Search Results (685)

Cadmium (Cd) pollution poses a serious threat to freshwater ecosystems. The freshwater mussel Anodonta woodiana is increasingly used as a bioindicator for monitoring Cd pollution in aquatic environments. However, the primary routes of Cd accumulation in A. woodiana remain unclear, and the molecular regulatory mechanisms underlying Cd accumulation are poorly understood. To address these gaps, this study employed a novel stable isotope dual-tracer technique to trace Cd from water (waterborne ¹¹²Cd) and the green alga Chlorella vulgaris (dietary ¹¹³Cd) during the simultaneous exposure experiment. Comparative transcriptomic analysis was then conducted to characterize molecular responses in A. woodiana following Cd exposure. The results showed that although newly accumulated ¹¹²Cd and ¹¹³Cd increased with exposure concentration and duration, the relative importance of ¹¹²Cd (91.6 ± 2.8%) was significantly higher than that of ¹¹³Cd (8.4 ± 2.8%) (p < 0.05). Cd exposure induced differentially expressed genes primarily enriched in the metabolic processes, cellular processes, and/or the ubiquitin-mediated proteolysis pathway. Within the ubiquitin-mediated proteolysis pathway, TRIP12 (E3 ubiquitin-protein ligase TRIP12) and Cul5 (cullin-5) were significantly upregulated. The findings will provide critical insights for interpreting Cd biomonitoring data in freshwater environments using mussels as bioindicators. Full article

Ubiquitination is a dynamic and reversible post-translational modification mediated by ubiquitination regulators (UBRs), which plays an essential role in protein stability, cell differentiation and immunity. Dysregulation of UBRs can lead to destabilization of biological processes and may induce serious human diseases, including cancer. Many UBRs, such as E3 ubiquitin ligases and deubiquitinases (DUBs), have been identified as potential drug targets for cancer therapy. However, the potential clinical value of UBRs in lung adenocarcinoma (LUAD) remains to be elucidated. Here, we identified 17 hub UBRs from high-confidence protein–protein interaction networks of UBRs correlated with cancer hallmark-related pathways using four topological algorithms. The expression of hub UBRs is affected by copy number variation and post-transcriptional regulation, and their high expression is often detrimental to patient survival. Based on the expression profiles of hub UBRs, patients can be classified into two ubiquitination subtypes with different characteristics. These subtypes exhibit significant differences across multiple dimensions, including survival, expression level, mutation burden, female predominance, infiltration level, immune profile, and drug response. In addition, we established a scoring system for evaluating the ubiquitination status of individual LUAD patients, called the ubiquitination-related risk (UB_risk) score, and found that patients with low scores are more likely to gain advantages from immunotherapy. The results of this study emphasize the critical role of ubiquitination in the classification, tumor microenvironment and immunotherapy of LUAD. The construction of the UB_risk scoring system lays a research foundation for evaluating the ubiquitination status of individual LUAD patients and formulating precise treatment strategies from the ubiquitination level. Full article

The global burden of respiratory viral infections is notable, which is attributed to their higher transmissibility compared to other viral diseases. Respiratory viruses are seen to have evolved resistance to available treatment options. Although vaccines and antiviral drugs control some respiratory viruses, this control is limited due to unexpected events, such as mutations and the development of antiviral resistance. The technology of proteolysis-targeting chimeras (PROTACs) has been emerging as a novel technology in viral therapeutics. These are small molecules that can selectively degrade target proteins via the ubiquitin–proteasome pathway. PROTACs as a therapy were initially developed against cancer, but they have recently shown promising results in their antiviral mechanisms by targeting viral and/or host proteins involved in the pathogenesis of viral infections. In this review, we elaborate on the antiviral potential of PROTACs as therapeutic agents and their potential as vaccine components against important respiratory viral pathogens, including influenza viruses, coronaviruses (SARS-CoV-2), and respiratory syncytial virus. Advanced applications of PROTAC antiviral strategies, such as hemagglutinin and neuraminidase degraders for influenza and spike proteins of SARS-CoV-2, are detailed in this review. Additionally, the role of PROTACs in targeting cellular mechanisms within the host, thereby preventing viral pathogenesis and eliciting an antiviral effect, is discussed. The potential of PROTACs as vaccines, utilizing proteasome-based virus attenuation to achieve a robust protective immune response, while ensuring safety and enhancing efficient production, is also presented. With the promises exhibited by PROTACs, this technology faces significant challenges, including the emergence of novel viral strains, tissue-specific expression of E3 ligases, and pharmacokinetic constraints. With advanced computational design in molecular platforms, PROTAC-based antiviral development offers an alternative, transformative path in tackling respiratory viruses. Full article

