Stress granules: potential therapeutic targets for infectious and inflammatory diseases

Stress granules: Guardians of cellular health and triggers of disease

Stress granules are membraneless organelles that serve as a protective cellular response to external stressors by sequestering non-translating messenger RNAs (mRNAs) and regulating protein synthesis. Stress granules formation mechanism is conserved across species, from yeast to mammals, and they play a critical role in minimizing cellular damage during stress. Composed of heterogeneous ribonucleoprotein complexes, stress granules are enriched not only in mRNAs but also in noncoding RNAs and various proteins, including translation initiation factors and RNA-binding proteins. Genetic mutations affecting stress granule assembly and disassembly can lead to abnormal stress granule accumulation, contributing to the progression of several diseases. Recent research indicates that stress granule dynamics are pivotal in determining their physiological and pathological functions, with acute stress granule formation offering protection and chronic stress granule accumulation being detrimental. This review focuses on the multifaceted roles of stress granules under diverse physiological conditions, such as regulation of mRNA transport, mRNA translation, apoptosis, germ cell development, phase separation processes that govern stress granule formation, and their emerging implications in pathophysiological scenarios, such as viral infections, cancer, neurodevelopmental disorders, neurodegeneration, and neuronal trauma.

A Narrative Review on Stress Granules and Ultraviolet Stress Granules

Background: Stress granules (SGs) are membraneless structures formed through liquid-liquid phase separation in response to cellular stress. These dynamic assemblies play a pivotal role in cellular adaptation and recovery from external stressors by modulating protein synthesis and preserving mRNA integrity, thereby influencing various cellular biological processes. Their significance has been demonstrated in diverse phenomena, including tumorigenesis, drug resistance, cellular senescence, and neurodegenerative disorders. Objective: This narrative review focuses on SGs and ultraviolet-induced SGs (UV SGs), examining their composition, formation mechanisms, and potential functions in the pathogenesis of various dermatological conditions, and explores the implications of UV SGs in cutaneous inflammation, immune-mediated skin disorders, dermatological malignancies, and pigmentary abnormalities. Methods: We conducted a literature search of relevant publications from the inception of the Web of Science and CNKI databases up to 2024. The search terms included "Stress Granules," "Ultraviolet Stress Granules," "Phase Separation," "Cellular Stress Response," and "Skin Diseases." High-quality articles were included after rigorous screening. Conclusions: In conclusion, this review aims to provide novel perspectives and targeted strategies for both clinical management and fundamental biological research in the field of dermatology.

Compartmentation of multiple metabolic enzymes and their preparation in vitro and in cellulo

Compartmentalization of multiple enzymes in cellulo and in vitro is a means of controlling the cascade reaction of metabolic enzymes. The compartmentation of enzymes through liquid-liquid phase separation may facilitate the reversible control of biocatalytic cascade reactions, thereby reducing the transcriptional and translational burden. This has attracted attention as a potential application in bioproduction. Recent research has demonstrated the existence and regulatory mechanisms of various enzyme compartments within cells. Mounting evidence suggests that enzyme compartmentation allows in vitro and in vivo regulation of cellular metabolism. However, the comprehensive regulatory mechanisms of enzyme condensates in cells and ideal organization of cellular systems remain unknown. This review provides an overview of the recent progress in multiple enzyme compartmentation in cells and summarizes strategies to reconstruct multiple enzyme assemblies in vitro and in cellulo. By examining parallel examples, we have evaluated the consensus and future perspectives of enzyme condensation.

Connecting the Dots: Stress Granule and Cardiovascular Diseases

Stress granules (SGs) are membrane-less cytoplasmic assemblies composed of mRNAs and RNA-binding proteins (RBPs) that transiently form to cope with various cellular stressors by halting mRNA translation and, consequently, protein synthesis. SG formation plays a crucial role in regulating multiple cellular processes, including cellular senescence, inflammatory responses, and adaptation to oxidative stress under both physiological and pathological conditions. Dysregulation of SG assembly and disassembly has been implicated in the pathogenesis of various diseases, including cardiovascular diseases (CVDs), cancer, viral and bacterial infections, and degenerative diseases. In this review, we survey the key aspects of SGs biogenesis and biological functions, with a particular focus on their causal involvement in CVDs. Furthermore, we summarized several SG-modulating compounds and discussed the therapeutic potential of small molecules targeting SG-related diseases in clinical settings.

Transcriptome Analysis Reveals Sertoli Cells Adapting Through Redox and Metabolic Pathways Under Heat Stress in Goats

BACKGROUND/OBJECTIVES

Climate change-induced temperature elevations pose significant challenges to livestock reproduction, particularly affecting testicular function in small ruminants. This study investigates the acute heat-stress response in goat Sertoli cells (SCs), aiming to elucidate the molecular mechanisms underlying heat-induced damage to male reproductive tissues.

