Mutant eIF2B leads to impaired mitochondrial oxidative phosphorylation in vanishing white matter disease

Abstract

Eukaryotic translation initiation factor 2B (eIF2B) is a master regulator of protein synthesis under normal and stress conditions. Mutations in any of the five genes encoding its subunits lead to vanishing white matter (VWM) disease, a recessive genetic deadly illness caused by progressive loss of white matter in the brain. In this study we used fibroblasts, which are not involved in the disease, to demonstrate the involvement of eIF2B in mitochondrial function and abundance. Mass spectrometry of total proteome of mouse embryonic fibroblasts (MEFs) isolated from Eif2b5 mice revealed unbalanced stoichiometry of proteins involved in oxidative phosphorylation and of mitochondrial translation machinery components, among others. Mutant MEFs exhibit 55% decrease in oxygen consumption rate per mtDNA content and 47% increase in mitochondrial abundance (p < 0.005), reflecting adaptation to energy requirements. A more robust eIF2B-associated oxidative respiration deficiency was found in mutant primary astrocytes, which exhibit > 3-fold lower ATP-linked respiration per cell despite a 2-fold increase in mtDNA content (p < 0.03). The 2-fold increase in basal and stimulated glycolysis in mutant astrocytes (p ≤ 0.03), but not in MEFs, demonstrates their higher energetic needs and further explicates their involvement in the disease. The data demonstrate the critical role of eIF2B in tight coordination of expression from nuclear and mitochondrial genomes and illuminates the importance of mitochondrial function in VWM pathology. Further dissection of the signaling network associated with eIF2B function will help generating therapeutic strategies for VWM disease and possibly other neurodegenerative disorders.

EIF2B2 mutations in vanishing white matter disease hypersuppress translation and delay recovery during the integrated stress response

“…In support of this possibility, in response to LPS treatment astrocytes in mouse models of VWMD fail to fully induce cytokines and chemokines needed for astrogliosis and remyelination (Cabilly et al 2012). Finally, one has to anticipate that the translation rate of some specific mRNAs will be sensitive to even partial reduction in eIF2B function, and therefore VWMD cells will have alterations in their proteome, which is supported by an altered proteome in VWMD cells, and brains from VWMD mice as compared to control samples (Gat-Viks et al 2015;Raini et al 2017). This diversity of differences in translation suggests that VWMD could arise by a complex mixture of these different alterations.…”

Identification of Repurposable Cytoprotective Drugs in Vanishing White Matter Disease Patient-Derived cells

“…The eIF2B mutations in murine models have been shown to decrease mitochondrial membrane potential and impair mitochondrial complex I function, resulting in a compensatory increase in mitochondrial abundance (9). Furthermore, mutations in eIF2B genes impair mitochondrial function during oxidative stress conditions in VWMD murine broblasts and astrocytes (11).…”

“…VWMD mouse models and induced pluripotent stem cell (iPSC) models (7,8) have identi ed a central role for dysfunctional astrocytes in the development of VWMD, with evidence for astrocytic apoptosis (8) and an inability to promote oligodendrocyte maturation (6). A key driver of cellular pathogenesis in VWMD involves the ISR, with alterations in responses to endoplasmic reticulum stress and oxidative stress (9,10). Mitochondrial dysfunction and increased accumulation of reactive oxygen species have been identi ed in VWMD murine broblasts, astrocytes and oligodendrocyte precursor cells (11,12).…”

Doença da substância branca evanescente: caracterização por imagem, correlação clínica e molecular

“…11,13,15 Em nosso grupo de pacientes, antecedente de trauma ou infecção como gatilho da abertura do quadro estava presente em 38,4% 5 e um outro paciente no estudo de Rosemberg et al 5,24 Todos os pacientes deste estudo apresentaram mutação no gene EIF2B5, em concordância com sua maior prevalência também em outras populações. 10,12,15,20 Em comparação com outros estudos brasileiros, esta é a primeira casuística na qual todos os pacientes possuem diagnóstico molecular, além do diagnóstico clínico e por imagem. Em relação às áreas predominantemente afetadas da substância branca, a maioria apresentou predomínio frontoparietal, tanto do hiperssinal T2, quanto da degeneração cística, com relativa preservação dos lobos temporal e occipital, corroborando outros estudos.…”

“…15,19 sempre afetam o mesmo gene, ou seja, a mesma subunidade: 63% na subunidade ε, 19% na β, 12% na δ, e mais raramente na γ (4%) e na α (2%). 12,15,18,20 Há 18,22,24 Em relação às características de neuroimagem expressas por essa leucoencefalopatia, têmse critérios diagnósticos classicamente bem estabelecidos por van der Knaap et al em 1997.…”