NEDD4 E3 ligase: Functions and mechanism in human cancer

The Role of Ubiquitination and the E3 Ligase Nedd4 in Regulating Corneal Epithelial Wound Healing

Purpose

Ubiquitination serves as a fundamental post-translational modification in numerous cellular events. Yet, its role in regulating corneal epithelial wound healing (CEWH) remains elusive. This study endeavored to determine the function and mechanism of ubiquitination in CEWH.

Methods

Western blot and immunoprecipitation were used to discern ubiquitination alterations during CEWH in mice. Interventions, including neuronally expressed developmentally downregulated 4 (Nedd4) siRNA and proteasome/lysosome inhibitor, assessed their impact on CEWH. In vitro analyses, such as the scratch wound assay, MTS assay, and EdU staining, were conducted to gauge cell migration and proliferation in human corneal epithelial cells (HCECs). Moreover, transfection of miR-30/200 coupled with a luciferase activity assay ascertained their regulatory mechanism on Nedd4.

Results

Global ubiquitination levels were markedly increased during the mouse CEWH. Importantly, the application of either proteasomal or lysosomal inhibitors notably impeded the healing process both in vivo and in vitro. Furthermore, Nedd4 was identified as an essential E3 ligase for CEWH. Nedd4 expression was significantly upregulated during CEWH. In vivo studies revealed that downregulation of Nedd4 substantially delayed CEWH, whereas further investigations underscored its role in regulating cell proliferation and migration, through the Stat3 pathway by targeting phosphatase and tensin homolog (PTEN). Notably, our findings pinpointed miR-30/200 family members as direct regulators of Nedd4.

Conclusions

Ubiquitination holds pivotal significance in orchestrating CEWH. The critical E3 ligase Nedd4, under the regulatory purview of miR-30 and miR-200, facilitates CEWH through PTEN-mediated Stat3 signaling. This revelation sheds light on a prospective therapeutic target within the realm of CEWH.

Involvement of E3 ubiquitin ligase NEDD4-mediated YY1 ubiquitination in alleviating idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic and lethal lung disease characterized by progressive lung scarring. This study aims to elucidate the role of the E3 ubiquitin ligase NEDD4 in the ubiquitination of YY1 and its subsequent impact on TAB1 transcription, revealing a possible molecular mechanism in the development of IPF. Through bioinformatics analysis and both in vitro and in vivo experiments, we observed differential expression levels of NEDD4 and YY1 between normal and IPF samples, identifying NEDD4 as an upstream E3 ubiquitin ligase of YY1. Furthermore, binding sites for the transcription factor YY1 on the promoter region of TAB1 were discovered, indicating a direct interaction. In vitro experiments using HEPF cells showed that NEDD4 mediates the ubiquitination and degradation of YY1, leading to suppressed TAB1 transcription, thereby inhibiting cell proliferation and fibrogenesis. These findings were corroborated by in vivo experiments in an IPF mouse model, where the ubiquitination pathway facilitated by NEDD4 attenuated IPF progression through the downregulation of YY1 and TAB1 transcription. These results suggest that NEDD4 plays a crucial role in the development of IPF by modulating YY1 ubiquitination and TAB1 transcription, providing new insights into potential therapeutic targets for treating IPF.

PUM2 promoted osteoarthritis progression through PTEN-mediated chondrocyte ferroptosis by facilitating NEDD4 mRNA degradation

Osteoarthritis (OA) is a prevalent degenerative joint disease with a lack of effective therapeutic. Chondrocyte ferroptosis contributes to the progression of OA. PUM2 is shown to exacerbate ischemia-reperfusion-induced neuroinflammation by promoting ferroptosis, but its role in OA remains unexplored. Here, primary mouse chondrocytes were stimulated with IL-1β to mimic OA chondrocyte injury in vitro. And PUM2 was upregulated in OA cartilage tissues and IL-1β-induced chondrocytes. Silencing PUM2 alleviated IL-1β-induced chondrocyte inflammation and ECM degradation. Mechanistically, PUM2 facilitated the degradation of NEDD4 mRNA by binding to the 3'UTR of NEDD4 mRNA, which in turn inhibited NEDD4 induced PTEN ubiquitination and degradation. Consistently, NEDD4 silencing reversed the ameliorative effect of PUM2 knockdown on chondrocyte injury, and overexpression of PTEN abolished the improved role of NEDD4 in chondrocyte injury. Moreover, PTEN aggravated IL-1β-induced ferroptosis in chondrocytes through the Nrf2/HO-1 pathway by increasing the levels of Fe2+, ROS, MDA, and ACSL4 protein, decreasing the activity of SOD and the levels of GSH and GPX4 protein, and aggravating mitochondrial damage. Additionally, destabilized medial meniscus (DMM) were conducted to establish the OA mouse model, and adenovirus-mediated PUM2 shRNA was administered intra-articularly. Silencing PUM2 attenuated OA-induced cartilage damage in vivo. In conclusion, PUM2 promoted OA progression through PTEN-mediated chondrocyte ferroptosis by facilitating NEDD4 mRNA degradation.

PTMs of PD-1/PD-L1 and PROTACs application for improving cancer immunotherapy

Immunotherapy has been developed, which harnesses and enhances the innate powers of the immune system to fight disease, particularly cancer. PD-1 (programmed death-1) and PD-L1 (programmed death ligand-1) are key components in the regulation of the immune system, particularly in the context of cancer immunotherapy. PD-1 and PD-L1 are regulated by PTMs, including phosphorylation, ubiquitination, deubiquitination, acetylation, palmitoylation and glycosylation. PROTACs (Proteolysis Targeting Chimeras) are a type of new drug design technology. They are specifically engineered molecules that target specific proteins within a cell for degradation. PROTACs have been designed and demonstrated their inhibitory activity against the PD-1/PD-L1 pathway, and showed their ability to degrade PD-1/PD-L1 proteins. In this review, we describe how PROTACs target PD-1 and PD-L1 proteins to improve the efficacy of immunotherapy. PROTACs could be a novel strategy to combine with radiotherapy, chemotherapy and immunotherapy for cancer patients.

The E3 ubiquitin ligases regulate inflammation in cardiovascular diseases

Accumulating evidence has illustrated that the E3 ubiquitin ligases critically participate in the development and progression of cardiovascular diseases. Dysregulation of E3 ubiquitin ligases exacerbates cardiovascular diseases. Blockade or activation of E3 ubiquitin ligases mitigates cardiovascular performance. Therefore, in this review, we mainly introduced the critical role and underlying molecular mechanisms of E3 ubiquitin ligase NEDD4 family in governing the initiation and progression of cardiovascular diseases, including ITCH, WWP1, WWP2, Smurf1, Smurf2, Nedd4-1 and Nedd4-2. Moreover, the functions and molecular insights of other E3 ubiquitin ligases, such as F-box proteins, in cardiovascular disease development and malignant progression are described. Furthermore, we illustrate several compounds that alter the expression of E3 ubiquitin ligases to alleviate cardiovascular diseases. Therefore, modulation of E3 ubiquitin ligases could be a novel and promising strategy for improvement of therapeutic efficacy of deteriorative cardiovascular diseases.

PHB2 promotes SHIP2 ubiquitination via the E3 ligase NEDD4 to regulate AKT signaling in gastric cancer

BACKGROUND

Prohibitin 2 (PHB2) exhibits opposite functions of promoting or inhibiting tumour across various cancer types. In this study, we aim to investigate its functions and underlying mechanisms in the context of gastric cancer (GC).

