scholarly journals Developmentally regulated PERK activity renders dendritic cells insensitive to subtilase cytotoxin-induced integrated stress response

2020 ◽  
Author(s):  
Andreia Mendes ◽  
Julien P. Gigan ◽  
Christian Rodriguez Rodrigues ◽  
Sébastien A. Choteau ◽  
Doriane Sanseau ◽  
...  
Keyword(s):  
Dendritic Cells ◽  
Stress Response ◽  
Mrna Translation ◽  
Initiation Factor ◽  
Integrated Stress Response ◽  
Developmentally Regulated ◽  
Translation Arrest ◽  
Eif2α Phosphorylation ◽  
Stressed Cells ◽  
Subtilase Cytotoxin

AbstractIn stressed cells, phosphorylation of eukaryotic initiation factor 2α (eIF2α) controls transcriptome-wide changes in mRNA translation and gene expression known as the integrated stress response (ISR). We show here that dendritic cells (DCs) display unusually high eIF2α phosphorylation, which is mostly caused by a developmentally regulated activation of the ER kinase PERK (EIF2AK3). Despite high p-eIF2α levels, differentiated DCs display active protein synthesis and no signs of a chronic ISR. eIF2α phosphorylation does not majorly impact DC differentiation nor cytokines production. It is however important to adapt protein homeostasis to the variations imposed on DCs by the immune or physiological contexts. This biochemical specificity prevents translation arrest and expression of the transcription factor ATF4 during ER-stress induction by subtilase cytotoxin or upon DC stimulation with bacterial lipopolysaccharides. This is also exemplified by the influence of the actin cytoskeleton dynamics on eIF2α phosphorylation and the migratory deficit observed in PERK-deficient DCs.

scholarly journals Proteostasis in dendritic cells is controlled by the PERK signaling axis independently of ATF4

2020 ◽  
Vol 4 (2) ◽  
pp. e202000865
Author(s):  
Andreia Mendes ◽  
Julien P Gigan ◽  
Christian Rodriguez Rodrigues ◽  
Sébastien A Choteau ◽  
Doriane Sanseau ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Stress Response ◽  
Mrna Translation ◽  
Initiation Factor ◽  
Integrated Stress Response ◽  
Translation Arrest ◽  
Eif2α Phosphorylation ◽  
Signaling Axis ◽  
Stressed Cells ◽  
Cytoskeleton Dynamics

In stressed cells, phosphorylation of eukaryotic initiation factor 2α (eIF2α) controls transcriptome-wide changes in mRNA translation and gene expression known as the integrated stress response. We show here that DCs are characterized by high eIF2α phosphorylation, mostly caused by the activation of the ER kinase PERK (EIF2AK3). Despite high p-eIF2α levels, DCs display active protein synthesis and no signs of a chronic integrated stress response. This biochemical specificity prevents translation arrest and expression of the transcription factor ATF4 during ER-stress induction by the subtilase cytotoxin (SubAB). PERK inactivation, increases globally protein synthesis levels and regulates IFN-β expression, while impairing LPS-stimulated DC migration. Although the loss of PERK activity does not impact DC development, the cross talk existing between actin cytoskeleton dynamics; PERK and eIF2α phosphorylation is likely important to adapt DC homeostasis to the variations imposed by the immune contexts.

scholarly journals Translation reinitiation at alternative open reading frames regulates gene expression in an integrated stress response

2004 ◽  
Vol 167 (1) ◽  
pp. 27-33 ◽  
Author(s):  
Phoebe D. Lu ◽  
Heather P. Harding ◽  
David Ron
Keyword(s):  
Gene Expression ◽  
Stress Response ◽  
Translational Regulation ◽  
Target Genes ◽  
Open Reading Frames ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Integrated Stress Response ◽  
Eif2α Phosphorylation ◽  
Stressed Cells

Stress-induced eukaryotic translation initiation factor 2 (eIF2) α phosphorylation paradoxically increases translation of the metazoan activating transcription factor 4 (ATF4), activating the integrated stress response (ISR), a pro-survival gene expression program. Previous studies implicated the 5′ end of the ATF4 mRNA, with its two conserved upstream ORFs (uORFs), in this translational regulation. Here, we report on mutation analysis of the ATF4 mRNA which revealed that scanning ribosomes initiate translation efficiently at both uORFs and ribosomes that had translated uORF1 efficiently reinitiate translation at downstream AUGs. In unstressed cells, low levels of eIF2α phosphorylation favor early capacitation of such reinitiating ribosomes directing them to the inhibitory uORF2, which precludes subsequent translation of ATF4 and represses the ISR. In stressed cells high levels of eIF2α phosphorylation delays ribosome capacitation and favors reinitiation at ATF4 over the inhibitory uORF2. These features are common to regulated translation of GCN4 in yeast. The metazoan ISR thus resembles the yeast general control response both in its target genes and its mechanistic details.