Aberrant activation of the mitogen-activated protein kinase (MAPK) cascade promotes oncogenic transcriptomes. Despite efforts to inhibit oncogenic kinases, such as BRAFV600E, tumor responses in patients can be heterogeneous and limited by drug resistance mechanisms. Here, we describe patient tumors that acquired COP1 or DET1 mutations after treatment with the BRAF^V600E inhibitor vemurafenib. COP1 and DET1 constitute the substrate adaptor of the E3 ubiquitin ligase CRL4^COP1/DET1, which targets transcription factors, including ETV1, ETV4, and ETV5, for proteasomal degradation. MAPK-MEK-ERK signaling prevents CRL4^COP1/DET1 from ubiquitinating ETV1, ETV4, and ETV5, but the mechanistic details are still being elucidated. We found that patient mutations in COP1 or DET1 inactivated CRL4^COP1/DET1 in melanoma cells, stabilized ETV1, ETV4, and ETV5, and conferred resistance to inhibitors of the MAPK pathway. ETV5, in particular, enhanced cell survival and was found to promote the expression of the pro-survival gene BCL2A1. Indeed, the deletion of pro-survival BCL2A1 re-sensitized COP1 mutant cells to vemurafenib treatment. These observations indicate that the post-translational regulation of ETV5 by CRL4^COP1/DET1 modulates transcriptional outputs in ERK-dependent cancers, and its inactivation contributes to therapeutic resistance. Full article

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi (T. cruzi), continues to pose significant public health challenges due to the toxicity, poor tolerability, and limited efficacy of current treatments. Targeted protein degradation (TPD) using proteolysis-targeting chimeras (PROTACs) represents a novel therapeutic avenue by leveraging the ubiquitin–proteasome system to selectively degrade essential parasite proteins. This review introduces the conceptual framework of “TrypPROTACs” as a prospective strategy for T. cruzi, integrating a comprehensive analysis of druggable targets across critical biological pathways, including ergosterol biosynthesis, redox metabolism, glycolysis, nucleotide synthesis, protein kinases, molecular chaperones such as heat shock protein 90 (Hsp90), and epigenetic regulators such as T. cruzi bromodomain factor 3 (TcBDF3). It is important to note that no TrypPROTAC compound has yet been synthesized or experimentally validated in T. cruzi; the approach discussed herein remains theoretical and forward-looking. Representative inhibitors for each target class are compiled, highlighting potency, selectivity, and structural features relevant to ligand design. We also examine the parasite’s ubiquitination machinery and compare it to the human system to identify putative E3 ubiquitin ligases. Key aspects of linker engineering and ternary complex stabilization are discussed, alongside potential validation techniques such as the cellular thermal shift assay (CETSA) and bioluminescence resonance energy transfer (NanoBRET). Collectively, these insights outline a roadmap for the rational design of TrypPROTACs and support the feasibility of expanding targeted protein degradation strategies to neglected tropical diseases. Full article

