scholarly journals Modulation of RNA condensation by the DEAD-box protein eIF4A

2019 ◽  
Author(s):  
Devin Tauber ◽  
Gabriel Tauber ◽  
Anthony Khong ◽  
Briana Van Treeck ◽  
Jerry Pelletier ◽  
...  
Keyword(s):  
Stress Granules ◽  
Protein Aggregates ◽  
Stress Granule ◽  
List Type ◽  
Dependent Manner ◽  
Granule Formation ◽  
Dead Box ◽  
The Dead ◽  
In Cells

SUMMARYStress granules are condensates of non-translating mRNAs and proteins involved in the stress response and neurodegenerative diseases. Stress granules form in part through intermolecular RNA-RNA interactions, although the process of RNA condensation is poorly understood. In vitro, we demonstrate that RNA is effectively recruited to the surfaces of RNA or RNP condensates. We demonstrate that the DEAD-box protein eIF4A reduces RNA condensation in vitro and limits stress granule formation in cells. This defines a purpose for eIF4A to limit intermolecular RNA-RNA interactions in cells, thereby allowing for proper RNP function. These results establish an important role for DEAD-box proteins as ATP-dependent RNA chaperones that can limit the intermolecular condensation and entanglement of RNA, analogous to the function of proteins like HSP70 in combatting protein aggregates.eTOC BlurbStress granules are formed in part by the process of RNA condensation, which is mediated by and promotes trans RNA-RNA interactions. The essential DEAD-box protein and translation initiation factor eIF4A limits stress granule formation by reducing RNA condensation through its function as an ATP-dependent RNA binding protein, behaving analogously to how protein chaperones like HSP70 combat protein aggregates.HighlightsRNA condensates promote intermolecular RNA-RNA interactions at their surfaceseIF4A limits the recruitment of RNAs to stress granules in cellseIF4A reduces the nucleation of stress granules in cellsRecombinant eIF4A1 inhibits the condensation of RNA in vitro in an ATP-dependent manner

scholarly journals RNA self-assembly contributes to stress granule formation and defining the stress granule transcriptome

2018 ◽  
Vol 115 (11) ◽  
pp. 2734-2739 ◽  
Author(s):  
Briana Van Treeck ◽  
David S. W. Protter ◽  
Tyler Matheny ◽  
Anthony Khong ◽  
Christopher D. Link ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Self Assembly ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Stress Granules ◽  
Stress Granule ◽  
Local Concentration ◽  
Granule Formation ◽  
In Cells

Stress granules are higher order assemblies of nontranslating mRNAs and proteins that form when translation initiation is inhibited. Stress granules are thought to form by protein–protein interactions of RNA-binding proteins. We demonstrate RNA homopolymers or purified cellular RNA forms assemblies in vitro analogous to stress granules. Remarkably, under conditions representative of an intracellular stress response, the mRNAs enriched in assemblies from total yeast RNA largely recapitulate the stress granule transcriptome. We suggest stress granules are formed by a summation of protein–protein and RNA–RNA interactions, with RNA self-assembly likely to contribute to other RNP assemblies wherever there is a high local concentration of RNA. RNA assembly in vitro is also increased by GR and PR dipeptide repeats, which are known to increase stress granule formation in cells. Since GR and PR dipeptides are involved in neurodegenerative diseases, this suggests that perturbations increasing RNA–RNA assembly in cells could lead to disease.

scholarly journals 0028 Sleep Duration Influences the Kinetics of Stress Granule Formation

SLEEP ◽  
2020 ◽  
Vol 43 (Supplement_1) ◽  
pp. A11-A12
Author(s):  
M K Dougherty ◽  
C Saul ◽  
L Carman ◽  
M D Nelson ◽  
J C Tudor
Keyword(s):  
Sleep Deprivation ◽  
Sleep Duration ◽  
Protein A ◽  
Stress Granules ◽  
Mtor Pathway ◽  
Stress Granule ◽  
Target Of Rapamycin ◽  
Granule Formation ◽  
One Way Anova

