The ubiquitin ligase Smurf2 suppresses TGFβ-induced epithelial-mesenchymal transition in a sumoylation-regulated manner

Down-regulation of MYO1A inhibits trophoblast cell proliferation and migration through SMURF2/Hedgehog signaling pathway and leads to fetal growth restriction

INTRODUCTION

Fetal growth restriction (FGR) is most commonly related to insufficient placental perfusion caused by insufficient trophoblast proliferation and migration. Myosin Ia, encoded by the gene MYO1A, plays an important role in cytoskeleton recombination and cell movement. In this study, we found that downregulation of MYO1A inhibits Hedgehog (Hh) signaling by interacting with SMURF2 in choriocarcinoma cells, leading to FGR.

METHODS

A total of 59 placenta samples (26 FGR placentas and 33 normal placentas) were collected. The expression of MYO1A in placental tissues of the two groups was detected by qRT-PCR and Western blotting. The proliferation ability of choriocarcinoma cell lines HTR-8/SVneo and JEG3 was tested by CCK8 and colony formation experiments, and the migration ability was tested by transwell and wound healing experiments. Co-immunoprecipitation assay is used to verify the interaction between myosin Ia and SMURF2.

RESULT

We found that MYO1A expression was significantly lower in the placentas of pregnant women with FGR than in normal pregnant women. Moreover, the knockdown of MYO1A has been observed to inhibit choriocarcinoma cells proliferation and migration. Downregulation of MYO1A inhibits Hh signaling by reducing SMURF2 expression.

DISCUSSION

Our findings suggest that FGR is associated with a down-regulation of MYO1A, which may affect the Hh pathway through its interaction with SMURF2. This provides clues for a deeper understanding of the specific mechanisms underlying FGR.

Targeting the SMURF2-HIF1α axis: a new frontier in cancer therapy

The SMAD-specific E3 ubiquitin protein ligase 2 (SMURF2) has emerged as a critical regulator in cancer biology, modulating the stability of Hypoxia-Inducible Factor 1-alpha (HIF1α) and influencing a network of hypoxia-driven pathways within the tumor microenvironment (TME). SMURF2 targets HIF1α for ubiquitination and subsequent proteasomal degradation, disrupting hypoxic responses that promote cancer cell survival, metabolic reprogramming, angiogenesis, and resistance to therapy. Beyond its role in HIF1α regulation, SMURF2 exerts extensive control over cellular processes central to tumor progression, including chromatin remodeling, DNA damage repair, ferroptosis, and cellular stress responses. Notably, SMURF2's ability to promote ferroptotic cell death through GSTP1 degradation offers an alternative pathway to overcome apoptosis resistance, expanding therapeutic options for refractory cancers. This review delves into the multifaceted interactions between SMURF2 and HIF1α, emphasizing how their interplay impacts metabolic adaptations like the Warburg effect, immune evasion, and therapeutic resistance. We discuss SMURF2's dual functionality as both a tumor suppressor and, in certain contexts, an oncogenic factor, underscoring its potential as a highly versatile therapeutic target. Furthermore, modulating the SMURF2-HIF1α axis presents an innovative approach to destabilize hypoxia-dependent pathways, sensitizing tumors to chemotherapy, radiotherapy, and immune-based treatments. However, the complexity of SMURF2's interactions necessitate a thorough assessment of potential off-target effects and challenges in specificity, which must be addressed to optimize its clinical application. This review concludes by proposing future directions for research into the SMURF2-HIF1α pathway, aiming to refine targeted strategies that exploit this axis and address the adaptive mechanisms of aggressive tumors, ultimately advancing the landscape of precision oncology.

An mRNA-encoded dominant-negative inhibitor of transcription factor RUNX1 suppresses vitreoretinal disease in experimental models

Messenger RNA (mRNA)-based therapies are a promising approach to medical treatment. Except for infectious diseases, no other disease has mRNA-based therapies available. The eye is an ideal model for mRNA therapeutic development because it requires limited dosing. Proliferative vitreoretinopathy (PVR) is a blinding condition caused by retinal detachment that now lacks available medical treatment, with surgery as the only treatment option. We previously implicated runt-related transcription factor-1 (RUNX1) as a driver of epithelial-to-mesenchymal transition (EMT) in PVR and as a critical mediator of aberrant ocular angiogenesis when up-regulated. On the basis of these findings, an mRNA was designed to express a dominant-negative inhibitor of RUNX1 (RUNX1-Trap). We show that RUNX1-Trap delivered in polymer-lipidoid complexes or lipid nanoparticles sequestered RUNX1 in the cytosol and strongly reduced proliferation in primary cell cultures established from fibrotic membranes derived from patients with PVR. We assessed the preclinical efficacy of intraocular delivery of mRNA-encoded RUNX1-Trap in a rabbit model of PVR and in a laser-induced mouse model of aberrant angiogenesis often used to study wet age-related macular degeneration. mRNA-encoded RUNX1-Trap suppressed ocular pathology, measured as pathological scores in the rabbit PVR model and leakage and lesion size in the laser-induced choroidal neovascularization mouse model. mRNA-encoded RUNX1-Trap also strongly reduced proliferation in a human ex vivo explant model of PVR. These data demonstrate the therapeutic potential of mRNA-encoded therapeutic molecules with dominant-negative properties, highlighting the potential of mRNA-based therapies beyond standard gene supplementation approaches.

AMPK induces PIAS3 mediated SUMOylation of E3 ubiquitin ligase Smurf1 impairing osteogenic differentiation and traumatic heterotopic ossification

AMP-activated protein kinase (AMPK) is a typical sensor of intracellular energy metabolism. Our previous study revealed the role of activated AMPK in the suppression of osteogenic differentiation and traumatic heterotopic ossification, but the underlying mechanism remains poorly understood. The E3 ubiquitin ligase Smurf1 is a crucial regulator of osteogenic differentiation and bone formation. We report here that Smurf1 is primarily SUMOylated at a C-terminal lysine residue (K324), which enhances its activity, facilitating ALK2 proteolysis and subsequent bone morphogenetic protein (BMP) signaling pathway inhibition. Furthermore, SUMOylation of the SUMO E3 ligase PIAS3 and Smurf1 SUMOylation was suppressed during the osteogenic differentiation and traumatic heterotopic ossification. More importantly, we found that AMPK activation enhances the SUMOylation of Smurf1, which is mediated by PIAS3 and increases the association between PIAS3 and AMPK. Overall, our study revealed that Smurf1 can be SUMOylated by PIAS3, Furthermore, Smurf1 SUMOylation mediates osteogenic differentiation and traumatic heterotopic ossification through suppression of the BMP signaling pathway. This study revealed that promotion of Smurf1 SUMOylation by AMPK activation may be implicated in traumatic heterotopic ossification treatment.

Association of mitochondrial phosphoenolpyruvate carboxykinase with prognosis and immune regulation in hepatocellular carcinoma

Mitochondrial phosphoenolpyruvate carboxykinase (PCK2), a mitochondrial isoenzyme, supports the growth of cancer cells under glucose deficiency conditions in vitro. This study investigated the role and potential mechanism of PCK2 in the occurrence and development of Hepatocellular carcinoma (HCC). The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO), and other databases distinguish the expression of PCK2 and verified by qRT-PCR and Western blotting. Kaplan-Meier was conducted to assess PCK2 survival in HCC. The potential biological function of PCK2 was verified by enrichment analysis and gene set enrichment analysis (GSEA). The correlation between PCK2 expression and immune invasion and checkpoint was found by utilizing Tumor Immune Estimation Resource (TIMER). Lastly, the effects of PCK2 on the proliferation and metastasis of hepatocellular carcinoma cells were evaluated by cell tests, and the expressions of Epithelial mesenchymal transformation (EMT) and apoptosis related proteins were detected. PCK2 is down-regulated in HCC, indicating a poor prognosis. PCK2 gene mutation accounted for 1.3% of HCC. Functional enrichment analysis indicated the potential of PCK2 as a metabolism-related therapeutic target. Subsequently, we identified several signaling pathways related to the biological function of PCK2. The involvement of PCK2 in immune regulation was verified and key immune checkpoints were predicted. Ultimately, after PCK2 knockdown, cell proliferation and migration were significantly increased, and N-cadherin and vimentin expression were increased. PCK2 has been implicated in immune regulation, proliferation, and metastasis of hepatocellular carcinoma, and is emerging as a novel predictive biomarker and metabolic-related clinical target.

