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

Detailed role of SR-A1 and SR-E3 in tumor biology, progression, and therapy

The first host defense systems are the innate immune response and the inflammatory response. Among innate immune cells, macrophages, are crucial because they preserve tissue homeostasis and eradicate infections by phagocytosis, or the ingestion of particles. Macrophages exhibit phenotypic variability contingent on their stimulation state and tissue environment and may be detected in several tissues. Meanwhile, critical inflammatory functions are played by macrophage scavenger receptors, in particular, SR-A1 (CD204) and SR-E3 (CD206), in a variety of pathophysiologic events. Such receptors, which are mainly found on the surface of multiple types of macrophages, have different effects on processes, including atherosclerosis, innate and adaptive immunity, liver and lung diseases, and, more recently, cancer. Although macrophage scavenger receptors have been demonstrated to be active across the disease spectrum, conflicting experimental findings and insufficient signaling pathways have hindered our comprehension of the molecular processes underlying its array of roles. Herein, as SR-A1 and SR-E3 functions are often binary, either protecting the host or impairing the pathophysiology of cancers has been reviewed. We will look into their function in malignancies, with an emphasis on their recently discovered function in macrophages and the possible therapeutic benefits of SR-A1 and SR-E3 targeting.

Development of an Injectable Biphasic Hyaluronic Acid-Based Hydrogel With Stress Relaxation Properties for Cartilage Regeneration

Biomimetic stress-relaxing hydrogels with reversible crosslinks attract significant attention for stem cell tissue regeneration compared with elastic hydrogels. However, stress-relaxing hyaluronic acid (HA)-based hydrogels fabricated using conventional technologies lack stability, biocompatibility, and mechanical tunability. Here, it is aimed to address these challenges by incorporating calcium or phosphate components into the HA backbone, which allows reversible crosslinking of HA with alginate to form interpenetrating networks, offering stability and mechanical tunability for mimicking cartilage. Diverse stress-relaxing hydrogels (τ1/2; SR50, 60-2000 s) are successfully prepared at ≈3 kPa stiffness with self-healing and shear-thinning abilities, favoring hydrogel injection. In vitro cell experiments with RNA sequencing analysis demonstrate that hydrogels tune chondrogenesis in a biphasic manner (hyaline or calcified) depending on the stress-relaxation properties and phosphate components. In vivo studies confirm the potential for biphasic chondrogenesis. These results indicate that the proposed stress-relaxing HA-based hydrogel with biphasic chondrogenesis (hyaline or calcified) is a promising material for cartilage regeneration.

Epigenetic regulation of TGF-β pathway and its role in radiation response

PURPOSE

Transforming growth factor (TGF-β) plays a dual role in tumor progression as well as a pivotal role in radiation response. TGF-β-related epigenetic regulations, including DNA methylation, histone modifications (including methylation, acetylation, phosphorylation, ubiquitination), chromatin remodeling and non-coding RNA regulation, have been found to affect the occurrence and development of tumors as well as their radiation response in multiple dimensions. Due to the significance of radiotherapy in tumor treatment and the essential roles of TGF-β signaling in radiation response, it is important to better understand the role of epigenetic regulation mechanisms mediated by TGF-β signaling pathways in radiation-induced targeted and non-targeted effects.

CONCLUSIONS

By revealing the epigenetic mechanism related to TGF-β-mediated radiation response, summarizing the existing relevant adjuvant strategies for radiotherapy based on TGF-β signaling, and discovering potential therapeutic targets, we hope to provide a new perspective for improving clinical treatment.

