Search Results (196)

Protein homeostasis is a dynamic process essential for cellular function and survival, tightly controlled by the ubiquitin–proteasome system. Within this system, ubiquitin-specific protease 7 (USP7) plays a key role as a deubiquitinating enzyme, thus modulating the stability, localization, and activity of a wide variety of substrates. USP7 is involved in critical cellular processes such as DNA repair, apoptosis, immune response, and epigenetic regulation. The dysregulation of USP7 expressions or activity has been linked to several pathological conditions, including cancer, neurodegenerative and inflammatory diseases, and viral infections. This enzyme exerts its biological functions through the stabilization of both oncogenic and tumor suppressor proteins, highlighting its sensitive role in tumorigenesis. Despite the identification of selective USP7 inhibitors with promising preclinical activity, the development of clinically effective compounds remains a major challenge. This review summarizes the current understanding of USP7 structure, function, and biological relevance, with a particular emphasis on its potential as a therapeutic target in oncology. Full article

Background: Gastric cancer is one of the most prevalent malignancies worldwide and the fourth leading cause of cancer-related mortality. Protein ubiquitination and deubiquitination regulate protein stability as post-translational modifications, playing essential roles in tumorigenesis. Although UCHL1, a deubiquitinating enzyme (DUB), is implicated in the progression of several cancer types, its role in gastric cancer remains unclear. Methods: Kaplan–Meier analysis and gastric cancer patient tissues were used to assess UCHL1 expression. Cell viability assay, colony-forming assay, and transwell migration and invasion assay were performed to evaluate cell growth. Immunoprecipitation and Western blotting analyzed protein expression and interactions. Results: This study demonstrates that UCHL1 expression is markedly upregulated in gastric cancer tissues compared to normal tissues. Elevated UCHL1 expression is associated with poor patient prognosis, supporting its potential role as an oncogenic factor. Reduced UCHL1 expression suppressed cell proliferation, migration, and invasion in gastric cancer cell lines. As the underlying mechanism, we identified CIP2A, a known oncogenic regulator of c-Myc, as a downstream effector of UCHL1. UCHL1 knockdown reduced CIP2A protein levels via deubiquitination, attenuated c-Myc signaling, and decreased expression of key cell cycle regulators. Furthermore, UCHL1 knockdown significantly downregulated cyclin D1 expression, arresting the cell cycle in the G1 phase and inhibiting cell proliferation. Conclusions: Collectively, our findings reveal that UCHL1 promotes gastric cancer progression, highlighting it as a potential therapeutic target. Full article

Ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1) is a critical deubiquitinating enzyme that is highly expressed in the central nervous system, where it participates in protein degradation and turnover as part of the ubiquitin–proteasome system (UPS). Convincing evidence supports the role of UCH-L1 dysfunction in several neurodegenerative disorders, given its unique position at the crossroad of several aetiopathogenic pathways, including those implicated in Alzheimer’s disease (AD) onset. Indeed, UCH-L1 depletion correlates with decreased levels of triggering receptor expressed on myeloid cells 2 (TREM2), with consequent effects on neuroinflammation. Notably, UCH-L1 can affect the level of phosphorylated tau protein, thus contributing to the formation of neurofibrillary tangles (NFTs). In addition, UCH-L1 influences β-Secretase 1 (BACE1) expression, resulting in the abnormal accumulation of amyloid-β plaques in brain parenchyma. These findings underline UCH-L1’s centrality in maintaining the homeostasis of protein folding and aggregation, which are significantly impaired in AD and AD-related dementias. Given these assumptions, UCH-L1 is recognized as a potential biomarker for AD, highlighting its relevance in governing the fate of crucial pathological mediators of cognitive impairment and neurodegeneration. Herein, we contextualize the involvement of UCH-L1 in different dementia-associated pathways and summarize the state of the art of UCH-L1 as a biomarker for AD diagnosis. Full article

