PTPN3 acts as a tumor suppressor and boosts TGF-ß signaling independent of its phosphatase activity.

TGF-ß controls a variety of cellular functions during development. Abnormal TGF-ß responses are commonly found in human diseases such as cancer, suggesting that TGF-ß signaling must be tightly regulated. Here, we report that protein tyrosine phosphatase non-receptor 3 (PTPN3) profoundly potentiates TGF-ß signaling independent of its phosphatase activity. PTPN3 stabilizes TGF-ß type I receptor (TßRI) through attenuating the interaction between Smurf2 and TßRI. Consequently, PTPN3 facilitates TGF-ß-induced R-Smad phosphorylation, transcriptional responses, and subsequent physiological responses. Importantly, the leucine-to-arginine substitution at amino acid residue 232 (L232R) of PTPN3, a frequent mutation found in intrahepatic cholangiocarcinoma (ICC), disables its role in enhancing TGF-ß signaling and abolishes its tumor-suppressive function. Our findings have revealed a vital role of PTPN3 in regulating TGF-ß signaling during normal physiology and pathogenesis.

Current perspectives on inhibitory SMAD7 in health and disease.

Transforming growth factor ß (TGF-ß) family members play an extensive role in cellular communication that orchestrates both early development and adult tissue homeostasis. Aberrant TGF-ß family signaling is associated with a pathological outcome in numerous diseases, and in-depth understanding of molecular and cellular processes could result in therapeutic benefit for patients. Canonical TGF-ß signaling is mediated by receptor-regulated SMADs (R-SMADs), a single co-mediator SMAD (Co-SMAD), and inhibitory SMADs (I-SMADs). SMAD7, one of the I-SMADs, is an essential negative regulator of the pleiotropic TGF-ß and bone morphogenetic protein (BMP) signaling pathways. In a negative feedback loop, SMAD7 inhibits TGF-ß signaling by providing competition for TGF-ß type-1 receptor (TßRI), blocking phosphorylation and activation of SMAD2. Moreover, SMAD7 recruits E3 ubiquitin SMURF ligases to the type I receptor to promote ubiquitin-mediated proteasomal degradation. In addition to its role in TGF-ß and BMP signaling, SMAD7 is regulated by and implicated in a variety of other signaling pathways and functions as a mediator of crosstalk. This review is focused on SMAD7, its function in TGF-ß and BMP signaling, and its role as a downstream integrator and crosstalk mediator. This crucial signaling molecule is tightly regulated by various mechanisms. We provide an overview of the ways by which SMAD7 is regulated, including noncoding RNAs (ncRNAs) and post-translational modifications (PTMs). Finally, we discuss its role in diseases, such as cancer, fibrosis, and inflammatory bowel disease (IBD).

Asporin Promotes TGF-ß-induced Lung Myofibroblast Differentiation by Facilitating Rab11-Dependent Recycling of TßRI.

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive fibrotic lung disease with high mortality and morbidity. ASPN (asporin), a member of the small leucine-rich proteoglycan family, plays crucial roles in tissue injury and regeneration. However, the precise pathophysiological role of ASPN and its molecular mechanisms in IPF remain unknown. We sought to investigate the role of ASPN during the development of pulmonary fibrosis and the therapeutic potential of targeting ASPN-related signaling pathways. In our study, three microarray datasets were downloaded from the Gene Expression Omnibus database, and differentially expressed genes were screened out by bioinformatic analysis. Hub genes were selected from the protein-protein interaction network. ASPN was examined in lung tissues from pulmonary fibrosis mouse models, and the role of ASPN in transforming growth factor (TGF)-ß/Smad signaling was determined by transfection with ASPN shRNA vectors in vitro. Biotinylation assays were conducted to measure plasma membrane TFG-ß receptor I (TßRI) and TßRI recycling after ASPN knockdown. The results showed ASPN expression was increased in the lungs of pulmonary fibrosis mouse models, and ASPN was primarily localized in α-SMA+ myofibroblasts. In vitro experiments proved that ASPN knockdown inhibited TGF-ß/Smad signaling and myofibroblast differentiation by regulating the stability of TßRI. Further molecular mechanisms revealed that ASPN knockdown inhibited TGF-ß/Smad signaling by suppressing recycling of TßRI to the cell surface in a Rab11-dependent manner and facilitated lysosome-mediated degradation of TßRI. In conclusion, our findings provide important evidence for the use of ASPN as a novel pharmacological target for treating pulmonary fibrosis.