METHODS

SCs were isolated from testes of 4-month-old black goats and exposed to heat stress (44 °C for 2.5 h). We employed transcriptome sequencing, CCK-8 assay, electron microscopy, ROS measurement, autophagy detection, Western blot analysis, and lactate concentration measurement. Bioinformatics analyses including Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, and protein-protein interaction network analyses were performed on the transcriptome data.

RESULTS

Heat stress significantly reduced SC viability, induced oxidative stress and autophagy, and altered gene expression profiles. We identified 1231 significantly differentially expressed genes, with significant enrichment in membrane-related processes and metabolic pathways. Metabolism-related genes, including PKLR, ACOT11, and LPCT12, were significantly downregulated. Protein-protein interaction network analysis revealed ten hub genes potentially crucial in the heat-stress response: HSP90AA1, HSPA5, BAG3, IGF1, HSPH1, IL1A, CCL2, CXCL10, ALB, and CALML4.

CONCLUSIONS

This study provides comprehensive insights into the molecular mechanisms underlying goat SC response to heat stress. The identified genes and pathways, particularly those related to metabolism and stress response, offer potential targets for developing strategies to mitigate heat-stress effects on livestock reproduction. These findings contribute to our understanding of climate change impacts on animal husbandry and may inform the development of heat-stress resistant livestock lines.

The Nucleocapsid (N) Proteins of Different Human Coronaviruses Demonstrate a Variable Capacity to Induce the Formation of Cytoplasmic Condensates

To date, seven human coronaviruses (HCoVs) have been identified. Four of these viruses typically manifest as a mild respiratory disease, whereas the remaining three can cause severe conditions that often result in death. The reasons for these differences remain poorly understood, but they may be related to the properties of individual viral proteins. The nucleocapsid (N) protein plays a crucial role in the packaging of viral genomic RNA and the modification of host cells during infection, in part due to its capacity to form dynamic biological condensates via liquid-liquid phase separation (LLPS). In this study, we investigated the capacity of N proteins derived from all HCoVs to form condensates when transiently expressed in cultured human cells. Some of the transfected cells were observed to contain cytoplasmic granules in which most of the N proteins were accumulated. Notably, the N proteins of SARS-CoV and SARS-CoV-2 showed a significantly reduced tendency to form cytoplasmic condensates. The condensate formation was not a consequence of overexpression of N proteins, as is typical for LLPS-inducing proteins. These condensates contained components of stress granules (SGs), indicating that the expression of N proteins caused the formation of SGs, which integrate N proteins. Thus, the N proteins of two closely related viruses, SARS-CoV and SARS-CoV-2, have the capacity to antagonize SG induction and/or assembly, in contrast to all other known HCoVs.

Stress Granules in Infectious Disease: Cellular Principles and Dynamic Roles in Immunity and Organelles

Stress granules (SGs) are membrane-less aggregates that form in response to various cellular stimuli through a process called liquid-liquid phase separation (LLPS). Stimuli such as heat shock, osmotic stress, oxidative stress, and infections can induce the formation of SGs, which play crucial roles in regulating gene expression to help cells adapt to stress conditions. Various mRNAs and proteins are aggregated into SGs, particularly those associated with the protein translation machinery, which are frequently found in SGs. When induced by infections, SGs modulate immune cell activity, supporting the cellular response against infection. The roles of SGs differ in viral versus microbial infections, and depending on the type of immune cell involved, SGs function differently in response to infection. In this review, we summarize our current understanding of the implication of SGs in immunity and cellular organelles in the context of infectious diseases. Importantly, we explore insights into the regulatory functions of SGs in the context of host cells under infection.

RSK1 and RSK2 as therapeutic targets: an up-to-date snapshot of emerging data

INTRODUCTION

The four members of the p90 ribosomal S6 kinase (RSK) family are serine/threonine protein kinases, which are phosphorylated and activated by ERK1/2. RSK1/2/3 are further phosphorylated by PDK1. Receiving inputs from two major signaling pathways places RSK as a key signaling node in numerous pathologies. A plethora of RSK1/2 substrates have been identified, and in the majority of cases the causative roles these RSK substrates play in the pathology are unknown.

AREAS COVERED

The majority of studies have focused on RSK1/2 and their functions in a diverse group of cancers. However, RSK1/2 are known to have important functions in cardiovascular disease and neurobiological disorders. Based on the literature, we identified substrates that are common in these pathologies with the goal of identifying fundamental physiological responses to RSK1/2.

EXPERT OPINION

The core group of targets in pathologies driven by RSK1/2 are associated with the immune response. However, there is a paucity of the literature addressing RSK function in inflammation, which is critical to know as the pan RSK inhibitor, PMD-026, is entering phase II clinical trials for metastatic breast cancer. A RSK inhibitor has the potential to be used in numerous diverse diseases and disorders.

