Loss of the tumor suppressor CYLD enhances Wnt/beta-catenin signaling through K63-linked ubiquitination of Dvl

The role of ubiquitination in health and disease

Ubiquitination is an enzymatic process characterized by the covalent attachment of ubiquitin to target proteins, thereby modulating their degradation, transportation, and signal transduction. By precisely regulating protein quality and quantity, ubiquitination is essential for maintaining protein homeostasis, DNA repair, cell cycle regulation, and immune responses. Nevertheless, the diversity of ubiquitin enzymes and their extensive involvement in numerous biological processes contribute to the complexity and variety of diseases resulting from their dysregulation. The ubiquitination process relies on a sophisticated enzymatic system, ubiquitin domains, and ubiquitin receptors, which collectively impart versatility to the ubiquitination pathway. The widespread presence of ubiquitin highlights its potential to induce pathological conditions. Ubiquitinated proteins are predominantly degraded through the proteasomal system, which also plays a key role in regulating protein localization and transport, as well as involvement in inflammatory pathways. This review systematically delineates the roles of ubiquitination in maintaining protein homeostasis, DNA repair, genomic stability, cell cycle regulation, cellular proliferation, and immune and inflammatory responses. Furthermore, the mechanisms by which ubiquitination is implicated in various pathologies, alongside current modulators of ubiquitination are discussed. Enhancing our comprehension of ubiquitination aims to provide novel insights into diseases involving ubiquitination and to propose innovative therapeutic strategies for clinical conditions.

CYLD Alterations Are Associated With Metastasis and Poor Prognosis in Human Papilloma Virus-Positive Head and Neck Cancer

BACKGROUND

Human papilloma virus (HPV)-associated head and neck squamous cell carcinoma (HNSCC) is an emerging epidemic and a subset of HPV-positive patients experience aggressive disease with metastases. The CYLD gene is frequently altered in HPV-positive HNSCC, but the role of these alterations in disease progression is poorly understood.

METHODS

We identified 11 HPV-positive HNSCC patients with CYLD alterations and assessed their clinical course. We also characterized a unique, HPV-positive, metastatic, HNSCC patient-derived xenograft (PDX).

RESULTS

All 11 patients developed metastasis with reduced overall survival when compared with metastatic HPV-positive patients with wild-type CYLD. The metastatic PDX harbored a CYLD mutation (S371*) and exhibited reduced expression of connexin 43, a potentially antimetastatic protein. We also investigated the functional impact of the S371* mutation, as well as 2 CYLD mutations from our 11-patient cohort.

CONCLUSION

Our findings indicate that alterations in CYLD in HPV-positive HNSCC are associated with metastasis and poor prognosis.

E3 ligases RNF43 and ZNRF3 display differential specificity for endocytosis of Frizzled receptors

The transmembrane E3 ligases RNF43 and ZNRF3 perform key tumour suppressor roles by inducing endocytosis of members of the Frizzled (FZD) family, the primary receptors for WNT. Loss-of-function mutations in RNF43 and ZNRF3 mediate FZD stabilisation and a WNT-hypersensitive growth state in various cancer types. Strikingly, RNF43 and ZNRF3 mutations are differentially distributed across cancer types, raising questions about their functional redundancy. Here, we compare the efficacy of RNF43 and ZNRF3 of targeting different FZDs for endocytosis. We find that RNF43 preferentially down-regulates FZD1/FZD5/FZD7, whereas ZNRF3 displays a preference towards FZD6. We show that the RNF43 transmembrane domain (TMD) is a key molecular determinant for inducing FZD5 endocytosis. Furthermore, a TMD swap between RNF43 and ZNRF3 re-directs their preference for FZD5 down-regulation. We conclude that RNF43 and ZNRF3 preferentially down-regulate specific FZDs, in part by a TMD-dependent mechanism. In accordance, tissue-specific expression patterns of FZD homologues correlate with the incidence of RNF43 or ZNRF3 cancer mutations in those tissues. Consequently, our data point to druggable vulnerabilities of specific FZD receptors in RNF43- or ZNRF3-mutant human cancers.

Ubiquitin-modifying enzymes in thyroid cancer：Mechanisms and functions

Thyroid cancer is the most common malignant tumor of the endocrine system, and evidence suggests that post-translational modifications (PTMs) and epigenetic alterations play an important role in its development. Recently, there has been increasing evidence linking dysregulation of ubiquitinating enzymes and deubiquitinases with thyroid cancer. This review aims to summarize our current understanding of the role of ubiquitination-modifying enzymes in thyroid cancer, including their regulation of oncogenic pathways and oncogenic proteins. The role of ubiquitination-modifying enzymes in thyroid cancer development and progression requires further study, which will provide new insights into thyroid cancer prevention, treatment and the development of novel agents.

New insights in ubiquitin-dependent Wnt receptor regulation in tumorigenesis

Wnt signaling plays a crucial role in embryonic development and homeostasis maintenance. Delicate and sensitive fine-tuning of Wnt signaling based on the proper timings and positions is required to balance cell proliferation and differentiation and maintain individual health. Therefore, homeostasis is broken by tissue hypoplasia or tumor formation once Wnt signal dysregulation disturbs the balance of cell proliferation. The well-known regulatory mechanism of Wnt signaling is the molecular reaction associated with the cytoplasmic accumulation of effector β-catenin. In addition to β-catenin, most Wnt effector proteins are also regulated by ubiquitin-dependent modification, both qualitatively and quantitatively. This review will explain the regulation of the whole Wnt signal in four regulatory phases, as well as the different ubiquitin ligases and the function of deubiquitinating enzymes in each phase. Along with the recent results, the mechanism by which RNF43 negatively regulates the surface expression of Wnt receptors, which has recently been well understood, will be detailed. Many RNF43 mutations have been identified in pancreatic and gastrointestinal cancers and examined for their functional alteration in Wnt signaling. Several mutations facilitate or activate the Wnt signal, reversing the RNF43 tumor suppressor function into an oncogene. RNF43 may simultaneously play different roles in classical multistep tumorigenesis, as both wild-type and mutant RNF43 suppress the p53 pathway. We hope that the knowledge obtained from further research in RNF43 will be applied to cancer treatment in the future despite the fully unclear function of RNF43.

Propranolol inhibits EMT and metastasis in breast cancer through miR-499-5p-mediated Sox6

PURPOSE

This study will focus on 4T1 cells, a murine mammary adenocarcinoma cell line, as the primary research subject. We aim to investigate the inhibitory effects and mechanisms of propranolol on epithelial-mesenchymal transition (EMT) in breast cancer cells, aiming to elucidate this phenomenon at the miRNA level.

METHODS

In this study, the EMT inhibitory effect of propranolol was observed through in vitro and animal experiments. For the screening of potential target miRNAs and downstream target genes, second-generation sequencing (SGS) and bioinformatics analysis were conducted. Following the screening process, the identified target miRNAs and their respective target genes were confirmed using various experimental methods. To confirm the target miRNAs and target genes, Western Blot (WB), reverse transcription polymerase chain reaction (RT-PCR), and immunofluorescence experiments were performed.

RESULTS

In this study, we found that propranolol significantly reduced lung metastasis in 4T1 murine breast cancer cells (p < 0.05). In vitro and in vivo experiments demonstrated that propranolol inhibited the epithelial-mesenchymal transition (EMT) as evidenced by Western Blot analysis (p < 0.05). Through next-generation sequencing (SGS), subsequent bioinformatics analysis, and PCR validation, we identified a marked downregulation of miR-499-5p (p < 0.05), suggesting its potential involvement in mediating the suppressive effects of propranolol on EMT. Overexpression of miR-499-5p promoted EMT, migration, and invasion of 4T1 cells, and these effects were not reversed or attenuated by propranolol (Validated via Western Blot, wound healing assay, transwell migration, and invasion assays, p < 0.05). Sox6 was identified as a functional target of miR-499-5p, with its downregulation correlating with the observed EMT changes (p < 0.05). Silencing Sox6 or overexpressing miR-499-5p inhibited Sox6 expression, further promoting the processes of EMT, invasion, and migration in 4T1 cells. Notably, these effects were not alleviated by propranolol (validated via Western Blot, wound healing assay, transwell migration, and invasion assays, p < 0.05). The direct interaction between miR-499-5p and Sox6 mRNA was confirmed by dual-luciferase reporter gene assay.

