scholarly journals The Energy Status of Astrocytes Is the Achilles’ Heel of eIF2B-Leukodystrophy

Cells ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1858
Author(s):  
Melisa Herrero ◽  
Maron Daw ◽  
Andrea Atzmon ◽  
Orna Elroy-Stein

Translation initiation factor 2B (eIF2B) is a master regulator of global protein synthesis in all cell types. The mild genetic Eif2b5(R132H) mutation causes a slight reduction in eIF2B enzymatic activity which leads to abnormal composition of mitochondrial electron transfer chain complexes and impaired oxidative phosphorylation. Previous work using primary fibroblasts isolated from Eif2b5(R132H/R132H) mice revealed that owing to increased mitochondrial biogenesis they exhibit normal cellular ATP level. In contrast to fibroblasts, here we show that primary astrocytes isolated from Eif2b5(R132H/R132H) mice are unable to compensate for their metabolic impairment and exhibit chronic state of low ATP level regardless of extensive adaptation efforts. Mutant astrocytes are hypersensitive to oxidative stress and to further energy stress. Moreover, they show migration deficit upon exposure to glucose starvation. The mutation in Eif2b5 prompts reactive oxygen species (ROS)-mediated inferior ability to stimulate the AMP-activated protein kinase (AMPK) axis, due to a requirement to increase the mammalian target of rapamycin complex-1 (mTORC1) signalling in order to enable oxidative glycolysis and generation of specific subclass of ROS-regulating proteins, similar to cancer cells. The data disclose the robust impact of eIF2B on metabolic and redox homeostasis programs in astrocytes and point at their hyper-sensitivity to mutated eIF2B. Thereby, it illuminates the central involvement of astrocytes in Vanishing White Matter Disease (VWMD), a genetic neurodegenerative leukodystrophy caused by homozygous hypomorphic mutations in genes encoding any of the 5 subunits of eIF2B.

2014 ◽  
Vol 6 ◽  
pp. JCNSD.S13540 ◽  
Author(s):  
Eulàlia Turón-Viñas ◽  
Mercè Pineda ◽  
Victòria Cusí ◽  
Eduardo López-Laso ◽  
Rebeca Losada Del Pozo ◽  
...  

Vanishing white matter (VWM) leukoencephalopathy is one of the most prevalent hereditary white matter diseases. It has been associated with mutations in genes encoding eukaryotic translation initiation factor ( eIF2B). We have compiled a list of all the patients diagnosed with VWM in Spain; we found 21 children. The first clinical manifestation in all of them was spasticity, with severe ataxia in six patients, hemiparesis in one child, and dystonic movements in another. They suffered from progressive cognitive deterioration and nine of them had epilepsy too. In four children, we observed optic atrophy and three also had progressive macrocephaly, which is not common in VWM disease. The first two cases were diagnosed before the 1980s. Therefore, they were diagnosed by necropsy studies. The last 16 patients were diagnosed according to genetics: we found mutations in the genes eIF2B5 (13 cases), eIF2B3 (2 cases), and eIF2B4 (1 case). In our report, the second mutation in frequency was c.318A>T; patients with this mutation all followed a slow chronic course, both in homozygous and heterozygous states. Previously, there were no other reports to confirm this fact. We also found some mutations not described in previous reports: c.1090C>T in eIF2B4, c.314A>G in eIF2B5, and c.877C>T in eIF2B5.


2020 ◽  
Vol 7 (6) ◽  
pp. 1438
Author(s):  
Bommidi Navya ◽  
Vamshi Krishna Kondle ◽  
Komal Uppal

Vanishing white matter disease (VWM) is one of the most prevalent inherited childhood leucoencephalopathies. Childhood ataxia and diffuse central nervous system hypomyelination are the common findings. The disease is characterized by chronic progressive and episodic deterioration with ataxia, spasticity and optic atrophy. VWM is caused by mutation in any of the five genes encoding the subunits of eukaryotic translation initiation factor eIF2B. The disease has an autosomal recessive mode of inheritance. The cause of the disease is unknown. Authors are reporting an 8 year old male child presented with complaint of difficulty while walking since one month and history viral fever was present one month back. MRI revealed bilateral symmetrical periventricular T2 hyperintensities with T1 hypointensities. Perivenular sparing was seen and molecular analysis shown eIF2B4 mutations confirmation of vanishing white matter disease. No specific treatment is available and advised to avoid stress and triggers.


2021 ◽  
Vol 118 (15) ◽  
pp. e2025522118
Author(s):  
Vijendra Sharma ◽  
Rapita Sood ◽  
Danning Lou ◽  
Tzu-Yu Hung ◽  
Maxime Lévesque ◽  
...  

