TGF-β signaling pathway mediated by deubiquitinating enzymes

Pollutants to pathogens: The role of heavy metals in modulating TGF-β signaling and lung cancer risk

Lung cancer is a malignant tumor that develops in the lungs due to the uncontrolled growth of aberrant cells. Heavy metals, such as arsenic, cadmium, mercury, and lead, are metallic elements characterized by their high atomic weights and densities. Anthropogenic activities, such as industrial operations and pollution, have the potential to discharge heavy metals into the environment, hence presenting hazards to ecosystems and human well-being. The TGF-β signalling pathways have a crucial function in controlling several cellular processes, with the ability to both prevent and promote tumor growth. TGF-β regulates cellular responses by interacting in both canonical and non-canonical signalling pathways. Research employing both in vitro and in vivo models has shown that heavy metals may trigger TGF-β signalling via complex molecular pathways. Experiments conducted in a controlled laboratory environment show that heavy metals like cadmium and arsenic may directly bind to TGF-β receptors, leading to alterations in their structure that enable the receptor to be phosphorylated. Activation of this route sets in motion subsequent signalling cascades, most notably the canonical Smad pathway. The development of lung cancer has been linked to heavy metals, which are ubiquitous environmental pollutants. To grasp the underlying processes, it is necessary to comprehend their molecular effect on TGF-β pathways. With a particular emphasis on its consequences for lung cancer, this abstract delves into the complex connection between exposure to heavy metals and the stimulation of TGF-β signalling.

USP25 promotes hepatocellular carcinoma progression by interacting with TRIM21 via the Wnt/β-catenin signaling pathway

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in the world. The ubiquitin-specific peptidase 25 (USP25) protein has been reported to participate in the development of several cancers. However, few studies have reported its association with HCC. In this study, we aimed to investigate the function and mechanism of USP25 in the progression of HCC.

METHODS

We analyzed USP25 protein expression in HCC based on The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) database cohorts. Then, we constructed USP25-overexpressing and USP25-knockdown HepG2, MHCC97H, and L-O2 cells. We detected the biological function of USP25 by performing a series of assays, such as Cell Counting Kit-8 (CCK-8), colony formation, transwell, and wound healing assays. Western blotting and quantitative real-time polymerase chain reaction (qRT-PCR) analyses were performed to detect the interaction between USP25 and the Wnt/β-catenin signaling pathway. The relationship between USP25 and tripartite motif-containing 21 (TRIM21) was assessed through mass spectrometry and co-immunoprecipitation (Co-IP) analysis. Finally, we constructed a mouse liver cancer model with the USP25 gene deletion to verify in vivo role of USP25.

RESULTS

USP25 was highly expressed in HCC tissue and HCC cell lines. Importantly, high expression of USP25 in tissues was closely related to a poor prognosis. USP25 knockdown markedly reduced the proliferation, migration, and invasion of HepG2 and MHCC97H cells, whereas USP25 overexpression led to the opposite effects. In addition, we demonstrated that USP25 interacts with TRIM21 to regulate the expression of proteins related to epithelial-mesenchymal transition (EMT; E-cadherin, N-cadherin, and Snail) and the Wnt/β-catenin pathway (β-catenin, Adenomatous polyposis coli, Axin2 and Glycogen synthase kinase 3 beta) and those of their downstream proteins (C-myc and Cyclin D1). Finally, we verified that knocking out USP25 inhibited tumor growth and distant metastasis in vivo .

CONCLUSIONS

In summary, our data showed that USP25 was overexpressed in HCC. USP25 promoted the proliferation, migration, invasion, and EMT of HCC cells by interacting with TRIM21 to activate the β-catenin signaling pathway.

Dual RNA-seq of spleens extracted from channel catfish infected with Aeromonas veronii reveals novel insights into host-pathogen interactions

Interactions between host and pathogen are involving various dynamic changes in transcript expression and critical for understanding host immunity against infections and its associated pathogenesis. Herein, we established a model of channel catfish infected with Aeromonas veronii. The infected fish had prominent body surface bleeding, and the spleen showed hyperemia and swelling. Then, the spleen of channel catfish infected with A. veronii was analyzed by dual RNA sequencing (RNA-seq), and the transcriptome data were compared with uninfected channel catfish spleen or bacteria cultured in vitro. The transcript expression profile of pathogen-host interaction between A. veronii and channel catfish was successfully studied. During infection, the host was enriched for multiple immune-related signaling pathways, such as the Toll-like receptor signaling pathway, Cytokine-cytokine receptor interaction, and T cell receptor signaling pathway; and significantly upregulated for many innate immune-related genes, including IL-8. At the same time, we found that A. veronii mainly harmed the host spleen through hemolysin. Our current findings are of great significance in clarifying the pathogenesis of channel catfish induced by A. veronii and provide gene targets for developing preventive measures.

Transforming growth factor-β in tumour development

Transforming growth factor-β (TGFβ) is a ubiquitous cytokine essential for embryonic development and postnatal tissue homeostasis. TGFβ signalling regulates several biological processes including cell growth, proliferation, apoptosis, immune function, and tissue repair following injury. Aberrant TGFβ signalling has been implicated in tumour progression and metastasis. Tumour cells, in conjunction with their microenvironment, may augment tumourigenesis using TGFβ to induce epithelial-mesenchymal transition, angiogenesis, lymphangiogenesis, immune suppression, and autophagy. Therapies that target TGFβ synthesis, TGFβ-TGFβ receptor complexes or TGFβ receptor kinase activity have proven successful in tissue culture and in animal models, yet, due to limited understanding of TGFβ biology, the outcomes of clinical trials are poor. Here, we review TGFβ signalling pathways, the biology of TGFβ during tumourigenesis, and how protein quality control pathways contribute to the tumour-promoting outcomes of TGFβ signalling.