METHODS

PHB2 protein expression levels in GC and normal tissues were examined using western blot and immunohistochemistry. PHB2 expression level associations with patient outcomes were examined through Kaplan-Meier plotter analysis utilizing GEO datasets (GSE14210 and GSE29272). The biological role of PHB2 and its subsequent regulatory mechanisms were elucidated in vitro and in vivo. GC cell viability and proliferation were assessed using MTT cell viability analysis, clonogenic assays, and BrdU incorporation assays, while the growth of GC xenografted tumours was measured via IHC staining of Ki67. The interaction among PHB2 and SHIP2, as well as between SHIP2 and NEDD4, was identified through co-immunoprecipitation, GST pull-down assays, and deletion-mapping experiments. SHIP2 ubiquitination and degradation were assessed using cycloheximide treatment, plasmid transfection and co-immunoprecipitation, followed by western blot analysis.

RESULTS

Our analysis revealed a substantial increase in PHB2 expression in GC tissues compared to adjacent normal tissues. Notably, higher PHB2 levels correlated with poorer patient outcomes, suggesting its clinical relevance. Functionally, silencing PHB2 in GC cells significantly reduced cell proliferation and retarded GC tumour growth, whereas overexpression of PHB2 further enhanced GC cell proliferation. Mechanistically, PHB2 physically interacted with Src homology 2-containing inositol 5-phosphatase 2 (SHIP2) in the cytoplasm of GC cells, thus leading to SHIP2 degradation via its novel E3 ligase NEDD4. It subsequently activated the PI3K/Akt signaling pathway and thus promoted GC cell proliferation.

CONCLUSIONS

Our findings highlight the importance of PHB2 upregulation in driving GC progression and its association with adverse patient outcomes. Understanding the functional impact of PHB2 on GC growth contributes valuable insights into the molecular underpinnings of GC and may pave the way for the development of targeted therapies to improve patient outcomes.

Deciphering roles of protein post-translational modifications in IgA nephropathy progression and potential therapy

Immunoglobulin A nephropathy (IgAN), one type of glomerulonephritis, displays the accumulation of glycosylated IgA in the mesangium. Studies have demonstrated that both genetics and epigenetics play a pivotal role in the occurrence and progression of IgAN. Post-translational modification (PTM) has been revealed to critically participate in IgAN development and progression because PTM dysregulation results in impaired degradation of proteins that regulate IgAN pathogenesis. A growing number of studies identify that PTMs, including sialylation, o-glycosylation, galactosylation, phosphorylation, ubiquitination and deubiquitination, modulate the initiation and progression of IgAN. Hence, in this review, we discuss the functions and mechanisms of PTMs in regulation of IgAN. Moreover, we outline numerous compounds that govern PTMs and attenuate IgAN progression. Targeting PTMs might be a useful strategy to ameliorate IgAN.

Physiological Functions of the Ubiquitin Ligases Nedd4-1 and Nedd4-2

The Nedd4 family of E3 ubiquitin ligases, consisting of a C2-WW(n)-HECT domain architecture, includes the closely related Nedd4/Nedd4-1 and Nedd4L/Nedd4-2, which play critical roles in human physiology and pathophysiology.This review focuses on the regulation of enzymatic activity of these Nedd4 proteins, as well as on their roles in regulating stability and function of membrane and other signaling proteins, such as ion channels, ion transporters, and growth factor receptors. The diseases caused by impairment of such regulation are discussed, as well as opportunities and challenges for targeting these enzymes for therapy.

NEDD4L Promotes IB Ubiquitination and Degradation in the Pathogenesis of Diabetic Retinopathy

PURPOSE

The dysregulation of NF-κB signaling activity plays an important role in the pathogenesis of diabetic retinopathy (DR). This study explored the association between NEDD4L and IκBα in DR.

METHODS

The rat model of diabetes was established and altered retinal vascular permeability in these rats was examined through an Evans blue dye assay. A range of glucose concentrations were used to treat retinal vascular endothelial cells (RVECs). The cells viability and apoptosis were assessed through MTT and flow cytometry, while shifts in cell permeability were examined by transendothelial resistance (TEER) and FITC dextran assay. The interaction of NEDD4L and IκBα was tested by Co-IP, while mRNA and protein levels were assessed via qPCR and Western blotting, respectively.

RESULTS

High glucose suppressed proliferative activity of RVECs, and promoted apoptosis and the protein level of NEDD4L and NF-κB p65, but decreased IκBα. NEDD4L knockdown reversed the changes in inflammation, oxidative stress, and permeability in RVECs exposed to high glucose. Similarly, NEDD4L silencing reverted observed TEER decreases, increased monolayer permeability to FITC dextran, and ZO-1 and Claudin-5 downregulation in response to high glucose. Conversely, the impact of NEDD4L overexpression was reversed by the NF-κB inhibitor PDTC treatment. NEDD4L induced the ubiquitination of IκBα in an IKK-2-dependent manner. Moreover, siNEDD4L treatment alleviated the symptoms of DR through the inactivation of NF-κB signaling in vivo.

CONCLUSIONS

NEDD4L could enhance inflammation, oxidative stress, and permeability in the retinal vascular endothelium by facilitating the ubiquitination of IκBα in an IKK-2-dependent manner. Our results support a role for NEDD4L in the pathogenesis of DR.

Ubiquitin ligase NEDD4 promotes the proliferation of hepatocellular carcinoma cells through targeting PCDH17 protein for ubiquitination and degradation

Neural precursor cell expressed developmentally downregulated 4 (NEDD4), an E3 ubiquitin ligase, is commonly upregulated in human hepatocellular carcinoma (HCC) and functions as an oncogenic factor in the progression of HCC, but the molecular mechanism needs be further explored. In this study, we found that NEDD4 could facilitate the proliferation of HCC cells, which was associated with regulating the ERK signaling. Further investigation showed that protocadherin 17 (PCDH17) was a potential substrate of NEDD4, and restoration of PCDH17 could block the facilitation of ERK signaling and HCC cells proliferation induced by NEDD4 overexpression. Whereafter, we confirmed that NEDD4 interacted with PCDH17 and promoted the Lys33-linked polyubiquitination and degradation of it via the proteasome pathway. Finally, NEDD4 protein level was found to be inversely correlated with that of PCDH17 in human HCC tissues. In conclusion, these results suggest that NEDD4 acts as an E3 ubiquitin ligase for PCDH17 ubiquitination and degradation thereby promoting the proliferation of HCC cells through regulating the ERK signaling, which may provide novel evidence for NEDD4 to be a promising therapeutic target for HCC.

The E3 ubiquitin ligase NEDD4 regulates chemoresistance to 5-fluorouracil in colorectal cancer cells by altering JNK signalling

Colorectal cancer (CRC) is the second leading cause of cancer deaths. Though chemotherapy is the main treatment option for advanced CRC, patients invariably acquire resistance to chemotherapeutic drugs and fail to respond to the therapy. Although understanding the mechanisms regulating chemoresistance has been a focus of intense research to manage this challenge, the pathways governing resistance to drugs are poorly understood. In this study, we provide evidence for the role of ubiquitin ligase NEDD4 in resistance developed against the most commonly used CRC chemotherapeutic drug 5-fluorouracil (5-FU). A marked reduction in NEDD4 protein abundance was observed in a panel of CRC cell lines and patient-derived xenograft samples that were resistant to 5-FU. Knockout of NEDD4 in CRC cells protected them from 5-FU-mediated apoptosis but not oxaliplatin or irinotecan. Furthermore, NEDD4 depletion in CRC cells reduced proliferation, colony-forming abilities and tumour growth in mice. Follow-up biochemical analysis highlighted the inhibition of the JNK signalling pathway in NEDD4-deficient cells. Treatment with the JNK activator hesperidin in NEDD4 knockout cells sensitised the CRC cells against 5-FU. Overall, we show that NEDD4 regulates cell proliferation, colony formation, tumour growth and 5-FU chemoresistance in CRC cells.