CONCLUSION

These results suggest that propranolol may have potential as a therapeutic agent for breast cancer treatment by targeting EMT and its regulatory mechanisms.

Up-regulated lncRNA CYLD as a ceRNA of miR-2383 facilitates bovine viral diarrhea virus replication by promoting CYLD expression to counteract RIG-I-mediated type-I IFN production

Bovine viral diarrhea virus (BVDV) is one of the most important pathogens of cattle, causing numerous economic losses to the cattle industry. To date, many potential mechanisms of BVDV evading or subverting innate immunity are still unknown. In this study, an lnc-CYLD/miR-2383/CYLD axis involved in BVDV-host interactions was screened from RNA-seq-based co-expression networks analysis of long noncoding RNAs, microRNAs and mRNAs in BVDV-infected bovine cells, and underlying mechanisms of lnc-CYLD/miR-2383/CYLD axis regulating BVDV replication were explored. Results showed that BVDV-induced up-regulation of the lnc-CYLD competed for binding to the miR-2383, and then promoted CYLD expression, thereby inhibiting RIG-I-mediated type-I interferon (IFN) production, which was subsequently confirmed by treatment with lnc-CYLD overexpression and miR-2383 inhibitor. However, miR-2383 transfection and small interfering RNA-mediated lnc-CYLD knockdown inhibited CYLD expression and enhanced RIG-I-mediated type-I IFN production, inhibiting BVDV replication. In addition, interaction relationship between lnc-CYLD and miR-2383, and colocalization relationship of lnc-CYLD, miR-2383 and CYLD were confirmed by dual-luciferase assay and in situ hybridization assay. Conclusively, up-regulation of the lnc-CYLD as a competing endogenous RNA binds to the miR-2383 to reduce inhibitory effect of the miR-2383 on the CYLD expression, playing an important role in counteracting type-I IFN-dependent antiviral immunity to facilitate BVDV replication.

Deubiquitylating Enzymes in Cancer and Immunity

Deubiquitylating enzymes (DUBs) maintain relative homeostasis of the cellular ubiquitome by removing the post-translational modification ubiquitin moiety from substrates. Numerous DUBs have been demonstrated specificity for cleaving a certain type of ubiquitin linkage or positions within ubiquitin chains. Moreover, several DUBs perform functions through specific protein-protein interactions in a catalytically independent manner, which further expands the versatility and complexity of DUBs' functions. Dysregulation of DUBs disrupts the dynamic equilibrium of ubiquitome and causes various diseases, especially cancer and immune disorders. This review summarizes the Janus-faced roles of DUBs in cancer including proteasomal degradation, DNA repair, apoptosis, and tumor metastasis, as well as in immunity involving innate immune receptor signaling and inflammatory and autoimmune disorders. The prospects and challenges for the clinical development of DUB inhibitors are further discussed. The review provides a comprehensive understanding of the multi-faced roles of DUBs in cancer and immunity.

Function, mechanism and drug discovery of ubiquitin and ubiquitin-like modification with multiomics profiling for cancer therapy

Ubiquitin (Ub) and ubiquitin-like (Ubl) pathways are critical post-translational modifications that determine whether functional proteins are degraded or activated/inactivated. To date, >600 associated enzymes have been reported that comprise a hierarchical task network (e.g., E1-E2-E3 cascade enzymatic reaction and deubiquitination) to modulate substrates, including enormous oncoproteins and tumor-suppressive proteins. Several strategies, such as classical biochemical approaches, multiomics, and clinical sample analysis, were combined to elucidate the functional relations between these enzymes and tumors. In this regard, the fundamental advances and follow-on drug discoveries have been crucial in providing vital information concerning contemporary translational efforts to tailor individualized treatment by targeting Ub and Ubl pathways. Correspondingly, emphasizing the current progress of Ub-related pathways as therapeutic targets in cancer is deemed essential. In the present review, we summarize and discuss the functions, clinical significance, and regulatory mechanisms of Ub and Ubl pathways in tumorigenesis as well as the current progress of small-molecular drug discovery. In particular, multiomics analyses were integrated to delineate the complexity of Ub and Ubl modifications for cancer therapy. The present review will provide a focused and up-to-date overview for the researchers to pursue further studies regarding the Ub and Ubl pathways targeted anticancer strategies.

Inactivation of Tumor Suppressor CYLD Inhibits Fibroblast Reprogramming to Pluripotency

CYLD is a tumor suppressor gene coding for a deubiquitinating enzyme that has a critical regulatory function in a variety of signaling pathways and biological processes involved in cancer development and progression, many of which are also key modulators of somatic cell reprogramming. Nevertheless, the potential role of CYLD in this process has not been studied. With the dual aim of investigating the involvement of CYLD in reprogramming and developing a better understanding of the intricate regulatory system governing this process, we reprogrammed control (CYLDWT/WT) and CYLD DUB-deficient (CYLDΔ9/Δ9) mouse embryonic fibroblasts (MEFs) into induced pluripotent stem cells (iPSCs) through ectopic overexpression of the Yamanaka factors (Oct3/4, Sox2, Klf4, c-myc). CYLD DUB deficiency led to significantly reduced reprogramming efficiency and slower early reprogramming kinetics. The introduction of WT CYLD to CYLDΔ9/Δ9 MEFs rescued the phenotype. Nevertheless, CYLD DUB-deficient cells were capable of establishing induced pluripotent colonies with full spontaneous differentiation potential of the three germ layers. Whole proteome analysis (Data are available via ProteomeXchange with identifier PXD044220) revealed that the mesenchymal-to-epithelial transition (MET) during the early reprogramming stages was disrupted in CYLDΔ9/Δ9 MEFs. Interestingly, differentially enriched pathways revealed that the primary processes affected by CYLD DUB deficiency were associated with the organization of the extracellular matrix and several metabolic pathways. Our findings not only establish for the first time CYLD's significance as a regulatory component of early reprogramming but also highlight its role as an extracellular matrix regulator, which has profound implications in cancer research.

AXIN1 bi-allelic variants disrupting the C-terminal DIX domain cause craniometadiaphyseal osteosclerosis with hip dysplasia

Sclerosing skeletal dysplasias result from an imbalance between bone formation and resorption. We identified three homozygous, C-terminally truncating AXIN1 variants in seven individuals from four families affected by macrocephaly, cranial hyperostosis, and vertebral endplate sclerosis. Other frequent findings included hip dysplasia, heart malformations, variable developmental delay, and hematological anomalies. In line with AXIN1 being a central component of the β-catenin destruction complex, analyses of primary and genome-edited cells harboring the truncating variants revealed enhanced basal canonical Wnt pathway activity. All three AXIN1-truncating variants resulted in reduced protein levels and impaired AXIN1 polymerization mediated by its C-terminal DIX domain but partially retained Wnt-inhibitory function upon overexpression. Addition of a tankyrase inhibitor attenuated Wnt overactivity in the AXIN1-mutant model systems. Our data suggest that AXIN1 coordinates the action of osteoblasts and osteoclasts and that tankyrase inhibitors can attenuate the effects of AXIN1 hypomorphic variants.

A Tumor Suppressive Role of CYLD as a Novel Potential DUB of Aurora B in Cervical Cancer

Background

Cervical cancer is a common leading cause of cancer related to women death worldwide. Cylindromatosis (CYLD) is known as an important tumor suppressor in various human cancers, and a deubiquitination enzyme (DUB) as well. Previously, we identified Skp2 as an E3 ligase of Aurora B ubiquitination, but the DUB of Aurora B still remains unknown.

Methods

Aurora B ubiquitination site is identified through in vivo ubiquitination assay. Activity of Aurora B and CENPA was detected by immunoblotting (IB) and immunofluorescence (IF) assay. Protein-to-protein interaction was investigated by immunoprecipitation (IP). Cell chromosome dynamics was monitored by live-cell time-lapse Imaging. Cancer cell proliferation, colony formation, apoptosis, and cell invasion and migration assays were also performed. Protein level was checked by immunohistochemical (IHC) staining in clinical cervical cancer samples.