Ubiquitination and deubiquitination in the regulation of epithelial-mesenchymal transition in cancer: Shifting gears at the molecular level

The process of conversion of non-motile epithelial cells to their motile mesenchymal counterparts is known as epithelial-mesenchymal transition (EMT), which is a fundamental event during embryonic development, tissue repair, and for the maintenance of stemness. However, this crucial process is hijacked in cancer and becomes the means by which cancer cells acquire further malignant properties such as increased invasiveness, acquisition of stem cell-like properties, increased chemoresistance, and immune evasion ability. The switch from epithelial to mesenchymal phenotype is mediated by a wide variety of effector molecules such as transcription factors, epigenetic modifiers, post-transcriptional and post-translational modifiers. Ubiquitination and de-ubiquitination are two post-translational processes that are fundamental to the ubiquitin-proteasome system (UPS) of the cell, and the shift in equilibrium between these two processes during cancer dictates the suppression or activation of different intracellular processes, including EMT. Here, we discuss the complex and dynamic relationship between components of the UPS and EMT in cancer.

OTUB1 augments hypoxia signaling via its non-canonical ubiquitination inhibition of HIF-1α during hypoxia adaptation

As a main regulator of cellular responses to hypoxia, the protein stability of hypoxia-inducible factor (HIF)-1α is strictly controlled by oxygen tension dependent of PHDs-catalyzed protein hydroxylation and pVHL complex-mediated proteasomal degradation. Whether HIF-1α protein stability as well as its activity can be further regulated under hypoxia is not well understood. In this study, we found that OTUB1 augments hypoxia signaling independent of PHDs/VHL and FIH. OTUB1 binds to HIF-1α and depletion of OTUB1 reduces endogenous HIF-1α protein under hypoxia. In addition, OTUB1 inhibits K48-linked polyubiquitination of HIF-1α via its non-canonical inhibition of ubiquitination activity. Furthermore, OTUB1 promotes hypoxia-induced glycolytic reprogramming for cellular metabolic adaptation. These findings define a novel regulation of HIF-1α under hypoxia and demonstrate that OTUB1-mediated HIF-1α stabilization positively regulates HIF-1α transcriptional activity and benefits cellular hypoxia adaptation.

Protein phosphatase 2A regulated by USP7 is polyubiquitinated and polyneddylated

Ubiquitin‑specific protease 7 (USP7) participates in the ubiquitin‑proteasome system (UPS), and is considered an essential regulator of substrate stability in cancers. In a previous study, the substrates that bind to USP7 were separated through two‑dimensional electrophoresis (2‑DE), which resulted in the identification of protein phosphatase 2A (PP2A) through matrix‑assisted laser desorption‑ionization time‑of‑flight mass spectrometry (MALDI‑TOF/MS) analysis. In the present study, GST pull‑down assay was performed to determine whether USP7 and PP2A directly bind to each other. Immunocytochemistry assay confirmed that USP7 co‑localizes with PP2A in the cytoplasm and nucleus of HeLa cells. Moreover, western blotting and immunoprecipitation were performed to determine whether polyubiquitination and polyneddylation of PP2A were formed. The results of the present study demonstrated that USP7 was a deubiquitinating enzyme of PP2A, and regulated the ubiquitination and stability of PP2A through the K48‑linked polyubiquitin chains. Consequently, the knockdown of USP7 reduced the expression of PP2A. The data of the present study revealed the cellular association between USP7 and PP2A, a new substrate of USP7.

Hatching is modulated by microRNA-378a-3p derived from extracellular vesicles secreted by blastocysts

Hatching from the zona pellucida is a prerequisite for embryo implantation and is less likely to occur in vitro for reasons unknown. Extracellular vesicles (EVs) are secreted by the embryo into the culture medium. Yet the role that embryonic EVs and their cargo microRNAs (miRNAs) play in blastocyst hatching has not been elucidated, partially due to the difficulties of isolating them from low amounts of culture medium. Here, we optimized EV-miRNA isolation from medium conditioned by individually cultured bovine embryos and subsequently showed that miR-378a-3p, which was up-regulated in EVs secreted by blastocysts, plays a crucial role in promoting blastocyst hatching. This demonstrates the regulatory effect of miR-378-3p on hatching, which is an established embryo quality parameter linked with implantation.

Extracellular vesicles (EVs) and their cargo microRNAs (miRNAs) are important regulators of embryo development to the blastocyst stage and beyond. Before implantation can take place, hatching of blastocysts from their zona pellucida is required. However, underlying mechanisms by which blastocyst formation and hatching are initiated remain largely unknown. Here, we provide evidence that embryonic EVs containing bta-miR-378a-3p play a crucial role in blastocyst hatching, using a bovine model. A customized procedure was used to isolate EV-miRNAs from culture droplets conditioned by individual bovine embryos that either developed to the blastocyst stage or did not (nonblastocyst). RNA sequencing identified 69 differentially expressed miRNAs between EVs derived from blastocyst conditioned medium (CM) and nonblastocyst CM. Among the miRNAs up-regulated in blastocyst CM, we selected bta-miR-378a-3p for further validation by functionality testing on developing in vitro embryos by means of mimics and inhibitors. Supplementing the embryo culture medium with miR-378a-3p mimic significantly improved blastocyst quality, with higher cell numbers and reduced apoptosis, and improved hatching, while the opposite was found after supplementation with miR-378a-3p inhibitor (P < 0.01). Transcriptomic analysis of embryos treated with miR-378 mimic/inhibitor showed differential expression (P < 0.01) of genes associated with embryo development and implantation, including RAP1GAP, ARFGEF2, SLC7A6, CENPA, SP1, LDLR, PYCR1, MYD88, TPP1, and NCOA3. In conclusion, miR-378a-3p is up-regulated in EVs secreted by embryos that develop to the blastocyst stage, and this EV-derived miR-378a-3p increases blastocyst quality and regulates embryo hatching, which is essential for embryo implantation.

