Search Results (722)

The Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) has evolved sophisticated immune-evasion strategies to establish a productive infection in the host, primarily by counteracting the innate antiviral response. Here, we demonstrate for the first time that the PRRSV non-structural protein NSP8 suppresses NF-κB-dependent antiviral signalling by hijacking the host ubiquitin-conjugating enzyme UBE2K and inducing the degradation of IKKα, a pivotal kinase in the NF-κB pathway. PRRSV infection led to significant upregulation of host UBE2K, which in turn facilitated viral replication. Mechanistically, we found that NSP8 interacts directly with IKKα, triggering its degradation by the proteasome. Furthermore, we revealed that this process was facilitated by the host protein UBE2K, which acted as a crucial cofactor by directly interacting with NSP8 and thereby enhancing its activity against IKKα. This disruption blocked the activation of the NF-κB pathway and suppressed the expression of downstream antiviral factors, such as TNF-α, IL-6 and IFN-β, ultimately facilitating PRRSV replication. All of these findings showed that NSP8 is an important part of the process by which the host NF-κB pathway is blocked by viruses. This is a new way in which PRRSV avoids the immune system. Full article

Suicide is a major public health concern and cause of death worldwide. While progress has been made in understanding molecular pathways involved in suicide, much more work is needed to identify clinically useful biomarkers of suicidality. Disturbed cellular proteostasis and aggregation of specific misfolded proteins are established pathological factors of neurodegenerative diseases. Increasing evidence also suggests that such aggregates often occur in patients with chronic mental illnesses. Recently, genes related to disturbed proteostasis showed differential methylation in individuals who died by suicide compared to controls. These include five genes encoding proteins that aggregate in neurodegenerative and/or mental illness: CRMP1 (also called DPYSL1), DISC1, MAPT (encoding the Tau protein), PRKN (also called PARK2, encoding Parkin), and SOD1. Given the possibility that altered methylation in these genes could affect expression of the proteins they encode, we aimed to review evidence for whether disturbed proteostasis may be a point of overlap between suicidality, neurodegenerative disease, and/or mental illnesses. Epigenetic changes in most of these genes also occur in other neurological disorders. Autophagy, and, to a lesser extent, the ubiquitin–proteasome system, are emerging as potentially impaired in individuals with suicidal tendencies and individuals who died by suicide. Based on this accumulated data, we hypothesise that disturbed proteostasis is likely to be a pathological component of suicidality. It is also plausible that this may lead to the accumulation of aggregated proteins in a similar manner to, and potentially overlapping with, those seen in major mental illnesses. If true, this would have consequences for potential identification of biomarkers for suicidality and should be a priority for future research in the field. Full article

Lysosomal storage, characterized by the progressive accumulation of undigested substrates in the lysosomal lumen, is a primary driver of various lysosome-related diseases. However, single-cell proteomic remodeling during lysosomal storage remains elusive, and the cellular responses for coping with this condition are poorly understood. Here, we employed deep-coverage single-cell proteomics to analyze C. elegans scavenger cells (coelomocytes) undergoing lysosomal storage. Our analysis revealed profound proteomic remodeling characterized by the massive, asymmetric upregulation of nearly 1000 proteins. We identified a coordinated compensatory response involving the robust induction of endoplasmic reticulum (ER) quality control, including ER unfolded protein response and ER-associated degradation, systemic hyperactivation of the ubiquitin–proteasome system (UPS), and a discordant mitochondrial response featuring concurrent bioenergetic upregulation and severe proteostatic stress. Collectively, this single-cell analysis establishes a high-resolution molecular blueprint of the hierarchical strategies cells employ to survive lysosomal collapse via compensatory quality control mechanisms. Full article