The regulatory roles of Smad2/3 protein and SMURF2 gene expression in granulosa cells of germinal vesicle and metaphase II oocytes in polycystic ovarian syndrome: A case-control study

Background

The impaired functions of granulosa cells (GCs) in the delayed development and immaturity of oocytes have been reported in polycystic ovary syndrome (PCOs). Even with ovarian stimulation, a large number of oocytes in these patients are still in the stage germinal vesicle (GV).

Objective

The levels of Smad2/3, phosphorylated Smad2/3 (P-Smad2/3), the expression of SARA, Smad4, and SMURF2 genes in the GCs surrounding metaphase II (MII) or GV oocytes in PCOs women were investigated.

Materials and Methods

GCs of MII and GV oocytes were isolated from 38 women with PCOs and the expression levels of SARA, Smad4, and SMURF2 in surrounding GCs of MII and GV oocytes were determined using reverse-transcription polymerase chain reaction. Also, Smad2/3 and P-Smad2/3 proteins were determined using western blotting.

Results

The expression level of SMURF2 was significantly higher in GCs surrounding GV oocytes compared with that of GCs encompassing MII oocytes (p < 0.001). At the same time, no significant differences were observed in SARA and Smad4 expression levels in GCs surrounding GV and MII oocytes. A lower level of P-Smad2/3 was also found in GCs GV oocytes compared with GCs of MII oocytes (p < 0.001).

Conclusion

It seems that P-Smad2/3 plays a role in oocyte development, and the downregulation of this protein is associated with a defect in the maturation of GV oocytes. On the other hand, the upregulation of the SMURF2 gene also affects the growth process of GCs and the maturation of GV oocytes.

Cbfβ regulates Wnt/β-catenin, Hippo/Yap, and Tgfβ signaling pathways in articular cartilage homeostasis and protects from ACLT surgery-induced osteoarthritis

As the most common degenerative joint disease, osteoarthritis (OA) contributes significantly to pain and disability during aging. Several genes of interest involved in articular cartilage damage in OA have been identified. However, the direct causes of OA are poorly understood. Evaluating the public human RNA-seq dataset showed that CBFB (subunit of a heterodimeric Cbfβ/Runx1, Runx2, or Runx3 complex) expression is decreased in the cartilage of patients with OA. Here, we found that the chondrocyte-specific deletion of Cbfb in tamoxifen-induced Cbfbf/f;Col2a1-CreERT mice caused a spontaneous OA phenotype, worn articular cartilage, increased inflammation, and osteophytes. RNA-sequencing analysis showed that Cbfβ deficiency in articular cartilage resulted in reduced cartilage regeneration, increased canonical Wnt signaling and inflammatory response, and decreased Hippo/Yap signaling and Tgfβ signaling. Immunostaining and western blot validated these RNA-seq analysis results. ACLT surgery-induced OA decreased Cbfβ and Yap expression and increased active β-catenin expression in articular cartilage, while local AAV-mediated Cbfb overexpression promoted Yap expression and diminished active β-catenin expression in OA lesions. Remarkably, AAV-mediated Cbfb overexpression in knee joints of mice with OA showed the significant protective effect of Cbfβ on articular cartilage in the ACLT OA mouse model. Overall, this study, using loss-of-function and gain-of-function approaches, uncovered that low expression of Cbfβ may be the cause of OA. Moreover, Local admission of Cbfb may rescue and protect OA through decreasing Wnt/β-catenin signaling, and increasing Hippo/Yap signaling and Tgfβ/Smad2/3 signaling in OA articular cartilage, indicating that local Cbfb overexpression could be an effective strategy for treatment of OA.

Distinctive tumorigenic significance and innovative oncology targets of SUMOylation

Protein SUMOylation, a post-translational modification, intricately regulates diverse biological processes including gene expression, cell cycle progression, signaling pathway transduction, DNA damage response, and RNA metabolism. This modification contributes to the acquisition of tumorigenicity and the maintenance of cancer hallmarks. In malignancies, protein SUMOylation is triggered by various cellular stresses, promoting tumor initiation and progression. This augmentation is orchestrated through its specific regulatory mechanisms and characteristic biological functions. This review focuses on elucidating the fundamental regulatory mechanisms and pathological functions of the SUMO pathway in tumor pathogenesis and malignant evolution, with particular emphasis on the tumorigenic potential of SUMOylation. Furthermore, we underscore the potential therapeutic benefits of targeting the SUMO pathway, paving the way for innovative anti-tumor strategies by perturbing this dynamic and reversible modifying process.

YTHDF2 governs muscle size through a targeted modulation of proteostasis

The regulation of proteostasis is fundamental for maintenance of muscle mass and function. Activation of the TGF-β pathway drives wasting and premature aging by favoring the proteasomal degradation of structural muscle proteins. Yet, how this critical post-translational mechanism is kept in check to preserve muscle health remains unclear. Here, we reveal the molecular link between the post-transcriptional regulation of m6A-modified mRNA and the modulation of SMAD-dependent TGF-β signaling. We show that the m6A-binding protein YTHDF2 is essential to determining postnatal muscle size. Indeed, muscle-specific genetic deletion of YTHDF2 impairs skeletal muscle growth and abrogates the response to hypertrophic stimuli. We report that YTHDF2 controls the mRNA stability of the ubiquitin ligase ASB2 with consequences on anti-growth gene program activation through SMAD3. Our study identifies a post-transcriptional to post-translational mechanism for the coordination of gene expression in muscle.

Deficiency of Cbfβ in articular cartilage leads to osteoarthritis-like phenotype through Hippo/Yap, TGFβ, and Wnt/β-catenin signaling pathways

Osteoarthritis (OA) is the most prevalent degenerative joint disorder, causing physical impairments among the elderly. Core binding factor subunit β (Cbfβ) has a critical role in bone homeostasis and cartilage development. However, the function and mechanism of Cbfβ in articular cartilage and OA remains unclear. We found that Cbfβf/fAggrecan-CreERT mice with Cbfβ-deficiency in articular cartilage developed a spontaneous osteoarthritis-like phenotype with articular cartilage degradation. Immunofluorescence staining showed that Cbfβf/fAggrecan-CreERT mice exhibited a significant increase in the expression of articular cartilage degradation markers and inflammatory markers in the knee joints. RNA-sequencing analysis demonstrated that Cbfβ orchestrated Hippo/Yap, TGFβ/Smad, and Wnt/β-catenin signaling pathways in articular cartilage, and Cbfβ deficiency resulted in the abnormal expression of downstream genes involved in maintaining articular cartilage homeostasis. Immunofluorescence staining results showed Cbfβ deficiency significantly increased active β-catenin and TCF4 expression while reducing Yap, TGFβ1, and p-Smad 2/3 expression. Western blot and qPCR validated gene expression changes in hip articular cartilage of Cbfβ-deficient mice. Our results demonstrate that deficiency of Cbfβ in articular cartilage leads to an OA-like phenotype via affecting Hippo/Yap, TGFβ, and Wnt/β-catenin signaling pathways, disrupting articular cartilage homeostasis and leading to the pathological process of OA in mice. Our results indicate that targeting Cbfβ may be a potential therapeutic target for the design of novel and effective treatments for OA.

Cbfβ regulates Wnt/β-catenin, Hippo/Yap, and TGFβ signaling pathways in articular cartilage homeostasis and protects from ACLT surgery-induced osteoarthritis

As the most common degenerative joint disease, osteoarthritis (OA) contributes significantly to pain and disability during aging. Several genes of interest involved in articular cartilage damage in OA have been identified. However, the direct causes of OA are poorly understood. Evaluating the public human RNA-seq dataset showed that Cbfβ, (subunit of a heterodimeric Cbfβ/Runx1,Runx2, or Runx3 complex) expression is decreased in the cartilage of patients with OA. Here, we found that the chondrocyte-specific deletion of Cbfβ in tamoxifen-induced Cbfβf/fCol2α1-CreERT mice caused a spontaneous OA phenotype, worn articular cartilage, increased inflammation, and osteophytes. RNA-sequencing analysis showed that Cbfβ deficiency in articular cartilage resulted in reduced cartilage regeneration, increased canonical Wnt signaling and inflammatory response, and decreased Hippo/YAP signaling and TGF-β signaling. Immunostaining and western blot validated these RNA-seq analysis results. ACLT surgery-induced OA decreased Cbfβ and Yap expression and increased active β-catenin expression in articular cartilage, while local AAV-mediated Cbfβ overexpression promoted Yap expression and diminished active β-catenin expression in OA lesions. Remarkably, AAV-mediated Cbfβ overexpression in knee joints of mice with OA showed the significant protective effect of Cbfβ on articular cartilage in the ACLT OA mouse model. Overall, this study, using loss-of-function and gain-of-function approaches, uncovered that low expression of Cbfβ may be the cause of OA. Moreover, Local admission of Cbfβ may rescue and protect OA through decreasing Wnt/β-catenin signaling, and increasing Hippo/Yap signaling and TGFβ/Smad2/3 signaling in OA articular cartilage, indicating that local Cbfβ overexpression could be an effective strategy for treatment of OA.