Plant U-box (PUB) E3 ubiquitin ligases have undergone significant expansion compared to their fungal and animal counterparts. These E3 ligases play critical roles in diverse biological processes, including responses to biotic and abiotic stresses. However, systematic identification of PUB genes in cucumber (Cucumis sativus L.) has been lacking, and their expression and functional characterization remain largely unexplored. Leveraging the recently released near-complete cucumber genome, we identified 53 putative PUB proteins classified into eight distinct groups based on domain architecture. The molecular weights of CsPUBs range from 26 to 166 kilodaltons (kDa). Exon numbers in CsPUB genes vary substantially, with CsPUB48 containing a maximum of 17 exons, while 18 CsPUB genes harbor only a single exon. Chromosomal distribution of CsPUBs is uneven, with Chr 3 harboring the highest density (12 genes) and Chr 7 the lowest (1 gene). Notably, tandem duplications (e.g., CsPUB29-CsPUB36 and CsPUB18-CsPUB49) and seven collinear gene pairs were identified, suggesting evolutionary diversification. Promoter regions of CsPUBs are enriched with cis-regulatory elements linked to plant growth and development, phytohormone, stress responses, light, and so on, implying their regulatory roles in various biological processes. Expression profiling revealed tissue-specific patterns and differential regulation of multiple CsPUBs under stress conditions. Subcellular localization studies demonstrated that CsPUBs target diverse organelles, with some localizing to punctate structures potentially representing uncharacterized compartments. Collectively, this systematic analysis establishes a comprehensive framework for understanding particular CsPUB functions. Full article

Targeted protein degradation (TPD) has emerged as a revolutionary strategy for modulating protein function, offering a promising alternative to traditional small-molecule inhibitors. The distinctive mechanism of action in TPD has previously allowed researchers to target undruggable proteins, broadening the scope of “druggable” properties and expanding the scope of therapeutic possibilities. As the field of TPD advances, several alternative strategies to proteolysis-targeting chimeras (PROTACs) have emerged, which do not rely on the E3 ubiquitin ligase recruitment mechanism, expending the scope of TPD. Recently, several new technologies have emerged for TPD of extracellular and membrane proteins. While encouraging progress has been made in this field, the application of these technologies remains in its early stages. In this review, we explore the therapeutic potential of current key emerging lysosome-mediated TPD approaches by summarizing key discoveries and address the challenges associated with degrading extracellular and membrane protein targets. We also outline the chemical structure, activity, and pharmaceutical properties of each degrader, as well as the development of chemical probes for perturbing autophagy pathways. Full article

Alzheimer’s disease (AD) is marked by the pathological accumulation of amyloid beta-42 (Aβ42), contributing to synaptic dysfunction and neurodegeneration. While extracellular amyloid plaques are well-studied, increasing evidence highlights intracellular Aβ42 as an early and toxic driver of disease progression. In this study, we present a novel, Generative AI–based drug design approach to promote targeted degradation of Aβ42 via the ubiquitin–proteasome system (UPS), using E3 ligase–directed molecular glues. We systematically evaluated the ternary complex formation potential of Aβ42 with three E3 ligases (CRBN, VHL, and MDM2) through structure-based modeling, ADMET screening, and docking. We then developed a Ligase-Conditioned Junction Tree Variational Autoencoder (LC-JT-VAE) to generate ligase-specific small molecules, incorporating protein sequence embeddings and torsional angle-aware molecular graphs. Our results demonstrate that this generative model can produce chemically valid, novel, and target-specific molecular glues capable of facilitating Aβ42 degradation. This integrated approach offers a promising framework for designing UPS-targeted therapies for neurodegenerative diseases. Full article

