Positive reciprocal regulation of ubiquitin C-terminal hydrolase L1 and beta-catenin/TCF signaling

Epigenetic Biomarkers and the Wnt/β-Catenin Pathway in Opisthorchis viverrini-associated Cholangiocarcinoma: A Scoping Review on Therapeutic Opportunities

BACKGROUND

Epigenetic modifications, such as DNA methylation and histone modifications, are pivotal in regulating gene expression pathways related to inflammation and cancer. While there is substantial research on epigenetic marks in cholangiocarcinoma (CCA), Opisthorchis viverrini-induced cholangiocarcinoma (Ov-CCA) is overlooked as a neglected tropical disease (NTD) with limited representation in the literature. Considering the distinct etiological agent, pathogenic mechanisms, and pathological manifestations, epigenetic research plays a pivotal role in uncovering markers and potential targets related to the cancer-promoting and morbidity-inducing liver fluke parasite prevalent in the Great Mekong Subregion (GMS). Emerging studies highlight a predominant hypermethylation phenotype in Opisthorchis viverrini (O. viverrini) tumor tissues, underscoring the significance of abnormal DNA methylation and histone modifications in genes and their promoters as reliable targets for Ov-CCA.

PRINCIPAL FINDINGS

Relevant published literature was identified by searching major electronic databases using targeted search queries. This process retrieved a total of 81 peer-reviewed research articles deemed eligible for inclusion, as they partially or fully met the pre-defined selection criteria. These eligible articles underwent a qualitative synthesis and were included in the systematic review. Within these, 11 studies specifically explored Ov-CCA tissues to investigate potential epigenetic biomarkers and therapeutic targets. This subset of 11 articles provided a foundation for exploring the applications of epigenetics-based therapies and biomarkers for Ov-CCA. These articles delved into various epigenetic modifications, including DNA methylation and histone modifications, and examined genes with aberrant epigenetic changes linked to deregulated signalling pathways in Ov-CCA progression.

CONCLUSIONS

This review identified epigenetic changes and Wnt/β-catenin pathway deregulation as key drivers in Ov-CCA pathogenesis. Promoter hypermethylation of specific genes suggests potential diagnostic biomarkers and dysregulation of Wnt/β-catenin-modulating genes contributes to pathway activation in Ov-CCA progression. Reversible epigenetic changes offer opportunities for dynamic disease monitoring and targeted interventions. Therefore, this study underscores the importance of these epigenetic modifications in Ov-CCA development, suggesting novel therapeutic targets within disrupted signalling networks. However, additional validation is crucial for translating these novel insights into clinically applicable strategies, enhancing personalised Ov-CCA management approaches.

Potential roles of UCH family deubiquitinases in tumorigenesis and chemical inhibitors developed against them

Deubiquitinating enzymes (DUBs) are a large group of proteases that reverse ubiquitination process and maintain protein homeostasis. The DUBs have been classified into seven subfamilies according to their primary sequence and structural similarity. As a small subfamily of DUBs, the ubiquitin C-terminal hydrolases (UCHs) subfamily only contains four members including UCHL1, UCHL3, UCHL5, and BRCA1-associated protein-1 (BAP1). Despite sharing the deubiquitinase activity with a similar catalysis mechanism, the UCHs exhibit distinctive biological functions which are mainly determined by their specific subcellular localization and partner substrates. Besides, growing evidence indicates that the UCH enzymes are involved in human malignancies. In this review, the structural information and biological functions of the UCHs are briefly described. Meanwhile, the roles of these enzymes in tumorigenesis and the discovered inhibitors against them are also summarized to give an insight into the cancer therapy with the potential alternative strategy.

The Suppression of Ubiquitin C-Terminal Hydrolase L1 Promotes the Transdifferentiation of Auditory Supporting Cells into Hair Cells by Regulating the mTOR Pathway

In mammals, hearing loss is irreversible due to the lack of the regenerative capacity of the auditory epithelium. However, stem/progenitor cells in mammalian cochleae may be a therapeutic target for hearing regeneration. The ubiquitin proteasome system plays an important role in cochlear development and maintenance. In this study, we investigated the role of ubiquitin C-terminal hydrolase L1 (UCHL1) in the process of the transdifferentiation of auditory supporting cells (SCs) into hair cells (HCs). The expression of UCHL1 gradually decreased as HCs developed and was restricted to inner pillar cells and third-row Deiters' cells between P2 and P7, suggesting that UCHL1-expressing cells are similar to the cells with Lgr5-positive progenitors. UCHL1 expression was decreased even under conditions in which supernumerary HCs were generated with a γ-secretase inhibitor and Wnt agonist. Moreover, the inhibition of UCHL1 by LDN-57444 led to an increase in HC numbers. Mechanistically, LDN-57444 increased mTOR complex 1 activity and allowed SCs to transdifferentiate into HCs. The suppression of UCHL1 induces the transdifferentiation of auditory SCs and progenitors into HCs by regulating the mTOR pathway.

Ubiquitin C‑terminal hydrolase‑L1: A new cancer marker and therapeutic target with dual effects (Review)

Ubiquitin C-terminal hydrolase-L1 (UCH-L1), a member of the lesser-known deubiquitinating enzyme family, has deubiquitinase and ubiquitin (Ub) ligase activity and the role of stabilizing Ub. UCH-L1 was first discovered in the brain and is associated with regulating cell differentiation, proliferation, transcriptional regulation and numerous other biological processes. UCH-L1 is predominantly expressed in the brain and serves a role in tumor promotion or inhibition. There is still controversy about the effect of UCH-L1 dysregulation in cancer and its mechanisms are unknown. Extensive research to investigate the mechanism of UCH-L1 in different types of cancer is key for the future treatment of UCH-L1-associated cancer. The present review details the molecular structure and function of UCH-L1. The role of UCH-L1 in different types of cancer is also summarized and how novel treatment targets provide a theoretical foundation in cancer research is discussed.

New Look of EBV LMP1 Signaling Landscape

Simple Summary

Epstein-Barr Virus (EBV) infection is associated with various lymphomas and carcinomas as well as other diseases in humans. The transmembrane protein LMP1 plays versatile roles in EBV life cycle and pathogenesis, by perturbing, reprograming, and regulating a large range of host cellular mechanisms and functions, which have been increasingly disclosed but not fully understood so far. We summarize recent research progress on LMP1 signaling, including the novel components LIMD1, p62, and LUBAC in LMP1 signalosome and LMP1 novel functions, such as its induction of p62-mediated selective autophagy, regulation of metabolism, induction of extracellular vehicles, and activation of NRF2-mediated antioxidative defense. A comprehensive understanding of LMP1 signal transduction and functions may allow us to leverage these LMP1-regulated cellular mechanisms for clinical purposes.

Abstract

The Epstein–Barr Virus (EBV) principal oncoprotein Latent Membrane Protein 1 (LMP1) is a member of the Tumor Necrosis Factor Receptor (TNFR) superfamily with constitutive activity. LMP1 shares many features with Pathogen Recognition Receptors (PRRs), including the use of TRAFs, adaptors, and kinase cascades, for signal transduction leading to the activation of NFκB, AP1, and Akt, as well as a subset of IRFs and likely the master antioxidative transcription factor NRF2, which we have gradually added to the list. In recent years, we have discovered the Linear UBiquitin Assembly Complex (LUBAC), the adaptor protein LIMD1, and the ubiquitin sensor and signaling hub p62, as novel components of LMP1 signalosome. Functionally, LMP1 is a pleiotropic factor that reprograms, balances, and perturbs a large spectrum of cellular mechanisms, including the ubiquitin machinery, metabolism, epigenetics, DNA damage response, extracellular vehicles, immune defenses, and telomere elongation, to promote oncogenic transformation, cell proliferation and survival, anchorage-independent cell growth, angiogenesis, and metastasis and invasion, as well as the development of the tumor microenvironment. We have recently shown that LMP1 induces p62-mediated selective autophagy in EBV latency, at least by contributing to the induction of p62 expression, and Reactive Oxygen Species (ROS) production. We have also been collecting evidence supporting the hypothesis that LMP1 activates the Keap1-NRF2 pathway, which serves as the key antioxidative defense mechanism. Last but not least, our preliminary data shows that LMP1 is associated with the deregulation of cGAS-STING DNA sensing pathway in EBV latency. A comprehensive understanding of the LMP1 signaling landscape is essential for identifying potential targets for the development of novel strategies towards targeted therapeutic applications.