scholarly journals EMBR-32. INTEGRATED STRESS RESPONSE PLAYS A PRO-SURVIVAL ROLE IN MYC-DRIVEN MEDULLOBLASTOMA

2021 ◽  
Vol 23 (Supplement_1) ◽  
pp. i12-i13
Author(s):  
Sofya Langman ◽  
Alberto Delaidelli ◽  
Yue Zhou Huang ◽  
Poul Sorensen
Keyword(s):  
Stress Response ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Integrated Stress Response ◽  
Unfolded Proteins ◽  
Treatment Regimens ◽  
Eif2α Phosphorylation ◽  
Cancer Cell Death

Abstract Medulloblastoma (MB) accounts for 20% of diagnosed brain tumors in children. Group 3 (G3) MB subtype is the most aggressive. Molecularly, G3 MB is characterized by MYC overexpression, which drives elevated mRNA translation in tumor cells. PERK is an eukaryotic translation initiation factor 2 (eIF2α) kinase that inhibits mRNA translation under endoplasmic reticulum (ER) stress conditions, such as in response to accumulation of unfolded proteins. When unfolded proteins accumulate in the ER, activated PERK phosphorylates eIF2α. This shuts down global translation and triggers integrated stress response (ISR) to help cells adapt through selective translation of mRNA encoding pro-survival proteins. High mRNA expression of PERK correlates with poor survival in G3 MB patients. In vitro, combination of ER or hypoxic stress with PERK knockdown induces apoptosis in MB cells. ISRIB is an ISR inhibitor that maintains translation rates despite eIF2α phosphorylation. Combining ISRIB with stress such as hypoxia induces apoptosis in MB cells and prevents accumulation of key ISR mediators such as ATF4. In addition, combination of ISRIB and hypoxia induces oxidative stress. Current G3 MB treatment regimens include vincristine, a known ISR inducer. Combination of ISRIB with vincristine amplifies vincristine-induced apoptosis, potentially suggesting novel therapeutic approach for MB. Our findings show that inhibition of ISR in G3 MB represents a powerful inducer of cancer cell death.

scholarly journals Lysosomotropic agents including azithromycin, chloroquine and hydroxychloroquine activate the integrated stress response

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ai-Ling Tian ◽  
Qi Wu ◽  
Peng Liu ◽  
Liwei Zhao ◽  
Isabelle Martins ◽  
...  
Keyword(s):  
Stress Response ◽  
Immune Responses ◽  
Initiation Factor ◽  
Integrated Stress Response ◽  
Serine Residue ◽  
Eif2α Phosphorylation ◽  
Lysosomotropic Agents ◽  
Cultured Human Cells

AbstractThe integrated stress response manifests with the phosphorylation of eukaryotic initiation factor 2α (eIF2α) on serine residue 51 and plays a major role in the adaptation of cells to endoplasmic reticulum stress in the initiation of autophagy and in the ignition of immune responses. Here, we report that lysosomotropic agents, including azithromycin, chloroquine, and hydroxychloroquine, can trigger eIF2α phosphorylation in vitro (in cultured human cells) and, as validated for hydroxychloroquine, in vivo (in mice). Cells bearing a non-phosphorylatable eIF2α mutant (S51A) failed to accumulate autophagic puncta in response to azithromycin, chloroquine, and hydroxychloroquine. Conversely, two inhibitors of eIF2α dephosphorylation, nelfinavir and salubrinal, enhanced the induction of such autophagic puncta. Altogether, these results point to the unexpected capacity of azithromycin, chloroquine, and hydroxychloroquine to elicit the integrated stress response.

scholarly journals A point mutation in the nucleotide exchange factor eIF2B constitutively activates the integrated stress response by allosteric modulation

2021 ◽  
Author(s):  
Lan Wang ◽  
Morgane Boone ◽  
Rosalie E Lawrence ◽  
Adam Frost ◽  
Peter Walter ◽  
...  
Keyword(s):  
Stress Response ◽  
Point Mutation ◽  
Translational Control ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Integrated Stress Response ◽  
Nucleotide Exchange ◽  
Exchange Factor ◽  
Nucleotide Exchange Factor

AbstractIn eukaryotic cells, stressors reprogram the cellular proteome by activating the integrated stress response (ISR). In its canonical form, stress-sensing kinases phosphorylate the eukaryotic translation initiation factor eIF2 (eIF2-P), which ultimately leads to reduced levels of ternary complex required for initiation of mRNA translation. Translational control is primarily exerted through a conformational switch in eIF2’s nucleotide exchange factor, eIF2B, which shifts from its active A-State conformation to its inhibited I-State conformation upon eIF2-P binding, resulting in reduced nucleotide exchange on eIF2. Here, we show functionally and structurally how a single histidine to aspartate point mutation in eIF2B’s β subunit (H160D) mimics the effects of eIF2-P binding by promoting an I-State like conformation, resulting in eIF2-P independent activation of the ISR. These findings corroborate our previously proposed (Schoof et al. 2021) A/I-State model of allosteric ISR regulation.