The SUMOylation and ubiquitination crosstalk in cancer

BACKGROUND

The cancer occurrence and progression are largely affected by the post-translational modifications (PTMs) of proteins. Currently, it has been shown that the relationship between ubiquitination and SUMOylation is highly complex and interactive. SUMOylation affects the process of ubiquitination and degradation of substrates. Contrarily, SUMOylation-related proteins are also regulated by the ubiquitination process thus altering their protein levels or activity. Emerging evidence suggests that the abnormal regulation between this crosstalk may lead to tumorigenesis.

PURPOSE

In this review, we have discussed the study of the relationship between ubiquitination and SUMOylation, as well as the possibility of a corresponding application in tumor therapy.

METHODS

The relevant literatures from PubMed have been reviewed for this article.

CONCLUSION

The interaction between ubiquitination and SUMOylation is crucial for the occurrence and development of cancer. A greater understanding of the crosstalk of SUMOylation and ubiquitination may be more conducive to the development of more selective and effective SUMOylation inhibitors, as well as a promotion of synergy with other tumor treatment strategies.

ING1 inhibits Twist1 expression to block EMT and is antagonized by the HDAC inhibitor vorinostat

ING1 is a chromatin targeting subunit of the Sin3a histone deacetylase (HDAC) complex that alters chromatin structure to subsequently regulate gene expression. We find that ING1 knockdown increases expression of Twist1, Zeb 1&2, Snai1, Bmi1 and TSHZ1 drivers of EMT, promoting EMT and cell motility. ING1 expression had the opposite effect, promoting epithelial cell morphology and inhibiting basal and TGF-β-induced motility in 3D organoid cultures. ING1 binds the Twist1 promoter and Twist1 was largely responsible for the ability of ING1 to reduce cell migration. Consistent with ING1 inhibiting Twist1 expression in vivo, an inverse relationship between ING1 and Twist1 levels was seen in breast cancer samples from The Cancer Genome Atlas (TCGA). The HDAC inhibitor vorinostat is approved for treatment of multiple myeloma and cutaneous T cell lymphoma and is in clinical trials for solid tumours as adjuvant therapy. One molecular target of vorinostat is INhibitor of Growth 2 (ING2), that together with ING1 serve as targeting subunits of the Sin3a HDAC complex. Treatment with sublethal (LD25-LD50) levels of vorinostat promoted breast cancer cell migration several-fold, which increased further upon ING1 knockout. These observations indicate that correct targeting of the Sin3a HDAC complex, and HDAC activity in general decreases luminal and basal breast cancer cell motility, suggesting that use of HDAC inhibitors as adjuvant therapies in breast cancers that are prone to metastasize may not be optimal and requires further investigation.

Unraveling the Molecular Puzzle: Exploring Gene Networks across Diverse EMT Status of Cell Lines

Understanding complex disease mechanisms requires a comprehensive understanding of the gene regulatory networks, as complex diseases are often characterized by the dysregulation and dysfunction of molecular networks, rather than abnormalities in single genes. Specifically, the exploration of cell line-specific gene networks can provide essential clues for precision medicine, as this methodology can uncover molecular interplays specific to particular cell line statuses, such as drug sensitivity, cancer progression, etc. In this article, we provide a comprehensive review of computational strategies for cell line-specific gene network analysis: (1) cell line-specific gene regulatory network estimation and analysis of gene networks under varying epithelial-mesenchymal transition (EMT) statuses of cell lines; and (2) an explainable artificial intelligence approach for interpreting the estimated massive multiple EMT-status-specific gene networks. The objective of this review is to help readers grasp the concept of computational network biology, which holds significant implications for precision medicine by offering crucial clues.

Sumoylated SnoN interacts with HDAC1 and p300/CBP to regulate EMT-associated phenotypes in mammary organoids

Protein post-translational modification by the small ubiquitin-like modifier (SUMO) regulates the stability, subcellular localization, and interactions of protein substrates with consequences on cellular responses including epithelial-mesenchymal transition (EMT). Transforming growth factor beta (TGFβ) is a potent inducer of EMT with implications for cancer invasion and metastasis. The transcriptional coregulator SnoN suppresses TGFβ-induced EMT-associated responses in a sumoylation-dependent manner, but the underlying mechanisms have remained largely unknown. Here, we find that sumoylation promotes the interaction of SnoN with the epigenetic regulators histone deacetylase 1 (HDAC1) and histone acetylase p300 in epithelial cells. In gain and loss of function studies, HDAC1 suppresses, whereas p300 promotes, TGFβ-induced morphogenetic changes associated with EMT-related events in three-dimensional multicellular organoids derived from mammary epithelial cells or carcinomas. These findings suggest that sumoylated SnoN acts via the regulation of histone acetylation to modulate EMT-related effects in breast cell organoids. Our study may facilitate the discovery of new biomarkers and therapeutics in breast cancer and other epithelial cell-derived cancers.

The role of NEDD4 related HECT-type E3 ubiquitin ligases in defective autophagy in cancer cells: molecular mechanisms and therapeutic perspectives

The homologous to the E6-AP carboxyl terminus (HECT)-type E3 ubiquitin ligases are the selective executers in the protein ubiquitination, playing a vital role in modulation of the protein function and stability. Evidence shows the regulatory role of HECT-type E3 ligases in various steps of the autophagic process. Autophagy is an intracellular digestive and recycling process that controls the cellular hemostasis. Defective autophagy is involved in tumorigenesis and has been detected in various types of cancer cells. A growing body of findings indicates that HECT-type E3 ligases, in particular members of the neural precursor cell expressed developmentally downregulated protein 4 (NEDD4) including NEDD4-1, NEDD4-L, SMURFs, WWPs, and ITCH, play critical roles in dysregulation or dysfunction of autophagy in cancer cells. The present review focuses on NEDD4 E3 ligases involved in defective autophagy in cancer cells and discusses their autophagic function in different cancer cells as well as substrates and the signaling pathways in which they participate, conferring a basis for the cancer treatment through the modulating of these E3 ligases.

LIM and Cysteine-Rich Domains 1 Promotes Transforming Growth Factor β1–Induced Epithelial–Mesenchymal Transition in Human Kidney 2 Cells

Renal fibrosis is the major pathologic manifestation of chronic kidney disease (CKD). LIM and cysteine-rich domains 1 (LMCD1) is upregulated in the kidney tissue from patients with CKD and the transforming growth factor β1 (TGF-β1)-treated human renal tubular epithelial cell line human kidney 2 (HK-2) (Gene Expression Omnibus: GSE66494 and GSE23338). Previously, we have demonstrated that the knockdown of LMCD1 ameliorated renal fibrosis in mice by blocking the activation of the extracellular signal-regulated kinase pathway. In this study, we sought to further investigate whether LMCD1 affects TGF-β1-induced epithelial-mesenchymal transition (EMT) of kidney tubular epithelial cells and its potential role in the TGF-β1/Smad signaling pathway. First, we confirmed that LMCD1 expression was increased in the fibrotic kidneys of patients with CKD compared with that in normal kidneys and that LMCD1 was predominantly localized in the renal tubules. LMCD1 and mesenchymal markers were upregulated in obstructed kidney tissues of mice at 21 days after unilateral ureteral obstruction surgery compared with the tissues in sham mice. Next, we demonstrated that TGF-β1 significantly increased LMCD1 expression through Smad-mediated transcription in HK-2 cells in vitro. In turn, LMCD1 acted as a transcriptional coactivator of E2F transcription factor 1 to promote the transcription of TGF-β1. Moreover, TGF-β1 increased the interaction between LMCD1 and Smad ubiquitination regulatory factor 2 (Smurf2) and accelerated Smurf2-mediated LMCD1 degradation via the ubiquitination system. The knockdown of LMCD1 inhibited TGF-β1-induced EMT in both HK-2 cells and unilateral ureteral obstruction mice. Our results indicate a positive feedback loop between TGF-β1 and LMCD1 for EMT induction in HK-2 cells and that Smurf2 acts as a negative regulator in this process by accelerating LMCD1 degradation.

