Structural determinants of Smad function in TGF-β signaling

Contextual determinants of TGFβ action in development, immunity and cancer

Few cell signals match the impact of the transforming growth factor-β (TGFβ) family in metazoan biology. TGFβ cytokines regulate cell fate decisions during development, tissue homeostasis and regeneration, and are major players in tumorigenesis, fibrotic disorders, immune malfunctions and various congenital diseases. The effects of the TGFβ family are mediated by a combinatorial set of ligands and receptors and by a common set of receptor-activated mothers against decapentaplegic homologue (SMAD) transcription factors, yet the effects can differ dramatically depending on the cell type and the conditions. Recent progress has illuminated a model of TGFβ action in which SMADs bind genome-wide in partnership with lineage-determining transcription factors and additionally integrate inputs from other pathways and the chromatin to trigger specific cellular responses. These new insights clarify the operating logic of the TGFβ pathway in physiology and disease.

Adenovirus‑mediated knockdown of activin A receptor type 2A attenuates immune‑induced hepatic fibrosis in mice and inhibits interleukin‑17‑induced activation of primary hepatic stellate cells

Fibrosis induces a progressive loss of liver function, thus leading to organ failure. Activins are secreted proteins that belong to the transforming growth factor (TGF)-β superfamily, which initiate signaling by binding to their two type II receptors: Activin A receptor type 2A (ACVR2A) and activin A receptor type 2B. Previous studies that have explored the mechanisms underlying immune-induced hepatic fibrosis have mainly focused on TGF-β signaling, not activin signaling. To investigate the role of the activin pathway in this disease, adenovirus particles containing short hairpin (sh)RNA targeting ACVR2A mRNA (Ad-ACVR2A shRNA) were administered to mice, which were chronically treated with concanavalin A (Con A). The pathological changes in the liver were evaluated with hematoxylin/eosin staining, Masson trichrome staining and immunohistochemical assay. The results detected an increase in serum activin A and liver ACVR2A in Con A-treated animals. Conversely, liver function was partially restored and fibrotic injury was attenuated when activin signaling was blocked. In addition, the activation of hepatic stellate cells (HSCs) in response to Con A was suppressed by Ad-ACVR2A shRNA, as evidenced by decreased α-smooth muscle actin, and type I and IV collagen expression. Furthermore, primary mouse HSCs (mHSCs) were activated when exposed to interleukin (IL)-17A or IL-17F, which are two major cytokines produced by cluster of differentiation 4⁺ T helper 17 cells. The levels of activin A, type I and IV collagen were determined with ELISA kits and the expression of fibrotic molecules was determined with western blot analysis. Conversely, blocking activin/ACVR2A impaired the potency of HSCs to produce collagens in response to IL-17s. In addition, C terminus phosphorylation of Smad2 on Ser465 and Ser467, induced by either Con A in the liver or by IL-17s in mHSCs, was partly inhibited when activin A/ACVR2A signaling was suppressed. Collectively, the present study demonstrated an involvement of activated activin A/ACVR2A/Smad2 signaling in immune-induced hepatic fibrosis.

Thrombospondin immune regulation and the kidney

Most therapeutic attempts to prevent the progression of kidney diseases have been based on interventions to inhibit the production of transforming growth factor-β (TGF-β). Thrombospondins (TSPs) play an important role in activating TGF-β. In the healthy kidney, two TSPs are expressed, TSP1 and TSP2, which exert contrasting effects. While TSP1 is a major activator of TGF-β in renal cells and exerts pro-inflammatory effects both in vitro and in vivo, TSP2 lacks the ability for TGF-β activation but regulates matrix remodeling and inflammation in experimental kidney disease. The effects of TSPs in the kidney have been mostly investigated by using the murine model of unilateral ureteral obstruction. In this model, TSP1 expression is increased along with the development of interstitial fibrosis and TGF-β. Relief of the obstruction gradually improves renal function and decreases the expression in TSP1 and TGF-β1. Several inhibitors of TSP1 prevented progressive interstitial fibrosis in murine models of ureteral obstruction, suggesting that control of latent TGF-β activation by inhibiting TSP1 might represent a novel potential target for preventing renal interstitial fibrosis. However, further studies are needed to assess whether TSP1-mediated TGF-β activation can be safely used in humans. In fact, TSPs normally act to suppress tumors in vivo. Moreover, TGF-β can exert a pivotal function in the immune system, as it may induce the production of regulatory T cells and suppress B cell responses. Knowledge of the molecular mechanisms involved in TGF-β regulation may help in finding effective treatments of tissue fibrosis, cancer and autoimmune disease.

The Pathway Coexpression Network: Revealing pathway relationships

A goal of genomics is to understand the relationships between biological processes. Pathways contribute to functional interplay within biological processes through complex but poorly understood interactions. However, limited functional references for global pathway relationships exist. Pathways from databases such as KEGG and Reactome provide discrete annotations of biological processes. Their relationships are currently either inferred from gene set enrichment within specific experiments, or by simple overlap, linking pathway annotations that have genes in common. Here, we provide a unifying interpretation of functional interaction between pathways by systematically quantifying coexpression between 1,330 canonical pathways from the Molecular Signatures Database (MSigDB) to establish the Pathway Coexpression Network (PCxN). We estimated the correlation between canonical pathways valid in a broad context using a curated collection of 3,207 microarrays from 72 normal human tissues. PCxN accounts for shared genes between annotations to estimate significant correlations between pathways with related functions rather than with similar annotations. We demonstrate that PCxN provides novel insight into mechanisms of complex diseases using an Alzheimer’s Disease (AD) case study. PCxN retrieved pathways significantly correlated with an expert curated AD gene list. These pathways have known associations with AD and were significantly enriched for genes independently associated with AD. As a further step, we show how PCxN complements the results of gene set enrichment methods by revealing relationships between enriched pathways, and by identifying additional highly correlated pathways. PCxN revealed that correlated pathways from an AD expression profiling study include functional clusters involved in cell adhesion and oxidative stress. PCxN provides expanded connections to pathways from the extracellular matrix. PCxN provides a powerful new framework for interrogation of global pathway relationships. Comprehensive exploration of PCxN can be performed at http://pcxn.org/.

Genes do not function alone, but interact within pathways to carry out specific biological processes. Pathways, in turn, interact at a higher level to affect major cellular activities such as motility, growth and development. We present a pathway coexpression network (PCxN) that systematically maps and quantifies these high-level interactions and establishes a unifying reference for pathway relationships. The method uses 3,207 human microarrays from 72 normal human tissues and 1,330 of the most well established pathway annotations to describe global relationships between pathways. PCxN accounts for shared genes to estimate correlations between pathways with related functions rather than with redundant pathway definitions. PCxN can be used to discover and explore pathways correlated with a pathway of interest. We applied PCxN to identify key processes related to Alzheimer’s disease (AD), interpreting a mixed genetic association and experimental derived set of disease genes in the context of gene co-expression. We expand the known relationships between pathways identified by gene set enrichment analysis in brain tissues affected with AD. PCxN provides a high-level overview of pathway relationships. PCxN is available as a webtool at http://pcxn.org/, and as a Bioconductor package at http://bioconductor.org/packages/pcxn/.

Upregulation of lncRNA CASC2 Suppresses Cell Proliferation and Metastasis of Breast Cancer via Inactivation of the TGF-β Signaling Pathway

Breast cancer is one of the major malignancies with a mounting mortality rate in the world. Long noncoding RNA (lncRNA) cancer susceptibility candidate 2 (CASC2) has been identified to regulate the initiation and progression of multiple tumorous diseases according to previous studies. However, its biological role has been rarely reported in breast cancer. In the present study, lncRNA CASC2 was found to be significantly downregulated in breast cancer tissues and cell lines using real-time quantitative PCR. Furthermore, gain-of-function assays demonstrated that overexpression of lncRNA CASC2 significantly repressed breast cancer cell proliferation and metastasis. Moreover, CASC2 induced cell cycle arrest and much more early apoptosis of breast cancer. Additionally, based on the above research, we illustrated that inactivation of the TGF-β signaling pathway was involved in the function of lncRNA CASC2. Collectively, lncRNA CASC2 was a key factor in the tumorigenesis and malignancy of breast cancer, suggesting it may possibly be a potential therapy target for the treatment of breast cancer.