POH1 induces Smad3 deubiquitination and promotes lung cancer metastasis

Smad3 is the key mediator of TGF-β1-triggered signal transduction and the related biological responses, promoting cell invasion and metastasis in various cancers, including lung cancer. However, the deubiquitinase stabilizing Smad3 remains unknown. In this study, we present a paradigm in which POH1 is identified as a novel deubiquitinase of Smad3 that plays a tumor-promoting role in lung adenocarcinoma (LUAD) by regulating Smad3 stability. POH1 markedly increased Smad3 protein levels and prolonged its half-life. POH1 directly interacted and colocalized with Smad3, leading to the removal of poly-deubiquitination of Smad3. Functionally, POH1 facilitated cell proliferation, migration, and invasion by stabilizing Smad3. Importantly, POH1 also promoted liver metastasis of lung cancer cells. The protein levels of both POH1 and Smad3 were raised in the tumor tissues of patients with LUAD, which predicts poor prognosis. Collectively, we demonstrate that POH1 acts as an oncoprotein by enhancing TGF-β1/Smad3 signaling and TGF-β1-mediated metastasis of lung cancer.

Engineered extracellular vesicle-encapsulated CHIP as novel nanotherapeutics for treatment of renal fibrosis

Renal interstitial fibrosis (RIF) is a fundamental pathological feature of chronic kidney disease (CKD). However, toxicity and poor renal enrichment of fibrosis inhibitors limit their further applications. In this study, a platform for CKD therapy is developed using superparamagnetic iron oxide nanoparticles (SPION) decorated mesenchymal stem cells derived extracellular vesicles with carboxyl terminus of Hsc70-interacting protein (CHIP) high expression (SPION-EVs) to achieve higher renal-targeting antifibrotic therapeutic effect. SPION-EVs selectively accumulate at the injury renal sites under an external magnetic field. Moreover, SPION-EVs deliver CHIP to induce Smad2/3 degradation in renal tubular cells which alleviates Smad2/3 activation-mediated fibrosis-like changes and collagen deposition. The extracellular vesicle engineering technology provides a potential nanoplatform for RIF therapy through CHIP-mediated Smad2/3 degradation.

Control of TGFβ signalling by ubiquitination independent function of E3 ubiquitin ligase TRIP12

Transforming growth factor β (TGFβ) pathway is a master regulator of cell proliferation, differentiation, and death. Deregulation of TGFβ signalling is well established in several human diseases including autoimmune disorders and cancer. Thus, understanding molecular pathways governing TGFβ signalling may help better understand the underlying causes of some of those conditions. Here, we show that a HECT domain E3 ubiquitin ligase TRIP12 controls TGFβ signalling in multiple models. Interestingly, TRIP12 control of TGFβ signalling is completely independent of its E3 ubiquitin ligase activity. Instead, TRIP12 recruits SMURF2 to SMAD4, which is most likely responsible for inhibitory monoubiquitination of SMAD4, since SMAD4 monoubiquitination and its interaction with SMURF2 were dramatically downregulated in TRIP12-/- cells. Additionally, genetic inhibition of TRIP12 in human and murine cells leads to robust activation of TGFβ signalling which was rescued by re-introducing wildtype TRIP12 or a catalytically inactive C1959A mutant. Importantly, TRIP12 control of TGFβ signalling is evolutionary conserved. Indeed, genetic inhibition of Drosophila TRIP12 orthologue, ctrip, in gut leads to a reduced number of intestinal stem cells which was compensated by the increase in differentiated enteroendocrine cells. These effects were completely normalised in Drosophila strain where ctrip was co-inhibited together with Drosophila SMAD4 orthologue, Medea. Similarly, in murine 3D intestinal organoids, CRISPR/Cas9 mediated genetic targeting of Trip12 enhances TGFβ mediated proliferation arrest and cell death. Finally, CRISPR/Cas9 mediated genetic targeting of TRIP12 in MDA-MB-231 breast cancer cells enhances the TGFβ induced migratory capacity of these cells which was rescued to the wildtype level by re-introducing wildtype TRIP12. Our work establishes TRIP12 as an evolutionary conserved modulator of TGFβ signalling in health and disease.