The SUMO components in rheumatoid arthritis

Small ubiquitin-like modifier (SUMO) proteins can reversibly attach covalently or non-covalently to lysine residues of various substrates. The processes are named SUMOylation and de-SUMOylation, which maintain a dynamic balance in the physiological state, and are regulated by SUMO components. However, the dysregulation of components disturbs the balance and alters the functions of target proteins, which causes the occurrence of diseases. To date, certain SUMO components, including SUMO-1, SUMO-2/3, SAE1/Uba2, Ubc9, PIASs (protein inhibitors of activated signal transducer and activator of transcription) and SENPs (SUMO-specific proteases), have been found to participate in the pathogenesis of RA and their potential value as therapeutic targets also have been highlighted. In addition, single nucleotide polymorphisms (SNPs) in the SUMO components have been reported to be associated with disease susceptibility. Until now, only the SNP site of SUMO-4 has been reported in RA. Here we provided a systematic overview of the general characteristics of SUMO components and highlighted a summary of their impact on RA.

Runx1 is a key regulator of articular cartilage homeostasis by orchestrating YAP, TGFβ, and Wnt signaling in articular cartilage formation and osteoarthritis

Runt-related transcription factor 1 (Runx1) plays a key role in cartilage formation, but its function in articular cartilage formation is unclear. We generated non-inducible and inducible Runx1-deficient mice (Runx1f/fCol2α1-Cre and Runx1f/fCol2α1-CreER mice) and found that chondrocyte-specific Runx1-deficient mice developed a spontaneous osteoarthritis (OA)-like phenotype and showed exacerbated articular cartilage destruction under OA, characterized by articular cartilage degradation and cartilage ossification, with decreased Col2α1 expression and increased Mmp13 and Adamts5 expression. RNA-sequencing analysis of hip articular cartilage from the Runx1f/fCol2α1-Cre mice compared to that from wild-type mice and subsequent validation analyses demonstrated that Runx1 is a central regulator in multiple signaling pathways, converging signals of the Hippo/Yap, TGFβ/Smad, and Wnt/β-catenin pathways into a complex network to regulate the expression of downstream genes, thereby controlling a series of osteoarthritic pathological processes. RNA-sequencing analysis of mutant knee joints showed that Runx1's role in signaling pathways in articular cartilage is different from that in whole knee joints, indicating that Runx1 regulation is tissue-specific. Histopathologic analysis confirmed that Runx1 deficiency decreased the levels of YAP and p-Smad2/3 and increased the levels of active β-catenin. Overexpression of Runx1 dramatically increased YAP expression in chondrocytes. Adeno-associated virus-mediated Runx1 overexpression in the knee joints of osteoarthritic mice showed the protective effect of Runx1 on articular cartilage damaged in OA. Our results notably showed that Runx1 is a central regulator of articular cartilage homeostasis by orchestrating the YAP, TGFβ, and Wnt signaling pathways in the formation of articular cartilage and OA, and targeting Runx1 and its downstream genes may facilitate the design of novel therapeutic approaches for OA.

TRAF4 hyperactivates HER2 signaling and contributes to Trastuzumab resistance in HER2-positive breast cancer

The HER2 receptor modulates downstream signaling by forming homodimers and heterodimers with other members of the HER family. For patients with HER2-positive breast cancer, Trastuzumab, an anti-HER2 monoclonal antibody as first-line therapy has shown significant survival benefits. However, the development of acquired resistance to Trastuzumab continues to be a significant obstacle. TNF receptor-associated factor 4 (TRAF4) upregulation was discovered to be associated with a worse clinical outcome. Here we identified TRAF4 overexpression as one of the putative mechanisms for HER2-positive breast cancer cells to maintain HER2 signaling during Trastuzumab treatment, while TRAF4 knockdown reduced HER2 stability and improved Trastuzumab sensitivity. Mechanistically, TRAF4 regulates HER2 level through its impact on SMAD specific E3 ubiquitin protein ligase protein 2 (SMURF2). The development of a membrane-associated protein complex containing HER2, TRAF4, and SMURF2 has been observed. SMURF2 bound to the HER2 cytoplasmic domain, and directly ubiquitinated it leading to HER2 degradation, whereas TRAF4 stabilized HER2 by degrading SMURF2 and inhibiting the binding of SMURF2 to HER2. Moreover, downregulation of TRAF4 has decreased the AKT/mTOR signaling. In conclusion, we discovered a new HER2 signaling regulation that involves the TRAF4-SMURF2 complex, a possible mechanism that might contribute to anti-HER2 resistance, making TRAF4 a viable target for treating HER2 + breast cancer.

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.

Ubiquitin ligases: guardians of mammalian development

Mammalian development demands precision. Millions of molecules must be properly located in temporal order, and their function regulated, to orchestrate important steps in cell cycle progression, apoptosis, migration and differentiation, to shape developing embryos. Ubiquitin and its associated enzymes act as cellular guardians to ensure precise spatio-temporal control of key molecules during each of these important cellular processes. Loss of precision results in numerous examples of embryological disorders or even cancer. This Review discusses the crucial roles of E3 ubiquitin ligases during key steps of early mammalian development and their roles in human disease, and considers how new methods to manipulate and exploit the ubiquitin regulatory machinery - for example, the development of molecular glues and PROTACs - might facilitate clinical therapy.

Tumor-suppressive role of Smad ubiquitination regulatory factor 2 in patients with colorectal cancer

Smad ubiquitination regulatory factor 2 (Smurf2) plays various roles in cancer progression. However, the correlation between Smurf2 and clinical outcomes has not been determined in patients diagnosed with colorectal cancer and colorectal liver metastases. We analyzed 66 patients with colorectal cancer who developed liver metastases. Smurf2 expression was assessed using immunohistochemical analysis of primary and metastatic liver tumors. High Smurf2 expression in both primary and metastatic tumors was significantly associated with longer overall survival time and time to surgical failure. Multivariate analyses revealed that low Smurf2 expression in primary tumors was an independent predictor of poor prognosis. In vitro experiments using colon cancer cell lines demonstrated that short interfering RNA knockdown of Smurf2 increased cell migration and tumor sphere formation. Western blot analyses revealed that Smurf2 knockdown increased the protein expression of epithelial cell adhesion molecule (EpCAM). Thus, in summary, high Smurf2 expression in cancer cells was found to be an independent predictor of better prognosis in patients with primary colorectal cancer and consequent liver metastases. The tumor-suppressive role of Smurf2 was found to be associated with cell migration and EpCAM expression; hence, Smurf2 can be considered a positive biomarker of cancer stem cell-like properties.

The Role of SUMO E3 Ligases in Signaling Pathway of Cancer Cells

Small ubiquitin-like modifier (SUMO)ylation is a reversible post-translational modification that plays a crucial role in numerous aspects of cell physiology, including cell cycle regulation, DNA damage repair, and protein trafficking and turnover, which are of importance for cell homeostasis. Mechanistically, SUMOylation is a sequential multi-enzymatic process where SUMO E3 ligases recruit substrates and accelerate the transfer of SUMO onto targets, modulating their interactions, localization, activity, or stability. Accumulating evidence highlights the critical role of dysregulated SUMO E3 ligases in processes associated with the occurrence and development of cancers. In the present review, we summarize the SUMO E3 ligases, in particular, the novel ones recently identified, and discuss their regulatory roles in cancer pathogenesis.

TFPI2 suppresses the interaction of TGF-β2 pathway regulators to promote endothelial-mesenchymal transition in diabetic nephropathy

Endothelial–mesenchymal transition (EndMT) is an important source of myofibroblasts, but also contributes to the progression of diabetic nephropathy (DN). By several differential gene expression analyses from the Gene Expression Omnibus (GEO) database, the tissue factor pathway inhibitor 2 (TFPI2) gene, known as a tumor suppressor, was shown to be dysregulated in DN; however, the potential role and regulatory mechanism of TFPI2 in DN are unclear. Here, we found abnormal upregulation of TFPI2 in the renal cortex of diabetic mice, accompanied by impaired renal function. We also injected a single dose of adeno-associated virus (AAV)2 carrying shRNA targeting TFPI2 intravenously into these mice and found that knockdown of TFPI2 improved renal function and reduced renal fibrosis and cell apoptosis in experimental DN. Furthermore, hyperglycemia-induced EndMT was inhibited in the absence of TFPI2, as evidenced by increased expression of endothelial markers (VE-cadherin and CD31) and decreased expression of mesenchymal markers (α-SMA, desmin, and FSP-1). To further explore the mechanism in vitro, human renal glomerular endothelial cells (hRGECs) were incubated in the presence of high glucose or transforming growth factor beta (TGF-β)2. TFPI2 deficiency inhibited high glucose-induced cell apoptosis and TGF-β2-induced EndMT in hRGECs, while overexpression of TFPI2 had the opposite effects. Importantly, TGF-β2 is a crucial driver of EndMT, and we found that TFPI2 promoted TGF-β2/Smad signaling activation by interferring the interaction of TGF-β pathway regulators (SMURF2 with SMAD7). Our results show that TFPI2 regulates EndMT and the TGF-β2 signaling pathway and is a potential promoter of DN pathogenesis.