Ubiquitin C-terminal hydrolase L1 promotes expression of programmed cell death-ligand 1 in non-small-cell lung cancer cells

Programmed cell death‐ligand 1 (PD‐L1) expressed on cancer cells can cause immune escape of non‐small‐cell lung cancer (NSCLC). Elucidation of the regulatory mechanisms of the PD‐L1 expression is a prerequisite for establishing new tumor immunotherapy strategies. Ubiquitin C‐terminal hydrolase L1 (UCHL1) is a regulator of cellular signaling transduction that is aberrantly expressed in NSCLC. However, it is not known whether UCHL1 regulates the expression of PD‐L1 in NSCLC cells. In the present study, we found that UCHL1 promotes the expression of PD‐L1 in NSCLC cell lines. In addition, UCHL1 expressed in NSCLC cells inhibited activation of Jurkat cells through upregulation of PD‐L1 expression in in vitro experiments. Moreover, UCHL1 upregulates PD‐L1 expression through facilitating activation of the AKT‐P65 signaling pathway. In conclusion, these results indicated that UCHL1 promoted PD‐L1 expression in NSCLC cells. This finding implied that inhibition of UCHL1 might suppress immune escape of NSCLC through downregulation of PD‐L1 expression in NSCLC cells.

Ubiquitin carboxyl-terminal hydrolase L1 promotes hypoxia-inducible factor 1-dependent tumor cell malignancy in spheroid models

Hypoxia-inducible factor 1 (HIF-1) is a critical heterodimeric transcription factor for tumor malignancy. Recently, ubiquitin carboxyl-terminal hydrolase L1 (UCHL1) has been reported to function as a deubiquitinating enzyme for the stabilization of its α subunit (HIF-1α). In the present study, we showed that UCHL1 inhibition can be an effective therapeutic strategy against HIF-1-dependent tumor malignancy. In 2D monolayer culture, a UCHL1 inhibitor suppressed HIF activity and decreased the transcription of HIF downstream genes by inhibiting the UCHL1-mediated accumulation of HIF-1α. Phenotypically, UCHL1 inhibition remarkably blocked cell migration. In 3D spheroid culture models, ectopic expression of UCHL1 significantly upregulated malignancy-related factors such as solidity, volume, as well as viable cell number in an HIF-1α-dependent manner. Conversely, inhibition of the UCHL1-HIF-1 pathway downregulated these malignancy-related factors and also abolished UCHL1-mediated cell proliferation and invasiveness. Finally, inhibition of UCHL1 promoted HIF-1α degradation and lowered the expression of HIF-1 target genes in the 3D model, as also observed in 2D monolayer culture. Our research indicates that the UCHL1-HIF-1 pathway plays a crucial role in tumor malignancy, making it a promising therapeutic target for cancer chemotherapy.

Inhibition of UCH-L1 Deubiquitinating Activity with Two Forms of LDN-57444 Has Anti-Invasive Effects in Metastatic Carcinoma Cells

Normally ubiquitin C-terminal hydrolase L1 (UCH-L1) is expressed in the central nervous and reproductive systems of adults, but its de novo expression has been detected in many human cancers. There is a growing body of evidence that UCH-L1 de-ubiquitinating (DUB) activity plays a major pro-metastatic role in certain carcinomas. Here we tested anti-metastatic effects of the small-molecule inhibitor of UCH-L1 DUB activity, LDN-57444, in cell lines from advanced oral squamous cell carcinoma (OSCC) as well as invasive nasopharyngeal (NP) cell lines expressing the major pro-metastatic gene product of Epstein–Barr virus (EBV) tumor virus, LMP1. To overcome the limited aqueous solubility of LDN-57444 we developed a nanoparticle formulation of LDN-57444 by incorporation of the compound in polyoxazoline micellear nanoparticles (LDN-POx). LDN-POx nanoparticles were equal in effects as the native compound in vitro. Our results demonstrate that inhibition of UCH-L1 DUB activity with LDN or LDN-POx inhibits secretion of exosomes and reduces levels of the pro-metastatic factor in exosomal fractions. Both forms of UCH-L1 DUB inhibitor suppress motility of metastatic squamous carcinoma cells as well as nasopharyngeal cells expressing EBV pro-metastatic Latent membrane protein 1 (LMP1) in physiological assays. Moreover, treatment with LDN and LDN-POx resulted in reduced levels of pro-metastatic markers, a decrease of carcinoma cell adhesion, as well as inhibition of extra-cellular vesicle (ECV)-mediated transfer of viral invasive factor LMP1. We suggest that soluble inhibitors of UCH-L1 such as LDN-POx offer potential forms of treatment for invasive carcinomas including EBV-positive malignancies.

Downregulated UCHL1 Accelerates Gentamicin-Induced Auditory Cell Death via Autophagy

The clinical use of aminoglycoside antibiotics is partly limited by their ototoxicity. The pathogenesis of aminoglycoside-induced ototoxicity still remains unknown. Here, RNA-sequencing was conducted to identify differentially expressed genes in rat cochlear organotypic cultures treated with gentamicin (GM), and 232 and 43 genes were commonly up- and downregulated, respectively, at day 1 and 2 after exposure. Ubiquitin carboxyl-terminal hydrolase isozyme L1 (Uchl1) was one of the downregulated genes whose expression was prominent in spiral ganglion cells (SGCs), lateral walls, as well as efferent nerve terminal and nerve fibers. We further investigated if a deficit of Uchl1 in organotypic cochlea and the House Ear Institute-Organ of Corti 1 (HEI-OC1) cells accelerates ototoxicity. We found that a deficit in Uchl1 accelerated GM-induced ototoxicity by showing a decreased number of SGCs and nerve fibers in organotypic cochlear cultures and HEI-OC1 cells. Furthermore, Uchl1-depleted HEI-OC1 cells revealed an increased number of autophagosomes accompanied by decreased lysosomal fusion. These data indicate that the downregulation of Uchl1 following GM treatment is deleterious to auditory cell survival, which results from the impaired autophagic flux. Our results provide evidence that UCHL1-dependent autophagic flux may have a potential as an otoprotective target for the treatment of GM-induced auditory cell death.

Ubiquitin carboxyl-terminal hydrolases: involvement in cancer progression and clinical implications

Protein ubiquitination and deubiquitination participate in a number of biological processes, including cell growth, differentiation, transcriptional regulation, and oncogenesis. Ubiquitin C-terminal hydrolases (UCHs), a subfamily of deubiquitinating enzymes (DUBs), includes four members: UCH-L1/PGP9.5 (protein gene product 9.5), UCH-L3, UCHL5/UCH37, and BRCA1-associated protein-1 (BAP1). Recently, more attention has been paid to the relationship between the UCH family and malignancies, which play different roles in the progression of different tumors. It remains controversial whether UCHL1 is a tumor promoter or suppressor. UCHL3 and UCH37 are considered to be tumor promoters, while BAP1 is considered to be a tumor suppressor. Studies have showed that UCH enzymes influence several signaling pathways that play crucial roles in oncogenesis, tumor invasion, and migration. In addition, UCH families are associated with tumor cell sensitivity to therapeutic modalities. Here, we reviewed the roles of UCH enzymes in the development of tumors, highlighting the potential consideration of UCH enzymes as new interesting targets for the development of anticancer drugs.

C-Terminal Farnesylation of UCH-L1 Plays a Role in Transport of Epstein-Barr Virus Primary Oncoprotein LMP1 to Exosomes

Exosomes are small vesicles that cells secrete into the extracellular space, and there is increasing evidence that they have pivotal roles in cell-to-cell communication in malignancy. It is reported also that EBV-associated malignant cells, including those derived from nasopharyngeal carcinoma (NPC) and B-cell lymphoma, secrete exosomes. These EBV-related exosomes may contain viral products such as latent membrane protein 1 (LMP1) and may contribute to cancer progression. The aim of this study was to investigate the mechanism by which those viral products are loaded in exosomes. In this study, we show for the first time that ubiquitin C-terminal hydrolase-L1 (UCH-L1) and its C-terminal farnesylation, a posttranslational lipid modification, contribute to this mechanism. Our results also suggest that inhibition of UCH-L1 farnesylation is a potential therapeutic target against cancer metastasis and invasion.