YWK-II/APLP2 inhibits TGF-β signaling by interfering with the TGFBR2-Hsp90 interaction

Transforming growth factor-β (TGF-β) regulates multiple cellular biological processes by activating TGF-β type I receptors (TGFBR1) and type II receptors (TGFBR2), and Hsp90 stabilizes these receptors through specific interactions. In many malignancies, one of the most deregulated signaling pathways is the TGF-β signaling pathway, which is often inactivated by mutations or deregulation of TGF-β type II receptors (TGFBR2). However, the molecular mechanisms are not well understood. In this study, we show that YWK-II/APLP2, an immediately early response gene for TGF-β signaling, inhibits TGF-β signaling by promoting the degradation of the TGFBR2 protein. Knockdown of YWK-II/APLP2 increases the TGFBR2 protein level and sensitizes cells to TGF-β stimulation, while YWK-II/APLP2 overexpression destabilizes TGFBR2 and desensitizes cells to TGF-β. Mechanistically, YWK-II/APLP2 is associated with TGFBR2 in a TGF-β activity-dependent manner, binds to Hsp90 to interfere with the interaction between TGFBR2 and Hsp90, and leads to enhanced ubiquitination and degradation of TGFBR2. Taken together, YWK-II/APLP2 is involved in negatively regulating the duration and intensity of TGF-β/Smad signaling and suggests that aberrantly high expression of YWK-II/APLP2 in malignancies may antagonize the growth inhibition mediated by TGF-β signaling and play a role in carcinogenesis.

RNF152 Suppresses Fatty Acid Oxidation and Metastasis of Lung Adenocarcinoma by Inhibiting IRAK1-Mediated AKR1B10 Expression

Lung adenocarcinoma (LUAD) is a common subtype of primary lung cancer. Fatty acid oxidation plays a key role in LUAD development by providing energy for tumor cells. This study aimed to identify the role of ring finger protein 152 (RNF152) in LUAD. RNF152 was down-regulated in LUAD, and low RNF152 expression correlated with a poor prognosis in LUAD patients. RNF152 overexpression inhibited the proliferation and malignant phenotype of LUAD cells, whereas RNF152 knockdown exerted an opposite effect. Tumor cells overexpressing RNF152 showed less fatty acid oxidation compared with control cells, whereas RNF152 knockdown induced fatty acid uptake and oxidation. Further analysis revealed the binding reaction between RNF152 and interleukin-1 receptor-associated kinase 1 (IRAK1). RNF152 reduced the stability of IRAK1 in LUAD cells by promoting its ubiquitination. RNF152-overexpressed tumor cells exhibited a significantly lower level of Aldo-Keto reductase family 1 member 10 (AKR1B10), whereas up-regulation of IRAK1 restored the expression of AKR1B10 in RNF152-overexpressed cells. Furthermore, up-regulation of IRAK1 eliminated the antitumor effect of RNF152 in LUAD cells. Mouse xenograft models confirmed the inhibitory effect of RNF152 on the tumorigenesis and metastasis of LUAD. Taken together, RNF152 played a tumor suppressive role in LUAD by promoting IRAK1 ubiquitination and IRAK1-mediated down-regulation of AKR1B10, thereby reversing the malignant phenotype of LUAD.

LINC00963-FOSB-mediated transcription activation of UBE3C enhances radioresistance of breast cancer cells by inducing ubiquitination-dependent protein degradation of TP73

BACKGROUND

The ubiquitin protein ligase E3C (UBE3C) has been reported to play an oncogenic role in breast cancer (BRCA). This work further investigates the effect of UBE3C on the radioresistance of BRCA cells.

METHODS

Molecules linking to radioresistance in BRCA were identified by analyzing two GEO datasets, GSE31863 and GSE101920. UBE3C overexpression or knockdown was induced in parental or radioresistant BRCA cells, followed by irradiation treatment. The malignant properties of cells in vitro, and the growth and metastatic activity of cells in nude mice, were analyzed. Downstream target proteins, as well as upstream transcriptional regulators of UBE3C, were predicted by bioinformatics tools. Molecular interactions were confirmed by immunoprecipitation and immunofluorescence assays. Furthermore, artificial alterations of TP73 and FOSB were induced in the BRCA cells for functional rescue assays.

