scholarly journals Reduced BMPR2 expression induces GM-CSF translation and macrophage recruitment in humans and mice to exacerbate pulmonary hypertension

2014 ◽  
Vol 211 (2) ◽  
pp. 263-280 ◽  
Author(s):  
Hirofumi Sawada ◽  
Toshie Saito ◽  
Nils P. Nickel ◽  
Tero-Pekka Alastalo ◽  
Jason P. Glotzbach ◽  
...  
Keyword(s):  
Messenger Rna ◽  
Mrna Translation ◽  
Inflammatory Cells ◽  
Stress Granule ◽  
Translation Initiation Factor ◽  
Mitogen Activated Protein Kinase ◽  
Initiation Factor ◽  
Granule Formation ◽  
Gm Csf ◽  
Protein Receptor

Idiopathic pulmonary arterial hypertension (PAH [IPAH]) is an insidious and potentially fatal disease linked to a mutation or reduced expression of bone morphogenetic protein receptor 2 (BMPR2). Because intravascular inflammatory cells are recruited in IPAH pathogenesis, we hypothesized that reduced BMPR2 enhances production of the potent chemokine granulocyte macrophage colony-stimulating factor (GM-CSF) in response to an inflammatory perturbation. When human pulmonary artery (PA) endothelial cells deficient in BMPR2 were stimulated with tumor necrosis factor (TNF), a twofold increase in GM-CSF was observed and related to enhanced messenger RNA (mRNA) translation. The mechanism was associated with disruption of stress granule formation. Specifically, loss of BMPR2 induced prolonged phospho-p38 mitogen-activated protein kinase (MAPK) in response to TNF, and this increased GADD34–PP1 phosphatase activity, dephosphorylating eukaryotic translation initiation factor (eIF2α), and derepressing GM-CSF mRNA translation. Lungs from IPAH patients versus unused donor controls revealed heightened PA expression of GM-CSF co-distributing with increased TNF and expanded populations of hematopoietic and endothelial GM-CSF receptor α (GM-CSFRα)–positive cells. Moreover, a 3-wk infusion of GM-CSF in mice increased hypoxia-induced PAH, in association with increased perivascular macrophages and muscularized distal arteries, whereas blockade of GM-CSF repressed these features. Thus, reduced BMPR2 can subvert a stress granule response, heighten GM-CSF mRNA translation, increase inflammatory cell recruitment, and exacerbate PAH.

scholarly journals The Leader Protein of Theiler's Virus Prevents the Activation of PKR

2019 ◽  
Vol 93 (19) ◽  
Author(s):  
Fabian Borghese ◽  
Frédéric Sorgeloos ◽  
Teresa Cesaro ◽  
Thomas Michiels
Keyword(s):  
Stress Granule ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Wild Type Virus ◽  
Granule Formation ◽  
Double Stranded Rna ◽  
Eif2α Phosphorylation ◽  
Leader Protein ◽  
Infected Cells ◽  
L Proteins

