Conditional expression of Toxoplasma gondii apical membrane antigen-1 (TgAMA1) demonstrates that TgAMA1 plays a critical role in host cell invasion
Conditional expression of Toxoplasma gondii apical membrane antigen-1 (TgAMA1) demonstrates that TgAMA1 plays a critical role in host cell invasion
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DOI：
10.1091/mbc.e05-04-0281
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发表时间：
2005-09-01
影响因子：
3.3
通讯作者：
Ward, GE
中科院分区：
文献类型：
--
作者：
Mital, J;Meissner, M;Ward, GE
弓形虫是一种专性胞内寄生虫，是人类重要的病原体。对于T.弓形虫或相关的顶复门寄生虫（包括疟原虫属，导致疟疾），因为研究这些生物体中的必需基因很困难。我们已经使用了最近开发的可调控启动子来创建T的条件敲除。弓形虫顶端膜抗原1（TgAMA1）。TgAMA1是一种跨膜蛋白，定位于寄生虫的微丝，即在入侵过程中分泌的分泌细胞器。AMA1蛋白在顶复门寄生虫中是保守的，并且作为疟疾疫苗候选物具有强烈的兴趣。我们在这里表明，T。缺乏TgAMA1的弓形虫速殖子在其侵入宿主细胞的能力方面严重受损，这提供了AMA1在侵入期间起作用的直接遗传证据。TgAMA1缺乏对寄生虫的微丝分泌或初始附着到宿主细胞没有影响，但它确实抑制棒状体的分泌，棒状体是其放电与活跃的宿主细胞渗透偶联的细胞器。这些数据表明，寄生虫附着到宿主细胞的模型发生在两个不同的阶段，其中第二个需要TgAMA1，并参与调节棒状体分泌。
Toxoplasma gondii is an obligate intracellular parasite and an important human pathogen. Relatively little is known about the proteins that orchestrate host cell invasion by T. gondii or related apicomplexan parasites (including Plasmodium spp., which cause malaria), due to the difficulty of studying essential genes in these organisms. We have used a recently developed regulatable promoter to create a conditional knockout of T. gondii apical membrane antigen-1 (TgAMA1). TgAMA1 is a transmembrane protein that localizes to the parasite's micronemes, secretory organelles that discharge during invasion. AMA1 proteins are conserved among apicomplexan parasites and are of intense interest as malaria vaccine candidates. We show here that T. gondii tachyzoites depleted of TgAMA1 are severely compromised in their ability to invade host cells, providing direct genetic evidence that AMA1 functions during invasion. The TgAMA1 deficiency has no effect on microneme secretion or initial attachment of the parasite to the host cell, but it does inhibit secretion of the rhoptries, organelles whose discharge is coupled to active host cell penetration. The data suggest a model in which attachment of the parasite to the host cell occurs in two distinct stages, the second of which requires TgAMA1 and is involved in regulating rhoptry secretion.