Targeting Nestin+ hepatic stellate cells ameliorates liver fibrosis by facilitating TßRI degradation.

BACKGROUND & AIMS: Liver fibrosis is a wound healing response that arises from various aetiologies. The intermediate filament protein Nestin has been reported to participate in maintaining tissue homeostasis during wound healing responses. However, little is known about the role Nestin plays in liver fibrosis. This study investigated the function and precise regulatory network of Nestin during liver fibrosis. METHODS: Nestin expression was assessed via immunostaining and quantitative real-time PCR (qPCR) in fibrotic/cirrhotic samples. The induction of Nestin expression by transforming growth factor beta (TGFß)-Smad2/3 signalling was investigated through luciferase reporter assays. The functional role of Nestin in hepatic stellate cells (HSCs) was investigated by examining the pathway activity of profibrogenic TGFß-Smad2/3 signalling and degradation of TGFß receptor I (TßRI) after interfering with Nestin. The in vivo effects of knocking down Nestin were examined with an adeno-associated virus vector (serotype 6, AAV6) carrying short-hairpin RNA targeting Nestin in fibrotic mouse models. RESULTS: Nestin was mainly expressed in activated HSCs and increased with the progression of liver fibrosis. The profibrogenic pathway TGFß-Smad2/3 induced Nestin expression directly. Knocking down Nestin promoted caveolin 1-mediated TßRI degradation, resulting in TGFß-Smad2/3 pathway impairment and reduced fibrosis marker expression in HSCs. In AAV6-treated murine fibrotic models, knocking down Nestin resulted in decreased levels of inflammatory infiltration, hepatocellular damage, and a reduced degree of fibrosis. CONCLUSION: The expression of Nestin in HSCs was induced by TGFß and positively correlated with the degree of liver fibrosis. Knockdown of Nestin decreased activation of the TGFß pathway and alleviated liver fibrosis both in vitro and in vivo. Our data demonstrate a novel role of Nestin in controlling HSC activation in liver fibrosis. LAY SUMMARY: Liver fibrosis has various aetiologies but represents a common process in chronic liver diseases that is associated with high morbidity and mortality. Herein, we demonstrate that the intermediate filament protein Nestin plays an essential profibrogenic role in liver fibrosis by forming a positive feedback loop with the TGFß-Smad2/3 pathway, providing a potential therapeutic target for the treatment of liver fibrosis.

Binding of coronin 1B to TßRI negatively regulates the TGFß1 signaling pathway.

Coronin 1B is an actin-binding protein that regulates several actin-dependent cellular processes including migration and endocytosis. However, the role of coronin 1B in the tumor growth factor (TGF)ß signaling pathway is largely unknown. Here, we investigated whether coronin 1B affects the TGFß signaling cascade and found that coronin 1B negatively regulates the TGFß signaling pathway. Immunoprecipitation and glutathione-S-transferase-pulldown assays revealed that coronin 1B directly associated with TGFß receptor I (TßRI). Overexpression of coronin 1B inhibited the TGFß1-induced interaction between TßRI and Smad2/3 in plasmid-transfected HEK293T cells. Coronin 1B was basally bound to TßRI in vascular smooth muscle cells (VSMCs), but TGFß1 stimulation did not affect their association, suggesting constitutive binding between coronin 1B and TßRI. Overexpression of coronin 1B suppressed TGFß1-induced activation of a Smad-binding element-luciferase reporter construct and a plasminogen activator inhibitor (PAI)-1 promoter-luciferase reporter construct in HEK293T cells. By contrast, depletion of coronin 1B by siRNA transfection increased TGFß1-induced Smad2/3 phosphorylation and PAI-1 expression in VSMCs. These results suggest that coronin 1B regulates the TGFß1 signaling cascade by constitutively interacting with TßRI and inhibiting the binding of Smad2/3 to TßRI in response to TGFß1 stimulation.

