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Background: Ferroptosis is extremely relevant to the progression of neurodegenerative pathologies such as Alzheimer's disease (AD). Ubiquitin-specific proteases (USP) can affect the NADPH oxidase family. Objective: Our study aimed to elucidate the potential role and molecular basis of a certain USP19 in reducing ferroptosis and mitochondrial injury in AD cells by targeting NOX4 stability. Methods: The deubiquitinase USP family gene USP19, which affects the stability of NOX4 protein, was first screened. The cell model of AD was constructed after interfering with SH-SY5Y cells by Aβ1-40, and then SH-SY5Y cells were infected with lentiviral vectors to knock down USP19 and overexpress NOX4, respectively. Finally, the groups were tested for cell viability, changes in cellular mitochondrial membrane potential, lipid reactive oxygen species, intracellular iron metabolism, and NOX4, Mf1, Mf2, and Drp1 protein expression. Results: 5 μmol/L Aβ1-40 intervened in SH-SY5Y cells for 24 h to construct a cell model of AD. Knockdown of USP19 decreased the expression of NOX4 protein, promoted the expression of mitochondrial fusion proteins Mnf1 and Mnf2, and inhibited the expression of the splitting protein Drp1. Furthermore, USP19 knockdown decreased mitochondrial membrane potential, SOD, MDA, intracellular iron content and increased GSH/GSSG ratio in SH-SY5Y cells. Our study revealed that NOX4 protein interacts with USP19 and knockdown of USP19 enhanced ubiquitination to maintain NOX4 protein stability. Conclusions: USP19 attenuates mitochondrial damage in SH-SY5Y cells by targeting NOX4 protein with Aβ1-40. [ABSTRACT FROM AUTHOR]

Ubiquitin-specific protease 5 (USP5) belongs to the ubiquitin-specific protease (USP) family, which uniquely recognizes unanchored polyubiquitin chains to maintain the homeostasis of monoubiquitin chains. USP5 participates in a wide range of cellular processes by specifically cleaving isopeptide bonds between ubiquitin and substrate proteins or ubiquitin itself. In the process of immune regulation, USP5 affects important cellular signaling pathways, such as NF-κB, Wnt/β-catenin, and IFN, by regulating ubiquitin-dependent protein degradation. These pathways play important roles in immune regulation and inflammatory responses. In addition, USP5 regulates the activity and function of immunomodulatory signaling pathways via the deubiquitination of key proteins, thereby affecting the activity of immune cells and the regulation of immune responses. In the present review, the structure and function of USP5, its role in immune regulation, and the mechanism by which USP5 affects the development of diseases by regulating immune signaling pathways are comprehensively overviewed. In addition, we also introduce the latest research progress of targeting USP5 in the treatment of related diseases, calling for an interdisciplinary approach to explore the therapeutic potential of targeting USP5 in immune regulation. [ABSTRACT FROM AUTHOR]

N-acetylneuraminic acid (Neu5Ac) is the predominant form of sialic acid present in the glossy swiftlet (Collocalia esculenta). It is also the only form of sialic acid detected in the human body. In this study, we investigated the mechanism underlying melanogenesis inhibition by Neu5Ac. We discovered that a reduction in tyrosinase protein levels led to an inhibition of melanin production by Neu5Ac. Additionally, the mRNA and protein levels of ubiquitin-specific protease (USP5) and microtubule-associated protein 1 light chain 3 (LC3)-II increased, while those of p62 decreased, indicating enhanced autophagic activity. Lysosomal cathepsin L2 protein levels also increased, and immunostaining revealed colocalization of lysosomal membrane protein (LAMP)-1 and tyrosinase. Additionally, levels of chaperonin containing T-complex polypeptide (CCT), implicated in increased autophagic flux, were elevated. Altogether, these findings suggest that tyrosinase-containing coated vesicles are transported by Neu5Ac into the autophagic degradation pathway, suppressing mature melanosome generation. This process involves increased USP5 levels preventing recognition of polyubiquitin by proteasomes. Furthermore, elevated CCT3 protein levels may enhance autophagic flux, leading to the incorporation of tyrosinase-containing coated vesicles into autophagosomes. These autophagosomes then fuse with lysosomes for cathepsin L2–mediated degradation. Thus, our findings suggest that Neu5Ac reduces tyrosinase activity and inhibits melanosome maturation by promoting selective autophagic degradation of abnormal proteins by p62. [ABSTRACT FROM AUTHOR]

Abstract Background CDC6 is an oncogenic protein whose expression level fluctuates during the cell cycle. Although several E3 ubiquitin ligases responsible for the ubiquitin-mediated proteolysis of CDC6 have been identified, the deubiquitination pathway for CDC6 has not been investigated. Methods The proteome-wide deubiquitinase (DUB) screening was used to identify the potential regulator of CDC6. Immunofluorescence, protein half-life and deubiquitination assays were performed to determine the protein stability of CDC6. Gain- and loss-of-function experiments were implemented to analyse the impacts of OUTD6A-CDC6 axis on tumour growth and chemosensitivity in vitro. N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN)-induced conditional Otud6a knockout (CKO) mouse model and tumour xenograft model were performed to analyse the role of OTUD6A-CDC6 axis in vivo. Tissue specimens were used to determine the association between OTUD6A and CDC6. Results OTUD6A interacts with, depolyubiquitinates and stabilizes CDC6 by removing K6-, K33-, and K48-linked polyubiquitination. Moreover, OTUD6A promotes cell proliferation and decreases sensitivity to chemotherapy by upregulating CDC6. CKO mice are less prone to BCa tumorigenesis induced by BBN, and knockdown of OTUD6A inhibits tumour progression in vivo. Furthermore, OTUD6A protein level has a positive correlation with CDC6 protein level, and high protein levels of OTUD6A and CDC6 are associated with poor prognosis in patients with bladder cancer. Conclusions We reveal an important yet missing piece of novel DUB governing CDC6 stability. In addition, our findings propose a model for the OTUD6A-CDC6 axis that provides novel insights into cell cycle and chemosensitivity regulation, which may become a potential biomarker and promising drug target for cancer treatment.

The balance between ubiquitination and deubiquitination is instrumental in the regulation of protein stability and maintenance of cellular homeostasis. The deubiquitinating enzyme, ubiquitin-specific protease 36 (USP36), a member of the USP family, plays a crucial role in this dynamic equilibrium by hydrolyzing and removing ubiquitin chains from target proteins and facilitating their proteasome-dependent degradation. The multifaceted functions of USP36 have been implicated in various disease processes, including cancer, infections, and inflammation, via the modulation of numerous cellular events, including gene transcription regulation, cell cycle regulation, immune responses, signal transduction, tumor growth, and inflammatory processes. The objective of this review is to provide a comprehensive summary of the current state of research on the roles of USP36 in different pathological conditions. By synthesizing the findings from previous studies, we have aimed to increase our understanding of the mechanisms underlying these diseases and identify potential therapeutic targets for their treatment. [ABSTRACT FROM AUTHOR]

Cerebrovascular diseases (CVDs) are a major threat to global health. Elucidation of the molecular mechanisms underlying the pathology of CVDs is critical for the development of efficacious preventative and therapeutic approaches. Accumulating studies have highlighted the significance of ubiquitin‐modifying enzymes (UMEs) in the regulation of CVDs. UMEs are a group of enzymes that orchestrate ubiquitination, a post‐translational modification tightly involved in CVDs. Functionally, UMEs regulate multiple pathological processes in ischemic and hemorrhagic stroke, moyamoya disease, and atherosclerosis. Considering the important roles of UMEs in CVDs, they may become novel druggable targets for these diseases. Besides, techniques applying UMEs, such as proteolysis‐targeting chimera and deubiquitinase‐targeting chimera, may also revolutionize the therapy of CVDs in the future. [ABSTRACT FROM AUTHOR]