CDC20 promotes radioresistance of prostate cancer by activating Twist1 expression

Currently, radiotherapy is one of the most attractive treatments for prostate cancer (PCa) patients. However, radioresistance remains a challenging issue and the underlying mechanism is unknown. Growing evidence has demonstrated that CDC20 (Cell division cycle protein 20) plays a pivotal role in a variety of tumors, including PCa. Here, GEPIA database mining and western blot analysis showed that higher expression of CDC20 was observed in PCa tissues and cells. We demonstrated that the expression of CDC20 was increased in PCa cells by irradiation, and knockdown of CDC20 resulted in inhibition of cell proliferation, migration, tumor formation, induced cell apoptosis and increased radiosensitivity in PCa in vitro and in vivo. Furthermore, we observed that CDC20 regulated Twist1 pathway, influencing cell proliferation and migration. These results suggest that targeting CDC20 and Twist1 may be an effective way to improve the radiosensitivity of PCa.

NEDD4L in human tumors: regulatory mechanisms and dual effects on anti-tumor and pro-tumor

Tumorigenesis and tumor development are closely related to the abnormal regulation of ubiquitination. Neural precursor cell expressed developmentally downregulated 4-like (NEDD4L), an E3 ubiquitin ligase critical to the ubiquitination process, plays key roles in the regulation of cancer stem cells, as well as tumor cell functions, including cell proliferation, apoptosis, cell cycle regulation, migration, invasion, epithelial-mesenchymal transition (EMT), and tumor drug resistance, by controlling subsequent protein degradation through ubiquitination. NEDD4L primarily functions as a tumor suppressor in several tumors but also plays an oncogenic role in certain tumors. In this review, we comprehensively summarize the relevant signaling pathways of NEDD4L in tumors, the regulatory mechanisms of its upstream regulatory molecules and downstream substrates, and the resulting functional alterations. Overall, therapeutic strategies targeting NEDD4L to treat cancer may be feasible.

E3 ubiquitin ligase neural precursor cell-expressed developmentally downregulated gene 4 motivates FOXA1 ubiquitination and restrains proliferation of diffuse large B-cell lymphoma cells via the Wnt/β-Catenin pathway

Neural precursor cell-expressed developmentally downregulated gene 4 (NEDD4) is an E3 ubiquitin ligase that recognizes substrates via protein-protein interactions and takes part in tumor development. This study aims to clarify NEDD4's functions in diffuse large B-cell lymphoma (DLBCL) and its downstream mechanisms. Collection of 53 DLBCL tissues and adjacent normal lymphoid tissues, and detection of NEDD4 and Forkhead box protein A1 (FOXA1) in the tissues were conducted. The selection of DLBCL cells was for FARAGE, and test of cells' advancement was after transfection. Analysis of NEDD4 and FOXA1's link, and test of Wnt/β-catenin pathway were implemented. In vivo tumor xenograft experiments were put into effect. Detection of the pathological conditions of tumor tissues and the positive Ki67 in the family was implemented. It came out NEDD4 was reduced in DLBCL tissues and cell lines, and FOXA1 was elevated; Enhancing NEDD4 or repressing FOXA1 refrained DLBCL cells' advancement; NEDD4 could combine with FOXA1 and trigger its ubiquitination and degradation; NEDD4 inactivates the Wnt/β-catenin pathway by motivating FOXA1 ubiquitination; NEDD4 enhancement refrained DLBCL growth in vivo. In conclusion, the E3 ubiquitin ligase NEDD4 accelerates FOXA1 ubiquitination but refrains DLBCL cell proliferation via the Wnt/β-Catenin pathway.

Oncogenic Role of the NFATC2/NEDD4/FBP1 Axis in Cholangiocarcinoma

Nuclear factor of activated T cells 2 (NFATC2) is reported to contribute to the initiation and progression of various cancers; however, its expression and function in cholangiocarcinoma (CCA) tissues remain elusive. Herein, we investigated the expression pattern, clinicopathologic characteristics, cell biological functions, and potential mechanisms of NFATC2 in CCA tissues. Real-time reverse-transcription PCR (RT-qPCR) and immunohistochemistry were performed to analyze the expression of NFATC2 in human CCA tissues. Cell counting kit 8, colony formation, flow cytometry, Western blotting, and Transwell assays, and in vivo xenograft and pulmonary metastasis models, were used to explore the effect of NFATC2 on the proliferation and metastasis of CCA. A dual-luciferase reporter system, oligonucleotide pull-down, chromatin immunoprecipitation, immunofluorescence, and coimmunoprecipitation were performed to reveal the potential mechanisms. We found that NFATC2 was upregulated in CCA tissues and cells, and its aberrantly high levels were associated with a poorer differentiation pattern. Functionally, NFATC2 overexpression promoted CCA cell proliferation and metastasis, whereas knockdown of NFATC2 led to opposite result. Mechanistically, NFATC2 could be enriched in the promoter region of neural precursor cell-expressed developmentally downregulated protein 4 (NEDD4) to facilitate its expression. Furthermore, NEDD4 targeted fructose-1, 6-bisphosphatase 1 (FBP1) and inhibited FBP1 expression via ubiquitination. In addition, silencing NEDD4 rescued the effects of NFATC2 overexpression on CCA cells. NEDD4 was upregulated in human CCA tissues, and its expression levels were positively correlated with those of NFATC2. We thus conclude that NFATC2 promotes the progression of CCA via the NEDD4/FBP1 axis, emphasizing the oncogenic role of NFATC2 in CCA progression.

Ubiquitin Engineering for Interrogating the Ubiquitin-Proteasome System and Novel Therapeutic Strategies

Protein turnover, a highly regulated process governed by the ubiquitin-proteasome system (UPS), is essential for maintaining cellular homeostasis. Dysregulation of the UPS has been implicated in various diseases, including viral infections and cancer, making the proteins in the UPS attractive targets for therapeutic intervention. However, the functional and structural redundancies of UPS enzymes present challenges in identifying precise drug targets and achieving target selectivity. Consequently, only 26S proteasome inhibitors have successfully advanced to clinical use thus far. To overcome these obstacles, engineered peptides and proteins, particularly engineered ubiquitin, have emerged as promising alternatives. In this review, we examine the impact of engineered ubiquitin on UPS and non-UPS proteins, as well as on viral enzymes. Furthermore, we explore their potential to guide the development of small molecules targeting novel surfaces, thereby expanding the range of druggable targets.

E3 Ubiquitin Ligases in Endothelial Dysfunction and Vascular Diseases: Roles and Potential Therapies

ABSTRACT

Ubiquitin E3 ligases are a structurally conserved family of enzymes that exert a variety of regulatory functions in immunity, cell death, and tumorigenesis through the ubiquitination of target proteins. Emerging evidence has shown that E3 ubiquitin ligases play crucial roles in the pathogenesis of endothelial dysfunction and related vascular diseases. Here, we reviewed the new findings of E3 ubiquitin ligases in regulating endothelial dysfunction, including endothelial junctions and vascular integrity, endothelial activation, and endothelial apoptosis. The critical role and potential mechanism of E3 ubiquitin ligases in vascular diseases, such as atherosclerosis, diabetes, hypertension, pulmonary hypertension, and acute lung injury, were summarized. Finally, the clinical significance and potential therapeutic strategies associated with the regulation of E3 ubiquitin ligases were also proposed.

Elucidating the role of ubiquitination and deubiquitination in osteoarthritis progression

Osteoarthritis is non-inflammatory degenerative joint arthritis, which exacerbates disability in elder persons. The molecular mechanisms of osteoarthritis are elusive. Ubiquitination, one type of post-translational modifications, has been demonstrated to accelerate or ameliorate the development and progression of osteoarthritis via targeting specific proteins for ubiquitination and determining protein stability and localization. Ubiquitination process can be reversed by a class of deubiquitinases via deubiquitination. In this review, we summarize the current knowledge regarding the multifaceted role of E3 ubiquitin ligases in the pathogenesis of osteoarthritis. We also describe the molecular insight of deubiquitinases into osteoarthritis processes. Moreover, we highlight the multiple compounds that target E3 ubiquitin ligases or deubiquitinases to influence osteoarthritis progression. We discuss the challenge and future perspectives via modulation of E3 ubiquitin ligases and deubiquitinases expression for enhancement of the therapeutic efficacy in osteoarthritis patients. We conclude that modulating ubiquitination and deubiquitination could alleviate the osteoarthritis pathogenesis to achieve the better treatment outcomes in osteoarthritis patients.