Abstract Introduction Stress granules are non-membrane bound aggregates of messenger ribonucleoproteins that are biomarkers of cellular stress. It has been shown in cells in vitro that suppression of the mammalian target of rapamycin (mTOR) pathway and its non-mammalian orthologue target of rapamycin (TOR) is associated with an increase in stress granule formation. It has also been shown that the mTOR pathway is suppressed in response to sleep deprivation in mice. Despite the possible connection via the TOR/mTOR pathway, there has not been any previous evidence linking sleep deprivation with stress granule formation. Methods Our present investigation uses the nematode Caenorhabditis elegans to model how stress granule formation and clearance are modified by sleep duration. We developed novel strains of C. elegans that model each type of sleep deprivation or enhancement and have RFP-labeled PAB-1 protein, a key component of stress granules. In addition to modifying sleep duration via genetic means, we also sleep deprived wildtype fluorescently labeled animals using mechanical disturbances. Results Animals with enhanced stress-induced sleep have stress granules that are smaller in size and cleared faster than wildtype, while sleep deprived animals have granules that are slower to clear (F11,473 = 7.752, ***p < 0.0001, one-way ANOVA). Animals that were manually deprived of stress-induced sleep were similarly slower to clear stress granules (F5,209 = 5.476 ***p < 0.0001, one-way ANOVA). Interestingly, animals genetically deprived of developmentally-timed sleep does not appear to have more stress granules in the middle of their sleep period than the sleeping wildtype stage (F2,42 = 2.659, p = 0.0729, one-way ANOVA). Conclusion This work demonstrates that the amount of sleep affects stress granule kinetics, which impacts the flow of genetic information inside cells. Support This work was supported by an R15GM122058 (NIH), John P. McNulty scholars program (SJU) and summer scholars program (SJU).

scholarly journals Casein Kinase 2 Is Linked to Stress Granule Dynamics through Phosphorylation of the Stress Granule Nucleating Protein G3BP1

2016 ◽  
Vol 37 (4) ◽  
Author(s):  
Lucas C. Reineke ◽  
Wei-Chih Tsai ◽  
Antrix Jain ◽  
Jason T. Kaelber ◽  
Sung Yun Jung ◽  
...  
Keyword(s):  
Cell Fate ◽  
Stress Granules ◽  
Casein Kinase ◽  
Casein Kinase 2 ◽  
Stress Granule ◽  
Translational Repression ◽  
Transcriptional Responses ◽  
Granule Formation ◽  
Cell Fate Decisions

ABSTRACT Stress granules (SGs) are large macromolecular aggregates that contain translation initiation complexes and mRNAs. Stress granule formation coincides with translational repression, and stress granules actively signal to mediate cell fate decisions by signaling to the translation apparatus to (i) maintain translational repression, (ii) mount various transcriptional responses, including innate immunity, and (iii) repress apoptosis. Previous work showed that G3BP1 is phosphorylated at serine 149, which regulates G3BP1 oligomerization, stress granule assembly, and RNase activity intrinsic to G3BP1. However, the kinase that phosphorylates G3BP1 was not identified, leaving a key step in stress granule regulation uncharacterized. Here, using chemical inhibition, genetic depletion, and overexpression experiments, we show that casein kinase 2 (CK2) promotes stress granule dynamics. These results link CK2 activity with SG disassembly. We also show that casein kinase 2 phosphorylates G3BP1 at serine 149 in vitro and in cells. These data support a role for casein kinase 2 in regulation of protein synthesis by downregulating stress granule formation through G3BP1.

184 Two types of anti-TIGIT antibodies with distinct binding epitope and functional activities

2020 ◽  
Vol 8 (Suppl 3) ◽  
pp. A198-A198
Author(s):  
Tingting Zhong ◽  
Xinghua Pang ◽  
Zhaoliang Huang ◽  
Na Chen ◽  
Xiaoping Jin ◽  
...  
Keyword(s):  
T Cells ◽  
Mixed Culture ◽  
Cell Activity ◽  
Cross Reactivity ◽  
Binding Activity ◽  
Jurkat Cells ◽  
List Type ◽  
Dependent Manner ◽  
Vitro Assay

