Dubremetz J F, Garcia-Réguet N, Conseil V, Fourmaux M N
Unité 42 INSERM, Villeneuve d'Ascq, France.
Int J Parasitol. 1998 Jul;28(7):1007-13. doi: 10.1016/s0020-7519(98)00076-9.
Host-cell invasion by apicomplexan parasites involves the successive exocytosis of three different secretory organelles; namely micronemes, rhoptries and dense granules. The findings of recent studies have extended the structural homologies of each set of organelles between most members of the phylum and suggest shared functions of each set. Micronemes are apparently used for host-cell recognition, binding, and possibly motility; rhoptries for parasitophorous vacuole formation; and dense granules for remodeling the vacuole into a metabolically active compartment. In addition, gene cloning and sequencing have demonstrated conserved domains, which are likely to serve similar functions in the invasion process. This is especially true for microneme proteins containing thrombospondin-like domains, which are likely to be involved in binding to sulphated glycoconjugates. One such protein was recently shown to be required for the motility of Plasmodium sporozoites. These molecules have been shown to be shed on the parasite and/or cell surfaces during the invasion process in Plasmodium, Toxoplasma and Eimeria. For rhoptries and dense granules, the association between exocytosed proteins and the parasitophorous vacuole membrane had been analyzed extensively in Toxoplasma, as these proteins are likely to play a crucial role in metabolic interactions between the parasites and their host cells. The development of parasite transformation by gene transfection has provided powerful tools to analyze the fate and function(s) of the corresponding proteins.
顶复门寄生虫对宿主细胞的入侵涉及三种不同分泌细胞器的连续胞吐作用，即微线体、棒状体和致密颗粒。最近的研究结果扩展了该门大多数成员之间每组细胞器的结构同源性，并表明每组细胞器具有共同的功能。微线体显然用于宿主细胞的识别、结合，可能还参与运动；棒状体用于形成纳虫空泡；致密颗粒用于将空泡重塑为代谢活跃的区室。此外，基因克隆和测序已证明存在保守结构域，这些结构域可能在入侵过程中发挥类似的功能。对于含有血小板反应蛋白样结构域的微线体蛋白来说尤其如此，这些结构域可能参与与硫酸化糖缀合物的结合。最近发现一种这样的蛋白是疟原虫子孢子运动所必需的。在疟原虫、弓形虫和艾美耳球虫的入侵过程中，这些分子已被证明会脱落到寄生虫和/或细胞表面。对于棒状体和致密颗粒，在弓形虫中已对胞吐蛋白与纳虫空泡膜之间的关联进行了广泛分析，因为这些蛋白可能在寄生虫与其宿主细胞之间的代谢相互作用中起关键作用。通过基因转染进行寄生虫转化的发展为分析相应蛋白的命运和功能提供了强大的工具。