The ubiquitin–proteasome system (UPS) is a highly conserved protein degradation pathway in eukaryotic cells. Through precisely controlled proteolysis of key regulatory proteins, the UPS plays a particularly critical role in plant sexual reproduction, where precise spatiotemporal regulation is essential. The UPS governs multiple aspects of plant sexual reproduction, including male and female gametophyte development, pollen–pistil interactions, double fertilization, and post-fertilization embryogenesis and endosperm development. Among UPS components, E3 ubiquitin ligases play a central role by mediating the spatiotemporal degradation of key proteins, while E2 conjugating enzymes and deubiquitinating enzymes also make essential contributions. Through cross-species and cross-stage comparisons, we find that the UPS exhibits conserved regulatory logic—including cell-cycle gating, spatial control of protein accumulation, and signal integration—while also having evolved lineage-specific functional diversification. In this review, we systematically synthesize UPS functions across the reproductive cycle and highlight persistent knowledge gaps, aiming to provide an integrated framework and a reference for future studies investigating the regulatory roles of the UPS in plant sexual reproduction. Full article

Autophagy is a conserved degradation pathway essential for cellular homeostasis in plants. Selective autophagy confers cargo specificity through receptors, among which NEIGHBOR OF BRCA1 GENE1 (NBR1) is one of the best-characterized. NBR1 mediates the selective turnover of ubiquitinated or stress-damaged cargoes, including protein aggregates and damaged organelles, by linking them to ATG8-decorated autophagosomes via its AIM and UBA domains. This process supports proteostasis, plant development, and adaptation to abiotic stresses, including heat, drought, chilling, salinity, and heavy metals, as well as biotic stresses from bacteria, fungi, viruses, and oomycetes. In this review, we summarize current advances in understanding NBR1 structure, evolutionary conservation, and cargo recognition mechanisms, and highlight its interplay with phytohormone signaling and the ubiquitin–proteasome system (UPS) in shaping plant growth and stress resilience. Full article

Background: Esophageal squamous cell carcinoma (ESCC) remains a highly lethal malignancy with limited therapeutic options, in part due to frequent activation of nuclear factor erythroid 2-related factor 2 (NFE2L2 or NRF2). Gain-of-function mutations in NRF2 disrupt its negative regulation by Kelch-like ECH-associated protein 1 (KEAP1), resulting in sustained NRF2 signaling that promotes tumor growth and resistance to chemotherapy and radiation. We previously identified the FDA-approved drug pyrimethamine (PYR) as an NRF2 inhibitor and demonstrated that inhibition of dihydrofolate reductase (DHFR) represents the primary mechanism underlying its NRF2-suppressive activity, supporting its advancement into a Phase I window-of-opportunity clinical trial (NCT 05678348). Meanwhile, in NRF2^W24C-KYSE70 and NRF2^D77V-KYSE180 cells, PYR promoted NRF2^Mut ubiquitination and proteasomal degradation and shortened its half-life. This study aims to explore additional modes of action by which PYR inhibits NRF2. Methods: Cell cycle analysis was performed by flow cytometry. Cell proliferation, apoptosis and chemosensitivity were assessed by Live-Cell Analysis System, while radiosensitivity was evaluated using X-ray irradiation and the CellTiter-Glo assay. Molecular interactions between NRF2 and KEAP1 were examined through Co-IP and PLA, and the direct binding of PYR to KEAP1 was quantified using ITC and SPR. Molecular docking and dynamic simulations were employed to predict potential PYR-binding pockets within the Kelch domain. Results: Using genetically defined isogenic ESCC cell models, we show that activation of mutant NRF2 (NRF2^Mut) or wild-type NRF2 (NRF2^WT) produces distinct, context-dependent effects on squamous differentiation, proliferation, and therapeutic response. We further demonstrate that PYR restores sensitivity to chemotherapy and ionizing radiation in NRF2^Mut ESCC cells. Mechanistically, short-term PYR treatment promotes KEAP1-dependent proteasome-mediated degradation of NRF2^W24C. Biochemical and biophysical assays indicate that PYR enhances the interaction between KEAP1 and NRF2^W24C in a manner associated with KEAP1-dependent proteasomal degradation. Computational modeling further suggests that PYR may engage a pocket within the Kelch domain to facilitate the NRF2^W24C-KEAP1 interaction. Conclusions: These findings show that PYR functionally restores KEAP1-mediated NRF2 degradation of select NRF2^Mut through a glue-like effect and overcomes therapy resistance in ESCC. Although the proposed glue-like mechanism remains hypothetical, this work supports further investigation into the NRF2–KEAP1 interaction and may inform the development of KEAP1-targeted strategies for NRF2^Mut cancers, including ESCC. Full article