BackgroundTIGIT is an inhibitory receptor mainly expressed on natural killer (NK) cells, CD8+ T cells, CD4+ T cells and Treg cells. TIGIT competes with CD226 for binding with CD155. In cancers, CD155 has been reported to up-regulate on tumor cells, and TIGIT was found to increase on TILs.1 Activation of TIGIT/CD155 pathway would mediate immunosuppression in tumor; while blockade of TIGIT promotes anti-tumor immune response.MethodsAK126 and AK113 are two humanized anti-human TIGIT monoclonal antibodies developed by Akesobio. Binding activity of AK126 and AK113 to human TIGIT, and competitive binding activity with CD155 and CD112, were performed by using ELISA, Fortebio, and FACS assays. Cross-reactivity with cynomolgus monkey TIGIT and epitope binning were also tested by ELISA assay. In-vitro assay to investigate the activity to promote IL-2 secretion was performed in mixed-culture of Jurkat-TIGIT cells and THP-1 cells.ResultsAK126 and AK113 could specifically bind to human TIGIT with comparative affinity and effectively blocked the binding of human CD155 and CD112 to human TIGIT. X-ray crystal structure of TIGIT and PVR revealed the C’-C’’ loop and FG loop regions of TIGIT are the main PVR interaction regions.2 The only amino acid residue differences in these regions between human and monkey TIGIT are 70C and 73D. AK126 binds to both human and monkey TIGIT, AK113 binds only to monkey TIGIT. This suggests that these residues are required for AK113 binding to human TIGIT, but not required for AK126. Interestingly, results from cell-based assays indicated that AK126 and AK113 showed significantly different activity to induce IL-2 secretion in mixed-culture of Jurkat-TIGIT cells and THP-1 cells (figure 1A and B), in which AK126 had a comparable capacity of activity to 22G2, a leading TIGIT mAb developed by another company, to induce IL-2 secretion, while, AK113 showed a significantly higher capacity than 22G2 and AK126.Abstract 184 Figure 1Anti-TIGIT Antibodies Rescues IL-2 Production in Vitro T-Cell Activity Assay in a dose dependent manner. Jurkat-TIGIT cells (Jurkat cells engineered to over-express human TIGIT) were co-cultured with THP-1 cells, and stimulated with plate-bound anti-CD3 mAb in the presence of TIGIT ligand CD155 (A) or CD112 (B) with anti-TIGIT antibodies. After incubated for 48h at 37° C and 5.0% CO2, IL-2 levels were assessed in culture supernatants by ELISA. Data shown as mean with SEM for n = 2.ConclusionsWe discovered two distinct types of TIGIT antibodies with differences in both epitope binding and functional activity. The mechanism of action and clinical significance of these antibodies require further investigation.ReferencesSolomon BL, Garrido-Laguna I. TIGIT: a novel immunotherapy target moving from bench to bedside. Cancer Immunol Immunother 2018;67:1659–1667.Stengel KF, Harden-Bowles K, Yu X, et al. Structure of TIGIT immunoreceptor bound to poliovirus receptor reveals a cell-cell adhesion and signaling mechanism that requires cis-trans receptor clustering. Proc Natl Acad Sci USA 2012;109:5399–5404.

scholarly journals Role of leukemia inhibitor factor (LIF) in decidualisation of murine uterine stromal cells in vitro

2004 ◽  
Vol 181 (3) ◽  
pp. 477-492 ◽  
Author(s):  
AA Fouladi Nashta ◽  
CV Andreu ◽  
N Nijjar ◽  
JK Heath ◽  
SJ Kimber
Keyword(s):  
In Vitro Culture ◽  
Stromal Cells ◽  
Control Level ◽  
Calf Serum ◽  
Prostaglandin E ◽  
Dependent Manner ◽  
Alp Activity ◽  
Dose Dependent ◽  
In Cells

Decidualisation of uterine stromal cells is a prerequisite for implantation of the embryo in mice. Here we have used an in vitro culture system in which stromal cells decidualise as indicated by a number of markers, including an increase in alkaline phosphatase (ALP) activity. The latter was used as a quantitative marker of decidualisation in the presence of low (2%) fetal calf serum. Prostaglandin E(2) (PGE(2)), which is known to induce decidualisation, increased ALP activity, and this effect was blocked in a dose-dependent manner by indomethacin. Leukemia inhibitory factor (LIF) was then examined, but it had no effect on PGE(2) secretion. However, LIF suppressed ALP activity in a dose-dependent manner in the presence of 2% serum, while an inhibitor of LIF that competes for binding to its receptor reversed the effect of LIF and increased ALP activity above the control level. In serum-free cultures, stromal cells differentiated rapidly, and no differences were observed between LIF-treated and untreated cultures. Stromal cells produce LIF during in vitro culture, and this peaked at 48 h. Freshly collected stromal cells from both day-2 and -4 pregnant mice expressed mRNA for the LIF receptor, and the transcript level was higher in cells isolated on day 4. However, no differences were observed in the relative levels of transcripts in cells from day 2 and day 4 after culture, nor were there differences between the LIF-treated cultures and controls. Therefore, in this study, we have shown that LIF suppresses decidualisation of murine uterine stromal cells in the presence of serum, this is not due to the regulation of PGE(2) secretion by stromal cells.

scholarly journals G-quadruplex DNA inhibits unwinding activity but promotes liquid–liquid phase separation by the DEAD-box helicase Ded1p