scholarly journals Pharmacological dimerization and activation of the exchange factor eIF2B antagonizes the integrated stress response

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Carmela Sidrauski ◽  
Jordan C Tsai ◽  
Martin Kampmann ◽  
Brian R Hearn ◽  
Punitha Vedantham ◽  
...  
Keyword(s):  
Stress Response ◽  
Translational Control ◽  
Control Point ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Integrated Stress Response ◽  
Nucleotide Exchange ◽  
Eif2α Phosphorylation ◽  
Symmetric Molecule ◽  
Invaluable Tool

The general translation initiation factor eIF2 is a major translational control point. Multiple signaling pathways in the integrated stress response phosphorylate eIF2 serine-51, inhibiting nucleotide exchange by eIF2B. ISRIB, a potent drug-like small molecule, renders cells insensitive to eIF2α phosphorylation and enhances cognitive function in rodents by blocking long-term depression. ISRIB was identified in a phenotypic cell-based screen, and its mechanism of action remained unknown. We now report that ISRIB is an activator of eIF2B. Our reporter-based shRNA screen revealed an eIF2B requirement for ISRIB activity. Our results define ISRIB as a symmetric molecule, show ISRIB-mediated stabilization of activated eIF2B dimers, and suggest that eIF2B4 (δ-subunit) contributes to the ISRIB binding site. We also developed new ISRIB analogs, improving its EC50 to 600 pM in cell culture. By modulating eIF2B function, ISRIB promises to be an invaluable tool in proof-of-principle studies aiming to ameliorate cognitive defects resulting from neurodegenerative diseases.

scholarly journals An inhibitor of HIV-1 protease modulates constitutive eIF2α dephosphorylation to trigger a specific integrated stress response

2015 ◽  
Vol 113 (2) ◽  
pp. E117-E126 ◽  
Author(s):  
Aude De Gassart ◽  
Bojan Bujisic ◽  
Léa Zaffalon ◽  
Laurent A. Decosterd ◽  
Antonia Di Micco ◽  
...  
Keyword(s):  
Stress Response ◽  
Stress Responses ◽  
Translation Initiation Factor ◽  
Hiv Protease ◽  
Initiation Factor ◽  
Hiv Protease Inhibitors ◽  
Integrated Stress Response ◽  
Α Subunit ◽  
Eif2α Phosphorylation ◽  
Program Characteristic

Inhibitors of the HIV aspartyl protease [HIV protease inhibitors (HIV-PIs)] are the cornerstone of treatment for HIV. Beyond their well-defined antiretroviral activity, these drugs have additional effects that modulate cell viability and homeostasis. However, little is known about the virus-independent pathways engaged by these molecules. Here we show that the HIV-PI Nelfinavir decreases translation rates and promotes a transcriptional program characteristic of the integrated stress response (ISR). Mice treated with Nelfinavir display hallmarks of this stress response in the liver, including α subunit of translation initiation factor 2 (eIF2α) phosphorylation, activating transcription factor-4 (ATF4) induction, and increased expression of known downstream targets. Mechanistically, Nelfinavir-mediated ISR bypassed direct activation of the eIF2α stress kinases and instead relied on the inhibition of the constitutive eIF2α dephosphorylation and down-regulation of the phophatase cofactor CReP (Constitutive Repressor of eIF2α Phosphorylation; also known as PPP1R15B). These findings demonstrate that the modulation of eIF2α-specific phosphatase cofactor activity can be a rheostat of cellular homeostasis that initiates a functional ISR and suggest that the HIV-PIs could be repositioned as therapeutics in human diseases to modulate translation rates and stress responses.

scholarly journals The Integrated Stress Response and Phosphorylated Eukaryotic Initiation Factor 2α in Neurodegeneration

2020 ◽  
Vol 79 (2) ◽  
pp. 123-143 ◽  
Author(s):  
Sarah Bond ◽  
Claudia Lopez-Lloreda ◽  
Patrick J Gannon ◽  
Cagla Akay-Espinoza ◽  
Kelly L Jordan-Sciutto
Keyword(s):  
Stress Response ◽  
Molecular Mechanisms ◽  
Protein Translation ◽  
Cell Types ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Integrated Stress Response ◽  
Eukaryotic Initiation Factor ◽  
Pharmacological Agents ◽  
Eif2α Phosphorylation