RESULTS

According to bioinformatics analyses, UBE3C expression was linked to radioresistance in BRCA. UBE3C knockdown in radioresistant BRCA cells reduced while its overexpression in parental BRCA cells increased the radioresistance of cells in vitro and in vivo. UBE3C, which induced ubiquitination-dependent protein degradation of TP73, was transcriptionally activated by FOSB. The radioresistance of cancer cells was blocked by TP73 overexpression or FOSB knockdown. Additionally, LINC00963 was found to be responsible for the recruitment of FOSB to the UBE3C promoter for transcription activation.

CONCLUSION

This work demonstrates that LINC00963 induces nuclear translocation of FOSB and the consequent transcription activation of UBE3C, which enhances radioresistance of BRCA cells by inducing ubiquitination-dependent protein degradation of TP73.

Bifunctional robots inducing targeted protein degradation

The gaining importance of Targeted Protein Degradation (TPD) and PROTACs (PROteolysis-TArgeting Chimeras) have drawn the scientific community's attention. PROTACs are considered bifunctional robots owing to their avidity for the protein of interest (POI) and E3-ligase, which induce the ubiquitination of POI. These molecules are based on event-driven pharmacology and are applicable in different conditions such as oncology, antiviral, neurodegenerative disease, acne etc., offering tremendous scope to researchers. In this review, primarily, we attempted to compile the recent works available in the literature on PROTACs for various targeted proteins. We summarized the design and development strategies with a focus on molecular information of protein residues and linker design. Rationalization of the ternary complex formation using Artificial Intelligence including machine & deep learning models and traditionally followed computational tools are also included in this study. Moreover, details describing the optimization of PROTACs chemistry and pharmacokinetic properties are added. Advanced PROTAC designs and targeting complex proteins, is summed up to cover the wide spectrum.

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.

To Ub or not to Ub: a regulatory question in TGF-β signaling

The transforming growth factor β (TGF-β) superfamily controls a wide spectrum of biological processes in metazoans, including cell proliferation, apoptosis, differentiation, cell-fate determination, and embryonic development. Deregulation of TGF-β-Smad signaling contributes to developmental anomalies and a variety of disorders and diseases such as tumorigenesis, fibrotic disorders, and immune diseases. In cancer, TGF-β has dual effects through its antiproliferative and prometastatic actions. At the cellular level, TGF-β functions mainly through the canonical Smad-dependent pathway in a cell type-specific and context-dependent manner. Accumulating evidence has demonstrated that ubiquitination plays a vital role in regulating TGF-β-Smad signaling. We summarize current progress on ubiquitination (Ub) and the ubiquitin ligases that regulate TGF-β-Smad signaling.

Enhanced Expression of ARK5 in Hepatic Stellate Cell and Hepatocyte Synergistically Promote Liver Fibrosis

AMPK-related protein kinase 5 (ARK5) is involved in a broad spectrum of physiological and cell events, and aberrant expression of ARK5 has been observed in a wide variety of solid tumors, including liver cancer. However, the role of ARK5 in liver fibrosis remains largely unexplored. We found that ARK5 expression was elevated in mouse fibrotic livers, and showed a positive correlation with the progression of liver fibrosis. ARK5 was highly expressed not only in activated hepatic stellate cells (HSCs), but also in hepatocytes. In HSCs, ARK5 prevents the degradation of transforming growth factor β type I receptor (TβRI) and mothers against decapentaplegic homolog 4 (Smad4) proteins by inhibiting the expression of Smad ubiquitin regulatory factor 2 (Smurf2), thus maintaining the continuous transduction of the transforming growth factor β (TGF-β) signaling pathway, which is essential for cell activation, proliferation and survival. In hepatocytes, ARK5 induces the occurrence of epithelial-mesenchymal transition (EMT), and also promotes the secretion of inflammatory factors. Inflammatory factors, in turn, further enhance the activation of HSCs and deepen the degree of liver fibrosis. Notably, we demonstrated in a mouse model that targeting ARK5 with the selective inhibitor HTH-01-015 attenuates CCl₄-induced liver fibrosis in mice. Taken together, the results indicate that ARK5 is a critical driver of liver fibrosis, and promotes liver fibrosis by synergy between HSCs and hepatocytes.