Increasing evidence shows that exosomes are key regulators in cancer cell-to-cell communication. Several reports on Epstein-Barr virus (EBV)-related malignancies demonstrate that latent membrane protein 1 (LMP1) secreted by exosomes derived from EBV- or LMP1-positive cells can promote cancer progression and metastasis. However, the mechanism by which LMP1 is loaded into exosomes is still poorly understood. Here, we examined whether the process of LMP1 loading into exosomes is linked to the multifunctional molecule of the ubiquitin system—ubiquitin C-terminal hydrolase-L1 (UCH-L1). For the first time, we demonstrate that LMP1 is physically associated with UCH-L1 and that directing of LMP1 to exosomes is mediated by C-terminal farnesylation of UCH-L1. Additionally, we found that the FTI-277 farnesyltransferase inhibitor reduces motility- and anchorage-independent growth of EBV-positive cells in functional assays. On the basis of our results, we conclude that C-terminal farnesylation of UCH-L1 is one of the key mechanisms by which LMP1 is sorted to exosomes. We hypothesize that inhibition of farnesylation with specific small-molecule inhibitors blocks exosome-mediated transfer of prometastatic molecules such as LMP1 during cancer cell-to-cell communications and thereby impedes the process of cancer invasion.

IMPORTANCE Exosomes are small vesicles that cells secrete into the extracellular space, and there is increasing evidence that they have pivotal roles in cell-to-cell communication in malignancy. It is reported also that EBV-associated malignant cells, including those derived from nasopharyngeal carcinoma (NPC) and B-cell lymphoma, secrete exosomes. These EBV-related exosomes may contain viral products such as latent membrane protein 1 (LMP1) and may contribute to cancer progression. The aim of this study was to investigate the mechanism by which those viral products are loaded in exosomes. In this study, we show for the first time that ubiquitin C-terminal hydrolase-L1 (UCH-L1) and its C-terminal farnesylation, a posttranslational lipid modification, contribute to this mechanism. Our results also suggest that inhibition of UCH-L1 farnesylation is a potential therapeutic target against cancer metastasis and invasion.

The role of ubiquitination and deubiquitination in the regulation of cell junctions

Maintenance of cell junctions plays a crucial role in the regulation of cellular functions including cell proliferation, permeability, and cell death. Disruption of cell junctions is implicated in a variety of human disorders, such as inflammatory diseases and cancers. Understanding molecular regulation of cell junctions is important for development of therapeutic strategies for intervention of human diseases. Ubiquitination is an important type of post-translational modification that primarily regulates endogenous protein stability, receptor internalization, enzyme activity, and protein-protein interactions. Ubiquitination is tightly regulated by ubiquitin E3 ligases and can be reversed by deubiquitinating enzymes. Recent studies have been focusing on investigating the effect of protein stability in the regulation of cell-cell junctions. Ubiquitination and degradation of cadherins, claudins, and their interacting proteins are implicated in epithelial and endothelial barrier disruption. Recent studies have revealed that ubiquitination is involved in regulation of Rho GTPases’ biological activities. Taken together these studies, ubiquitination plays a critical role in modulating cell junctions and motility. In this review, we will discuss the effects of ubiquitination and deubiquitination on protein stability and expression of key proteins in the cell-cell junctions, including junction proteins, their interacting proteins, and small Rho GTPases. We provide an overview of protein stability in modulation of epithelial and endothelial barrier integrity and introduce potential future search directions to better understand the effects of ubiquitination on human disorders caused by dysfunction of cell junctions.

Immunoproteasome in the blood plasma of children with acute appendicitis, and its correlation with proteasome and UCHL1 measured by SPR imaging biosensors

The aim of this study was to determinate the immunoproteasome concentration in the blood plasma of children with appendicitis, and its correlation with circulating proteasome and ubiquitin carboxyl-terminal hydrolase L1 (UCHL1). Twenty-seven children with acute appendicitis, managed at the Paediatric Surgery Department, were included randomly into the study (age 2 years 9 months up to 14 years, mean age 9·5 ± 1 years). There were 10 girls and 17 boys; 18 healthy, age-matched subjects, admitted for planned surgeries served as controls. Mean concentrations of immunoproteasome, 20S proteasome and UCHL1 in the blood plasma of children with appendicitis before surgery 24 h and 72 h after the appendectomy were higher than in the control group. The immunoproteasome, 20S proteasome and UCHL1 concentrations in the blood plasma of patients with acute appendicitis were highest before surgery. The immunoproteasome, 20S proteasome and UCHL1 concentration measured 24 and 72 h after the operation decreased slowly over time and still did not reach the normal range (P < 0·05). There was no statistical difference between immunoproteasome, 20S proteasome and UCHL1 concentrations in children operated on laparoscopically and children after classic appendectomy. The immunoproteasome concentration may reflect the metabolic response to acute state inflammation, and the process of gradual ebbing of the inflammation may thus be helpful in the assessment of the efficacy of treatment. The method of operation - classic open appendectomy or laparoscopic appendectomy - does not influence the general trend in immunoproteasome concentration in children with appendicitis.

Single-cell RNA sequencing reveals an altered gene expression pattern as a result of CRISPR/cas9-mediated deletion of Gene 33/Mig6 and chronic exposure to hexavalent chromium in human lung epithelial cells

Gene 33 (Mig6, ERRFI1) is an adaptor protein with multiple cellular functions. We recently reported that depletion of this protein promotes lung epithelial cell transformation induced by hexavalent chromium [Cr(VI)]. However, the early molecular events that mediate this process are not clear. In the present study, we used single-cell RNA sequencing to compare gene expression profiles between BEAS-2B lung epithelial cells chronically exposed to a sublethal dose of Cr(VI) with or without CRISPR/cas9-mediated deletion of Gene 33. Our data reveal 83 differentially expressed genes. The most notable changes are genes associated with cell adhesion, oxidative stresses, protein ubiquitination, epithelial-mesenchymal transition/metastasis, and WNT signaling. Up-regulation of some neuro-specific genes is also evident, particularly ubiquitin carboxyl-terminal hydrolase L1 (UCHL1), a deubiquitinase and potential biomarker for lung cancer. Gene 33 deletion and/or Cr(VI) exposure did not cause discernable changes in cell morphology. However, Gene 33 deletion led to a modest but significant reduction of cells in the G2/M phase of the cell cycle regardless of Cr(VI) exposure. Gene 33 deletion also significantly reduced cell proliferation. Interestingly, Cr(VI) exposure eliminated the difference in cell proliferation between the two genotypes. Gene 33 deletion also significantly elevated cell migration. Our data indicate that combined Gene 33 deletion and chronic Cr(VI) exposure produces a gene expression pattern and a phenotype resemble those of the transformed lung epithelial cells. Given the known association of UCHL1 with lung cancer, we propose that UCHL1 is an important player in the early stage of lung epithelial cell transformation and tumorigenesis.

Ubiquitin carboxyl-terminal esterase L1 (UCHL1) is associated with stem-like cancer cell functions in pediatric high-grade glioma

Pediatric high-grade gliomas represent 8–12% of all primary tumors of the nervous system in children. Five-year survival for these pediatric aggressive tumors is poor (15–35%) indicating the need to develop better treatments for pediatric high-grade gliomas. In this work we used SF188 and SJ-GBM2 cell lines to study the function of the ubiquitin carboxyl-terminal esterase L1 (UCHL1), a deubiquitinase de-regulated in several cancers, in pediatric high-grade gliomas. UCHL1 depletion in SF188 and SJ-GBM2 glioma cells was associated with decreased cell proliferation and invasion, along with a reduced ability to grow in soft agar and to form spheres (i.e. self-renewal measure). A 70% reduction in Wnt signaling was also observed in the SF188 and SJ-GBM2 UCHL1 knockdowns (KDs) using a TCF-dependent TOPflash reporter assay. Transcriptome comparisons of UCHL1 KDs versus vector control identified a list of 306 differentially expressed genes (at least 2-fold change; p <0.05) which included genes known to be involved in cancer like ACTA2, POSTN, LIF, FBXL7, FBXW11, GDF15, HEY2, but also potential novel genes such us IGLL5, ABCA4, AQP3, AQP4, CALB1, and ALK. Bioinformatics gene ontology (GO) analysis of these 306 genes revealed significant enrichment in “signal peptides”, “extracellular matrix”and “secreted proteins” GO Terms. “Angiogenesis and blood vessel development”, “neuron differentiation/development”, cell adhesion”, and “cell migration” also showed significant enrichment in our GO analysis. Top canonical pathways identified by Ingenuity Pathway Analysis (IPA) included “Clathrin-mediated Endocytosis Signaling” (p = 5.14x10^-4), “Virus Entry via Endocytic Pathways” (p = 6.15x 10⁻⁴), and “High Mobility Group-Box 1 (HMGB1) Signaling” (p = 6.15x10^-4). While FGF2, IL1B, TNF and PDGFB were predicted as top upstream regulators (p < 2x10-¹⁶) of the UCHL1 KD-associated transcriptome. Aberrant expression of UCHL1 in pediatric high-grade gliomas may promote cell invasion, transformation, and self-renewal properties, at least in part, by modulating Wnt/Beta catenin activity. UCHL1 might act as an oncogene in glioma within the gene network that imparts stem-like characteristics to these cancer cells.