Epstein-Barr Virus (EBV) is a causative agent of infectious mononucleosis and is strongly associated with Burkitt lymphoma, Hodgkin lymphoma, and nasopharyngeal carcinoma. EBV encodes a deubiquitinating enzyme, BPLF1, which is important for infectious virus production, B-cell immortalization, and tumorigenesis. To elucidate BPLF1’s role, an affinity-based mass spectrometry screen was performed, which suggested that BPLF1 and mTOR interact. mTOR, a critical mediator within cellular signaling cascades and oncogenesis, exists in two distinct complexes: mTOR Complex 1 (mTORC1) and mTOR Complex 2 (mTORC2). Here, we show that BPLF1 has direct deubiquitinating (DUB) activity on mTOR, removing both K48- and K63-ubiquitin linkages. Additionally, WT BPLF1 decreased mTORC1 localization to the lysosome and decreased the phosphorylation of mTORC1 downstream effectors, 4E-BP1 and S6K1. BPLF1 also had DUB activity on Raptor and Rictor, which have both been shown to preferentially cause the formation of mTORC2 over mTORC1 when not ubiquitinated. Immunoprecipitation of mTOR shows decreased mTORC1 formation in the presence of WT BPLF1. Importantly, treatment with rapamycin, an mTORC1 inhibitor, increased infectious virus production, while JR-AB2-011, an mTORC2 inhibitor, reduced infectious virus production. Taken together, these data demonstrate that BPLF1’s effect on the mTOR signaling cascade regulates cellular and viral processes during EBV infectivity and replication. Full article

Mammalian circadian rhythms, governing ~24 h oscillations in behavior, physiology, and hormone levels, are orchestrated by transcriptional–translational feedback loops centered around the core clock protein cryptochrome 1 (CRY1). While CRY1 ubiquitination is known to regulate clock function, the roles of specific ubiquitination sites remain unclear. Here, we identify lysine 151 (K151) as a critical residue modulating the circadian period through non-canonical mechanisms. Using site-directed mutagenesis, we generated CRY1-K151Q/R mutants mimicking constitutive deubiquitination. Circadian rescue assays in Cry1/2-deficient cells revealed period shortening (K151Q: −2.25 h; K151R: −1.4 h; n = 3, p < 0.01, Student’s t-test), demonstrating K151’s functional importance. Despite normal nuclear localization kinetics, K151Q/R mutants exhibited reduced transcriptional repression in luciferase assays, a weakened interaction with BMAL1 by the luciferase complementation assay, and enhanced binding to E3 ligase FBXL12 (but not FBXL3) while showing more stability than wild-type CRY1. Notably, the absence of ubiquitination-linked degradation or altered FBXL3 engagement suggests a ubiquitination-independent mechanism. We propose that CRY1-K151 serves as a structural hub fine-tuning circadian periodicity by modulating core clock protein interactions rather than through traditional ubiquitin-mediated turnover. These findings redefine the mechanistic landscape of post-translational clock regulation and offer new therapeutic avenues for circadian disorders. Full article

Deubiquitination plays a pivotal role in regulating plant responses to abiotic stress, growth, and development. Among the deubiquitinase (DUB) families, ubiquitin-specific proteases (UBPs) constitute the largest group. Despite this, limited research has been conducted on the functional characteristics of the UBP gene family in soybean (Glycine max). In this study, we identified 52 UBP gene family members in soybean, all of which harbored UCH (ubiquitin C-terminal hydrolase) domains with short yet evolutionarily conserved Cys-box and His-box. These genes were phylogenetically classified into 14 distinct groups; GmUBP genes within the same group shared analogous patterns of conserved domains and motifs. Moreover, a synteny analysis reveals that the GmUBP family has undergone extensive gene duplication events and shares a close evolutionary relationship with Arabidopsis thaliana. We conducted a focused analysis on GmUBP7, which is a gene exhibiting high expression levels in soybean seeds. Intriguingly, this gene exhibited several haplotypes in natural soybean varieties, with significant differences being observed in relation to seed traits, such as 100-seed weight, total fatty acid content, and protein content among different haplotypes. Collectively, the findings from this study provide a foundation for the functional characterization of GmUBP genes, offering new insights into the regulatory network underlying seed development in soybean. Full article

