Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.
CSIR-Centre for Cellular and Molecular Biology, Hyderabad 50007, India.
Int J Mol Sci. 2021 Apr 12;22(8):3979. doi: 10.3390/ijms22083979.
parasites cycle between sand fly vectors and mammalian hosts, transforming from extracellular promastigotes that reside in the vectors' alimentary canal to obligatory intracellular non-motile amastigotes that are harbored by macrophages of the mammalian hosts. The transition between vector and host exposes them to a broad range of environmental conditions that induces a developmental program of gene expression, with translation regulation playing a key role. The genome encodes six paralogs of the cap-binding protein eIF4E. All six isoforms show a relatively low degree of conservation with eIF4Es of other eukaryotes, as well as among themselves. This variability could suggest that they have been assigned discrete roles that could contribute to their survival under the changing environmental conditions. Here, we describe LeishIF4E-5, a LeishIF4E paralog. Despite the low sequence conservation observed between LeishIF4E-5 and other LeishIF4Es, the three aromatic residues in its cap-binding pocket are conserved, in accordance with its cap-binding activity. However, the cap-binding activity of LeishIF4E-5 is restricted to the promastigote life form and not observed in amastigotes. The overexpression of LeishIF4E-5 shows a decline in cell proliferation and an overall reduction in global translation. Immuno-cytochemical analysis shows that LeishIF4E-5 is localized in the cytoplasm, with a non-uniform distribution. Mass spectrometry analysis of proteins that co-purify with LeishIF4E-5 highlighted proteins involved in RNA metabolism, along with two LeishIF4G paralogs, LeishIF4G-1 and LeishIF4G-2. These vary in their conserved eIF4E binding motif, possibly suggesting that they can form different complexes.
寄生虫在沙蝇媒介和哺乳动物宿主之间循环，从位于媒介消化道内的细胞外前鞭毛体转化为必须在哺乳动物宿主的巨噬细胞内寄生的无动力的内体无鞭毛体。在媒介和宿主之间的转换使它们暴露于广泛的环境条件下，诱导基因表达的发育程序，其中翻译调节起着关键作用。该基因组编码六类帽结合蛋白 eIF4E 的同源物。所有六种同工型与其他真核生物的 eIF4E 以及彼此之间都表现出相对较低的保守性。这种可变性可能表明它们被赋予了不同的角色，这有助于它们在不断变化的环境条件下生存。在这里，我们描述了 LeishIF4E-5，一种 LeishIF4E 同源物。尽管在 LeishIF4E-5 和其他 LeishIF4Es 之间观察到的序列保守性较低，但它的帽结合口袋中的三个芳香族残基是保守的，符合其帽结合活性。然而，LeishIF4E-5 的帽结合活性仅限于前鞭毛体生命形式，在无鞭毛体中观察不到。LeishIF4E-5 的过表达显示细胞增殖下降和整体翻译水平降低。免疫细胞化学分析表明，LeishIF4E-5 定位于细胞质中，分布不均匀。与 LeishIF4E-5 共纯化的蛋白质的质谱分析突出了参与 RNA 代谢的蛋白质，以及两种 LeishIF4G 同源物 LeishIF4G-1 和 LeishIF4G-2。它们的 eIF4E 结合基序存在差异，可能表明它们可以形成不同的复合物。
