The activin signaling pathway promotes differentiation of dI3 interneurons in the spinal neural tube

The generation of the appropriate types and numbers of mature neurons during the development of the spinal cord requires the careful coordination of patterning, proliferation, and differentiation. In the dorsal neural tube, this coordination is achieved by the combined action of multiple ligands of both the Wnt and TGF-beta families, and their effectors, such as the bHLH proteins. TGF-beta signaling acting through the BMP receptors is necessary for the generation of several dorsal interneuron types. Other TGF-beta ligands expressed in the dorsal neural tube interact with the Activin receptors, which signal via a different set of SMAD proteins than BMPs. The effects of Activin signaling on the developing neural tube have not been described. Here we have activated the Activin signal transduction pathway in a cell-autonomous manner in the developing chick neural tube. We find that a constitutively active Activin receptor promotes differentiation throughout the neural tube. Although most differentiated cell populations are unaffected by Activin signaling, the number of dorsal interneuron 3 (dI3) cells is specifically increased. Our data suggest that Activin signaling may promote the formation of the dI3 precursor cells within a region circumscribed by BMP signaling and that this function is not dependent upon BMP signaling.     

Impaired growth of pancreatic exocrine cells in transgenic mice expressing human activin betaE subunit

Activins, TGF-beta superfamily members, have multiple functions in a variety of cells and tissues. Recently, additional activin beta subunit genes, betaC and betaE, have been identified. To explore the role of activin E, we created transgenic mice overexpressing human activin betaE subunit. There were pronounced differences in the pancreata of the transgenic animals as compared with their wild-type counterparts. Pancreatic weight, expressed relative to total body weight, was significantly reduced. Histologically, adipose replacement of acini in the exocrine pancreas was observed. There was a significant decrease in the number of PCNA-positive cells in the acinar cells, indicating reduced proliferation in the exocrine pancreas of the transgenic mice. However, quantitative pancreatic morphometry showed that the total number and mass of the islets of the transgenic mice were comparable with those of the nontransgenic control mice. Our findings suggest a role for activin E in regulating the proliferation of pancreatic exocrine cells.     

Oridonin suppresses gastric cancer SGC-7901 cell proliferation by targeting the TNF-alpha/androgen receptor/TGF-beta signalling pathway axis

Statistics provided by GLOBOCAN list gastric cancer as the sixth most common, with a mortality ranking of third highest for the year 2020. In China, a herb called Rabdosia rubescens (Hemsl.) H.Hara, has been used by local residents for the treatment of digestive tract cancer for hundreds of years. Oridonin, the main ingredient of the herb, has a curative effect for gastric cancer, but the mechanism has not been previously clarified. This study mainly aimed to investigate the role of TNF-alpha/Androgen receptor/TGF-beta signalling pathway axis in mediating the proliferation inhibition of oridonin on gastric cancer SGC-7901 cells. MTT assay, cell morphology observation assay and fluorescence assay were adopted to study the efficacy of oridonin on cell proliferation. The network pharmacology was used to predict the pathway axis regulated by oridonin. Western blot assay was adopted to verify the TNF-α/Androgen receptor/TGF-β signalling pathway axis regulation on gastric cancer by oridonin. The results showed Oridonin could inhibit the proliferation of gastric cancer cells, change cell morphology and cause cell nuclear fragmentation. A total of 11signaling pathways were annotated by the network pharmacology, among them, Tumour necrosis factor alpha (TNF-α) signalling pathway, androgen receptor (AR) signalling pathway and transforming growth factor (TGF-β) signalling pathway account for the largest proportion. Oridonin can regulate the protein expression of the three signalling pathways, which is consistent with the results predicted by network pharmacology. These findings indicated that oridonin can inhibit the proliferation of gastric cancer SGC-7901 cells by regulating the TNF-α /AR /TGF-β signalling pathway axis.     

Transforming growth factor-beta (TGF-beta) binding to the extracellular domain of the type II TGF-beta receptor: receptor capture on a biosensor surface using a new coiled-coil capture system demonstrates that avidity contributes significantly to high affinity binding

