USP36-Mediated Deubiquitination of DOCK4 Contributes to the Diabetic Renal Tubular Epithelial Cell Injury via Wnt/β-Catenin Signaling Pathway

A potential therapeutic molecule target: lncRNA AK023507 inhibits the metastasis of breast cancer by regulating the WNT/DOCK4/β-catenin axis

PURPOSE

Breast cancer (BC) has become the most common malignant tumor in women worldwide. This study was carried out to find and validate a novel molecular therapeutic target for BC.

METHODS

Long non-coding RNA (lncRNA) AK023507 was selected as the study objects through microarray analysis. The function of lncRNA AK023507 was verified by various cell function experiments in vitro, subcutaneous tumorigenesis experiments, and lung metastasis model experiments in vivo. The RNA pull-down experiment and Western blot experiment were used to confirm the mechanism regulation pathway and the recovery experiment was used to verify it. TCGA datasets were used for clinical and immune function prediction analysis.

RESULTS

In vitro cell function tests and in vivo experiments suggested that overexpression of lncRNA AK023507 inhibited the proliferation and metastasis of BC cells. The RNA pull-down experiment and Western blot analysis validated that lncRNA AK023507 interacted with the dedicator of cytokinesis 4 (DOCK4) protein. Analysis of public databases predicted that DOCK4 is a potential prognostic risk factor associated with epithelial-mesenchymal transition (EMT) and central memory T cell (TCM) cellular immune infiltration.

CONCLUSIONS

LncRNA AK023507 inhibits the proliferation and metastasis of BC by regulating the DOCK4/β-catenin axis. This discovery will provide new potential therapeutic targets for BC.

Silencing DOCK2 Attenuates Cardiac Fibrosis Following Myocardial Infarction in Mice Via Targeting PI3K/Akt and Wnt/β-Catenin Pathways

Cardiac fibrosis following myocardial infarction (MI) seriously affects the prognosis and survival rate of patients. This study aimed to determine the effect and regulation mechanism of the dedicator of cytokinesis 2 (DOCK2) during this process. Experiments were carried out in mice in vivo, and in Ang II treated cardiac fibroblasts (CFs) in vitro. DOCK2 was increased in mouse myocardial tissues after MI and Ang II-treated CFs. In MI mice, DOCK2 silencing improved cardiac function, and ameliorated cardiac fibrosis. DOCK2 knockdown suppressed the activation of CFs and decreased the expression of α-SMA, collagen I, and collagen III. Suppression of DOCK2 mitigated Ang II induced migration of CFs. DOCK2 inhibition reduced the activity of the PI3K/Akt and Wnt/β-catenin pathways, while this change could be reversed by the pathway activators, SC79 and SKL2001. In summary, DOCK2 suppression improves cardiac dysfunction and attenuates cardiac fibrosis after MI via attenuating PI3K/Akt and Wnt/β-catenin pathways.

Oridonin ameliorates renal fibrosis in diabetic nephropathy by inhibiting the Wnt/β-catenin signaling pathway

Diabetic nephropathy (DN) is one of the most serious and frequent complications among diabetes patients and presently constitutes vast the cases of end-stage renal disease worldwide. Tubulointerstitial fibrosis is a crucial factor related to the occurrence and progression of DN. Oridonin (Ori) is a diterpenoid derived from rubescens that has diverse pharmacological properties. Our previous study showed that Ori can protect against DN by decreasing the inflammatory response. However, whether Ori can alleviate renal fibrosis in DN remains unknown. Here, we investigated the mechanism through which Ori affects the Wnt/β-catenin signaling pathway in diabetic rats and human proximal tubular epithelial cells (HK-2) exposed to high glucose (HG) levels. Our results revealed that Ori treatment markedly decreased urinary protein excretion levels, improved renal function and alleviated renal fibrosis in diabetic rats. In vitro, HG treatment increased the migration of HK-2 cells while reducing their viability and proliferation rate, and treatment with Ori reversed these changes. Additionally, the knockdown of β-catenin arrested cell migration and reduced the expression levels of Wnt/β-catenin signaling-related molecules (Wnt4, p-GSK3β and β-catenin) and fibrosis-related molecules (α-smooth muscle actin, collagen I and fibronectin), and Ori treatment exerted an effect similar to that observed after the knockdown of β-catenin. Furthermore, the combination of Ori treatment and β-catenin downregulation exerted more pronounced biological effects than treatment alone. These findings may provide the first line of evidence showing that Ori alleviates fibrosis in DN by inhibiting the Wnt/β-catenin signaling pathway and thereby reveal a novel therapeutic avenue for treating tubulointerstitial fibrosis.

SUMOylation regulation of ribosome biogenesis: Emerging roles for USP36

Ribosome biogenesis is essential for cell growth, proliferation, and animal development. Its deregulation leads to various human disorders such as ribosomopathies and cancer. Thus, tight regulation of ribosome biogenesis is crucial for normal cell homeostasis. Emerging evidence suggests that posttranslational modifications such as ubiquitination and SUMOylation play a crucial role in regulating ribosome biogenesis. Our recent studies reveal that USP36, a nucleolar deubiquitinating enzyme (DUB), acts also as a SUMO ligase to regulate nucleolar protein group SUMOylation, thereby being essential for ribosome biogenesis. Here, we provide an overview of the current understanding of the SUMOylation regulation of ribosome biogenesis and discuss the role of USP36 in nucleolar SUMOylation.