SMURF2 phosphorylation at Thr249 modifies glioma stemness and tumorigenicity by regulating TGF-β receptor stability

Glioma stem cells (GSCs) contribute to the pathogenesis of glioblastoma, the most malignant form of glioma. The implication and underlying mechanisms of SMAD specific E3 ubiquitin protein ligase 2 (SMURF2) on the GSC phenotypes remain unknown. We previously demonstrated that SMURF2 phosphorylation at Thr²⁴⁹ (SMURF2^Thr249) activates its E3 ubiquitin ligase activity. Here, we demonstrate that SMURF2^Thr249 phosphorylation plays an essential role in maintaining GSC stemness and tumorigenicity. SMURF2 silencing augmented the self-renewal potential and tumorigenicity of patient-derived GSCs. The SMURF2^Thr249 phosphorylation level was low in human glioblastoma pathology specimens. Introduction of the SMURF2^T249A mutant resulted in increased stemness and tumorigenicity of GSCs, recapitulating the SMURF2 silencing. Moreover, the inactivation of SMURF2^Thr249 phosphorylation increases TGF-β receptor (TGFBR) protein stability. Indeed, TGFBR1 knockdown markedly counteracted the GSC phenotypes by SMURF2^T249A mutant. These findings highlight the importance of SMURF2^Thr249 phosphorylation in maintaining GSC phenotypes, thereby demonstrating a potential target for GSC-directed therapy.

Hiraiwa et al. show that phosphorylation of SMAD specific E3 ubiquitin protein ligase 2 (SMURF2) at Thr249 mediates ubiquitylation and degradation of the TGF-β receptor TGBR1 leading to loss of glioblastoma stem cell tumorigenic capacity. Their data elucidates a mechanism of regulation of the TGF-β signaling pathway that controls the stem cell status in glioblastoma.

BORIS/CTCFL expression activates the TGFβ signaling cascade and induces Drp1 mediated mitochondrial fission in neuroblastoma

The cancer-testis antigen CTCFL/BORIS (Brother of Regulator of Imprinted Sites) also known, as a paralog of CTCF -the "master weaver of the genome" is a key transcriptional regulator. Both CTCF and BORIS can bind to the same promoter sequence and recruit diverse proteins. BORIS is also known to be associated with actively translating ribosomes suggesting new roles of BORIS in gene expression. Various studies have attempted to elucidate the role of BORIS in different cell types for the development of targeted therapy depending on molecular signatures and genetic aberrations associated with the disease type. The current study is focused on its role in neuroblastoma. Here, we have deciphered the role of BORIS on TGFβ1 pathway which is highly affected by embryonic CTCFL expression. BORIS stabilized the SMAD3 and SMAD4 transcripts leading to prolonged TGFβ activation. Further, loss of BORIS abrogated both the canonical and non-canonical TGFβ signaling suggesting the dependency of TGFβ on BORIS. The effect on the metabolic profile of the neuroblastoma cells were analyzed with change in BORIS expression levels. Also, ectopic expression of BORIS leads to Drp1 phosphorylation (Ser616) enhancing mitochondrial fission followed by a switch in cellular metabolism towards glycolysis. This cellular metabolism switch was in turn supported with a reduction in oxygen consumption rate upon BORIS expression. Interestingly methylome analysis revealed patterns of global histone methylation, a mechanism that regulate important signaling pathways in neuroblastoma. This study analyzes the consequence of BORIS expression in neuroblastoma cells and thereby elucidate its downstream targets, which could help in designing effective therapeutic for treating neuroblastoma. Similar results were obtained in both MYCN amplified and non-MYCN neuroblastoma cell lines, indicating a common mechanism of BORIS/CTCFL action in neuroblastoma.

Regulation of transforming growth factor-β signalling by SUMOylation and its role in fibrosis

Fibrosis is an abnormal healing process that only repairs the structure of an organ after injury and does not address damaged functions. The pathogenesis of fibrosis is multifactorial and highly complex; numerous signalling pathways are involved in this process, with the transforming growth factor-β (TGF-β) signalling pathway playing a central role. TGF-β regulates the generation of myofibroblasts and the epithelial-mesenchymal transition by regulating transcription and translation of downstream genes and precisely regulating fibrogenesis. The TGF-β signalling pathway can be modulated by various post-translational modifications, of which SUMOylation has been shown to play a key role. In this review, we focus on the function of SUMOylation in canonical and non-canonical TGF-β signalling and its role in fibrosis, providing promising therapeutic strategies for fibrosis.

Therapeutic Potential of Targeting the SUMO Pathway in Cancer

SUMOylation is a dynamic and reversible post-translational modification, characterized more than 20 years ago, that regulates protein function at multiple levels. Key oncoproteins and tumor suppressors are SUMO substrates. In addition to alterations in SUMO pathway activity due to conditions typically present in cancer, such as hypoxia, the SUMO machinery components are deregulated at the genomic level in cancer. The delicate balance between SUMOylation and deSUMOylation is regulated by SENP enzymes possessing SUMO-deconjugation activity. Dysregulation of SUMO machinery components can disrupt the balance of SUMOylation, contributing to the tumorigenesis and drug resistance of various cancers in a context-dependent manner. Many molecular mechanisms relevant to the pathogenesis of specific cancers involve SUMO, highlighting the potential relevance of SUMO machinery components as therapeutic targets. Recent advances in the development of inhibitors targeting SUMOylation and deSUMOylation permit evaluation of the therapeutic potential of targeting the SUMO pathway in cancer. Finally, the first drug inhibiting SUMO pathway, TAK-981, is currently also being evaluated in clinical trials in cancer patients. Intriguingly, the inhibition of SUMOylation may also have the potential to activate the anti-tumor immune response. Here, we comprehensively and systematically review the recent developments in understanding the role of SUMOylation in cancer and specifically focus on elaborating the scientific rationale of targeting the SUMO pathway in different cancers.

SUMOylation Wrestles With the Occurrence and Development of Breast Cancer

Breast cancer has the highest incidence among cancers and is the most frequent cause of death in women worldwide. The detailed mechanism of the pathogenesis of breast cancer has not been fully elucidated, and there remains a lack of effective treatment methods for the disease. SUMOylation covalently conjugates a large amount of cellular proteins, and affects their cellular localization and biological activity to participate in numerous cellular processes. SUMOylation is an important process and imbalance of SUMOylation results in the progression of human diseases. Increasing evidence shows that numerous SUMOylated proteins are involved in the occurrence and development of breast cancer. This review summarizes a series of studies on protein SUMOylation in breast cancer in recent years. The study of SUMOylated proteins provides a comprehensive understanding of the pathophysiology of breast cancer and provides evolving therapeutic strategies for the treatment of breast cancer.

Posttranslational Modifications of Smurfs: Emerging Regulation in Cancer

Smad ubiquitination regulatory factors (Smurfs) belong to the Nedd4 subfamily of HECT-type E3 ubiquitin ligases. Under normal situations, Smurfs are exactly managed by upstream regulators, and thereby strictly control tumor biological processes, including cell growth, differentiation, apoptosis, polarization, epithelial mesenchymal transition (EMT), and invasion. Disruption of Smurf activity has been implicated in cancer progression, and Smurf activity is controlled by a series of posttranslational modifications (PTMs), including phosphorylation, ubiquitination, neddylation, sumoylation, and methylation. The effect and function of Smurfs depend on PTMs and regulate biological processes. Specifically, these modifications regulate the functional expression of Smurfs by affecting protein degradation and protein interactions. In this review, we summarize the complexity and diversity of Smurf PTMs from biochemical and biological perspectives and highlight the understanding of their roles in cancer.

