Dataset Information

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

ABSTRACT: 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-2? (eIF2?). This inhibits eIF2? activity resulting in a general decline in protein synthesis. Genomic data reveal that E. histolytica possesses eIF2? (EheIF2?) 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-EheIF2?. Long-term serum starvation, long-term heat shock, and oxidative stress induced an increase in the level of phospho-EheIF2?, 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 EheIF2?. We generated transgenic cells that overexpress wildtype EheIF2?, a non-phosphorylatable variant of eIF2? in which Ser59 was mutated to alanine (EheIF2?-S59A), or a phosphomimetic variant of eIF2? in which Ser59 was mutated to aspartic acid (EheIF2?-S59D). Consistent with the known functions of eIF2?, cells expressing wildtype or EheIF2?-S59D exhibited increased or decreased translation, respectively. Surprisingly, cells expressing EheIF2?-S59A also exhibited reduced translation. Cells expressing EheIF2?-S59D were more resistant to long-term serum starvation underscoring the significance of EheIF2? phosphorylation in managing stress. Finally, phospho-eIF2? accumulated during encystation in E. invadens, a model encystation system. Together, these data demonstrate that the eIF2?-dependent stress response system is operational in Entamoeba species.

SUBMITTER: Hendrick HM

PROVIDER: S-EPMC5179133 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

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

Hendrick Holland M HM Welter Brenda H BH Hapstack Matthew A MA Sykes Steven E SE Sullivan William J WJ Temesvari Lesly A LA

PLoS pathogens 20161208 12

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 inhibit ...[more]

PMID: 27930733

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Project description:Entamoeba histolytica is an intestinal parasite infecting over 50 million people worldwide and is the causative agent of amebic dysentery and amoebic liver abscess. In the human host, E. histolytica experiences stress brought on by nutrient deprivation and the host immune response. To be a successful parasite, E. histolytica must counter the stress; therefore, understanding the stress response may uncover new drug targets. In many systems, the stress response includes down-regulation of protein translation, which is regulated by phosphorylation of eukaryotic initiation factor (eIF-2α). Previous work has demonstrated that phosphorylation of the E. histolytica eIF-2α (EheIF-2α) increases significantly when exposed to long-term serum starvation, oxidative stress, and long-term heat shock. However, the effects of reagents that are known to induce nitrosative or endoplasmic reticulum (ER) stresses, on EheIF-2α have yet to be evaluated. Nitrosative stress is part of the host's immune response and ER stress can be caused by several physiological or pathological factors. We treated E. histolytica cells with various reagents known to induce nitrosative stress (DPTA-NONOate and SNP) or ER stress (BFA and DTT). We examined the morphology of the ER, tracked phosphorylation of EheIF-2α, and assessed protein translation in control and stressed cells. While all four stress-inducing reagents caused a global reduction in protein translation, only DTT was capable of also inducing changes in the morphology of the ER (consistent with ER stress) and phosphorylation of EheIF-2α. This suggests that DTT authentically induces ER stress in E. histolytica and that this stress is managed by the eIF-2α-based system. This was supported by the observation that cells expressing a non-phosphorylatable version of eIF-2α were also highly sensitive to DTT-stress. Since protein translation decreased in the absence of phosphorylation of eIF-2α (after treatment with DPTA-NONOate, SNP or BFA), the data also indicate that there are alternative protein-translational control pathways in E. histolytica. Overall, our study further illuminates the stress response to nitrosative stress and ER stress in E. histolytica.

Dataset Information

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

Publications

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

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