Expression of trypomastigote trans-sialidase in metacyclic forms of Trypanosoma cruzi increases parasite escape from its parasitophorous vacuole
Expression of trypomastigote trans-sialidase in metacyclic forms of Trypanosoma cruzi increases parasite escape from its parasitophorous vacuole
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DOI：
10.1111/j.1462-5822.2006.00755.x
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发表时间：
2006-12-01
影响因子：
3.4
通讯作者：
Schenkman, Sergio
中科院分区：
文献类型：
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作者：
Rubin-de-Celis, Sergio S. C.;Uemura, Haruki;Schenkman, Sergio
克氏锥虫通过形成寄生液泡（pv）积极侵入哺乳动物细胞。进入后，寄生虫必须从这些液泡中逃脱，以便在宿主细胞质内复制。反式唾液酸酶（TS）是一种用于从宿主糖缀合物中获得唾液酸的寄生虫酶，与细胞入侵和PV退出有关，但该酶在这些过程中的作用尚不清楚。在这里，我们发现来自受感染哺乳动物细胞的锥乳突虫表达和释放的TS活性是来自昆虫载体的感染形式的无性系亚环锥乳突虫的20倍。这两种形式都具有侵入哺乳动物细胞的能力，但细胞衍生的锥乳线虫较早地从液泡中退出。为了测试高TS表达是否与PV的增加退出有关，我们在亚环形式的表面表达了锥马乳石TS。转染和未转染的元环细胞同样附着和侵袭HeLa或CHO细胞。相比之下，表面表达TS的元环细胞比未转染的元环细胞或在细胞质中表达TS的元环细胞更早地从液泡中逃逸。唾液酸可能作为一种屏障，被表面或分泌的TS移除，因为所有类型的寄生虫都比野生型CHO细胞更早地从唾液酸缺乏的Lec 2细胞的液泡中逃脱。此外，表达TS的半环型和半环型较早分化为无纺丝体。这些结果表明，TS在细胞源性锥体中表达的增加是导致锥体较早地从PV进入细胞质并随后分化为无尾锥体的原因。
Trypanosoma cruzi actively invades mammalian cells by forming parasitophorous vacuoles (PVs). After entry, the parasite has to escape from these vacuoles in order to replicate inside the host cell cytosol. Trans-sialidase (TS), a parasite enzyme that is used to obtain sialic acid from host glycoconjugates, has been implicated in cell invasion and PV exit, but how the enzyme acts in these processes is still unknown. Here we show that trypomastigotes derived from infected mammalian cells express and release 20 times more TS activity than axenic metacyclic trypomastigotes, which correspond to the infective forms derived from the insect vector. Both forms have the same capacity to invade mammalian cells, but cell derived trypomastigotes exit earlier from the vacuole. To test whether high TS expression is responsible for this increased exit from the PV, trypomastigote TS was expressed on the surface of metacyclic forms. Transfected and non-transfected metacyclics attached to and invaded HeLa or CHO cells equally. In contrast, metacyclics expressing TS on the surface escaped earlier from the vacuole than non-transfected metacyclics, or metacyclics expressing TS in their cytoplasm. Sialic acid may act as a barrier, which is removed by surface andor secreted TS, because all types of parasites escaped earlier from the vacuoles of sialic acid-deficient Lec 2 cells than wild-type CHO cells. In addition, trypomastigotes and metacyclic forms expressing TS differentiated earlier into amastigotes. These results indicate that the increased expression of TS in cell-derived trypomastigotes is responsible for the earlier exit from the PV to the cytoplasm and their subsequent differentiation into amastigotes.