Face morphogenesis is promoted by Pbx-dependent EMT via regulation of Snail1 during frontonasal prominence fusion

Human cleft lip with or without cleft palate (CL/P) is a common craniofacial abnormality caused by impaired fusion of the facial prominences. We have previously reported that, in the mouse embryo, epithelial apoptosis mediates fusion at the seam where the prominences coalesce. Here, we show that apoptosis alone is not sufficient to remove the epithelial layers. We observed morphological changes in the seam epithelia, intermingling of cells of epithelial descent into the mesenchyme and molecular signatures of epithelial-mesenchymal transition (EMT). Utilizing mouse lines with cephalic epithelium-specific Pbx loss exhibiting CL/P, we demonstrate that these cellular behaviors are Pbx dependent, as is the transcriptional regulation of the EMT driver Snail1. Furthermore, in the embryo, the majority of epithelial cells expressing high levels of Snail1 do not undergo apoptosis. Pbx1 loss- and gain-of-function in a tractable epithelial culture system revealed that Pbx1 is both necessary and sufficient for EMT induction. This study establishes that Pbx-dependent EMT programs mediate murine upper lip/primary palate morphogenesis and fusion via regulation of Snail1. Of note, the EMT signatures observed in the embryo are mirrored in the epithelial culture system.

Expression of TGF-beta receptor 1 and Smads in the tissues of primary spontaneous pneumothorax

BACKGROUND

Primary spontaneous pneumothorax (PSP) is a common disease which is often caused by the rupture of bullae in the lungs. The underlying pathogenesis of PSP remains unclear. Some molecules may be involved in the development of PSP potentially. The aim of this study was to investigate the expression of TGF-beta receptor 1 (TβR1), Smad2, Smad3 and Smad4 in the resected bullae of patients with PSP.

METHODS

From May 2015 to May 2016, 34 patients with PSP underwent video-assisted thoracoscopic surgery (VATS) bullectomy. Immunohistochemistry was performed to identify the expression of TβR1, Smad2, Smad3 and Smad4 in the resected pulmonary bullae tissues. The levels of these cytokines were calculated by immunoreactivity scoring system (IRS). Ten patients without pneumothorax associated disease were selected as the control group.

RESULTS

The analysis showed that the expression levels of TβR1, Smad2 and Smad4 were significantly higher in bullae tissues of patients with PSP than that in normal lung tissues (P=0.012, 0.031, 0.000 respectively). There was no significant difference between the expression level of Smad3 in bullae tissue of PSP patients and that in normal lung tissues of the control group (P=0.140). However, the absolute quantity of Smad3 expression in PSP bullae tissues was (4.2529±1.7193), scored by the IRS, which is higher than that in the control lung tissues (3.2600±2.2132). Also, the expression of TβR1, Smad2, Smad3 and Smad4 were not showed correlation with the clinical characteristics of PSP patients, such as age, sex, body mass index (BMI), recurrence and side of pneumothorax.

CONCLUSIONS

TβR1, Smad2 and Smad4 highly expressed in bullae tissues of PSP patients. Our findings suggested that TβR1, Smad2 and Smad4 may be related to the development of PSP bullae.

LncRNA AWPPH inhibits SMAD4 via EZH2 to regulate bladder cancer progression

This study aimed to investigate the effect and underlying mechanism of lncRNA AWPPH in bladder cancer (BC). A total of 20 Ta-T1 stage BC tissues, 20 T2-T4 stage BC tissues, and 20 normal bladder tissues, as well as human bladder epithelial cell line SV-HUC-1, human BC cell lines RT4, and T24 were obtained to detect the levels of AWPPH, enhancer of zeste homolog 2 (EZH2) and SMAD4 using RT-qPCR or Western blotting. RT4 cells were transfected with pc-AWPPH, pc-EZH2, or pc-control and T24 cells were transfected with si-AWPPH, si-EZH2, si-control, or pc-AWPPH + pc-SMAD4, respectively. Then, cell proliferation, apoptosis, autophagy, and migration, were detected using MTT assay, colony formation assay, Annexin V-FITC/PI method, Western blotting, and Transwell analysis, respectively. The relationship of AWPPH and EZH2 or SMAD4 was evaluated by RNA immunoprecipitation (RIP) assay or Chromatin immunoprecipitation (ChIP) assay. Compared with normal bladder tissues or cells, the levels of AWPPH and EZH2 were overexpressed, while SMAD4 was down-regulated in BC tissues or cells (all P < 0.01). Cell viability, colony number, and migration were significantly increased, while cell apoptosis ratio was reduced in cells with pc-AWPPH compared with cells with pc-control (all P < 0.05), meanwhile, these effects were reversed by the treatment of pc-SMAD4. Then, RIP assay revealed that AWPPH could bind to EZH2 and ChIP assay showed SMAD4 was regulated by EZH2. LncRNA AWPPH can promote cell proliferation, autophagy, and migration, as well as inhibit cell apoptosis in BC by inhibiting SMAD4 via EZH2.

GP73 promotes invasion and metastasis of bladder cancer by regulating the epithelial-mesenchymal transition through the TGF-β1/Smad2 signalling pathway

This study investigated the effects of Golgi membrane protein 73 (GP73) on the epithelial-mesenchymal transition (EMT) and on bladder cancer cell invasion and metastasis through the TGF-β1/Smad2 signalling pathway. Paired bladder cancer and adjacent tissue samples (102) and normal bladder tissue samples (106) were obtained. Bladder cancer cell lines (T24, 5637, RT4, 253J and J82) were selected and assigned to blank, negative control (NC), TGF-β, thrombospondin-1 (TSP-1), TGF-β1+ TSP-1, GP73-siRNA-1, GP73-siRNA-2, GP73-siRNA-1+ TSP-1, GP73-siRNA-1+ pcDNA-GP73, WT1-siRNA and WT1-siRNA + GP73-siRNA-1 groups. Expressions of GP73, TGF-β1, Smad2, p-Smad2, E-cadherin and vimentin were detected using RT-qPCR and Western blotting. Cell proliferation, migration and invasion were determined using MTT assay, scratch testing and Transwell assay, respectively. Compared with the blank and NC groups, levels of GP73, TGF-β1, Smad2, p-Smad2, N-cadherin and vimentin decreased, and levels of WT1 and E-cadherin increased in the GP73-siRNA-1 and GP73-siRNA-2 groups, while the opposite results were observed in the WT1 siRNA, TGF-β, TSP-1 and TGF-β + TSP-1 groups. Cell proliferation, migration and invasion notably decreased in the GP73-siRNA-1 and GP73-siRNA-2 groups in comparison with the blank and NC groups, while in the WT1 siRNA, TGF-β, TSP-1 and TGF-β + TSP-1 groups, cell migration, invasion and proliferation showed the reduction after the EMT. These results suggest that GP73 promotes bladder cancer invasion and metastasis by inducing the EMT through down-regulating WT1 levels and activating the TGF-β1/Smad2 signalling pathway.

Cyclin-Dependent Kinase 8: A New Hope in Targeted Cancer Therapy?

Cyclin-dependent kinase 8 (CDK8) plays a vital role in regulating transcription either through its association with the Mediator complex or by phosphorylating transcription factors. Myriads of genetic and biochemical studies have established CDK8 as a key oncogenic driver in many cancers. Specifically, CDK8-mediated activation of oncogenic Wnt-β-catenin signaling, transcription of estrogen-inducible genes, and suppression of super enhancer-associated genes contributes to oncogenesis in colorectal, breast, and hematological malignancies, respectively. However, while most research supports the role of CDK8 as an oncogene, other work has raised the possibility of its contrary function. The diverse biological functions of CDK8 and its seemingly context-specific roles in different types of cancers have spurred a great amount of interest and perhaps an even greater amount of controversy in the development of CDK8 inhibitors as potential cancer therapeutic agents. Herein, we review the latest landscape of CDK8 biology and its involvement in carcinogenesis. We dissect current efforts in discovering CDK8 inhibitors and attempt to provide an outlook at the future of CDK8-targeted cancer therapies.

