Parasitology, Department of Infectious Diseases, University of Heidelberg Medical School, Heidelberg, Germany.
Cell Microbiol. 2012 Nov;14(11):1757-68. doi: 10.1111/j.1462-5822.2012.01836.x. Epub 2012 Jul 30.
Plasmodium sporozoites can move at high speed for several tens of minutes, which is essential for the initial stage of a malaria infection. The crescent-shaped sporozoites move on 2D substrates preferably in the same direction on circular paths giving raise to helical paths in 3D matrices. Here we determined the structural basis that underlies this type of movement. Immature, non-motile sporozoites were found to lack the subpellicular network required for obtaining the crescent parasite shape. In vitro, parasites moving in the favoured direction move faster and more persistent than the few parasites that move in the opposite direction. Photobleaching experiments showed that sporozoites flip their ventral side up when switching the direction of migration. Cryo-electron tomography revealed a polarized arrangement of microtubules and polar rings towards the substrate in Plasmodium sporozoites, but not in the related parasite Toxoplasma gondii. As a consequence, secretory vesicles, which release proteins involved in adhesion, migration and invasion at the front end of the parasite, are delivered towards the substrate. The resulting chiral structure of the parasite appears to determine the unique directionality of movement and could explain how the sporozoite achieves rapid and sustained directional motility in the absence of external stimuli.
疟原虫子孢子可以高速移动数十分钟，这对于疟疾感染的初始阶段至关重要。新月形的子孢子在 2D 基质上移动，优选在圆形路径上沿同一方向移动，从而在 3D 基质中产生螺旋路径。在这里，我们确定了这种运动类型的结构基础。未成熟的非运动子孢子被发现缺乏获得新月形寄生虫形状所需的亚膜网络。在体外，沿有利方向移动的寄生虫比少数沿相反方向移动的寄生虫移动得更快、更持久。光漂白实验表明，当子孢子改变迁移方向时，它们会将腹侧向上翻转。冷冻电子断层扫描显示，在疟原虫子孢子中，微管和极环向基质呈极化排列，但在相关寄生虫刚地弓形虫中则没有。因此，将参与寄生虫前端附着、迁移和入侵的分泌小泡递送到基质上。寄生虫的这种手性结构似乎决定了其独特的运动方向，这可以解释子孢子如何在没有外部刺激的情况下实现快速和持续的定向运动。
