Sibley L D, Niesman I R, Asai T, Takeuchi T
Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110.
Exp Parasitol. 1994 Nov;79(3):301-11. doi: 10.1006/expr.1994.1093.
Toxoplasma gondii is an obligate intracellular parasite capable of invading a wide range of host cells where it residues in a specially modified compartment termed the parasitophorous vacuole. This compartment provides a protected environment for the parasite which enters a rapid growth phase shortly after invasion. To identify functional components of this interface, we have used immunolabeling and cell fractionation to localize the potent nucleoside triphosphate hydrolase (NTPase) produced by Toxoplasma. In extracellular tachyzoites, NTPase was not exposed on the cell surface but was localized in small vesicles, called dense granules, scattered throughout the cell cytoplasm. Shortly following invasion. NTPase was secreted from dense granules and occupied the lumen of the parasitophorous vacuole where it was often associated with the intravacuolar network. NTPase was exclusively found in the supernatant in cell fractionation studies of both extracellular tachyzoites lysed by freeze-thaw and following secretion into the parasitophorous vacuole. These studies provide evidence for the rapid secretion of NTPase into the parasitophorous vacuole, where it may play a key role in processing of nucleotides for purine salvage by the parasite.
刚地弓形虫是一种专性细胞内寄生虫，能够侵入多种宿主细胞，并在一个经过特殊修饰的称为纳虫空泡的区室中存活。这个区室为寄生虫提供了一个受保护的环境，寄生虫在侵入后不久就进入快速生长阶段。为了确定这个界面的功能成分，我们利用免疫标记和细胞分级分离技术来定位刚地弓形虫产生的强效核苷三磷酸水解酶（NTPase）。在细胞外速殖子中，NTPase不暴露在细胞表面，而是定位于散布在整个细胞质中的小泡，即致密颗粒中。侵入后不久，NTPase从致密颗粒中分泌出来，占据纳虫空泡的腔，在那里它常与泡内网络相关联。在对经冻融裂解的细胞外速殖子以及分泌到纳虫空泡后的细胞进行分级分离研究时，NTPase仅存在于上清液中。这些研究为NTPase快速分泌到纳虫空泡中提供了证据，在那里它可能在寄生虫嘌呤补救途径的核苷酸加工过程中起关键作用。