Results

We identified Lysine 115 (K115) as the main Aurora B ubiquitination site for Skp2. We could also detect an interaction of Aurora B with the DUB CYLD. We found that CYLD promoted deubiquitination of Aurora B, and regulated Aurora B activity and function as well. Compared with control, we found it took more time for the cells to finish cell mitosis with CYLD over-expression. Furthermore, we found that CYLD deficiency promoted cervical cancer cell proliferation, colony formation, cell migration and invasion, and inhibited apoptosis instead, whereas it is just opposite with CYLD over-expression. In clinical cervical cancer samples, we showed a negative correlation of CYLD expression with Aurora B activation and histological cancer cell invasion. Furthermore, there was less CYLD abundance and higher Aurora B activity in advanced cancer samples compared with early stage.

Conclusions

Our findings uncover CYLD as a novel potential DUB of Aurora B, which inhibits Aurora B activation and its subsequent function in cell mitosis, and also provide more evidence for its tumor suppressor function in cervical cancer.

RSPO3 Furin domain-conjugated liposomes for selective drug delivery to LGR5-high cells

The transmembrane receptor LGR5 potentiates Wnt/β-catenin signaling by binding both secreted R-spondin (RSPOs) and the Wnt tumor suppressors RNF43/ZNRF3, directing clearance of RNF43/ZNRF3 from the cell surface. Besides being widely used as a stem cell marker in various tissues, LGR5 is overexpressed in many types of malignancies, including colorectal cancer. Its expression characterizes a subpopulation of cancer cells that play a crucial role in tumor initiation, progression and cancer relapse, known as cancer stem cells (CSCs). For this reason, ongoing efforts are aimed at eradicating LGR5-positive CSCs. Here, we engineered liposomes decorated with different RSPO proteins to specifically detect and target LGR5-positive cells. Using fluorescence-loaded liposomes, we show that conjugation of full-length RSPO1 to the liposomal surface mediates aspecific, LGR5-independent cellular uptake, largely mediated by heparan sulfate proteoglycan binding. By contrast, liposomes decorated only with the Furin (FuFu) domains of RSPO3 are taken up by cells in a highly specific, LGR5-dependent manner. Moreover, encapsulating doxorubicin in FuFuRSPO3 liposomes allowed us to selectively inhibit the growth of LGR5-high cells. Thus, FuFuRSPO3-coated liposomes allow for the selective detection and ablation of LGR5-high cells, providing a potential drug delivery system for LGR5-targeted anti-cancer strategies.

SPATA2 suppresses epithelial-mesenchymal transition to inhibit metastasis and radiotherapy sensitivity in non-small cell lung cancer via impairing DVL1/β-catenin signaling

Metastasis is the major cause of cancer-related death of cancer patients. Epithelial-mesenchymal transition (EMT) is one critical process during the cascade of tumor metastasis. EMT is a developmental program exploited by cancer cells to transition from epithelial state to mesenchymal state and confers metastatic properties as well as treatment resistance. Finding factors to inhibit EMT will greatly improve the prognosis patients. Spermatogenesis associated 2 (SPATA2) was originally isolated from human testis and proved playing a role in spermatogenesis. To date, however, the role of SPATA2 in oncogenesis is unknown. In the current study, by mining the public database and validating in a cohort of collected non-small cell lung cancer (NSCLC) specimens, we uncovered that the expression of SPATA2 positively correlated with the prognosis of patients and was an independent prognosis marker in NSCLC. Functional studies proved that ectopic overexpression of SPATA2 inhibited EMT resulting in impaired motility and invasiveness properties in vitro and metastasis in vivo, and increased radiosensitivity in NSCLC. Mechanistic investigation showed that SPATA2 could suppress the β-catenin signaling via attenuating DVL1 ubiquitination to achieve the functions. Taken together, the current study revealed an inhibitory role of SPATA2 on EMT and that SPATA2 could be a potential target for therapy of NSCLC.

Potential use of EGFR-targeted molecular therapies for tumor suppressor CYLD-negative and poor prognosis oral squamous cell carcinoma with chemoresistance

BACKGROUND

Tumor suppressor CYLD dysfunction by loss of its expression, triggers malignant transformation, especially drug resistance and tumor invasion/metastasis. Although loss of CYLD expression is significantly associated with poor prognosis in a large variety of tumors, no clinically-effective treatment for CYLD-negative cancer patients is available.

METHODS

We focused on oral squamous cell carcinoma (OSCC), and sought to develop novel therapeutic agents for CYLD-negative cancer patients with poor prognosis. CYLD-knockdown OSCC cells by using CYLD-specific siRNA, were used to elucidate and determine the efficacy of novel drug candidates by evaluating cell viability and epithelial-mesenchymal transition (EMT)-like change. Therapeutic effects of candidate drug on cell line-derived xenograft (CDX) model and usefulness of CYLD as a novel biomarker using patient-derived xenograft (PDX) model were further investigated.

RESULTS

CYLD-knockdown OSCC cells were resistant for all currently-available cytotoxic chemotherapeutic agents for OSCC, such as, cisplatin, 5-FU, carboplatin, docetaxel, and paclitaxel. By using comprehensive proteome analysis approach, we identified epidermal growth factor receptor (EGFR), a receptor tyrosine kinase, played key roles in CYLD-knockdown OSCC cells. Indeed, cell survival rate in the cisplatin-resistant CYLD-knockdown OSCC cells was markedly inhibited by treatment with clinically available EGFR tyrosine kinase inhibitors (EGFR-TKIs), such as gefitinib. In addition, gefitinib was significantly effective for not only cell survival, but also EMT-like changes through inhibiting transforming growth factor-β (TGF-β) signaling in CYLD-knockdown OSCC cells. Thereby, overall survival of CYLD-knockdown CDX models was significantly prolonged by gefitinib treatment. Moreover, we found that CYLD expression was significantly associated with gefitinib response by using PDX models.

CONCLUSIONS

Our results first revealed that EGFR-targeted molecular therapies, such as EGFR-TKIs, could have potential to be novel therapeutic agents for the CYLD-negative OSCC patients with poor prognosis.

Role of K63-linked ubiquitination in cancer

Ubiquitination is a critical type of post-translational modifications, of which K63-linked ubiquitination regulates interaction, translocation, and activation of proteins. In recent years, emerging evidence suggest involvement of K63-linked ubiquitination in multiple signaling pathways and various human diseases including cancer. Increasing number of studies indicated that K63-linked ubiquitination controls initiation, development, invasion, metastasis, and therapy of diverse cancers. Here, we summarized molecular mechanisms of K63-linked ubiquitination dictating different biological activities of tumor and highlighted novel opportunities for future therapy targeting certain regulation of K63-linked ubiquitination in tumor.

Nuclear Dishevelled: An enigmatic role in governing cell fate and Wnt signaling

The Dishevelled gene was first identified in Drosophila mutants with disoriented hair and bristle polarity and subsequent work has now demonstrated its importance in critical and diverse aspects of biology. Since those early discoveries, Dishevelled has been shown to coordinate a plethora of developmental and cellular processes that range from controlling cell polarity during gastrulation to partnering with chromatin modifying enzymes to regulate histone methylation at genomic loci. While the role of DVL in development is well-respected and the cytosolic function of DVL has been studied more extensively, its nuclear role continues to remain murky. In this review we highlight some of the seminal discoveries that have contributed to the field, but the primary focus is to discuss recent advances with respect to the nuclear role of Dishevelled. This nuclear function of Dishevelled is a dimension which is proving to be increasingly important yet remains enigmatic.

