scholarly journals Sugar phosphate activation of the stress sensor eIF2B

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Qi Hao ◽  
Jin-Mi Heo ◽  
Boguslaw P. Nocek ◽  
Kevin G. Hicks ◽  
Vincent S. Stoll ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Nutrient Status ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Sugar Phosphate ◽  
Metabolizing Enzymes ◽  
Cellular Processes ◽  
Phosphate Sensing ◽  
Sugar Phosphates ◽  
Vanishing White Matter Disease

AbstractThe multi-subunit translation initiation factor eIF2B is a control node for protein synthesis. eIF2B activity is canonically modulated through stress-responsive phosphorylation of its substrate eIF2. The eIF2B regulatory subcomplex is evolutionarily related to sugar-metabolizing enzymes, but the biological relevance of this relationship was unknown. To identify natural ligands that might regulate eIF2B, we conduct unbiased binding- and activity-based screens followed by structural studies. We find that sugar phosphates occupy the ancestral catalytic site in the eIF2Bα subunit, promote eIF2B holoenzyme formation and enhance enzymatic activity towards eIF2. A mutant in the eIF2Bα ligand pocket that causes Vanishing White Matter disease fails to engage and is not stimulated by sugar phosphates. These data underscore the importance of allosteric metabolite modulation for proper eIF2B function. We propose that eIF2B evolved to couple nutrient status via sugar phosphate sensing with the rate of protein synthesis, one of the most energetically costly cellular processes.

scholarly journals Correction of eIF2-dependent defects in brain protein synthesis, synaptic plasticity, and memory in mouse models of Alzheimer’s disease

2021 ◽  
Vol 14 (668) ◽  
pp. eabc5429
Author(s):  
Mauricio M. Oliveira ◽  
Mychael V. Lourenco ◽  
Francesco Longo ◽  
Nicole P. Kasica ◽  
Wenzhong Yang ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Protein Synthesis ◽  
Synaptic Plasticity ◽  
Translation Initiation ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Postmortem Brain Tissue ◽  
Phosphorylated Eif2α

Neuronal protein synthesis is essential for long-term memory consolidation, and its dysregulation is implicated in various neurodegenerative disorders, including Alzheimer’s disease (AD). Cellular stress triggers the activation of protein kinases that converge on the phosphorylation of eukaryotic translation initiation factor 2α (eIF2α), which attenuates mRNA translation. This translational inhibition is one aspect of the integrated stress response (ISR). We found that postmortem brain tissue from AD patients showed increased phosphorylation of eIF2α and reduced abundance of eIF2B, another key component of the translation initiation complex. Systemic administration of the small-molecule compound ISRIB (which blocks the ISR downstream of phosphorylated eIF2α) rescued protein synthesis in the hippocampus, measures of synaptic plasticity, and performance on memory-associated behavior tests in wild-type mice cotreated with salubrinal (which inhibits translation by inducing eIF2α phosphorylation) and in both β-amyloid-treated and transgenic AD model mice. Thus, attenuating the ISR downstream of phosphorylated eIF2α may restore hippocampal protein synthesis and delay cognitive decline in AD patients.

scholarly journals Protein synthesis persists during necrotic cell death

2005 ◽  
Vol 168 (4) ◽  
pp. 545-551 ◽  
Author(s):  
Xavier Saelens ◽  
Nele Festjens ◽  
Eef Parthoens ◽  
Isabel Vanoverberghe ◽  
Michael Kalai ◽  
...  
Keyword(s):  
Cell Death ◽  
Protein Synthesis ◽  
De Novo ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Necrotic Cell Death ◽  
Necrotic Cell ◽  
Proteolytic Activation ◽  
Double Stranded Rna ◽  
Molecular Events

Cell death is an intrinsic part of metazoan development and mammalian immune regulation. Whereas the molecular events orchestrating apoptosis have been characterized extensively, little is known about the biochemistry of necrotic cell death. Here, we show that, in contrast to apoptosis, the induction of necrosis does not lead to the shut down of protein synthesis. The rapid drop in protein synthesis observed in apoptosis correlates with caspase-dependent breakdown of eukaryotic translation initiation factor (eIF) 4G, activation of the double-stranded RNA-activated protein kinase PKR, and phosphorylation of its substrate eIF2-α. In necrosis induced by tumor necrosis factor, double-stranded RNA, or viral infection, de novo protein synthesis persists and 28S ribosomal RNA fragmentation, eIF2-α phosphorylation, and proteolytic activation of PKR are absent. Collectively, these results show that, in contrast to apoptotic cells, necrotic dying cells retain the opportunity to synthesize proteins.

scholarly journals Caspase-mediated cleavage of eukaryotic translation initiation factor subunit 2α

1999 ◽  
Vol 342 (1) ◽  
pp. 65-70 ◽  
Author(s):  
Shinya SATOH ◽  
Makoto HIJIKATA ◽  
Hiroshi HANDA ◽  
Kunitada SHIMOTOHNO
Keyword(s):  
Protein Synthesis ◽  
Translation Initiation ◽  
Caspase 3 ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation Initiation Factor ◽  
Α Subunit ◽  
Eukaryotic Translation ◽  
Initiation Of Translation ◽  
Eukaryotic Translation Initiation