Adaptors as the regulators of HECT ubiquitin ligases

The HECT (homologous to E6AP C-terminus) ubiquitin ligases (E3s) are a small family of highly conserved enzymes involved in diverse cellular functions and pathological conditions. Characterised by a C-terminal HECT domain that accepts ubiquitin from E2 ubiquitin conjugating enzymes, these E3s regulate key signalling pathways. The activity and functional regulation of HECT E3s are controlled by several factors including post-translational modifications, inter- and intramolecular interactions and binding of co-activators and adaptor proteins. In this review, we focus on the regulation of HECT E3s by accessory proteins or adaptors and discuss various ways by which adaptors mediate their regulatory roles to affect physiological outcomes. We discuss common features that are conserved from yeast to mammals, regardless of the type of E3s as well as shed light on recent discoveries explaining some existing enigmas in the field.

SUMOylation of the ubiquitin ligase IDOL decreases LDL receptor levels and is reversed by SENP1

Inducible degrader of the low-density lipoprotein receptor (IDOL) is an E3 ubiquitin ligase mediating degradation of low-density lipoprotein (LDL) receptor (LDLR). IDOL also controls its own stability through autoubiquitination, primarily at lysine 293. Whether IDOL may undergo other forms of posttranslational modification is unknown. In this study, we show that IDOL can be modified by small ubiquitin-like modifier 1 at the K293 residue at least. The SUMOylation of IDOL counteracts its ubiquitination and augments IDOL protein levels. SUMOylation and the associated increase of IDOL protein are effectively reversed by SUMO-specific peptidase 1 (SENP1) in an activity-dependent manner. We further demonstrate that SENP1 affects LDLR protein levels by modulating IDOL. Overexpression of SENP1 increases LDLR protein levels and enhances LDL uptake in cultured cells. On the contrary, loss of SENP1 lowers LDLR levels in an IDOL-dependent manner and reduces LDL endocytosis. Collectively, our results reveal SUMOylation as a new regulatory posttranslational modification of IDOL and suggest that SENP1 positively regulates the LDLR pathway via deSUMOylation of IDOL and may therefore be exploited for the treatment of cardiovascular disease.

Global gene network exploration based on explainable artificial intelligence approach

In recent years, personalized gene regulatory networks have received significant attention, and interpretation of the multilayer networks has been a critical issue for a comprehensive understanding of gene regulatory systems. Although several statistical and machine learning approaches have been developed and applied to reveal sample-specific regulatory pathways, integrative understanding of the massive multilayer networks remains a challenge. To resolve this problem, we propose a novel artificial intelligence (AI) strategy for comprehensive gene regulatory network analysis. In our strategy, personalized gene networks corresponding specific clinical characteristic are constructed and the constructed network is considered as a second-order tensor. Then, an explainable AI method based on deep learning is applied to decompose the multilayer networks, thus we can reveal all-encompassing gene regulatory systems characterized by clinical features of patients. To evaluate the proposed methodology, we apply our method to the multilayer gene networks under varying conditions of an epithelial–mesenchymal transition (EMT) process. From the comprehensive analysis of multilayer networks, we identified novel markers, and the biological mechanisms of the identified genes and their reciprocal mechanisms are verified through the literature. Although any biological knowledge about the identified genes was not incorporated in our analysis, our data-driven approach based on AI approach provides biologically reliable results. Furthermore, the results provide crucial evidences to reveal biological mechanism related to various diseases, e.g., keratinocyte proliferation. The use of explainable AI method based on the tensor decomposition enables us to reveal global and novel mechanisms of gene regulatory system from the massive multiple networks, which cannot be demonstrated by existing methods. We expect that the proposed method provides a new insight into network biology and it will be a useful tool to integrative gene network analysis related complex architectures of diseases.

Regulation of Epithelial-Mesenchymal Plasticity by the E3 Ubiquitin-Ligases in Cancer

The epithelial-mesenchymal plasticity (EMP) is a process by which epithelial cells acquire the ability to dynamically switch between epithelial and mesenchymal phenotypic cellular states. Epithelial cell plasticity in the context of an epithelial-to-mesenchymal transition (EMT) confers increased cell motility, invasiveness and the ability to disseminate to distant sites and form metastasis. The modulation of molecularly defined targets involved in this process has become an attractive therapeutic strategy against cancer. Protein degradation carried out by ubiquitination has gained attention as it can selectively degrade proteins of interest. In the ubiquitination reaction, the E3 ubiquitin-ligases are responsible for the specific binding of ubiquitin to a small subset of target proteins, and are considered promising anticancer drug targets. In this review, we summarize the role of the E3 ubiquitin-ligases that control targeted protein degradation in cancer-EMT, and we highlight the potential use of the E3 ubiquitin-ligases as drug targets for the development of small-molecule drugs against cancer.

Regulation of epithelial-mesenchymal transition and organoid morphogenesis by a novel TGFβ-TCF7L2 isoform-specific signaling pathway

Alternative splicing contributes to diversification of gene function, yet consequences of splicing on functions of specific gene products is poorly understood. The major transcription factor TCF7L2 undergoes alternative splicing but the biological significance of TCF7L2 isoforms has remained largely to be elucidated. Here, we find that the TCF7L2 E-isoforms maintain, whereas the M and S isoforms disrupt morphogenesis of 3D-epithelial cell-derived organoids via regulation of epithelial-mesenchymal transition (EMT). Remarkably, TCF7L2E2 antagonizes, whereas TCF7L2M2/S2 promotes EMT-like effects in epithelial cells induced by transforming growth factor beta (TGFβ) signaling. In addition, we find TGFβ signaling reduces the proportion of TCF7L2E to TCF7L2M/S protein in cells undergoing EMT. We also find that TCF7L2 operates via TGFβ-Smad3 signaling to regulate EMT. Collectively, our findings unveil novel isoform-specific functions for the major transcription factor TCF7L2 and provide novel links between TCF7L2 and TGFβ signaling in the control of EMT-like responses and epithelial tissue morphogenesis.

PIAS1 and TIF1γ collaborate to promote SnoN SUMOylation and suppression of epithelial-mesenchymal transition

SUMO E3 ligases specify protein substrates for SUMOylation. The SUMO E3 ligases PIAS1 and TIF1γ target the transcriptional regulator SnoN for SUMOylation leading to suppression of epithelial-mesenchymal transition (EMT). Whether and how TIF1γ and PIAS1 might coordinate SnoN SUMOylation and regulation of EMT remained unknown. Here, we reveal that SnoN associates simultaneously with both TIF1γ and PIAS1, leading to a trimeric protein complex. Hence, PIAS1 and TIF1γ collaborate to promote the SUMOylation of SnoN. Importantly, loss of function studies of PIAS1 and TIF1γ suggest that these E3 ligases act in an interdependent manner to suppress EMT of breast cell-derived tissue organoids. Collectively, our findings unveil a novel mechanism by which SUMO E3 ligases coordinate substrate SUMOylation with biological implications.

The Post-translational Modifications of Smurf2 in TGF-β Signaling

Smad ubiquitin regulatory factor 2 (Smurf2), an essential negative regulator of TGF-β signaling, ubiquitinates TGF-β receptors (TβRs) and Smad proteins, inducing their proteasomal degradation. Smurf2 plays crucial roles in regulating TGF-β signaling and maintaining normal cellular functions and tissue homeostasis; dysfunction of Smurf2 triggers abnormal TGF-β signaling in pathological states. Smurf2 has been reported as a potentially strong candidate for targeting therapies for related diseases. Recent work has begun to focus on the regulation of Smurf2 itself, and emerging evidence indicates that Smurf2 is regulated by post-translational modifications (PTMs) mechanisms. These mechanisms predominantly regulate the expression level and E3 ligase activity of Smurf2, strongly suggesting that this protein contributes to complicated roles under multiple pathophysiological conditions. In this review, we cover some significant and novel mechanisms of the PTMs that potentially control Smurf2 participation in TGF-β signaling, including ubiquitylation, SUMOylation, neddylation, phosphorylation, and methylation in order to provide a broad view of the depth and sophistication of Smurf2 function in TGF-β regulation, as well as perspectives for future therapeutic directions for its associated diseases.

The Role of miR-200b-3p in Modulating TGF-β1-induced Injury in Human Bronchial Epithelial Cells

BACKGROUND

Dysregulation of microRNAs (miRNAs) has been implicated in airway diseases where transforming growth factor-β (TGF-β)-induced epithelial-mesenchymal transition (EMT) may contribute to pathophysiology. Our study investigated the role of miRNA-200b in TGF-β1-induced EMT in human bronchial epithelial cells.