Genotoxicity-Stimulated and CYLD-Driven Malignant Transformation

Oxidative stress, which can cause DNA damage, can both activate TNF-R1 directly in the absence of TNF stimulation and phosphorylate c-Abl, thus promoting its cytoplasmic translocation. Persistent cytoplasmic localization of c-Abl has been associated with cellular transformation. c-Abl phosphorylates OTULIN at tyrosine 56, thereby disrupting its relationship with LUBAC. OTULIN-released LUBAC interacts with SPATA2 and is recruited to the TNF-R1sc, facilitating SPATA2-CYLD interaction. All these interactions are required for the activation of IKKβ to stimulate NF-κB transcriptional activity following genotoxic stress. IKKβ also induces the critical phosphorylation of CYLD at serine 568 to increase its deubiquitinating (DUB) activity required for the termination of signaling cascades. Contrary to the widespread belief that CYLD is an absolute tumor suppressor, CYLD initiates and terminates NF-κB activity by alternately using its oncoprotein and tumor suppressor activities, respectively. If IKKβ fails to achieve the DUB activity-inducing phosphorylation at serine 568, CYLD would operate in a sustained mode of oncogenic activity. The resulting dysregulated NF-κB activation and other accompanying pathologies will disrupt cellular homeostasis in favor of transformation.

Cylindromatosis drives synapse pruning and weakening by promoting macroautophagy through Akt-mTOR signaling

The lysine-63 deubiquitinase cylindromatosis (CYLD) is long recognized as a tumor suppressor in immunity and inflammation, and its loss-of-function mutations lead to familial cylindromatosis. However, recent studies reveal that CYLD is enriched in mammalian brain postsynaptic densities, and a gain-of-function mutation causes frontotemporal dementia (FTD), suggesting critical roles at excitatory synapses. Here we report that CYLD drives synapse elimination and weakening by acting on the Akt-mTOR-autophagy axis. Mice lacking CYLD display abnormal sociability, anxiety- and depression-like behaviors, and cognitive inflexibility. These behavioral impairments are accompanied by excessive synapse numbers, increased postsynaptic efficacy, augmented synaptic summation, and impaired NMDA receptor-dependent hippocampal long-term depression (LTD). Exogenous expression of CYLD results in removal of established dendritic spines from mature neurons in a deubiquitinase activity-dependent manner. In search of underlying molecular mechanisms, we find that CYLD knockout mice display marked overactivation of Akt and mTOR and reduced autophagic flux, and conversely, CYLD overexpression potently suppresses Akt and mTOR activity and promotes autophagy. Consequently, abrogating the Akt-mTOR-autophagy signaling pathway abolishes CYLD-induced spine loss, whereas enhancing autophagy in vivo by the mTOR inhibitor rapamycin rescues the synaptic pruning and LTD deficits in mutant mice. Our findings establish CYLD, via Akt-mTOR signaling, as a synaptic autophagy activator that exerts critical modulations on synapse maintenance, function, and plasticity.

CYLD destabilizes NoxO1 protein by promoting ubiquitination and regulates prostate cancer progression

The NADPH oxidase (Nox) family of enzymes is solely dedicated in the generation of reactive oxygen species (ROS). ROS generated by Nox are involved in multiple signaling cascades and a myriad of pathophysiological conditions including cancer. As such, ROS seem to have both detrimental and beneficial roles in a number of cellular functions, including cell signaling, growth, apoptosis and proliferation. Regulatory mechanisms are required to control the activity of Nox enzymes in order to maintain ROS balance within the cell. Here, we performed genome-wide screening for deubiquitinating enzymes (DUBs) regulating Nox organizer 1 (NoxO1) protein expression using a CRISPR/Cas9-mediated DUB-knockout library. We identified cylindromatosis (CYLD) as a binding partner regulating NoxO1 protein expression. We demonstrated that the overexpression of CYLD promotes ubiquitination of NoxO1 protein and reduces the NoxO1 protein half-life. The destabilization of NoxO1 protein by CYLD suppressed excessive ROS generation. Additionally, CRISPR/Cas9-mediated knockout of CYLD in PC-3 cells promoted cell proliferation, migration, colony formation and invasion in vitro. In xenografted mice, injection of CYLD-depleted cells consistently led to tumor development with increased weight and volume. Taken together, these results indicate that CYLD acts as a destabilizer of NoxO1 protein and could be a potential tumor suppressor target for cancer therapeutics.

Palmitate impairs the autophagic flux to induce p62-dependent apoptosis through the upregulation of CYLD in NRCMs

The most abundant saturated free fatty acid such as palmitate (PA), can accumulate in cardiomyocytes and induce lipotoxicity. CYLD is a known regulator in the development of cardiovascular disease and an important mediator of apoptosis. The role of CYLD in PA-induced cardiomyocyte apoptosis is not completely known. Here, we showed that PA treatment resulted in a concentration- and time-dependent effect on neonatal rat cardiomyocytes (NRCMs) apoptosis. PA impaired autophagy by significantly increasing the expression levels of LC3-II, Beclin 1, and also p62 in NRCMs. The autophagy flux was measured by detecting the fluorescence in the cells with Ad-mCherry-GFP-LC3B, a decrease in red puncta and a significant increase in yellow puncta in response to PA stimulation indicated that PA impairs the autophagic flux at the late stage of autophagosome-lysosome fusion. We further found knocked down of p62 by siRNA significantly decreased the expression level of cleaved caspase-3, decreased the apoptosis rate, also alleviated the loss of mitochondrial membrane potential, and decreased AIF and Cyt C releasing from mitochondria into the cytoplasm in the PA-treated NRCMs. From this, we considered that p62 accumulation was responsible for mitochondria-mediated apoptosis in PA-treated NRCMs. In addition, PA-induced a strong elevation of CYLD, siRNA-mediated knockdown of CYLD significantly antagonized PA-induced apoptosis and restored the autophagic flux in NRCMs. Knockdown of CYLD activation of the Wnt/β-catenin pathway to restore the autophagic flux and reduce the accumulation of p62 in PA- stimulated NRCMs, while an inhibitor of the Wnt/β-catenin pathway reversed this effect. Thus, our findings provide new insight into the molecular mechanism of PA toxicity in myocardial cells and suggest that CYLD may be a new therapeutic target for lipotoxic cardiomyopathy.

Genetic Testing in CYLD Cutaneous Syndrome: An Update

CYLD cutaneous syndrome (CCS) is an inclusive label for the inherited skin adnexal tumour syndromes Brooke–Spiegler Syndrome (BSS-OMIM 605041), familial cylindromatosis (FC – OMIM 132700) and multiple familial trichoepitheliomas (MFT-OMIM 601606). All three syndromes arise due to germline pathogenic variants in CYLD, a tumour suppressor gene (OMIM 605018). CCS is transmitted in an autosomal dominant pattern, and has variable expressivity, both of the three syndromic phenotypes, and of the severity of tumour burden. Age-related penetrance figures are not precisely reported. The first tumours typically appear during puberty and progressively accumulate through adulthood. Penetrance is typically high, with equal numbers of males and females affected. Genetic testing is important for confirmation of the clinical diagnosis, genetic counselling and family planning, including preimplantation diagnosis. Additionally, identified CCS patients may be eligible for future clinical trials of non-surgical pre-emptive interventions that aim to prevent tumour growth. In this update, we review the clinical presentations of germline and mosaic CCS. An overview of the germline pathogenic variant spectrum of patients with CCS reveals more than 100 single nucleotide variants and small insertions and deletions in coding exons, most frequently resulting in predicted truncation. In addition, a minority of patients have large deletions involving the CYLD gene, intronic pathogenic variants that affect splicing, or inversions. We discuss germline and somatic testing approaches. Somatic testing of tumour tissue, relevant in mosaic CCS, can reveal recurrently detected pathogenic variants when two or more tumours are tested. This can influence genetic testing of children, who may inherit this as a germline variant, and inform genetic counselling and prenatal diagnosis. Finally, we discuss testing technologies that are currently used, their benefits and limitations, and future directions for genetic testing in CCS.