ABSTRACT Leader (L) proteins encoded by cardioviruses are multifunctional proteins that contribute to innate immunity evasion. L proteins of Theiler’s murine encephalomyelitis virus (TMEV), Saffold virus (SAFV), and encephalomyocarditis virus (EMCV) were reported to inhibit stress granule assembly in infected cells. Here, we show that TMEV L can act at two levels in the stress granule formation pathway: on the one hand, it can inhibit sodium arsenite-induced stress granule assembly without preventing eIF2α phosphorylation and, thus, acts downstream of eIF2α; on the other hand, it can inhibit eucaryotic translation initiation factor 2 alpha kinase 2 (PKR) activation and the consequent PKR-mediated eIF2α phosphorylation. Interestingly, coimmunostaining experiments revealed that PKR colocalizes with viral double-stranded RNA (dsRNA) in cells infected with L-mutant viruses but not in cells infected with the wild-type virus. Furthermore, PKR coprecipitated with dsRNA from cells infected with L-mutant viruses significantly more than from cells infected with the wild-type virus. These data strongly suggest that L blocks PKR activation by preventing the interaction between PKR and viral dsRNA. In infected cells, L also rendered PKR refractory to subsequent activation by poly(I·C). However, no interaction was observed between L and either dsRNA or PKR. Taken together, our results suggest that, unlike other viral proteins, L indirectly acts on PKR to negatively regulate its responsiveness to dsRNA. IMPORTANCE The leader (L) protein encoded by cardioviruses is a very short multifunctional protein that contributes to evasion of the host innate immune response. This protein notably prevents the formation of stress granules in infected cells. Using Theiler’s virus as a model, we show that L proteins can act at two levels in the stress response pathway leading to stress granule formation, the most striking one being the inhibition of eucaryotic translation initiation factor 2 alpha kinase 2 (PKR) activation. Interestingly, the leader protein appears to inhibit PKR via a novel mechanism by rendering this kinase unable to detect double-stranded RNA, its typical activator. Unlike other viral proteins, such as influenza virus NS1, the leader protein appears to interact with neither PKR nor double-stranded RNA, suggesting that it acts indirectly to trigger the inhibition of the kinase.

scholarly journals Regulation of Stress Granule Formation by Inflammation, Vascular Injury, and Atherosclerosis

2019 ◽  
Vol 39 (10) ◽  
pp. 2014-2027 ◽  
Author(s):  
Allison B. Herman ◽  
Milessa Silva Afonso ◽  
Sheri E. Kelemen ◽  
Mitali Ray ◽  
Christine N. Vrakas ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Rna Binding ◽  
Binding Protein ◽  
Muscle Cells ◽  
Stress Granule ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Granule Formation ◽  
Altered Expression

Objective: Stress granules (SGs) are dynamic cytoplasmic aggregates containing mRNA, RNA-binding proteins, and translation factors that form in response to cellular stress. SGs have been shown to contribute to the pathogenesis of several human diseases, but their role in vascular diseases is unknown. This study shows that SGs accumulate in vascular smooth muscle cells (VSMCs) and macrophages during atherosclerosis. Approach and Results: Immunohistochemical analysis of atherosclerotic plaques from LDLR − /− mice revealed an increase in the stress granule-specific markers Ras-G3BP1 (GTPase-activating protein SH3 domain-binding protein) and PABP (poly-A-binding protein) in intimal macrophages and smooth muscle cells that correlated with disease progression. In vitro, PABP+ and G3BP1+ SGs were rapidly induced in VSMC and bone marrow–derived macrophages in response to atherosclerotic stimuli, including oxidized low-density lipoprotein and mediators of mitochondrial or oxidative stress. We observed an increase in eIF2α (eukaryotic translation initiation factor 2-alpha) phosphorylation, a requisite for stress granule formation, in cells exposed to these stimuli. Interestingly, SG formation, PABP expression, and eIF2α phosphorylation in VSMCs is reversed by treatment with the anti-inflammatory cytokine interleukin-19. Microtubule inhibitors reduced stress granule accumulation in VSMC, suggesting cytoskeletal regulation of stress granule formation. SG formation in VSMCs was also observed in other vascular disease pathologies, including vascular restenosis. Reduction of SG component G3BP1 by siRNA significantly altered expression profiles of inflammatory, apoptotic, and proliferative genes. Conclusions: These results indicate that SG formation is a common feature of the vascular response to injury and disease, and that modification of inflammation reduces stress granule formation in VSMC.

scholarly journals eIF-Three to Tango: emerging functions of translation initiation factor eIF3 in protein synthesis and disease

2020 ◽  
Vol 12 (6) ◽  
pp. 403-409 ◽  
Author(s):  
Dieter A Wolf ◽  
Yingying Lin ◽  
Haoran Duan ◽  
Yabin Cheng
Keyword(s):  
Protein Synthesis ◽  
Messenger Rna ◽  
Protein Production ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Protein Homeostasis ◽  
Subcellular Targeting ◽  
Post Translational Modifications ◽  
The Past