Background: CDC6 is an oncogenic protein whose expression level fluctuates during the cell cycle. Although several E3 ubiquitin ligases responsible for the ubiquitin-mediated proteolysis of CDC6 have been identified, the deubiquitination pathway for CDC6 has not been investigated. Methods: The proteome-wide deubiquitinase (DUB) screening was used to identify the potential regulator of CDC6. Immunofluorescence, protein half-life and deubiquitination assays were performed to determine the protein stability of CDC6. Gain- and loss-of-function experiments were implemented to analyse the impacts of OUTD6A-CDC6 axis on tumour growth and chemosensitivity in vitro. N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN)-induced conditional Otud6a knockout (CKO) mouse model and tumour xenograft model were performed to analyse the role of OTUD6A-CDC6 axis in vivo. Tissue specimens were used to determine the association between OTUD6A and CDC6. Results: OTUD6A interacts with, depolyubiquitinates and stabilizes CDC6 by removing K6-, K33-, and K48-linked polyubiquitination. Moreover, OTUD6A promotes cell proliferation and decreases sensitivity to chemotherapy by upregulating CDC6. CKO mice are less prone to BCa tumorigenesis induced by BBN, and knockdown of OTUD6A inhibits tumour progression in vivo. Furthermore, OTUD6A protein level has a positive correlation with CDC6 protein level, and high protein levels of OTUD6A and CDC6 are associated with poor prognosis in patients with bladder cancer. Conclusions: We reveal an important yet missing piece of novel DUB governing CDC6 stability. In addition, our findings propose a model for the OTUD6A-CDC6 axis that provides novel insights into cell cycle and chemosensitivity regulation, which may become a potential biomarker and promising drug target for cancer treatment. [ABSTRACT FROM AUTHOR]

Summary: Eukaryotes have evolved sophisticated post‐translational modifications to regulate protein function and numerous biological processes, including ubiquitination controlled by the coordinated action of ubiquitin‐conjugating enzymes and deubiquitinating enzymes (Dubs). However, the function of deubiquitination in pathogenic fungi is largely unknown.Here, the distribution of Dubs in the fungal kingdom was surveyed and their functions were systematically characterized using the phytopathogen Fusarium graminearum as the model species, which causes devastating diseases of all cereal species world‐wide.Our findings demonstrate that Dubs are critical for fungal development and virulence, especially the ubiquitin‐specific protease 15 (Ubp15). Global ubiquitome analysis and subsequent experiments identified three important substrates of Ubp15, including the autophagy‐related protein Atg8, the mitogen‐activated protein kinase Gpmk1, and the mycotoxin deoxynivalenol (DON) biosynthetic protein Tri4. Ubp15 regulates the deubiquitination of the Atg8, thereby impacting its subcellular localization and the autophagy process. Moreover, Ubp15 also modulates the deubiquitination of Gpmk1 and Tri4. This modulation subsequently influences their protein stabilities and further affects the formation of penetration structures and the biosynthetic process of DON, respectively.Collectively, our findings reveal a previously unknown regulatory pathway of a deubiquitinating enzyme for fungal virulence and highlight the potential of Ubp15 as a target for combating fungal diseases. [ABSTRACT FROM AUTHOR]

Background & aimsThe stimulator of interferon genes (STING)/TANK-binding kinase 1 (TBK1) pathway is vital in mediating innate immune and inflammatory responses during oxidative/endoplasmic reticulum (ER) stress. However, it remains unknown whether macrophage thioredoxin-interacting protein (TXNIP) may regulate TBK1 function and cell death pathways during oxidative/ER stress.MethodsA mouse model of hepatic ischaemia/reperfusion injury (IRI), the primary hepatocytes, and bone marrow-derived macrophages were used in the myeloid-specific TXNIP knockout (TXNIPM-KO) and TXNIP-proficient (TXNIPFL/FL) mice.ResultsThe TXNIPM-KO mice were resistant to ischaemia/reperfusion (IR) stress-induced liver damage with reduced serum alanine aminotransferase (ALT)/aspartate aminotransferase (AST) levels, macrophage/neutrophil infiltration, and pro-inflammatory mediators compared with the TXNIPFL/FL controls. IR stress increased TXNIP, p-STING, and p-TBK1 expression in ischaemic livers. However, TXNIPM-KO inhibited STING, TBK1, interferon regulatory factor 3 (IRF3), and NF-κB activation with interferon-β (IFN-β) expression. Interestingly, TXNIPM-KO augmented nuclear factor (erythroid-derived 2)-like 2 (NRF2) activity, increased antioxidant gene expression, and reduced macrophage reactive oxygen species (ROS) production and hepatic apoptosis/necroptosis in IR-stressed livers. Mechanistically, macrophage TXNIP deficiency promoted cylindromatosis (CYLD), which colocalised and interacted with NADPH oxidase 4 (NOX4) to enhance NRF2 activity by deubiquitinating NOX4. Disruption of macrophage NRF2 or its target gene 2',5' oligoadenylate synthetase-like 1 (OASL1) enhanced Ras GTPase-activating protein-binding protein 1 (G3BP1) and TBK1-mediated inflammatory response. Notably, macrophage OASL1 deficiency induced hepatocyte apoptotic peptidase activating factor 1 (APAF1), cytochrome c, and caspase-9 activation, leading to increased caspase-3-initiated apoptosis and receptor-interacting serine/threonine-protein kinase 3 (RIPK3)-mediated necroptosis.ConclusionsMacrophage TXNIP deficiency enhances CYLD activity and activates the NRF2-OASL1 signalling, controlling IR stress-induced liver injury. The target gene OASL1 regulated by NRF2 is crucial for modulating STING-mediated TBK1 activation and Apaf1/cytochrome c/caspase-9-triggered apoptotic/necroptotic cell death pathway. Our findings underscore a novel role of macrophage TXNIP-mediated CYLD-NRF2-OASL1 axis in stress-induced liver inflammation and cell death, implying the potential therapeutic targets in liver inflammatory diseases.Lay summaryLiver inflammation and injury induced by ischaemia and reperfusion (the absence of blood flow to the liver tissue followed by the resupply of blood) is a significant cause of hepatic dysfunction and failure following liver transplantation, resection, and haemorrhagic shock. Herein, we uncover an underlying mechanism that contributes to liver inflammation and cell death in this setting and could be a therapeutic target in stress-induced liver inflammatory injury.

Cells respond to invading pathogens and danger signals from the environment by adapting gene expression to meet the need for protective effector molecules. While this innate immune response is required for the cell and the organism to recover, excess immune activation may lead to loss of homeostasis, thereby promoting chronic inflammation and cancer progression. The molecular basis of innate immune defence is comprised of factors promoting survival and proliferation, such as cytokines, antimicrobial peptides and anti‐apoptotic proteins. As the molecular mechanisms regulating innate immune responses are conserved through evolution, the fruit fly Drosophila melanogaster serves as a convenient, affordable and ethical model organism to enhance understanding of immune signalling. Fly immunity against bacterial infection is built up by both cellular and humoral responses, where the latter is regulated by the Imd and Toll pathways activating NF‐κB transcription factors Relish, Dorsal and Dif, as well as JNK activation and JAK/STAT signalling. As in mammals, the Drosophila innate immune signalling pathways are characterised by ubiquitination of signalling molecules followed by ubiquitin receptors binding to the ubiquitin chains, as well as by rapid changes in protein levels by ubiquitin‐mediated targeted proteasomal and lysosomal degradation. In this review, we summarise the molecular signalling pathways regulating immune responses to pathogen infection in Drosophila, with a focus on ubiquitin‐dependent control of innate immunity and inflammatory signalling. [ABSTRACT FROM AUTHOR]

Abstract Cerebrovascular diseases (CVDs) are a major threat to global health. Elucidation of the molecular mechanisms underlying the pathology of CVDs is critical for the development of efficacious preventative and therapeutic approaches. Accumulating studies have highlighted the significance of ubiquitin‐modifying enzymes (UMEs) in the regulation of CVDs. UMEs are a group of enzymes that orchestrate ubiquitination, a post‐translational modification tightly involved in CVDs. Functionally, UMEs regulate multiple pathological processes in ischemic and hemorrhagic stroke, moyamoya disease, and atherosclerosis. Considering the important roles of UMEs in CVDs, they may become novel druggable targets for these diseases. Besides, techniques applying UMEs, such as proteolysis‐targeting chimera and deubiquitinase‐targeting chimera, may also revolutionize the therapy of CVDs in the future.