Expression and regulatory network of E3 ubiquitin ligase NEDD4 family in cancers

NEDD4 family represent an important group of E3 ligases, which regulate various cellular pathways of cell proliferation, cell junction and inflammation. Emerging evidence suggested that NEDD4 family members participate in the initiation and development of tumor. In this study, we systematically investigated the molecular alterations as well as the clinical relevance regarding NEDD4 family genes in 33 cancer types. Finally, we found that NEDD4 members showed increased expression in pancreas cancer and decreased expression in thyroid cancer. NEDD4 E3 ligase family genes had an average mutation frequency in the range of 0-32.1%, of which HECW1 and HECW2 demonstrated relatively high mutation rate. Breast cancer harbors large amount of NEDD4 copy number amplification. NEDD4 family members interacted proteins were enriched in various pathways including p53, Akt, apoptosis and autophagy, which were confirmed by further western blot and flow cytometric analysis in A549 and H1299 lung cancer cells. In addition, expression of NEDD4 family genes were associated with survival of cancer patients. Our findings provide novel insight into the effect of NEDD4 E3 ligase genes on cancer progression and treatment in the future.

Ubiquitination Links DNA Damage and Repair Signaling to Cancer Metabolism

Changes in the DNA damage response (DDR) and cellular metabolism are two important factors that allow cancer cells to proliferate. DDR is a set of events in which DNA damage is recognized, DNA repair factors are recruited to the site of damage, the lesion is repaired, and cellular responses associated with the damage are processed. In cancer, DDR is commonly dysregulated, and the enzymes associated with DDR are prone to changes in ubiquitination. Additionally, cellular metabolism, especially glycolysis, is upregulated in cancer cells, and enzymes in this metabolic pathway are modulated by ubiquitination. The ubiquitin-proteasome system (UPS), particularly E3 ligases, act as a bridge between cellular metabolism and DDR since they regulate the enzymes associated with the two processes. Hence, the E3 ligases with high substrate specificity are considered potential therapeutic targets for treating cancer. A number of small molecule inhibitors designed to target different components of the UPS have been developed, and several have been tested in clinical trials for human use. In this review, we discuss the role of ubiquitination on overall cellular metabolism and DDR and confirm the link between them through the E3 ligases NEDD4, APC/C^CDH1, FBXW7, and Pellino1. In addition, we present an overview of the clinically important small molecule inhibitors and implications for their practical use.

The role of E3 ubiquitin ligases and deubiquitinases in bladder cancer development and immunotherapy

Bladder cancer is one of the common malignant urothelial tumors. Post-translational modification (PTMs), including ubiquitination, acetylation, methylation, and phosphorylation, have been revealed to participate in bladder cancer initiation and progression. Ubiquitination is the common PTM, which is conducted by E1 ubiquitin-activating enzyme, E2 ubiquitin-conjugating enzyme and E3 ubiquitin-protein ligase. E3 ubiquitin ligases play a key role in bladder oncogenesis and progression and drug resistance in bladder cancer. Therefore, in this review, we summarize current knowledge regarding the functions of E3 ubiquitin ligases in bladder cancer development. Moreover, we provide the evidence of E3 ubiquitin ligases in regulation of immunotherapy in bladder cancer. Furthermore, we mention the multiple compounds that target E3 ubiquitin ligases to improve the therapy efficacy of bladder cancer. We hope our review can stimulate researchers and clinicians to investigate whether and how targeting E3 ubiquitin ligases acts a novel strategy for bladder cancer therapy.

Divergent acute versus prolonged pharmacological GLP-1R responses in adult β cell-specific β-arrestin 2 knockout mice

The glucagon-like peptide-1 receptor (GLP-1R) is a major type 2 diabetes therapeutic target. Stimulated GLP-1Rs are rapidly desensitized by β-arrestins, scaffolding proteins that not only terminate G protein interactions but also act as independent signaling mediators. Here, we have assessed in vivo glycemic responses to the pharmacological GLP-1R agonist exendin-4 in adult β cell-specific β-arrestin 2 knockout (KO) mice. KOs displayed a sex-dimorphic phenotype consisting of weaker acute responses that improved 6 hours after agonist injection. Similar effects were observed for semaglutide and tirzepatide but not with biased agonist exendin-phe1. Acute cyclic adenosine 5'-monophosphate increases were impaired, but desensitization reduced in KO islets. The former defect was attributed to enhanced β-arrestin 1 and phosphodiesterase 4 activities, while reduced desensitization co-occurred with impaired GLP-1R recycling and lysosomal targeting, increased trans-Golgi network signaling, and reduced GLP-1R ubiquitination. This study has unveiled fundamental aspects of GLP-1R response regulation with direct application to the rational design of GLP-1R-targeting therapeutics.

Association of rare, recurrent nonsynonymous variants in the germline of prostate cancer patients of African ancestry

BACKGROUND

Although men of African ancestry (AA) have the highest mortality rate from prostate cancer (PCa), relatively little is known about the germline variants that are associated with PCa risk in AA men. The goal of this study is to systematically evaluate rare, recurrent nonsynonymous variants across the exome for their association with PCa in AA men.

METHODS

Whole exome sequencing (WES) of germline DNA in two AA PCa patient cohorts of Johns Hopkins Hospital (N = 960) and Wayne State University (N = 747) was performed. All nonsynonymous variants present in both case cohorts, with a carrier rate between 0.5% and 1%, were identified. Their carrier rates were compared with rates from 8128 African/African American (AFR) control subjects from The Genome Aggregation Database (gnomAD) using Fisher's exact test. Significant variants, defined as false discovery rate (FDR) adjusted p-value ≤ 0.05, were further evaluated in AA PCa cases (N = 132) and controls (N = 1184) from the UK Biobank (UKB).

RESULTS

Two variants reached a pre-specified statistical significance level. The first was p.R14Q in GPRC5C (found in 0.47% of PCa cases and 0.01% of population controls); odds ratio (OR) for PCa was 37.46 (95% confidence interval CI 4.68-299.72), p_exact  = 7.01E-06, FDR-adjusted p-value = 0.05. The second was p.R511Q in IGF1R (found in 0.53% of PCa cases and 0.01% of population controls); OR for PCa was 21.54 (95%CI 4.65-99.76), p_exact  = 5.51E-06, FDR-adjusted p-value = 0.05. The mean percentage of African ancestry was similar between variant carriers and noncarriers of each variant, p > 0.05. In the UKB AA men, GPRC5C R14Q was 0.76% and 0.08% in cases and controls, respectively, OR for PCa was 9.00 (95%CI 0.56-145.23), p_exact  = 0.19. However, IGF1R R511Q was not found in cases or controls.

CONCLUSIONS

This WES study identified two rare, recurrent nonsynonymous PCa risk-associated variants in AA. Confirmation in additional large populations of AA PCa cases and controls is required.

Exploiting E3 ubiquitin ligases to reeducate the tumor microenvironment for cancer therapy

Tumor development relies on a complex and aberrant tissue environment in which cancer cells receive the necessary nutrients for growth, survive through immune escape, and acquire mesenchymal properties that mediate invasion and metastasis. Stromal cells and soluble mediators in the tumor microenvironment (TME) exhibit characteristic anti-inflammatory and protumorigenic activities. Ubiquitination, which is an essential and reversible posttranscriptional modification, plays a vital role in modulating the stability, activity and localization of modified proteins through an enzymatic cascade. This review was motivated by accumulating evidence that a series of E3 ligases and deubiquitinases (DUBs) finely target multiple signaling pathways, transcription factors and key enzymes to govern the functions of almost all components of the TME. In this review, we systematically summarize the key substrate proteins involved in the formation of the TME and the E3 ligases and DUBs that recognize these proteins. In addition, several promising techniques for targeted protein degradation by hijacking the intracellular E3 ubiquitin-ligase machinery are introduced.