RNF43 inhibits WNT5A-driven signaling and suppresses melanoma invasion and resistance to the targeted therapy

RNF43 is an E3 ubiquitin ligase and known negative regulator of WNT/β-catenin signaling. We demonstrate that RNF43 is also a regulator of noncanonical WNT5A-induced signaling in human cells. Analysis of the RNF43 interactome using BioID and immunoprecipitation showed that RNF43 can interact with the core receptor complex components dedicated to the noncanonical Wnt pathway such as ROR1, ROR2, VANGL1, and VANGL2. RNF43 triggers VANGL2 ubiquitination and proteasomal degradation and clathrin-dependent internalization of ROR1 receptor and inhibits ROR2 activation. These activities of RNF43 are physiologically relevant and block pro-metastatic WNT5A signaling in melanoma. RNF43 inhibits responses to WNT5A, which results in the suppression of invasive properties of melanoma cells. Furthermore, RNF43 prevented WNT5A-assisted development of resistance to BRAF V600E and MEK inhibitors. Next, RNF43 acted as melanoma suppressor and improved response to targeted therapies in vivo. In line with these findings, RNF43 expression decreases during melanoma progression and RNF43-low patients have a worse prognosis. We conclude that RNF43 is a newly discovered negative regulator of WNT5A-mediated biological responses that desensitizes cells to WNT5A.

Dishevelled-1 DIX and PDZ domain lysine residues regulate oncogenic Wnt signaling

DVL proteins are central mediators of the Wnt pathway and relay complex input signals into different branches of the Wnt signaling network. However, molecular mechanism(s) that regulate DVL-mediated relay of Wnt signals still remains unclear. Here, for the first time, we elucidate the functional significance of three DVL-1 lysines (K/Lys) which are subject to post-translational acetylation. We demonstrate that K34 Lys residue in the DIX domain regulates subcellular localization of β-catenin, thereby influencing downstream Wnt target gene expression. Additionally, we show that K69 (DIX domain) and K285 (PDZ domain) regulate binding of DVL-1 to Wnt target gene promoters and modulate expression of Wnt target genes including CMYC, OCT4, NANOG, and CCND1, in cell line models and xenograft tumors. Finally, we report that conserved DVL-1 lysines modulate various oncogenic functions such as cell migration, proliferation, cell-cycle progression, 3D-spheroid formation and in-vivo tumor growth in breast cancer models. Collectively, these findings highlight the importance of DVL-1 domain-specific lysines which were recently shown to be acetylated and characterize their influence on Wnt signaling. These site-specific modifications may be subject to regulation by therapeutics already in clinical use (lysine deacetylase inhibitors such as Panobinostat and Vorinostat) or may possibly have prognostic utility in translational efforts that seek to modulate dysfunctional Wnt signaling.

Regulatory interplay between microRNAs and WNT pathway in glioma

Glioma is one of the most common neoplasms of the central nervous system with a poor survival. Due to the obstacles in treating this disease, a part of recent studies mainly focuses on identifying the underlying molecular mechanisms that contribute to its malignancy. Altering microRNAs (miRNAs) expression pattern has been identified obviously in many cancers. Through regulating various targets and signaling pathways, miRNAs play a pivotal role in cancer progression. As one of the essential signaling pathways, WNT pathway is dysregulated in many cancers, and a growing body of evidence emphasis its dysregulation in glioma. Herein, we provide a comprehensive review of miRNAs involved in WNT pathway in glioma. Moreover, we show the interplay between miRNAs and WNT pathway in regulating different processes such as proliferation, invasion, migration, radio/chemotherapy resistance, and epithelial-mesenchymal-transition. Then, we introduce several drugs and treatments against glioma, which their effects are mediated through the interplay of WNT pathway and miRNAs.

Regulation of Dishevelled protein activity and stability by post-translational modifications and autophagy

As a key component of Wnt signaling, Dishevelled (Dvl/Dsh) plays essential roles in development processes and adult tissue homeostasis in multicellular organisms, and its deregulation results in human development disorders and other diseases. Dvl integrates and relays complex Wnt signals by acting as a branch-point of β-catenin-dependent canonical and β-catenin-independent noncanonical pathways. It dynamically interacts with multiple proteins to modulate Wnt signaling, while its activity and stability are tightly controlled by other proteins. This Review summarizes the current understanding of regulation of Dvl activity, localization, and stability by post-translational modifications, aggregation, and autophagy, and the impacts on Dvl function in both Wnt signaling and biological processes.

Can We Pharmacologically Target Dishevelled: The Key Signal Transducer in the Wnt Pathways?

Dishevelled (DVL) is the central signal transducer in both Wnt/β-catenin-dependent and independent signalling pathways. DVL is required to connect receptor complexes and downstream effectors. Since proximal Wnt pathway components and DVL itself are upregulated in many types of cancer, DVL represents an attractive therapeutic target in the Wnt-addicted cancers and other disorders caused by aberrant Wnt signalling. Here, we discuss progress in several approaches for the modulation of DVL function and hence inhibition of the Wnt signalling. Namely, we sum up the potential of modulation of enzymes that control post-translational modification of DVL - such as inhibition of DVL kinases or promotion of DVL ubiquitination and degradation. In addition, we discuss research directions that can take advantage of direct interaction with the protein domains essential for DVL function: the inhibition of DIX- and DEP-domain mediated polymerization and interaction of DVL PDZ domain with its ligands.

Deubiquitinating Enzymes Orchestrate the Cancer Stem Cell-Immunosuppressive Niche Dialogue: New Perspectives and Therapeutic Potential

Cancer stem cells (CSCs) are sparks for igniting tumor recurrence and the instigators of low response to immunotherapy and drug resistance. As one of the important components of tumor microenvironment, the tumor associated immune microenvironment (TAIM) is driving force for the heterogeneity, plasticity and evolution of CSCs. CSCs create the inhibitory TAIM (ITAIM) mainly through four stemness-related signals (SRSs), including Notch-nuclear factor-κB axis, Hedgehog, Wnt and signal transducer and activator of transcription. Ubiquitination and deubiquitination in proteins related to the specific stemness of the CSCs have a profound impact on the regulation of ITAIM. In regulating the balance between ubiquitination and deubiquitination, it is crucial for deubiquitinating enzymes (DUBs) to cleave ubiquitin chains from substrates. Ubiquitin-specific peptidases (USPs) comprise the largest family of DUBs. Growing evidence suggests that they play novel functions in contribution of ITAIM, including regulating tumor immunogenicity, activating stem cell factors, upregulating the SRSs, stabilizing anti-inflammatory receptors, and regulating anti-inflammatory cytokines. These overactive or abnormal signaling may dampen antitumor immune responses. The inhibition of USPs could play a regulatory role in SRSs and reversing ITAIM, and also have great potential in improving immune killing ability against tumor cells, including CSCs. In this review, we focus on the USPs involved in CSCs signaling pathways and regulating ITAIM, which are promising therapeutic targets in antitumor therapy.

Ubiquitination and Deubiquitination in Oral Disease

Oral health is an integral part of the general health and well-being of individuals. The presence of oral disease is potentially indicative of a number of systemic diseases and may contribute to their early diagnosis and treatment. The ubiquitin (Ub) system has been shown to play a role in cellular immune response, cellular development, and programmed cell death. Ubiquitination is a post-translational modification that occurs in eukaryotes. Its mechanism involves a number of factors, including Ub-activating enzymes, Ub-conjugating enzymes, and Ub protein ligases. Deubiquitinating enzymes, which are proteases that reversely modify proteins by removing Ub or Ub-like molecules or remodeling Ub chains on target proteins, have recently been regarded as crucial regulators of ubiquitination-mediated degradation and are known to significantly affect cellular pathways, a number of biological processes, DNA damage response, and DNA repair pathways. Research has increasingly shown evidence of the relationship between ubiquitination, deubiquitination, and oral disease. This review investigates recent progress in discoveries in diseased oral sites and discusses the roles of ubiquitination and deubiquitination in oral disease.