Ubiquitin-specific protease 5 (USP5) belongs to the ubiquitin-specific protease (USP) family, which uniquely recognizes unanchored polyubiquitin chains to maintain the homeostasis of monoubiquitin chains. USP5 participates in a wide range of cellular processes by specifically cleaving isopeptide bonds between ubiquitin and substrate proteins or ubiquitin itself. In the process of immune regulation, USP5 affects important cellular signaling pathways, such as NF-κB, Wnt/β-catenin, and IFN, by regulating ubiquitin-dependent protein degradation. These pathways play important roles in immune regulation and inflammatory responses. In addition, USP5 regulates the activity and function of immunomodulatory signaling pathways via the deubiquitination of key proteins, thereby affecting the activity of immune cells and the regulation of immune responses. In the present review, the structure and function of USP5, its role in immune regulation, and the mechanism by which USP5 affects the development of diseases by regulating immune signaling pathways are comprehensively overviewed. In addition, we also introduce the latest research progress of targeting USP5 in the treatment of related diseases, calling for an interdisciplinary approach to explore the therapeutic potential of targeting USP5 in immune regulation.

Objective To explore the antitumor small molecules targeting the ubiquitin–proteasome system (UPS) on the basis of active molecules from traditional Chinese medicine. Methods UbG76V-GFP stably expressing cell line was constructed to screen novel small molecule inhibitors targeting UPS. The fluorogenic substrates of Suc-LLVY-AMC, Z-LLE-AMC, and Boc-LRR-AMC were used to assess the effect of dioscin on the 20S proteasome hydrolase activity. The Ub-AMC substrate was used to evaluate the effect of dioscin on the intracellular deubiquitinating enzyme activity. Western blot was used to detect the effect of dioscin on intracellular ubiquitination levels. CCK-8 and colony formation assays were used to detect the inhibitory effect of dioscin on the tumor cell proliferation. Results Dioscin is a UPS inhibitor discovered through the UbG76V-GFP reporter system. It enhances intracellular ubiquitination and inhibits tumor cell proliferation and colony formation by targeting deubiquitinating enzymes. Conclusion Dioscin could significantly inhibit tumor cell proliferation by targeting ubiquitin–proteasome.

N-acetylneuraminic acid (Neu5Ac) is the predominant form of sialic acid present in the glossy swiftlet (Collocalia esculenta). It is also the only form of sialic acid detected in the human body. In this study, we investigated the mechanism underlying melanogenesis inhibition by Neu5Ac. We discovered that a reduction in tyrosinase protein levels led to an inhibition of melanin production by Neu5Ac. Additionally, the mRNA and protein levels of ubiquitin-specific protease (USP5) and microtubule-associated protein 1 light chain 3 (LC3)-II increased, while those of p62 decreased, indicating enhanced autophagic activity. Lysosomal cathepsin L2 protein levels also increased, and immunostaining revealed colocalization of lysosomal membrane protein (LAMP)-1 and tyrosinase. Additionally, levels of chaperonin containing T-complex polypeptide (CCT), implicated in increased autophagic flux, were elevated. Altogether, these findings suggest that tyrosinase-containing coated vesicles are transported by Neu5Ac into the autophagic degradation pathway, suppressing mature melanosome generation. This process involves increased USP5 levels preventing recognition of polyubiquitin by proteasomes. Furthermore, elevated CCT3 protein levels may enhance autophagic flux, leading to the incorporation of tyrosinase-containing coated vesicles into autophagosomes. These autophagosomes then fuse with lysosomes for cathepsin L2–mediated degradation. Thus, our findings suggest that Neu5Ac reduces tyrosinase activity and inhibits melanosome maturation by promoting selective autophagic degradation of abnormal proteins by p62.

The balance between ubiquitination and deubiquitination is instrumental in the regulation of protein stability and maintenance of cellular homeostasis. The deubiquitinating enzyme, ubiquitin-specific protease 36 (USP36), a member of the USP family, plays a crucial role in this dynamic equilibrium by hydrolyzing and removing ubiquitin chains from target proteins and facilitating their proteasome-dependent degradation. The multifaceted functions of USP36 have been implicated in various disease processes, including cancer, infections, and inflammation, via the modulation of numerous cellular events, including gene transcription regulation, cell cycle regulation, immune responses, signal transduction, tumor growth, and inflammatory processes. The objective of this review is to provide a comprehensive summary of the current state of research on the roles of USP36 in different pathological conditions. By synthesizing the findings from previous studies, we have aimed to increase our understanding of the mechanisms underlying these diseases and identify potential therapeutic targets for their treatment.

Objective To explore the antitumor small molecules targeting the ubiquitin–proteasome system (UPS) on the basis of active molecules from traditional Chinese medicine. Methods UbG76V-GFP stably expressing cell line was constructed to screen novel small molecule inhibitors targeting UPS. The fluorogenic substrates of Suc-LLVY-AMC, Z-LLE-AMC, and Boc-LRR-AMC were used to assess the effect of dioscin on the 20S proteasome hydrolase activity. The Ub-AMC substrate was used to evaluate the effect of dioscin on the intracellular deubiquitinating enzyme activity. Western blot was used to detect the effect of dioscin on intracellular ubiquitination levels. CCK-8 and colony formation assays were used to detect the inhibitory effect of dioscin on the tumor cell proliferation. Results Dioscin is a UPS inhibitor discovered through the UbG76V-GFP reporter system. It enhances intracellular ubiquitination and inhibits tumor cell proliferation and colony formation by targeting deubiquitinating enzymes. Conclusion Dioscin could significantly inhibit tumor cell proliferation by targeting ubiquitin–proteasome. [ABSTRACT FROM AUTHOR]

ABSTRACTMed1 binds to a nuclear receptor and regulates transcription. Elevated Med1 protein expression promotes cancer growth in hormone-dependent breast and prostate cancers. Med1 protein expression was investigated by deubiquitinating enzymes (DUBs) overexpression in breast cancer cell lines. Various DNA constructs of SRT-DUBs were overexpressed in the MCF7 cell line, and Med1 protein expression was investigated by western blotting. The cell growth and in vitro invasion assay were performed in BRCA1-associated protein 1 (BAP1) wild type and mutant (C91A) overexpressed cells. Ubiquitination of the Med1 protein was observed, and Med1 protein expression and transcriptional activity were verified by various DUBs overexpressed. Although Med1 protein expression increased upon the overexpression of BAP1, it was not affected by the overexpression of BAP1 mutant (C91A). BAP1 was increased by the E2 treatment, which has an important effect on the breast cancer growth, and cell growth was decreased by BAP1 C91A overexpression. However, metastatic capacities were decreased by BAP1. In addition, the binding between the Med1 and the BAP1 protein was observed. These data suggested that BAP1 regulated Med1 protein expression in breast cancer cells and involved in cancer cell growth and metastasis by binding to Med1 protein.