Mature TGF-beta isoforms, which are covalent dimers, signal by binding to three types of cell surface receptors, the type I, II and III TGF-beta receptors. A complex composed of the TGF-beta ligand and the type I and II receptors is required for signaling. The type II receptor is responsible for recruiting TGF-beta into the heteromeric ligand/type I receptor/type II receptor complex. The purpose of this study was to test for the extent that avidity contributes to receptor affinity. Using a surface plasmon resonance (SPR)-based biosensor (the BIACORE), we captured the extracellular domain of the type II receptor (TbetaRIIED) at the biosensor surface in an oriented and stable manner by using a de novo designed coiled-coil (E/K coil) heterodimerizing system. We characterized the kinetics of binding of three TGF-beta isoforms to this immobilized TbetaRIIED. The results demonstrate that the stoichiometry of TGF-beta binding to TbetaRIIED was one dimeric ligand to two receptors. All three TGF-beta isoforms had rapid and similar association rates, but different dissociation rates, which resulted in the equilibrium dissociation constants being approximately 5pM for the TGF-beta1 and -beta3 isoforms, and 5nM for the TGF-beta2 isoform. Since these apparent affinities are at least four orders of magnitude higher than those determined when TGF-beta was immobilized, and are close to those determined for TbetaRII at the cell surface, we suggest that avidity contributes significantly to high affinity receptor binding both at the biosensor and cell surfaces. Finally, we demonstrated that the coiled-coil immobilization approach does not require the purification of the captured protein, making it an attractive tool for the rapid study of any protein-protein interaction.     

Requirement of Smad3 for mast cell growth

The involvement of the TGF-beta family in cell growth of bone marrow-derived mast cells (BMMC) cultured with medium containing pokeweed mitogen-stimulated spleen cell-conditioned medium (PWM-SCM) was examined. Doubling time of BMMC from Smad3-null mice was longer than that from wild-type (WT) mice, and the differences tended to be larger with time of culture. Consistent with the results, uptake and reduction of [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt; MTS] was lower in Smad3-deficient BMMC. Cell cycle analyses revealed no apparent differences between WT BMMC and Smad3-deficient BMMC, suggesting that longer doubling time in Smad3-deficient BMMC resulted from increased cell death. TGF-beta and activin A were supplied by PWM-SCM rather than by self-production by BMMC. Blocking the TGF-beta pathway by anti-TGF-beta neutralizing antibody or an inhibitor for the type I receptors for ligands including TGF-beta and activin, SB431542, inhibited MTS uptake and reduction in WT BMMC, whereas anti-activin A antibody and SB431542 tended to inhibit them in Smad3-deficient BMMC. The present results suggest that TGF-beta-induced and Smad3-mediated signaling is essential for maximal cell growth in mast cells, and that the activin pathway may be required for it when mast cell context is modulated by Smad3 depletion.     

The clinical and biological roles of transforming growth factor beta in colon cancer stem cells: A systematic review

Background

Transforming growth factor beta (TGF-β) is a multipurpose cytokine, which plays a role in many cellular functions such as proliferation, differentiation, migration, apoptosis, cell adhesion and regulation of epithelial to mesenchymal transition. Despite many studies having observed the effect that TGF-β plays in colorectal cancer, its role in the colorectal stem cell population has not been widely observed.

The role of activin in neuropeptide induction and pain sensation

Signals from target tissues play critical roles in the functional differentiation of neuronal cells, and in their subsequent adaptations to peripheral changes in the adult. Sensory neurons in the dorsal root ganglia (DRG) provide an excellent model system for the study of signals that regulate the development of neuronal diversity. DRG have been well characterized and contain both neurons that convey information from muscles about limb position, as well as other neurons that provide sensations from skin about pain information. Sensory neurons involved in pain sensation can be distinguished physiologically and antigenically, and one hallmark characteristic is that these neurons contain neuropeptides important for their functions. The transforming growth factor (TGF) beta family member activin A has recently been implicated in neural development and response to injury. During sensory neuron development, peripheral target tissues containing activin or activin itself can regulate pain neuropeptide expression. Long after development has ceased, skin target tissues retain the capacity to signal neurons about changes or injury, to functionally refine synapses. This review focuses on the role of activin as a target-derived differentiative factor in neural development that has additional roles in response to cutaneous injuries in the adult.     

Mechanisms of action of bone morphogenetic proteins in cancer

The bone morphogenetic proteins (BMPs) play fundamental roles in embryonic development and control differentiation of a diverse set of cell types. It is therefore of no surprise that the BMPs also contribute to the process of tumourigenesis and regulate cancer progression through various stages. We summarise here key roles of BMP ligands, receptors, their signalling mediators, mainly focusing on proteins of the Smad family, and extracellular antagonists, that contribute to the onset of tumourigenesis and to cancer progression in diverse tissues. Overall, the BMP pathways seem to act as tumour suppressors that maintain physiological tissue homeostasis and which are perturbed in cancer either via genetic mutation or via epigenetic misregulation of key gene components. BMPs also control the self-renewal and fate choices made by stem cells in several tissues. By promoting cell differentiation, including inhibition of the process of epithelial-mesenchymal transition, BMPs contribute to the malignant progression of cancer at advanced stages. It is therefore reasonable that pharmaceutical industries continuously develop biological agents and chemical modulators of BMP signalling with the aim to improve therapeutic regimes against several types of cancer.     