Abstract Studies over the past three years have substantially expanded the involvements of eukaryotic initiation factor 3 (eIF3) in messenger RNA (mRNA) translation. It now appears that this multi-subunit complex is involved in every possible form of mRNA translation, controlling every step of protein synthesis from initiation to elongation, termination, and quality control in positive as well as negative fashion. Through the study of eIF3, we are beginning to appreciate protein synthesis as a highly integrated process coordinating protein production with protein folding, subcellular targeting, and degradation. At the same time, eIF3 subunits appear to have specific functions that probably vary between different tissues and individual cells. Considering the broad functions of eIF3 in protein homeostasis, it comes as little surprise that eIF3 is increasingly implicated in major human diseases and first attempts at therapeutically targeting eIF3 have been undertaken. Much remains to be learned, however, about subunit- and tissue-specific functions of eIF3 in protein synthesis and disease and their regulation by environmental conditions and post-translational modifications.

scholarly journals MNK-eIF4E signalling is a highly conserved mechanism for sensory neuron axonal plasticity: evidence from Aplysia californica

2019 ◽  
Vol 374 (1785) ◽  
pp. 20190289 ◽  
Author(s):  
Sandra M. Mihail ◽  
Andi Wangzhou ◽  
Kumud K. Kunjilwar ◽  
Jamie K. Moy ◽  
Gregory Dussor ◽  
...  
Keyword(s):  
Sensory Neuron ◽  
Sensory Neurons ◽  
Therapeutic Potential ◽  
Aplysia Californica ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Mitogen Activated Protein Kinase ◽  
Initiation Factor ◽  
Translation Regulation ◽  
Eukaryotic Translation

Injury to sensory neurons causes an increase in the excitability of these cells leading to enhanced action potential generation and a lowering of spike threshold. This type of sensory neuron plasticity occurs across vertebrate and invertebrate species and has been linked to the development of both acute and persistent pain. Injury-induced plasticity in sensory neurons relies on localized changes in gene expression that occur at the level of mRNA translation. Many different translation regulation signalling events have been defined and these signalling events are thought to selectively target subsets of mRNAs. Recent evidence from mice suggests that the key signalling event for nociceptor plasticity is mitogen-activated protein kinase-interacting kinase (MNK) -mediated phosphorylation of eukaryotic translation initiation factor (eIF) 4E. To test the degree to which this is conserved in other species, we used a previously described sensory neuron plasticity model in Aplysia californica . We find, using a variety of pharmacological tools, that MNK signalling is crucial for axonal hyperexcitability in sensory neurons from Aplysia . We propose that MNK-eIF4E signalling is a core, evolutionarily conserved, signalling module that controls nociceptor plasticity. This finding has important implications for the therapeutic potential of this target, and it provides interesting clues about the evolutionary origins of mechanisms important for pain-related plasticity. This article is part of the Theo Murphy meeting issue ‘Evolution of mechanisms and behaviour important for pain’.

scholarly journals Essential Role of Enterovirus 2A Protease in Counteracting Stress Granule Formation and the Induction of Type I Interferon

2019 ◽  
Vol 93 (10) ◽  
Author(s):  
Linda J. Visser ◽  
Martijn A. Langereis ◽  
Huib H. Rabouw ◽  
Maryam Wahedi ◽  
Elke M. Muntjewerff ◽  
...  
Keyword(s):  
Gene Transcription ◽  
Cellular Responses ◽  
Encephalomyocarditis Virus ◽  
Stress Granule ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Type I ◽  
Granule Formation ◽  
Α Subunit ◽  
Viral Proteases