The pathogenicmechanisms of pancreatic cancer (PC) are still not fully understood. Ubiquitination modifications have a crucial role in tumorigenesis and progression. Yet, the role of MINDY2, amember of the motif interacting with Ub-containing novel DUB family (MINDY), as a newly identified deubiquitinating enzyme, in PC is still unclear. In this study, we found that MINDY2 expression is elevated in PC tissue (clinical samples) and was associated with poor prognosis. We also found that MINDY2 is associated with pro-carcinogenic factors such as epithelialmesenchymal transition (EMT), inflammatory response, and angiogenesis; the ROC curve suggested that MINDY2 has a high diagnostic value in PC. Immunological correlation analysis suggested that MINDY2 is deeply involved in immune cell infiltration in PC and is associated with immune checkpoint-related genes. In vivo and in vitro experiments further suggested that elevated MINDY2 promotes PC proliferation, invasive metastasis, and EMT. Meanwhile, actinin alpha 4 (ACTN4) was identified as a MINDY2-interacting protein by mass spectrometry and other experiments, and ACTN4 protein levels were significantly correlated with MINDY2 expression. The ubiquitination assay confirmed that MINDY2 stabilizes the ACTN4 protein level by deubiquitination. The pro-oncogenic effect of MINDY2 was significantly inhibited by silencing ACTN4. Bioinformatics Analysis and Western blot experiments further confirmed that MINDY2 stabilizes ACTN4 through deubiquitination and thus activates the PI3K/AKT/mTOR signaling pathway. In conclusion, we identified the oncogenic role and mechanism of MINDY2 in PC, suggesting that MINDY2 is a viable candidate gene for PC and may be a therapeutic target and critical prognostic indicator. [ABSTRACT FROM AUTHOR]

Ubiquitin‐specific protease 4 (USP4) is highly overexpressed in colon cancer and acts as a potent protooncogenic protein by deubiquitinating β‐catenin. However, its prominent roles in tumor formation and migration in cancer cells are not fully understood by its deubiquitinating enzyme (DUB) activity on β‐catenin. Thus, we investigated an additional role of USP4 in cancer. In this study, we identified cortactin (CTTN), an actin‐binding protein involved in the regulation of cytoskeleton dynamics and a potential prognostic marker for cancers, as a new cellular interacting partner of USP4 from proximal labeling of HCT116 cells. Additionally, the role of USP4 in CTTN activation and promotion of cell dynamics and migration was investigated in HCT116 cells. We confirmed that interacting of USP4 with CTTN increased cell movement. This finding was supported by the fact that USP4 overexpression in HCT116 cells with reduced expression of CTTN was insufficient to promote cell migration. Additionally, we observed that USP4 overexpression led to a significant increase in CTTN phosphorylation, which is a requisite mechanism for cell migration, by regulating Src/focal adhesion kinase (FAK) binding to CTTN and its activation. Our results suggest that USP4 plays a dual role in cancer progression, including stabilization of β‐catenin as a DUB and interaction with CTTN to promote cell dynamics by inducing CTTN phosphorylation. Therefore, this study demonstrates that USP4 is important for cancer progression and is a good target for treating or preventing cancer. [ABSTRACT FROM AUTHOR]

In ovarian cancer patients, the 5-year survival rate is 90% for stages I and II, but only 30% for stages III and IV. Unfortunately, as 75% of the patients are diagnosed at stages III and IV, many experience a recurrence. To ameliorate this, it is necessary to develop new biomarkers for early diagnosis and treatment. The ubiquitin–proteasome system is a post-translational modification that plays an important role in regulating protein stability through ubiquitination. In particular, deubiquitinating enzymes (DUBs) regulate protein stability through deubiquitinating substrate proteins. In this review, DUBs and substrates regulated by these enzymes are summarized based on their functions in ovarian cancer cells. This would be useful for the discovery of biomarkers for ovarian cancer and developing new therapeutic candidates. [ABSTRACT FROM AUTHOR]

Abstract Objective Pregnancy is characterized by well-defined immunological adaptions within the maternal immune cell compartment allowing the survival of a genetically disparate individual in the maternal womb. Phenotype and function of immune cells are largely determined by intracellular processing of external stimuli. Ubiquitinating and deubiquitinating enzymes are known to critically regulate immune signaling either by modulating the stability or the interaction of the signaling molecules. Accordingly, if absent, critical physiological processes may be perturbed such as fetal tolerance induction. Based on previous findings that mice hemizygous for the deubiquitinating enzyme otubain 1 (OTUB1) do not give rise to homozygous progeny, here, we investigated whether partial OTUB1 deficiency influences fetal-wellbeing in a syngeneic or an allogeneic pregnancy context accompanied by changes in the dendritic cell (DC) and T cell compartment. Results We observed increased fetal rejection rates in allogeneic pregnant OTUB1 heterozygous dams but not syngeneic pregnant OTUB1 heterozygous dams when compared to OTUB1 wildtype dams. Fetal demise in allogeneic pregnancies was not associated with major changes in maternal peripheral and local DC and T cell frequencies. Thus, our results suggest that OTUB1 confers fetal protection, however, this phenotype is independent of immune responses involving DC and T cells.

Protein ubiquitination, which is catalyzed by ubiquitin-activating enzymes, ubiquitin-conjugating enzymes, and ubiquitin ligases, is a crucial post-translational modification to regulate numerous cellular functions in a spatio–temporal-specific manner. The human genome encodes ~100 deubiquitinating enzymes (DUBs), which antagonistically regulate the ubiquitin system. OTUD1, an ovarian tumor protease (OTU) family DUB, has an N-terminal-disordered alanine-, proline-, glycine-rich region (APGR), a catalytic OTU domain, and a ubiquitin-interacting motif (UIM). OTUD1 preferentially hydrolyzes lysine-63-linked ubiquitin chains in vitro; however, recent studies indicate that OTUD1 cleaves various ubiquitin linkages, and is involved in the regulation of multiple cellular functions. Thus, OTUD1 predominantly functions as a tumor suppressor by targeting p53, SMAD7, PTEN, AKT, IREB2, YAP, MCL1, and AIF. Furthermore, OTUD1 regulates antiviral signaling, innate and acquired immune responses, and cell death pathways. Similar to Nrf2, OTUD1 contains a KEAP1-binding ETGE motif in its APGR and regulates the reactive oxygen species (ROS)-mediated oxidative stress response and cell death. Importantly, in addition to its association with various cancers, including multiple myeloma, OTUD1 is involved in acute graft-versus-host disease and autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, and ulcerative colitis. Thus, OTUD1 is an important DUB as a therapeutic target for a variety of diseases. [ABSTRACT FROM AUTHOR]

Huntington’s disease (HD) is a neurodegenerative disorder caused by a CAG repeat expansion in the N-terminus of the HTT gene. The CAG repeat expansion translates into a polyglutamine expansion in the mutant HTT (mHTT) protein, resulting in intracellular aggregation and neurotoxicity. Lowering the mHTT protein by reducing synthesis or improving degradation would delay or prevent the onset of HD, and the ubiquitin-proteasome system (UPS) could be an important pathway to clear the mHTT proteins prior to aggregation. The UPS is not impaired in HD, and proteasomes can degrade mHTT entirely when HTT is targeted for degradation. However, the mHTT protein is differently ubiquitinated when compared to wild-type HTT (wtHTT), suggesting that the polyQ expansion affects interaction with (de) ubiquitinating enzymes and subsequent targeting for degradation. The soluble mHTT protein is associated with several ubiquitin-modifying enzymes, and various ubiquitin-modifying enzymes have been identified that are linked to Huntington’s disease, either by improving mHTT turnover or affecting overall homeostasis. Here we describe their potential mechanism of action toward improved mHTT targeting towards the proteostasis machinery.