Crosstalk between TGF-β signaling and epigenome

The transforming growth factor beta (TGF-β) family of ligands plays major roles in embryonic development, tissue homeostasis, adult immunity, and wound repair. Dysregulation of TGF-β signaling pathway leads to severe diseases. Its key components have been revealed over the past two decades. This family of cytokines acts by activating receptor activated SMAD (R-SMAD) transcription factors, which in turn modulate the expression of specific sets of target genes. Cells of a multicellular organism have the same genetic information, yet they show structural and functional differences owing to differential expression of their genes. Studies have demonstrated that epigenetic regulation, an integral part of the TGF-β signaling, enables cells to sense and respond to TGF-β signaling in a cell context-dependent manner. R-SMAD, as the central transcription factor of TGF-β signaling, can recruit various epigenetic regulators to shape the transcriptome. In this review, we focus on epigenetic regulatory mechanisms in the TGF-β signaling during mammalian development and diseases and discuss the central role of the interaction between R-SMAD and various epigenetic regulators in this epigenetic regulation. The crosstalk between TGF-β signaling and the epigenome could serve as a versatile fine-tuning mechanism for transcriptional regulation during embryonic development and progression of diseases, particularly cancer.

Repurposed drug screen identifies cardiac glycosides as inhibitors of TGF-β-induced cancer-associated fibroblast differentiation

The tumor microenvironment, primarily composed of myofibroblasts, directly influences the progression of solid tumors. Through secretion of growth factors, extracellular matrix deposition, and contractile mechanotransduction, myofibroblasts, or cancer-associated fibroblasts (CAFs), support angiogenesis and cancer cell invasion and metastasis. The differentiation of fibroblasts to CAFs is primarily induced by TGF-β from cancer cells. To discover agents capable of blocking CAF differentiation, we developed a high content immunofluorescence-based assay to screen repurposed chemical libraries utilizing fibronectin expression as an initial CAF marker. Screening of the Prestwick chemical library and NIH Clinical Collection repurposed drug library, totaling over 1700 compounds, identified cardiac glycosides as particularly potent CAF blocking agents. Cardiac glycosides are traditionally used to regulate intracellular calcium by inhibiting the Na+/K+ ATPase to control cardiac contractility. Herein, we report that multiple cardiac glycoside compounds, including digoxin, are able to inhibit TGF-β-induced fibronectin expression at low nanomolar concentrations without undesirable cell toxicity. We found this inhibition to hold true for multiple fibroblast cell lines. Using real-time qPCR, we determined that digoxin prevented induction of multiple CAF markers. Furthermore, we report that digoxin is able to prevent TGF-β-induced fibroblast contraction of extracellular matrix, a major phenotypic consequence of CAF differentiation. Assessing the mechanism of inhibition, we found digoxin reduced SMAD promoter activity downstream of TGF-β, and we provide data that the effect is through inhibition of its known target, the Na+/K+ ATPase. These findings support a critical role for calcium signaling during CAF differentiation and highlight a novel, repurposable modality for cancer therapy.

The SMAD3 transcription factor binds complex RNA structures with high affinity

Several members of the SMAD family of transcription factors have been reported to bind RNA in addition to their canonical double-stranded DNA (dsDNA) ligand. RNA binding by SMAD has the potential to affect numerous cellular functions that involve RNA. However, the affinity and specificity of this RNA binding activity has not been well characterized, which limits the ability to validate and extrapolate functional implications of this activity. Here we perform quantitative binding experiments in vitro to determine the ligand requirements for RNA binding by SMAD3. We find that SMAD3 binds poorly to single- and double-stranded RNA, regardless of sequence. However, SMAD3 binds RNA with large internal loops or bulges with high apparent affinity. This apparent affinity matches that for its canonical dsDNA ligand, suggesting a biological role for RNA binding by SMAD3.

Structural basis for genome wide recognition of 5-bp GC motifs by SMAD transcription factors

Smad transcription factors activated by TGF-β or by BMP receptors form trimeric complexes with Smad4 to target specific genes for cell fate regulation. The CAGAC motif has been considered as the main binding element for Smad2/3/4, whereas Smad1/5/8 have been thought to preferentially bind GC-rich elements. However, chromatin immunoprecipitation analysis in embryonic stem cells showed extensive binding of Smad2/3/4 to GC-rich cis-regulatory elements. Here, we present the structural basis for specific binding of Smad3 and Smad4 to GC-rich motifs in the goosecoid promoter, a nodal-regulated differentiation gene. The structures revealed a 5-bp consensus sequence GGC(GC)|(CG) as the binding site for both TGF-β and BMP-activated Smads and for Smad4. These 5GC motifs are highly represented as clusters in Smad-bound regions genome-wide. Our results provide a basis for understanding the functional adaptability of Smads in different cellular contexts, and their dependence on lineage-determining transcription factors to target specific genes in TGF-β and BMP pathways.

Smad transcription factors are part of the TGF-β signal transduction pathways and are recruited to the genome by cell lineage-defining factors. Here, the authors identify specific Smad binding GC-rich motifs and provide structural information showing Smad3 and Smad4 bound to these motifs.

TGF-β Family Signaling in Tumor Suppression and Cancer Progression

Transforming growth factor-β (TGF-β) induces a pleiotropic pathway that is modulated by the cellular context and its integration with other signaling pathways. In cancer, the pleiotropic reaction to TGF-β leads to a diverse and varied set of gene responses that range from cytostatic and apoptotic tumor-suppressive ones in early stage tumors, to proliferative, invasive, angiogenic, and oncogenic ones in advanced cancer. Here, we review the knowledge accumulated about the molecular mechanisms involved in the dual response to TGF-β in cancer, and how tumor cells evolve to evade the tumor-suppressive responses of this signaling pathway and then hijack the signal, converting it into an oncogenic factor. Only through the detailed study of this complexity can the suitability of the TGF-β pathway as a therapeutic target against cancer be evaluated.

Sirt1 interaction with active Smad2 modulates transforming growth factor-β regulated transcription

Background

The simplicity of Transforming Growth Factor ß (TGFβ) signaling pathway, linear and non-amplified, hardly sustains its variety of responses. This is often justified by the complex regulation showed by Smad proteins, TGFβ signaling intracellular transducers, object of post-translational modifications that modulate TGFβ-dependent transcription. Protein acetylation is emerging as a compelling mechanism affecting the activities of significant transcription factors, including p53, FOXO or NF-kB. Smad proteins might be controlled by this mechanism, implying that accessory factors capable of altering Smads-transcriptional complexes acetylation status and hence regulate TGFβ responses remain to be identified. Understanding this interaction may help in the assessment of TGFβ signaling outcomes, extending from healthy physiology to pathological conditions and cancer.

Methods

A two-hybrid chimera interacting system allowed to identify Sirt1, a NAD+ dependent type III histone deacetylase, as a novel Smad2 interactor. Several well stablished cellular models were applied to characterize this interaction by means of co-immunoprecipitation of tagged proteins and immuno-fluorescence staining. The occurrence of the interaction at Smad2 driven transcriptomic complexes was studied by means of DNA-pull-down and chromatin immunoprecipitation (ChIP), while its effects were assessed by protein over-expression and siRNA applied into a TGFβ-dependent reporter gene assay.

Results

The interaction was confirmed and observed to be enhanced upon Smad2 acetylation, a known feature of active and nuclear Smad2. However, Sirt1 did not play a major role in Smad2 deacetylation. Anti-Sirt1 ChIP showed increased recovery of promoter regions corresponding to Smad2-driven genes after TGFβ-stimulation, while its occurrence at Smad2-dependent transcriptomic complexes on DNA was found to effectively modulate gene expression.

Conclusions

Sirt1 presence on Smad2-driven TGFβ-dependent regulatory elements was detected and found to increase after TGFβ treatment. Moreover, Sirt1 overexpression resulted in a decrease of the activity of a Smad2-driven TGFβ-dependent reporter gene, while Sirt1 interference increased its activity. This would confirm the relevance of the discovered Sirt1-Smad2 interaction for the regulation of TGFβ-dependent gene transcription.

Electronic supplementary material

The online version of this article (10.1186/s12964-017-0205-y) contains supplementary material, which is available to authorized users.

