and identifies lineage-specific motility proteins that are attractive targets to consider for therapeutic intervention.
致病原生动物的运动能力取决于鞭毛（与纤毛同义），鞭毛的轴丝含有九对双联微管（DMT）和两对单微管。DMT 内的微管内蛋白（MIP）影响轴丝的稳定性和运动能力，并提供谱系特异性的适应性，但单个 MIP 的功能和组装机制大多未知。在这里，我们在昏睡病寄生虫布氏锥虫中表明，DMT 内连接点处的保守 MIP FAP106 对于锥虫的运动是必需的，并且作为一个关键的相互作用枢纽，指导几个保守和谱系特异性 MIP 的组装。我们使用比较冷冻电子断层扫描（cryoET）和定量蛋白质组学来鉴定 MIP 候选物。通过 RNAi 敲低以及将 AlphaFold 模型拟合到 cryoET 图谱中，我们证明了这些候选物之一，MC8，是一种锥虫特异性 MIP，是寄生虫运动所必需的。我们的工作推进了对 MIP 组装机制的理解，并确定了谱系特异性运动蛋白，这些蛋白是治疗干预的有吸引力的候选目标。