Objective: Pregnancy is characterized by well-defined immunological adaptions within the maternal immune cell compartment allowing the survival of a genetically disparate individual in the maternal womb. Phenotype and function of immune cells are largely determined by intracellular processing of external stimuli. Ubiquitinating and deubiquitinating enzymes are known to critically regulate immune signaling either by modulating the stability or the interaction of the signaling molecules. Accordingly, if absent, critical physiological processes may be perturbed such as fetal tolerance induction. Based on previous findings that mice hemizygous for the deubiquitinating enzyme otubain 1 (OTUB1) do not give rise to homozygous progeny, here, we investigated whether partial OTUB1 deficiency influences fetal-wellbeing in a syngeneic or an allogeneic pregnancy context accompanied by changes in the dendritic cell (DC) and T cell compartment. Results: We observed increased fetal rejection rates in allogeneic pregnant OTUB1 heterozygous dams but not syngeneic pregnant OTUB1 heterozygous dams when compared to OTUB1 wildtype dams. Fetal demise in allogeneic pregnancies was not associated with major changes in maternal peripheral and local DC and T cell frequencies. Thus, our results suggest that OTUB1 confers fetal protection, however, this phenotype is independent of immune responses involving DC and T cells. [ABSTRACT FROM AUTHOR]

Protein ubiquitination is a widespread, multifunctional, posttranslational protein modification, best known for its ability to direct protein degradation via the ubiquitin proteasome system (UPS). Ubiquitination is also reversible, and the human genome encodes over 90 deubiquitinating enzymes (DUBs), many of which appear to target specific subsets of ubiquitinated proteins. This review focuses on the roles of DUBs in neurodevelopmental disorders (NDDs). We present the current genetic evidence connecting 12 DUBs to a range of NDDs and the functional studies implicating at least 19 additional DUBs as candidate NDD genes. We highlight how the study of DUBs in NDDs offers critical insights into the role of protein degradation during brain development. Because one of the major known functions of a DUB is to antagonize the UPS, loss of function of DUB genes has been shown to culminate in loss of abundance of its protein substrates. The identification and study of NDD DUB substrates in the developing brain is revealing that they regulate networks of proteins that themselves are encoded by NDD genes. We describe the new technologies that are enabling the full resolution of DUB protein networks in the developing brain, with the view that this knowledge can direct the development of new therapeutic paradigms. The fact that the abundance of many NDD proteins is regulated by the UPS presents an exciting opportunity to combat NDDs caused by haploinsufficiency, because the loss of abundance of NDD proteins can be potentially rectified by antagonizing their UPS-based degradation. [ABSTRACT FROM AUTHOR]

Ubiquitin specific protease 7 (USP7) is a deubiquitinating enzyme, which removes ubiquitin tag from numerous protein substrates involved in diverse cellular processes such as cell cycle regulation, apoptosis and DNA damage response. USP7 affects stability, interaction network and cellular localization of its cellular and viral substrates by controlling their ubiquitination status. The large 41 kDa catalytic domain of USP7 harbors the active site of the enzyme. Here we present a nearly complete (93%) NMR resonance assignment of isoleucine, leucine and valine (ILV) side-chains of the USP7 catalytic domain along with a refined nearly complete (93%) assignment of its backbone resonances. The reported ILV methyl group assignment will facilitate further NMR investigations of structure, interactions and conformational dynamics of the USP7 enzyme. [ABSTRACT FROM AUTHOR]

The Epstein-Barr virus (EBV) is implicated in several cancers, including EBV-associated gastric cancer (EBVaGC). This study focuses on EBV-encoded BALF1 (BamH1 A fragment leftward reading frame 1), a key apoptosis regulator in EBV-related cancers, whose specific impact on EBVaGC was previously unknown. Our findings indicate that BALF1 overexpression in gastric cancer cells significantly enhances their proliferation, migration, and resistance to chemotherapy-induced apoptosis, confirming BALF1's oncogenic potential. A novel discovery is that BALF1 undergoes degradation via the ubiquitin-proteasome pathway. Through analysis of 69 deubiquitinating enzymes (DUBs), ovarian tumor protease (OTU) domain-containing protein 1 (OTUD1) emerged as a vital regulator for maintaining BALF1 protein stability. Furthermore, BALF1 was found to play a role in regulating the stability of the B-cell lymphoma-2 (Bcl-2) protein, increasing its levels through deubiquitination. This mechanism reveals BALF1's multifaceted oncogenic role in gastric cancer, as it contributes both directly and indirectly to cancer progression, particularly by stabilizing Bcl-2, known for its anti-apoptotic characteristics. These insights significantly deepen our understanding of EBV's involvement in the pathogenesis of gastric cancer. The elucidation of OTUD1's role in BALF1 regulation and its influence on Bcl-2 stabilization provide new avenues for therapeutic intervention in EBVaGC, bridging the gap between viral oncogenesis and cellular protein regulation and offering a more holistic view of gastric cancer development under the influence of EBV. • EBVaGC is regarded as the most prevalent malignant tumor triggered by EBV infection. • While EBV-encoded BALF1 is crucial in EBVaGC, its specific function remains unclear. • OTUD1 was identified as BALF1's key deubiquitinase via screening of a DUBs library. • BALF1 acts to deubiquitinate Bcl-2, leading to stabilization of its protein levels. • Increased apoptosis blocker Bcl-2 may explain EBVaGC's heightened aggressiveness. [ABSTRACT FROM AUTHOR]

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease in which motor neurons in spinal cord and motor cortex are progressively lost. About 15% cases of ALS also develop the frontotemporal dementia (FTD), in which the frontotemporal lobar degeneration (FTLD) occurs in the frontal and temporal lobes of the brain. Among the pathologic commonalities in ALS and FTD is ubiquitin-positive cytoplasmic aggregation of TDP-43 that may reflect both its loss-of-function and gain-of-toxicity from proteostasis impairment. Deep understanding of how protein quality control mechanisms regulate TDP-43 proteinopathies still remains elusive. Recently, a growing body of evidence indicates that ubiquitinating and deubiquitinating pathways are critically engaged in the fate decision of aberrant or pathological TDP-43 proteins. E3 ubiquitin ligases coupled with deubiquitinating enzymes may influence the TDP-43-associated proteotoxicity through diverse events, such as protein stability, translocation, and stress granule or inclusion formation. In this article, we recapitulate our current understanding of how ubiquitinating and deubiquitinating mechanisms can modulate TDP-43 protein quality and its pathogenic nature, thus shedding light on developing targeted therapies for ALS and FTD by harnessing protein degradation machinery.

As an important form of posttranslational modification, protein ubiquitination regulates a wide variety of biological processes, including different aspects of T cell development and differentiation. During T cell development, thymic seeding progenitor cells (TSPs) in the thymus undergo multistep maturation programs and checkpoints, which are critical to build a functional and tolerant immune system. Currently, a tremendous amount of research has focused on the transcriptional regulation of thymocyte development. However, in the past few years, compelling evidence has revealed that the ubiquitination system also plays a crucial role in the regulation of thymocyte developmental programs. In this review, we summarize recent findings on the molecular mechanisms and cellular pathways that regulate thymocyte ubiquitination and discuss the roles of E3 ligases and deubiquitinating enzymes (DUBs) involved in these processes. Understanding how T cell development is regulated by ubiquitination and deubiquitination will not only enhance our understanding of cell fate determination via gene regulatory networks but also provide potential novel therapeutic strategies for treating autoimmune diseases and cancer. [ABSTRACT FROM AUTHOR]

The CDC73/HRPT2 gene, a defect which causes hyperparathyroidism–jaw tumor (HPT-JT) syndrome, encodes CDC73/parafibromin. We aimed to investigate whether CDC73 would be a target for ubiquitin–proteasome degradation. We cloned full-length cDNAs encoding a family of 58 ubiquitin-specific deubiquitinating enzymes (DUBs), also known as ubiquitin-specific proteases (USPs). Use of the yeast two-hybrid system then enabled us to identify USP37 as interacting with CDC73. The biochemical interaction between the USP37 and CDC73 and their reciprocal binding domains were studied. Co-localization of CDC73 and USP37 was observed in cells. CDC73 was found to be polyubiquitinated, and polyubiquitination of CDC73 was prominent in mutants. CDC73 was deubiquitinated via K48-specific ubiquitin chains by USP37, but not by the catalytically inactive USP37C350S mutant. Observation of the binding between deletion mutants of CDC73 and USP37 revealed that the β-catenin binding site of CDC73 and the ubiquitin-interacting motifs 2 and 3 (UIM2 and 3) of USP37 were responsible for the interaction between the two proteins. Moreover, these two enzymes co-existed within the nucleus of COS7 cells. We conclude that USP37 is a DUB for CDC73 and that the two proteins interact through specific domains, suggesting that USP37 is responsible for the stability of CDC73 in HPT-JT syndrome. [ABSTRACT FROM AUTHOR]