Lentivirus-mediated over-expression of let-7b microRNA suppresses hepatic fibrosis in the mouse infected with Schistosoma japonicum.

Transforming growth factor-ß (TGF-ß) signaling pathway is documented to participate in liver fibrosis via multifactorial mechanisms. microRNA Let-7b (Let-7b) has been proved to alleviate cell fibrosis through regulating TGF-ß receptor I (TßRI), but whether it is involved in Schistosomiasis liver fibrosis (SLF) has not been determined. In the present, SLF mice model was used to investigate Let-7b's function and mechanism in SLF. We found that hepatic let-7b expression was continuously declined in SLF, accompanied by the induction of TGF-ß pathway molecules (TGF-ß1, TßRI), profibrogenic mediators (α-SMA, colla I), and Th1/Th2 cells response factors (IFN-γ, IL-4). When recombinant Lentivirus of let-7b (Lenti-let-7b) was transfected into S. japonicum-infected mice, the mice hepatic fibrosis was distinctly ameliorated, and TGF-ß1, TßRI, α-SMA, and colla I expressions were remarkly decreased, mice serum IL-4 and IFN-γ levels were reduced. Similarly, over-expression of let-7b down-regulated the expression of TßRI in THP-1 cells transfected with let-7b mimics, while TßRI was up-regulated after treated with let-7b inhibitor. These findings suggested that let-7b is a negative regulator to SLF through downregulating TßRI, and inhibits Th1 and Th2 type cell immune response. This provides a novel potential therapeutic strategy for SFL prevention.

Transforming growth factor-ß1 acts via TßR-I on microglia to protect against MPP(+)-induced dopaminergic neuronal loss.

Neuroinflammation is associated with pathogenesis of Parkinson's disease (PD), a neurodegenerative disorder characterized by a progressive loss of dopaminergic (DAergic) neurons within the substantia nigra. Transforming growth factor (TGF)-ß1 exerts anti-inflammatory and neuroprotective properties. However, it is unclear if microglia are required for TGF-ß1 neuroprotection in PD. Here we used both shRNA and pharmacologic inhibition to determine the role of microglial TGF-ß receptor (TßR)-I and its downstream signaling pathways in 1-methyl-4-phenylpyridinium (MPP(+))-induced DAergic neuronal toxicity. As expected, MPP(+) reduced the number of tyrosine hydroxylase (TH)-immunoreactive cells in ventral mesencephalic cell cultures. We found that MPP(+) activated microglia as determined by an upregulation in expression of CD11b and inducible nitric oxide synthase (iNOS), an increase in expression and secretion of tumor necrosis factor (TNF)-α and interleukin (IL)-1ß, and a decrease in expression and secretion of the neurotrophic factor, insulin-like growth factor (IGF)-1. Pretreatment with TGF-ß1 significantly inhibited all these changes caused by MPP(+). Expression of microglial TßR-I was upregulated by TGF-ß1. Silencing of the TßR-I gene in microglia abolished both the neuroprotective and anti-inflammatory properties of TGF-ß1. TGF-ß1 increased microglial p38 MAPK and Akt phosphorylation, both of which were blocked by the p38 inhibitor SB203580 and the PI3K inhibitor LY294002, respectively. Pretreatment of microglia with either SB203580 or LY294002 impaired the ability of TGF-ß1 to inhibit MPP(+)-induced DAergic neuronal loss and microglial activation. These findings establish that TGF-ß1 activates TßR-I and its downstream p38 MAPK and PI3K-Akt signaling pathways in microglia to protect against DAergic neuronal loss that characterizes in PD.

