Interplay between autophagy and proteasome during protein turnover

The role of the immunoproteasome in cardiovascular disease

The ubiquitinproteasome system (UPS) is the main mechanism responsible for the intracellular degradation of misfolded or damaged proteins. Under inflammatory conditions, the immunoproteasome, an isoform of the proteasome, can be induced, enhancing the antigen-presenting function of the UPS. Furthermore, the immunoproteasome also serves nonimmune functions, such as maintaining protein homeostasis and regulating signalling pathways, and is involved in the pathophysiological processes of various cardiovascular diseases (CVDs). This review aims to provide a comprehensive summary of the current research on the involvement of the immunoproteasome in cardiovascular diseases, with the ultimate goal of identifying novel strategies for the treatment of these conditions.

ECHDC2 inhibits the proliferation of gastric cancer cells by binding with NEDD4 to degrade MCCC2 and reduce aerobic glycolysis

BACKGROUND

The Enoyl-CoA hydratase/isomerase family plays a crucial role in the metabolism of tumors, being crucial for maintaining the energy balance and biosynthetic needs of cancer cells. However, the enzymes within this family that are pivotal in gastric cancer (GC) remain unclear.

METHODS

We employed bioinformatics techniques to identify key Enoyl-CoA hydratase/isomerase in GC. The expression of ECHDC2 and its clinical significance were validated through tissue microarray analysis. The role of ECHDC2 in GC was further assessed using colony formation assays, CCK8 assay, EDU assay, Glucose and lactic acid assay, and subcutaneous tumor experiments in nude mice. The mechanism of action of ECHDC2 was validated through Western blotting, Co-immunoprecipitation, and immunofluorescence experiments.

RESULTS

Our analysis of multiple datasets indicates that low expression of ECHDC2 in GC is significantly associated with poor prognosis. Overexpression of ECHDC2 notably inhibits aerobic glycolysis and proliferation of GC cells both in vivo and in vitro. Further experiments revealed that overexpression of ECHDC2 suppresses the P38 MAPK pathway by inhibiting the protein level of MCCC2, thereby restraining glycolysis and proliferation in GC cells. Ultimately, it was discovered that ECHDC2 promotes the ubiquitination and subsequent degradation of MCCC2 protein by binding with NEDD4.

CONCLUSIONS

These findings underscore the pivotal role of the ECHDC2 in regulating aerobic glycolysis and proliferation in GC cells, suggesting ECHDC2 as a potential therapeutic target in GC.

A synchronized symphony: Intersecting roles of ubiquitin proteasome system and autophagy in cellular degradation

Eukaryotic cells have evolved dynamic quality control pathways and recycling mechanisms for cellular homeostasis. We discuss here, the two major systems for quality control, the ubiquitin-proteasome system (UPS) and autophagy that regulate cellular protein and organelle turnover and ensure efficient nutrient management, cellular integrity and long-term wellbeing of the plant. Both the pathways rely on ubiquitination signal to identify the targets for proteasomal and autophagic degradation, yet they use distinct degradation machinery to process these cargoes. Nonetheless, both UPS and autophagy operate together as an interrelated quality control mechanism where they communicate with each other at multiple nodes to coordinate and/or compensate the recycling mechanism particularly under development and environmental cues. Here, we provide an update on the cellular machinery of autophagy and UPS, unravel the nodes of their crosstalk and particularly highlight the factors responsible for their differential deployment towards protein, macromolecular complexes and organelles.

circCUL3 drives malignant progression of cervical cancer by activating autophagy through sponge miR-223-3p upregulation of ATG7

Circular RNA (circRNA) has emerged as a pivotal regulatory factor in cancer biology, yet its exact role in cervical cancer remains incompletely understood. In this study, we investigated the functional role of circCUL3 in cervical cancer and explored its potential as a therapeutic target. Functional gain and loss experiments were conducted in Hela and Siha cell lines to elucidate the biological functions of circCUL3 in cervical cancer. The results revealed that circCUL3 overexpression significantly enhanced cell viability, migration, and invasion while suppressing apoptosis, while circCUL3 knockout displayed the opposite effects. Mechanistically, we identified hsa-miR-223-3p as a target of circCUL3, with its expression being negatively regulated by circCUL3. Furthermore, we discovered that circCUL3 could sequester miR-223-3p, leading to the upregulation of ATG7 expression, and this was linked to the regulation of autophagy in cervical cancer cells. In vivo validation using a xenograft mouse model further supported our in vitro findings. Notably, we found that chloroquine (CQ), an autophagy inhibitor, restored miR-223-3p expression and counteracted the oncogenic effect of circCUL3 overexpression. In conclusion, circCUL3 potentially contributes to the malignant progression of cervical cancer by acting as a sponge for miR-223-3p, resulting in the upregulation of ATG7 and the activation of autophagy.