Epithelial-mesenchymal plasticity in kidney fibrosis

Epithelial-mesenchymal transition (EMT) is an important biological process contributing to kidney fibrosis and chronic kidney disease. This process is characterized by decreased epithelial phenotypes/markers and increased mesenchymal phenotypes/markers. Tubular epithelial cells (TECs) are commonly susceptible to EMT by various stimuli, for example, transforming growth factor-β (TGF-β), cellular communication network factor 2, angiotensin-II, fibroblast growth factor-2, oncostatin M, matrix metalloproteinase-2, tissue plasminogen activator (t-PA), plasmin, interleukin-1β, and reactive oxygen species. Similarly, glomerular podocytes can undergo EMT via these stimuli and by high glucose condition in diabetic kidney disease. EMT of TECs and podocytes leads to tubulointerstitial fibrosis and glomerulosclerosis, respectively. Signaling pathways involved in EMT-mediated kidney fibrosis are diverse and complex. TGF-β1/Smad and Wnt/β-catenin pathways are the major venues triggering EMT in TECs and podocytes. These two pathways thus serve as the major therapeutic targets against EMT-mediated kidney fibrosis. To date, a number of EMT inhibitors have been identified and characterized. As expected, the majority of these EMT inhibitors affect TGF-β1/Smad and Wnt/β-catenin pathways. In addition to kidney fibrosis, these EMT-targeted antifibrotic inhibitors are expected to be effective for treatment against fibrosis in other organs/tissues.

Roles of ubiquitin-specific proteases in inflammatory diseases

Ubiquitin-specific proteases (USPs), as one of the deubiquitinating enzymes (DUBs) families, regulate the fate of proteins and signaling pathway transduction by removing ubiquitin chains from the target proteins. USPs are essential for the modulation of a variety of physiological processes, such as DNA repair, cell metabolism and differentiation, epigenetic modulations as well as protein stability. Recently, extensive research has demonstrated that USPs exert a significant impact on innate and adaptive immune reactions, metabolic syndromes, inflammatory disorders, and infection via post-translational modification processes. This review summarizes the important roles of the USPs in the onset and progression of inflammatory diseases, including periodontitis, pneumonia, atherosclerosis, inflammatory bowel disease, sepsis, hepatitis, diabetes, and obesity. Moreover, we highlight a comprehensive overview of the pathogenesis of USPs in these inflammatory diseases as well as post-translational modifications in the inflammatory responses and pave the way for future prospect of targeted therapies in these inflammatory diseases.

CUL3 induces mitochondrial dysfunction via MRPL12 ubiquitination in renal tubular epithelial cells

Diabetic kidney disease (DKD) is the leading cause of chronic kidney disease worldwide and the strongest predictor of mortality in patients with diabetes. Despite its significance, the pathological mechanism underlying the onset and progression of DKD remains incompletely understood. In this study, we have shown that mitochondrial ribosomal protein L12 (MRPL12) plays a significant role in DKD by modulating mitochondrial function. We demonstrated that MRPL12 was mainly ubiquitinated at K150 in renal tubular epithelial cells. We have found that Cullin3 (CUL3), an E3 ubiquitin ligase, directly interacts with MRPL12 and induces the K63-linked ubiquitination of MRPL12, resulting in mitochondrial biosynthesis dysfunction. Moreover, under high-glucose (HG) conditions in renal tubular epithelial cells, we observed up-regulation of CUL3 expression, significant increase in CUL3-mediated ubiquitination of MRPL12 and dysregulation of mitochondrial biosynthesis. Notably, CUL3 knockdown stabilised the MRPL12 protein and protected mitochondrial biosynthesis under HG conditions. Our findings provide novel insight into how CUL3 affects mitochondrial biosynthesis in renal tubular epithelial cells through MRPL12 ubiquitination and suggest a potential therapeutic strategy for DKD in the future.

Emerging Therapeutic Strategies for Attenuating Tubular EMT and Kidney Fibrosis by Targeting Wnt/β-Catenin Signaling

Epithelial-mesenchymal transition (EMT) is defined as a process in which differentiated epithelial cells undergo phenotypic transformation into myofibroblasts capable of producing extracellular matrix, and is generally regarded as an integral part of fibrogenesis after tissue injury. Although there is evidence that the complete EMT of tubular epithelial cells (TECs) is not a major contributor to interstitial myofibroblasts in kidney fibrosis, the partial EMT, a status that damaged TECs remain inside tubules, and co-express both epithelial and mesenchymal markers, has been demonstrated to be a crucial stage for intensifying fibrogenesis in the interstitium. The process of tubular EMT is governed by multiple intracellular pathways, among which Wnt/β-catenin signaling is considered to be essential mainly because it controls the transcriptome associated with EMT, making it a potential therapeutic target against kidney fibrosis. A growing body of data suggest that reducing the hyperactivity of Wnt/β-catenin by natural compounds, specific inhibitors, or manipulation of genes expression attenuates tubular EMT, and interstitial fibrogenesis in the TECs cultured under profibrotic environments and in animal models of kidney fibrosis. These emerging therapeutic strategies in basic researches may provide beneficial ideas for clinical prevention and treatment of chronic kidney disease.