Abstract The proposed molecular mechanisms underlying neurodegenerative pathogenesis are varied, precluding the development of effective therapies for these increasingly prevalent disorders. One of the most consistent observations across neurodegenerative diseases is the phosphorylation of eukaryotic initiation factor 2α (eIF2α). eIF2α is a translation initiation factor, involved in cap-dependent protein translation, which when phosphorylated causes global translation attenuation. eIF2α phosphorylation is mediated by 4 kinases, which, together with their downstream signaling cascades, constitute the integrated stress response (ISR). While the ISR is activated by stresses commonly observed in neurodegeneration, such as oxidative stress, endoplasmic reticulum stress, and inflammation, it is a canonically adaptive signaling cascade. However, chronic activation of the ISR can contribute to neurodegenerative phenotypes such as neuronal death, memory impairments, and protein aggregation via apoptotic induction and other maladaptive outcomes downstream of phospho-eIF2α-mediated translation inhibition, including neuroinflammation and altered amyloidogenic processing, plausibly in a feed-forward manner. This review examines evidence that dysregulated eIF2a phosphorylation acts as a driver of neurodegeneration, including a survey of observations of ISR signaling in human disease, inspection of the overlap between ISR signaling and neurodegenerative phenomenon, and assessment of recent encouraging findings ameliorating neurodegeneration using developing pharmacological agents which target the ISR. In doing so, gaps in the field, including crosstalk of the ISR kinases and consideration of ISR signaling in nonneuronal central nervous system cell types, are highlighted.

scholarly journals Mutagenesis screen uncovers lifespan extension through integrated stress response inhibition without reduced mRNA translation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Maxime J. Derisbourg ◽  
Laura E. Wester ◽  
Ruth Baddi ◽  
Martin S. Denzel
Keyword(s):  
Stress Response ◽  
Translation Initiation ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Lifespan Extension ◽  
Protein Homeostasis ◽  
Integrated Stress Response ◽  
Mutagenesis Screen

AbstractProtein homeostasis is modulated by stress response pathways and its deficiency is a hallmark of aging. The integrated stress response (ISR) is a conserved stress-signaling pathway that tunes mRNA translation via phosphorylation of the translation initiation factor eIF2. ISR activation and translation initiation are finely balanced by eIF2 kinases and by the eIF2 guanine nucleotide exchange factor eIF2B. However, the role of the ISR during aging remains poorly understood. Using a genomic mutagenesis screen for longevity inCaenorhabditis elegans, we define a role of eIF2 modulation in aging. By inhibiting the ISR, dominant mutations in eIF2B enhance protein homeostasis and increase lifespan. Consistently, full ISR inhibition using phosphorylation-defective eIF2α or pharmacological ISR inhibition prolong lifespan. Lifespan extension through impeding the ISR occurs without a reduction in overall protein synthesis. Instead, we observe changes in the translational efficiency of a subset of mRNAs, of which the putative kinasekin-35is required for lifespan extension. Evidently, lifespan is limited by the ISR and its inhibition may provide an intervention in aging.

scholarly journals Integrated Stress Response Deregulation underlies Vanishing White Matter and is a target for therapy

2018 ◽  
Author(s):  
Truus E.M. Abbink ◽  
Lisanne E. Wisse ◽  
Ermelinda Jaku ◽  
Michiel J. Thiecke ◽  
Daniel Voltolini-González ◽  
...  
Keyword(s):  
Stress Response ◽  
White Matter ◽  
Clinical Signs ◽  
Mrna Translation ◽  
Initiation Factor ◽  
Integrated Stress Response ◽  
Missense Mutations ◽  
Recessive Mutations ◽  
Mrna Markers ◽  
Vanishing White Matter

AbstractVanishing white matter (VWM) is a fatal, stress-sensitive leukodystrophy that mainly affects children and is currently without treatment. VWM is caused by recessive mutations in eukaryotic initiation factor 2B (eIF2B) that is crucial for initiation of mRNA translation and its regulation under stress conditions. Mice with bi-allelic missense mutations in eIF2B recapitulate human VWM. VWM pathomechanisms are unclear. Using polysomal profiling to screen for mRNAs with altered translation we observed most prominent changes in expression of integrated stress response (ISR) mRNAs in brains of mutant compared to wild-type mice; expression levels correlated with disease severity. We substantiated these findings in VWM patients’ brains. ISRIB, an ISR inhibitor, normalized expression of mRNA markers, ameliorated white matter pathology and improved motor skills in VWM mice, thus showing that the ISR is central in VWM pathomechanisms and a viable target for therapy.One Sentence SummaryISRIB ameliorates ISR deregulation and clinical signs in VWM mice

Sign in / Sign up

Export Citation Format

Share Document