E3 ubiquitin ligase RNF128 negatively regulates the IL-3/STAT5 signaling pathway by facilitating K27-linked polyubiquitination of IL-3Rα

IL-3/STAT5 signaling pathway is crucial for the development and activation of immune cells, contributing to the cellular response to infections and inflammatory stimuli. Dysregulation of the IL-3/STAT5 signaling have been associated with inflammatory and autoimmune diseases characterized by inflammatory cell infiltration and organ damage. IL-3 receptor α (IL-3Rα) specifically binds to IL-3 and initiates intracellular signaling, resulting in the phosphorylation of STAT5. However, the regulatory mechanisms of IL-3Rα remain unclear. Here, we identified the E3 ubiquitin ligase RNF128 as a negative regulator of IL-3/STAT5 signaling by targeting IL-3Rα for lysosomal degradation. RNF128 was shown to selectively bind to IL-3Rα, without interacting with the common beta chain IL-3Rβ, which shares the subunit with GM-CSF. The deficiency of Rnf128 had no effect on GM-CSF-induced phosphorylation of Stat5, but it resulted in heightened Il-3-triggered activation of Stat5 and increased transcription of the Id1, Pim1, and Cd69 genes. Furthermore, we found that RNF128 promoted the K27-linked polyubiquitination of IL-3Rα in a ligase activity-dependent manner, ultimately facilitating its degradation through the lysosomal pathway. RNF128 inhibited the activation and chemotaxis of macrophages in response to LPS stimulation, thereby attenuating excessive inflammatory responses. Collectively, these results reveal that RNF128 negatively regulates the IL-3/STAT5 signaling pathway by facilitating K27-linked polyubiquitination of IL-3Rα. This study uncovers E3 ubiquitin ligase RNF128 as a novel regulator of the IL-3/STAT5 signaling pathway, providing potential molecular targets for the treatment of inflammatory diseases.

The ubiquitin-proteasome system in the plant response to abiotic stress: Potential role in crop resilience improvement

The post-translational modification (PTM) of proteins by ubiquitination modulates many physiological processes in plants. As the major protein degradation pathway in plants, the ubiquitin-proteasome system (UPS) is considered a promising target for improving crop tolerance drought, high salinity, extreme temperatures, and other abiotic stressors. The UPS also participates in abiotic stress-related abscisic acid (ABA) signaling. E3 ligases are core components of the UPS-mediated modification process due to their substrate specificity. In this review, we focus on the abiotic stress-associated regulatory mechanisms and functions of different UPS components, emphasizing the participation of E3 ubiquitin ligases. We also summarize and discuss UPS-mediated modulation of ABA signaling. In particular, we focus our review on recent research into the UPS-mediated modulation of the abiotic stress response in major crop plants. We propose that altering the ubiquitination site of the substrate or the substrate-specificity of E3 ligase using genome editing technology such as CRISPR/Cas9 may improve the resistance of crop plants to adverse environmental conditions. Such a strategy will require continued research into the role of the UPS in mediating the abiotic stress response in plants.

TET2 stabilized by deubiquitinase USP21 ameliorates cigarette smoke-induced apoptosis in airway epithelial cells

DNA demethylase TET2 was related with lung function. However, the precise role of TET2 in cigarette smoke (CS)-induced apoptosis of airway epithelium cells, and the mechanisms involved, have yet to be elucidated. Here, we showed that CS decreased TET2 protein levels but had no significant effect on its mRNA levels in lung tissues of chronic obstructive pulmonary disease (COPD) patients and CS-induced COPD mice model and even in airway epithelial cell lines. TET2 could inhibit CS-induced apoptosis of airway epithelial cell in vivo and in vitro. Moreover, we identified ubiquitin-specific protease 21 (USP21) as a deubiquitinase of TET2 in airway epithelial cells. USP21 interacted with TET2 and inhibited CSE-induced TET2 degradation. USP21 downregulated decreased TET2 abundance and further reduced the anti-apoptosis effect of TET2. Thus, we draw a conclusion that the USP21/TET2 axis is involved in CS-induced apoptosis of airway epithelial cells.

Degrade to stay healthy-Proteolytic interplay during inflammation

Proteasomes and autophagy constitute the 2 main proteolytic machineries for cytoplasmic content. A new study in PLOS Biology now demonstrates that autophagy stimulation alters proteasome composition, degrading hyperactive immunoproteasomes and thereby limiting inflammation.

Dehydrocostus lactone suppresses gastric cancer progression by targeting ACLY to inhibit fatty acid synthesis and autophagic flux

INTRODUCTION

Dehydrocostus lactone (Dehy), a natural sesquiterpene lactone from Saussurea lappa Clarke, displays remarkable efficacy in treating cancer and gastrointestinal disorders. However, its anti-gastric cancer (GC) effect remains poorly understood.

OBJECTIVES

Our study aimed to elucidate the anti-GC effect of Dehy and its putative mechanism.