Regulation of transforming growth factor-β signaling as a therapeutic approach to treating colorectal cancer

According to data from 2020, Slovakia has long been among the top five countries with the highest incidence rate of colorectal cancer (CRC) worldwide, and the rate is continuing to rise every year. In approximately 80% of CRC cases, allelic loss (loss of heterozygosity, LOH) occurs in the long arm of chromosome 18q. The most important genes that can be silenced by 18q LOH or mutations are small mothers against decapentaplegic homolog (SMAD) 2 and SMAD4, which are intracellular mediators of transforming growth factor (TGF)-β superfamily signals. TGF-β plays an important role in the pro-oncogenic processes, including such properties as invasion, epithelial-mesenchymal transition (commonly known as EMT), promotion of angiogenesis, and immunomodulatory effects. Several recent studies have reported that activation of TGF-β signaling is related to drug resistance in CRC. Because the mechanisms of drug resistance are different between patients in different stages of CRC, personalized treatment is more effective. Therefore, knowledge of the activation and inhibition of factors that affect the TGF-β signaling pathway is very important.

Regulation of transforming growth factor-β signaling as a therapeutic approach to treating colorectal cancer

According to data from 2020, Slovakia has long been among the top five countries with the highest incidence rate of colorectal cancer (CRC) worldwide, and the rate is continuing to rise every year. In approximately 80% of CRC cases, allelic loss (loss of heterozygosity, LOH) occurs in the long arm of chromosome 18q. The most important genes that can be silenced by 18q LOH or mutations are small mothers against decapentaplegic homolog (SMAD) 2 and SMAD4, which are intracellular mediators of transforming growth factor (TGF)-β superfamily signals. TGF-β plays an important role in the pro-oncogenic processes, including such properties as invasion, epithelial-mesenchymal transition (commonly known as EMT), promotion of angiogenesis, and immunomodulatory effects. Several recent studies have reported that activation of TGF-β signaling is related to drug resistance in CRC. Because the mechanisms of drug resistance are different between patients in different stages of CRC, personalized treatment is more effective. Therefore, knowledge of the activation and inhibition of factors that affect the TGF-β signaling pathway is very important.

Assessment of the TGFB1 gene expression and methylation status of the promoter region in patients with colorectal cancer

The aim of this study was to evaluate the expression of the TGFB1 gene encoding the TGF-β1 cytokine in 64 patients, and then to compare it with clinico-pathological features. The study also investigated whether the regulation of the gene expression is caused by methylation of the promoter region between - 235 and + 22 nucleotide from the start of transcription. The dependence of the relative level of the TGFB1 gene expression on the clinical advancement according to the TNM classifications was shown. Additionally, the individual grades of the T and M features of the TNM classification differed in the relative transcript levels of the TGFB1 gene. Moreover, the higher relative expression level of the studied gene was associated with a lack of vascular invasion by cancer cells and presence of lymphocytes in the neoplastic tissue. The obtained results may indicate a possible impact of the gene on the process of carcinogenesis in colorectal cancer and reduction of its expression level may be one of the factors contributing to progression of the disease.

A linkage between effectual genes in progression of CRC through canonical and non-canonical TGF-β signaling pathways

