Induction of an acrosomal process in Toxoplasma gondii: visualization of actin filaments in a protozoan parasite.
Induction of an acrosomal process in Toxoplasma gondii: visualization of actin filaments in a protozoan parasite.
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DOI：
10.1073/pnas.96.16.9095
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发表时间：
1999-08
影响因子：
11.1
通讯作者：
M. Shaw;L. Tilney
中科院分区：
文献类型：
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作者：
M. Shaw;L. Tilney
弓形虫是一种复合体寄生虫，其侵袭期以肌动蛋白依赖的方式主动入侵宿主细胞。然而，尽管含有大量的生化肌动蛋白，但在这些寄生虫中从未观察到肌动蛋白细丝。Jasplakinolide是一种膜透性的肌动蛋白聚合和细丝稳定药物，它诱导每个速殖子前端的肌动蛋白细丝与锥体结合，在许多情况下，它们形成一个突出的膜包裹的顶端突起，使人想起无脊椎动物精子的顶体突起。这些jasplakinolide诱导的细丝上装饰着肌球蛋白亚片段1，明确地证明它们确实是肌动蛋白。用jasplakinolide治疗的速殖子无法入侵宿主细胞，但一旦药物被移除，寄生虫就能够进入宿主细胞。在寄生虫顶端的肌动蛋白聚合与顶端在宿主细胞入侵中的作用是一致的，该作用是由与表面蛋白的分泌和背面封顶耦合的锥形复合体的手提式伸展和收缩所驱动的。
The invasive stages of Toxoplasma gondii, an Apicomplexan parasite, actively invade their host cells in an actin-dependent way. However, despite containing biochemically significant amounts of actin, actin filaments have never been observed in these parasites. Jasplakinolide, a membrane-permeable actin-polymerizing and filament-stabilizing drug, induced the polymerization of actin filaments at the anterior end of each tachyzoite in association with the conoid, where they formed, in many cases, a prominent membrane-enclosed apical projection reminiscent of acrosomal processes of invertebrate sperm. These jasplakinolide-induced filaments decorated with myosin subfragment 1, demonstrating unequivocally that they were indeed actin. Jasplakinolide-treated tachyzoites were unable to invade host cells, but once the drug was removed the parasites were able to enter host cells. Actin polymerization at the apical end of the parasite is consistent with the role of the apical end in host-cell invasion powered by a jackhammer-like extension and retraction of the conoid complex coupled to the secretion and rearward capping of surface proteins.