METHODS

The anti-GC effect was assessed with MTT, colony formation, wound healing and transwell invasion assays. Cell apoptosis rate was detected by Annexin V-FITC/PI binding assay. Network pharmacology analysis and XF substrate oxidation stress test explored the underlying mechanism and altered metabolic phenotype. Lipogenic enzyme expressions and neutral lipid pool were measured to evaluate cellular lipid synthesis and storage. Biolayer interferometry and molecular docking investigated the direct target of Dehy. Autophagosomes were observed by transmission electron microscopy and MDC staining, while the autophagic flux was detected by mRFP-GFP-LC3 transfection. The clinical significance of ACLY was confirmed by tissue microarrays. Patient-derived xenograft (PDX) models were adopted to detect the clinical therapeutic potential of Dehy.

RESULTS

Dehy prominently suppressed GC progression both in vitro and in vivo. Mechanistically, Dehy down-regulated the lipogenic enzyme ACLY, thereby reducing fatty acid synthesis and lipid reservation. Moreover, IKKβ was identified as the direct target of Dehy. Dehy inhibited the phosphorylation of IKKβ, promoting the ubiquitination and degradation of ACLY, thereby resulting in lipid depletion. Subsequently, GC cells initiated autophagy to replenish the missing lipids, whereas Dehy impeded this cytoprotective mechanism by down-regulating LAMP1 and LAMP2 expressions, which disrupted lysosomal membrane functions, ultimately leading to apoptosis. Additionally, Dehy exhibited potential in GC clinical therapy as it enhanced the efficacy of 5-Fluorouracil in PDX models.

CONCLUSIONS

Our work identified Dehy as a desirable agent for blunting abnormal lipid metabolism and highlighted its inhibitory effect on protective autophagy, suggesting the future development of Dehy as a novel therapeutic drug for GC.

Multi-omics insights into the mechanism of the high-temperature tolerance in a thermotolerant Chlorella sorokiniana

Improving high-temperature tolerance of microalgae is crucial to enhance the robustness and economy of microalgae industrial production. Herein, a continuous adaptive laboratory evolution (ALE) system was developed to generate the thermotolerant strain of Chlorella sorokiniana. The resulting thermotolerant strain TR42 exhibited excellent cell growth and biomass production at 42 °C, the temperature that the original strain (OS) could not survive. The high-temperature resistant mechanism of TR42 was investigated by integrating the physiology, transcriptome, proteome and metabolome analyses, which involved enhancing antioxidant capacity, maintaining protein homeostasis, remodeling photosynthetic metabolism, and regulating the synthesis of heat-stress related metabolites. The proof-of-concept high-temperature outdoor cultivation demonstrated that TR42 exhibited 1.15- to 5.72-fold increases in biomass production and 1.62- to 7.04-fold increases in lipid productivity compared to those of OS, respectively, which provided a promising platform for microalgae industrial production. Thus, the multi-system thermotolerant mechanism of TR42 offered potential targets for enhancing high-temperature tolerance of microalgae.

Recent advances in cellular degradation and nuclear control of leaf senescence

Senescence is the final stage of plant growth and development, and is a highly regulated process at the molecular, cellular, and organismal levels. When triggered by age, hormonal, or environmental cues, plants actively adjust their metabolism and gene expression to execute the progression of senescence. Regulation of senescence is vital for the reallocation of nutrients to sink organs, to ensure reproductive success and adaptations to stresses. Identification and characterization of hallmarks of leaf senescence are of great importance for understanding the molecular regulatory mechanisms of plant senescence, and breeding future crops with more desirable senescence traits. Tremendous progress has been made in elucidating the genetic network underpinning the metabolic and cellular changes in leaf senescence. In this review, we focus on three hallmarks of leaf senescence - chlorophyll and chloroplast degradation, loss of proteostasis, and activation of senescence-associated genes (SAGs), and discuss recent findings of the molecular players and the crosstalk of senescence pathways.

Genome-wide analysis of WD40 protein family and functional characterization of BvWD40-82 in sugar beet

Sugar beet is one of the most important sugar crops in the world. It contributes greatly to the global sugar production, but salt stress negatively affects the crop yield. WD40 proteins play important roles in plant growth and response to abiotic stresses through their involvement in a variety of biological processes, such as signal transduction, histone modification, ubiquitination, and RNA processing. The WD40 protein family has been well-studied in Arabidopsis thaliana, rice and other plants, but the systematic analysis of the sugar beet WD40 proteins has not been reported. In this study, a total of 177 BvWD40 proteins were identified from the sugar beet genome, and their evolutionary characteristics, protein structure, gene structure, protein interaction network and gene ontology were systematically analyzed to understand their evolution and function. Meanwhile, the expression patterns of BvWD40s under salt stress were characterized, and a BvWD40-82 gene was hypothesized as a salt-tolerant candidate gene. Its function was further characterized using molecular and genetic methods. The result showed that BvWD40-82 enhanced salt stress tolerance in transgenic Arabidopsis seedlings by increasing the contents of osmolytes and antioxidant enzyme activities, maintaining intracellular ion homeostasis and increasing the expression of genes related to SOS and ABA pathways. The result has laid a foundation for further mechanistic study of the BvWD40 genes in sugar beet tolerance to salt stress, and it may inform biotechnological applications in improving crop stress resilience.