Integrin Beta 3 Regulates Cellular Senescence by Activating the TGF-β Pathway

Cellular senescence is an important in vivo mechanism that prevents the propagation of damaged cells. However, the precise mechanisms regulating senescence are not well characterized. Here, we find that ITGB3 (integrin beta 3 or β3) is regulated by the Polycomb protein CBX7. β3 expression accelerates the onset of senescence in human primary fibroblasts by activating the transforming growth factor β (TGF-β) pathway in a cell-autonomous and non-cell-autonomous manner. β3 levels are dynamically increased during oncogene-induced senescence (OIS) through CBX7 Polycomb regulation, and downregulation of β3 levels overrides OIS and therapy-induced senescence (TIS), independently of its ligand-binding activity. Moreover, cilengitide, an αvβ3 antagonist, has the ability to block the senescence-associated secretory phenotype (SASP) without affecting proliferation. Finally, we show an increase in β3 levels in a subset of tissues during aging. Altogether, our data show that integrin β3 subunit is a marker and regulator of senescence.

Cystine knot growth factors and their functionally versatile proregions

The cystine knot disulfide pattern has been found to be widespread in nature, since it has been detected in proteins from plants, marine snails, spiders and mammals. Cystine knot proteins are secreted proteins. Their functions range from defense mechanisms as toxins, e.g. ion channel or enzyme inhibitors, to hormones, blood factors and growth factors. Cystine knot proteins can be divided into two superordinate groups. (i) The cystine knot peptides, also referred to - with other non-cystine knot proteins - as knottins, with linear and cyclic polypeptide chains. (ii) The cystine knot growth factor family, which is in the focus of this article. The disulfide ring structure of the cystine knot peptides is made up by the half-cystines 1-4 and 2-5, and the threading disulfide bond is formed by the half-cystines, 3-6. In the growth factor group, the disulfides of half-cystines 1 and 4 pass the ring structure formed by the half-cystines 2-5 and 3-6. In this review, special emphasis will be devoted to the growth factor cystine knot proteins and their proregions. The latter have shifted into the focus of scientific interest as their important biological roles are just to be unravelled.

TGF-β1/Smad3 Signaling Pathway Mediates T-2 Toxin-Induced Decrease of Type II Collagen in Cultured Rat Chondrocytes

T-2 toxin can cause damage to the articular cartilage, but the molecular mechanism remains unclear. By employing the culture of rat chondrocytes, we investigated the effect of the TGF-β1/Smad3 signaling pathway on the damage to chondrocytes induced by T-2 toxin. It was found that T-2 toxin could reduce cell viability and increased the number of apoptotic cells when compared with the control group. After the addition of the T-2 toxin, the production of type II collagen was reduced at mRNA and protein levels, while the levels of TGF-β1, Smad3, ALK5, and MMP13 were upregulated. The production of the P-Smad3 protein was also increased. Inhibitors of TGF-β1 and Smad3 were able to reverse the effect of the T-2 toxin on the protein level of above-mentioned signaling molecules. The T-2 toxin could promote the level of MMP13 via the stimulation of TGF-β1 signaling in chondrocytes, resulting in the downregulation of type II collagen and chondrocyte damage. Smad3 may be involved in the degradation of type II collagen, but the Smad3 has no connection with the regulation of MMP13 level. This study provides a new clue to elucidate the mechanism of T-2 toxin-induced chondrocyte damage.

Getting Old through the Blood: Circulating Molecules in Aging and Senescence of Cardiovascular Regenerative Cells

Global aging is a hallmark of our century. The natural multifactorial process resulting in aging involves structural and functional changes, affecting molecules, cells, and tissues. As the western population is getting older, we are witnessing an increase in the burden of cardiovascular events, some of which are known to be directly linked to cellular senescence and dysfunction. In this review, we will focus on the description of a few circulating molecules, which have been correlated to life span, aging, and cardiovascular homeostasis. We will review the current literature concerning the circulating levels and related signaling pathways of selected proteins (insulin-like growth factor 1, growth and differentiation factor-11, and PAI-1) and microRNAs of interest (miR-34a, miR-146a, miR-21), whose bloodstream levels have been associated to aging in different organisms. In particular, we will also discuss their potential role in the biology and senescence of cardiovascular regenerative cell types, such as endothelial progenitor cells, mesenchymal stromal cells, and cardiac progenitor cells.

Interleukin 1 β-induced SMAD2/3 linker modifications are TAK1 dependent and delay TGFβ signaling in primary human mesenchymal stem cells

BACKGROUND

Chondrogenic differentiation of mesenchymal stem cells (MSC) requires transforming growth factor beta (TGFβ) signaling. TGFβ binds to the type I receptor activin-like kinase (ALK)5 and results in C-terminal SMAD2/3 phosphorylation (pSMAD2/3C). In turn pSMAD2/3C translocates to the nucleus and regulates target gene expression. Inflammatory mediators are known to exert an inhibitory effect on MSC differentiation. In this study we investigated the effect of interleukin 1 β (IL1β) on SMAD2/3 signaling dynamics and post-translational modifications.

RESULTS

Co-stimulation of MSC with TGFβ and IL1β did not affect peak pSMAD2C levels at 1h post-stimulation. Surprisingly, SMAD3 transcriptional activity, as determined by the CAGA₁₂-luciferase reporter construct, was enhanced by co-stimulation of TGFβ and IL1β compared to TGFβ alone. Furthermore, IL1β stimulation induced CAGA₁₂-luciferase activity in a SMAD dependent way. As SMAD function can be modulated independent of canonical TGFβ signaling through the SMAD linker domain, we studied SMAD2 linker phosphorylation at specific threonine and serine residues. SMAD2 linker threonine and serine modifications were observed within 1h following TGFβ, IL1β or TGFβ and IL1β stimulation. Upon co-stimulation linker modified SMAD2 accumulated in the cytoplasm and SMAD2/3 target gene transcription (ID1, JUNB) at 2-4h was inhibited. A detailed time course analysis of IL1β-induced SMAD2 linker modifications revealed a distinct temperospatial pattern compared to TGFβ. Co-stimulation with both factors resulted in a similar kinetic profile as TGFβ alone. Nevertheless, IL1β did subtly alter TGFβ-induced pSMAD2C levels between 8 and 24h post-stimulation, which was reflected by TGFβ target gene expression (PAI1, JUNB). Direct evidence for the importance of SMAD3 linker modifications for the effect of IL1β on TGFβ signaling was obtained by over-expression of SMAD3 or a SMAD3 linker phospho-mutant. Finally, an inhibitor screening was performed to identify kinases involved in SMAD2/3 linker modifications. We identified TAK1 kinase activity as crucial for IL1β-induced SMAD2 linker modifications and CAGA₁₂-luciferase activity.

CONCLUSIONS

TGFβ and IL1β signaling interact at the SMAD2/3 level in human primary MSC. Down-stream TGFβ target genes were repressed by IL1β independent of C-terminal SMAD2 phosphorylation. We demonstrate that SMAD2/3 linker modifications are required for this interplay and identified TAK1 as a crucial mediator of IL1β-induced TGFβ signal modulation.

MDM2 promotes epithelial-mesenchymal transition and metastasis of ovarian cancer SKOV3 cells

Background:

Metastasis accounts for the most lethal reason for the death of ovarian cancer patients, but remains largely untreated. Epithelial–mesenchymal transition (EMT) is critical for the conversion of early-stage ovarian tumours into metastatic malignancies. Thus the exploration of the signalling pathways promoting EMT would open potential opportunities for the treatment of metastatic ovarian cancer. Herein, the putative role of MDM2 in regulating EMT and metastasis of ovarian cancer SKOV3 cells was investigated.

Methods:

The regulatory effects by MDM2 on cell motility was emulated by wound-healing and transwell assays. The effects on EMT transition and Smad pathway were studied by depicting the expression levels of epithelial marker E-cadherin as well as key components of Smad pathway. To evaluate the clinical relevance of our findings, the correlation of MDM2 expression levels with the stages of 104 ovarian cancer patients was investigated by immunohistochemistry assay.