ABSTRACTMost viruses have acquired mechanisms to suppress antiviral alpha/beta interferon (IFN-α/β) and stress responses. Enteroviruses (EVs) actively counteract the induction of IFN-α/β gene transcription and stress granule (SG) formation, which are increasingly implicated as a platform for antiviral signaling, but the underlying mechanisms remain poorly understood. Both viral proteases (2Aproand 3Cpro) have been implicated in the suppression of these responses, but these conclusions predominantly rely on ectopic overexpression of viral proteases or addition of purified viral proteases to cell lysates. Here, we present a detailed and comprehensive comparison of the effect of individual enterovirus proteases on the formation of SGs and the induction of IFN-α/β gene expression in infected cells for representative members of the enterovirus species EV-A to EV-D. First, we show that SG formation and IFN-β induction are suppressed in cells infected with EV-A71, coxsackie B3 virus (CV-B3), CV-A21, and EV-D68. By introducing genes encoding CV-B3 proteases in a recombinant encephalomyocarditis virus (EMCV) that was designed to efficiently activate antiviral responses, we show that CV-B3 2Apro, but not 3Cpro, is the major antagonist that counters SG formation and IFN-β gene transcription and that 2Apro’s proteolytic activity is essential for both functions. 2Aproefficiently suppressed SG formation despite protein kinase R (PKR) activation and α subunit of eukaryotic translation initiation factor 2 phosphorylation, suggesting that 2Aproantagonizes SG assembly or promotes its disassembly. Finally, we show that the ability to suppress SG formation and IFN-β gene transcription is conserved in the 2Aproof EV-A71, CV-A21, and EV-D68. Collectively, our results indicate that enterovirus 2Aproplays a key role in inhibiting innate antiviral cellular responses.IMPORTANCEEnteroviruses are important pathogens that can cause a variety of diseases in humans, including aseptic meningitis, myocarditis, hand-foot-and-mouth disease, conjunctivitis, and acute flaccid paralysis. Like many other viruses, enteroviruses must counteract antiviral cellular responses to establish an infection. It has been suggested that enterovirus proteases cleave cellular factors to perturb antiviral pathways, but the exact contribution of viral proteases 2Aproand 3Cproremains elusive. Here, we show that 2Apro, but not 3Cpro, of all four human EV species (EV-A to EV-D) inhibits SG formation and IFN-β gene transcription. Our observations suggest that enterovirus 2Aprohas a conserved function in counteracting antiviral host responses and thereby is the main enterovirus “security protein.” Understanding the molecular mechanisms of enterovirus immune evasion strategies may help to develop countermeasures to control infections with these viruses.

scholarly journals HIV-1 Gag Blocks Selenite-Induced Stress Granule Assembly by Altering the mRNA Cap-Binding Complex

mBio ◽  
2016 ◽  
Vol 7 (2) ◽  
Author(s):  
Alessandro Cinti ◽  
Valerie Le Sage ◽  
Marwan Ghanem ◽  
Andrew J. Mouland
Keyword(s):  
Translation Initiation ◽  
Mrna Translation ◽  
Stress Granule ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Type Ii ◽  
Gag Protein ◽  
Induced Stress ◽  
Important Host ◽  
Hiv 1

ABSTRACT Stress granules (SGs) are dynamic accumulations of stalled preinitiation complexes and translational machinery that assemble under stressful conditions. Sodium selenite (Se) induces the assembly of noncanonical type II SGs that differ in morphology, composition, and mechanism of assembly from canonical SGs. Se inhibits translation initiation by altering the cap-binding activity of eukaryotic translation initiation factor 4E (eIF4E)-binding protein 1 (4EBP1). In this work, we show that human immunodeficiency virus type 1 (HIV-1) Gag is able to block the assembly of type II noncanonical SGs to facilitate continued Gag protein synthesis. We demonstrate that expression of Gag reduces the amount of hypophosphorylated 4EBP1 associated with the 5′ cap potentially through an interaction with its target, eIF4E. These results suggest that the assembly of SGs is an important host antiviral defense that HIV-1 has evolved for inhibition through several distinct mechanisms. IMPORTANCE The antiviral stress response is an important host defense that many viruses, including HIV-1, have evolved to evade. Selenite induces a block in translation and leads to stress granule assembly through the sequestration of eIF4E by binding hypophosphorylated 4EBP1. In this work, we demonstrate that in the face of selenite-induced stress, HIV-1 is able to maintain Gag mRNA translation and to elicit a blockade to selenite-induced stress granule assembly by altering the amount of hypophosphorylated 4EBP1 on the 5′ cap.