PLEKHA4 Promotes Wnt/β-Catenin Signaling-Mediated G1-S Transition and Proliferation in Melanoma

Despite recent promising advances in targeted therapies and immunotherapies, patients with melanoma incur substantial mortality. In particular, inhibitors targeting BRAF-mutant melanoma can lead to resistance, and no targeted therapies exist for NRAS-mutant melanoma, motivating the search for additional therapeutic targets and vulnerable pathways. Here we identify a regulator of Wnt/β-catenin signaling, PLEKHA4, as a factor required for melanoma proliferation and survival. PLEKHA4 knockdown in vitro decreased Dishevelled levels, attenuated Wnt/β-catenin signaling, and blocked progression through the G1-S cell-cycle transition. In mouse xenograft and allograft models, inducible PLEKHA4 knockdown attenuated tumor growth in BRAF- and NRAS-mutant melanomas and exhibited an additive effect with the clinically used inhibitor encorafenib in a BRAF-mutant model. As an E3 ubiquitin ligase regulator with both lipid- and protein-binding partners, PLEKHA4 presents several opportunities for targeting with small molecules. Our work identifies PLEKHA4 as a promising drug target for melanoma and clarifies a controversial role for Wnt/β-catenin signaling in the control of melanoma proliferation. SIGNIFICANCE: This study establishes that melanoma cell proliferation requires the protein PLEKHA4 to promote pathologic Wnt signaling for proliferation, highlighting PLEKHA4 inhibition as a new avenue for the development of targeted therapies.

Aberrations of Chromosomes 1 and 16 in Breast Cancer: A Framework for Cooperation of Transcriptionally Dysregulated Genes

Derivative chromosome der(1;16), isochromosome 1q, and deleted 16q-producing arm-level 1q-gain and/or 16q-loss-are recurrent cytogenetic abnormalities in breast cancer, but their exact role in determining the malignant phenotype is still largely unknown. We exploited The Cancer Genome Atlas (TCGA) data to generate and analyze groups of breast invasive carcinomas, called 1,16-chromogroups, that are characterized by a pattern of arm-level somatic copy number aberrations congruent with known cytogenetic aberrations of chromosome 1 and 16. Substantial differences were found among 1,16-chromogroups in terms of other chromosomal aberrations, aneuploidy scores, transcriptomic data, single-point mutations, histotypes, and molecular subtypes. Breast cancers with a co-occurrence of 1q-gain and 16q-loss can be distinguished in a "low aneuploidy score" group, congruent to der(1;16), and a "high aneuploidy score" group, congruent to the co-occurrence of isochromosome 1q and deleted 16q. Another three groups are formed by cancers showing separately 1q-gain or 16q-loss or no aberrations of 1q and 16q. Transcriptome comparisons among the 1,16-chromogroups, integrated with functional pathway analysis, suggested the cooperation of overexpressed 1q genes and underexpressed 16q genes in the genesis of both ductal and lobular carcinomas, thus highlighting the putative role of genes encoding gamma-secretase subunits (APH1A, PSEN2, and NCSTN) and Wnt enhanceosome components (BCL9 and PYGO2) in 1q, and the glycoprotein E-cadherin (CDH1), the E3 ubiquitin-protein ligase WWP2, the deubiquitinating enzyme CYLD, and the transcription factor CBFB in 16q. The analysis of 1,16-chromogroups is a strategy with far-reaching implications for the selection of cancer cell models and novel experimental therapies.

Molecular Mechanisms of DUBs Regulation in Signaling and Disease

The large family of deubiquitinating enzymes (DUBs) are involved in the regulation of a plethora of processes carried out inside the cell by protein ubiquitination. Ubiquitination is a basic pathway responsible for the correct protein homeostasis in the cell, which could regulate the fate of proteins through the ubiquitin–proteasome system (UPS). In this review we will focus on recent advances on the molecular mechanisms and specificities found for some types of DUBs enzymes, highlighting illustrative examples in which the regulatory mechanism for DUBs has been understood in depth at the molecular level by structural biology. DUB proteases are responsible for cleavage and regulation of the multiple types of ubiquitin linkages that can be synthesized inside the cell, known as the ubiquitin-code, which are tightly connected to specific substrate functions. We will display some strategies carried out by members of different DUB families to provide specificity on the cleavage of particular ubiquitin linkages. Finally, we will also discuss recent progress made for the development of drug compounds targeting DUB proteases, which are usually correlated to the progress of many pathologies such as cancer and neurodegenerative diseases.

Basal Cell Adenoma and Basal Cell Adenocarcinoma

Basal cell adenoma (BCA) and basal cell adenocarcinoma (BCAC) are uncommon biphasic salivary gland tumors having morphologic similarities to other biphasic salivary gland neoplasms having differentiation toward the intercalated ducts of the salivary gland. Both tumors show mixtures of trabecular, tubular, solid, and membranous solid patterns. BCAC is separated from BCA primarily by the presence of invasion in the former. The diagnosis of BCA and BCAC is best carried out with hematoxylin and eosin-stained sections and careful attention to detail of tumors in the differential diagnosis, including adenoid cystic carcinoma, pleomorphic adenoma, and epithelial myoepithelial carcinoma.

Ubiquitin-proteasome system (UPS) as a target for anticancer treatment

The ubiquitin-proteasome system (UPS) plays an important role in the cellular processes for protein quality control and homeostasis. Dysregulation of the UPS has been implicated in numerous diseases, including cancer. Indeed, components of UPS are frequently mutated or abnormally expressed in various cancers. Since Bortezomib, a proteasome inhibitor, received FDA approval for the treatment of multiple myeloma and mantle cell lymphoma, increasing numbers of researchers have been seeking drugs targeting the UPS as a cancer therapeutic strategy. Here, we introduce the essential component of UPS, including ubiquitinating enzymes, deubiquitinating enzymes and 26S proteasome, and we summarize their targets and mechanisms that are crucial for tumorigenesis. In addition, we briefly discuss some UPS inhibitors, which are currently in clinical trials as cancer therapeutics.

Deubiquitinating Enzyme-Mediated Signaling Networks in Cancer Stem Cells

Cancer stem cells (CSCs) have both the capacity for self-renewal and the potential to differentiate and contribute to multiple tumor properties, such as recurrence, metastasis, heterogeneity, multidrug resistance, and radiation resistance. Thus, CSCs are considered to be promising therapeutic targets for cancer therapy. The function of CSCs can be regulated by ubiquitination and deubiquitination of proteins related to the specific stemness of the cells executing various stem cell fate choices. To regulate the balance between ubiquitination and deubiquitination processes, the disassembly of ubiquitin chains from specific substrates by deubiquitinating enzymes (DUBs) is crucial. Several key developmental and signaling pathways have been shown to play essential roles in this regulation. Growing evidence suggests that overactive or abnormal signaling within and among these pathways may contribute to the survival of CSCs. These signaling pathways have been experimentally shown to mediate various stem cell properties, such as self-renewal, cell fate decisions, survival, proliferation, and differentiation. In this review, we focus on the DUBs involved in CSCs signaling pathways, which are vital in regulating their stem-cell fate determination.

CYLD Promotes Apoptosis of Nasopharyngeal Carcinoma Cells by Regulating NDRG1

Purpose

Nasopharyngeal carcinoma (NPC) is among the most common malignancies derived from the epithelium of the nasopharynx. To date, the regulatory networks involved in NPC have not been fully identified. Previous studies revealed multiple loss-of-function mutations in NPC and specifically in cylindromatosis lysine 63 deubiquitinase (CYLD); however, the exact role of CYLD in NPC progression and its potential mechanism remains unclear.

Methods

We performed immunohistochemical (IHC) staining and real-time quantitative polymerase chain reaction (qPCR) to measure CYLD expression in NPC tissues, and Western blot was conducted to determine CYLD levels in NPC cell lines. Cell proliferation was detected by CCK8 assay and colony formation analysis, and apoptosis was determined by Annexin V/propidium iodide staining. Potential targets of CYLD were verified by co-immunoprecipitation and mass spectrometry. Xenograft assay was conducted to confirm the role of CYLD in vivo.

Results

We found that CYLD levels were significantly decreased in both NPC tissues and cell lines, and that CYLD overexpression inhibited NPC cell proliferation and promoted apoptosis. Additionally, we revealed that CYLD bound and upregulated N-Myc downstream regulated 1 (NDRG1), and that silencing NDRG1 abolished the tumor-suppressor effect of CYLD on NPC cells. Furthermore, CYLD suppressed tumor growth in xenograft mice models.