Circ_0022382 ameliorated intervertebral disc degeneration by regulating TGF-β3 expression through sponge adsorption of miR-4726-5p

Circular RNAs (circRNAs) participate in the progression of many diseases, but knowledge on the role of circRNAs in intervertebral disc degeneration (IDD) is limited. In this study, we discovered the characteristics of a new circRNA (circ_0022382) in human endplate chondrocytes. Currently, real-time quantitative polymerase chain reaction (RT-qPCR) showed that the relative expression level of circ_0022382 was significantly lower under intermittent cyclic tension stimulation than in the control group. circ_0022382, miR-4726-5p and Transforming growth factor 3 (TGF-β3) were evaluated by RT-qPCR, Western Blot and immunofluorescence assay. Additionally, the role and mechanism of circ_0022382 in vivo were also consistent in the rat model. Furthermore, Intermittent cyclic mechanical tension can cause degeneration of endplate chondrocytes. The tension-sensitive circRNA_0022382 was decreased, and we found that circRNA_0022382 promoted morphology of endplate chondrocytes by sponge-binding miR-4726-5p down-regulation of target gene the TGF-β3 expression, thereby alleviating IDD. In a rat model of acupuncture, intervertebral disc injection of circ_0022382 relieved the progression of IDD in vivo. In conclusion, the circ_0022382/miR-4726-5p/TGF-β3 axis plays a key role in the anabolism and catabolism of the endplate chondrocyte extracellular matrix (ECM). It is suggested that circ_0022382 may provide a new approach for the prevention and treatment of IDD.

Redox regulation of DUBs and its therapeutic implications in cancer

Reactive oxygen species (ROS) act as a double-edged sword in cancer, where low levels of ROS are beneficial but excessive accumulation leads to cancer progression. Elevated levels of ROS in cancer are counteracted by the antioxidant defense system. An imbalance between ROS generation and the antioxidant system alters gene expression and cellular signaling, leading to cancer progression or death. Post-translational modifications, such as ubiquitination, phosphorylation, and SUMOylation, play a critical role in the maintenance of ROS homeostasis by controlling ROS production and clearance. Recent evidence suggests that deubiquitinating enzymes (DUBs)-mediated ubiquitin removal from substrates is regulated by ROS. ROS-mediated oxidation of the catalytic cysteine (Cys) of DUBs, leading to their reversible inactivation, has emerged as a key mechanism regulating DUB-controlled cellular events. A better understanding of the mechanism by which DUBs are susceptible to ROS and exploring the ways to utilize ROS to pharmacologically modulate DUB-mediated signaling pathways might provide new insight for anticancer therapeutics. This review assesses the recent findings regarding ROS-mediated signaling in cancers, emphasizes DUB regulation by oxidation, highlights the relevant recent findings, and proposes directions of future research based on the ROS-induced modifications of DUB activity.

USP15 Enhances the Proliferation, Migration, and Collagen Deposition of Hypertrophic Scar-Derived Fibroblasts by Deubiquitinating TGF-βR1 In Vitro

Background:

Hypertrophic scar is a fibroproliferative disorder caused by skin injury. The incidence of hypertrophic scar following trauma or burns is 40 to 70 percent or 70 percent, respectively. It has been shown that transforming growth factor (TGF) β1/Smad signaling plays a crucial role in hypertrophic scar, and that USP15 can regulate the activity of TGFβ1/Smad signaling to affect the progression of the disease. However, the underlying mechanism of USP15 in hypertrophic scar remains unclear. The authors hypothesized that USP15 was up-regulated and enhanced the proliferation, migration, invasion, and collagen deposition of hypertrophic scar–derived fibroblasts by deubiquitinating TGF-β receptor I (TβRI) in vitro.

Methods:

Fibroblasts were isolated from human hypertrophic scars in vitro. The knockdown and overexpression of USP15 in hypertrophic scar–derived fibroblasts were performed using lentivirus infection. The effect of USP15 on hypertrophic scar–derived fibroblast proliferation, migration, and invasion, and the expression of TβRI, Smad2, Smad3, α-SMA, COL1, and COL3, were detected by Cell Counting Kit-8, scratch, invasion, quantitative real-time polymerase chain reaction, and Western blot assays. The interaction between USP15 and TβRI was detected by co-immunoprecipitation and ubiquitination assays.

Results:

The authors demonstrated that USP15 knockdown significantly inhibited the proliferation, migration, and invasion of hypertrophic scar–derived fibroblasts in vitro and down-regulated the expression of TβRI, Smad2, Smad3, α-SMA, COL1, and COL3; in addition, USP15 overexpression showed the opposite trends (p < 0.05). Co-immunoprecipitation and ubiquitination assays revealed that USP15 interacted with TβRI and deubiquitinated TβRI.

Conclusion:

USP15 enhances the proliferation, migration, invasion, and collagen deposition of hypertrophic scar–derived fibroblasts by deubiquitinating TβRI in vitro.