Eukaryotic translation initiation factor 2α (eIF-2α), a target molecule of the interferon-inducible double-stranded-RNA-dependent protein kinase (PKR), was cleaved in apoptotic Saos-2 cells on treatment with poly(I)˙poly(C) or tumour necrosis factor α. This cleavage occurred with a time course similar to that of poly(ADP-ribose) polymerase, a well-known caspase substrate. In addition, eIF-2α was cleaved by recombinant active caspase-3 in vitro. By site-directed mutagenesis, the cleavage site was mapped to an Ala-Glu-Val-Asp300 ↓ Gly301 sequence located in the C-terminal portion of eIF-2α. PKR phosphorylates eIF-2α on Ser51, resulting in the suppression of protein synthesis. PKR-mediated translational suppression was repressed when the C-terminally cleaved product of eIF-2α was overexpressed in Saos-2 cells, even though PKR can phosphorylate this cleaved product. These results suggest that caspase-3 or related protease(s) can modulate the efficiency of protein synthesis by cleaving the α subunit of eIF-2, a key component in the initiation of translation.

scholarly journals Measles Virus N Protein Inhibits Host Translation by Binding to eIF3-p40

2007 ◽  
Vol 81 (21) ◽  
pp. 11569-11576 ◽  
Author(s):  
Hiroki Sato ◽  
Munemitsu Masuda ◽  
Moeko Kanai ◽  
Kyoko Tsukiyama-Kohara ◽  
Misako Yoneda ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Mammalian Cells ◽  
Measles Virus ◽  
Encephalomyocarditis Virus ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Translation System ◽  
Dependent Manner ◽  
Initiation Factors ◽  
Human T Cell

ABSTRACT The nonsegmented, negative-sense RNA genome of measles virus (MV) is encapsidated by the virus-encoded nucleocapsid protein (N). In this study, we searched for N-binding cellular proteins by using MV-N as bait and screening the human T-cell cDNA library by yeast two-hybrid assay and isolated the p40 subunit of eukaryotic initiation factor 3 (eIF3-p40) as a binding partner. The interaction between MV-N and eIF3-p40 in mammalian cells was confirmed by coimmunoprecipitation. Since eIF3-p40 is a translation initiation factor, we analyzed the potential inhibitory effect of MV-N on protein synthesis. Glutathione S-transferase (GST)-fused MV-N (GST-N) inhibited translation of reporter mRNAs in rabbit reticulocyte lysate translation system in a dose-dependent manner. Encephalomyocarditis virus internal ribosomal entry site-mediated translation, which requires canonical initiation factors to initiate translation, was also inhibited by GST-N. In contrast, a unique form of translation mediated by the intergenic region of Plautia stali intestine virus, which can assemble 80S ribosomes in the absence of canonical initiation factors, was scarcely affected by GST-N. In vivo expression of MV-N induced by the Cre/loxP switching system inhibited the synthesis of a transfected reporter protein, as well as overall protein synthesis. These results suggest that MV-N targets eIF3-p40 and may be involved in inhibiting MV-induced host translation.

Increase in Cap- and IRES-Dependent Protein Synthesis by Overproduction of Translation Initiation Factor eIF4G

2000 ◽  
Vol 277 (1) ◽  
pp. 117-123 ◽  
Author(s):  
Satoko Hayashi ◽  
Kazuhiro Nishimura ◽  
Tomomi Fukuchi-Shimogori ◽  
Keiko Kashiwagi ◽  
Kazuei Igarashi
Keyword(s):  
Protein Synthesis ◽  
Translation Initiation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Dependent Protein

scholarly journals eIF2B as a Target for Viral Evasion of PKR-Mediated Translation Inhibition

mBio ◽  
2020 ◽  
Vol 11 (4) ◽  
Author(s):  
Jennifer Deborah Wuerth ◽  
Matthias Habjan ◽  
Markus Kainulainen ◽  
Besim Berisha ◽  
Damien Bertheloot ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Protein Kinase ◽  
Nonstructural Protein ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Mammalian Host ◽  
Eukaryotic Initiation Factor ◽  
Α Subunit ◽  
Immune Factor

ABSTRACT RNA-activated protein kinase (PKR) is a major innate immune factor that senses viral double-stranded RNA (dsRNA) and phosphorylates eukaryotic initiation factor (eIF) 2α. Phosphorylation of the α subunit converts the eIF2αβγ complex into a stoichiometric inhibitor of eukaryotic initiation factor eIF2B, thus halting mRNA translation. To escape this protein synthesis shutoff, viruses have evolved countermechanisms such as dsRNA sequestration, eIF-independent translation by an internal ribosome binding site, degradation of PKR, or dephosphorylation of PKR or of phospho-eIF2α. Here, we report that sandfly fever Sicilian phlebovirus (SFSV) confers such a resistance without interfering with PKR activation or eIF2α phosphorylation. Rather, SFSV expresses a nonstructural protein termed NSs that strongly binds to eIF2B. Although NSs still allows phospho-eIF2α binding to eIF2B, protein synthesis and virus replication are unhindered. Hence, SFSV encodes a unique PKR antagonist that acts by rendering eIF2B resistant to the inhibitory action of bound phospho-eIF2α. IMPORTANCE RNA-activated protein kinase (PKR) is one of the most powerful antiviral defense factors of the mammalian host. PKR acts by phosphorylating mRNA translation initiation factor eIF2α, thereby converting it from a cofactor to an inhibitor of mRNA translation that strongly binds to initiation factor eIF2B. To sustain synthesis of their proteins, viruses are known to counteract this on the level of PKR or eIF2α or by circumventing initiation factor-dependent translation altogether. Here, we report a different PKR escape strategy executed by sandfly fever Sicilian virus (SFSV), a member of the increasingly important group of phleboviruses. We found that the nonstructural protein NSs of SFSV binds to eIF2B and protects it from inactivation by PKR-generated phospho-eIF2α. Protein synthesis is hence maintained and the virus can replicate despite ongoing full-fledged PKR signaling in the infected cells. Thus, SFSV has evolved a unique strategy to escape the powerful antiviral PKR.

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