Overexpression of ubiquitin carboxyl-terminal hydrolase L1 (UCHL1) in serum of children after thermal injury

PURPOSE

The study aims to determinate concentrations of ubiquitin C-terminal hydrolase 1 (UCHL1), which hydrolyzes amino acids from ubiquitin and cleave di-ubiquitins, in serum of children after thermal injury.

PATIENTS/METHODS

42 children scalded by hot water, managed at the Department of Pediatric Surgery, with burns in 4-20% TBSA were included into the study (age 9 months up to 14 years, mean age 2.5±1 years). Blood plasma UCHL1 concentration was assessed in 2-6h, 12-16h, 3d, 5d, and 7d after injury using surface plasmon resonance imaging biosensor. 18 healthy subjects admitted for planned surgeries served as controls.

RESULTS

The UCHL1 concentration in the blood plasma of patients with thermal injuries reached its peak 12-16h after thermal injury and slowly decreased over time, and still did not reach the normal range on the 7th day after thermal injury. Mean concentrations of UCHL1 after thermal injury were above the range measured in controls (0.12ng/ml): 2-6h after injury - 5.59ng/dl, 12-16h after injury - 9.16ng/dl, 3 days after injury - 6.94ng/dl, 5 days after 5.41ng/dl, 7 days after injury - 4.09ng/dl.

CONCLUSIONS

We observed sudden increase in the concentration of UCHL1 2-16h after thermal injury with the slow decrease in the UCHL1 concentration over the time. UCHL1 concentration was proportional to the severity of the burn. Further studies are needed to determine the mechanisms by which UCHL1 contributes to metabolic response following thermal injury.

Pathogenic LRRK2 variants are gain-of-function mutations that enhance LRRK2-mediated repression of β-catenin signaling

BACKGROUND

LRRK2 mutations and risk variants increase susceptibility to inherited and idiopathic Parkinson's disease, while recent studies have identified potential protective variants. This, and the fact that LRRK2 mutation carriers develop symptoms and brain pathology almost indistinguishable from idiopathic Parkinson's disease, has led to enormous interest in this protein. LRRK2 has been implicated in a range of cellular events, but key among them is canonical Wnt signalling, which results in increased levels of transcriptionally active β-catenin. This pathway is critical for the development and survival of the midbrain dopaminergic neurones typically lost in Parkinson's disease.

METHODS

Here we use Lrrk2 knockout mice and fibroblasts to investigate the effect of loss of Lrrk2 on canonical Wnt signalling in vitro and in vivo. Micro-computed tomography was used to study predicted tibial strength, while pulldown assays were employed to measure brain β-catenin levels. A combination of luciferase assays, immunofluorescence and co-immunoprecipitation were performed to measure canonical Wnt activity and investigate the relationship between LRRK2 and β-catenin. TOPflash assays are also used to study the effects of LRRK2 kinase inhibition and pathogenic and protective LRRK2 mutations on Wnt signalling. Data were tested by Analysis of Variance.

RESULTS

Loss of Lrrk2 causes a dose-dependent increase in the levels of transcriptionally active β-catenin in the brain, and alters tibial bone architecture, decreasing the predicted risk of fracture. Lrrk2 knockout cells display increased TOPflash and Axin2 promoter activities, both basally and following Wnt activation. Consistently, over-expressed LRRK2 was found to bind β-catenin and repress TOPflash activation. Some pathogenic LRRK2 mutations and risk variants further suppressed TOPflash, whereas the protective R1398H variant increased Wnt signalling activity. LRRK2 kinase inhibitors affected canonical Wnt signalling differently due to off-targeting; however, specific LRRK2 inhibition reduced canonical Wnt signalling similarly to pathogenic mutations.

CONCLUSIONS

Loss of LRRK2 causes increased canonical Wnt activity in vitro and in vivo. In agreement, over-expressed LRRK2 binds and represses β-catenin, suggesting LRRK2 may act as part of the β-catenin destruction complex. Since some pathogenic LRRK2 mutations enhance this effect while the protective R1398H variant relieves it, our data strengthen the notion that decreased canonical Wnt activity is central to Parkinson's disease pathogenesis.

TGF-β1 induces PGP9.5 expression in CAFs to promote the growth of colorectal cancer cells

Numerous studies indicate that the interaction between cancer-associated fibroblasts (CAFs) and tumors is manifested in the entire process of colorectal cancer (CRC) cell development, in which TGF-β1 plays a key role and has a significant effect on promoting the activation of CAFs. However, there are few studies on the mechanisms involved in the activation of CAFs by TGF-β1 to produce an influence on tumor cells. TGF-β1 was added to CAFs for further culture, and the expression of α-SMA was significantly enhanced as shown by immunofluorescence assay. Western blot analysis was performed, and the results showed that TGF-β1 promoted expression of PGP9.5 in a time-dependent manner. After siRNA was used to inhibit the expression of Smad2 or Smad3, the TGF-β1-induced PGP9.5 expression in CAFs was obviously suppressed. In addition, TGF-β1 was also found to promote the expression of PGP9.5 through the ERK1/2 and PI3K pathways. CAFs were cultured on the upper layer of a Transwell plate and TGF-β1 was added. Simultaneously, CRC cells were cultured on the lower layer. The biological behaviors of the cancer cells were detected. According to the results, TGF-β1 promoted the proliferation and invasion of CRC cells and inhibited their apoptosis while activating CAFs. This effect was achieved by induction of the expression of PGP9.5. However, when PGP9.5 was inhibited, the impact of TGF-β1 on tumor cells after activation of CAFs was not fully blocked. Therefore, TGF-β1 can promote PGP9.5 expression in CAFs to facilitate the growth of cancer cells. This finding aids in the identification of new targets for treating CRC.

UCHL1 is a biomarker of aggressive multiple myeloma required for disease progression

The success of proteasome inhibition in multiple myeloma highlights the critical role for the ubiquitin-proteasome system (UPS) in this disease. However, there has been little progress in finding more specific targets within the UPS involved in myeloma pathogenesis. We previously found the ubiquitin hydrolase UCH-L1 to be frequently over-expressed in B-cell malignancies, including myeloma, and showed it to be a potent oncogene in mice. Here we show that UCH-L1 is a poor prognostic factor that is essential for the progression of myeloma. We found high levels of UCHL1 to predict early progression in newly diagnosed patients; a finding reversed by the inclusion of bortezomib. We also found high UCHL1 levels to be a critical factor in the superiority of bortezomib over high-dose dexamethasone in relapsed patients. High UCHL1 partially overlaps with, but is distinct from, known genetic risks including 4p16 rearrangement and 1q21 amplification. Using an orthotopic mouse model, we found UCH-L1 depletion delays myeloma dissemination and causes regression of established disease. We conclude that UCH-L1 is a biomarker of aggressive myeloma that may be an important marker of bortezomib response, and may itself be an effective target in disseminated disease.