Conclusion

These results suggest CYLD as a tumor suppressor, potential biomarker for diagnosing NPC, and therapeutic target.

RNF43 truncations trap CK1 to drive niche-independent self-renewal in cancer

Wnt/β-catenin signaling is a primary pathway for stem cell maintenance during tissue renewal and a frequent target for mutations in cancer. Impaired Wnt receptor endocytosis due to loss of the ubiquitin ligase RNF43 gives rise to Wnt-hypersensitive tumors that are susceptible to anti-Wnt-based therapy. Contrary to this paradigm, we identify a class of RNF43 truncating cancer mutations that induce β-catenin-mediated transcription, despite exhibiting retained Wnt receptor downregulation. These mutations interfere with a ubiquitin-independent suppressor role of the RNF43 cytosolic tail that involves Casein kinase 1 (CK1) binding and phosphorylation. Mechanistically, truncated RNF43 variants trap CK1 at the plasma membrane, thereby preventing β-catenin turnover and propelling ligand-independent target gene transcription. Gene editing of human colon stem cells shows that RNF43 truncations cooperate with p53 loss to drive a niche-independent program for self-renewal and proliferation. Moreover, these RNF43 variants confer decreased sensitivity to anti-Wnt-based therapy. Our data demonstrate the relevance of studying patient-derived mutations for understanding disease mechanisms and improved applications of precision medicine.

CYLD Alterations in the Tumorigenesis and Progression of Human Papillomavirus-Associated Head and Neck Cancers

Genetic alterations of CYLD lysine 63 deubiquitinase (CYLD), a tumor-suppressor gene encoding a deubiquitinase (DUB) enzyme, are associated with the formation of tumors in CYLD cutaneous syndrome. Genome sequencing efforts have revealed somatic CYLD alterations in multiple human cancers. Moreover, in cancers commonly associated with human papillomavirus (HPV) infection (e.g., head and neck squamous cell carcinoma), CYLD alterations are preferentially observed in the HPV-positive versus HPV-negative form of the disease. The CYLD enzyme cleaves K63-linked polyubiquitin from substrate proteins, resulting in the disassembly of key protein complexes and the inactivation of growth-promoting signaling pathways, including pathways mediated by NF-κB, Wnt/β-catenin, and c-Jun N-terminal kinases. Loss-of-function CYLD alterations lead to aberrant activation of these signaling pathways, promoting tumorigenesis and malignant transformation. This review summarizes the association and potential role of CYLD somatic mutations in HPV-positive cancers, with particular emphasis on the role of these alterations in tumorigenesis, invasion, and metastasis. Potential therapeutic strategies for patients whose tumors harbor CYLD alterations are also discussed. IMPLICATIONS: Alterations in CYLD gene are associated with HPV-associated cancers, contribute to NF-κB activation, and are implicated in invasion and metastasis.

USP9X Deubiquitylates DVL2 to Regulate WNT Pathway Specification

The WNT signaling network is comprised of multiple receptors that relay various input signals via distinct transduction pathways to execute multiple complex and context-specific output processes. Integrity of the WNT signaling network relies on proper specification between canonical and noncanonical pathways, which presents a regulatory challenge given that several signal transducing elements are shared between pathways. Here, we report that USP9X, a deubiquitylase, and WWP1, an E3 ubiquitin ligase, regulate a ubiquitin rheostat on DVL2, a WNT signaling protein. Our findings indicate that USP9X-mediated deubiquitylation of DVL2 is required for canonical WNT activation, while increased DVL2 ubiquitylation is associated with localization to actin-rich projections and activation of the planar cell polarity (PCP) pathway. We propose that a WWP1-USP9X axis regulates a ubiquitin rheostat on DVL2 that specifies its participation in either canonical WNT or WNT-PCP pathways. These findings have important implications for therapeutic targeting of USP9X in human cancer.

DVL2 is a signal transducing protein that participates in canonical and noncanonical WNT signaling relays. Here, Nielsen et al. report that the deubiquitylase USP9X and the E3 ubiquitin ligase WWP1 operate on DVL2 to establish a ubiquitin rheostat that contributes to WNT pathway specification in human breast cancer cells.

Long noncoding RNA mediates stroke-induced neurogenesis

Neurogenesis contributes to poststroke recovery. Long noncoding RNAs (lncRNAs) participate in the regulation of stem cell self-renewal and differentiation. However, the role of lncRNAs in stroke-induced neurogenesis remains unknown. In this study, we found that H19 was the most highly upregulated lncRNA in neural stem cells (NSCs) of the subventricular zone (SVZ) of rats subjected to focal cerebral ischemia. Deletion of H19 suppressed cell proliferation, promoted cell death, and blocked NSC differentiation. RNA sequencing analysis revealed that genes deregulated by H19 knockdown were those that are involved in transcription, apoptosis, proliferation, cell cycle, and response to hypoxia. H19 knockdown significantly increased the transcription of cell cycle-related genes including p27, whereas overexpression of H19 substantially reduced expression of these genes through the interaction with chromatin remodeling proteins EZH2 and SUZ12. Moreover, H19 regulated neurogenesis-related miRNAs. Inactivation of H19 in NSCs of ischemic rats attenuated spontaneous functional recovery after stroke. Collectively, our data provide novel insights into the epigenetic regulation of lncRNAs in stroke-induced neurogenesis.

Regulation of Wnt Signaling through Ubiquitination and Deubiquitination in Cancers

The Wnt signaling pathway plays important roles in embryonic development, homeostatic processes, cell differentiation, cell polarity, cell proliferation, and cell migration via the β-catenin binding of Wnt target genes. Dysregulation of Wnt signaling is associated with various diseases such as cancer, aging, Alzheimer’s disease, metabolic disease, and pigmentation disorders. Numerous studies entailing the Wnt signaling pathway have been conducted for various cancers. Diverse signaling factors mediate the up- or down-regulation of Wnt signaling through post-translational modifications (PTMs), and aberrant regulation is associated with several different malignancies in humans. Of the numerous PTMs involved, most Wnt signaling factors are regulated by ubiquitination and deubiquitination. Ubiquitination by E3 ligase attaches ubiquitins to target proteins and usually induces proteasomal degradation of Wnt signaling factors such as β-catenin, Axin, GSK3, and Dvl. Conversely, deubiquitination induced by the deubiquitinating enzymes (DUBs) detaches the ubiquitins and modulates the stability of signaling factors. In this review, we discuss the effects of ubiquitination and deubiquitination on the Wnt signaling pathway, and the inhibitors of DUBs that can be applied for cancer therapeutic strategies.

Activity of Smurf2 Ubiquitin Ligase Is Regulated by the Wnt Pathway Protein Dishevelled

Wnt and BMP signaling pathways are two key molecular machineries regulating development and homeostasis. The efficient coordination of Wnt and BMP is essential in many developmental processes such as establishment of antero-posterior and dorso-ventral body axis, regulation of convergent extension, or development of various organ systems. SMAD ubiquitination regulatory factor (Smurf) family of E3 ubiquitin ligases are important and evolutionary conserved regulators of TGF-β/BMP signaling pathways. Smurf2 has been previously shown to regulate Wnt/planar cell polarity (PCP) signaling pathway by ubiquitinating Prickle1, one of the key components of PCP. We explored the role of Smurf2 in Wnt pathways in further detail and identified that Smurf2 is also a ubiquitin ligase of Dishevelled (DVL), the key cytoplasmic signal transducer in the Wnt pathway. Interestingly, the Smurf2 and DVL relationship expands beyond substrate-E3 ligase. We can show that DVL activates Smurf2, which allows Smurf2 to ubiquitinate its substrates from Wnt/PCP (Prickle1) as well as TGF-β/BMP (Smad2) pathways more efficiently. Using SMAD7 as an example of Smurf2 activator we show that DVL and SMAD7 both activates Smurf2 activity. In HEK293 cells the deficiency of DVL phenocopies absence of Smurf2 and leads to the increased phosphorylation of R-Smads. Smurf2-DVL connection provides a novel and intriguing point of crosstalk for Wnt and BMP pathways.