MicroRNA-101 suppresses liver fibrosis by targeting the TGFß signalling pathway.

Transforming growth factor-ß (TGFß) is crucial for liver fibrogenesis and the blunting of TGFß signalling in hepatic stellate cells (HSCs) or hepatocytes can effectively inhibit liver fibrosis. microRNAs (miRNAs) have emerged as key regulators in modulating TGFß signalling and liver fibrogenesis. However, the regulation of TGFß receptor I (TßRI) production by miRNA remains poorly understood. Here we demonstrate that the miR-101 family members act as suppressors of TGFß signalling by targeting TßRI and its transcriptional activator Kruppel-like factor 6 (KLF6) during liver fibrogenesis. Using a mouse model of carbon tetrachloride (CCl4 )-induced liver fibrosis, we conducted a time-course experiment and observed significant down-regulation of miR-101 in the fibrotic liver as well as in the activated HSCs and injured hepatocytes in the process of liver fibrosis. Meanwhile, up-regulation of TßRI/KLF6 was observed in the fibrotic liver. Subsequent investigations validated that TßRI and KLF6 were direct targets of miR-101. Lentivirus-mediated ectopic expression of miR-101 in liver greatly reduced CCl4 -induced liver fibrosis, whereas intravenous administration of antisense miR-101 oligonucleotides aggravated hepatic fibrogenesis. Mechanistic studies revealed that miR-101 inhibited profibrogenic TGFß signalling by suppressing TßRI expression in both HSCs and hepatocytes. Additionally, miR-101 promoted the reversal of activated HSCs to a quiescent state, as indicated by suppression of proliferation and migration, loss of activation markers and gain of quiescent HSC-specific markers. In hepatocytes, miR-101 attenuated profibrogenic TGFß signalling and suppressed the consequent up-regulation of profibrogenic cytokines, as well as TGFß-induced hepatocyte apoptosis and the inhibition of cell proliferation. The pleiotropic roles of miR-101 in hepatic fibrogenesis suggest that it could be a potential therapeutic target for liver fibrosis.

Kindlin-2 Regulates the Oncogenic Activities of Integrins and TGF-ß In Triple Negative Breast Cancer Progression and Metastasis.

Background: Kindlin-2, an adaptor protein, is dysregulated in various human cancers, including triple negative breast cancer (TNBC), where it drives tumor progression and metastasis by influencing several cancer hallmarks. One well-established role of Kindlin-2 involves the regulation of integrin signaling, achieved by directly binding to the cytoplasmic tail of the integrin ß subunit. In this study, we present novel insights into Kindlin-2's involvement in stabilizing the ß1-Integrin:TGF-ß type 1 receptor (TßRI) complexes, acting as a physical bridge that links ß1-Integrin to TßRI. The loss of Kindlin-2 results in the degradation of this protein complex, leading to the inhibition of downstream oncogenic pathways. Methods: Our methodology encompassed a diverse range of in vitro assays, including CRISPR/Cas9 gene editing, cell migration, 3D tumorsphere formation and invasion, solid binding, co-immunoprecipitation, cell adhesion and spreading assays, as well as western blot and flow cytometry analyses, utilizing MDA-MB-231 and 4T1 TNBC cell lines. Additionally, preclinical in vivo mouse models of TNBC tumor progression and metastasis were employed to substantiate our findings. Results: The investigation revealed that the direct interaction between Kindlin-2 and ß1-Integrin is mediated through the C-terminal F3 domain of Kindlin-2, while the interaction between Kindlin-2 and TßRI is facilitated through the F2 domain of Kindlin-2. Disruption of this bridge, achieved via CRISPR/Cas9-mediated knockout of Kindlin-2, led to the degradation of ß1-Integrin and TßRI, resulting in the inhibition of oncogenic pathways downstream of both proteins, subsequently hindering tumor growth and metastasis. Treatment of Kindlin-2-deficient cells with the proteasome inhibitor MG-132 restored the expression of both ß1-Integrin and TßRI. Furthermore, the rescue of Kindlin-2 expression reinstated their oncogenic activities both in vitro and in vivo. Conclusions: This study identifies a novel function of Kindlin-2 in stabilizing the ß1-Integrin:TßR1 complexes and regulating their downstream oncogenic signaling. The translational implications of these findings are substantial, potentially unveiling new therapeutically targeted pathways crucial for the treatment of TNBC tumors.