Down syndrome (DS), caused by trisomy 21, is the most prevalent genetic condition associated with accelerated aging and near-universal development of early-onset Alzheimer’s disease (AD). Beyond gene-dosage imbalance, trisomy 21 induces widespread transcriptional, metabolic, and proteomic remodeling that establishes a chronic state of proteotoxic and oxidative stress from early development. Increasing evidence identifies DS as a disorder of proteostasis network failure, in which sustained translational pressure, redox disequilibrium, and degradation pathway insufficiency progressively erode cellular resilience. In the DS brain, persistent endoplasmic reticulum stress with PERK-dominant signaling, mitochondrial dysfunction characterized by oxidative phosphorylation deficits and excessive reactive oxygen species production, and impaired antioxidant responses create a highly vulnerable intracellular environment. Concomitantly, degradation systems become compromised: proteasomal catalytic activity declines, ubiquitin-dependent signaling is remodeled, and chronic mTOR hyperactivation suppresses autophagic and mitophagic flux. The coordinated impairment of the ubiquitin–proteasome system and autophagy establish a feed-forward cycle of proteotoxic accumulation and redox amplification. Within this framework, Alzheimer-like neuropathology in DS emerges not solely from amyloid precursor protein triplication but as the late manifestation of decades-long proteostasis exhaustion. Therapeutic strategies aimed at restoring global proteostasis and redox balance may therefore represent a more effective systems-level approach to mitigating neurodegeneration in DS. Full article

Although LRRK2 mutations modulate systemic glucose homeostasis and metabolic dysfunction precedes Parkinson’s disease (PD) motor symptoms; the way in which pathogenic variants of LRRK2 disrupt astrocytic glucose metabolism and organellar homeostasis remains poorly understood. Here, we demonstrate that LRRK2-I1371V mutation causes profound metabolic and organellar dysfunction in LRRK2-I1371V PD-iPSC-derived astrocytes and U87 cells overexpressing I1371V variant. LRRK2-I1371V astrocytes exhibit significantly reduced GLUT1 expression and cell surface localization, resulting in impaired glucose uptake and decreased lactate production. This metabolic insufficiency correlates with cascading mitochondrial dysfunction, characterized by membrane depolarization, elevated reactive oxygen species, enhanced ubiquitination and reduced proteasomal activity. Reduced LAMP1/LAMP2 expression, impaired lysosomal acidification, and selective cathepsin D deficiency were observed. Accumulation of undegraded cargo was confirmed by transmission electron microscopy upon α-synuclein exposure. ER stress was evident by upregulation of GADD34/CHOP, increased phospho-PERK, and reduced nascent protein synthesis. Increased ER–mitochondrial contact via MAMs and enhanced STIM1-ORAI3 clustering reflect compensatory but ultimately insufficient responses to energy stress. Our results reveal that LRRK2-I1371V induces glucose uptake deficits, leading to energy depletion and integrated ER–mitochondria–lysosome dysfunction, thus indicating restoration of astrocytic metabolic capacity as a potential therapeutic strategy for LRRK2-associated PD. Full article

Cellular protein quality control comprises the ubiquitin proteasome system, autophagy, and molecular chaperones, which maintain proteostasis in healthy tissues. The failure of these cellular and molecular pathways, which normally safeguard the proteome, can cause and even exacerbate amyloidoses, the abnormal accumulation of proteins into amyloid fibrils that drive neurodegeneration. Amyloidoses can also damage peripheral organs; examples include light chain amyloidosis, cardiac amyloidosis, and renal amyloidosis. Restoring proteostasis and preventing protein aggregation is therefore an active area of research, with several promising strategies under investigation. Among these approaches, small-molecule modulators that restore proteostasis are attractive candidates because they may simultaneously rescue multiple quality control mechanisms and remodel aggregates to improve their accessibility to endogenous degradation pathways. Here, we propose that amyloid pathology disrupts multiple proteostasis pathways simultaneously, creating a feedforward cascade in which the breakdown of interconnected proteostasis networks drives progressive protein aggregation, which in turn propels proteostasis collapse. Pharmacological interventions targeting protein aggregation offer opportunity to rescue interconnected proteostasis networks, which could, in turn, cooperatively manage or eliminate pathogenic amyloid burden. Full article

