Department of Molecular & Cell Biology, University of California, Berkeley, CA 94720, USA.
Department of Molecular & Cell Biology, University of California, Berkeley, CA 94720, USA
J Cell Sci. 2020 Jul 9;133(13):jcs129213. doi: 10.1242/jcs.129213.
, the causative agent of African sleeping sickness, has a flagellum that is crucial for motility, pathogenicity, and viability. In most eukaryotes, the intraflagellar transport (IFT) machinery drives flagellum biogenesis, and anterograde IFT requires kinesin-2 motor proteins. In this study, we investigated the function of the two kinesin-2 proteins, TbKin2a and TbKin2b, in bloodstream form trypanosomes. We found that, compared to kinesin-2 proteins across other phyla, TbKin2a and TbKin2b show greater variation in neck, stalk and tail domain sequences. Both kinesins contributed additively to flagellar lengthening. Silencing TbKin2a inhibited cell proliferation, cytokinesis and motility, whereas silencing TbKin2b did not. TbKin2a was localized on the flagellum and colocalized with IFT components near the basal body, consistent with it performing a role in IFT. TbKin2a was also detected on the flagellar attachment zone, a specialized structure that connects the flagellum to the cell body. Our results indicate that kinesin-2 proteins in trypanosomes play conserved roles in flagellar biosynthesis and exhibit a specialized localization, emphasizing the evolutionary flexibility of motor protein function in an organism with a large complement of kinesins.
，导致非洲昏睡病的病原体，具有鞭毛，鞭毛对于运动性、致病性和生存力至关重要。在大多数真核生物中，鞭毛内运输（IFT）机制驱动鞭毛发生，而正向 IFT 需要驱动蛋白-2 （kinesin-2） 运动蛋白。在这项研究中，我们研究了两种 kinesin-2 蛋白，TbKin2a 和 TbKin2b，在血液阶段锥虫中的功能。与其他门的 kinesin-2 蛋白相比，我们发现 TbKin2a 和 TbKin2b 的颈、茎和尾域序列变化更大。两种肌球蛋白都对鞭毛的延长有累加作用。沉默 TbKin2a 抑制细胞增殖、胞质分裂和运动，而沉默 TbKin2b 则没有。TbKin2a 定位于鞭毛上，并与靠近基体的 IFT 成分共定位，这与它在 IFT 中发挥作用一致。TbKin2a 也在鞭毛附着区被检测到，鞭毛附着区是连接鞭毛和细胞体的一种特殊结构。我们的结果表明，锥虫中的 kinesin-2 蛋白在鞭毛生物合成中发挥保守作用，并表现出特殊的定位，强调了在一个具有大量肌球蛋白的生物体中，马达蛋白功能的进化灵活性。
