Graduate Institute of Pathology and Parasitology, National Defense Medical Center, Taipei City, Taiwan.
Division of Clinical Pathology, Department of Pathology, Tri-Service General Hospital, National Defense Medical Center, Taipei City, Taiwan.
J Microbiol Immunol Infect. 2019 Apr;52(2):336-344. doi: 10.1016/j.jmii.2018.11.002. Epub 2018 Nov 22.
Autophagy has been shown to be involved in the pathogenesis of several protists, offering prospects for the developments of new drugs targeting autophagy. However, there is no evidence illustrating functional autophagy in the deep-branching trichomonads. The human parasitic protist Trichomonas vaginalis has been predicted to possess reduced autophagic machinery, with only autophagy-related protein 8 (Atg8) conjugation system required for autophagosome formation.
The recombinant protein of TvAtg8 (rTvAtg8) and the polyclonal antibody against rTvAtg8 were generated. The expression and localization of TvAtg8 was monitored upon autophagy induction by glucose restriction (GR) compared with glucose-rich cultivation. The role of TvAtg8 in proteolysis was clarified.
Here, we report that T. vaginalis Atg8 (TvAtg8) is upregulated and conjugated to autophagosome-like vesicles upon autophagy induction by GR. Moreover, we investigate, for the first time, the role of autophagy in T. vaginalis. Proteasome inhibition (PI)-induced autophagy compensates for the removal of polyubiquitinated proteins under glucose-rich condition. GR-induced autophagy is a major proteolytic system in T. vaginalis. These results suggest that autophagy is vital for proteolysis in T. vaginalis with an impaired ubiquitin-proteasome system or under glucose-limited environment.
Our findings unveiled previously unidentified functions of autophagy in proteostasis in trichomonads, advancing our understanding of this highly conserved process in the ancient eukaryote.
自噬已被证明参与了几种原生动物的发病机制，为开发针对自噬的新药提供了前景。然而，没有证据表明深分枝毛滴虫中存在功能性自噬。人类寄生虫原生动物阴道毛滴虫被预测具有减少的自噬机制，仅需要自噬相关蛋白 8（Atg8）缀合系统即可形成自噬体。
生成了 TvAtg8（rTvAtg8）的重组蛋白和针对 rTvAtg8 的多克隆抗体。通过葡萄糖限制（GR）诱导自噬与葡萄糖丰富培养相比，监测 TvAtg8 的表达和定位。阐明了 TvAtg8 在蛋白水解中的作用。
在这里，我们报告 T. vaginalis Atg8（TvAtg8）在 GR 诱导的自噬时上调并与自噬体样囊泡缀合。此外，我们首次研究了自噬在 T. vaginalis 中的作用。蛋白酶体抑制（PI）诱导的自噬补偿了葡萄糖丰富条件下多泛素化蛋白的去除。GR 诱导的自噬是 T. vaginalis 中的主要蛋白水解系统。这些结果表明，自噬对于缺乏泛素-蛋白酶体系统或在葡萄糖有限环境下的 T. vaginalis 中的蛋白水解至关重要。
我们的发现揭示了自噬在毛滴虫中蛋白质稳定中的以前未被识别的功能，提高了我们对这一在古老真核生物中高度保守的过程的理解。