The Alternaria alternata tangerine pathotype causes Alternaria brown spot, a devastating disease of susceptible tangerine varieties and their hybrids. Alternaria citri toxin (ACT) is the primary virulence factor, but the regulatory mechanisms governing ACT synthesis remain unclear. Deubiquitinating enzymes maintain ubiquitination homeostasis and regulate fungal pathogenicity, yet their role in A. alternata remains unexplored. We characterized 13 ubiquitin-specific protease (UBP) family members in A. alternata tangerine pathotype. Six UBP genes (Aaubp2, Aaubp3, Aaubp4, Aaubp6, Aaubp14, and Aaubp15) regulated mycelial growth. Aaubp14 deletion abolished sporulation, while mutations of Aaubp3, Aaubp4, Aaubp6, Aaubp8, and Aaubp15 altered conidial morphology. qRT-PCR demonstrated distinct host-induced expression patterns among Aaubp genes. Pathogenicity tests showed that ΔAaubp6, ΔAaubp14, and ΔAaubp15 mutants failed to produce lesions on Citrus reticulata cv. Hongjv leaves. Moreover, Aaubp14 deletion significantly suppressed ACT biosynthesis gene expression and blocked ACT production. Comparative proteomics showed Aaubp14 regulates ACT biosynthesis by modulating protein ubiquitination in metabolic pathways and controls pathogenicity via a complex network. Our findings elucidate Aaubp gene function in development and pathogenicity, particularly the Aaubp14-mediated regulation mechanism, providing insights into ubiquitination-mediated pathogenicity in phytopathogenic fungi. Full article

Infectious bronchitis virus (IBV) is a coronavirus first isolated in the 1930s infecting chickens. IBV causes great economic losses to the global poultry industry, as it affects egg production and causes mortality by leaving the host susceptible to secondary bacterial infections. Even though vaccines are available, they are poorly cross-protective against new variants of the virus, which are always on the cusp of emerging. Effective antiviral therapies, or possibly the production of transgenic animals immune to IBV infection, are therefore sorely needed. As the papain-like protease (PLpro) of IBV has deubiquitinating activity besides its crucial ability to cleave the viral polyprotein, we have applied a novel strategy of selecting ubiquitin variants (UbVs) from a phage-displayed library that have high affinity to this viral protease. These UbVs were found to inhibit the deubiquitinating activity of PLpro and consequently obstruct the virus’s ability to evade the innate immune response in the host cell. By obstructing the proteolytic activity of PLpro, these UbVs were seemingly able to inhibit viral infection as assessed using immunofluorescence microscopy. Whilst virus infection was detected in around 5% of UbV-expressing cells, the virus was present in around 30–40% of GFP (control)-expressing cells. This suggests that the expression of UbVs indeed seems to inhibit IBV infection, making UbVs a potentially potent and innovative antiviral strategy in the quest for control of IBV infections. 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-specific protease (UBP) family constitutes the largest group within the deubiquitinating enzymes (DUBs) and plays a crucial role in regulating the cell cycle, growth, and developmental processes in living organisms. By utilizing genomic and transcriptomic databases, we employed bioinformatics tools to identify UBP family members within pepper genomes and to analyze the expression profiles of CaUBP genes under various abiotic stresses, as well as in different tissues and organs. Our findings revealed the presence of 40 CaUBPs in peppers, exhibiting significant variation in their physicochemical properties. Subcellular localization studies indicated that all CaUBPs are localized in the nucleus. Phylogenetic analysis categorized the 40 CaUBPs into 11 distinct subfamilies (G1–G11), with the largest subfamily comprising seven members. Members within the same subfamily displayed similar domain and motif structures. The promoter regions of CaUBP genes were found to be enriched with elements responsive to light, stress, and hormones. Syntenic analysis revealed that 12 CaUBPs were mapped to the Arabidopsis thaliana genome, suggesting potential functional conservation. Additionally, tandem duplications were observed in the alignment of two sets of genes within the pepper genome. CaUBPs were implicated in the stress response and organ growth, with CaUBP17/34/35 showing significant changes in expression under heat stress. While most genes were not expressed in leaves, the expression of several genes (CaUBP3/17/27/32/35/38) in flowers was significantly altered. This study establishes a foundation for further exploration of the roles of CaUBPs in pepper growth, development, and stress response mechanisms. Full article