Investigating rutin as a potential transforming growth factor-ß type I receptor antagonist for the inhibition of bleomycin-induced lung fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a chronic lung condition characterized by the abnormal regulation of extracellular matrix (ECM) and epithelial-mesenchymal transition (EMT). In this study, we investigated the potential of rutin, a natural flavonoid, in attenuating transforming growth factor-ß (TGF-ß)-induced ECM regulation and EMT through the inhibition of the TGF-ß type I receptor (TßRI)-mediated suppressor of mothers against decapentaplegic (SMAD) signaling pathway. We found that non-toxic concentrations of rutin attenuated TGF-ß-induced ECM-related genes, including fibronectin, elastin, collagen 1 type 1, and TGF-ß, as well as myoblast differentiation from MRC-5 lung fibroblast cells accompanied by the downregulation of α-smooth muscle actin. Rutin also inhibited TGF-ß-induced EMT processes, such as wound healing, migration, and invasion by regulating EMT-related gene expression. Additionally, rutin attenuated bleomycin-induced lung fibrosis in mice, thus providing a potential therapeutic option for IPF. The molecular docking analyses in this study predict that rutin occludes the active site of TßRI and inhibits SMAD-mediated fibrotic signaling pathways in lung fibrosis. These findings highlight the potential of rutin as a promising anti-fibrotic prodrug for lung fibrosis and other TGF-ß-induced fibrotic and cancer-related diseases; however, further studies are required to validate its safety and effectiveness in other experimental models.

The ubiquitin-ligase TRAF6 and TGFß type I receptor form a complex with Aurora kinase B contributing to mitotic progression and cytokinesis in cancer cells.

BACKGROUND: Transforming growth factor ß (TGFß) is overexpressed in several advanced cancer types and promotes tumor progression. We have reported that the intracellular domain (ICD) of TGFß receptor (TßR) I is cleaved by proteolytic enzymes in cancer cells, and then translocated to the nucleus in a manner dependent on the endosomal adaptor proteins APPL1/2, driving an invasiveness program. How cancer cells evade TGFß-induced growth inhibition is unclear. METHODS: We performed microarray analysis to search for genes regulated by APPL1/2 proteins in castration-resistant prostate cancer (CRPC) cells. We investigated the role of TßRI and TRAF6 in mitosis in cancer cell lines cultured in 10% FBS in the absence of exogenous TGFß. The molecular mechanism of the ubiquitination of AURKB by TRAF6 in mitosis and the formation of AURKB-TßRI complex in cancer cell lines and tissue microarrays was also studied. FINDINGS: During mitosis and cytokinesis, AURKB-TßRI complexes formed in midbodies in CRPC and KELLY neuroblastoma cells. TRAF6 induced polyubiquitination of AURKB on K85 and K87, protruding on the surface of AURKB to facilitate its activation. AURKB-TßRI complexes in patient's tumor tissue sections correlated with the malignancy of prostate cancer. INTERPRETATION: The AURKB-TßRI complex may become a prognostic biomarker for patients with risk of developing aggressive PC. FUNDING: Swedish Medical Research Council (2019-01598, ML; 2015-02757 and 2020-01291, CHH), the Swedish Cancer Society (20 0964, ML), a regional agreement between Umeå University and Region Västerbotten (ALF; RV-939377, -967041, -970057, ML). The European Research Council (787472, CHH). KAW 2019.0345, and the Kempe Foundation SMK-1866; ML. National Microscopy Infrastructure (NMI VR-RFI 2016-00968).