Different molecular signaling pathways have been involved in the incidence and progression of CRC. We aimed to examine the correlation between eight candidate genes, including TFGβ, SMAD2, SMAD4, RhoA, EGFR, MAP2K1, MTA1, and LEF1 in the progression of colorectal cancer (CRC) and their association with clinicopathological variables and CRC patients prognosis. Immunohistochemistry and quantitative real-time polymerase chain reaction (qRT-PCR) analysis 2^-ΔΔct, were performed to assess the expression of eight genes in 64 and 122 patients with CRC, respectively and 20 normal samples were added for verification. We showed a positive correlation between SMAD2 and MAP2K1 (r = 0.337, P < 0.001), MAP2K1 and LEF1 (r = 0.187, P = 0.03), SMAD4 and RhoA (r = 0.214, P = 0.01) and as well, a negative correlation between SMAD2 and TGFβ (r =  - 0.197, P = 0.02), and RhoA and LEF1 (r =  - 0.180, P = 0.04) in tumor tissues. A decrease in RhoA mRNA expression was associated with the advanced TNM stage (P = 0.01), while the EGFR and SMAD2 mRNA expression upregulated in advanced stages (P = 0.03, P = 0.03), respectively. Also, an increase in EGFR and SMAD4 protein expression was significantly associated with the advanced TNM stage (P = 0.000) (P = .002), respectively. Perceiving the connections between canonical and non-canonical Transforming growth factor (TGF-β) signaling pathway along with the epidermal growth factor receptor (EGFR) and WNT cascades may trigger the development of novel approaches for CRC prediction.

MiR-30c-5p loss-induced PELI1 accumulation regulates cell proliferation and migration via activating PI3K/AKT pathway in papillary thyroid carcinoma

Background

The aberrant expression of E3 ubiquitin ligase Pellino-1 (PELI1) contributes to several human cancer development and progression. However, its expression patterns and functional importance in papillary thyroid cancer (PTC) remains unknown.

Methods

PELI1 expression profiles in PTC tissues were obtained and analyzed through the starBase v3.0 analysis. Real-time PCR, Immunohistochemical assays (IHC) and Western blot were used to investigate the mRNA and protein levels of PELI1 in PTC. The effects of PELI1 on PTC cell progression were evaluated through CCK-8, colony formation, Transwell, and Wound healing assay in vitro, and a PTC xenograft mouse model in vivo. The downstream target signal of PELI1 in PTC was analyzed by using Kyoto encyclopedia of genes and genomes (KEGG), and bioinformatics tools were used to identify potential miRNAs targeting PELI1. Human umbilical cord mesenchymal stem cells were modified by miR-30c-5p and the miR-30c-5p containing extracellular vesicles were collected (miR-30c-5p-EVs) by ultra-high-speed centrifugation method. Then, the effects of miR-30c-5p-EVs on PELI1 expression and PTC progression were evaluated both in vitro and in vivo.

Results

Both mRNA and protein expression of PELI1 were widely increased in PTC tissues, and overexpression of PELI1 was positively correlated with bigger tumor size and lymph node metastases. PELI1 promoted PTC cell proliferation and migration in vitro. While, PELI1 silencing significantly suppressed PTC growth in vivo accompanied with reduced expression of Ki-67 and matrix metallopeptidase 2 (MMP-2). Mechanistically, PI3K-AKT pathway was identified as the downstream target of PELI1, and mediated the functional influence of PELI1 in PTC cells. Moreover, we found that the expression of miR-30c-5p was inversely correlated with PELI1 in PTC samples and further confirmed that miR-30c-5p was a tumor-suppressive miRNA that directly targeted PELI1 to inhibit PTC cell proliferation and migration. Furthermore, we showed that miR-30c-5p-EVs could effectively downregulate PELI1 expression and suppress the PTC cell growth in vitro and in vivo.

Conclusion

This study not only supported the first evidence that miR-30c-5p loss-induced PELI1 accumulation facilitated cell proliferation and migration by activating the PI3K-AKT pathway in PTC but also provided novel insights into PTC therapy based on miR-carrying-hUCMSC-EVs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03226-1.

MicroRNA-411-3p inhibits bleomycin-induced skin fibrosis by regulating transforming growth factor-β/Smad ubiquitin regulatory factor-2 signalling