METHODS

NanoString nCounter miRNA assay was used to profile miRNA in control versus TGF-β1 (1, 4, and 24 h) stimulated BEAS-2B cells. Immortalized primary bronchial epithelial cell line (BEAS-2B cells), human primary bronchial epithelial cells (PBECs), and PBECs derived post-lung transplant were transfected with miR-200b-3p mimics and EMT marker expression was examined at RNA and protein level. miRNA target studies were performed and validated using computational tools and luciferase assay. In situ hybridization was done on normal lung tissue to localize miR-200b-3p in airway epithelium.

RESULTS

miR-200b-3p was downregulated post-TGF-β1 treatment compared with control in BEAS-2B. miR-200b-3p mimic transfection before TGF-β1 stimulation maintained epithelial marker expression and downregulated mesenchymal cell markers at RNA and protein level in BEAS-2B cells and PBECs. Furthermore, miR-200b-3p mimics reversed established TGF-β1-induced EMT in BEAS-2B cells. miR-200b-3p targets, ZNF532, and ZEB2 were validated as direct targets using luciferase assay. miR-200b-3p mimics suppress TGF-β1-induced EMT via inhibition of ZNF532 and ZEB2. In situ hybridization showed that miR-200b-3p is expressed in the normal lung epithelium. Additionally, miR-200b-3p mimics inhibit EMT in the presence of TGF-β1 in PBECs derived from lung allograft.

CONCLUSIONS

We provide proof of concept that miR-200b-3p protects airway epithelial cells from EMT. Manipulating miR-200b-3p expression may represent a novel therapeutic modulator in airway pathophysiology.

Expression Levels of SMAD Specific E3 Ubiquitin Protein Ligase 2 (Smurf2) and its Interacting Partners Show Region-specific Alterations During Brain Aging

Aging occurs due to a combination of several factors, such as telomere attrition, cellular senescence, and stem cell exhaustion. The telomere attrition-dependent cellular senescence is regulated by increased levels of SMAD specific E3 ubiquitin protein ligase 2 (smurf2). With age smurf2 expression increases and Smurf2 protein interacts with several regulatory proteins including, Smad7, Ep300, Yy1, Sirt1, Mdm2, and Tp53, likely affecting its function related to cellular aging. The current study aimed at analyzing smurf2 expression in the aged brain because of its potential regulatory roles in the cellular aging process. Zebrafish were used because like humans they age gradually and their genome has 70% similarity. In the current study, we demonstrated that smurf2 gene and protein expression levels altered in a region-specific manner during the aging process. Also, in both young and old brains, Smurf2 protein was enriched in the cytosol. These results imply that during aging Smurf2 is regulated by several mechanisms including post-translational modifications (PTMs) and complex formation. Also, the expression levels of its interacting partners defined by the STRING database, tp53, mdm2, ep300a, yy1a, smad7, and sirt1, were analyzed. Multivariate analysis indicated that smurf2, ep300a, and sirt1, whose proteins regulate ubiquitination, acetylation, and deacetylation of target proteins including Smad7 and Tp53, showed age- and brain region-dependent patterns. Our data suggest a likely balance between Smurf2- and Mdm2-mediated ubiquitination, and Ep300a-mediated acetylation/Sirt1-mediated deacetylation, which most possibly affects the functionality of other interacting partners in regulating cellular and synaptic aging and ultimately cognitive dysfunction.

SMURF2 prevents detrimental changes to chromatin, protecting human dermal fibroblasts from chromosomal instability and tumorigenesis

E3 ubiquitin ligases (E3s) play essential roles in the maintenance of tissue homeostasis under normal and stress conditions, as well as in disease states, particularly in cancer. However, the role of E3s in the initiation of human tumors is poorly understood. Previously, we reported that genetic ablation of the HECT-type E3 ubiquitin ligase Smurf2 induces carcinogenesis in mice; but whether and how these findings are pertinent to the inception of human cancer remain unknown. Here we show that SMURF2 is essential to protect human dermal fibroblasts (HDFs) from malignant transformation, and its depletion converts HDFs into tumorigenic entity. This phenomenon was associated with the radical changes in chromatin structural and epigenetic landscape, dysregulated gene expression and cell-cycle control, mesenchymal-to-epithelial transition and impaired DNA damage response. Furthermore, we show that SMURF2-mediated tumor suppression is interlinked with SMURF2's ability to regulate the expression of two central chromatin modifiers-an E3 ubiquitin ligase RNF20 and histone methyltransferase EZH2. Silencing these factors significantly reduced the growth and transformation capabilities of SMURF2-depleted cells. Finally, we demonstrate that SMURF2-compromised HDFs are highly tumorigenic in nude mice. These findings suggest the critical role that SMURF2 plays in preventing malignant alterations, chromosomal instability and cancer.

The role of proteases in epithelial-to-mesenchymal cell transitions in cancer

Changing the characteristics of cells from epithelial states to mesenchymal properties is a key process involved in developmental and physiological processes as well as in many diseases with cancer as the most prominent example. Nowadays, a great deal of work and literature concerns the understanding of the process of epithelial-to-mesenchymal transition (EMT) in terms of its molecular regulation and its implications for cancer. Similar statements can certainly be made regarding the investigation of the more than 500 proteases typically encoded by a mammalian genome. Specifically, the impact of proteases on tumor biology has been a long-standing topic of interest. However, although EMT actively regulates expression of many proteases and proteolytic enzymes are clearly involved in survival, division, differentiation, and movements of cells, information on the diverse roles of proteases in EMT has been rarely compiled. Here we aim to conceptually connect the scientific areas of "EMT" and "protease" research by describing how several important classes of proteolytic enzymes are regulated by EMT and how they are involved in initiation and execution of the EMT program. To do so, we briefly introduce the evolving key features of EMT and its regulation followed by discussion of protease involvement in this process.

Ubiquitin, SUMO, and Nedd8 as Therapeutic Targets in Cancer

Ubiquitin defines a family of approximately 20 peptidic posttranslational modifiers collectively called the Ubiquitin-like (UbLs). They are conjugated to thousands of proteins, modifying their function and fate in many ways. Dysregulation of these modifications has been implicated in a variety of pathologies, in particular cancer. Ubiquitin, SUMO (-1 to -3), and Nedd8 are the best-characterized UbLs. They have been involved in the regulation of the activity and/or the stability of diverse components of various oncogenic or tumor suppressor pathways. Moreover, the dysregulation of enzymes responsible for their conjugation/deconjugation has also been associated with tumorigenesis and cancer resistance to therapies. The UbL system therefore constitutes an attractive target for developing novel anticancer therapeutic strategies. Here, we review the roles and dysregulations of Ubiquitin, SUMO, and Nedd8 pathways in tumorigenesis, as well as recent advances in the identification of small molecules targeting their conjugating machineries for potential application in the fight against cancer.

The functions and regulation of Smurfs in cancers

Smad ubiquitination regulatory factor 1 (Smurf1) and Smurf2 are HECT-type E3 ubiquitin ligases, and both Smurfs were initially identified to regulate Smad protein stability in the TGF-β/BMP signaling pathway. In recent years, Smurfs have exhibited E3 ligase-dependent and -independent activities in various kinds of cells. Smurfs act as either potent tumor promoters or tumor suppressors in different tumors by regulating biological processes, including metastasis, apoptosis, cell cycle, senescence and genomic stability. The regulation of Smurfs activity and expression has therefore emerged as a hot spot in tumor biology research. Further, the Smurf1- or Smurf2-deficient mice provide more in vivo clues for the functional study of Smurfs in tumorigenesis and development. In this review, we summarize these milestone findings and, in turn, reveal new avenues for the prevention and treatment of cancer by regulating Smurfs.

TGF-β in Hepatic Stellate Cell Activation and Liver Fibrogenesis-Updated 2019

Liver fibrosis is an advanced liver disease condition, which could progress to cirrhosis and hepatocellular carcinoma. To date, there is no direct approved antifibrotic therapy, and current treatment is mainly the removal of the causative factor. Transforming growth factor (TGF)-β is a master profibrogenic cytokine and a promising target to treat fibrosis. However, TGF-β has broad biological functions and its inhibition induces non-desirable side effects, which override therapeutic benefits. Therefore, understanding the pleiotropic effects of TGF-β and its upstream and downstream regulatory mechanisms will help to design better TGF-β based therapeutics. Here, we summarize recent discoveries and milestones on the TGF-β signaling pathway related to liver fibrosis and hepatic stellate cell (HSC) activation, emphasizing research of the last five years. This comprises impact of TGF-β on liver fibrogenesis related biological processes, such as senescence, metabolism, reactive oxygen species generation, epigenetics, circadian rhythm, epithelial mesenchymal transition, and endothelial-mesenchymal transition. We also describe the influence of the microenvironment on the response of HSC to TGF-β. Finally, we discuss new approaches to target the TGF-β pathway, name current clinical trials, and explain promises and drawbacks that deserve to be adequately addressed.