Chronic stress antagonizes formation of Stress Granules

Chronic stress mediates cellular changes that can contribute to human disease. However, fluctuations in RNA metabolism caused by chronic stress have been largely neglected in the field. Stress granules (SGs) are cytoplasmic ribonucleoprotein condensates formed in response to stress-induced inhibition of mRNA translation and polysome disassembly. Despite the broad interest in SG assembly and disassembly in response to acute stress, SG assembly in response to chronic stress has not been extensively investigated. In this study, we show that cells pre-conditioned with low dose chronic (24-hour exposure) stresses such as oxidative stress, endoplasmic reticulum stress, mitochondrial stress, and starvation, fail to assemble SGs in response to acute stress. While translation is drastically decreased by acute stress in pre-conditioned cells, polysome profiling analysis reveals the partial preservation of polysomes resistant to puromycin-induced disassembly. We showed that chronic stress slows down the rate of mRNA translation at the elongation phase and triggers phosphorylation of translation elongation factor eEF2. Polysome profiling followed by RNase treatment confirmed that chronic stress induces ribosome stalling. Chronic stress-induced ribosome stalling is distinct from ribosome collisions that are known to trigger a specific stress response pathway. In summary, chronic stress triggers ribosome stalling, which blocks polysome disassembly and SG formation by subsequent acute stress.

Significant statements

Stress granules (SGs) are dynamic cytoplasmic biocondensates assembled in response to stress-induced inhibition of mRNA translation and polysome disassembly. SGs have been proposed to contribute to the survival of cells exposed to toxic conditions. Although the mechanisms of SG assembly and disassembly in the acute stress response are well understood, the role of SGs in modulating the response to chronic stress is unclear. Here, we show that human cells pre-conditioned with chronic stress fail to assemble SGs in response to acute stress despite inhibition of mRNA translation. Mechanistically, chronic stress induces ribosome stalling, which prevents polysome disassembly and subsequent SG formation. This finding suggests that chronically stressed or diseased human cells may have a dysfunctional SG response that could inhibit cell survival and promote disease.

Metal-polyphenol-network coated R612F nanoparticles reduce drug resistance in hepatocellular carcinoma by inhibiting stress granules

Stress granules (SGs) are considered to be the nonmembrane discrete assemblies present in the cytoplasm to cope with various environmental stress. SGs can promote the progression and drug resistance of hepatocellular carcinoma (HCC). Therefore, it is important to explore the mechanism of SG formation to reduce drug resistance in HCC. In this study, we demonstrate that p110α is required for SGs assembly. Mechanistically, the Arg-Gly (RG) motif of p110α is required for SG competence and regulates the recruitment of SG components. The methylation of p110α mediated by protein arginine methyltransferase 1 (PRMT1) interferes with the recruitment of p110α to SG components, thereby inhibiting the promotion of p110α to SGs. On this basis, we generated metal-polyphenol-network-coated R612F nanoparticles (MPN-R612F), which can efficiently enter HCC cells and maintain the hypermethylation state of p110α, thereby inhibiting the assembly of SGs and ultimately reducing the resistance of HCC cells to sorafenib. The combination of MPN-R612F nanoparticles and sorafenib can kill HCC cells more effectively and play a stronger anti-tumor effect. This study provides a new perspective for targeting SGs in the treatment of HCC.

Formation of the NLRP3 inflammasome inhibits stress granule assembly by multiple mechanisms

Proper regulation of cellular response to environmental stress is crucial for maintaining biological homeostasis and is achieved by the balance between cell death processes, such as the formation of the pyroptosis-inducing NLRP3 inflammasome, and pro-survival processes, such as stress granule (SG) assembly. However, the functional interplay between these two stress-responsive organelles remains elusive. Here, we identified DHX33, a viral RNA sensor for the NLRP3 inflammasome, as a SG component, and the SG-nucleating protein G3BP as an NLRP3 inflammasome component. We also found that a decrease in intracellular potassium (K+) concentration, a key 'common' step in NLRP3 inflammasome activation, markedly inhibited SG assembly. Therefore, when macrophages are exposed to stress stimuli with the potential to induce both SGs and the NLRP3 inflammasome, such as cytoplasmic poly(I:C) stimulation, they preferentially form the NLRP3 inflammasome but avoid SG assembly by sequestering G3BP into the inflammasome and by inducing a reduction in intracellular K+ levels. Thus, under such conditions, DHX33 is primarily utilized as a viral RNA sensor for the inflammasome. Our data reveal the functional crosstalk between NLRP3 inflammasome-mediated pyroptosis and SG-mediated cell survival pathways and delineate a molecular mechanism that regulates cell-fate decisions and anti-viral innate immunity under stress.

