REGγ drives Lgr5+ stem cells to potentiate radiation induced intestinal regeneration.

Leucine-rich repeat containing G protein-coupled receptor 5 (Lgr5), a marker of intestinal stem cells (ISCs), is considered to play key roles in tissue homoeostasis and regeneration after acute radiation injury. However, the activation of Lgr5 by integrated signaling pathways upon radiation remains poorly understood. Here, we show that irradiation of mice with whole-body depletion or conditional ablation of REGγ in Lgr5+ stem cell impairs proliferation of intestinal crypts, delaying regeneration of intestine epithelial cells. Mechanistically, REGγ enhances transcriptional activation of Lgr5 via the potentiation of both Wnt and Hippo signal pathways. TEAD4 alone or cooperates with TCF4, a transcription factor mediating Wnt signaling, to enhance the expression of Lgr5. Silencing TEAD4 drastically attenuated ß-catenin/TCF4 dependent expression of Lgr5. Together, our study reveals how REGγ controls Lgr5 expression and expansion of Lgr5+ stem cells in the regeneration of intestinal epithelial cells. Thus, REGγ proteasome appears to be a potential therapeutic target for radiation-induced gastrointestinal disorders.

Mapping Novel Biomarkers of Liver Injury by Tissue Proteomic Analysis.

Liver damage is a dynamic process, and evaluation of liver injury degree is the key step in disease diagnosis. However, few common markers among different types of liver injury have been reported. Herein, we generated three liver injury mouse models, including Con A-induced, CCl4-injected, and subjected bile duct ligation mouse models, to simulate different types of liver damage in humans and then performed a label-free mass spectrometry to identify differentially expressed proteins in liver tissues. Interestingly, two proteins, G3BP and ABCC6, were conserved regulated in different liver injury models and are proposed to be biomarkers in liver injury, with G3BP upregulated and ABCC6 downregulated. Overall, our study identified two novel biomarkers of liver injury, and they might be used as potential drug targets of liver damage research studies.

Proteasome-dependent degradation of Smad7 is critical for lung cancer metastasis.

Lung cancer is one of the cancers with highest morbidity and mortality rates and the metastasis of lung cancer is a leading cause of death. Mechanisms of lung cancer metastasis are yet to be fully understood. Herein, we demonstrate that mice deficient for REGγ, a proteasome activator, exhibited a significant reduction in tumor size, numbers, and metastatic rate with prolonged survival in a conditional Kras/p53 mutant lung cancer model. REGγ enhanced the TGFß-Smad signaling pathway by ubiquitin-ATP-independent degradation of Smad7, an inhibitor of the TGFß pathway. Activated TGFß signaling in REGγ-positive lung cancer cells led to diminished expression of E-cadherin, a biomarker of epithelial-mesenchymal transitions (EMT), and elevated mesenchymal markers compared with REGγ-deficient lung cancer cells. REGγ overexpression was found in lung cancer patients with metastasis, correlating with the reduction of E-Cadherin/Smad7 and a poor prognosis. Overall, our study indicates that REGγ promotes lung cancer metastasis by activating TGF-ß signaling via degradation of Smad7. Thus, REGγ may serve as a novel therapeutic target for lung cancers with poor prognosis.

Proteasome activator REGγ promotes inflammation in Leydig cells via IkBε signaling.

The development of testicular inflammation affects the normal male reproductive function. The proteasome activator complex subunit 3 (REGγ) has been suggested to regulate experimental colitis. However, to the best of our knowledge, a potential association between REGγ and testicular inflammation has not been demonstrated. The present study successfully established inflammatory models in C57 mice, primary Leydig cells and the TM3 cell line. It was observed that the absence of REGγ conveyed a significantly protective effect toward testosterone secretion in Leydig cells. REGγ deficiency significantly decreased the expression levels of phosphorylated transcription factor p65 and inflammatory factors in testis tissues, primary Leydig cells and the TM3 cell line. Inflammation also upregulated the expression levels of REGγ. Furthermore, the degradation of the nuclear factor light­chain­enhancer of activated B cells (NF­κB) inhibitor ε (IkBε) signaling pathway regulated REGγ and NF­κB expression. Double knockdown of REGγ and IkBε restored the response in wild­type cells to LPS­induced inflammation. In summary, these results demonstrated that REGγ regulates NF­κB activity by specifically degrading IkBε to regulate inflammation in testicular Leydig cells.

miR-195-5p is critical in REGγ-mediated regulation of wnt/ß-catenin pathway in renal cell carcinoma.

Renal cell carcinoma (RCC) is the most prevalent malignancy of kidney and accounts for approximately 4% of all cancer diagnoses in adults. Previous studies demonstrated microRNA-195-5p (miR-195-5p) as a tumor suppressor which is deregulated in many human cancers. However, the role of miR-195-5p in RCC is largely unknown. In the present study, we demonstrated that miR-195-5p was downregulated and negatively correlated with advanced clinical stage in RCC. Overexpression of miR-195-5p significantly suppressed RCC cells growth in vitro and in vivo, induced apoptosis and enhanced chemosensitivity to sorafenib. Conversely, suppression of miR-195-5p exhibited a reverse effect. REGγ, a proteasome activator, was identified as a novel downstream target of miR-195-5p in RCC. Knockdown of REGγ inhibited proliferation, induced apoptosis, increased sorafenib chemosensitivity and suppressed the wnt/ß-catenin pathway in RCC cells. Moreover, restoration of REGγ markedly abolished the effects of miR-195-5p in RCC, and the wnt/ß-catenin pathway was suppressed by miR-195-5p overexpression while activated by miR-195-5p inhibition in RCC cells. Our findings suggest that miR-195-5p is critical in REGγ-mediated regulation of wnt/ß-catenin pathway in RCC development and may serve as a novel target for RCC treatment.

REGγ accelerates melanoma formation by regulating Wnt/ß-catenin signalling pathway.

It has been reported that the proteasome activator REGγ is associated with multiple oncogenic pathways in human cancers. However, the role of REGγ in the development of melanoma and the underlying mechanisms remain unclear. In this study, we attempted to investigate the effects of REGγ on human melanoma cell proliferation in vitro and in vivo. We demonstrated that knockdown of REGγ inhibited melanoma cell growth and arrested melanoma cell at G1 phase. Furthermore, depletion of REGγ also inhibited the xenograft growth of human melanoma. Mechanistically, REGγ activates Wnt/ß-catenin signal pathway by degrading GSK-3ß in melanoma cell lines and mouse models. Transient knockdown of ß-catenin effectively blocked cell proliferation in REGγ wild-type melanoma cells. In human melanoma samples, REGγ was overexpressed and positively correlated with ß-catenin levels. This study demonstrates that REGγ is a central molecule in the development of melanoma by regulating Wnt/ß-catenin pathway. This suggests that targeting REGγ could be an alternative therapeutic approach for melanoma.