RNA-binding E3 ubiquitin ligases (RBULs) provide a link between RNA metabolic processes and the ubiquitin proteasome system (UPS). In humans, RBULs are involved in various biological processes, such as cell proliferation and differentiation, as well as sexual development. To date, little is known about their role in the protozoan parasite Plasmodium falciparum, the causative agent of malaria tropica. We previously identified a novel P. falciparum RBUL, the RING finger E3 ligase PfRNF1, which is highly expressed during gametocyte development. Here, we conducted BioID-based proximity interaction studies to unveil the PfRNF1 interactome. We show that in immature gametocytes, PfRNF1 forms an interaction network that is mainly composed of RNA-binding proteins, including the translational repressors DOZI and CITH and members of the CCR4-NOT complex, as well as UPS-related proteins. In particular, PfRNF1 interacts with recently identified regulators of sexual development like the zinc finger protein PfMD3, with which it shares the majority of interactors. The common interactome of PfRNF1 and PfMD3 comprises several uncharacterized proteins predominantly expressed in male or female gametocytes. Our results demonstrate that PfRNF1 engages with RNA-binding proteins crucial for sex determination in gametocytes, thereby linking posttranscriptional regulation with the UPS. Full article

Transcription factors (TFs) play central roles in gene regulation and disease progression but have long been considered undruggable due to the absence of well-defined binding pockets and their reliance on protein–protein or protein–DNA interactions. Proteolysis-targeting chimeras (PROTACs) offer a novel strategy to overcome these limitations by inducing selective degradation of TFs via the ubiquitin–proteasome system. This review highlights recent advances in TF-targeting PROTACs, focusing on key oncogenic TFs such as androgen receptor (AR), estrogen receptor alpha (ERα), BRD4, c-Myc, and STAT family members. Strategies for ligand design—including small molecules, peptides, and nucleic acid-based elements—are discussed alongside the use of various E3 ligases such as VHL, CRBN, and IAP. Several clinically advanced PROTACs, including ARV-110 and ARV-471, demonstrate the therapeutic potential of this technology. Despite challenges in pharmacokinetics and E3 ligase selection, emerging data suggest that PROTACs can successfully target TFs, paving the way for new treatment strategies across oncology and other disease areas. Full article

The U-box E3 ubiquitin ligase (PUB) gene family plays an important role in regulating plant responses to abiotic stress. Poncirus trifoliata (trifoliate orange), a citrus rootstock with notable cold, drought, and salt tolerance, serves as an excellent model for studying stress-responsive genes. In this study, a total of 47 PUB genes (PtrPUBs) were identified in the trifoliate orange genome. Chromosomal distribution analysis indicated that PtrPUB genes were unevenly distributed across nine trifoliate orange chromosomes. Phylogenetic tree analysis indicated that 170 PUB proteins from trifoliate orange, Arabidopsis thaliana, and tomato were clustered into five subfamilies. Gene structure, conserved domain, and motif analyses revealed diverse exon–intron and motif organizations of PtrPUB genes, suggesting potential functional differentiation among PtrPUBs. Cis-acting analysis indicated that the promoters of PtrPUB genes harbor elements related to hormone signaling (ABA, MeJA), drought stress, and low-temperature responses. Transcriptomic data and qRT-PCR results suggested that PtrPUB genes are responsive to ABA and dehydration treatments. This study provides a foundation for understanding the functional roles of PUB genes in trifoliate orange and offers insights for improving stress tolerance in citrus breeding programs. Full article

RNF213 encodes a unique protein with AAA+ ATPase and E3 ubiquitin ligase activities that are critical for its diverse roles, which range from involvement in human vasculopathies, such as Moyamoya disease, to ubiquitination of viral and bacterial pathogens. Nevertheless, its primary functions in human signaling remain unclear due to the limited identification of direct substrates. Here, we investigated the interaction between RNF213 and caveolin-1 (Cav-1), a small scaffolding protein vital for caveolae formation and the regulation of a plethora of cellular processes. Cav-1 specifically binds within the two functional AAA+ domains of RNF213 in an ATP-dependent manner, highlighting the influence of cellular energy status on this interaction. Consequently, RNF213 ubiquitinates Cav-1 at several N-terminal lysine residues through K48 and K63 linkages, although several Moyamoya disease-associated RNF213 mutations greatly reduce this polyubiquitination. Moreover, RNF213 activity inhibits phosphorylation of a key regulatory residue of Cav-1, as RNF213 knockdown under oxidative stress markedly enhances Cav-1 Tyr14 phosphorylation and modifies nitric oxide bioavailability in endothelial cells. Collectively, our results indicate that RNF213 functions as a molecular switch modulating Cav-1 signaling based on RNF213 functionality and cellular conditions. These findings offer new insights into vascular pathogenesis and the vast signal pathways along the RNF213–Cav-1 axis. Full article

