Alcantara Carolina L, de Souza Wanderley, Cunha E Silva Narcisa L
Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil.
Núcleo de Biologia Estrutural e Bioimagens (CENABIO)-Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Biomagens (INBEB), Rio de Janeiro, Rio de Janeiro, Brazil.
Cell Microbiol. 2021 Sep;23(9):e13346. doi: 10.1111/cmi.13346. Epub 2021 May 18.
Endocytosis in Trypanosoma cruzi is mainly performed through a specialised membrane domain called cytostome-cytopharynx complex. Its ultrastructure and dynamics in endocytosis are well characterized in epimastigotes, being absent in trypomastigotes, that lack endocytic activity. Intracellular amastigotes also possess a cytostome-cytopharynx but participation in endocytosis of these forms is not clear. Extracellular amastigotes can be obtained from the supernatant of infected cells or in vitro amastigogenesis. These amastigotes share biochemical and morphological features with intracellular amastigotes but retain trypomastigote's ability to establish infection. We analysed and compared the ultrastructure of the cytostome-cytopharynx complex of intracellular amastigotes and extracellular amastigotes using high-resolution tridimensional electron microscopy techniques. We compared the endocytic ability of intracellular amastigotes, obtained through host cell lysis, with that of extracellular amastigotes. Intracellular amastigotes showed a cytostome-cytopharynx complex similar to epimastigotes'. However, after isolation, the complex undergoes ultrastructural modifications that progressively took to an impairment of endocytosis. Extracellular amastigotes do not possess a cytostome-cytopharynx complex nor the ability to endocytose. Those observations highlight morpho functional differences between intra and extracellular amastigotes regarding an important structure related to cell metabolism. TAKE AWAYS: T. cruzi intracellular amastigotes endocytose through the cytostome-cytopharynx complex. The cytostome-cytopharynx complex of intracellular amastigotes is ultrastructurally similar to the epimastigote. Intracellular amastigotes, once outside the host cell, disassembles the cytostome-cytopharynx membrane domain. Extracellular amastigotes do not possess a cytostome-cytopharynx either the ability to endocytose.
克氏锥虫的内吞作用主要通过一个称为胞口-胞咽复合体的特殊膜结构域来进行。其超微结构以及在内吞作用中的动态变化在无鞭毛体中已得到充分表征，而在缺乏内吞活性的锥鞭毛体中则不存在。细胞内无鞭毛体也具有胞口-胞咽，但这些形态在内吞作用中的参与情况尚不清楚。细胞外无鞭毛体可从感染细胞的上清液中获得，也可通过体外无鞭毛体生成获得。这些无鞭毛体与细胞内无鞭毛体具有共同的生化和形态特征，但保留了锥鞭毛体建立感染的能力。我们使用高分辨率三维电子显微镜技术分析并比较了细胞内无鞭毛体和细胞外无鞭毛体的胞口-胞咽复合体的超微结构。我们将通过宿主细胞裂解获得的细胞内无鞭毛体的内吞能力与细胞外无鞭毛体的内吞能力进行了比较。细胞内无鞭毛体显示出与无鞭毛体相似的胞口-胞咽复合体。然而，分离后，该复合体经历超微结构修饰，逐渐导致内吞作用受损。细胞外无鞭毛体不具有胞口-胞咽复合体，也没有内吞能力。这些观察结果突出了细胞内和细胞外无鞭毛体在与细胞代谢相关的重要结构方面的形态功能差异。要点：克氏锥虫细胞内无鞭毛体通过胞口-胞咽复合体进行内吞。细胞内无鞭毛体的胞口-胞咽复合体在超微结构上与无鞭毛体相似。细胞内无鞭毛体一旦离开宿主细胞，就会拆解胞口-胞咽膜结构域。细胞外无鞭毛体既不具有胞口-胞咽，也没有内吞能力。
