Paradoxical Sensitivity to an Integrated Stress Response Blocking Mutation in Vanishing White Matter Cells.
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 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 eIF2α on GEF by a contravening EIF2S1/eIF2αS51A 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 eIF2α 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.
Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
Yusuke
http://orcid.org/0000-0003-0345-1416
Y
Sekine
Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
Alisa
http://orcid.org/0000-0002-9885-6012
A
Zyryanova
Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
Ana
http://orcid.org/0000-0002-7230-3188
A
Crespillo-Casado
Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
Niko
http://orcid.org/0000-0002-4640-3724
N
Amin-Wetzel
Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
Heather P
http://orcid.org/0000-0002-7359-7974
HP
Harding
Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
David
http://orcid.org/0000-0002-3014-5636
D
Ron
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D059865:Endoplasmic Reticulum Stress / Q000235:genetics*; D020717:Eukaryotic Initiation Factor-2B / Q000737:chemistry / Q000235:genetics*; D006801:Humans; D009154:Mutation; D011995:Recombination, Genetic; D056811:Unfolded Protein Response / Q000235:genetics; D066127:White Matter / Q000166:cytology* / Q000378:metabolism
D020717:Eukaryotic Initiation Factor-2B