2021 ◽  
Author(s):  
Jun Gao ◽  
Zhaofeng Gao ◽  
Andrea A. Putnam ◽  
Alicia K. Byrd ◽  
Sarah L. Venus ◽  
...  
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Liquid Phase Separation ◽  
Intrinsically Disordered ◽  
Dead Box ◽  
G4 Dna ◽  
G Quadruplex ◽  
The Dead ◽  
Liquid Liquid Phase Separation

G-quadruplex (G4) DNA inhibits RNA unwinding activity but promotes liquid–liquid phase separation of the DEAD-box helicase Ded1p in vitro and in cells. This highlights multifaceted effects of G4DNA on an enzyme with intrinsically disordered domains.

scholarly journals Puumala and Andes Orthohantaviruses Cause Transient Protein Kinase R-Dependent Formation of Stress Granules

2019 ◽  
Vol 94 (3) ◽  
Author(s):  
Wanda Christ ◽  
Janne Tynell ◽  
Jonas Klingström
Keyword(s):  
Protein Kinase ◽  
Host Cell ◽  
Stress Responses ◽  
Stress Granules ◽  
Cell Stress ◽  
Stress Granule ◽  
Hantavirus Infection ◽  
Stress Signaling ◽  
Protein Kinase R ◽  
Granule Formation

ABSTRACT Virus infection frequently triggers host cell stress signaling resulting in translational arrest; as a consequence, many viruses employ means to modulate the host stress response. Hantaviruses are negative-sense, single-stranded RNA viruses known to inhibit host innate immune responses and apoptosis, but their impact on host cell stress signaling remains largely unknown. In this study, we investigated activation of host cell stress responses during hantavirus infection. We show that hantavirus infection causes transient formation of stress granules (SGs) but does so in only a limited proportion of infected cells. Our data indicate some cell type-specific and hantavirus species-specific variability in SG prevalence and show SG formation to be dependent on the activation of protein kinase R (PKR). Hantavirus infection inhibited PKR-dependent SG formation, which could account for the transient nature and low prevalence of SG formation observed during hantavirus infection. In addition, we report only limited colocalization of hantaviral proteins or RNA with SGs and show evidence indicating hantavirus-mediated inhibition of PKR-like endoplasmic reticulum (ER) kinase (PERK). IMPORTANCE Our work presents the first report on stress granule formation during hantavirus infection. We show that hantavirus infection actively inhibits stress granule formation, thereby escaping the detrimental effects on global translation imposed by host stress signaling. Our results highlight a previously uncharacterized aspect of hantavirus-host interactions with possible implications for how hantaviruses are able to cause persistent infection in natural hosts and for pathogenesis.

scholarly journals Small molecules for modulating protein driven liquid-liquid phase separation in treating neurodegenerative disease

2019 ◽  
Author(s):  
Richard J. Wheeler ◽  
Hyun O. Lee ◽  
Ina Poser ◽  
Arun Pal ◽  
Thom Doeleman ◽  
...  
Keyword(s):  
Phase Separation ◽  
Neurodegenerative Disease ◽  
Stress Granules ◽  
Life Time ◽  
Stress Granule ◽  
Phase Behaviour ◽  
Granule Proteins ◽  
Lateral Sclerosis ◽  
Liquid Liquid Phase Separation

AbstractAmyotrophic lateral sclerosis (ALS) is a neurodegenerative disease with few avenues for treatment. Many proteins implicated in ALS associate with stress granules, which are examples of liquid-like compartments formed by phase separation. Aberrant phase transition of stress granules has been implicated in disease, suggesting that modulation of phase transitions could be a possible therapeutic route. Here, we combine cell-based and protein-based screens to show that lipoamide, and its related compound lipoic acid, reduce the propensity of stress granule proteins to aggregate in vitro. More significantly, they also prevented aggregation of proteins over the life time of Caenorhabditis elegans. Observations that they prevent dieback of ALS patient-derived (FUS mutant) motor neuron axons in culture and recover motor defects in Drosophila melanogaster expressing FUS mutants suggest plausibility as effective therapeutics. Our results suggest that altering phase behaviour of stress granule proteins in the cytoplasm could be a novel route to treat ALS.

scholarly journals Retinoic Acid Inducible Gene I and Protein Kinase R, but Not Stress Granules, Mediate the Proinflammatory Response to Yellow Fever Virus

2020 ◽  
Vol 94 (22) ◽  
Author(s):  
Guillaume Beauclair ◽  
Felix Streicher ◽  
Maxime Chazal ◽  
Daniela Bruni ◽  
Sarah Lesage ◽  
...  
Keyword(s):  
Yellow Fever ◽  
Yellow Fever Virus ◽  
Rna Virus ◽  
Stress Granules ◽  
Cytokine Response ◽  
Fever Virus ◽  
Stress Granule ◽  
Proinflammatory Response ◽  
Granule Formation ◽  
Proinflammatory Mediators