E3 Ligases Meet Their Match: Fragment-Based Approaches to Discover New E3 Ligands and to Unravel E3 Biology

Ubiquitination is a key post-translational modification of proteins, affecting the regulation of multiple cellular processes. Cells are equipped with over 600 ubiquitin orchestrators, called E3 ubiquitin ligases, responsible for directing the covalent attachment of ubiquitin to substrate proteins. Due to their regulatory role in cells, significant efforts have been made to discover ligands for E3 ligases. The recent emergence of the proteolysis targeting chimera (PROTAC) and molecular glue degrader (MGD) modalities has further increased interest in E3 ligases as drug targets. This perspective focuses on how fragment based lead discovery (FBLD) methods have been used to discover new ligands for this important target class. In some cases these efforts have led to clinical candidates; in others, they have provided tools for deepening our understanding of E3 ligase biology. Recently, FBLD-derived ligands have inspired the design of PROTACs that are able to artificially modulate protein levels in cells.

TMEPAI promotes degradation of the NF-κB signaling pathway inhibitory protein IκBα and contributes to tumorigenesis

The transmembrane prostate androgen-induced protein (TMEPAI) is known to be highly expressed in various types of cancer and promoted oncogenic abilities. However, the mechanisms whereby TMEPAI facilitates tumorigenesis are not fully understood. Here we reported that expression of TMEPAI activated the NF-κB signaling. TMEPAI showed direct interaction with NF-κB pathway inhibitory protein IκBα. Though ubiquitin ligase Nedd4 (neural precursor cell expressed, developmentally down-regulated 4) did not interact with IκBα directly, TMEPAI recruited Nedd4 for ubiquitination of IκBα, leading to IκBα degradation through the proteasomal and lysosomal pathway, and promoted activation of NF-κB signaling. Further study indicated NF-κB signaling is involved in TMEPAI-induced cell proliferation and tumor growth in immune deficient mice. This finding helps to further understand the mechanism of TMEPAI on tumorigenesis and suggests TMEPAI is potential target for cancer treatment.

The role of the NDRG1 in the pathogenesis and treatment of breast cancer

Breast cancer (BC) is the leading cause of cancer death in women. This disease is heterogeneous, with clinical subtypes being estrogen receptor-α (ER-α) positive, having human epidermal growth factor receptor 2 (HER2) overexpression, or being triple-negative for ER-α, progesterone receptor, and HER2 (TNBC). The ER-α positive and HER2 overexpressing tumors can be treated with agents targeting these proteins, including tamoxifen and pertuzumab, respectively. Despite these treatments, resistance and metastasis are problematic, while TNBC is challenging to treat due to the lack of suitable targets. Many studies examining BC and other tumors indicate a role for N-myc downstream-regulated gene-1 (NDRG1) as a metastasis suppressor. The ability of NDRG1 to inhibit metastasis is due, in part, to the inhibition of the initial step in metastasis, namely the epithelial-to-mesenchymal transition. Paradoxically, there are also reports of NDRG1 playing a pro-oncogenic role in BC pathogenesis. The oncogenic effects of NDRG1 in BC have been reported to relate to lipid metabolism or the mTOR signaling pathway. The molecular mechanism(s) of how NDRG1 regulates the activity of multiple signaling pathways remains unclear. Therapeutic strategies that up-regulate NDRG1 have been developed and include agents of the di-2-pyridylketone thiosemicarbazone class. These compounds target oncogenic drivers in BC cells, suppressing the expression of multiple key hormone receptors including ER-α, progesterone receptor, androgen receptor, and prolactin receptor, and can also overcome tamoxifen resistance. Considering the varying role of NDRG1 in BC pathogenesis, further studies are required to examine what subset of BC patients would benefit from pharmacopeia that up-regulate NDRG1.

The Role of HECT E3 Ubiquitin Ligases in Colorectal Cancer

Colorectal cancer (CRC) is estimated to rank as the second reason for cancer-related deaths, and the prognosis of CRC patients remains unsatisfactory. Numerous studies on gastrointestinal cell biology have shown that the E3 ligase-mediated ubiquitination exerts key functions in the pathogenesis of CRC. The homologous to E6-associated protein C-terminus (HECT) family E3 ligases are a major group of E3 enzymes, featured with the presence of a catalytic HECT domain, which participate in multiple cellular processes; thus, alterations in HECT E3 ligases in function or expression are closely related to the occurrence and development of many human malignancies, including-but not limited to-CRC. In this review, we summarize the potential role of HECT E3 ligases in colorectal carcinogenesis and the related underlying molecular mechanism to expand our understanding of their pathological functions. Exploiting specific inhibitors targeting HECT E3 ligases could be a potential therapeutic strategy for CRC therapy in the future.

Emerging roles of the HECT E3 ubiquitin ligases in gastric cancer

Gastric cancer (GC) is one of the most pernicious gastrointestinal tumors with extraordinarily high incidence and mortality. Ubiquitination modification of cellular signaling proteins has been shown to play important roles in GC tumorigenesis, progression, and prognosis. The E3 ubiquitin ligase is the crucial enzyme in the ubiquitination reaction and determines the specificity of ubiquitination substrates, and thus, the cellular effects. The HECT E3 ligases are the second largest E3 ubiquitin ligase family characterized by containing a HECT domain that has E3 ubiquitin ligase activity. The HECT E3 ubiquitin ligases have been found to engage in GC progression. However, whether HECT E3 ligases function as tumor promoters or tumor suppressors in GC remains controversial. In this review, we will focus on recent discoveries about the role of the HECT E3 ubiquitin ligases, especially members of the NEDD4 and other HECT E3 ligase subfamilies, in GC.

hCINAP regulates the differentiation of embryonic stem cells by regulating NEDD4 liquid-liquid phase-separation-mediated YAP1 activation

YAP1 functions in lineage differentiation of pluripotent embryonic stem cells (ESCs); however, the detailed mechanisms underlying the regulation of YAP1 activity during ESC differentiation remain elusive. Here, we report that hCINAP serves as a negative regulator of YAP1 during ESC fate decisions. The expression of mCINAP, the murine homolog of hCINAP, is downregulated during the differentiation process of murine ESC (mESC) ectoderm lineage, leading to liquid-liquid phase separation (LLPS) of NEDD4 and activation of YAP1. Mechanistically, hCINAP interacts with and prevents NEDD4 from forming cytoplasmic condensates that compartmentalize YAP1 and its kinase NLK, facilitating YAP1 phosphorylation at Ser128 and promoting YAP1 activation. mCINAP depletion leads to the formation of NEDD4 condensates and YAP1 activation, which impedes endoderm differentiation of mESCs. Our study shows that hCINAP is a vital regulator of YAP1 activity and is essential for stem cell fate decisions, which provides mechanistic insight into early embryogenesis.

The E3 ubiquitin ligases regulate PD-1/PD-L1 protein levels in tumor microenvironment to improve immunotherapy

The tumor microenvironment (TME) is the tumor surrounding environment, which is critical for tumor development and progression. TME is also involved in clinical intervention and treatment outcomes. Modulation of TME is useful for improving therapy strategies. PD-L1 protein on tumor cells interacts with PD-1 protein on T cells, contributing to T cell dysfunction and exhaustion, blockage of the immune response. Evidence has demonstrated that the expression of PD-1/PD-L1 is associated with clinical response to anti-PD-1/PD-L1 therapy in cancer patients. It is important to discuss the regulatory machinery how PD-1/PD-L1 protein is finely regulated in tumor cells. In recent years, studies have demonstrated that PD-1/PD-L1 expression was governed by various E3 ubiquitin ligases in TME, contributing to resistance of anti-PD-1/PD-L1 therapy in human cancers. In this review, we will discuss the role and molecular mechanisms of E3 ligases-mediated regulation of PD-1 and PD-L1 in TME. Moreover, we will describe how E3 ligases-involved PD-1/PD-L1 regulation alters anti-PD-1/PD-L1 efficacy. Altogether, targeting E3 ubiquitin ligases to control the PD-1/PD-L1 protein levels could be a potential strategy to potentiate immunotherapeutic effects in cancer patients.