Wnt/β-Catenin Signaling Mediated-UCH-L1 Expression in Podocytes of Diabetic Nephropathy

Increasing studies identified podocyte injury as a key early risk factor resulting in diabetic nephropathy (DN). The ubiquitin carboxy-terminal hydrolase 1 (UCH-L1) participates in podocyte differentiation and injury, which is elevated in the podocytes of a variety of nephritis. Whether UCH-L1 expression is positively related to podocyte injury of DN remains unclear. In this study, elevated expression of UCH-L1 and its intrinsic mechanism in high glucose (HG)-stimulated murine podocytes were investigated using western blot and real-time quantitative PCR. Kidney biopsies of DN patients and health individuals were stained by immunofluorescence (IF) method. The morphological and functional changes of podocytes were tested by F-actin staining and cell migration assay. Results demonstrated that HG induced upregulation of UCH-L1 and activation of the Wnt/β-catenin signaling pathway in podocytes. However, blocking of the Wnt pathway by dickkopf related protein 1 (DKK1) eliminated the above changes. Furthermore, IF staining confirmed that, compared with healthy individuals, the expression of UCH-L1 and β-catenin were obviously increased in kidney biopsy of DN patients. Overexpression of UCH-L1 remodeled its actin cytoskeleton, increased its cell migration and impacted its important proteins. All the findings manifested that Wnt/β-catenin/UCH-L1 may be a new potential therapy method in the treatment of DN in future.

UCH-L1 in DLBCL: marker or target?

In this issue of Blood, Bedekovics et al have demonstrated that a multifunctional molecule of the ubiquitin system ubiquitin C-terminal hydrolase L1 (UCH-L1) is induced in diffuse large B-cell lymphomas (DLBCLs), and that levels of this molecule are higher in germinal center (GC) B-cell DLBCL (GCB-DLBCL) compared with activated B-cell DLBCL (ABC-DLBCL) and predict poor outcomes.

Ubiquitin C-terminal hydrolase 1: A novel functional marker for liver myofibroblasts and a therapeutic target in chronic liver disease

BACKGROUND & AIMS

Ubiquitination is a reversible protein modification involved in the major cellular processes that define cell phenotype and behaviour. Ubiquitin modifications are removed by a large family of proteases named deubiquitinases. The role of deubiquitinases in hepatic stellate cell (HSC) activation and their contribution to fibrogenesis are poorly defined. We have identified that the deubiquitinase ubiquitin C-terminal hydrolase 1 (UCHL1) is highly induced following HSC activation, determined its function in activated HSC and its potential as a therapeutic target for fibrosis.

METHODS

Deubiquitinase expression was determined in day 0 and day 10 HSC. Increased UCHL1 expression was confirmed in human HSC and in an alcoholic liver disease (ALD) patient liver. The importance of UCHL1 in hepatic fibrosis was investigated in CCl4 and bile duct ligation injured mice using a pharmacological inhibitor (LDN 57444). The effects of UCHL1 inhibition on HSC proliferation were confirmed by Western blot and 3H thymidine incorporation.

RESULTS

Here we report that pharmacological inhibition of UCHL1 blocks progression of established fibrosis in CCl4 injured mice. UCHL1 siRNA knockdown, LDN 57444 treatment, or HSC isolated from UCHL1(-/-) mice show attenuated proliferation in response to the mitogen, platelet-derived growth factor. Additionally, we observed changes in the phosphorylation of the cell cycle regulator retinoblastoma protein (Rb) in the absence of UCHL1 highlighting a potential mechanism for the reduced proliferative response.

CONCLUSIONS

UCHL1 expression is highly upregulated upon HSC activation and is involved in the regulation of HSC proliferation. This study highlights therapeutic opportunities for pharmacological targeting of UCHL1 in chronic liver disease.

UCH-LI acts as a novel prognostic biomarker in gastric cardiac adenocarcinoma

Gastric cardiac adenocarcinoma (GCA) accounts for a majority of gastric cancer population and harbors unfavorable outcome. Ubiquitin C-terminal hydrolase L1 (UCH-L1) belongs to the deubiquitinating enzyme family, which could regulate cell growth in human cancers. In the present study, expression of UCH-L1 was evaluated in 196 GCAs by immunohistochemistry using tissue microarray and its function on gastric cancer cells was measured. UCH-L1 expression was increased in GCA specimens, compared with their normal tissues and UCH-L1 overexpression is tightly correlated with tumor size and overall TNM stage. Log-rank analysis showed that UCH-L1 positive is reversely associated with cumulative survival (P<0.001). Multivariate Cox regression model showed that UCH-L1 overexpression is a remarkably negative predictor in GCA prognosis (Hazard Ratio=0.53, P<0.01), along with advanced TNM stage that is a known negative factor in gastric cancers (Hazard Ratio=0.33, P<0.05). Silencing of UCH-L1 reduced the ability of cell proliferation, colony formation, migration and invasion of gastric cancer cells. Our findings suggest that UCH-L1 is a promising prognostic biomarker for GCAs and might play an important role in the carcinogenesis of gastric cancer.

Ubiquitin specific protease 4 positively regulates the WNT/β-catenin signaling in colorectal cancer

β-catenin is a key signal transducer in the canonical WNT pathway and is negatively regulated by ubiquitin-dependent proteolysis. Through screening of various deubiquitinating enzymes (DUBs), we identified ubiquitin specific protease 4 (USP4) as a candidate for β-catenin-specific DUB. The effects of USP4 overexpression or knockdown suggested that USP4 positively controls the stability of β-catenin and enhances β-catenin-regulated transcription. Domain mapping results revealed that the C-terminal catalytic domain is responsible for β-catenin binding and nuclear transport. Examination of colon cancer tissues from patients revealed a correlation between elevated expression levels of USP4 and β-catenin. Consistent with this correlation, USP4 knockdown in HCT116, a colon cancer cell line, reduced invasion and migration activity. These observations indicate that USP4 acts as a positive regulator of the WNT/β-catenin pathway by deubiquitination and facilitates nuclear localization of β-catenin. Therefore, we propose that USP4 is a potential target for anti-cancer therapeutics.

Ubiquitin carboxyl terminal hydrolyase L1-suppressed autophagic degradation of p21WAF1/Cip1 as a novel feedback mechanism in the control of cardiac fibroblast proliferation

Aims

Deubiquitinating enzymes (DUBs) appear to be critical regulators of a multitude of processes such as proliferation, apoptosis, differentiation, and inflammation; however, the potential roles of DUBs in the heart remain to be determined. This study was aimed to explore the role of a DUB, ubiquitin carboxyl terminal hydrolyase L1 (UCH-L1) in maladaptive cardiac remodeling and dysfunction.

Methods and Results

Maladaptive cardiac remodeling and dysfunction were induced in mice by transverse aortic constriction (TAC). UCH-L1 expression was transiently increased and then declined near to the basal level while impairment of cardiac function proceeded. The upregulation of UCH-L1 was observed in cardiac myocytes and fibroblasts. In primary culture of cardiac fibroblasts, UCH-L1 was upregulated by platelet-derived growth factor (PDGF)-BB and PDGF-DD. Adenoviral overexpession of UCH-L1 inhibited the PDGF-induced cardiac fibroblast proliferation without affecting the activation of mitogen activated protein kinases (MAPKs), Akt, and signal transducers and activators of transcription 3 (STAT3). Further signaling dissection revealed that PDGF-BB posttranscriptional upregulated p21^WAF1/Cip1 protein expression, which was inhibited by rapamycin, an activator of autophagy via suppressing mammalian target of rapamycin (mTOR), rather than MG132, a proteasome inhibitor. Overexpression of UCH-L1 enhanced PDGF-BB-induced mTOR phosphorylation and upregulation of p21^WAF1/Cip1 protein expression while suppressed autophagic flux in cardiac fibroblasts.

Conclusion

UCH-L1 facilitates PDGF-BB-induced suppression of autophagic degradation of p21^WAF1/Cip1 proteins in cardiac fibroblasts, which may serve as a novel negative feedback mechanism in the control of cardiac fibroblast proliferation contributing to cardiac fibrosis and dysfunction.

Could dysregulation of UPS be a common underlying mechanism for cancer and neurodegeneration? Lessons from UCHL1

Ubiquitin proteasome system (UPS) determines the timing and extent of protein turnover in cells, and it is one of the most strictly controlled cellular mechanisms. Lack of proper control over UPS is attributed to both cancer and to neurodegenerative diseases, yet in different context and direction. Cancerous cells have altered cellular metabolisms, uncontrolled cellular division, and increased proteasome activity. The specialized function prevent neurons from undergoing cellular division but allow them to extend an axon over long distances, establish connections, and to form stable neuronal circuitries. Neurons heavily depend on the proper function of the proteasome and the UPS for their proper function. Reduction of UPS function in vulnerable neurons results in protein aggregation, increased ER stress, and cell death. Identification of compounds that selectively block proteasome function in distinct set of malignancies added momentum to drug discovery efforts, and deubiquitinases (DUBs) gained much attention. This review will focus on ubiquitin carboxy-terminal hydrolase L1 (UCHL1), a DUB that is attributed to both cancer and neurodegeneration. The potential of developing effective treatment strategies for two major health problems by controlling the function of UPS opens up new avenues for innovative approaches and therapeutic interventions.