The orphan GPR50 receptor interacting with TßRI induces G1/S-phase cell cycle arrest via Smad3-p27/p21 in BRL-3A cells.

The liver has the powerful capacity to regenerate after injury or resection. In one of our previous studies, GPR50 was observed to be significantly upregulated at 6 h, following a partial hepatectomy (PH) in rat liver regeneration (LR) via gene expression profile. However, little research has been done on the regulation and mechanism of GPR50 in the liver. Herein, we observed that the overexpression of GPR50 inhibited the proliferation of BRL-3A cells. To further explore the molecular mechanisms of GPR50 in the regulation of BRL-3A cell proliferation, interaction between GPR50 and transforming growth factor-beta I (TßRI) and iTRAQTM differential proteomic analysis were elucidated, which suggested that GPR50 may interact with TßRI to activate the TGF-ß signaling pathway and arrest BRL-3A cell cycle G1/S transition. Subsequently, the potential mechanism underlying the role of GPR50 in hepatocyte growth was also explored through the addition of a signaling pathway inhibitor. These data suggested that interaction between the orphan GPR50 receptor and TßRI induced the G1/S-phase cell cycle arrest of BRL-3A cells via the Smad3-p27/p21 pathway.

Jagged-1 is induced by mTOR inhibitors in renal cancer cells through an Akt/ALK5/Smad4-dependent mechanism.

The mammalian target of rapamycin (mTOR) plays an important role in the aggressiveness and therapeutic resistance of many cancers. Targeting mTOR continues to be under clinical investigation for cancer therapy. Despite the notable clinical success of mTOR inhibitors in extending the overall survival of patients with certain malignancies including metastatic renal cell carcinomas (RCCs), the overall impact of mTOR inhibitors on cancers has been generally disappointing and attributed to various compensatory responses. Here we provide the first report that expression of the Notch ligand Jagged-1 (JAG1), which is associated with aggressiveness of RCCs, is induced by several inhibitors of mTOR (rapamycin (Rap), BEZ235, KU-0063794) in human clear cell RCC (ccRCC) cells. Using both molecular and chemical inhibitors of PI3K, Akt, and TGF-ß signaling, we provide evidence that the induction of JAG1 expression by mTOR inhibitors in ccRCC cells depends on the activation of Akt and occurs through an ALK5 kinase/Smad4-dependent mechanism. Furthermore, we show that mTOR inhibitors activate Notch1 and induce the expression of drivers of epithelial-mesenchymal transition, notably Hic-5 and Slug. Silencing JAG1 with selective shRNAs blocked the ability of KU-0063794 and Rap to induce Hic-5 in ccRCC cells. Moreover, Rap enhanced TGF-ß-induced expression of Hic-5 and Slug, both of which were repressed in JAG1-silenced ccRCC cells. Silencing JAG1 selectively decreased the motility of ccRCC cells treated with Rap or TGF-ß1. Moreover, inhibition of Notch signaling with γ-secretase inhibitors enhanced or permitted mTOR inhibitors to suppress the motility of ccRCC cells. We suggest targeting JAG1 may enhance therapeutic responses to mTOR inhibitors in ccRCCs.

CUEDC1 inhibits epithelial-mesenchymal transition via the TßRI/Smad signaling pathway and suppresses tumor progression in non-small cell lung cancer.