NEDD4 attenuates oxidized low‑density lipoprotein‑induced inflammation and dysfunction in vascular endothelial cells via regulating APEX1 expression

Atherosclerosis chiefly results from inflammation as well as vascular endothelial cell dysfunction. Methylation levels of neuronally expressed developmentally downregulated 4 (NEDD4) were found to be fortified in atherosclerosis patients and NEDD4 deficiency enhanced vascular calcification. However, the exact function of NEDD4 in inflammation and vascular endothelial dysfunction remains to be elucidated. In the present study, CCK-8 assay was used to estimate cell viability. Reverse transcription-quantitative PCR was adopted to examine the expression of NEDD4, inflammation-associated enzymes and apurinic/apyrimidinic endodeoxyribonuclease 1 (APEX1). Western blotting was used to test NEDD4, endothelial nitric oxide synthase, inducible nitric oxide synthase and APEX1 protein levels. Cytotoxicity was detected by a lactate dehydrogenase (LDH) kit. Reactive oxygen species level was tested by a corresponding kit. Vascular cell adhesion molecule 1 and intercellular adhesion molecule 1 contents were examined with ELISA. Cell adhesion assays evaluated the adhesion of endothelial cells. Co-immunoprecipitation assay was used to test the relationship between NEDD4 and APEX1. The data revealed that NEDD4 expression rapidly declined in oxidized low density lipoprotein (ox-LDL)-induced human umbilical vein endothelial cells (HUVECs). Following NEDD4 overexpression, the active damage, inflammatory release and endothelial cell dysfunction in ox-LDL-induced HUVECs were attenuated. After co-transfection of APEX1 interference plasmids and NEDD4 overexpression plasmids, cell damage, inflammatory release and endothelial cell dysfunction in ox-LDL-induced HUVECs were improved again. Taken together, NEDD4 attenuated ox-LDL-induced inflammation and endothelial dysfunction by regulating APEX1 expression.

Methods to Evaluate the Effects of HAT/KAT Inhibition on SIAH2-Driven Reactive Oxygen Species Generation in Helicobacter pylori-Infected Gastric Epithelial Cells

Helicobacter pylori infection is one of the leading factors that promotes, among other diseases, gastric cancer (GC). Infection of gastric epithelial cells (GECs) by H. pylori enhances the expression as well as acetylation of the E3 ubiquitin ligase SIAH2 which promotes GC progression. The histone acetyltransferase (HAT) activity of p300 catalyzes SIAH2 acetylation following H. pylori infection. Since reactive oxygen species (ROS) generation in H. pylori-infected GECs accelerates GC progression, acetylation-mediated SIAH2 regulation might be a crucial modifier of ROS generation in the infected GECs. Here, we describe a compendium of methods to evaluate the effects of HAT/lysine acetyl transferase (KAT) inhibitors (HAT/KATi) on SIAH2-mediated ROS regulation in H. pylori-infected GECs.

The E3 ubiquitin ligase NEDD4-1 protects against acetaminophen-induced liver injury by targeting VDAC1 for degradation

Acetaminophen (APAP) overdose is a major cause of liver injury. Neural precursor cell expressed developmentally downregulated 4-1 (NEDD4-1) is an E3 ubiquitin ligase that has been implicated in the pathogenesis of numerous liver diseases; however, its role in APAP-induced liver injury (AILI) is unclear. Thus, this study aimed to investigate the role of NEDD4-1 in the pathogenesis of AILI. We found that NEDD4-1 was dramatically downregulated in response to APAP treatment in mouse livers and isolated mouse hepatocytes. Hepatocyte-specific NEDD4-1 knockout exacerbated APAP-induced mitochondrial damage and the resultant hepatocyte necrosis and liver injury, while hepatocyte-specific NEDD4-1 overexpression mitigated these pathological events both in vivo and in vitro. Additionally, hepatocyte NEDD4-1 deficiency led to marked accumulation of voltage-dependent anion channel 1 (VDAC1) and increased VDAC1 oligomerization. Furthermore, VDAC1 knockdown alleviated AILI and weakened the exacerbation of AILI caused by hepatocyte NEDD4-1 deficiency. Mechanistically, NEDD4-1 was found to interact with the PPTY motif of VDAC1 through its WW domain and regulate K48-linked ubiquitination and degradation of VDAC1. Our present study indicates that NEDD4-1 is a suppressor of AILI and functions by regulating the degradation of VDAC1.

Targeting CSC-related transcription factors by E3 ubiquitin ligases for cancer therapy

Evidence has revealed that transcription factors play essential roles in regulation of multiple cellular processes, including cell proliferation, metastasis, EMT, cancer stem cells and chemoresistance. Dysregulated expression levels of transcription factors contribute to tumorigenesis and malignant progression. The expression of transcription factors is tightly governed by several signaling pathways, noncoding RNAs and E3 ubiquitin ligases. Cancer stem cells (CSCs) have been validated in regulation of tumor metastasis, reoccurrence and chemoresistance in human cancer. Transcription factors have been verified to participate in regulation of CSC formation, including Oct4, SOX2, KLF4, c-Myc, Nanog, GATA, SALL4, Bmi-1, OLIG2, POU3F2 and FOX proteins. In this review article, we will describe the critical role of CSC-related transcription factors. We will further discuss which E3 ligases regulate the degradation of these CSC-related transcription factors and their underlying mechanisms. We also mentioned the functions and mechanisms of EMT-associated transcription factors such as ZEB1, ZEB2, Snail, Slug, Twist1 and Twist2. Furthermore, we highlight the therapeutic potential via targeting E3 ubiquitin ligases for modulation of these transcription factors.

The HERC proteins and the nervous system

The HERC protein family is one of three subfamilies of Homologous to E6AP C-terminus (HECT) E3 ubiquitin ligases. Six HERC genes have been described in humans, two of which encode Large HERC proteins -HERC1 and HERC2- with molecular weights above 520 kDa that are constitutively expressed in the brain. There is a large body of evidence that mutations in these Large HERC genes produce clinical syndromes in which key neurodevelopmental events are altered, resulting in intellectual disability and other neurological disorders like epileptic seizures, dementia and/or signs of autism. In line with these consequences in humans, two mice carrying mutations in the Large HERC genes have been studied quite intensely: the tambaleante mutant for Herc1 and the Herc2^+/530 mutant for Herc2. In both these mutant mice there are clear signs that autophagy is dysregulated, eliciting cerebellar Purkinje cell death and impairing motor control. The tambaleante mouse was the first of these mice to appear and is the best studied, in which the Herc1 mutation elicits: (i) delayed neural transmission in the peripheral nervous system; (ii) impaired learning, memory and motor control; and (iii) altered presynaptic membrane dynamics. In this review, we discuss the information currently available on HERC proteins in the nervous system and their biological activity, the dysregulation of which could explain certain neurodevelopmental syndromes and/or neurodegenerative diseases.