USP15 participates in DBP-induced testicular oxidative stress injury through regulating the Keap1/Nrf2 signaling pathway

Di-n-butylphthalate (DBP) has been listed as an environmental priority pollutant in China due to its distinct biotoxicity. Epidemiological studies have shown that exposure to DBP is closely related to a series of congenital and acquired defects in the male reproductive system. The oxidative stress injury caused by DBP plays an important role in these defects. Previous studies have demonstrated that the Keap1/Nrf2 antioxidative pathway plays a protective role in DBP-induced oxidative stress injury. However, the further molecular regulation mechanism of the activation of Nrf2 pathway remains unclear. Here, we demonstrate that DBP caused testicular oxidative stress injury and Nrf2 pathway was activated in response to the injury in vivo and in vitro. Moreover, we validated that reduced level of USP15 attenuates DBP-induced oxidative stress injury through restraining the ubiquitylation and degradation of Nrf2. Notably, USP15 is confirmed as a target of miR-135b-5p and miR-135b-5p mediated inhibition of USP15 is involved in the DBP-induced oxidative stress injury. Collectively, these findings indicated that decreased level of USP15 functions a significant protective effect on the oxidative stress injury of testis caused by DBP via regulating the Keap1/Nrf2 signaling pathway.

Deubiquitinating enzymes as possible drug targets for schistosomiasis

Deubiquitinating enzymes (DUBs) are conserved in Schistosoma mansoni and may be linked to the 26S proteasome. Previous results from our group showed that b-AP15, an inhibitor of the 26S proteasome DUBs UCHL5 and USP14 induced structural and gene expression changes in mature S. mansoni pairs. This work suggests the use of the nonselective DUB inhibitor PR-619 to verify whether these enzymes are potential target proteins for new drug development. Our approach is based on previous studies with DUB inhibitors in mammalian cells that have shown that these enzymes are associated with apoptosis, autophagy and the transforming growth factor beta (TGF-β) signaling pathway. PR-619 inhibited oviposition in parasite pairs in vitro, leading to mitochondrial changes, autophagic body formation, and changes in expression of SmSmad2 and SmUSP9x, which are genes linked to the TGF-β pathway that are responsible for parasite oviposition and SmUCHL5 and SmRpn11 DUB maintenance. Taken together, these results indicate that DUBs may be used as targets for the development of new drugs against schistosomiasis.

USP15: a review of its implication in immune and inflammatory processes and tumor progression

The covalent post-translational modification of proteins by ubiquitination not only influences protein stability and half-life, but also several aspects of protein function including enzymatic activity, sub-cellular localization, and interactions with binding partners. Protein ubiquitination status is determined by the action of large families of ubiquitin ligases and deubiquitinases, whose combined activities regulate many physiological and cellular pathways. The Ubiquitin Specific Protease (USP) family is one of 8 subfamilies of deubiquitinating enzymes composed of more than 50 members. Recent studies have shown that USP15 plays a critical role in regulating many aspects of immune and inflammatory function of leukocytes in response to a broad range of infectious and autoimmune insults and following tissue damage. USP15 regulated pathways reviewed herein include TLR signaling, RIG-I signaling, NF-kB, and IRF3/IRF7-dependent transcription for production of pro-inflammatory cytokines and type I interferons. In addition, USP15 has been found to regulate pathways implicated in tumor onset and progression such as p53, and TGF-β signaling, but also influences the leukocytes-determined immune and inflammatory microenvironment of tumors to affect progression and outcome. Hereby reviewed are recent studies of USP15 in model cell lines in vitro, and in mutant mice in vivo with reference to available human clinical datasets.

BFAR coordinates TGFβ signaling to modulate Th9-mediated cancer immunotherapy

TGFβ is essential for the generation of anti-tumor Th9 cells; on the other hand, it causes resistance against anti-tumor immunity. Despite recent progress, the underlying mechanism reconciling the double-edged effect of TGFβ signaling in Th9-mediated cancer immunotherapy remains elusive. Here, we find that TGFβ-induced down-regulation of bifunctional apoptosis regulator (BFAR) represents the key mechanism preventing the sustained activation of TGFβ signaling and thus impairing Th9 inducibility. Mechanistically, BFAR mediates K63-linked ubiquitination of TGFβR1 at K268, which is critical to activate TGFβ signaling. Thus, BFAR deficiency or K268R knock-in mutation suppresses TGFβR1 ubiquitination and Th9 differentiation, thereby inhibiting Th9-mediated cancer immunotherapy. More interestingly, BFAR-overexpressed Th9 cells exhibit promising therapeutic efficacy to curtail tumor growth and metastasis and promote the sensitivity of anti–PD-1–mediated checkpoint immunotherapy. Thus, our findings establish BFAR as a key TGFβ-regulated gene to fine-tune TGFβ signaling that causes Th9 induction insensitivity, and they highlight the translational potential of BFAR in promoting Th9-mediated cancer immunotherapy.

The Role of Ubiquitin E3 Ligase in Atherosclerosis

Atherosclerosis is a chronic inflammatory vascular disease. Atherosclerotic cardiovascular disease is the main cause of death in both developed and developing countries. Many pathophysiological factors, including abnormal cholesterol metabolism, vascular inflammatory response, endothelial dysfunction and vascular smooth muscle cell proliferation and apoptosis, contribute to the development of atherosclerosis and the molecular mechanisms underlying the development of atherosclerosis are not fully understood. Ubiquitination is a multistep post-translational protein modification that participates in many important cellular processes. Emerging evidence suggests that ubiquitination plays important roles in the pathogenesis of atherosclerosis in many ways, including regulation of vascular inflammation, endothelial cell and vascular smooth muscle cell function, lipid metabolism and atherosclerotic plaque stability. This review summarizes important contributions of various E3 ligases to the development of atherosclerosis. Targeting ubiquitin E3 ligases may provide a novel strategy for the prevention of the progression of atherosclerosis.

