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Rab7D small GTPase is involved in phago‐, trogocytosis and cytoskeletal reorganization in the enteric protozoan Entamoeba histolytica
Cellular Microbiology ( IF 3.4 ) Pub Date : 2020-09-25 , DOI: 10.1111/cmi.13267
Yumiko Saito-Nakano 1 , Ratna Wahyuni 2, 3, 4 , Kumiko Nakada-Tsukui 1 , Kentaro Tomii 5 , Tomoyoshi Nozaki 2
Affiliation  

Rab small GTPases regulate membrane traffic between distinct cellular compartments of all eukaryotes in a tempo‐spatially specific fashion. Rab small GTPases are also involved in the regulation of cytoskeleton and signalling. Membrane traffic and cytoskeletal regulation play pivotal role in the pathogenesis of Entamoeba histolytica, which is a protozoan parasite responsible for human amebiasis. E. histolytica is unique in that its genome encodes over 100 Rab proteins, containing multiple isotypes of conserved members (e.g., Rab7) and Entamoeba‐specific subgroups (e.g., RabA, B, and X). Among them, E. histolytica Rab7 is the most diversified group consisting of nine isotypes. While it was previously demonstrated that EhRab7A and EhRab7B are involved in lysosome and phagosome biogenesis, the individual roles of other Rab7 members and their coordination remain elusive. In this study, we characterised the third member of Rab7, Rab7D, to better understand the significance of the multiplicity of Rab7 isotypes in E. histolytica. Overexpression of EhRab7D caused reduction in phagocytosis of erythrocytes, trogocytosis (meaning nibbling or chewing of a portion) of live mammalian cells, and phagosome acidification and maturation. Conversely, transcriptional gene silencing of EhRab7D gene caused opposite phenotypes in phago/trogocytosis and phagosome maturation. Furthermore, EhRab7D gene silencing caused reduction in the attachment to and the motility on the collagen‐coated surface. Image analysis showed that EhRab7D was occasionally associated with lysosomes and prephagosomal vacuoles, but not with mature phagosomes and trogosomes. Finally, in silico prediction of structural organisation of EhRab7 isotypes identified unique amino acid changes on the effector binding surface of EhRab7D. Taken together, our data suggest that EhRab7D plays coordinated counteracting roles: a inhibitory role in phago/trogocytosis and lyso/phago/trogosome biogenesis, and an stimulatory role in adherence and motility, presumably via interaction with unique effectors. Finally, we propose the model in which three EhRab7 isotypes are sequentially involved in phago/trogocytosis.

中文翻译:

Rab7D 小 GTPase 参与肠道原生动物溶组织内阿米巴的吞噬、吞噬作用和细胞骨架重组

Rab 小 GTP 酶以特定时间空间的方式调节所有真核生物不同细胞区室之间的膜交通。Rab 小 GTP 酶也参与细胞骨架和信号传导的调节。膜运输和细胞骨架调节在溶组织内阿米巴的发病机制中起着关键作用,溶组织内阿米巴是一种导致人类阿米巴病的原生动物寄生虫。E. histolytica的独特之处在于其基因组编码 100 多种 Rab 蛋白,其中包含多个同种型的保守成员(例如 Rab7)和内阿米巴特异性亚群(例如,RabA、B 和 X)。其中,E.histolyticaRab7 是由九个同种型组成的最多样化的组。虽然之前已经证明 EhRab7A 和 EhRab7B 参与溶酶体和吞噬体的生物发生,但其他 Rab7 成员的个人作用及其协调仍然难以捉摸。在本研究中,我们对 Rab7 的第三个成员 Rab7D 进行了表征,以更好地了解溶组织大肠杆菌中 Rab7 同种型多样性的重要性。EhRab7D 的过表达导致红细胞吞噬作用、哺乳动物活细胞的吞噬作用(意味着啃食或咀嚼一部分)以及吞噬体酸化和成熟减少。相反,EhRab7D基因的转录基因沉默在吞噬/吞噬作用和吞噬体成熟中导致相反的表型。此外,EhRab7D基因沉默导致胶原涂层表面的附着和运动减少。图像分析表明,EhRab7D 偶尔与溶酶体和前吞噬体液泡相关,但与成熟的吞噬体和吞噬体无关。最后,对 EhRab7 同种型结构组织的计算机模拟预测确定了 EhRab7D 效应子结合表面上独特的氨基酸变化。总而言之,我们的数据表明 EhRab7D 发挥协调的抵消作用:在吞噬/吞噬作用和溶血/吞噬/吞噬体生物发生中的抑制作用,以及在粘附和运动中的刺激作用,大概是通过与独特的效应器相互作用。最后,我们提出了三个 EhRab7 同种型依次参与吞噬/吞噬作用的模型。
更新日期:2020-09-25
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