ABSTRACT Yellow fever virus (YFV) is an RNA virus primarily targeting the liver. Severe YF cases are responsible for hemorrhagic fever, plausibly precipitated by excessive proinflammatory cytokine response. Pathogen recognition receptors (PRRs), such as the cytoplasmic retinoic acid inducible gene I (RIG-I)-like receptors (RLRs), and the viral RNA sensor protein kinase R (PKR), are known to initiate a proinflammatory response upon recognition of viral genomes. Here, we sought to reveal the main determinants responsible for the acute cytokine expression occurring in human hepatocytes following YFV infection. Using a RIG-I-defective human hepatoma cell line, we found that RIG-I largely contributes to cytokine secretion upon YFV infection. In infected RIG-I-proficient hepatoma cells, RIG-I was localized in stress granules. These granules are large aggregates of stalled translation preinitiation complexes known to concentrate RLRs and PKR and are so far recognized as hubs orchestrating RNA virus sensing. Stable knockdown of PKR in hepatoma cells revealed that PKR contributes to both stress granule formation and cytokine induction upon YFV infection. However, stress granule disruption did not affect the cytokine response to YFV infection, as assessed by small interfering RNA (siRNA)-knockdown-mediated inhibition of stress granule assembly. Finally, no viral RNA was detected in stress granules using a fluorescence in situ hybridization approach coupled with immunofluorescence. Our findings suggest that both RIG-I and PKR mediate proinflammatory cytokine induction in YFV-infected hepatocytes, in a stress granule-independent manner. Therefore, by showing the uncoupling of the cytokine response from the stress granule formation, our model challenges the current view in which stress granules are required for the mounting of the acute antiviral response. IMPORTANCE Yellow fever is a mosquito-borne acute hemorrhagic disease caused by yellow fever virus (YFV). The mechanisms responsible for its pathogenesis remain largely unknown, although increased inflammation has been linked to worsened outcome. YFV targets the liver, where it primarily infects hepatocytes. We found that two RNA-sensing proteins, RIG-I and PKR, participate in the induction of proinflammatory mediators in human hepatocytes infected with YFV. We show that YFV infection promotes the formation of cytoplasmic structures, termed stress granules, in a PKR- but not RIG-I-dependent manner. While stress granules were previously postulated to be essential platforms for immune activation, we found that they are not required for the production of proinflammatory mediators upon YFV infection. Collectively, our work uncovered molecular events triggered by the replication of YFV, which could prove instrumental in clarifying the pathogenesis of the disease, with possible repercussions for disease management.

scholarly journals Stable Formation of Compositionally Unique Stress Granules in Virus-Infected Cells

2009 ◽  
Vol 84 (7) ◽  
pp. 3654-3665 ◽  
Author(s):  
Joanna Piotrowska ◽  
Spencer J. Hansen ◽  
Nogi Park ◽  
Katarzyna Jamka ◽  
Peter Sarnow ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Heat Shock ◽  
Viral Infections ◽  
De Novo ◽  
Stress Granules ◽  
Stress Granule ◽  
Initiation Factor ◽  
Granule Formation ◽  
Infected Cells ◽  
Positive Strand Rna

ABSTRACT Stress granules are sites of mRNA storage formed in response to a variety of stresses, including viral infections. Here, the mechanisms and consequences of stress granule formation during poliovirus infection were examined. The results indicate that stress granules containing T-cell-restricted intracellular antigen 1 (TIA-1) and mRNA are stably constituted in infected cells despite lacking intact RasGAP SH3-domain binding protein 1 (G3BP) and eukaryotic initiation factor 4G. Fluorescent in situ hybridization revealed that stress granules in infected cells do not contain significant amounts of viral positive-strand RNA. Infection does not prevent stress granule formation in response to heat shock, indicating that poliovirus does not block de novo stress granule formation. A mutant TIA-1 protein that prevents stress granule formation during oxidative stress also prevents formation in infected cells. However, stress granule formation during infection is more dependent upon ongoing transcription than is formation during oxidative stress or heat shock. Furthermore, Sam68 is recruited to stress granules in infected cells but not to stress granules formed in response to oxidative stress or heat shock. These results demonstrate that stress granule formation in poliovirus-infected cells utilizes a transcription-dependent pathway that results in the appearance of stable, compositionally unique stress granules.

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