MiR-195 and miR-497 suppress tumorigenesis in lung cancer by inhibiting SMURF2-induced TGF-β receptor I ubiquitination

SMURF2 is a member of the HECT family of E3 ubiquitin ligases that have important roles as a negative regulator of transforming growth factor‐β (TGF‐β) signaling through ubiquitin‐mediated degradation of TGF‐β receptor I. However, the regulatory mechanism of SMURF2 is largely unknown. In this study, we identified that micro(mi)R‐195 and miR‐497 putatively target SMURF2 using several target prediction databases. Both miR‐195 and miR‐497 bind to the 3′‐UTR of the SMURF2 mRNA and inhibit SMURF2 expression. Furthermore, miR‐195 and miR‐497 regulate SMURF2‐dependent TβRI ubiquitination and cause the activation of the TGF‐β signaling pathway in lung cancer cells. Upregulation of miR‐195 and miR‐497 significantly reduced cell viability and colony formation through the activation of TGF‐β signaling. Interestingly, miR‐195 and miR‐497 also reduced the invasion ability of lung cancer cells when cells were treated with TGF‐β1. Subsequent in vivo studies in xenograft nude mice model revealed that miR‐195 and miR‐497 repress tumor growth. These findings demonstrate that miR‐195 and miR‐497 act as a tumor suppressor by suppressing ubiquitination‐mediated degradation of TGF‐β receptors through SMURF2, and suggest that miR‐195 and miR‐497 are potential therapeutic targets for lung cancer.

TTC3 contributes to TGF-β1-induced epithelial-mesenchymal transition and myofibroblast differentiation, potentially through SMURF2 ubiquitylation and degradation

Transforming growth factor-β (TGF-β) acts as a key cytokine in epithelial−mesenchymal transition (EMT) and myofibroblast differentiation, which are important for normal tissue repair and fibrotic diseases. Ubiquitylation and proteasomal degradation of TGF-β signaling proteins acts as a regulatory mechanism for the precise control of TGF-β signaling. SMAD-specific ubiquitin E3 ligase (SMAD ubiquitination regulatory factor 2, SMURF2) controls TGF-β signaling proteins including the TGF-β receptor (TGFR) and SMAD2/3. Here, we report that tetratricopeptide repeat domain 3 (TTC3), a ubiquitin E3 ligase, positively regulates TGF-β₁-induced EMT and myofibroblast differentiation, through inducing ubiquitylation and proteasomal degradation of SMURF2. In human bronchial epithelial cells (BEAS-2B) and normal human lung fibroblasts, TTC3 knockdown suppressed TGF-β₁-induced EMT and myofibroblast differentiation, respectively. Similarly, when TTC3 expression was suppressed, the TGF-β₁-stimulated elevation of p-SMAD2, SMAD2, p-SMAD3, and SMAD3 were inhibited. In contrast, overexpression of TTC3 caused both EMT and myofibroblast differentiation in the absence of TGF-β₁ treatment. TGF-β₁ reduced SMURF2 levels and TTC3 overexpression led to a further decrease in SMURF2 levels, while TTC3 knockdown inhibited TGF-β₁-induced SMURF2 reduction. In cell and in vitro ubiquitylation assays demonstrated TTC3-mediated SMURF2 ubiquitylation, and coimmunoprecipitation assays established the binding between SMURF2 and TTC3. TGF-β₁-induced TTC3 expression was inhibited by the knockdown of SMAD2 and SMAD3. Finally, Ttc3 mRNA levels were significantly increased and Smurf2 protein levels were significantly decreased in the lungs of mice treated with bleomycin as compared with the lungs of control mice. Collectively, these data suggest that TTC3 may contribute to TGF-β₁-induced EMT and myofibroblast differentiation, potentially through SMURF2 ubiquitylation/proteasomal degradation and subsequent inhibition of SMURF2-mediated suppression of SMAD2 and SMAD3, which in turn induces TTC3 expression.

Extra-virgin olive oil contains a metabolo-epigenetic inhibitor of cancer stem cells

Targeting tumor-initiating, drug-resistant populations of cancer stem cells (CSC) with phytochemicals is a novel paradigm for cancer prevention and treatment. We herein employed a phenotypic drug discovery approach coupled to mechanism-of-action profiling and target deconvolution to identify phenolic components of extra virgin olive oil (EVOO) capable of suppressing the functional traits of CSC in breast cancer (BC). In vitro screening revealed that the secoiridoid decarboxymethyl oleuropein aglycone (DOA) could selectively target subpopulations of epithelial-like, aldehyde dehydrogenase (ALDH)-positive and mesenchymal-like, CD44⁺CD24^−/low CSC. DOA could potently block the formation of multicellular tumorspheres generated from single-founder stem-like cells in a panel of genetically diverse BC models. Pretreatment of BC populations with noncytotoxic doses of DOA dramatically reduced subsequent tumor-forming capacity in vivo. Mice orthotopically injected with CSC-enriched BC-cell populations pretreated with DOA remained tumor-free for several months. Phenotype microarray-based screening pointed to a synergistic interaction of DOA with the mTOR inhibitor rapamycin and the DNA methyltransferase (DNMT) inhibitor 5-azacytidine. In silico computational studies indicated that DOA binds and inhibits the ATP-binding kinase domain site of mTOR and the S-adenosyl-l-methionine (SAM) cofactor-binding pocket of DNMTs. FRET-based Z-LYTE™ and AlphaScreen-based in vitro assays confirmed the ability of DOA to function as an ATP-competitive mTOR inhibitor and to block the SAM-dependent methylation activity of DNMTs. Our systematic in vitro, in vivo and in silico approaches establish the phenol-conjugated oleoside DOA as a dual mTOR/DNMT inhibitor naturally occurring in EVOO that functionally suppresses CSC-like states responsible for maintaining tumor-initiating cell properties within BC populations.

Regulating the human HECT E3 ligases

Ubiquitination, the covalent attachment of ubiquitin to proteins, by E3 ligases of the HECT (homologous to E6AP C terminus) family is critical in controlling diverse physiological pathways. Stringent control of HECT E3 ligase activity and substrate specificity is essential for cellular health, whereas deregulation of HECT E3s plays a prominent role in disease. The cell employs a wide variety of regulatory mechanisms to control HECT E3 activity and substrate specificity. Here, we summarize the current understanding of these regulatory mechanisms that control HECT E3 function. Substrate specificity is generally determined by interactions of adaptor proteins with domains in the N-terminal extensions of HECT E3 ligases. These N-terminal domains have also been found to interact with the HECT domain, resulting in the formation of inhibitory conformations. In addition, catalytic activity of the HECT domain is commonly regulated at the level of E2 recruitment and through HECT E3 oligomerization. The previously mentioned regulatory mechanisms can be controlled through protein-protein interactions, post-translational modifications, the binding of calcium ions, and more. Functional activity is determined not only by substrate recruitment and catalytic activity, but also by the type of ubiquitin polymers catalyzed to the substrate. While this is often determined by the specific HECT member, recent studies demonstrate that HECT E3s can be modulated to alter the type of ubiquitin polymers they catalyze. Insight into these diverse regulatory mechanisms that control HECT E3 activity may open up new avenues for therapeutic strategies aimed at inhibition or enhancement of HECT E3 function in disease-related pathways.

The SUMO System and TGFβ Signaling Interplay in Regulation of Epithelial-Mesenchymal Transition: Implications for Cancer Progression

Protein post-translational modification by the small ubiquitin-like modifier (SUMO), or SUMOylation, can regulate the stability, subcellular localization or interactome of a protein substrate with key consequences for cellular processes including the Epithelial-Mesenchymal Transition (EMT). The secreted protein Transforming Growth Factor beta (TGFβ) is a potent inducer of EMT in development and homeostasis. Importantly, the ability of TGFβ to induce EMT has been implicated in promoting cancer invasion and metastasis, resistance to chemo/radio therapy, and maintenance of cancer stem cells. Interestingly, TGFβ-induced EMT and the SUMO system intersect with important implications for cancer formation and progression, and novel therapeutics identification.