Phosphorylation of Eukaryotic Initiation Factor-2α during Stress and Encystation in Entamoeba Species

PLoS Pathogens

Holland M. Hendrick¹  William J. Sullivan Jr.¹  Matthew A. Hapstack¹  Steven E. Sykes²  Lesly A. Temesvari²  Brenda H. Welter² 

[1] Department of Biological Sciences, Clemson University Clemson, South Carolina, United States of America;Eukaryotic Pathogens Innovation Center (EPIC) Clemson University Clemson, South Carolina, United States of America

关键词: Entamoeba histolytica;    Phosphorylation;    Polyribosomes;    Trophozoites;    Tetracyclines;    Oxidative stress;    Protein expression;    Glucose;   

DOI  :  10.1371/journal.ppat.1006085

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Entamoeba histolytica is an enteric pathogen responsible for amoebic dysentery and liver abscess. It alternates between the host-restricted trophozoite form and the infective environmentally-stable cyst stage. Throughout its lifecycle E. histolytica experiences stress, in part, from host immune pressure. Conversion to cysts is presumed to be a stress-response. In other systems, stress induces phosphorylation of a serine residue on eukaryotic translation initiation factor-2α (eIF2α). This inhibits eIF2α activity resulting in a general decline in protein synthesis. Genomic data reveal that E. histolytica possesses eIF2α (EheIF2α) with a conserved phosphorylatable serine at position 59 (Ser59). Thus, this pathogen may have the machinery for stress-induced translational control. To test this, we exposed cells to different stress conditions and measured the level of total and phospho-EheIF2α. Long-term serum starvation, long-term heat shock, and oxidative stress induced an increase in the level of phospho-EheIF2α, while short-term serum starvation, short-term heat shock, or glucose deprivation did not. Long-term serum starvation also caused a decrease in polyribosome abundance, which is in accordance with the observation that this condition induces phosphorylation of EheIF2α. We generated transgenic cells that overexpress wildtype EheIF2α, a non-phosphorylatable variant of eIF2α in which Ser59 was mutated to alanine (EheIF2α-S59A), or a phosphomimetic variant of eIF2α in which Ser59 was mutated to aspartic acid (EheIF2α-S59D). Consistent with the known functions of eIF2α, cells expressing wildtype or EheIF2α-S59D exhibited increased or decreased translation, respectively. Surprisingly, cells expressing EheIF2α-S59A also exhibited reduced translation. Cells expressing EheIF2α-S59D were more resistant to long-term serum starvation underscoring the significance of EheIF2α phosphorylation in managing stress. Finally, phospho-eIF2α accumulated during encystation in E. invadens, a model encystation system. Together, these data demonstrate that the eIF2α-dependent stress response system is operational in Entamoeba species.

【 授权许可】

CC BY