KSHV LANA and EBV LMP1 induce the expression of UCH-L1 following viral transformation

Ubiquitin C-terminal Hydrolase L1 (UCH-L1) has oncogenic properties and is highly expressed during malignancies. We recently documented that Epstein-Barr virus (EBV) infection induces uch-l1 expression. Here we show that Kaposi's Sarcoma-associated herpesvirus (KSHV) infection induced UCH-L1 expression, via cooperation of KSHV Latency-Associated Nuclear Antigen (LANA) and RBP-Jκ and activation of the uch-l1 promoter. UCH-L1 expression was also increased in Primary Effusion Lymphoma (PEL) cells co-infected with KSHV and EBV compared with PEL cells infected only with KSHV, suggesting EBV augments the effect of LANA on uch-l1. EBV latent membrane protein 1 (LMP1) is one of the few EBV products expressed in PEL cells. Results showed that LMP1 was sufficient to induce uch-l1 expression, and co-expression of LMP1 and LANA had an additive effect on uch-l1 expression. These results indicate that viral latency products of both human γ-herpesviruses contribute to uch-l1 expression, which may contribute to the progression of lymphoid malignancies.

Caspase-1 promotes Epstein-Barr virus replication by targeting the large tegument protein deneddylase to the nucleus of productively infected cells

The large tegument proteins of herpesviruses contain N-terminal cysteine proteases with potent ubiquitin and NEDD8-specific deconjugase activities, but the function of the enzymes during virus replication remains largely unknown. Using as model BPLF1, the homologue encoded by Epstein-Barr virus (EBV), we found that induction of the productive virus cycle does not affect the total level of ubiquitin-conjugation but is accompanied by a BPLF1-dependent decrease of NEDD8-adducts and accumulation of free NEDD8. Expression of BPLF1 promotes cullin degradation and the stabilization of cullin-RING ligases (CRLs) substrates in the nucleus, while cytoplasmic CRLs and their substrates are not affected. The inactivation of nuclear CRLs is reversed by the N-terminus of CAND1, which inhibits the binding of BPLF1 to cullins and prevents efficient viral DNA replication. Targeting of the deneddylase activity to the nucleus is dependent on processing of the catalytic N-terminus by caspase-1. Inhibition of caspase-1 severely impairs viral DNA synthesis and the release of infectious virus, pointing a previously unrecognized role of the cellular response to danger signals triggered by EBV reactivation in promoting virus replication.

An Always Correlated gene expression landscape for ovine skeletal muscle, lessons learnt from comparison with an "equivalent" bovine landscape

Background

We have recently described a method for the construction of an informative gene expression correlation landscape for a single tissue, longissimus muscle (LM) of cattle, using a small number (less than a hundred) of diverse samples. Does this approach facilitate interspecies comparison of networks?

Findings

Using gene expression datasets from LM samples from a single postnatal time point for high and low muscling sheep, and from a developmental time course (prenatal to postnatal) for normal sheep and sheep exhibiting the Callipyge muscling phenotype gene expression correlations were calculated across subsets of the data comparable to the bovine analysis. An “Always Correlated” gene expression landscape was constructed by integrating the correlations from the subsets of data and was compared to the equivalent landscape for bovine LM muscle. Whilst at the high level apparently equivalent modules were identified in the two species, at the detailed level overlap between genes in the equivalent modules was limited and generally not significant. Indeed, only 395 genes and 18 edges were in common between the two landscapes.

Conclusions

Since it is unlikely that the equivalent muscles of two closely related species are as different as this analysis suggests, within tissue gene expression correlations appear to be very sensitive to the samples chosen for their construction, compounded by the different platforms used. Thus users need to be very cautious in interpretation of the differences. In future experiments, attention will be required to ensure equivalent experimental designs and use cross-species gene expression platform to enable the identification of true differences between different species.

Ubiquitin C-terminal hydrolase l1 in tumorigenesis

Ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1, aka PGP9.5) is an abundant, neuronal deubiquitinating enzyme that has also been suggested to possess E3 ubiquitin-protein ligase activity and/or stabilize ubiquitin monomers in vivo. Recent evidence implicates dysregulation of UCH-L1 in the pathogenesis and progression of human cancers. Although typically only expressed in neurons, high levels of UCH-L1 have been found in many nonneuronal tumors, including breast, colorectal, and pancreatic carcinomas. UCH-L1 has also been implicated in the regulation of metastasis and cell growth during the progression of nonsmall cell lung carcinoma, colorectal cancer, and lymphoma. Together these studies suggest UCH-L1 has a potent oncogenic role and drives tumor development. Conversely, others have observed promoter methylation-mediated silencing of UCH-L1 in certain tumor subtypes, suggesting a potential tumor suppressor role for UCH-L1. In this paper, we provide an overview of the evidence supporting the involvement of UCH-L1 in tumor development and discuss the potential mechanisms of action of UCH-L1 in oncogenesis.

UCHL1 acts as a colorectal cancer oncogene via activation of the β-catenin/TCF pathway through its deubiquitinating activity

Ubiquitin C-terminal hydrolase-L1 (UCHL1) belongs to the family of deubiquitinating enzymes (DUBs), which is involved in the ubiquitin-dependent proteolytic system. Previously, we have reported that the upregulation of UCHL1 is related to lymph node metastasis in colorectal cancer (CRC). However, its molecular mechanisms remain elusive. In this study, we transfected pcDNA3.1/UCHL1 and the pcDNA3.1/UCHL1-C90S mutant into HCT8 cells. The changes in biological features in these stable transfectants were examined both in vitro and in vivo. Western blot analysis was used to analyze the changes in the β-catenin/T cell factor (TCF) pathway. We demonstrated that UCHL1 re-expression promoted the proliferation, migration and metastasis potential of HCT8 cells both in vitro and in vivo. We also found that UCHL1 could decelerate β-catenin degradation depending on its deubiquitinating activity. The accumulated β-catenin consequently activated the β-catenin/TCF pathway and induced the expression of cyclin D1 and uPA. These observations imply that UCHL1 may contribute to CRC progression by activating the β-catenin/TCF pathway through its deubi-quitinating activity.

Control of BACE1 degradation and APP processing by ubiquitin carboxyl-terminal hydrolase L1

Deposition of amyloid β protein (Aβ) in the brain is the hallmark of Alzheimer's disease (AD) pathogenesis. Beta-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) is the β-secretase in vivo essential for generation of Aβ. Previously we demonstrated that BACE1 is ubiquitinated and the degradation of BACE1 is mediated by the ubiquitin-proteasome pathway (UPP). However the mechanism underlying regulation of BACE1 degradation by UPP remains elusive. Ubiquitin carboxyl-terminal hydrolase L1 (UCHL1) is a deubiquitinating enzyme highly specific to neuron, catalyzing the hydrolysis of ubiquitin conjugates from ubiquitinated substrates. UCHL1 regulates ubiquitin-dependent protein degradation. However, whether UCHL1 is particularly involved in the proteasomal degradation of BACE1 and what is the role of UCHL1 in AD pathogenesis remain elusive. To investigate the effect of UCHL1 on BACE1 degradation, HUCH cells, a UCHL1 stably over-expressed HEK293 cell line, was established. We found that inhibition of UCHL1 significantly increased BACE1 protein level in a time-dependent manner. Half life of BACE1 was reduced in HUCH cells compared with HEK. Over-expression of UCHL1 decreased APP C-terminal fragment C99 and Aβ levels in HUCH cells. Moreover, disruption of Uchl1 gene significantly elevated levels of endogenous BACE1, C99 and Aβ in the Uchl1-null gad mice. These results demonstrated that UCHL1 accelerates BACE1 degradation and affects APP processing and Aβ production. This study suggests that potentiation of UCHL1 might be able to reduce the level of BACE1 and Aβ in brain, which makes it a novel target for AD drug development.