Lung cancer remains the most lethal cancer worldwide because of its high metastasis potential. Epithelial-mesenchymal transition (EMT) is known as the first step of the metastasis cascade, but the potential regulatory mechanisms of EMT have not been clearly established. In this study, we first found that low CUEDC1 expression correlated with lymph node metastasis in non-small cell lung cancer (NSCLC) patients using immunohistochemistry (IHC). CUEDC1 knockdown promoted the metastasis of NSCLC cells and EMT process and activated TßRI/Smad signaling pathway. Overexpression of CUEDC1 decreased the metastatic potential of lung cancer cells and inhibited the EMT process and inactivated TßRI/Smad signaling pathway. Immunoprecipitation (IP) assays showed that Smurf2 is a novel CUEDC1-interacting protein. Furthermore, CUEDC1 could regulate Smurf2 expression through the degradation of Smurf2. Overexpression of Smurf2 abolished CUEDC1 knockdown induced-EMT and the activation of TßRI/Smad signaling pathway, while siRNA Smurf2 reversed CUEDC1 overexpression-mediated regulation of EMT and TßRI/Smad signaling pathway. Additionally, CUEDC1 inhibited proliferation and promoted apoptosis of NSCLC cells. In vivo, CUEDC1-knockdown cells promoted metastasis and tumor growth compared with control cells. In conclusion, our findings indicate that the crucial role of CUEDC1 in NSCLC progression and provide support for its clinical investigation for therapeutic approaches.

Interaction of TGFß3 ligand with its receptors type II (TßRII) and type I (TßRI): A unique mechanism of protein-protein association.

The proper orchestration of transforming growth factor beta (TGFß) mediated signal transduction depends upon a delicate set of interactions between specific ligands and their receptors. Here we present an in-depth profiling of the binding mechanism of TGFß3 ligand with its type II and type I receptors (TßRII and TßRI) using isothermal titration calorimetry (ITC). Studies were carried out in acidic pH as it has great physiological relevance for TGFß3 activity. Our findings reveal an unusual positive enthalpy (∆H) compensated by a large favourable entropy (∆S) during TGFß3-TßRII interaction. In addition to the hydrophobic effect, we propose that a distinct conformational switch from "closed" to "open" form as experienced by TGFß3 on binding to TßRII is contributing significantly to the increase in overall entropy of the system. Binding studies of TGFß3 and TßRII were carried out at different pH values and salt concentrations to gain further insight into the thermodynamics of the interaction. Furthermore, the importance of hydrophobic interactions on the binding affinity of TßRII with TGFß3 was confirmed by two TßRII variants (interfacial). Finally, a distinct shift from entropy to enthalpy dominated interaction was observed upon recruitment of TßRI to the binary complex forming the ternary complex.

SIRT7 regulates the TGF-ß1-induced proliferation and migration of mouse airway smooth muscle cells by modulating the expression of TGF-ß receptor I.

Accumulating evidence shows that sirtuin 7 (SIRT7), a key mediator of many cellular activities, plays an important role in the pathogenesis of various diseases; however, little is known about the role of SIRT7 in asthma, which is characterized by airway remodeling. This study investigated the potential role of SIRT7 in regulating the proliferation and migration of airway smooth muscle (ASM) cells, which are critical events during airway remodeling in asthmatic conditions. The results demonstrated that SIRT7 expression was significantly upregulated in ASM cells treated with transforming growth factor-beta 1 (TGF-ß1). Knockdown of SIRT7 inhibited the proliferation, promoted the apoptosis, and suppressed the migration of TGF-ß1-treated ASM cells, while overexpression of SIRT7 had the opposite effect. Moreover, knockdown of SIRT7 inhibited protein expression of the TGF-ß receptor I (TßRI), whilst overexpression of SIRT7 promoted the expression of TßRI. Importantly, knockdown of TßRI partially reversed the stimulatory effect of SIRT7 overexpression on the TGF-ß1-induced proliferation and migration of ASM cells. Taken together, these results demonstrate that SIRT7 is involved in regulating TGF-ß1-induced ASM cell proliferation and migration by regulating the expression of TßRI, thus indicating an important role of SIRT7 during airway remodeling in asthma.

Sterol Regulatory Element Binding Protein (SREBP)-1 is a novel regulator of the Transforming Growth Factor (TGF)-ß receptor I (TßRI) through exosomal secretion.