Ubiquitin-specific protease 32 (USP32), a deubiquitylating enzyme that controls the ubiquitin process, is overexpressed in multiple cancers and serves as a promising therapeutic target for cancer therapy. Drugs targeting ferroptosis have exhibited promising anticancer activity. Lycobetaine (LBT), a natural alkaloid, holds promise against various cancers, yet its specific targets and anticancer mechanisms remain unclear. In this study, we show that LBT induced ferroptosis in lung squamous cell carcinoma (LUSC) cells, accompanied by glutathione depletion and the accumulation of lipid peroxidation, malondialdehyde, and ferrous iron. Mechanistically, drug affinity responsive target stability-based mass spectrometry analysis, molecular dynamics simulations, and a cellular thermal shift assay confirmed that USP32 is a potential target of LBT in LUSC cells. Moreover, a strong interaction between USP32 and nuclear factor erythroid 2-related factor 2 (NRF2) was found via immunoprecipitation–mass spectrometry and co-immunoprecipitation. In addition, the ubiquitination assay results demonstrated that LBT treatment significantly increased NRF2 ubiquitination and degradation by targeting USP32. Importantly, USP32 overexpression effectively attenuated the effects of LBT on proliferation and ferroptosis in LUSC cells. In orthotopic LUSC xenografts, the administration of LBT significantly inhibited tumor growth and metastasis and induced ferroptosis by targeting the USP32–NRF2 signaling axis. Taken together, these data suggest that LBT exerts its anticancer effects by inhibiting USP32-mediated NRF2 deubiquitination to induce ferroptosis and that LBT may serve as a prospective USP32-targeting agent for LUSC treatment. Full article

Cancer management has traditionally depended on chemotherapy as the mainstay of treatment; however, recent advancements in targeted therapies and immunotherapies have offered new options. Ubiquitin-specific proteases (USPs) have emerged as promising therapeutic targets in cancer treatment due to their crucial roles in regulating protein homeostasis and various essential cellular processes. This review covers the following: (1) the structural and functional characteristics of USPs, highlighting their involvement in key cancer-related pathways, and (2) the discovery, chemical structures, mechanisms of action, and potential clinical implications of USP inhibitors in cancer therapy. Particular attention is given to the role of USP inhibitors in enhancing cancer immunotherapy, e.g., modulation of the tumor microenvironment, effect on regulatory T cell function, and influence on immune checkpoint pathways. Furthermore, this review summarizes the current progress and challenges of clinical trials involving USP inhibitors as cancer therapy. We also discuss the complexities of achieving target selectivity, the ongoing efforts to develop more specific and potent USP inhibitors, and the potential of USP inhibitors to overcome drug resistance and synergize with existing cancer treatments. We finally provide a perspective on future directions in targeting USPs, including the potential for personalized medicine based on specific gene mutations, underscoring their significant potential for enhancing cancer treatment. By elucidating their mechanisms of action, clinical progress, and potential future applications, we hope that this review could serve as a useful resource for both basic scientists and clinicians in the field of cancer therapeutics. Full article