The Ubp family of deubiquitinating enzymes has been found to play important roles in plant‐pathogenic fungi, but their regulatory mechanisms are still largely unknown. In this study, we revealed the regulatory mechanism of the deubiquitinating enzyme Ubp3 during the infection process of Magnaporthe oryzae. AUBP3 deletion mutant was severely defective in appressorium turgor accumulation, leading to the impairment of appressorial penetration. During appressorium formation, the mutant was also defective in glycogen and lipid metabolism. Interestingly, we found that nitrogen starvation and rapamycin treatment induced the ribophagy process in M. oryzae, which is closely dependent on Ubp3. In the ∆ubp3 mutant, the ribosome proteins and rRNAs were not well degraded on nitrogen starvation and rapamycin treatment. We also found that Ubp3 interacted with the GTPase‐activating protein Smo1 and regulated its de‐ubiquitination. Ubp3‐dependent de‐ubiquitination of Smo1 may be required for Smo1 to coordinate Ras signalling. Taken together, our results showed at least two roles of Ubp3 in M. oryzae: it regulates the ribophagy process and it regulates de‐ubiquitination of GTPase‐activating protein Smo1 for appressorium‐mediated infection. [ABSTRACT FROM AUTHOR]

Background: Breast cancer is a prevalent disease that has a dismal prognosis for patients and a bad outlook for treatments. Ubiquitination is a reversible biological process that regulates protein production and degradation, as well as plays a vital role in protein transport, localization, and biological activity., Methods: We obtained the breast cancer patient sample data and used a machine learning technique to create a novel index called Deubiquitinating enzyme related index (DUBRI) by gathering genes associated to deubiquitinating enzymes. Based on DUBRI, we systematically analyze patients' prognosis, clinical characteristics, tumor immune microenvironment, chemotherapy response and immunotherapy response. Finally, the function of OTUB2 was explored in breast cancer cells., Results: DUBRI, which consists of five deubiquitinating enzyme genes (OTUB2, USP41, MINDY2, YOD1, and PSMD7), is a reliable predictor of survival in breast cancer patients. We found that the high DUBRI group presented higher levels of immune cell infiltration. We performed molecular docking prediction of core target proteins in deubiquitinating enzymes. In vitro experiments verified that knockdown of OTUB2 could inhibit the proliferation and migration of breast cancer., Conclusions: The DUBRI discovered in this research may effectively evaluate the outlook of breast cancer patients and identify groups of patients who would gain advantages from immunotherapy, offering vital knowledge for the future targeted treatment of breast cancer patients.

Background: Deubiquitinating enzymes specifically removes ubiquitin molecules from ubiquitin-tagged target proteins, thereby inhibiting the degradation of target proteins and playing an important role in tumor. However, the mechanism of deubiquitinating enzyme USP45 in tumors remains unclear.Methods: Based on the RNA-seq data of tissues and cell lines in The Cancer Genome Atlas (TCGA) database, GTEx and CCLE database, the pan-cancer analysis of USP45 expression and survival outcome were performed using R software and Kaplan-Meier Plotter. The structural variants, gene mutations and gene copy number alteration of USP45 were analyzed using the TCGA Pan-Cancer Atlas Studies dataset in the cBioPortal database. The relationships between USP45 and mRNA methylation, tumor heterogeneity, tumor stemness, and tumor immunity were performed by Sangerbox platform and TIMER2.0 using Pearson correlation analysis. Through the ENCORI database and string database, we constructed the ceRNA regulatory mechanism and protein-protein interaction network for USP45. Based on the RNA-seq data in TCGA and GTEx databases, we also constructed the downstream regulatory network for USP45 using the Limma and ClusterProfiler packages of R software. At last, the protein expression levels of USP45 were detected by immunohistochemistry in tumor tissue microarrays.Results: USP45 is upregulated in most types of tumors and negatively correlated with the overall survival and recurrence-free survival of patient. Furthermore, the structural variation, gene mutations and gene copy number variation of USP45 were identified in different types of tumors. The pan-cancer analysis showed that USP45 was closely related to mRNA methylation, tumor heterogeneity and tumor stemness. In most types of tumors, the expression of USP45 was positively correlated with many immune checkpoint molecules and immune regulators such as PD-L1, while negatively correlated with the infiltration levels of NK cells, Th1 cells, macrophages, and dendritic cells in the tumor microenvironment. Finally, we constructed the ceRNA regulatory network, protein-protein interaction network and downstream regulatory network for USP45 in different types of tumors.Conclusion: Our study firstly explored the putative oncogenic role of USP45 in pan-cancer, and provided insights for further investigation of USP45.

Deubiquitinating enzymes (DUBs), ~100 of which are found in human cells, are proteases that remove ubiquitin conjugates from proteins, thereby regulating protein turnover. They are involved in a wide range of cellular activities and are emerging therapeutic targets for cancer and other diseases. Drugs targeting USP1 and USP30 are in clinical development for cancer and kidney disease respectively. However, the majority of substrates and pathways regulated by DUBs remain unknown, impeding efforts to prioritize specific enzymes for research and drug development. To assemble a knowledgebase of DUB activities, co-dependent genes, and substrates, we combined targeted experiments using CRISPR libraries and inhibitors with systematic mining of functional genomic databases. Analysis of the Dependency Map, Connectivity Map, Cancer Cell Line Encyclopedia, and multiple protein-protein interaction databases yielded specific hypotheses about DUB function, a subset of which were confirmed in follow-on experiments. The data in this paper are browsable online in a newly developed DUB Portal and promise to improve understanding of DUBs as a family as well as the activities of incompletely characterized DUBs (e.g. USPL1 and USP32) and those already targeted with investigational cancer therapeutics (e.g. USP14, UCHL5, and USP7).

In ovarian cancer patients, the 5-year survival rate is 90% for stages I and II, but only 30% for stages III and IV. Unfortunately, as 75% of the patients are diagnosed at stages III and IV, many experience a recurrence. To ameliorate this, it is necessary to develop new biomarkers for early diagnosis and treatment. The ubiquitin–proteasome system is a post-translational modification that plays an important role in regulating protein stability through ubiquitination. In particular, deubiquitinating enzymes (DUBs) regulate protein stability through deubiquitinating substrate proteins. In this review, DUBs and substrates regulated by these enzymes are summarized based on their functions in ovarian cancer cells. This would be useful for the discovery of biomarkers for ovarian cancer and developing new therapeutic candidates.

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is a chronic inflammatory disorder of the gastrointestinal tract. Although the pathophysiology of IBD is multifaceted, ubiquitination, a post-translational modification, has been shown to have essential roles in its pathogenesis and development. Ubiquitin-modifying enzymes (UMEs) work in synergy to orchestrate the optimal ubiquitination of target proteins, thereby maintaining intestinal homeostasis. Genome-wide association studies (GWAS) have identified multiple UME genes as IBD susceptibility loci, implying the importance of UMEs in IBD. Furthermore, accumulative evidence demonstrates that UMEs affect intestinal inflammation by regulating various aspects, such as intestinal barrier functions and immune responses. Considering the significant functions of UMEs in IBD, targeting UMEs could become a favorable therapeutic approach for IBD. The disease course of IBD is critically regulated by the post-translational modification, ubiquitination, which is orchestrated by UMEs, including E1, E2, and E3 ubiquitinating enzymes, as well as deubiquitinating enzymes. Genetic variants in multiple UMEs, such as A20, have been linked with IBD susceptibility. Functionally, UMEs influence IBD by affecting intestinal barrier function as well as innate and adaptive immune responses. Elucidation of the biological functions of UMEs, identification of their substate proteins, and clarification of the type of ubiquitination are a major focus in UME research. Advances in protein biochemistry have paved the way to develop drugs therapeutically degrading proteins contributing to IBD by ubiquitin-mediated proteolysis. [ABSTRACT FROM AUTHOR]