Results:

We demonstrate that MDM2 functions as a key factor to drive EMT and motility of ovarian SKOV3 cells, by facilitating the activation of TGF-β-Smad pathway, which results in the increased transcription of snail/slug and the subsequent loss of E-cadherin levels. Such induction of EMT is sustained in either E3 ligase-depleted MDM2 or E3 ligase inhibitor HLI-373-treated cells, while being impaired by the N-terminal deletion of MDM2, which is also reflected by the inhibitory effects against EMT by Nutlin-3a, the N-terminal targeting agent. The expression levels of MDM2 is highly correlated with the stages of the ovarian cancer patients, and the higher expression of MDM2 together with TGFB are closely correlated with poor prognosis and predict a high risk of ovarian cancer patients.

Conclusions:

This study suggests that MDM2 activates Smad pathway to promote EMT in ovarian cancer metastasis, and targeting the N-terminal of MDM2 can reprogram EMT and impede the mobility of cancer cells.

Molecular characterization of two distinct Smads gene and their roles in the response to bacteria change and wound healing from Hyriopsis cumingii

The proteins of Smad family are critical components of the TGF-β superfamily signal pathway. In this paper, we cloned two intracellular mediators of TGF-β signaling, Smad3 and Smad5, from the pearl mussel Hyriopsis cumingii. The full length cDNA of HcSmad3 and HcSmad5 were 2052 bp and 1908 bp and encoded two polypeptides of 418 and 461amino acid residues, respectively. The deduced amino acid of HcSmad3 and HcSmad5 possessed two putative conserved domains, MH1 and MH2, a conserved phosphorylation motif SSXS at the carboxyl-terminal. The two Smad genes were detected muscle, mantle, hepatopancreas and gill, but with a very low level in heamocytes. The transcripts of Smad3 and Smad5 were up-regulated in hemocytes and hepatopancreas after A. hydrophila and PGN stimulation. However, the expression of Smad3 and Smad5 were only up-regulated in hepatopancreas after A. hydrophila stimulation. The transcripts of Smad3 and Smad5 had a slight change in hepatopancreas after PGN stimulation. The transcripts of HcSmad3 showed very little increase and HcSmad5 mRNA significantly up-regulated after wounding.

SOX4: Joining the Master Regulators of Epithelial-to-Mesenchymal Transition?

The epithelial-to-mesenchymal transition (EMT) is an important developmental program exploited by cancer cells to gain mesenchymal features. Transcription factors globally regulating processes during EMT are often referred as 'master regulators' of EMT, and include members of the Snail and ZEB transcription factor families. The SRY-related HMG box (SOX) 4 transcription factor can promote tumorigenesis by endowing cells with migratory and invasive properties, stemness, and resistance to apoptosis, thereby regulating key aspects of the EMT program. We propose here that SOX4 should also be considered as a master regulator of EMT, and we review the molecular mechanisms underlying its function.

An FGFR inhibitor converts the tumor promoting effect of TGF-β by the induction of fibroblast-associated genes of hepatoma cells

Tumors consistently mimic wound-generating chronic inflammation; however, why they do not heal like wounds with fibrotic scars remains unknown. The components of the tumor microenvironment, such as transforming growth factor β (TGF-β) and fibroblast growth factors (FGFs), may account for this phenomenon. Tumor formation involves continuous activation of the FGF pathway, whereas the repair of tissue injury is a self-limiting process accompanied with controlled activation of the FGF pathway. In the tumor microenvironment TGF-β increases the secretion of FGFs, further promoting the malignant biological properties of tumors. However, during wound healing, sufficient TGF-β together with moderate FGFs lead to matrix deposition and the formation of fibrotic scars. In the present study, TGF-β1 combined with AZD4547, an FGF receptor (FGFR) inhibitor, transformed hepatoma cells into less malignant fibroblast-like cells with respect to morphology, physiological properties, and gene expression profiles. In vivo experiments showed that TGF-β1 combined with AZD4547 not only inhibited tumor growth but also promoted tumor parenchyma fibrosis. Our results indicate that FGFR inhibitor treatment converts the effect of TGF-β on the hepatocellular carcinoma cells from tumor promotion into tumor inhibition by enhancing the induction effect of TGF-β on some fibroblast-associated genes. Converting human liver cancer cells into less malignant fibroblast-like cells and inducing tumor parenchyma cell fibrosis provides an alternative strategy for limiting tumor progression.

Absolute Ligand Discrimination by Dimeric Signaling Receptors

Many signaling pathways act through shared components, where different ligand molecules bind the same receptors or activate overlapping sets of response regulators downstream. Nevertheless, different ligands acting through cross-wired pathways often lead to different outcomes in terms of the target cell behavior and function. Although a number of mechanisms have been proposed, it still largely remains unclear how cells can reliably discriminate different molecular ligands under such circumstances. Here we show that signaling via ligand-induced receptor dimerization-a very common motif in cellular signaling-naturally incorporates a mechanism for the discrimination of ligands acting through the same receptor.

The expression profiling of serum miR-92a, miR-375, and miR-760 in colorectal cancer: An Egyptian study

Dysregulation in microRNA expression is a common feature in colorectal cancer. Due to the inconsistent results regarding serum miR-92a expression pattern and the insufficient studies on serum miR-375 and miR-760, we aimed in this study to investigate their expression profile and diagnostic and prognostic power in Egyptian colorectal cancer patients. The expression profile of miR-92a, miR-375, and miR-760 was determined in the sera of 64 colorectal cancer patients using quantitative real-time reverse transcription polymerase chain reaction in comparison to 27 healthy control subjects. The expression fold change of the studied microRNAs was correlated with patients' clinicopathological features. Receiver operating characteristic curve analysis was done to determine the role of these microRNAs in colorectal cancer diagnosis and follow-up according to the yielded area under the curve. The expression pattern of miR-92a was significantly upregulated (3.38 ± 2.52, p < 0.0001), while both of miR-375 and 760 were significantly downregulated (-1.250 ± 1.80, p< 0.0001; -1.710 ± 1.88, p < 0.0001, respectively) in colorectal cancer than the control. MiR-92a was positively correlated ( r = 0.671, p = 0.0001), while miR-375 and miR-760 were inversely correlated ( r = -0.414, p = 0.001; r = -0.644, p = 0.0001) with advanced colorectal cancer stages. Receiver operating characteristic curve analysis disclosed the highest diagnostic potential for miR-760 to discriminate colorectal cancer patients and early-stage colorectal cancer from the control (area under the curve = 0.922 and 0.875, respectively), while the highest prognostic potential for discrimination between colorectal cancer stages was for miR-92a. In conclusion, serum level of miR-92a, miR-375, and miR-760 may serve as biomarkers of colorectal cancer in Egyptian patients with high diagnostic power for miR-760 and high prognostic power for miR-92a.

The lysine methyltransferase SMYD2 methylates the kinase domain of type II receptor BMPR2 and stimulates bone morphogenetic protein signaling

Lysine methylation of chromosomal and nuclear proteins is a well-known mechanism of epigenetic regulation, but relatively little is known about the role of this protein modification in signal transduction. Using an RNAi-based functional screening of the SMYD family of lysine methyltransferases (KMTs), we identified SMYD2 as a KMT essential for robust bone morphogenic protein (BMP)- but not TGFβ-induced target gene expression in HaCaT keratinocyte cells. A role for SMYD2 in BMP-induced gene expression was confirmed by shRNA knockdown and CRISPR/Cas9-mediated knock-out of SMYD2 We further demonstrate that SMYD2 knockdown or knock-out impairs BMP-induced phosphorylation of the signal-transducing protein SMAD1/5 and SMAD1/5 nuclear localization and interaction with SMAD4. The SMYD2 KMT activity was required to facilitate BMP-mediated signal transduction, as treatment with the SMYD2 inhibitor AZ505 suppressed BMP2-induced SMAD1/5 phosphorylation. Furthermore, we present evidence that SMYD2 likely modulates the BMP response through its function in the cytosol. We show that, although SMYD2 interacted with multiple components in the BMP pathway, it specifically methylated the kinase domain of BMP type II receptor BMPR2. Taken together, our findings suggest that SMYD2 may promote BMP signaling by directly methylating BMPR2, which, in turn, stimulates BMPR2 kinase activity and activation of the BMP pathway.

