Heme is an essential cofactor for many biological processes in aerobic organisms, which can synthesize it de novo through a conserved pathway. Trypanosoma cruzi, the etiological agent of Chagas disease, as well as other trypanosomatids relevant to human health, are heme auxotrophs, meaning they must import it from their mammalian hosts or insect vectors. However, how these species import and regulate heme levels is not fully defined yet. It is known that the membrane protein TcHTE is involved in T. cruzi heme transport, although its specific role remains unclear. In the present work, we studied endogenous TcHTE in the different life cycle stages of the parasite to gain insight into its function in heme transport and homeostasis. We have confirmed that TcHTE is predominantly detected in replicative stages (epimastigote and amastigote), in which heme transport activity was previously validated. We also showed that in epimastigotes, TcHTE protein and mRNA levels decrease in response to increments in heme concentration, confirming it as a member of the heme response gene family. Finally, we demonstrated that T. cruzi epimastigotes can sense intracellular heme by an unknown mechanism and regulate heme transport to adapt to changing conditions. Based on these results, we propose a model in which T. cruzi senses intracellular heme and regulates heme transport activity by adjusting the expression of TcHTE. The elucidation and characterization of heme transport and homeostasis will contribute to a better understanding of a critical pathway for T. cruzi biology allowing the identification of novel and essential proteins.

译文

血红素是需氧生物中许多生物过程必不可少的辅因子,可以通过保守的途径从头合成。克氏锥虫是恰加氏病的病原体,以及与人类健康相关的其他锥虫,是血红素营养缺陷型动物,这意味着它们必须从哺乳动物宿主或昆虫媒介中进口。但是,这些物种如何导入和调节血红素水平尚未完全确定。众所周知,膜蛋白TcHTE参与了克氏T。克氏血红素的转运,尽管其具体作用尚不清楚。在目前的工作中,我们研究了寄生虫不同生命周期阶段的内源性TcHTE,以了解其在血红素转运和体内平衡中的功能。我们已经确认,TcHTE主要在复制阶段 (epimastigote和amastigote) 检测到,其中血红素运输活性先前已得到验证。我们还表明,在epimastigotes中,TcHTE蛋白和mRNA水平随着血红素浓度的增加而降低,这证实了它是血红素反应基因家族的成员。最后,我们证明了克氏T. cruzi epimastigotes可以通过未知机制感知细胞内血红素,并调节血红素转运以适应不断变化的条件。基于这些结果,我们提出了一个模型,其中T。cruzi通过调节TcHTE的表达来感知细胞内血红素并调节血红素转运活性。血红素转运和稳态的阐明和表征将有助于更好地理解克鲁氏杆菌生物学的关键途径,从而可以鉴定新的和必需的蛋白质。

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