Host cell invasion by Apicomplexa: an expression of the parasite's contractile system?
Host cell invasion by Apicomplexa: an expression of the parasite's contractile system?
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Apicomplexa 入侵宿主细胞：寄生虫收缩系统的表达？
作者：
D. Russell
摘要 最近对球虫子孢子运动性的研究表明，膜相关的收缩系统能够将某些膜内成分沿着寄生虫表面移动，推动其前进。该系统的特性类似于记录的宿主细胞入侵观察结果。本研究参考上述研究结果，通过光学显微镜、扫描和透射电子显微镜对柔嫩艾美耳球虫和弯形艾美耳球虫的入侵行为进行了研究。已知的运动抑制剂可以防止入侵，但附着似乎不受影响。入侵本身分为三个阶段；附着和定向、寄生液泡的诱导以及寄生虫进入液泡的易位。超微结构检查显示在整个侵袭过程中维持着紧密的膜/膜关联。从这些结果来看，寄生虫通过“盖住”宿主/寄生虫连接点进入寄生液泡，从而移动到宿主细胞中。这种模型有两个主要优点；它不需要对任何一个细胞进行额外的修饰，并且膜受体的特异性将使一个膜相关收缩系统负责运动、抗体加帽和宿主细胞入侵。
SUMMARY Recent studies on the motility of coccidian sporozoites have demonstrated a membrane-associated contractile system capable of moving certain intramembraneous components down the parasite surface propelling it forwards. The properties of this system resemble recorded observations on host cell invasion. In this study the invasive behaviour of Eimeria tenella and E. acervulina has been examined, with reference to the above findings, by light microscope and scanning and transmission electron microscopes. Known inhibitors of motility prevent invasion, though attachment appears unaffected. Invasion itself consists of 3 phases; attachment and orientation, induction of a parasitophorous vacuole and translocation of the parasite into the vacuole. Ultrastructural examination reveals a close membrane/membrane association maintained throughout invasion. From these results it is suggested that the parasite enters the parasitophorous vacuole by ‘capping’ the host/parasite junction down its body, so locomoting into the host cell. Such a model has two main advantages; it requires no additional modifications to either cell, and the specificity of membrane receptors would enable the one membrane-associated contractile system to be responsible for locomotion, antibody capping and host cell invasion.