Unraveling the Potential Role of NEDD4-like E3 Ligases in Cancer

Cancer is a deadly disease worldwide, with an anticipated 19.3 million new cases and 10.0 million deaths occurring in 2020 according to GLOBOCAN 2020. It is well established that carcinogenesis and cancer development are strongly linked to genetic changes and post-translational modifications (PTMs). An important PTM process, ubiquitination, regulates every aspect of cellular activity, and the crucial enzymes in the ubiquitination process are E3 ubiquitin ligases (E3s) that affect substrate specificity and must therefore be carefully regulated. A surfeit of studies suggests that, among the E3 ubiquitin ligases, neuronal precursor cell-expressed developmentally downregulated 4 (NEDD4)/NEDD4-like E3 ligases show key functions in cellular processes by controlling subsequent protein degradation and substrate ubiquitination. In addition, it was demonstrated that NEDD4 mainly acts as an oncogene in various cancers, but also plays a tumor-suppressive role in some cancers. In this review, to comprehend the proper function of NEDD4 in cancer development, we summarize its function, both its tumor-suppressive and oncogenic role, in multiple types of malignancies. Moreover, we briefly explain the role of NEDD4 in carcinogenesis and progression, including cell survival, cell proliferation, autophagy, cell migration, invasion, metastasis, epithelial-mesenchymal transition (EMT), chemoresistance, and multiple signaling pathways. In addition, we briefly explain the significance of NEDD4 as a possible target for cancer treatment. Therefore, we conclude that targeting NEDD4 as a therapeutic method for treating human tumors could be a practical possibility.

ARHGEF3 regulates the stability of ACLY to promote the proliferation of lung cancer

Rho GTPases play an essential role in many cellular processes, including cell cycle progress, cell motility, invasion, migration, and transformation. Several studies indicated that the dysregulation of Rho GTPase signaling is closely related to tumorigenesis. Rho GEFs considered being positive regulators of Rho GTPase, promoting the dissociation of Rho protein from GDP and binding to GTP, thus activating the downstream signaling pathway. Herein, we demonstrated that ARHGEF3, a member of the Rho GEFs family, played an important role in non-small cell lung cancer (NSCLC). We found that ARHGEF3 was highly expressed in non-small cell lung cancer and facilitated cancer cell proliferation of NSCLC cells in vitro and in vivo. Further studies demonstrated that ARHGEF3 enhanced the protein homeostasis of ATP-citrate lyase (ACLY) by reducing its acetylation on Lys17 and Lys86, leading to the dissociation between ACLY and its E3 ligase-NEDD4. Interestingly, this function of ARHGEF3 on the protein homeostasis of ACLY was independent of its GEF activity. Taken together, our findings uncover a novel function of ARHGEF3, suggesting that ARHGEF3 is a promising therapeutic target in non-small cell lung cancer.

An update regarding the role of WNK kinases in cancer

Mammalian WNK kinases (WNKs) are serine/threonine kinases that contain four members, WNK1-4. They function to maintain ion homeostasis and regulate blood pressure in mammals. Recent studies have revealed that the dysregulation of WNKs contributes to tumor growth, metastasis, and angiogenesis through complex mechanisms, especially through phosphorylating kinase substrates SPS1-related proline/alanine-rich kinase (SPAK) and oxidative stress-responsive kinase 1 (OSR1). Here, we review and discuss the relationships between WNKs and several key factors/biological processes in cancer, including ion channels, cation chloride cotransporters, sodium bicarbonate cotransporters, signaling pathways, angiogenesis, autophagy, and non-coding RNAs. In addition, the potential drugs for targeting WNK-SPAK/OSR1 signaling have also been discussed. This review summarizes and discusses knowledge of the roles of WNKs in cancer, which provides a comprehensive reference for future studies.

Keloid: Genetic susceptibility and contributions of genetics and epigenetics to its pathogenesis

Keloid, characterized by fibroproliferative disorders of the skin, can be developed in people of different genders, ages, and ethnicities. Keloid can appear in any part of the body but are especially common on the earlobe, upper torso, and triangular muscle. The genetic heterogeneity and susceptibility of KD (keloid) vary among different races and ethnicities. Studies have found that multiple loci on multiple chromosomes are associated with the pathogenesis of KD, and specific gene variants may also be involved. Despite multiple investigations attempting to uncover the etiology of keloid formation, the genetic mechanism of keloid formation remains unknown. To establish a foundation for a better understanding of the genetics and epigenetics of keloids, we have evaluated and summarized current studies which are mostly related to heredity, genetic polymorphisms, predisposing gene, DNA methylation, and non-coding RNA. We also discussed the problems and potential of genetic and epigenetic investigations of keloids, with the goal of developing new therapeutic approaches to enhance the prognosis of keloid patients.

NEDD4 E3 Ligases: Functions and Mechanisms in Bone and Tooth

Protein ubiquitination is a precisely controlled enzymatic cascade reaction belonging to the post-translational modification of proteins. In this process, E3 ligases catalyze the binding of ubiquitin (Ub) to protein substrates and define specificity. The neuronally expressed developmentally down-regulated 4 (NEDD4) subfamily, belonging to the homology to E6APC terminus (HECT) class of E3 ligases, has recently emerged as an essential determinant of multiple cellular processes in different tissues, including bone and tooth. Here, we place special emphasis on the regulatory role of the NEDD4 subfamily in the molecular and cell biology of osteogenesis. We elucidate in detail the specific roles, downstream substrates, and upstream regulatory mechanisms of the NEDD4 subfamily. Further, we provide an overview of the involvement of E3 ligases and deubiquitinases in the development, repair, and regeneration of another mineralized tissue—tooth.

Targeting matrix metalloproteinases by E3 ubiquitin ligases as a way to regulate the tumor microenvironment for cancer therapy

The tumor microenvironment (TME) plays an important role in neoplastic development. Matrix metalloproteinases (MMPs) are critically involved in tumorigenesis by modulation of the TME and degradation of the extracellular matrix (ECM) in a large variety of malignancies. Evidence has revealed that dysregulated MMPs can lead to ECM damage, the promotion of cell migration and tumor metastasis. The expression and activities of MMPs can be tightly regulated by TIMPs, multiple signaling pathways and noncoding RNAs. MMPs are also finely controlled by E3 ubiquitin ligases. The current review focuses on the molecular mechanism by which MMPs are governed by E3 ubiquitin ligases in carcinogenesis. Due to the essential role of MMPs in oncogenesis, they have been considered the attractive targets for antitumor treatment. Several strategies that target MMPs have been discovered, including the use of small-molecule inhibitors, peptides, inhibitory antibodies, natural compounds with anti-MMP activity, and RNAi therapeutics. However, these molecules have multiple disadvantages, such as poor solubility, severe side-effects and low oral bioavailability. Therefore, it is necessary to discover the novel inhibitors that suppress MMPs for cancer therapy. Here, we discuss the therapeutic potential of targeting E3 ubiquitin ligases to inhibit MMPs. We hope this review will stimulate the discovery of novel therapeutics for the MMP-targeted treatment of a variety of human cancers.

A SS18::NEDD4 Cutaneous Spindled and Epithelioid Sarcoma: A Hitherto Unclassified Cutaneous Sarcoma, Resembling Epithelioid Sarcoma with Aggressive Clinical Behavior

SS18::SSX gene fusions as a result of t(X,18)(p11;q11) have only been described in synovial sarcoma (SS). Recently, an SS18::NEDD4 gene fusion was identified in a single case of primary renal SS exhibiting a hypocellular and myxoid morphology. Herein, we report a case of an unclassified malignant cutaneous spindled and epithelioid neoplasm in a 60‐year‐old female that resembled an epithelioid sarcoma (ES) and harbored a rare SS18::NEDD4 gene fusion. Briefly, the patient presented with a progressively growing cutaneous mass involving the volar aspect of right hand, warranting an amputation. Histologic sections revealed a cutaneous ulcerative neoplasm composed of spindled and epithelioid cells, bearing a certain semblance to ES, with diffuse invasion into the subcutis and skeletal muscle. Coagulation tumor necrosis and mitotic figures were present. By immunohistochemistry, the tumor cells were positive for keratins (AE1/3 and cam5.2), vimentin, CMYC, BCL2, p53, smooth muscle actin (focal), and TLE1 (multifocal) and negative for p40, p63, CK5/6, CK7, CK20, CD56, CD31, CD34, ERG, desmin, SMMS, H‐Caldesmon, myogenin, and S‐100. Expression of INI1 stain was retained. The unusual histomorphology and inconclusive immunophenotypic profile lead to next‐generation sequencing identifying an SS18::NEDD4 gene fusion with genomic coordinates 5′‐SS18 (ex1‐9 NM_005637)‐NEDD4 (ex14‐29 NM_006154). Fluorescence in situ hybridization confirmed SS18 gene rearrangement. Within 2 years, the patient developed widespread metastatic disease. Despite aggressive multimodality treatment, the patient succumbed to disease. In summary, we report a unique case of previously unclassified cytokeratin positive malignant cutaneous spindled and epithelioid sarcoma with aggressive behavior, harboring an SS18::NEDD4 fusion.

