GCN2-like eIF2α kinase manages the amino acid starvation response in Toxoplasma gondii.
GCN2-like eIF2α kinase manages the amino acid starvation response in Toxoplasma gondii.
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GCN2样EIF2α激酶管理弓形虫弓形虫中的氨基酸饥饿反应。
DOI：
10.1016/j.ijpara.2013.08.005
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发表时间：
2014-02
影响因子：
4
通讯作者：
Sullivan, William J., Jr.
中科院分区：
文献类型：
--
作者：
Konrad, Christian;Wek, Ronald C.;Sullivan, William J., Jr.
顶端复门原生动物弓形虫是一种重要的人类和兽医病原体。作为一种专性细胞内寄生虫，弓形虫依赖于宿主细胞提供的营养，并且需要适应可用资源的限制。在哺乳动物细胞中，通过真核翻译起始因子 2 (eIF2α) α 亚基的 GCN2 磷酸化进行的翻译调节是适应营养应激的关键机制。弓形虫编码两种 GCN2 样蛋白激酶：TgIF2K-C 和 TgIF2K-D。我们之前表明，TgIF2K-D 在从宿主细胞排出后磷酸化弓形虫 eIF2α (TgIF2α)，这使得寄生虫能够克服暴露于细胞外环境的问题。然而，TgIF2K-C 的功能仍未解决。为了确定 TgIF2K-C 在寄生虫中的功能，我们克隆了编码 TgIF2K-C 的 cDNA，并生成了该 TgIF2α 激酶的敲除寄生虫，以研究其在裂解周期中的功能。与亲代寄生虫相比，TgIF2K-C 敲除并未表现出适应性缺陷。然而，在感染随后在无谷氨酰胺培养基中培养的人成纤维细胞后，细胞内 TgIF2K-C 敲除寄生虫的 TgIF2α 诱导磷酸化受到阻碍，并且与亲代寄生虫相比，形成的噬菌斑数量减少了 50%。此外，我们发现无谷氨酰胺培养基中的这种生长缺陷在仅表达不可磷酸化的 TgIF2α (TgIF2α-S71A) 的寄生虫中被表型复制，但在 TgIF2K-D 敲除中却没有。这些研究表明，弓形虫 GCN2 样激酶 TgIF2K-C 和 TgIF2K-D 进化出在适应寄生虫环境变化方面具有不同的作用。
The apicomplexan protozoan Toxoplasma gondii is a significant human and veterinary pathogen. As an obligate intracellular parasite, Toxoplasma depends on nutrients provided by the host cell and needs to adapt to limitations in available resources. In mammalian cells, translational regulation via GCN2 phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 (eIF2α) is a key mechanism for adapting to nutrient stress. Toxoplasma encodes two GCN2-like protein kinases, TgIF2K-C and TgIF2K-D. We previously showed that TgIF2K-D phosphorylates T. gondii eIF2α (TgIF2α) upon egress from the host cell, which enables the parasite to overcome exposure to the extracellular environment. However, the function of TgIF2K-C remained unresolved. To determine the functions of TgIF2K-C in the parasite, we cloned the cDNA encoding TgIF2K-C and generated knockout parasites of this TgIF2α kinase to study its function during the lytic cycle. The TgIF2K-C knockout did not exhibit a fitness defect compared with parental parasites. However, upon infection of human fibroblasts that were subsequently cultured in glutamine-free medium, the intracellular TgIF2K-C knockout parasites were impeded for induced phosphorylation of TgIF2α and showed a 50% reduction in the number of plaques formed compared with parental parasites. Furthermore, we found that this growth defect in glutamine-free media was phenocopied in parasites expressing only a non-phosphorylatable TgIF2α (TgIF2α-S71A), but not in a TgIF2K-D knockout. These studies suggest that Toxoplasma GCN2-like kinases TgIF2K-C and TgIF2K-D evolved to have distinct roles in adapting to changes in the parasite’s environment.
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