Fragile X Messenger Ribonucleoprotein Protein and Its Multifunctionality: From Cytosol to Nucleolus and Back

Silencing of the fragile X messenger ribonucleoprotein 1 (FMR1) gene and a consequent lack of FMR protein (FMRP) synthesis are associated with fragile X syndrome, one of the most common inherited intellectual disabilities. FMRP is a multifunctional protein that is involved in many cellular functions in almost all subcellular compartments under both normal and cellular stress conditions in neuronal and non-neuronal cell types. This is achieved through its trafficking signals, nuclear localization signal (NLS), nuclear export signal (NES), and nucleolar localization signal (NoLS), as well as its RNA and protein binding domains, and it is modulated by various post-translational modifications such as phosphorylation, ubiquitination, sumoylation, and methylation. This review summarizes the recent advances in understanding the interaction networks of FMRP with a special focus on FMRP stress-related functions, including stress granule formation, mitochondrion and endoplasmic reticulum plasticity, ribosome biogenesis, cell cycle control, and DNA damage response.

Evaluation of G3BP1 in the prognosis of acute and acute-on-chronic liver failure after the treatment of artificial liver support system

BACKGROUND

The increased expression of G3BP1 was positively correlated with the prognosis of liver failure.

AIM

To investigate the effect of G3BP1 on the prognosis of acute liver failure (ALF) and acute-on-chronic liver failure (ACLF) after the treatment of artificial liver support system (ALSS).

METHODS

A total of 244 patients with ALF and ACLF were enrolled in this study. The levels of G3BP1 on admission and at discharge were detected. The validation set of 514 patients was collected to verify the predicted effect of G3BP1 and the viability of prognosis.

RESULTS

This study was shown that lactate dehydrogenase (LDH), alpha-fetoprotein (AFP) and prothrombin time were closely related to the prognosis of patients. After the ALSS treatment, the patient' amount of decreased G3BP1 index in difference of G3BP1 between the value of discharge and admission (difG3BP1) < 0 group had a nearly 10-fold increased risk of progression compared with the amount of increased G3BP1 index. The subgroup analysis showed that the difG3BP1 < 0 group had a higher risk of progression, regardless of model for end-stage liver disease high-risk or low-risk group. At the same time, compared with the inflammatory marks [tumor necrosis factor-α, interleukin (IL)-1β and IL-18], G3BP1 had higher discrimination and was more stable in the model analysis and validation set. When combined with AFP and LDH, concordance index was respectively 0.84 and 0.8 in training and validation cohorts.

CONCLUSION

This study indicated that G3BP1 could predict the prognosis of ALF or ACLF patients treated with ALSS. The combination of G3BP1, AFP and LDH could accurately evaluate the disease condition and predict the clinical endpoint of patients.

Inhibition of cGAS-STING pathway by stress granules after activation of M2 macrophages by human mesenchymal stem cells against drug induced liver injury

OBJECTIVE

Cells can produce stress granules (SGs) to protect itself from damage under stress. The cGAS-STING pathway is one of the important pattern recognition pathways in the natural immune system. This study was investigated whether human mesenchymal stem cells (hMSCs) could protect the liver by inducing M2 macrophages to produce SGs during acute drug induced liver injury (DILI) induced by acetaminophen (APAP).

METHODS

After intragastric administration of APAP in vivo to induce DILI mice model, hMSCs were injected into the tail vein. The co-culture system of hMSCs and M2 macrophages was established in vitro. It was further use SGs inhibitor anisomicin to intervene M2 macrophages. The liver histopathology, liver function, reactive oxygen species (ROS) level, apoptosis pathway, endoplasmic reticulum stress (ERS) level, SGs markers (G3BP1/TIA-1), cGAS-STING pathway, TNF-α, IL-6, IL-1β mRNA levels in liver tissue and M2 macrophages were observed.

RESULTS

In vivo experiments, it showed that hMSCs could alleviate liver injury, inhibite the level of ROS, apoptosis and ERS, protect liver function in DILI mice. The mount of M2 was increased in the liver. hMSCs could also induce the production of SGs, inhibit the cGAS-STING pathway and reduce TNF-α, IL-6, IL-1β mRNA expression. The results in vitro showed that hMSCs could induce the production of SGs in macrophages, inhibit the cGAS-STING pathway, promote the secretion of IL-4 and IL-13, and reduce TNF-α, IL-6, IL-1β mRNA level in cells. In the process of IL-4 inducing M2 macrophage activation, anisomycin could inhibit the production of SGs, activate the cGAS-STING pathway, and promote the inflammatory factor TNF-α, IL-6, IL-1β mRNA expression in cells.

CONCLUSIONS

HMSCs had a protective effect on acute DILI in mice induced by APAP. Its mechanism might involve in activating M2 type macrophages, promoting the production of SGs, inhibiting the cGAS-STING pathway, and reducing the expression of pro-inflammatory factors in macrophages, to reduce hepatocytes damage.