E3 Ubiquitin Ligases: Key Regulators of TGFβ Signaling in Cancer Progression

Transforming growth factor β (TGFβ) is a secreted growth and differentiation factor that influences vital cellular processes like proliferation, adhesion, motility, and apoptosis. Regulation of the TGFβ signaling pathway is of key importance to maintain tissue homeostasis. Perturbation of this signaling pathway has been implicated in a plethora of diseases, including cancer. The effect of TGFβ is dependent on cellular context, and TGFβ can perform both anti- and pro-oncogenic roles. TGFβ acts by binding to specific cell surface TGFβ type I and type II transmembrane receptors that are endowed with serine/threonine kinase activity. Upon ligand-induced receptor phosphorylation, SMAD proteins and other intracellular effectors become activated and mediate biological responses. The levels, localization, and function of TGFβ signaling mediators, regulators, and effectors are highly dynamic and regulated by a myriad of post-translational modifications. One such crucial modification is ubiquitination. The ubiquitin modification is also a mechanism by which crosstalk with other signaling pathways is achieved. Crucial effector components of the ubiquitination cascade include the very diverse family of E3 ubiquitin ligases. This review summarizes the diverse roles of E3 ligases that act on TGFβ receptor and intracellular signaling components. E3 ligases regulate TGFβ signaling both positively and negatively by regulating degradation of receptors and various signaling intermediates. We also highlight the function of E3 ligases in connection with TGFβ's dual role during tumorigenesis. We conclude with a perspective on the emerging possibility of defining E3 ligases as drug targets and how they may be used to selectively target TGFβ-induced pro-oncogenic responses.

The Small GTPase RAC1B: A Potent Negative Regulator of-and Useful Tool to Study-TGFβ Signaling

RAC1 and its alternatively spliced isoform, RAC1B, are members of the Rho family of GTPases. Both isoforms are involved in the regulation of actin cytoskeleton remodeling, cell motility, cell proliferation, and epithelial-mesenchymal transition (EMT). Compared to RAC1, RAC1B exhibits a number of distinctive features with respect to tissue distribution, downstream signaling and a role in disease conditions like inflammation and cancer. The subcellular locations and interaction partners of RAC1 and RAC1B vary depending on their activation state, which makes RAC1 and RAC1B ideal candidates to establish cross-talk with cancer-associated signaling pathways-for instance, interactions with signaling by transforming growth factor β (TGFβ), a known tumor promoter. Although RAC1 has been found to promote TGFβ-driven tumor progression, recent observations in pancreatic carcinoma cells surprisingly revealed that RAC1B confers anti-oncogenic properties, i.e., through inhibiting TGFβ-induced EMT. Since then, an unexpected array of mechanisms through which RAC1B cross-talks with TGFβ signaling has been demonstrated. However, rather than being uniformly inhibitory, RAC1B interacts with TGFβ signaling in a way that results in the selective blockade of tumor-promoting pathways, while concomitantly allowing tumor-suppressive pathways to proceed. In this review article, we are going to discuss the specific interactions between RAC1B and TGFβ signaling, which occur at multiple levels and include various components such as ligands, receptors, cytosolic mediators, transcription factors, and extracellular inhibitors of TGFβ ligands.

Deubiquitinase USP13 promotes extracellular matrix expression by stabilizing Smad4 in lung fibroblast cells

Smad4 plays a central role in the regulation of extracellular matrix (ECM) protein expression and cell differentiation; however, the molecular regulation of Smad4 protein stability by a deubiquitinase has not been reported. In the current study, we reveal that a deubiquitinase USP13 stabilizes Smad4, ultimately modulating ECM protein expression in lung fibroblast cells. USP13 was increased in primary adult lung fibroblasts isolated from bleomycin-challenged mice and transforming growth factor (TGF)-β1-treated primary mouse lung fibroblasts. In a bleomycin-induced murine model of lung fibrosis, USP13-deficient mice showed reduced ECM levels such as fibronectin (FN) and collagen compared with wild-type mice. The reductions in both protein levels and mRNA expression of ECM were observed in the isolated lung fibroblasts from USP13-deficient mice, suggesting that downregulation of USP13 reduces ECM levels through inhibiting its transcription. To investigate the molecular mechanisms by which USP13 modulates ECM expression, we focused on the role of USP13 on Smad4 expression. Overexpression of USP13 increased FN and Smad4 protein levels in lung fibroblasts, while downregulation of USP13 reduced Smad4 protein levels, without altering Smad4 mRNA expression, suggesting that USP13 regulates Smad4 protein stability. Knockdown of USP13 decreased Smad4 half-life and promoted Smad4 ubiquitination. Both Smad4 and USP13 were co-localized in the cytoplasm in treated cell, and co-translocated into the nucleus in response to TGF-β1. The results indicate that USP13 promotes ECM expression by stabilizing Smad4 in lung fibroblasts and plays a role in the maintenance of the extracellular matrix in lungs.