Accumulation of matrix in the glomerulus is a classic hallmark of diabetic nephropathy. The profibrotic cytokine transforming growth factor beta 1 (TGF-ß1) plays a central role in the development of glomerular sclerosis. Recent studies have demonstrated that the transcription factor sterol regulatory element binding protein (SREBP)-1 is an important regulator of glomerular sclerosis through both induction of TGF-ß1 as well as facilitation of its signaling. Here we have identified that SREBP-1 is also a novel regulator of TGF-ß receptor I (TßRI) expression in kidney mesangial cells. Inhibition of SREBP activation with fatostatin or downregulation of SREBP-1 using siRNA inhibited the expression of the receptor. SREBP-1 did not regulate TßRI transcription, nor did it induce its proteasomal or lysosomal degradation or proteolytic cleavage. Disruption of lipid rafts with cyclodextrin, however, prevented TßRI downregulation. This was not dependent on caveolae since SREBP-1 inhibition could induce TßRI downregulation in caveolin-1 knockout mesangial cells. SREBP-1 associated with TßRI, and SREBP-1 inhibition led to the secretion of TßRI in exosomes. Thus, we have identified a novel role for SREBP-1 as a cell surface retention factor for TßRI in mesangial cells, preventing its secretion in exosomes. Inhibition of SREBP-1 in vivo may thus provide a novel therapeutic strategy for diabetic nephropathy which targets multiple aspects of TGFß signaling and matrix upregulation.

RETRACTED: Inhibition of the TGF-ß1/Smad signaling pathway protects against cartilage injury and osteoarthritis in a rat model.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Editor-in-Chief as there are concerns about the reliability of the results included in the article. The journal was initially contacted by several authors requesting retraction of this paper because these authors claimed that it was published without their knowledge and consent, although several authors have opposing opinions. Fig. 6A. contains similar parts of Fig 2C from another paper authored by the same group of authors published in Journal of Cellular Biochemistry, Volume 119, Issue 2, (2018) 1827-1840, https://doi.org/10.1002/jcb.26344, the journal requested the authors to provide the raw data. However, the authors were not able to fulfill this request.

Posttranslational Modifications of TGF-ß Receptors.

TGF-ß is a prototype of the TGF-ß cytokine superfamily and exerts multiple regulatory effects on cell activities. It signals through two types of membrane-bound serine/threonine kinase receptors. Upon TGF-ß binding, the type II receptor TßRII recruits the type I receptor TßRI and form a functional heterocomplex. TßRII trans-phosphorylates the GS region of TßRI, thus triggering its kinase activity. Activated TßRI proceeds to activate downstream Smad2/3. Signal intensity and duration through the availability, activity and destiny of TGF-ß receptors are finely controlled by multiple posttranslational modifications such as phosphorylation, ubiquitination, and neddylation. This chapter introduces methods for examination of these modifications of TGF-ß receptors.

BIX02189 inhibits TGF-ß1-induced lung cancer cell metastasis by directly targeting TGF-ß type I receptor.

Transforming growth factor-ß1 (TGF-ß1) promotes tumor metastasis by inducing an epithelial-to-mesenchymal transition (EMT) in cancer cells. In this study, we investigated the effects of BIX02189 and XMD8-92, pharmacologic inhibitors of the MEK5 [mitogen-activated protein kinase/extracellular-signal-regulated kinase (ERK)5] signaling pathway, on the EMT and migration of cancer cells induced by TGF-ß1. In human A549 lung cancer cells, TGF-ß1-induced EMT, cell motility, and expression of matrix metalloproteinase-2 were completely inhibited by BIX02189, but not by XMD8-92 or small interference RNAs specific to MEK5 and ERK5. Interestingly, BIX02189 strongly blocked the activation of TGF-ß1 signaling components, and this inhibitory effect was not reproduced by MEK5 inhibition. Molecular docking simulation and kinase assays revealed that BIX02189 binds directly to the ATP-binding site of the TGF-ß receptor type I (TßRI) and suppresses its kinase activity. Finally, the anti-metastatic effect of BIX02189 was validated in a TßRI-derived A549 xenograft mouse model. Collectively, these findings newly characterize BIX02189 as a potent inhibitor of TßRI that can block the tumor metastatic activity of TGF-ß1.