Skin fibrosis, which is characterized by fibroblast proliferation and increased extracellular matrix, has no effective treatment. An increasing number of studies have shown that microRNAs (miRNAs/miRs) participate in the mechanism of skin fibrosis, such as in limited cutaneous systemic sclerosis and pathological scarring. The objective of the present study was to determine the role of miR‐411‐3p in bleomycin (BLM)‐induced skin fibrosis and skin fibroblast transformation. Using Western blot analysis and real‐time quantitative polymerase chain reaction assess the expression levels of miR‐411‐3p, collagen (COLI) and transforming growth factor (TGF)‐β/Smad ubiquitin regulatory factor (Smurf)‐2/Smad signalling factors both in vitro and in vivo with or without BLM. To explore the regulatory relationship between miR‐411‐3p and Smurf2, we used the luciferase reporter assay. Furthermore, miR‐411‐3p overexpression was identified in vitro and in vivo via transfection with Lipofectamine 2000 reagent and injection. Finally, we tested the dermal layer of the skin using haematoxylin and eosin and Van Gieson's staining. We found that miR‐411‐3p expression was decreased in bleomycin (BLM)‐induced skin fibrosis and fibroblasts. However, BLM accelerated transforming growth factor (TGF)‐β signalling and collagen production. Overexpression of miR‐411‐3p inhibited the expression of collagen, F‐actin and the TGF‐β/Smad signalling pathway factors in BLM‐induced skin fibrosis and fibroblasts. In addition, miR‐411‐3p inhibited the target Smad ubiquitin regulatory factor (Smurf)‐2. Furthermore, Smurf2 was silenced, which attenuated the expression of collagen via suppression of the TGF‐β/Smad signalling pathway. We demonstrated that miR‐411‐3p exerts antifibrotic effects by inhibiting the TGF‐β/Smad signalling pathway via targeting of Smurf2 in skin fibrosis.

Quantitative ubiquitylome analysis reveals specificity of RNF111/Arkadia E3 ubiquitin ligase for its degradative substrates SKI and SKIL/SnoN in TGF-β signaling pathway

RNF111/Arkadia is an E3 ubiquitin ligase that activates the TGF-β pathway by degrading transcriptional repressors SKIL/SnoN and SKI, and truncations of the RING C-terminal domain of RNF111 that abolish its E3 function and subsequently TGF-β signaling are observed in some cancers. In the present study, we sought to perform a comprehensive analysis of RNF111 endogenous substrates upon TGF-β signaling activation using an integrative proteomic approach. In that aim we carried out label free quantitative proteomics after enrichment of ubiquitylated proteins (ubiquitylome) in parental U2OS cell line compared to U2OS CRISPR engineered clones expressing a truncated form of RNF111 devoid of its C-terminal RING domain. We compared two methods of enrichment for ubiquitylated proteins prior to proteomics analysis by mass spectrometry, the diGly remnant peptide immunoprecipitation with a K-ε-GG antibody (diGly) and a novel approach using protein immunoprecipitation with a ubiquitin pan nanobody (pan UB) that recognizes all ubiquitin chains and monoubiquitylation. While we detected SKIL ubiquitylation among 108 potential RNF111 substrates with the diGly method, we found that the pan UB method also constitutes a powerful approach since it enabled detection of 52 potential RNF111 substrates including SKI, SKIL and RNF111. Integrative comparison of the RNF111-dependent proteome and ubiquitylomes enabled identification of SKI and SKIL as the only targets ubiquitylated and degraded by RNF111 E3 ligase function in presence of TGF-β. Our results indicate that lysine 343 localized in the SAND domain of SKIL constitutes a target for RNF111 ubiquitylation and demonstrate that RNF111 E3 ubiquitin ligase function specifically targets SKI and SKIL ubiquitylation and degradation upon TGF-β pathway activation.

Transforming Growth Factor-β: An Agent of Change in the Tumor Microenvironment

Transforming Growth Factor-β (TGF-β) is a key regulator of embryonic development, adult tissue homeostasis, and lesion repair. In tumors, TGF-β is a potent inhibitor of early stage tumorigenesis and promotes late stage tumor progression and metastasis. Here, we review the roles of TGF-β as well as components of its signaling pathways in tumorigenesis. We will discuss how a core property of TGF-β, namely its ability to change cell differentiation, leads to the transition of epithelial cells, endothelial cells and fibroblasts to a myofibroblastoid phenotype, changes differentiation and polarization of immune cells, and induces metabolic reprogramming of cells, all of which contribute to the progression of epithelial tumors.