The TGF-β Family in Caenorhabditis elegans

Transforming growth factor β (TGF-β) and related ligands have potent effects on an enormous diversity of biological functions in all animals examined. Because of the strong conservation of TGF-β family ligand functions and signaling mechanisms, studies from multiple animal systems have yielded complementary and synergistic insights. In the nematode Caenorhabditis elegans, early studies were instrumental in the elucidation of TGF-β family signaling mechanisms. Current studies in C. elegans continue to identify new functions for the TGF-β family in this organism as well as new conserved mechanisms of regulation.

Hepatocyte-specific expression of constitutively active Alk5 exacerbates thioacetamide-induced liver injury in mice

While Transforming growth factor-βs (Tgf-βs) have been known to play an important role in liver fibrosis through an activation of Hepatic Stellate Cells (HSC), their fibrotic role on hepatocytes in liver damage has not been addressed thoroughly. To shed more light on the hepatocyte-specific role of Tgf-β signaling during liver fibrosis, we generated transgenic mice expressing constitutively active Tgf-β type I receptor Alk5 under the control of albumin promoter. Uninjured mice with increased Tgf-β/Alk5 signaling in hepatocytes (caAlk5/Alb-Cre mice) did not show characteristics related to hepatocyte death, fibrosis and inflammation. When subjected to thioacetamide (TAA) treatment, caAlk5/Alb-Cre mice exhibited more severe liver injury, when compared to control littermates. After TAA administration for 12 weeks, an increase in pathological changes was evident in caAlk5/Alb-Cre livers, with higher number of infiltrating cells in the portal and periportal area. Immunohistochemistry for F4/80, myeloperoxidase and CD3 showed that there was an increased accumulation of macrophages, neutrophils and T-lymphocytes, respectively, in caAlk5/Alb-Cre livers. Coincidently, we observed an exacerbated liver damage as seen by increases in serum aminotransferase level and number of apoptotic hepatocytes in caAlk5/Alb-Cre mice. Sirius staining of collagen demonstrated that the fibrotic response was worsened in caAlk5/Alb-Cre mice. The enhanced fibrosis in mutant livers was associated with marked production of α-SMA-positive myofibroblast. Hepatic expression of genes indicative of HSC activation was greater in caAlk5/Alb-Cre mice. In conclusion, our data indicated that elevation of Tgf-β signaling via Alk5 in hepatocytes is not sufficient to induce liver pathology but plays an important role in amplifying TAA-induced liver damage.

Cell-penetrating peptides selectively targeting SMAD3 inhibit profibrotic TGF-β signaling

TGF-β is considered a master switch in the pathogenesis of organ fibrosis. The primary mediators of this activity are the SMAD proteins, particularly SMAD3. In the current study, we have developed a cell-penetrating peptide (CPP) conjugate of the HIV TAT protein that is fused to an aminoterminal sequence of sorting nexin 9 (SNX9), which was previously shown to bind phosphorylated SMAD3 (pSMAD3). We determined that specifically preventing the nuclear import of pSMAD3 using the TAT-SNX9 peptide inhibited profibrotic TGF-β activity in murine cells and human lung fibroblasts as well as in vivo with no demonstrable toxicity. TGF-β signaling mediated by pSMAD2, bone morphogenetic protein 4 (BMP4), EGF, or PDGF was unaffected by the TAT-SNX9 peptide. Furthermore, while the TAT-SNX9 peptide prevented TGF-β's profibrotic activity in vitro as well as in 2 murine treatment models of pulmonary fibrosis, a 3-amino acid point mutant that was unable to bind pSMAD3 proved ineffective. These findings indicate that specifically targeting pSMAD3 can ameliorate both the direct and indirect fibroproliferative actions of TGF-β.

Age, gender and UV-exposition related effects on gene expression in in vivo aged short term cultivated human dermal fibroblasts

Ageing, the progressive functional decline of virtually all tissues, affects numerous living organisms. Main phenotypic alterations of human skin during the ageing process include reduced skin thickness and elasticity which are related to extracellular matrix proteins. Dermal fibroblasts, the main source of extracellular fibrillar proteins, exhibit complex alterations during in vivo ageing and any of these are likely to be accompanied or caused by changes in gene expression. We investigated gene expression of short term cultivated in vivo aged human dermal fibroblasts using RNA-seq. Therefore, fibroblast samples derived from unaffected skin were obtained from 30 human donors. The donors were grouped by gender and age (Young: 19 to 25 years, Middle: 36 to 45 years, Old: 60 to 66 years). Two samples were taken from each donor, one from a sun-exposed and one from a sun-unexposed site. In our data, no consistently changed gene expression associated with donor age can be asserted. Instead, highly correlated expression of a small number of genes associated with transforming growth factor beta signalling was observed. Also, known gene expression alterations of in vivo aged dermal fibroblasts seem to be non-detectable in cultured fibroblasts.

The careg element reveals a common regulation of regeneration in the zebrafish myocardium and fin

The existence of common mechanisms regulating organ regeneration is an intriguing concept. Here we report on a regulatory element that is transiently activated during heart and fin regeneration in zebrafish. This element contains a ctgfa upstream sequence, called careg, which is induced by TGFβ/Activin-β signalling in the peri-injury zone of the myocardium and the fin mesenchyme. In addition, this reporter demarcates a primordial cardiac layer and intraray osteoblasts. Using genetic fate mapping, we show the regenerative competence of careg-expressing cells. The analysis of the heart reveals that the primordial cardiac layer is incompletely restored after cryoinjury, whereas trabecular and cortical cardiomyocytes contribute to myocardial regrowth. In regenerating fins, the activated mesenchyme of the stump gives rise to the blastema. Our findings provide evidence of a common regenerative programme in cardiomyocytes and mesenchyme that opens the possibility to further explore conserved mechanisms of the cellular plasticity in diverse vertebrate organs.

PPARγ Links BMP2 and TGFβ1 Pathways in Vascular Smooth Muscle Cells, Regulating Cell Proliferation and Glucose Metabolism

BMP2 and TGFβ1 are functional antagonists of pathological remodeling in the arteries, heart, and lung; however, the mechanisms in VSMCs, and their disturbance in pulmonary arterial hypertension (PAH), are unclear. We found a pro-proliferative TGFβ1-Stat3-FoxO1 axis in VSMCs, and PPARγ as inhibitory regulator of TGFβ1-Stat3-FoxO1 and TGFβ1-Smad3/4, by physically interacting with Stat3 and Smad3. TGFβ1 induces fibrosis-related genes and miR-130a/301b, suppressing PPARγ. Conversely, PPARγ inhibits TGFβ1-induced mitochondrial activation and VSMC proliferation, and regulates two glucose metabolism-related enzymes, platelet isoform of phosphofructokinase (PFKP, a PPARγ target, via miR-331-5p) and protein phosphatase 1 regulatory subunit 3G (PPP1R3G, a Smad3 target). PPARγ knockdown/deletion in VSMCs activates TGFβ1 signaling. The PPARγ agonist pioglitazone reverses PAH and inhibits the TGFβ1-Stat3-FoxO1 axis in TGFβ1-overexpressing mice. We identified PPARγ as a missing link between BMP2 and TGFβ1 pathways in VSMCs. PPARγ activation can be beneficial in TGFβ1-associated diseases, such as PAH, parenchymal lung diseases, and Marfan's syndrome.

The inhibition of microRNA-15a suppresses hepatitis B virus-associated liver cancer cell growth through the Smad/TGF-β pathway

In the present study, the role of microRNA‑15a (miR‑15a) was investigated in hepatitis B virus (HBV)‑associated liver cancer. The results revealed that the expression levels of miR-15a were increased in HBV-associated liver cancer tissues compared with the levels in normal tumor‑adjacent tissues. Moreover, Smad-7 protein expression in patients with HBV-associated liver cancer was higher than that in normal tumor-adjacent tissues. In addition, miR-15a expression and Smad-7 protein expression were increased in HepG2 hepatocellular carcinoma cells compared with that noted in L-02 normal hepatocytes. In HepG2 cells, miR-15a inhibition suppressed cell proliferation and increased Smad-7 protein expression. The inhibition of miR-15a was also demonstrated to decrease transforming growth factor (TGF)-β1 protein expression and Smad-2, p-Smad-2 and Smad-4 expression levels in HepG2 cells. Furthermore, FSP1 protein expression and caspase-3/-7 activities were enhanced by miR-15a inhibition in HepG2 cells compared with the control group. Treatment with recombinant TGF-β1 was demonstrated to activate Smad‑2/-4 and FSP1 protein expression and increase caspase-3/-7 activity in HepG2 cells. Collectively, these findings demonstrate that the miR-15a/Smad-7/TGF-β pathway is important in HBV-associated liver cancer.