The role of ubiquitination in tumorigenesis and targeted drug discovery

Ubiquitination, an important type of protein posttranslational modification (PTM), plays a crucial role in controlling substrate degradation and subsequently mediates the "quantity" and "quality" of various proteins, serving to ensure cell homeostasis and guarantee life activities. The regulation of ubiquitination is multifaceted and works not only at the transcriptional and posttranslational levels (phosphorylation, acetylation, methylation, etc.) but also at the protein level (activators or repressors). When regulatory mechanisms are aberrant, the altered biological processes may subsequently induce serious human diseases, especially various types of cancer. In tumorigenesis, the altered biological processes involve tumor metabolism, the immunological tumor microenvironment (TME), cancer stem cell (CSC) stemness and so on. With regard to tumor metabolism, the ubiquitination of some key proteins such as RagA, mTOR, PTEN, AKT, c-Myc and P53 significantly regulates the activity of the mTORC1, AMPK and PTEN-AKT signaling pathways. In addition, ubiquitination in the TLR, RLR and STING-dependent signaling pathways also modulates the TME. Moreover, the ubiquitination of core stem cell regulator triplets (Nanog, Oct4 and Sox2) and members of the Wnt and Hippo-YAP signaling pathways participates in the maintenance of CSC stemness. Based on the altered components, including the proteasome, E3 ligases, E1, E2 and deubiquitinases (DUBs), many molecular targeted drugs have been developed to combat cancer. Among them, small molecule inhibitors targeting the proteasome, such as bortezomib, carfilzomib, oprozomib and ixazomib, have achieved tangible success. In addition, MLN7243 and MLN4924 (targeting the E1 enzyme), Leucettamol A and CC0651 (targeting the E2 enzyme), nutlin and MI-219 (targeting the E3 enzyme), and compounds G5 and F6 (targeting DUB activity) have also shown potential in preclinical cancer treatment. In this review, we summarize the latest progress in understanding the substrates for ubiquitination and their special functions in tumor metabolism regulation, TME modulation and CSC stemness maintenance. Moreover, potential therapeutic targets for cancer are reviewed, as are the therapeutic effects of targeted drugs.

Coupling Conjugation and Deconjugation Activities to Achieve Cellular Ubiquitin Dynamics

In eukaryotic cells, proteome remodeling is mediated by the ubiquitin-proteasome system, which regulates protein degradation, trafficking, and signaling events in the cell. Interplay between the cellular proteome and ubiquitin is complex and dynamic and many regulatory features that support this system have only recently come into focus. An unexpected recurring feature in this system is the physical interaction between E3 ubiquitin ligases and deubiquitylases (DUBs). Recent studies have reported on the regulatory significance of DUB-E3 interactions and it is becoming clear that they play important but complicated roles in the regulation of diverse cellular processes. Here, we summarize the current understanding of interactions between ubiquitin conjugation and deconjugation machineries and we examine the regulatory logic of these enigmatic complexes.

CYLD, a mechanosensitive deubiquitinase, regulates TGFβ signaling in load-induced bone formation

Many signaling pathways involved in bone homeostasis also participate in the anabolic response of bone to mechanical loading. For example, TGFβ signaling coordinates the maintenance of bone mass and bone quality through its effects on osteoblasts, osteoclasts, and osteocytes. TGFβ signaling is also essential for the mechanosensitive formation of new bone. However, the mechanosensitive mechanisms controlling TGFβ signaling in osteocytes remain to be determined, particularly those that integrate TGFβ signaling with other early responses to mechanical stimulation. Here, we used an in vivo mouse hindlimb loading model to identify mechanosensitive molecules in the TGFβ pathway, and MLO-Y4 cells to evaluate their interactions with the prostaglandin E2 (PGE2) pathway, which is well-known for its rapid response to mechanical stimulation and its role in bone anabolism. Although mRNA levels for several TGFβ ligands, receptors, and effectors were unchanged, the level of phosphorylated Smad2/3 (pSmad2/3) was reduced in tibial bone as early as 3 h after early mechanical stimulation. We found that PGE2 and its receptor, EP2, repress pSmad2/3 levels and transactivation of Serpine1 in osteocytes. PGE2 and EP2 control the level of pSmad2/3 through a proteasome-dependent mechanism that relies on the deubiquitinase CYLD. CYLD protein levels were also reduced in the tibiae within 3 h of mechanical loading. Using CYLD-deficient mice, we found that CYLD is required for the rapid load-mediated repression of pSmad2/3 and for load-induced bone formation. These data introduce CYLD as a mechanosensitive deubiquitinase that participates in the prostaglandin-dependent repression of TGFβ signaling in osteocytes.

Ubiquitin-Regulated Cell Proliferation and Cancer

Ubiquitin ligases (E3) play a crucial role in the regulation of different cellular processes such as proliferation and differentiation via recognition, interaction, and ubiquitination of key cellular proteins in a spatial and temporal regulated manner. The type of ubiquitin chain formed determines the fate of the substrates. The ubiquitinated substrates can be degraded by the proteasome, display altered subcellular localization, or can suffer modifications on their interaction with functional protein complexes. Deregulation of E3 activities is frequently found in various human pathologies, including cancer. The illegitimated or accelerated degradation of oncosuppressive proteins or, inversely, the abnormally high accumulation of oncoproteins, contributes to cell proliferation and transformation. Anomalies in protein abundance may be related to mutations that alter the direct or indirect recognition of proteins by the E3 enzymes or alterations in the level of expression or activity of ubiquitin ligases. Through a few examples, we illustrate here the complexity and diversity of the molecular mechanisms related to protein ubiquitination involved in cell cycle regulation. We will discuss the role of ubiquitin-dependent degradation mediated by the proteasome, the role of non-proteolytic ubiquitination during cell cycle progression, and the consequences of this deregulation on cellular transformation. Finally, we will highlight the novel opportunities that arise from these studies for therapeutic intervention.

Deubiquitinating Enzymes: A Critical Regulator of Mitosis

Mitosis is a complex and dynamic process that is tightly regulated by a large number of mitotic proteins. Dysregulation of these proteins can generate daughter cells that exhibit genomic instability and aneuploidy, and such cells can transform into tumorigenic cells. Thus, it is important for faithful mitotic progression to regulate mitotic proteins at specific locations in the cells at a given time in each phase of mitosis. Ubiquitin-dependent modifications play critical roles in this process by regulating the degradation, translocation, or signal transduction of mitotic proteins. Here, we review how ubiquitination and deubiquitination regulate the progression of mitosis. In addition, we summarize the substrates and roles of some deubiquitinating enzymes (DUBs) crucial for mitosis and describe how they contribute error correction during mitosis and control the transition between the mitotic phases.

Acetylation of conserved DVL-1 lysines regulates its nuclear translocation and binding to gene promoters in triple-negative breast cancer

Dishevelled (DVL) proteins are central mediators of the Wnt signalling pathway and are versatile regulators of several cellular processes, yet little is known about their post-translational regulation. Acetylation is a reversible post-translational modification (PTM) which regulates the function of several non-histone proteins involved in tumorigenesis. Since we previously demonstrated that lysine deacetylase, SIRT-1, regulates DVL protein levels and its function, we reasoned that DVL could potentially be a substrate for SIRT-1 mediated deacetylation. To further examine the potential role of multiple families of lysine deacetylases in the post-translational regulation of DVL, we screened for novel acetylation sites using liquid chromatography mass-spectrometry (LC-MS/MS) analysis. Herein, we report 12 DVL-1 lysine residues that show differential acetylation in response to changes in oxygen tension and deacetylase inhibition in triple-negative breast cancer (TNBC). PTMs are well documented to influence protein activity, and cellular localization. We also identify that acetylation of two key lysine residues, K69 and K285, present on the DIX and PDZ domains respectively, promote nuclear over cytoplasmic localization of DVL-1, and influences its promoter binding and regulation of genes implicated in cancer. Collectively, these findings for the first time, uncover acetylation as a novel layer of regulation of DVL-1 proteins.