The mechanistic/mammalian target of rapamycin complex 1 (mTORC1) integrates multiple signals to regulate critical cellular processes such as mRNA translation, lipid biogenesis, and autophagy. Germline and somatic mutations in mTOR and genes upstream of mTORC1, such as PTEN, TSC1/2, AKT3, PIK3CA, and components of GATOR1 and KICSTOR complexes, are associated with various epileptic disorders. Increased mTORC1 activity is linked to the pathophysiology of epilepsy in both humans and animal models, and mTORC1 inhibition suppresses epileptogenesis in humans with tuberous sclerosis and animal models with elevated mTORC1 activity. However, the role of mTORC1-dependent translation and the neuronal cell types mediating the effect of enhanced mTORC1 activity in seizures remain unknown. The eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) and 2 (4E-BP2) are translational repressors downstream of mTORC1. Here we show that the ablation of 4E-BP2, but not 4E-BP1, in mice increases the sensitivity to pentylenetetrazole (PTZ)- and kainic acid (KA)–induced seizures. We demonstrate that the deletion of 4E-BP2 in inhibitory, but not excitatory neurons, causes an increase in the susceptibility to PTZ-induced seizures. Moreover, mice lacking 4E-BP2 in parvalbumin, but not somatostatin or VIP inhibitory neurons exhibit a lowered threshold for seizure induction and reduced number of parvalbumin neurons. A mouse model harboring a human PIK3CA mutation that enhances the activity of the PI3K-AKT pathway (Pik3caH1047R-Pvalb) selectively in parvalbumin neurons shows susceptibility to PTZ-induced seizures. Our data identify 4E-BP2 as a regulator of epileptogenesis and highlight the central role of increased mTORC1-dependent translation in parvalbumin neurons in the pathophysiology of epilepsy.


2015 ◽  
Vol 35 (20) ◽  
pp. 3517-3527 ◽  
Author(s):  
Tadashi Nakagawa ◽  
Takaaki Araki ◽  
Makiko Nakagawa ◽  
Atsushi Hirao ◽  
Michiaki Unno ◽  
...  

The kinase mTOR (mammalian target of rapamycin) promotes translation as well as cell survival and proliferation under nutrient-rich conditions. Whereas mTOR activates translation through ribosomal protein S6 kinase (S6K) and eukaryotic translation initiation factor 4E-binding protein (4E-BP), how it facilitates cell proliferation has remained unclear. We have now identified p19Arf, an inhibitor of cell cycle progression, as a novel substrate of S6K that is targeted to promote cell proliferation. Serum stimulation induced activation of the mTOR-S6K axis and consequent phosphorylation of p19Arfat Ser75. Phosphorylated p19Arfwas then recognized by the F-box protein β-TrCP2 and degraded by the proteasome. Ablation of β-TrCP2 thus led to the arrest of cell proliferation as a result of the stabilization and accumulation of p19Arf. The β-TrCP2 paralog β-TrCP1 had no effect on p19Arfstability, suggesting that phosphorylated p19Arfis a specific substrate of β-TrCP2. Mice deficient in β-TrCP2 manifested accumulation of p19Arfin the yolk sac and diedin utero. Our results suggest that the mTOR pathway promotes cell proliferation via β-TrCP2-dependent p19Arfdegradation under nutrient-rich conditions.


Author(s):  
Lucca Pietro Camillo dos Santos ◽  
Bruno Moisés de Matos ◽  
Brenda Cecilia de Maman Ribeiro ◽  
Nilson Ivo Tonin Zanchin ◽  
Beatriz Gomes Guimarães

Kinetoplastida, a class of early-diverging eukaryotes that includes pathogenic Trypanosoma and Leishmania species, display key differences in their translation machinery compared with multicellular eukaryotes. One of these differences involves a larger number of genes encoding eIF4E and eIF4G homologs and the interaction pattern between the translation initiation factors. eIF4G is a scaffold protein which interacts with the mRNA cap-binding factor eIF4E, the poly(A)-binding protein, the RNA helicase eIF4A and the eIF3 complex. It contains the so-called middle domain of eIF4G (MIF4G), a multipurpose adaptor involved in different protein–protein and protein–RNA complexes. Here, the crystal structure of the MIF4G domain of T. cruzi EIF4G5 is described at 2.4 Å resolution, which is the first three-dimensional structure of a trypanosomatid MIF4G domain to be reported. Structural comparison with IF4G homologs from other eukaryotes and other MIF4G-containing proteins reveals differences that may account for the specific interaction mechanisms of MIF4G despite its highly conserved overall fold.


2005 ◽  
Vol 122 (4) ◽  
pp. 529-543 ◽  
Author(s):  
Greco Hernández ◽  
Michael Altmann ◽  
José Manuel Sierra ◽  
Henning Urlaub ◽  
Ruth Diez del Corral ◽  
...  

2003 ◽  
Vol 285 (4) ◽  
pp. E754-E762 ◽  
Author(s):  
Stephen J. Crozier ◽  
Joshua C. Anthony ◽  
Charles M. Schworer ◽  
Ali K. Reiter ◽  
Tracy G. Anthony ◽  
...  

The purpose of the study described herein was to investigate how the mammalian target of rapamycin (mTOR)-signaling pathway and eukaryotic initiation factor 2B (eIF2B) activity, both having key roles in the translational control of protein synthesis in skeletal muscle, are regulated in cardiac muscle of rats in response to two different models of altered free fatty acid (FFA) and insulin availability. Protein synthetic rates were reduced in both gastrocnemius and heart of 3-day diabetic rats. The reduction was associated with diminished mTOR-mediated signaling and eIF2B activity in the gastrocnemius but only with diminished mTOR signaling in the heart. In response to the combination of acute hypoinsulinemia and hypolipidemia induced by administration of niacin, protein synthetic rates were also diminished in both gastrocnemius and heart. The niacin-induced changes were associated with diminished mTOR signaling and eIF2B activity in the heart but only with decreased mTOR signaling in the gastrocnemius. In the heart, mTOR signaling and eIF2B activity correlated with cellular energy status and/or redox potential. Thus FFAs may contribute to the translational control of protein synthesis in the heart but not in the gastrocnemius. In contrast, insulin, but not FFAs, is required for the maintenance of protein synthesis in the gastrocnemius.


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