scholarly journals Novel N7-Arylmethyl Substituted Dinucleotide mRNA 5′ cap Analogs: Synthesis and Evaluation as Modulators of Translation

Pharmaceutics ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1941
Author(s):  
Radoslaw Wojcik ◽  
Marek R. Baranowski ◽  
Lukasz Markiewicz ◽  
Dorota Kubacka ◽  
Marcelina Bednarczyk ◽  
...  
Keyword(s):  
Messenger Rna ◽  
A549 Cells ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation ◽  
Potential Applications ◽  
Eukaryotic Translation Initiation ◽  
Translational Inhibition

Dinucleotide analogs of the messenger RNA cap (m7GpppN) are useful research tools and have potential applications as translational inhibitors or reagents for modification of in vitro transcribed mRNAs. It has been previously reported that replacing the methyl group at the N7-position with benzyl (Bn) produces a dinucleotide cap with superior properties. Here, we followed up on this finding by synthesizing 17 novel Bn7GpppG analogs and determining their structure–activity relationship regarding translation and translational inhibition. The compounds were prepared in two steps, including selective N7-alkylation of guanosine 5′-monophosphate by arylmethyl bromide followed by coupling with imidazole-activated GDP, with total yields varying from 22% to 62%. The compounds were then evaluated by determining their affinity for eukaryotic translation initiation factor 4E (eIF4E), testing their susceptibility to decapping pyrophosphatase, DcpS—which is most likely the major cellular enzyme targeting this type of compound—and determining their translation inhibitory properties in vitro. We also synthesized mRNAs capped with the evaluated compounds and tested their translational properties in A549 cells. Our studies identified N7-(4-halogenbenzyl) substituents as promising modifications in the contexts of either mRNA translation or translational inhibition. Finally, to gain more insight into the consequences at the molecular level of N7-benzylation of the mRNA cap, we determined the crystal structures of three compounds with eIF4E.

scholarly journals PRMT7 methylates eukaryotic translation initiation factor 2α and regulates its role in stress granule formation

2019 ◽  
Vol 30 (6) ◽  
pp. 778-793 ◽  
Author(s):  
Nasim Haghandish ◽  
R. Mitchell Baldwin ◽  
Alan Morettin ◽  
Haben Tesfu Dawit ◽  
Hemanta Adhikary ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Stress Granule ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Single Type ◽  
Granule Formation ◽  
Eukaryotic Translation Initiation Factor ◽  
Eukaryotic Translation ◽  
Arginine Residues ◽  
Eukaryotic Translation Initiation

Protein arginine methyltransferases (PRMTs) are a family of enzymes that modify proteins by methylating the guanidino nitrogen atoms of arginine residues to regulate cellular processes such as chromatin remodeling, pre-mRNA splicing, and signal transduction. PRMT7 is the single type III PRMT solely capable of arginine monomethylation. To date, other than histone proteins, there are very few identified substrates of PRMT7. We therefore performed quantitative mass spectrometry experiments to identify PRMT7’s interactome and potential substrates to better characterize the enzyme’s biological function(s) in cells. These experiments revealed that PRMT7 interacts with and can methylate eukaryotic translation initiation factor 2 alpha (eIF2α), in vitro and in breast cancer cells. Furthermore, we uncovered a potential regulatory interplay between eIF2α arginine methylation by PRMT7 and stress-induced phosphorylation status of eIF2α at serine 51. Finally, we demonstrated that PRMT7 is required for eIF2α-dependent stress granule formation in the face of various cellular stresses. Altogether, our findings implicate PRMT7 as a novel mediator of eIF2α-dependent cellular stress response pathways.

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