Kaposi's sarcoma-associated herpesvirus latency-associated nuclear antigen and angiogenin interact with common host proteins, including annexin A2, which is essential for survival of latently infected cells

Kaposi's sarcoma-associated herpesvirus (KSHV) infection and latency-associated nuclear antigen (LANA-1) upregulate the multifunctional protein angiogenin (ANG). Our studies demonstrate that silencing ANG or inhibiting its nuclear translocation downregulates KSHV LANA-1 expression and ANG is necessary for KSHV latency, anti-apoptosis and angiogenesis (Sadagopan et al., J. Virol. 83:3342-3364, 2009; Sadagopan et al., J Virol. 85:2666-2685, 2011). Here we show that LANA-1 interacts with ANG and colocalizes in latently infected endothelial telomerase-immortalized human umbilical vein endothelial (TIVE-LTC) cells. Mass spectrometric analyses of TIVE-LTC proteins immunoprecipitated by anti-LANA-1 and ANG antibodies identified 28 common cellular proteins such as ribosomal proteins, structural proteins, tRNA synthetases, metabolic pathway enzymes, chaperons, transcription factors, antioxidants, and ubiquitin proteosome proteins. LANA-1 and ANG interaction with one of the proteins, annexin A2, was validated. Annexin A2 has been shown to play roles in cell proliferation, apoptosis, plasmin generation, exocytosis, endocytosis, and cytoskeleton reorganization. It is also known to associate with glycolytic enzyme 3-phosphoglyceratekinase in the primer recognition protein (PRP) complex that interacts with DNA polymerase α in the lagging strand of DNA during replication. A higher level of annexin A2 is expressed in KSHV+ but not in Epstein-Barr virus (EBV)+ B-lymphoma cell lines. Annexin A2 colocalized with several LANA-1 punctate spots in KSHV+ body cavity B-cell lymphoma (BCBL-1) cells. In triple-staining analyses, we observed annexin A2-ANG-LANA-1, annexin A2-ANG, and ANG-LANA-1 colocalizations. Annexin A2 appeared as punctate nuclear dots in LANA-1-positive TIVE-LTC cells. In LANA-1-negative TIVE-LTC cells, annexin A2 was detected predominately in the cytoplasm, with some nuclear spots, and colocalization with ANG was observed mostly in the cytoplasm. Annexin A2 coimmunoprecipitated with LANA-1 and ANG in TIVE-LTC and BCBL-1 cells and with ANG in 293T cells independent of LANA-1. This suggested that annexin A2 forms a complex with LANA-1 and ANG as well as a separate complex with ANG. Silencing annexin A2 in BCBL-1 cells resulted in significant cell death, downregulation of cell cycle-associated Cdk6 and of cyclin D, E, and A proteins, and downregulation of LANA-1 and ANG expression. No effect was seen in KSHV⁻ lymphoma (BJAB and Ramos) and 293T cells. These studies suggest that LANA-1 association with annexin A2/ANG could be more important than ANG association with annexin A2, and KSHV probably uses annexin A2 to maintain the viability and cell cycle regulation of latently infected cells. Since the identified LANA-1- and ANG-interacting common cellular proteins are hitherto unknown to KSHV and ANG biology, this offers a starting point for further analysis of their roles in KSHV biology, which may lead to identification of potential therapeutic targets to control KSHV latency and associated malignancies.

Ubiquitin carboxyl-terminal hydrolase 1 (UCHL1) is a potential tumour suppressor in prostate cancer and is frequently silenced by promoter methylation

Background

We have previously reported significant downregulation of ubiquitin carboxyl-terminal hydrolase 1 (UCHL1) in prostate cancer (PCa) compared to the surrounding benign tissue. UCHL1 plays an important role in ubiquitin system and different cellular processes such as cell proliferation and differentiation. We now show that the underlying mechanism of UCHL1 downregulation in PCa is linked to its promoter hypermethylation. Furthermore, we present evidences that UCHL1 expression can affect the behavior of prostate cancer cells in different ways.

Results

Methylation specific PCR analysis results showed a highly methylated promoter region for UCHL1 in 90% (18/20) of tumor tissue compared to 15% (3/20) of normal tissues from PCa patients. Pyrosequencing results confirmed a mean methylation of 41.4% in PCa whereas only 8.6% in normal tissues. To conduct functional analysis of UCHL1 in PCa, UCHL1 is overexpressed in LNCaP cells whose UCHL1 expression is normally suppressed by promoter methylation and found that UCHL1 has the ability to decrease the rate of cell proliferation and suppresses anchorage-independent growth of these cells. In further analysis, we found evidence that exogenous expression of UCHL1 suppress LNCaP cells growth probably via p53-mediated inhibition of Akt/PKB phosphorylation and also via accumulation of p27kip1 a cyclin dependant kinase inhibitor of cell cycle regulating proteins. Notably, we also observed that exogenous expression of UCHL1 induced a senescent phenotype that was detected by using the SA-ß-gal assay and might be due to increased p14ARF, p53, p27kip1 and decreased MDM2.

Conclusion

From these results, we propose that UCHL1 downregulation via promoter hypermethylation plays an important role in various molecular aspects of PCa biology, such as morphological diversification and regulation of proliferation.

PU.1-dependent regulation of UCH L1 expression in B-lymphoma cells

Elevated levels of ubiquitin C-terminal hydrolase L1 (UCH L1) have been detected in a variety of malignancies, and recent studies show the oncogenic capacity of overexpressed UCH L1 in vivo in animal models. Here we demonstrate that expression of endogenous UCH L1 is significantly higher in B-lymphoma cells than in transformed cells of epithelial and fibroblastic origin. The specific hematopoietic transcription factor PU.1 induces UCH L1 expression through direct activation of the uch l1 promoter. Using chromatin immunoprecipitation (ChIP) assays and direct mutagenesis we identified PU.1 binding sites on the uch l1 promoter, at least three of which are involved in this activation. We also show that the viral transcriptional co-activator EBNA2 dramatically increases PU.1-dependent up-regulation of endogenous UCH L1 expression. Finally, inhibition of PU.1 expression with specific shRNA resulted in reduction of UCH L1 mRNA and protein levels in Epstein-Barr virus (EBV)-transformed B-cells. We propose that the ubiquitin-editing enzyme UCH L1 is a multifunctional pro-oncogenic factor involved in development and progression of certain lymphoid malignancies, including EBV-associated lymphomas.

An atlas of altered expression of deubiquitinating enzymes in human cancer

Background

Deubiquitinating enzymes (DUBs) are proteases that process ubiquitin (Ub) or ubiquitin-like gene products, remodel polyubiquitin(-like) chains on target proteins, and counteract protein ubiquitination exerted by E3 ubiquitin-ligases. A wealth of studies has established the relevance of DUBs to the control of physiological processes whose subversion is known to cause cellular transformation, including cell cycle progression, DNA repair, endocytosis and signal transduction. Altered expression of DUBs might, therefore, subvert both the proteolytic and signaling functions of the Ub system.

Methodology/Principal Findings

In this study, we report the first comprehensive screening of DUB dysregulation in human cancers by in situ hybridization on tissue microarrays (ISH-TMA). ISH-TMA has proven to be a reliable methodology to conduct this kind of study, particularly because it allows the precise identification of the cellular origin of the signals. Thus, signals associated with the tumor component can be distinguished from those associated with the tumor microenvironment. Specimens derived from various normal and malignant tumor tissues were analyzed, and the “normal” samples were derived, whenever possible, from the same patients from whom tumors were obtained. Of the ∼90 DUBs encoded by the human genome, 33 were found to be expressed in at least one of the analyzed tissues, of which 22 were altered in cancers. Selected DUBs were subjected to further validation, by analyzing their expression in large cohorts of tumor samples. This analysis unveiled significant correlations between DUB expression and relevant clinical and pathological parameters, which were in some cases indicative of aggressive disease.

Conclusions/Significance

The results presented here demonstrate that DUB dysregulation is a frequent event in cancer, and have implications for therapeutic approaches based on DUB inhibition.

Exploitation of the ubiquitin system by invading bacteria

A variety of bacterial intracellular pathogens target the host cell ubiquitin system during invasion, a process that involves transient but fundamental changes in the actin cytoskeleton and plasma membrane. These changes are induced by bacterial proteins, which can be surface associated, secreted or injected directly into the host cell. Here, the invasion strategies of two extensively studied intracellular bacteria, Salmonella enterica serovar Typhimurium and Listeria monocytogenes, are used to illustrate some of the diverse ways by which bacterial pathogens intersect the host cell ubiquitin pathway.