USP9X prevents AGEs-induced upregulation of FN and TGF-β1 through activating Nrf2-ARE pathway in rat glomerular mesangial cells

Oxidative stress is a key pathological factor for diabetic renal fibrosis by activating TGF-β/Smad pathway in glomerular mesangial cells (GMCs) to promote the synthesis of extracellular matrix such as fibronectin (FN). Nuclear factor-E2-related factor (Nrf2)- anti-oxidant response element (ARE) anti-oxidative pathway has crucial renoprotective effects, and inhibiting ubiquitin-mediated degradation of Nrf2 delays diabetic renal fibrosis development. Ubiquitin-specific protease 9X (USP9X) has close relationship with oxidative stress and TGF-β/Smad pathway, but whether it regulate diabetic renal fibrosis remains unclarified. Here, we found that advanced glycation-end products (AGEs) dose- and time-dependently reduced the protein expression and deubiquitinase activity of USP9X in GMCs. USP9X overexpression attenuated AGEs-induced upregulation of FN, TGF-β1, and Collagen Ⅳ, three fibrosis-related marker proteins, in a deubiquitinase activity-dependent manner. While USP9X depletion with siRNAs further promoted the expressions of those proteins in AGEs-treated GMCs. Under AGEs treatment conditions, USP9X overexpression markedly increased the total and nuclear levels, ARE-binding ability, and transcriptional activity of Nrf2, upregulated the protein expressions of Nrf2 downstream genes HO-1 and NQO1, and eventually reduced the excessive production of ROS. Overexpression of the deubiquitinase catalytically inactive USP9X-C1556S mutant failed to exert such effects. Silencing Nrf2 abolished the renoprotective effects of USP9X. Further study showed that upon AGEs stimulation, Nrf2 transferred into the nucleus and the interaction between USP9X and Nrf2 was weakened. AGEs also increased Nrf2 ubiquitination level, and overexpression of USP9X, instead of USP9X-C1556S, significantly reduced the ubiquitination level of Nrf2. Taken together, USP9X reduced Nrf2 ubiquitination level and promoted Nrf2-ARE pathway activation to prevent the accumulation of extracellular matrix, eventually alleviated the pathological process of diabetic renal fibrosis.

The Influence of Adalimumab and Cyclosporine A on the Expression Profile of the Genes Related to TGFβ Signaling Pathways in Keratinocyte Cells Treated with Lipopolysaccharide A

BACKGROUND

In the treatment of moderate to severe psoriasis, cyclosporine A (CsA) conventional therapy is used and biological, anti-cytokine treatment using, for example, anti-TNF drug-adalimumab.

AIM

This study aimed at investigating the effect of CsA and adalimumab on the profile of mRNAs and protein expression associated with transforming growth factor β (TGFβ) pathways in human keratinocyte (HaCaT) culture previously exposed to lipopolysaccharide (LPS).

MATERIALS AND METHODS

HaCaT culture was exposed to 1 ng/ml LPS for 8 hours+8 μg/ml adalimumab for 2, 8, and 24 hours or 1 ng/ml LPS for 8 hours+100 ng/ml CsA for 2, 8, and 24 hours and compared to the control culture. Sulphorodamine B cytotoxicity assay was performed. The expression profile of mRNA related to TGFβ paths was indicated by microarray and RTqPCR analyses. The ELISA test was used to analyze changes on the proteome level. Statistical analysis consisted of ANOVA analysis and the post hoc Tukey test (p < 0.05).

RESULTS

The cytotoxicity test showed that LPS, adalimumab, and cyclosporine in the concentration used in this experiment did not have any cytotoxicity effect on HaCaT cells. The largest fold changes (FC) in expression in (∣FC | >4.00) was determined for TGFβ1-3, TGFβRI-III, SKIL, SMURF2, SMAD3, BMP2, BMP6, JAK2, UBE2D1, SKP2, EDN1, and PRKAR2B (p < 0.05). In addition, on the protein level, the direct changes observed at mRNA were the same.

CONCLUSION

Analysis of the microarray expression profile of genes associated with TGFβ signaling pathways has demonstrated the potential of cyclosporin A and adalimumab to induce changes in their transcriptional activity. The anti-TNF drug seems to affect TGFβ cascades to a greater extent than cyclosporin A. The obtained results suggest that the regularity of taking the drug is important for the efficacy of psoriasis therapy.

The evolutionarily conserved deubiquitinase UBH1/UCH-L1 augments DAF7/TGF-β signaling, inhibits dauer larva formation, and enhances lung tumorigenesis

Modification of the transforming growth factor β (TGF-β) signaling components by (de)ubiquitination is emerging as a key regulatory mechanism that controls cell signaling responses in health and disease. Here, we show that the deubiquitinating enzyme UBH-1 in Caenorhabditis elegans and its human homolog, ubiquitin C-terminal hydrolase-L1 (UCH-L1), stimulate DAF-7/TGF-β signaling, suggesting that this mode of regulation of TGF-β signaling is conserved across animal species. The dauer larva-constitutive C. elegans phenotype caused by defective DAF-7/TGF-β signaling was enhanced and suppressed, respectively, by ubh-1 deletion and overexpression in the loss-of-function genetic backgrounds of daf7, daf-1/TGF-βRI, and daf4/R-SMAD, but not of daf-8/R-SMAD. This suggested that UBH-1 may stimulate DAF-7/TGF-β signaling via DAF-8/R-SMAD. Therefore, we investigated the effect of UCH-L1 on TGF-β signaling via its intracellular effectors, i.e. SMAD2 and SMAD3, in mammalian cells. Overexpression of UCH-L1, but not of UCH-L3 (the other human homolog of UBH1) or of the catalytic mutant UCH-L1C90A, enhanced TGF-β/SMAD-induced transcriptional activity, indicating that the deubiquitination activity of UCH-L1 is indispensable for enhancing TGF-β/SMAD signaling. We also found that UCH-L1 interacts, deubiquitinates, and stabilizes SMAD2 and SMAD3. Under hypoxia, UCH-L1 expression increased and TGF-β/SMAD signaling was potentiated in the A549 human lung adenocarcinoma cell line. Notably, UCH-L1-deficient A549 cells were impaired in tumorigenesis, and, unlike WT UCH-L1, a UCH-L1 variant lacking deubiquitinating activity was unable to restore tumorigenesis in these cells. These results indicate that UCH-L1 activity supports DAF-7/TGF-β signaling and suggest that UCH-L1's deubiquitination activity is a potential therapeutic target for managing lung cancer.