• T. gondii ubiquitin system mirrors eukaryotic mechanisms. • Potential novel T. gondii drug targets in ubiquitin pathway. • DUBs regulate T. gondii cell cycle and replication. • UBLs crucial for T. gondii survival and pathogenicity. Toxoplasmosis, a zoonotic parasitic disease caused by Toxoplasma gondii (T. gondii), is prevalent worldwide. The fact should be emphasized that a considerable proportion of individuals infected with T. gondii may remain asymptomatic; nevertheless, the condition can have severe implications for pregnant women or immunocompromised individuals. The current treatment of toxoplasmosis primarily relies on medication; however, traditional anti-toxoplasmosis drugs exhibit significant limitations in terms of efficacy, side effects, and drug resistance. The life cycles of T. gondii are characterized by distinct stages and its body morphology goes through dynamic alterations during the growth cycle that are intricately governed by a wide array of post-translational modifications (PTMs). Ubiquitin (Ub) signaling and ubiquitin-like (Ubl) signaling are two crucial post-translational modification pathways within cells, regulating protein function, localization, stability, or interactions by attaching Ub or ubiquitin-like proteins (Ubls) to target proteins. While these signaling mechanisms share some functional similarities, they have distinct regulatory mechanisms and effects. T. gondii possesses both Ub and Ubls and plays a significant role in regulating the parasite's life cycle and maintaining its morphology through PTMs of substrate proteins. Investigating the role and mechanism of protein ubiquitination in T. gondii will provide valuable insights for preventing and treating toxoplasmosis. This review explores the distinctive characteristics of Ub and Ubl signaling in T. gondii , with the aim of inspiring research ideas for the identification of safer and more effective drug targets against toxoplasmosis. [ABSTRACT FROM AUTHOR]

Cyld is a tumor suppressor gene that has attracted particular interest recently, due to its involvement in many types of neo-plasia, including head and neck squamous cell carcinoma, multiple myeloma, melanoma, hepatocellular carcinoma and colon cancer. Cyld encodes a predominantly cytoplasmic protein (CYLD), which is a deubiquitinating enzyme that regulates primarily cell survival and cell division pathways. Studies on the molecular function of CYLD have shown that it can modulate NF-κΒ, JNK, p38, TGF-beta, Wnt and Notch signaling. The present study aimed to investigate whether CYLD expression can be correlated with the development of clear cell renal cell carcinoma (ccRCC). Towards this goal, immunohistochemistry and Real Time PCR experiments were performed in order to analyze CYLD expression in clear cell renal cell carcinoma and matched normal tissue specimens. In addition, a clonogenic assay was performed to analyze the effect of CYLD wt and a catalytically inactive mutant CYLD on the growth of human embryonic kidney cells. The results of the present study show that CYLD is downregulated at protein and mRNA level in patients with ccRCC. This is further corroborated by the results of a clonogenic assay, which showed a deubiquitinating activity-dependent growth inhibitory role of CYLD in human embryonic kidney cells. Our results support the notion that CYLD can have a tumor suppressing role, at least in a subset of clear cell renal cell carcinoma, suggesting that it can be incorporated in the future in the development of targeted therapeutic approaches.

Protein ubiquitination, which is catalyzed by ubiquitin-activating enzymes, ubiquitin-conjugating enzymes, and ubiquitin ligases, is a crucial post-translational modification to regulate numerous cellular functions in a spatio–temporal-specific manner. The human genome encodes ~100 deubiquitinating enzymes (DUBs), which antagonistically regulate the ubiquitin system. OTUD1, an ovarian tumor protease (OTU) family DUB, has an N-terminal-disordered alanine-, proline-, glycine-rich region (APGR), a catalytic OTU domain, and a ubiquitin-interacting motif (UIM). OTUD1 preferentially hydrolyzes lysine-63-linked ubiquitin chains in vitro; however, recent studies indicate that OTUD1 cleaves various ubiquitin linkages, and is involved in the regulation of multiple cellular functions. Thus, OTUD1 predominantly functions as a tumor suppressor by targeting p53, SMAD7, PTEN, AKT, IREB2, YAP, MCL1, and AIF. Furthermore, OTUD1 regulates antiviral signaling, innate and acquired immune responses, and cell death pathways. Similar to Nrf2, OTUD1 contains a KEAP1-binding ETGE motif in its APGR and regulates the reactive oxygen species (ROS)-mediated oxidative stress response and cell death. Importantly, in addition to its association with various cancers, including multiple myeloma, OTUD1 is involved in acute graft-versus-host disease and autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, and ulcerative colitis. Thus, OTUD1 is an important DUB as a therapeutic target for a variety of diseases.

Chemoresistance is a major obstacle faced by oesophageal cancer patients and is synonymous with a poor prognosis. MCL1 is a pivotal member of the anti-apoptotic Bcl-2 protein family, which has been found to play an important role in cell survival, proliferation, differentiation and chemoresistance. Thus, it might be an ideal target for treating oesophageal cancer patients. Although it is known that MCL1 is degraded via the ubiquitin-proteasome system, the deubiquitylating enzyme (DUB) responsible for stabilizing MCL1 remains elusive to date. Herein, we demonstrate that Ubiquitin-Specific Protease 20 (USP20) is a novel regulator of the apoptotic signaling pathway. Moreover, USP20 could regulate the deubiquitination of MCL1 to, in turn, regulate its stability. Increased expression of USP20 was correlated with increased levels of MCL1 protein in human patient samples. In addition, depletion of USP20 could increase the polyubiquitination of MCL1, thereby increasing the conversion rate of MCL1 and the sensitivity of cells to chemotherapy. Overall, our findings indicate that the USP20-MCL1 axis might play a key role in the apoptotic signaling pathway. • USP20 is an MCL1 binding protein and accelerates its deubiquitination depends on enzymatic activity. • USP20 is a potential biomarker for predicting chemoresistance. • USP20-MCL1 axis might play a key role in the apoptotic signalling pathway. [ABSTRACT FROM AUTHOR]

Cyld is a tumor suppressor gene that has attracted particular interest recently, due to its involvement in many types of neoplasia, including head and neck squamous cell carcinoma, multiple myeloma, melanoma, hepatocellular carcinoma and colon cancer. Cyld encodes a predominantly cytoplasmic protein (CYLD), which is a deubiquitinating enzyme that regulates primarily cell survival and cell division pathways. Studies on the molecular function of CYLD have shown that it can modulate NF-α, JNK, p38, TGF-β, Wnt and Notch signaling. The present study aimed to investigate whether CYLD expression can be correlated with the development of clear cell renal cell carcinoma (ccRCC). Towards this goal, immunohistochemistry and Real Time PCR experiments were performed in order to analyze CYLD expression in clear cell renal cell carcinoma and matched normal tissue specimens. In addition, a clonogenic assay was performed to analyze the effect of CYLD wt and a catalytically inactive mutant CYLD on the growth of human embryonic kidney cells. The results of the present study show that CYLD is downregulated at protein and mRNA level in patients with ccRCC. This is further corroborated by the results of a clonogenic assay, which showed a deubiquitinating activity-dependent growth inhibitory role of CYLD in human embryonic kidney cells. Our results support the notion that CYLD can have a tumor suppressing role, at least in a subset of clear cell renal cell carcinoma, suggesting that it can be incorporated in the future in the development of targeted therapeutic approaches. [ABSTRACT FROM AUTHOR]

Hepatocellular carcinoma (HCC) has emerged as one of the most prevalent life‐threatening cancers, and the high mortality rate is largely due to the metastasis. The sustained activation of Smad4 and transforming growth factor‐β (TGF‐β) is closely associated with advanced HCC metastasis. However, the regulatory mechanism underlying the aberrant activation of Smad4 and TGF‐β pathway remains elusive. In this study, using a functional screen of USPs siRNA library, we identified ubiquitin‐specific proteases USP10 as a deubiquitinating enzyme (DUB) that sustains the protein level of Smad4 and activates TGF‐β signaling. Further analysis showed that USP10 directly interacts with Smad4 and stabilizes it through the cleavage of its proteolytic ubiquitination, thus promoting HCC metastasis. The suppression of USP10 by either shRNAs or catalytic inhibitor Spautin‐1 significantly inhibited the migration of HCC cells, whereas the reconstitution of Smad4 was able to efficiently rescue this defect. Overall, our study not only uncovers the regulatory effect of USP10 on the protein abundance of Smad4, but also indicates that USP10 could be regarded as a potential intervention target for the metastatic HCC in Smad4‐positive patients.