The gut microbiota, acting as a critical extrinsic endocrine organ, is profoundly involved in the pathological evolution and therapeutic response of hormone-dependent malignancies. This review elucidates the core mechanisms governing the microbiota, endocrine, and immune triple-axis. Multi-omic and biochemical evidence demonstrates that microbial metabolic networks, comprising the estrobolome, androbolome, and progestobolome/corticobolome, rely on enzymatic systems such as β-glucuronidases (GUS) and steroid-17,20-desmolases to execute hormone deconjugation and structural modification, thereby modulating systemic steroid exposure. Concurrently, microbe-derived metabolites, such as secondary bile acids and purine derivatives, act as inter-kingdom messengers. These metabolites remodel the tumor immune microenvironment by antagonizing hormone receptors and activating specific signaling axes, such as the Inosine-A2AR pathway. By modulating localized immune cells like effector T cells and myeloid cells, they play a pivotal role in tumor immune evasion. Furthermore, pharmacomicrobiomics reveals a bidirectional regulation between anti-tumor agents and the gut microbiota, where endocrine and immunotherapeutic drugs can induce microbial dysbiosis, while specific gut taxa contribute to primary or acquired resistance by enzymatically inactivating drugs (e.g., reductive inactivation of Enzalutamide) or providing hormonal precursors through bypass pathways. Facing translational challenges, such as real-world microbiome complexity and the colonization resistance of indigenous flora, we propose treating the human body as a unified host–microbe holobiont system. Future research should leverage gnotobiotic models and genetic causal inference to establish functional causality. These efforts will facilitate the development of precision tools, including ubiquitin–proteasome system (UPS) modulators, microbial enzyme inhibitors, and engineered live biotherapeutics. Collectively, these systems biology strategies offer a robust framework for overcoming therapeutic resistance in hormone-dependent malignancies. Full article

Background: Glioblastoma (GBM) is the most common and aggressive brain tumor in adults. Changes in the ubiquitination system in GBM cells can promote uncontrolled tumor growth and reduce the effectiveness of treatments. However, the exact targets and regulatory elements of the ubiquitin–proteasome system involved in GBM are still not well understood. Methods: All data were obtained by using in silico analysis, immunohistochemistry, Western blot, RT-qPCR, gene silencing and proliferation assay. Results: Computational and protein analyses show that aggressive gliomas have higher expression of the RING ligase RNF182, with significantly greater levels in glioblastoma (GBM) than in low-grade gliomas. Elevated RNF182 is strongly associated with GBM growth. Experiments using siRNA to inhibit RNF182 in the human glioblastoma cell line U87MG significantly reduced cell proliferation, suggesting that RNF182 promotes tumor growth and may be a potential therapeutic target. Conclusions: These findings create a connection between the ubiquitin–proteasome system and the unchecked growth observed in GBM, identifying RNF182 as a new marker associated with GBM proliferation and an additional target for GBM treatment. Full article

Ubiquitination is a reversible post-translational modification crucial for cellular homeostasis and protein degradation. It is orchestrated by a cascade of ubiquitin-activating enzymes (E1), conjugating enzymes (E2), and ligases (E3) that tag proteins with ubiquitin, and deubiquitinating enzymes (DUBs) that remove these tags. Through this tightly regulated ubiquitination/deubiquitination system, cells control protein turnover, localization, and activity, thereby governing processes ranging from cell cycle progression and DNA repair to immune and stress responses. Here, we review the structural and functional mechanisms of each class of enzymes in the ubiquitin–proteasome system, including E1, E2, E3, and DUBs, and highlight their roles in key signaling pathways and physiological processes. We further discuss how the dysregulation of these enzymes leads to diseases such as cancer, neurodegenerative disorders, and immune diseases, underlining the potential of targeting ubiquitination pathways for therapeutic intervention. Full article