Down-regulated NEDD4L facilitates tumor progression through activating Notch signaling in lung adenocarcinoma

Neural precursor cell expressed developmentally down-regulated 4-like protein (NEDD4L), an E3 ubiquitin ligase, exerts an important role in diverse biological processes including development, tumorigenesis, and tumor progression. Although the role of NEDD4L in the pathogenesis of lung adenocarcinoma (LUAD) has been described, the mechanism by which NEDD4L promotes LUAD progression remains poorly understood. In the study, the correlation between NEDD4L level and clinical outcome in LUAD patients was analysed using the data from The Cancer Genome Atlas (TCGA) database. NEDD4L expression in LUAD cell lines and tissue samples was assessed through quantitative real-time PCR (qRT-PCR). The biological function of NEDD4L on regulating LUAD cell proliferation was tested with Cell Counting Kit-8 (CCK-8) assay in vitro, and mouse xenograft tumor model in vivo. We found that NEDD4L expression was significantly decreased in LUAD tissues and cell lines. Lower expression of NEDD4L exhibited a significantly poorer overall survival. Functionally, NEDD4L knockdown in H1299 cells accelerated cell growth, whereas NEDD4L overexpression in A549 cells repressed cell proliferation. NEDD4L overexpression also inhibited tumor xenograft growth in vivo. Mechanistically, NEDD4L decreased the protein stability of notch receptor 2 (Notch2) through facilitating its ubiquitination and degradation by ubiquitin-proteasome system. Consequently, NEDD4L negatively regulated Notch signaling activation in LUAD cells, and RO4929097 (a Notch inhibitor) treatment effectively repressed the effect of NEDD4L knockdown on LUAD cell proliferation. Taken together, these results demonstrate that down-regulated NEDD4L facilitates LUAD progression by activating Notch signaling, and NEDD4L may be a promising target to treat LUAD.

NEDD4 attenuates phosgene-induced acute lung injury through the inhibition of Notch1 activation

Phosgene gas leakage can cause life-threatening acute lung injury (ALI), which is characterized by inflammation, increased vascular permeability, pulmonary oedema and oxidative stress. Although the downregulation of neuronal precursor cell-expressed developmentally downregulated 4 (NEDD4) is known to be associated with inflammation and oxidative damage, its functions in phosgene-induced ALI remain unclear. In this study, rats with phosgene-induced ALI were intravenously injected with NEDD4-overexpressing lentiviruses to determine the functions of NEDD4 in this inflammatory condition. NEDD4 expression was decreased in the lung parenchyma of phosgene-exposed control rats, whereas its expression level was high in the NEDD4-overexpressing rats. Phosgene exposure increased the wet-to-dry lung weight ratio, but NEDD4 abrogated this effect. NEDD4 overexpression attenuated phosgene-induced lung inflammation, lowering the high lung injury score (based on total protein, inflammatory cells and inflammatory factors in bronchoalveolar lavage fluid) and also reduced phosgene-induced oxidative stress and cell apoptosis. Finally, NEDD4 was found to interact with Notch1, enhancing its ubiquitination and thereby its degradation, thus attenuating the inflammatory responses to ALI. Therefore, we demonstrated that NEDD4 plays a protective role in alleviating phosgene-induced ALI, suggesting that enhancing the effect of NEDD4 may be a new approach for treating phosgene-induced ALI.

The NEDD4 ubiquitin E3 ligase: a snapshot view of its functional activity and regulation

Due to its fundamental role in all eukaryotic cells, a deeper understanding of the molecular mechanisms underlying ubiquitination is of central importance. Being responsible for chain specificity and substrate recognition, E3 ligases are the selective elements of the ubiquitination process. In this review, we discuss different cellular pathways regulated by one of the first identified E3 ligase, NEDD4, focusing on its pathophysiological role, its known targets and modulators. In addition, we highlight small molecule inhibitors that act on NEDD4 and discuss new strategies to effectively target this E3 enzyme.

Diverse Roles of F-BoxProtein3 in Regulation of Various Cellular Functions

Accumulated evidence shows that the F-box protein 3 (FBXO3) has multiple biological functions, including regulation of immune pathologies, neuropathic diseases and antiviral response. In this review article, we focus on the role of FBXO3 in inflammatory disorders and human malignancies. We also describe the substrates of FBXO3, which contribute to inflammatory disorders and cancers. We highlight that the high expression of FBXO3 is frequently observed in rheumatoid arthritis, leukemia, pituitary adenoma, and oral squamous cell carcinoma. Moreover, we discuss the regulation of FBXO3 by both carcinogens and cancer preventive agents. Our review provides a comprehensive understanding of the role of FBXO3 in various biological systems and elucidates how FBXO3 regulates substrate ubiquitination and degradation during various physiological and pathological processes. Therefore, FBXO3 can be a novel target in the treatment of human diseases including carcinomas.

N4BP3 Regulates RIG-I-Like Receptor Antiviral Signaling Positively by Targeting Mitochondrial Antiviral Signaling Protein

Mitochondrial antiviral signaling protein (MAVS), an adaptor protein, is activated by RIG-I, which is critical for an effective innate immune response to infection by various RNA viruses. Viral infection causes the RIG-I-like receptor (RLR) to recognize pathogen-derived dsRNA and then becomes activated to promote prion-like aggregation and activation of MAVS. Subsequently, through the recruitment of TRAF proteins, MAVS activates two signaling pathways mediated by TBK1-IRF3 and IKK- NF-κb, respectively, and turns on type I interferon and proinflammatory cytokines. This study discovered that NEDD4 binding protein 3 (N4BP3) is a positive regulator of the RLR signaling pathway by targeting MAVS. Overexpression of N4BP3 promoted virus-induced activation of the interferon-β (IFN-β) promoter and interferon-stimulated response element (ISRE). Further experiments showed that knockdown or knockout N4BP3 impaired RIG-I-like receptor (RLR)-mediated innate immune response, induction of downstream antiviral genes, and cellular antiviral responses. We also detected that N4BP3 could accelerate the interaction between MAVS and TRAF2. Related experiments revealed that N4BP3 could facilitate the ubiquitination modification of MAVS. These findings suggest that N4BP3 is a critical component of the RIG-I-like receptor (RLR)-mediated innate immune response by targeting MAVS, which also provided insight into the mechanisms of innate antiviral responses.

Insights Into the Biological Role of NEDD4L E3 Ubiquitin Ligase in Human Cancers

Neural precursor cell expressed developmentally downregulated 4-like (NEDD4L) is an E3 ubiquitin ligase that has been reported to participate in multiple cellular procedures by regulating of substrate ubiquitination and subsequent protein degradation. A great amount of evidence has demonstrated that NEDD4L mainly functions as a tumor suppressor in most cancer types, while it also acts as an oncogene in a few cancers. In this review, we summarize the potential role of NEDD4L in carcinogenesis and the related underlying molecular mechanism to improve our understanding of its functions in the tumorigenesis of human malignancies. Developing clinical drugs targeting NEDD4L could be a potential therapeutic strategy for cancer therapy in the future.