Regulation of Ubiquitin Enzymes in the TGF-β Pathway

The transforming growth factor-β (TGF-β) pathway has a tumor suppressor role in normal and premalignant cells but promotes oncogenesis in advanced cancer cells. Components of the pathway are tightly controlled by ubiquitin modifying enzymes and aberrations in these enzymes are frequently observed to dysregulate the pathway causing diseases such as bone disorders, cancer and metastasis. These enzymes and their counterparts are increasingly being tested as druggable targets, and thus a deeper understanding of the enzymes is required. This review summarizes the roles of specific ubiquitin modifying enzymes in the TGF-β pathway and how they are regulated.

Pdgfrb is a direct regulatory target of TGFβ signaling in atrioventricular cushion mesenchymal cells

Cushion formation is the initial step for the development of valvuloseptal structures in mammalian hearts. TGFβ signaling plays critical roles in multiple steps of cushion morphogenesis. We used a newly developed conditional immortal atrioventricular cushion mesenchymal cell line, tsA58-AVM, to identify the TGFβ regulatory target genes through microarray analysis. Expression of ~1350 genes was significantly altered by TGFβ1 treatment. Subsequent bioinformatic analysis of TGFβ activated genes revealed that PDGF-BB signaling is the top hit as the potential upstream regulator. Among the 37 target molecules, 10 genes known to be involved in valve development and hemostasis were selected for quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis. Our results confirmed that they are all upregulated by TGFβ1 stimulation in tsA58-AVM cells and in primary atrioventricular cushion cells. We focused on examining regulation of Pdgfrb by TGFβ1, which encodes a tyrosine kinase receptor for PDGF-BB. We found that the ~150bp Pdgfrb promoter can respond to TGFβ stimulation and that this response relies on the two SP1 binding sites within the promoter. Co-immunoprecipitation analysis confirmed SP1 interacts with SMAD2 in a TGFβ-dependent fashion. Furthermore, SMAD2 is associated with the Pdgfrb promoter and this association is diminished by knocking down expression of Sp1. Our data therefore collectively suggest that upon TGFβ stimulation, SP1 recruits SMAD2 to the promoter of Pdgfrb to up-regulate its expression and thus Pdgfrb is a direct downstream target of the TGFβ/SMAD2 signaling.

Pin1, the Master Orchestrator of Bone Cell Differentiation

Pin1 is an enzyme that specifically recognizes the peptide bond between phosphorylated serine or threonine (pS/pT-P) and proline. This recognition causes a conformational change of its substrate, which further regulates downstream signaling. Pin1^-/- mice show developmental bone defects and reduced mineralization. Pin1 targets RUNX2 (Runt-Related Transcription Factor 2), SMAD1/5, and β-catenin in the FGF, BMP, and WNT pathways, respectively. Pin1 has multiple roles in the crosstalk between different anabolic bone signaling pathways. For example, it controls different aspects of osteoblastogenesis and increases the transcriptional activity of Runx2, both directly and indirectly. Pin1 also influences osteoclastogenesis at different stages by targeting PU.1 (Purine-rich nucleic acid binding protein 1), C-FOS, and DC-STAMP. The phenotype of Pin1^-/- mice has led to the recent identification of multiple roles of Pin1 in different molecular pathways in bone cells. These roles suggest that Pin1 can be utilized as an efficient drug target in congenital and acquired bone diseases. J. Cell. Physiol. 232: 2339-2347, 2017. © 2016 Wiley Periodicals, Inc.

Transforming Growth Factor-β1 Modulates the Expression of Syndecan-4 in Cultured Vascular Endothelial Cells in a Biphasic Manner

Proteoglycans are macromolecules that consist of a core protein and one or more glycosaminoglycan side chains. Previously, we reported that transforming growth factor‐β₁ (TGF‐β₁) regulates the synthesis of a large heparan sulfate proteoglycan, perlecan, and a small leucine‐rich dermatan sulfate proteoglycan, biglycan, in vascular endothelial cells depending on cell density. Recently, we found that TGF‐β₁ first upregulates and then downregulates the expression of syndecan‐4, a transmembrane heparan sulfate proteoglycan, via the TGF‐β receptor ALK5 in the cells. In order to identify the intracellular signal transduction pathway that mediates this modulation, bovine aortic endothelial cells were cultured and treated with TGF‐β₁. Involvement of the downstream signaling pathways of ALK5—the Smad and MAPK pathways—in syndecan‐4 expression was examined using specific siRNAs and inhibitors. The data indicate that the Smad3–p38 MAPK pathway mediates the early upregulation of syndecan‐4 by TGF‐β₁, whereas the late downregulation is mediated by the Smad2/3 pathway. Multiple modulations of proteoglycan synthesis may be involved in the regulation of vascular endothelial cell functions by TGF‐β₁. J. Cell. Biochem. 118: 2009–2017,2017. © 2016 The Authors. Journal of Cellular Biochemistry Published by Wiley Periodicals, Inc.

Pathological changes in basement membranes and dermal connective tissue of skin from patients with hereditary cystatin C amyloid angiopathy

Hereditary cystatin C amyloid angiopathy (HCCAA) is a genetic disease caused by a mutation in the cystatin C gene. Cystatin C is abundant in cerebrospinal fluid and the most prominent pathology in HCCAA is cerebral amyloid angiopathy due to mutant cystatin C amyloid deposition with associated cerebral hemorrhages, typically in young adult carriers. Analyses of post-mortem brain samples shows that pathological changes are limited to arteries and regions adjacent to arteries. The severity of pathological changes at post-mortem has precluded the elucidation of the evolution of histological changes. Mutant cystatin C deposition in carriers is systemic and has, for example, been described in the skin, suggesting similar pathological mechanisms both in the brain and outside of the central nervous system. The aim of this study was to use skin biopsies from asymptomatic and symptomatic carriers to study intermediate events in HCCAA pathogenesis. We found that cystatin C deposition in minimally affected samples was limited to the basement membrane (BM) between the dermis and epidermis. When the deposits were more advanced, they extended to other BM regions in the skin. Our results showed that the immunoreactivity of the BM protein COLIV was increased to a similar extent in all carrier biopsies and cystatin C deposits were in close association with COLIV. The density of fibroblasts in the upper dermis of carrier skin was increased, whereas the distribution of other cell types examined did not differ compared with control biopsies. COLIV and cystatin C immunoreactivity in carrier biopsies was closely associated with the fibroblasts. The results of this study, in conjunction with our previous results regarding pathological BM changes in leptomeningeal arteries of patients, suggest that BM changes are early and important events in HCCAA pathogenesis that could facilitate cystatin C deposition and aggregation.

The distribution and potential prognostic value of SMAD protein expression in chronic lymphocytic leukemia

The SMAD proteins are responsible for transducing signals from activated transforming growth factor-beta. This is the first study assessing the expression of SMAD-1/8, SMAD-2/3, SMAD-4, and SMAD-7 in chronic lymphocytic leukemia cells with regard to their clinical significance and potential prognostic value. Overexpression of SMAD-1/8 was observed in 160 chronic lymphocytic leukemia patients compared to 42 healthy volunteers (p = 0.023) and was associated with a more progressive course of the disease (p = 0.016). Moreover, the high expression of SMAD-1/8 correlated with other, well-established prognostic factors, including clinical stage (p = 0.010) and lymphocyte doubling time (p = 0.021). The expression of SMAD-4 was lower in chronic lymphocytic leukemia patients compared with the control group (p = 0.003). Importantly, lower SMAD-4 levels correlated with longer progression-free survival (p = 0.009), progressive course of the disease (p = 0.002), advanced clinical stage (p = 0.0004), elevated beta-2-microglobulin and lactate dehydrogenase levels (p < 0.05), shorter lymphocyte doubling time (p = 0.009), and CD38 antigen expression (p = 0.039). In addition, lower SMAD-4 expression correlated with lower apoptotic index (p = 0.0007) and lower expression of receptors for vascular endothelial growth factors VEGFR-1 and VEGFR-2. A significant association was found between the low expression of inhibitory protein SMAD-7 and both zeta-chain-associated protein kinase 70–negative cells (p = 0.04) and lower apoptotic index (p = 0.004). No differences were observed in SMAD-2/3 expression. In conclusion, our results demonstrate a significant correlation between greater SMAD-1/8 and lower SMAD-4 expression in chronic lymphocytic leukemia cells, as well as more progressive outcome and poor prognosis. These data provide supporting evidence that the expression of SMAD proteins plays an important role in disease development and may be considered as a novel, biologic prognostic factor in this disease.