Linking Cancer Stem Cell Plasticity to Therapeutic Resistance-Mechanism and Novel Therapeutic Strategies in Esophageal Cancer

Esophageal cancer (EC) is an aggressive form of cancer, including squamous cell carcinoma (ESCC) and adenocarcinoma (EAC) as two predominant histological subtypes. Accumulating evidence supports the existence of cancer stem cells (CSCs) able to initiate and maintain EAC or ESCC. In this review, we aim to collect the current evidence on CSCs in esophageal cancer, including the biomarkers/characterization strategies of CSCs, heterogeneity of CSCs, and the key signaling pathways (Wnt/β-catenin, Notch, Hedgehog, YAP, JAK/STAT3) in modulating CSCs during esophageal cancer progression. Exploring the molecular mechanisms of therapy resistance in EC highlights DNA damage response (DDR), metabolic reprogramming, epithelial mesenchymal transition (EMT), and the role of the crosstalk of CSCs and their niche in the tumor progression. According to these molecular findings, potential therapeutic implications of targeting esophageal CSCs may provide novel strategies for the clinical management of esophageal cancer.

Protein Stability of Pyruvate Kinase Isozyme M2 Is Mediated by HAUSP

The ubiquitin–proteasome system (UPS) is responsible for proteasomal degradation, regulating the half-life of the protein. Deubiquitinating enzymes (DUBs) are components of the UPS and inhibit degradation by removing ubiquitins from protein substrates. Herpesvirus-associated ubiquitin-specific protease (HAUSP) is one such deubiquitinating enzyme and has been closely associated with tumor development. In a previous study, we isolated putative HAUSP binding substrates by two-dimensional electrophoresis (2-DE) and identified them by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF/MS) analysis. The analysis showed that pyruvate kinase isoenzyme M2 (PKM2) was likely to be one of the substrates for HAUSP. Further study revealed that PKM2 binds to HAUSP, confirming the interaction between these proteins, and that PKM2 possesses the putative HAUSP binding motif, E or P/AXXS. Therefore, we generated mutant forms of PKM2 S57A, S97A, and S346A, and found that S57A had less binding affinity. In a previous study, we demonstrated that PKM2 is regulated by the UPS, and that HAUSP- as a DUB-acted on PKM2, thus siRNA for HAUSP increases PKM2 ubiquitination. Our present study newly highlights the direct interaction between HAUSP and PKM2.

Ubiquitin-specific protease-44 inhibits the proliferation and migration of cells via inhibition of JNK pathway in clear cell renal cell carcinoma

Background

Clear cell renal cell carcinoma (ccRCC) is the most common form of adult kidney cancer. Ubiquitin-specific protease (USP)44 has been reported to be involved in various cancers. We investigated the function, role and molecular mechanism of USP44 in ccRCC.

Methods

Data obtained from the Cancer Genome Atlas Data Portal and Gene Expression Omnibus database were analyzed to uncover the clinical relevance of USP44 expression and tumor development. USP44 function in the proliferation and migration of tumor cells was assessed by cellular and molecular analyses using ccRCC lines (786-O cells and Caki-1 cells).

Results

USP44 showed low expression in ccRCC cancer tissues compared with that in normal tissue. USP44 expression was negatively correlated with tumor stage, tumor grade, and patient survival. USP44 overexpression inhibited the proliferation and migration of 786-O cells and Caki-1 cells significantly. USP44 overexpression also prohibited cell proliferation by upregulating expression of P21, downregulating cyclin-D1 expression, and inhibiting cell migration by downregulating expression of matrix metalloproteinase (MMP)2 and MMP9. USP44 knockdown enhanced the proliferation and migration of 786-O cells and Caki-1 cells. USP44 function in inhibiting the proliferation and migration of 786-O cells and Caki-1 cells was associated with phosphorylation of Jun N-terminal kinase (JNK).

Conclusion

USP44 may be a marker in predicting ccRCC progression. Inhibition by USP44 of the proliferation and migration of 786-O cells and Caki-1 cells is dependent upon the JNK pathway.

Smad7 Binds Differently to Individual and Tandem WW3 and WW4 Domains of WWP2 Ubiquitin Ligase Isoforms

WWP2 is an E3 ubiquitin ligase that differentially regulates the contextual tumour suppressor/progressor TGFβ signalling pathway by alternate isoform expression. WWP2 isoforms select signal transducer Smad2/3 or inhibitor Smad7 substrates for degradation through different compositions of protein–protein interaction WW domains. The WW4 domain-containing WWP2-C induces Smad7 turnover in vivo and positively regulates the metastatic epithelial–mesenchymal transition programme. This activity and the overexpression of these isoforms in human cancers make them candidates for therapeutic intervention. Here, we use NMR spectroscopy to solve the solution structure of the WWP2 WW4 domain and observe the binding characteristics of Smad7 substrate peptide. We also reveal that WW4 has an enhanced affinity for a Smad7 peptide phosphorylated at serine 206 adjacent to the PPxY motif. Using the same approach, we show that the WW3 domain also binds Smad7 and has significantly enhanced Smad7 binding affinity when expressed in tandem with the WW4 domain. Furthermore, and relevant to these biophysical findings, we present evidence for a novel WWP2 isoform (WWP2C-ΔHECT) comprising WW3–WW4 tandem domains and a truncated HECT domain that can inhibit TGFβ signalling pathway activity, providing a further layer of complexity and feedback to the WWP2 regulatory apparatus. Collectively, our data reveal a structural platform for Smad substrate selection by WWP2 isoform WW domains that may be significant in the context of WWP2 isoform switching linked to tumorigenesis.

