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Paradoxical Sensitivity to an Integrated Stress Response Blocking Mutation in Vanishing White Matter Cells.

ABSTRACT: The eukaryotic translation initiation factor eIF2B promotes mRNA translation as a guanine nucleotide exchange factor (GEF) for translation initiation factor 2 (eIF2). Endoplasmic reticulum (ER) stress-mediated activation of the kinase PERK and the resultant phosphorylation of eIF2's alpha subunit (eIF2?) attenuates eIF2B GEF activity thereby inducing an integrated stress response (ISR) that defends against protein misfolding in the ER. Mutations in all five subunits of human eIF2B cause an inherited leukoencephalopathy with vanishing white matter (VWM), but the role of the ISR in its pathogenesis remains unclear. Using CRISPR-Cas9 genome editing we introduced the most severe known VWM mutation, EIF2B4A391D, into CHO cells. Compared to isogenic wildtype cells, GEF activity of cells with the VWM mutation was impaired and the mutant cells experienced modest enhancement of the ISR. However, despite their enhanced ISR, imposed by the intrinsic defect in eIF2B, disrupting the inhibitory effect of phosphorylated eIF2? on GEF by a contravening EIF2S1/eIF2?S51A mutation that functions upstream of eIF2B, selectively enfeebled both EIF2B4A391D and the related severe VWM EIF2B4R483W cells. The basis for paradoxical dependence of cells with the VWM mutations on an intact eIF2? genotype remains unclear, as both translation rates and survival from stressors that normally activate the ISR were not reproducibly affected by the VWM mutations. Nonetheless, our findings support an additional layer of complexity in the development of VWM, beyond a hyperactive ISR.

SUBMITTER: Sekine Y

PROVIDER: S-EPMC5094784 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Paradoxical Sensitivity to an Integrated Stress Response Blocking Mutation in Vanishing White Matter Cells.

Sekine Yusuke Y Zyryanova Alisa A Crespillo-Casado Ana A Amin-Wetzel Niko N Harding Heather P HP Ron David D

PloS one 20161103 11

The eukaryotic translation initiation factor eIF2B promotes mRNA translation as a guanine nucleotide exchange factor (GEF) for translation initiation factor 2 (eIF2). Endoplasmic reticulum (ER) stress-mediated activation of the kinase PERK and the resultant phosphorylation of eIF2's alpha subunit (eIF2α) attenuates eIF2B GEF activity thereby inducing an integrated stress response (ISR) that defends against protein misfolding in the ER. Mutations in all five subunits of human eIF2B cause an inher ...[more]

PMID: 27812215

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Project description:Vanishing white matter (VWM) is a leukodystrophy caused by biallelic pathogenic variants in eukaryotic translation initiation factor 2B. Neuropathology includes lack of reactive gliosis, paucity of myelin, and axonal abnormalities. Alteration in proteins involved in cellular metabolism has also been implicated in the disease. It, however, remains unclear which factors contribute to VWM pathogenesis. Here, we aimed at gaining insight into the basis of VWM pathogenesis using the 2b5ho mouse model of VWM. We first investigated the temporal proteome in the cerebellum, corpus callosum, cortex, and brainstem of 2b5ho and wild type (WT) mice. Protein changes observed in 2b5ho mice were then cross-referenced with published proteomic datasets from post mortem VWM patient brain tissue to define alterations relevant to the human disease. By comparing 2b5ho mice with their region- and age-matched WT counterparts, we identified region-specific protein changes associated with disease development and progression. We showed that the proteome in the cerebellum and cortex of 2b5ho mice was already deregulated prior to pathology development, whereas proteome changes in the corpus callosum only occurred after onset of pathology. Remarkably, protein changes in the brainstem were transient, indicating that a compensatory mechanism might occur in this region throughout the disease course. Gene ontology overrepresentation analysis revealed that proteome changes observed in 2b5ho mouse brains reflect alterations in features well-known in VWM. Side-by-side comparison of the 2b5ho mouse and VWM patient brain proteomes revealed that part of protein changes were the same as in VWM patients. These could represent relevant changes that contribute to the disease or even drive its progression in VWM patients. Taken together, we show that the proteome in the brain of 2b5ho mice is affected in a region-specific and time-dependent manner. We found that the 2b5ho mouse model partly replicates the human disease at the protein level, and provides a spatiotemporal proteome resource to study aspects of VWM pathogenesis. This resource highlights alterations presenting from early to late disease stages, and those that possibly drive disease progression.

Dataset Information

Paradoxical Sensitivity to an Integrated Stress Response Blocking Mutation in Vanishing White Matter Cells.

Publications

Paradoxical Sensitivity to an Integrated Stress Response Blocking Mutation in Vanishing White Matter Cells.

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