Adipose tissue fibrosis in human cancer cachexia: the role of TGFβ pathway

Background

Cancer cachexia is a multifactorial syndrome that dramatically decreases survival. Loss of white adipose tissue (WAT) is one of the key characteristics of cachexia. WAT wasting is paralleled by microarchitectural remodeling in cachectic cancer patients. Fibrosis results from uncontrolled ECM synthesis, a process in which, transforming growth factor-beta (TGFβ) plays a pivotal role. So far, the mechanisms involved in adipose tissue (AT) re-arrangement, and the role of TGFβ in inducing AT remodeling in weight-losing cancer patients are poorly understood. This study examined the modulation of ECM components mediated by TGFβ pathway in fibrotic AT obtained from cachectic gastrointestinal cancer patients.

Methods

After signing the informed consent form, patients were enrolled into the following groups: cancer cachexia (CC, n = 21), weight-stable cancer (WSC, n = 17), and control (n = 21). The total amount of collagen and elastic fibers in the subcutaneous AT was assessed by histological analysis and by immunohistochemistry. TGFβ isoforms expression was analyzed by Multiplex assay and by immunohistochemistry. Alpha-smooth muscle actin (αSMA), fibroblast-specific protein (FSP1), Smad3 and 4 were quantified by qPCR and/or by immunohistochemistry. Interleukin (IL) 2, IL5, IL8, IL13 and IL17 content, cytokines known to be associated with fibrosis, was measured by Multiplex assay.

Results

There was an accumulation of collagen and elastic fibers in the AT of CC, as compared with WSC and controls. Collagens type I, III, VI, and fibronectin expression was enhanced in the tissue of CC, compared with both WSC and control. The pronounced expression of αSMA in the surrounding of adipocytes, and the increased mRNA content for FSP1 (20-fold) indicate the presence of activated myofibroblasts; particularly in CC. TGFβ1 and TGFβ3 levels were up-regulated by cachexia in AT, as well in the isolated adipocytes. Smad3 and Smad4 labeling was found to be more evident in the fibrotic areas of CC adipose tissue.

Conclusions

Cancer cachexia promotes the development of AT fibrosis, in association with altered TGFβ signaling, compromising AT organization and function.

Magnolol Attenuates Concanavalin A-induced Hepatic Fibrosis, Inhibits CD4+ T Helper 17 (Th17) Cell Differentiation and Suppresses Hepatic Stellate Cell Activation: Blockade of Smad3/Smad4 Signalling

Magnolol is a pharmacological biphenolic compound extracted from Chinese herb Magnolia officinalis, which displays anti-inflammatory and antioxidant effects. This study was aimed at exploring the potential effect of magnolol on immune-related liver fibrosis. Herein, BALB/c mice were injected with concanavalin A (ConA, 8 mg/kg/week) up to 6 weeks to establish hepatic fibrosis, and magnolol (10, 20, 30 mg/kg/day) was given to these mice orally throughout the whole experiment. We found that magnolol preserved liver function and attenuated liver fibrotic injury in vivo. In response to ConA stimulation, the CD4⁺ T cells preferred to polarizing towards CD4⁺ T helper 17 (Th17) cells in liver. Magnolol was observed to inhibit Th17 cell differentiation in ConA-treated liver in addition to suppressing interleukin (IL)-17A generation. Hepatic stellate cells were activated in fibrotic liver as demonstrated by increased alpha smooth muscle actin (α-SMA) and desmin. More transforming growth factor (TGF)-β1 and activin A were secreted into the serum. Magnolol suppressed this abnormal HSC activation. Furthermore, the phosphorylation of Smad3 in its linker area (Thr179, Ser 204/208/213) was inhibited by magnolol. In vitro, the recombinant IL-17A plus TGF-β1 or activin A induced activation of human LX2 HSCs and promoted their collagen production. Smad3/Smad4 signalling pathway was activated in LX2 cells exposed to the fibrotic stimuli, as illustrated by the up-regulated phospho-Smad3 and the enhanced interaction between Smad3 and Smad4. These alterations were suppressed by magnolol. Collectively, our study reveals a novel antifibrotic effect of magnolol on Th17 cell-mediated fibrosis.

The syndrome of central hypothyroidism and macroorchidism: IGSF1 controls TRHR and FSHB expression by differential modulation of pituitary TGFβ and Activin pathways

IGSF1 (Immunoglobulin Superfamily 1) gene defects cause central hypothyroidism and macroorchidism. However, the pathogenic mechanisms of the disease remain unclear. Based on a patient with a full deletion of IGSF1 clinically followed from neonate to adulthood, we investigated a common pituitary origin for hypothyroidism and macroorchidism, and the role of IGSF1 as regulator of pituitary hormone secretion. The patient showed congenital central hypothyroidism with reduced TSH biopotency, over-secretion of FSH at neonatal minipuberty and macroorchidism from 3 years of age. His markedly elevated inhibin B was unable to inhibit FSH secretion, indicating a status of pituitary inhibin B resistance. We show here that IGSF1 is expressed both in thyrotropes and gonadotropes of the pituitary and in Leydig and germ cells in the testes, but at very low levels in Sertoli cells. Furthermore, IGSF1 stimulates transcription of the thyrotropin-releasing hormone receptor (TRHR) by negative modulation of the TGFβ1-Smad signaling pathway, and enhances the synthesis and biopotency of TSH, the hormone secreted by thyrotropes. By contrast, IGSF1 strongly down-regulates the activin-Smad pathway, leading to reduced expression of FSHB, the hormone secreted by gonadotropes. In conclusion, two relevant molecular mechanisms linked to central hypothyroidism and macroorchidism in IGSF1 deficiency are identified, revealing IGSF1 as an important regulator of TGFβ/Activin pathways in the pituitary.

The role of transforming growth factor (TGF)-β in the infarcted myocardium

The adult mammalian heart has negligible regenerative capacity. Following myocardial infarction, sudden necrosis of cardiomyocytes triggers an intense inflammatory reaction that clears the wound from dead cells and matrix debris, while activating a reparative program. A growing body of evidence suggests that members of the transforming growth factor (TGF)-β family critically regulate the inflammatory and reparative response following infarction. Although all three TGF-β isoforms (TGF-β1, -β2 and -β3) are markedly upregulated in the infarcted myocardium, information on isoform-specific actions is limited. Experimental studies have suggested that TGF-β exerts a wide range of actions on cardiomyocytes, fibroblasts, immune cells, and vascular cells. The findings are often conflicting, reflecting the context-dependence of TGF-β-mediated effects; conclusions are often based exclusively on in vitro studies and on associative evidence. TGF-β has been reported to modulate cardiomyocyte survival responses, promote monocyte recruitment, inhibit macrophage pro-inflammatory gene expression, suppress adhesion molecule synthesis by endothelial cells, promote myofibroblast conversion and extracellular matrix synthesis, and mediate both angiogenic and angiostatic effects. This review manuscript discusses our understanding of the cell biological effects of TGF-β in myocardial infarction. We discuss the relative significance of downstream TGF-β-mediated Smad-dependent and -independent pathways, and the risks and challenges of therapeutic TGF-β targeting. Considering the high significance of TGF-β-mediated actions in vivo, study of cell-specific effects and dissection of downstream signaling pathways are needed in order to design safe and effective therapeutic approaches.