Abstract Autophagy is a major degradation pathway that utilizes lysosome hydrolases to degrade cellular constituents and is often induced under cellular stress conditions to restore cell homeostasis. Another prime degradation pathway in the cells is ubiquitin-proteasome system (UPS), in which proteins tagged by certain types of polyubiquitin chains are selectively recognized and removed by proteasome. Although the two degradation pathways are operated independently with different sets of players, recent studies have revealed reciprocal cross talks between UPS and autophagy at multiple layers. In this review, we summarize the roles of protein ubiquitination and deubiquitination in controlling the initiation, execution, and termination of bulk autophagy as well as the role of ubiquitination in signaling certain types of selective autophagy. We also highlight how dysregulation of ubiquitin-mediated autophagy pathways is associated with a number of human diseases and the potential of targeting these pathways for disease intervention.

Med1 binds to a nuclear receptor and regulates transcription. Elevated Med1 protein expression promotes cancer growth in hormone-dependent breast and prostate cancers. Med1 protein expression was investigated by deubiquitinating enzymes (DUBs) overexpression in breast cancer cell lines. Various DNA constructs of SRT-DUBs were overexpressed in the MCF7 cell line, and Med1 protein expression was investigated by western blotting. The cell growth and in vitro invasion assay were performed in BRCA1-associated protein 1 (BAP1) wild type and mutant (C91A) overexpressed cells. Ubiquitination of the Med1 protein was observed, and Med1 protein expression and transcriptional activity were verified by various DUBs overexpressed. Although Med1 protein expression increased upon the overexpression of BAP1, it was not affected by the overexpression of BAP1 mutant (C91A). BAP1 was increased by the E2 treatment, which has an important effect on the breast cancer growth, and cell growth was decreased by BAP1 C91A overexpression. However, metastatic capacities were decreased by BAP1. In addition, the binding between the Med1 and the BAP1 protein was observed. These data suggested that BAP1 regulated Med1 protein expression in breast cancer cells and involved in cancer cell growth and metastasis by binding to Med1 protein., Competing Interests: No potential conflict of interest was reported by the author(s)., (© 2024 The Author(s). Published with license by Taylor & Francis Group, LLC.)

The deubiquitinating enzyme USP1 contains highly conserved motifs forming its catalytic center. Recently, the COSMIC mutation database identified a mutation in USP1 at Asp‐199 in endometrial cancer. Here, we investigated the role of Asp‐199 for USP1 function. The mutation of aspartic acid to alanine (D199A) resulted in failure of USP1 to undergo autocleavage and form a complex with ubiquitin, indicating D199A Usp1 is catalytically inactive. The D199A mutation did not affect the interaction with Uaf1. Moreover, D199A Usp1 had defects in deubiquitination of FANCD2 and PCNA and displayed reduced FANCD2 foci formation and DNA repair efficiency. Furthermore, mutation of Asp‐199 to glutamic acid resulted in phenotypes similar to the D199A mutation. Collectively, our findings demonstrate the importance of Asp‐199 for USP1 activity and suggest the implications of USP1 downregulation in cancer. [ABSTRACT FROM AUTHOR]

Ubiquitination plays an important role in human immunodeficiency virus 1 (HIV-1) infection. HIV proteins such as Vif and Vpx mediate the degradation of the host proteins APOBEC3 and SAMHD1, respectively, through the proteasome pathway. However, whether deubiquitylating enzymes play an essential role in HIV-1 infection is largely unknown. Here, we demonstrate that the deubiquitinase USP21 potently inhibits HIV-1 production by indirectly downregulating the expression of HIV-1 transactivator of transcription (Tat), which is essential for transcriptional elongation in HIV-1. USP21 deubiquitylates Tat via its deubiquitinase activity, but a stronger ability to reduce Tat expression than a dominant-negative ubiquitin mutant (Ub-KO) showed that other mechanisms may contribute to USP21-mediated inhibition of Tat. Further investigation showed that USP21 downregulates cyclin T1 mRNA levels by increasing methylation of histone K9 in the promoter of cyclin T1, a subunit of the positive transcription elongation factor b (P-TEFb) that interacts with Tat and transactivation response element (TAR) and is required for transcription stimulation and Tat stability. Moreover, USP21 had no effect on the function of other HIV-1 accessory proteins, including Vif, Vpr, Vpx, and Vpu, indicating that USP21 was specific to Tat. These findings improve our understanding of USP21-mediated functional suppression of HIV-1 production. IMPORTANCE Ubiquitination plays an essential role in viral infection. Deubiquitinating enzymes (DUBs) reverse ubiquitination by cleaving ubiquitins from target proteins, thereby affecting viral infection. The role of the members of the USP family, which comprises the largest subfamily of DUBs, is largely unknown in HIV-1 infection. Here, we screened a series of USP members and found that USP21 inhibits HIV-1 production by specifically targeting Tat but not the other HIV-1 accessory proteins. Further investigations revealed that USP21 reduces Tat expression in two ways. First, USP21 deubiquitinates polyubiquitinated Tat, causing Tat instability, and second, USP21 reduces the mRNA levels of cyclin T1 (CycT1), an important component of P-TEFb, that leads to Tat downregulation. Thus, in this study, we report a novel role of the deubiquitinase, USP21, in HIV-1 infection. USP21 represents a potentially useful target for the development of novel anti-HIV drugs. [ABSTRACT FROM AUTHOR]

Deregulated MYC overexpression and activation contributes to tumor growth and progression. Given the short half-life and unstable nature of the MYC protein, it is not surprising that the oncoprotein is highly regulated via diverse posttranslational mechanisms. Among them, ubiquitination dynamically controls the levels and activity of MYC during normal cell growth and homeostasis, whereas the disturbance of the ubiquitination/deubiquitination balance enables unwanted MYC stabilization and activation. In addition, MYC is also regulated by SUMOylation which crosstalks with the ubiquitination pathway and controls MYC protein stability and activity. In this mini-review, we will summarize current updates regarding MYC ubiquitination and provide perspectives about these MYC regulators as potential therapeutic targets in cancer. [ABSTRACT FROM AUTHOR]

SUMOylation plays a crucial role in regulating diverse cellular processes including ribosome biogenesis. Proteomic analyses and experimental evidence showed that a number of nucleolar proteins involved in ribosome biogenesis are modified by SUMO. However, how these proteins are SUMOylated in cells is less understood. Here, we report that USP36, a nucleolar deubiquitinating enzyme (DUB), promotes nucleolar SUMOylation. Overexpression of USP36 enhances nucleolar SUMOylation, whereas its knockdown or genetic deletion reduces the levels of SUMOylation. USP36 interacts with SUMO2 and Ubc9 and directly mediates SUMOylation in cells and in vitro. We show that USP36 promotes the SUMOylation of the small nucleolar ribonucleoprotein (snoRNP) components Nop58 and Nhp2 in cells and in vitro and their binding to snoRNAs. It also promotes the SUMOylation of snoRNP components Nop56 and DKC1. Functionally, we show that knockdown of USP36 markedly impairs rRNA processing and translation. Thus, USP36 promotes snoRNP group SUMOylation and is critical for ribosome biogenesis and protein translation. SYNOPSIS: The deubiquitinase USP36 also promotes protein SUMOylation and is essential for ribosome biogenesis and protein translation. USP36 promotes nucleolar protein SUMOylation.USP36 is the first identified DUB/SUMO promoting dual function protein.USP36 promotes snoRNA protein group SUMOylation.USP36 is critical for rRNA processing, translation and cell growth. [ABSTRACT FROM AUTHOR]