Tripartite motif (TRIM) 25 is a member of the TRIM E3 ubiquitin ligase family, which plays multiple roles in anti-tumor and antiviral defenses through various pathways. Its RBCC and SPRY/PRY domains work cooperatively for its oligomerization and subsequent activation of ligase activity. TRIM25 expression is regulated by several proteins and RNAs, and it functionally participates in the post-transcriptional and translational modification of antiviral regulators, such as RIG-I, ZAP, and avSGs. Conversely, the antiviral functions of TRIM25 are inhibited by viral proteins and RNAs through their interactions, as well as by the viral infection-mediated upregulation of certain miRNAs. Here, we review the antiviral functions of TRIM25 and highlight its significance regarding innate immunity, particularly in antiviral defense and viral immune evasion. Full article

E3 ubiquitin ligases and deubiquitinating enzymes (DUBs) are pivotal regulators of bone homeostasis, orchestrating osteoblast differentiation, proliferation, and osteoclast activity by controlling protein degradation and stability. This review delineates the roles of key E3 ligases (e.g., Smurf1, Smurf2, TRIM family) and DUBs (e.g., USP family) in bone formation and resorption. E3 ligases such as Smurf1/2 inhibit osteogenesis by degrading BMP/Smad signaling components, while TRIM proteins and HERC ligases promote osteoblast differentiation. Conversely, DUBs like USP2 and USP34 stabilize β-catenin and Smad1/RUNX2, enhancing osteogenic pathways, whereas USP10 and USP12 suppress differentiation. Dysregulation of these enzymes contributes to osteoporosis, fracture non-union, and other bone disorders. The interplay between ubiquitination and deubiquitination, alongside the regulatory role of miRNA and environmental factors, underscores their therapeutic potential. Future research should focus on developing therapies targeting E3 ubiquitin ligases, deubiquitinases, miRNA regulators, and small-molecule inhibitors to restore bone homeostasis in osteoporosis and fracture healing disorders. Full article

The ubiquitin–proteasome system (UPS) plays a pivotal role in determining protein fate, regulating signal transduction, and maintaining cellular homeostasis. Protein ubiquitination, a key post-translational modification, is orchestrated by the sequential actions of three primary enzymes, ubiquitin-activating enzyme (E1), ubiquitin-conjugating enzyme (E2), and ubiquitin protein ligase (E3), alongside the regulatory influence of deubiquitinases (DUBs) and various cofactors. The process begins with E1, which activates ubiquitin molecules. Subsequently, E2 receives the activated ubiquitin from E1 and transfers it to E3. E3, in turn, recognizes specific target proteins and facilitates the covalent attachment of ubiquitin from E2 to lysine residues on the target protein. Among the E2 enzymes, ubiquitin-conjugating enzyme E2O (UBE2O) stands out as a unique E2–E3 hybrid enzyme. UBE2O directly mediates the ubiquitination of a wide array of substrates, including 5′-AMP-activated protein kinase catalytic subunit alpha-2 (AMPKα2), MAX interactor 1 (Mxi1), and v-maf musculoaponeurotic fibrosarcoma oncogene homolog (c-Maf), among others. In this narrative review, we will explore the structural characteristics of UBE2O and elucidate its molecular functions. Additionally, we will summarize recent advancements in understanding the role of UBE2O in various tumors, Alzheimer’s disease (AD), and metabolic diseases. Finally, we will discuss the potential of targeting UBE2O as a novel therapeutic strategy for the treatment of human diseases. Full article