The A20 deubiquitinase activity negatively regulates LMP1 activation of IRF7

A20 possesses both deubiquitinase (DUB) and ubiquitin E3 ligase activities that are required for termination of Toll-like receptor (TLR) signaling leading to NF-kappaB activation and for blockage of tumor necrosis factor (TNF)-induced cytotoxicity and apoptosis. A20 is induced by the Epstein-Barr virus (EBV) oncoprotein LMP1. However, its dual ubiquitin-editing activities have not been investigated in the context of either EBV infection or IRF7 responses. Both A20 and IRF7 have oncogenic properties. We have recently shown that LMP1 activates IRF7 through K63-linked ubiquitination which requires RIP1 and TRAF6, but how this ubiquitination event is regulated has not been studied. Here, we show that A20 negatively regulates IRF7 transcriptional activity induced by LMP1. Deletion or mutation of A20 C-terminal zinc finger motifs had no effect on the inhibition of IRF7 activity, whereas DUB-deficient truncation or point mutation ablated the ability of A20 to inhibit IRF7. Correspondingly, the A20 N-terminal DUB domain, but not the C-terminal E3 ligase domain, interacts physically with IRF7. Transient expression of A20 reduced K63-linked ubiquitination of IRF7 in vivo, but an in vitro deubiquitination assay with purified constituents shows that IRF7 did not act as a substrate for A20 DUB activity. Moreover, A20 interacts with IRF7 endogenously in latently EBV-infected type 3 Raji cells, in which expression of both A20 and IRF7 is constitutively induced by the considerable level of endogenous LMP1. Knockdown of endogenous A20 in Raji cells by expression of A20 short hairpin RNA (shRNA) vectors increases endogenous IRF7 activity and ubiquitination, as well as the protein level of LMP1, a target of IRF7. Thus, A20 negatively regulates LMP1-stimulated IRF7 ubiquitination and activity in EBV latency, and its DUB activity is indispensable for this function. Finally, we discussed the regulation and function of IRFs in EBV latency.

The potential role of ubiquitin c-terminal hydrolases in oncogenesis

Deubiquitinating enzymes (DUBs), capable of removing ubiquitin (Ub) from protein substrates, are involved in numerous biological processes. The ubiquitin C-terminal hydrolases (UCHs) subfamily of DUBs consists of four members: UCH-L1, UCH-L3, UCH37 and BRCA1-associated protein-1 (BAP1). UCH-L1 possesses deubiquitinating activity and dimerization-dependent ubiquitin ligase activity, and functions as a mono-ubiquitin stabilizer; UCH-L3 does both deubiquitinating and deneddylating activity, except dimerization or ligase activity, and unlike UCH-L1, can interact with Lys48-linked Ub dimers to protect it from degradation and in the meanwhile to inhibit its hydrolase activity; UCH37 is responsible for the deubiquitinating activity in the 19S proteasome regulatory complex, and as indicated by the recent study, UCH37 is also associated with the human Ino80 chromatin-remodeling complex (hINO80) in the nucleus and can be activated via transient association of 19S regulatory particle- or proteasome-bound hRpn13 with hINO80; BAP1, binding to the wild-type BRCA1 RING finger domain, is regarded as a tumor suppressor, but for such suppressing activity, as demonstrated otherwise, both deubiquitinating activity and nucleus localization are required. There is growing evidence that UCH enzymes and human malignancies are closely correlated. Previous studies have shown that UCH enzymes play a crucial role in some signalings and cell-cycle regulation. In this review, we provided an insight into the relation between UCH enzymes and oncogenesis.

Ubiquitin editing enzyme UCH L1 and microtubule dynamics: implication in mitosis

Microtubules are essential components of the cytoskeleton and are involved in many aspects of cell responses including cell division, migration, and intracellular signal transduction. Among other factors, post-translational modifications play a significant role in the regulation of microtubule dynamics. Here, we demonstrate that the ubiquitin-editing enzyme UCH L1, abundant expression of which is normally restricted to brain tissue, is also a part of the microtubule network in a variety of transformed cells. Moreover, during mitosis, endogenous UCH L1 is expressed and tightly associated with the mitotic spindle through all stages of M phase, suggesting that UCH L1 is involved in regulation of microtubule dynamics. Indeed, addition of recombinant UCH L1 to the reaction of tubulin polymerization in vitro had an inhibitory effect on microtubule formation. Unexpectedly, western blot analysis of tubulin fractions after polymerization revealed the presence of a specific approximately 50 kDa band of UCH L1 (not the normal approximately 25 kDa) in association with microtubules, but not with free tubulin. In addition, we show that along with 25 kDa UCH L1, endogenous high molecular weight UCH L1 complexes exist in cells, and that levels of 50 kDa UCH L1 complexes are increasing in cells during mitosis. Finally, we provide evidence that ubiquitination is involved in tubulin polymerization: the presence of ubiquitin during polymerization in vitro by itself inhibited microtubule formation and enhanced the inhibitory effect of added UCH L1. The inhibitory effects of UCH L1 correlate with an increase in ubiquitination of microtubule components. Since besides being a deubiquitinating enzyme, UCH L1 as a dimer has also been shown to exhibit ubiquitin ligase activity, we discuss the possibility that the approximately 50 kDa UCH L1 observed is a dimer which prevents microtubule formation through ubiquitination of tubulins and/or microtubule-associated proteins.

Emerging roles of deubiquitinases in cancer-associated pathways

Deubiquitinases (DUBs) are emerging as important regulators of many pathways germane to cancer. They may regulate the stability of key oncogenes, exemplified by USP28 stabilisation of c-Myc. Alternatively they can negatively regulate ubiquitin-dependent signalling cascades such as the NF-kappaB activation pathway. We review the current literature that associates DUBs with cancer and discuss their suitability as drug targets of the future.

Ubiquitin carboxyl terminal hydrolase L1 negatively regulates TNFalpha-mediated vascular smooth muscle cell proliferation via suppressing ERK activation

Deubiquitinating enzymes (DUBs) appear to be critical regulators of a multitude of processes such as proliferation, apoptosis, differentiation, and inflammation. We have recently demonstrated that a DUB of ubiquitin carboxyl terminal hydrolase L1 (UCH-L1) inhibits vascular lesion formation via suppressing inflammatory responses in vasculature. However, the precise underlying mechanism remains to be defined. Herein, we report that a posttranscriptional up-regulation of UCH-L1 provides a negative feedback to tumor necrosis factor alpha (TNFalpha)-mediated activation of extracellular signal-regulated kinases (ERK) and proliferation in vascular smooth muscle cells (VSMCs). In rat adult VSMCs, adenoviral over-expression of UCH-L1 inhibited TNFalpha-induced activation of ERK and DNA synthesis. In contrast, over-expression of UCH-L1 did not affect platelet derived growth factor (PDGF)-induced VSMC proliferation and activation of growth stimulating cascades including ERK. TNFalpha hardly altered UCH-L1 mRNA expression and stability; however, up-regulated UCH-L1 protein expression via increasing UCH-L1 translation. These results uncover a novel mechanism by which UCH-L1 suppresses vascular inflammation.

Expression and functional studies of ubiquitin C-terminal hydrolase L1 regulated genes

Deubiquitinating enzymes (DUBs) have been increasingly implicated in regulation of cellular processes, but a functional role for Ubiquitin C-terminal Hydrolases (UCHs), which has been largely relegated to processing of small ubiquitinated peptides, remains unexplored. One member of the UCH family, UCH L1, is expressed in a number of malignancies suggesting that this DUB might be involved in oncogenic processes, and increased expression and activity of UCH L1 have been detected in EBV-immortalized cell lines. Here we present an analysis of genes regulated by UCH L1 shown by microarray profiles obtained from cells in which expression of the gene was inhibited by RNAi. Microarray data were verified with subsequent real-time PCR analysis. We found that inhibition of UCH L1 activates genes that control apoptosis, cell cycle arrest and at the same time suppresses expression of genes involved in proliferation and migration pathways. These findings are complemented by biological assays for apoptosis, cell cycle progression and migration that support the data obtained from microarray analysis, and suggest that the multi-functional molecule UCH L1 plays a role in regulating principal pathways involved in oncogenesis.