TGF-β signaling in intervertebral disc health and disease

OBJECTIVE

This paper aims to provide a comprehensive review of the changing role of transforming growth factor-β (TGF-β) signaling in intervertebral disc (IVD) health and disease.

METHODS

A comprehensive literature search was performed using PubMed terms 'TGF-β' and 'IVD'.

RESULTS

TGF-β signaling is necessary for the development and growth of IVD, and can play a protective role in the restoration of IVD tissues by stimulating matrix synthesis, inhibiting matrix catabolism, inflammatory response and cell loss. However, excessive activation of TGF-β signaling is detrimental to the IVD, and inhibition of the aberrant TGF-β signaling can delay IVD degeneration.

CONCLUSIONS

Activation of TGF-β signaling has a promising treatment prospect for IVD degeneration, while excessive activation of TGF-β signaling may contribute to the progression of IVD degeneration. Studies aimed at elucidating the changing role of TGF-β signaling in IVD at different pathophysiological stages and its specific molecular mechanisms are needed, and these studies will contribute to safe and effective TGF-β signaling-based treatments for IVD degeneration.

Skeletal muscle atrogenes: From rodent models to human pathologies

Skeletal muscle atrophy is a common side effect of most human diseases. Muscle loss is not only detrimental for the quality of life but it also dramatically impairs physiological processes of the organism and decreases the efficiency of medical treatments. While hypothesized for years, the existence of an atrophying programme common to all pathologies is still incompletely solved despite the discovery of several actors and key regulators of muscle atrophy. More than a decade ago, the discovery of a set of genes, whose expression at the mRNA levels were similarly altered in different catabolic situations, opened the way of a new concept: the presence of atrogenes, i.e. atrophy-related genes. Importantly, the atrogenes are referred as such on the basis of their mRNA content in atrophying muscles, the regulation at the protein level being sometimes more complicate to elucidate. It should be noticed that the atrogenes are markers of atrophy and that their implication as active inducers of atrophy is still an open question for most of them. While the atrogene family has grown over the years, it has mostly been incremented based on data coming from rodent models. Whether the rodent atrogenes are valid for humans still remain to be established. An "atrogene" was originally defined as a gene systematically up- or down-regulated in several catabolic situations. Even if recent works often restrict this notion to the up-regulation of a limited number of proteolytic enzymes, it is important to keep in mind the big picture view. In this review, we provide an update of the validated and potential rodent atrogenes and the metabolic pathways they belong, and based on recent work, their relevance in human physio-pathological situations. We also propose a more precise definition of the atrogenes that integrates rapid recovery when catabolic stimuli are stopped or replaced by anabolic ones.

Cell-Free, Embryo-Specific sncRNA as a Molecular Biological Bridge between Patient Fertility and IVF Efficiency

Small noncoding RNAs (sncRNAs) are key regulators of the majority of human reproduction events. Understanding their function in the context of gametogenesis and embryogenesis will allow insight into the possible causes of in vitro fertilization (IVF) implantation failure. The aim of this study was to analyze the sncRNA expression profile of the spent culture media on day 4 after fertilization and to reveal a relationship with the morphofunctional characteristics of gametes and resultant embryos, in particular, with the embryo development and implantation potential. Thereto, cell-free, embryo-specific sncRNAs were identified by next generation sequencing (NGS) and quantified by reverse transcription coupled with polymerase chain reaction (RT-PCR) in real-time. Significant differences in the expression level of let-7b-5p, let-7i-5p, piR020401, piR16735, piR19675, piR20326, and piR17716 were revealed between embryo groups of various morphological gradings. Statistically significant correlations were found between the expression profiles of piR16735 and piR020401 with the oocyte-cumulus complex number, let-7b-5p and piR020401 with metaphase II oocyte and two pronuclei embryo numbers, let-7i-5p and piR20497 with the spermatozoid count per milliliter of ejaculate, piR19675 with the percentage of linearly motile spermatozoids, let-7b-5p with the embryo development grade, and let-7i-5p with embryo implantation. According to partial least squares discriminant analysis (PLS-DA), the expression levels of let-7i-5p (Variable Importance in Projection score (VIP) = 1.6262), piR020401 (VIP = 1.45281), and piR20497 (VIP = 1.42765) have the strongest influences on the implantation outcome.

The role of ubiquitin-specific peptidases in cancer progression

Protein ubiquitination is an important mechanism for regulating the activity and levels of proteins under physiological conditions. Loss of regulation by protein ubiquitination leads to various diseases, such as cancer. Two types of enzymes, namely, E1/E2/E3 ligases and deubiquitinases, are responsible for controlling protein ubiquitination. The ubiquitin-specific peptidases (USPs) are the main members of the deubiquitinase family. Many studies have addressed the roles of USPs in various diseases. An increasing number of studies have indicated that USPs are critical for cancer progression, and some USPs have been used as targets to develop inhibitors for cancer prevention. Herein we collect and organize most of the recent studies on the roles of USPs in cancer progression and discuss the development of USP inhibitors for cancer therapy in the future.