Molecular subtype–guided therapy for breast cancer (BC) remains limited in a subset of patients by suboptimal efficacy, acquired resistance, and the presence of “undruggable” targets. Proteolysis-targeting chimeras (PROTACs) represent a targeted protein degradation (TPD) strategy that differs fundamentally from conventional occupancy-driven inhibition. By inducing ubiquitination of a protein of interest and subsequent proteasomal degradation, PROTACs can directly reduce pathogenic protein abundance and potentially abrogate non-catalytic or scaffolding functions, thereby enabling more durable pathway suppression in selected resistance contexts. This review comprehensively summarizes the mechanisms of action, key molecular design elements, and the developmental landscape of PROTACs, and maps target selection and research progress across BC molecular subtypes. In hormone receptor–positive/HER2-negative BC, clinical translation is most advanced for estrogen receptor alpha-directed PROTACs; Phase III evidence indicates biomarker-dependent efficacy, with clearer benefit signals in resistant subgroups such as estrogen receptor 1 mutations, suggesting that the net clinical benefit of TPD is more likely to be realized through precision stratification. In contrast, in solid-tumor settings, including human epidermal growth factor receptor 2 (HER2)-positive BC and triple-negative breast cancer, PROTAC translation is more frequently constrained by an “exposure–selectivity–therapeutic window” trade-off driven by physicochemical liabilities, insufficient tumor penetration, and broad target expression. Accordingly, engineering strategies—such as antibody/aptamer-mediated targeted delivery, stimulus-responsive prodrugs, nanocarriers, and local administration—are emerging as decisive approaches to enable safe and effective clinical implementation. Looking forward, further progress of PROTACs in BC will depend on expanding the spectrum of E3 ubiquitin ligases and recruitment modalities, establishing predictable and dynamically monitorable biomarker systems, optimizing rational combination/sequencing regimens with exposure- and schedule-guided dosing, and advancing scalable manufacturing and quality control capabilities, thereby translating mechanistic advantages of TPD into verifiable precision-therapy applications. Full article

Osteosarcoma (OS) is an aggressive bone malignancy with poor prognosis, characterized by high metastasis rates. Kinesin family member 18B (KIF18B), a key protein in cell division and mitosis, has emerged as a potential diagnostic and therapeutic target in various cancers, including OS. This study investigates the role of KIF18B in OS progression and its underlying mechanisms. We found that KIF18B expression is significantly upregulated in OS tissues and correlates with lymph node metastasis (N-stage) and clinical stage. Knockdown of KIF18B inhibited OS cell migration, invasion, proliferation, and tumorigenesis. Mechanistically, KIF18B promotes OS survival through the ubiquitin–proteasome system (UPS) by regulating Skp2 protein degradation. KIF18B knockdown accelerated Skp2 ubiquitination, leading to reduced Skp2 levels and inhibited OS cell viability and glycolytic metabolism. Overexpression of KIF18B enhanced OS cell viability and glycolysis in an Skp2-dependent manner. These findings suggest that the KIF18B-Skp2 axis plays a critical role in the metabolic reprogramming of OS cells and serves as a novel prognostic biomarker and therapeutic target in OS. Full article

As sessile organisms, plants must continuously perceive and integrate external environmental cues with internal developmental signals to optimize growth, reproduction, and survival. Central to this adaptive capacity is the ubiquitin-proteasome system (UPS), the primary pathway for selective protein degradation in eukaryotes. Within the UPS, BTB (Broad-Complex, Tramtrack, and Bric-à-brac) proteins serve as critical substrate adaptors for the Cullin3 (CUL3)-based E3 ubiquitin ligase complex. These proteins play indispensable roles in plant growth, development, hormone signaling, and responses to abiotic stresses. Recent advances have revealed the remarkable functional versatility of BTB proteins, implicating them in the regulation of photomorphogenesis, root architecture, flowering time, stress resilience, and yield-related traits. With 80 BTB-encoding genes in Arabidopsis thaliana and key orthologs identified in major crops—including of rice (Oryza sativa), soybean (Glycine max), and maize (Zea mays)—BTB proteins act as molecular “bridges” that integrate developmental programs with environmental stress signals. This review summarizes the structural features, classification, and multifaceted functions of plant BTB proteins, with an emphasis on their roles in growth regulation, abiotic stress tolerance, light signaling, and agricultural productivity. We further discuss their mechanisms in ubiquitin-dependent proteolysis, transcriptional regulation, and signal integration, offering insights into their potential as targets for engineering climate-resilient crops and advancing sustainable agriculture. Full article