Plants utilize plasma membrane localized receptors like kinases (RLKs) or receptor-like proteins (RLPs) to recognize pathogens and activate pattern-triggered immunity (PTI) responses. A gain-of-function mutation in the Arabidopsis RLP SNC2 (SUPPRESSOR OF NPR1-1, CONSTITUTIVE 2) leads to constitutive activation of defense responses in snc2-1D mutant plants. Transcription factors, SYSTEMIC ACQUIRED RESISTANCE DEFICIENT 1 (SARD1) and CALMODULIN-BINDING PROTEIN 60g (CBP60g), define two parallel pathways downstream of SNC2. The autoimmunity of snc2-1D was partially affected by single mutations in SARD1 or CBP60g but completely suppressed by the sard1 cbp60g double mutant. From a suppressor screen using sard1-1 snc2-1D, we identified a deubiquitinating enzyme ASSOCIATED MOLECULE WITH THE SH3 DOMAIN OF STAM 1 (AMSH1) as a key component in SNC2-mediated plant immunity. A loss-of-function mutation in AMSH1 can suppress the autoimmune responses of sard1-1 snc2-1D. In eukaryotes, selective protein degradation often occurs through the ubiquitination/deubiquitination system. The deubiquitinating enzymes that remove ubiquitin from target proteins play essential roles in controlling the level of target protein ubiquitination and degradation. As loss of AMSH1 results in decreased BDA1 abundance and BDA1 is a transmembrane protein required for SNC2-mediated immunity, AMSH1 likely contributes to immunity regulation through controlling BDA1 stability. Full article

BC is the most commonly diagnosed cancer and the second leading cause of cancer death among women worldwide. Cellular stress is a condition that leads to disrupted homeostasis by extrinsic and intrinsic factors. Among other stressors, hypoxia is a driving force for breast cancer (BC) progression and a general hallmark of solid tumors. Thus, intratumoral hypoxia is an important determinant of invasion, metastasis, treatment failure, prognosis, and patient mortality. Acquisition of the epithelial–mesenchymal transition (EMT) phenotype is also a consequence of tumor hypoxia. The cellular response to hypoxia is mainly regulated by the hypoxia signaling pathway, governed by hypoxia-inducible factors (HIFs), mainly HIF1α. HIFs are a family of transcription factors (TFs), which induce the expression of target genes involved in cell survival and proliferation, metabolic reprogramming, angiogenesis, resisting apoptosis, invasion, and metastasis. HIF1α cooperates with a large number of other TFs. In this review, we focused on the crosstalk and cooperation between HIF1α and other TFs involved in the cellular response to hypoxia in BC. We identified a cluster of TFs, proposed as the HIF1α-TF interactome, that orchestrates the transcription of target genes involved in hypoxia, due to their post-translational modifications (PTMs), including phosphorylation/dephosphorylation, ubiquitination/deubiquitination, SUMOylation, hydroxylation, acetylation, S-nitrosylation, and palmitoylation. PTMs of these HIF1α-related TFs drive their stability and activity, degradation and turnover, and the bidirectional translocation between the cytoplasm or plasma membrane and nucleus of BC cells, as well as the transcription/activation of proteins encoded by oncogenes or inactivation of tumor suppressor target genes. Consequently, PTMs of TFs in the HIF1α interactome are crucial regulatory mechanisms that drive the cellular response to oxygen deprivation in BC cells. Full article

As a crucial post-translational modification (PTM), protein ubiquitination mediates the breakdown of particular proteins, which plays a pivotal role in a large number of biological processes including plant growth, development, and stress response. The ubiquitin-proteasome system (UPS) consists of ubiquitin (Ub), ubiquitinase, deubiquitinating enzyme (DUB), and 26S proteasome mediates more than 80% of protein degradation for protein turnover in plants. For the ubiquitinases, including ubiquitin-activating enzyme (E1), ubiquitin-conjugating enzyme (E2), and ubiquitin ligase (E3), the FBK (F-box Kelch repeat protein) is an essential component of multi-subunit E3 ligase SCF (Skp1-Cullin 1-F-box) involved in the specific recognition of target proteins in the UPS. Many FBK genes have been identified in different plant species, which regulates plant growth and development through affecting endogenous phytohormones as well as plant tolerance to various biotic and abiotic stresses associated with changes in secondary metabolites such as phenylpropanoid, phenolic acid, flavonoid, lignin, wax, etc. The review summarizes the significance of the ubiquitination modification of protein, the role of UPS in protein degradation, and the possible function of FBK genes involved in plant growth, development, secondary metabolism, and stress response, which provides a systematic and comprehensive understanding of the mechanism of ubiquitination and potential function of FBKs in plant species. Full article