P311 binds to the latency associated protein and downregulates the expression of TGF-beta1 and TGF-beta2

P311 is an 8-kDa protein originally found in neurons and muscle. We recently showed that expression of P311 in NIH 3T3 cells induced a myofibroblast phenotype with low TGF-beta1 expression. Here we demonstrate that P311 downregulates not only TGF-beta1, but also TGF-beta2, expression, with no effect on TGF-beta3. In addition, P311 interacts with TGF-beta2 in a yeast two-hybrid system through a sequence encompassing part of the TGF-beta latent associated protein (LAP) and part of mature TGF-beta2. Coimmunoprecipitations demonstrated interaction between P311 and TGF-beta1 and 2, but not TGF-beta3. Additional coimmunoprecipitations after introducing LAP or mature TGF-beta1 into cells demonstrated P311 binding to LAP, but not to mature TGF-beta. P311 has a conserved PEST domain, which generally serves as a rapid degradation signal. Deletion of the PEST domain reversed the effect of P311 on TGF-beta isoforms. Finally, Smad3 activity was decreased in P311-expressing cells, but was corrected by exogenous TGF-beta1 treatment, which also elevated TGF-beta1 mRNA level. This suggested that P311 downregulates TGF-beta1 and 2 in part by blocking TGF-beta autoinduction.     

The role of effectors of the activin signalling pathway, activin receptors IIA and IIB, and Smad2, in patterning of tooth development.

The gene for activin betaA is expressed in the early odontogenic mesenchyme of all murine teeth but mutant mice show a patterning defect where incisors and mandibular molars fail to develop but maxillary molars develop normally. In order to understand why maxillary molar tooth development can proceed in the absence of activin, we have explored the role of mediators of activin signalling in tooth development. Analysis of tooth development in activin receptor II and Smad2 mutants shows that a similar tooth phenotype to activin betaA mutants can be observed. In addition, we identify a novel downstream target of activin signalling, the Iroquois-related homeobox gene, Irx1, and show that its expression in activin betaA mutant embryos is lost in all tooth germs, including the maxillary molars. These results strongly suggest that other transforming growth factor beta molecules are not stimulating the activin signalling pathway in the absence of activin. This was confirmed by a non-genetic approach using exogenous soluble receptors to inhibit all activin signalling in tooth development, which reproduced the genetic phenotypes. Activin, thus, has an essential role in early development of incisor and mandibular molar teeth but this pathway is not required for development of maxillary molars.     

Ozone therapy restores immune dysfunction in refractory idiopathic granulomatous mastitis as a novel potential therapeutic approach

Immunological dysfunction has been suggested to play a major role in the pathogenesis of idiopathic granulomatous mastitis (IGM). We recently showed that ozone therapy was effective in patients with steroid-resistant IGM. This study assessed alterations in intracellular cytokine expression patterns in different T-lymphocyte subsets after ozone therapy in refractory IGM. Peripheral blood T lymphocyte subsets (CD8⁺, CD4⁺, CD4⁺CD25⁺CD127⁻) were analyzed via flow-cytometry for intracellular cytokine expressions IFN-γ, TNF-α, IL-10, and TGF-β before and after completion of 4-month systemic ozone therapy. Ozone therapy significantly increased the CD4⁺IFN-γ⁺ (p = 0.032), CD4⁺TNF-α⁺ (p = 0.028), and the CD8⁺TNF-α⁺ (p = 0.012) T cells. In contrast, significant decreases in CD4⁺ IL-10⁺ (p = 0.047) and CD8⁺IL-10⁺ T cells (p = 0.022) and CD4⁺CD25⁺CD127^−//low Treg cells secreting TGF-β (p = 0.005) were found after ozone therapy. When patients were analyzed according to the response to ozone therapy, patients with a complete remission were more likely to have increased CD3⁻CD16⁺CD56⁺ natural killer cells (p = 0.0027) and decreased CD19⁺ B lymphocytes (p = 0.046) following ozone therapy. Our results suggest that ozone therapy stimulated a T-helper-1 response associated with IFN-γ production and downregulation of TGF-β expression in CD4⁺CD25⁺CD127⁻ Treg cells. These alterations in the immune system following ozone therapy can improve wound healing and restore immune dysfunction in patients with refractory IGM.     

Expression of activin subunits and receptors in the developing human ovary: activin A promotes germ cell survival and proliferation before primordial follicle formation

The formation of the essential functional unit of the ovary, the primordial follicle, occurs during fetal life in humans. Factors regulating oogonial proliferation and interaction with somatic cells before primordial follicle formation are largely unknown. We have investigated the expression, localisation and functional effects of activin and its receptors in the human fetal ovary at 14-21 weeks gestation. Expression of mRNA for the activin betaA and betaB subunits and the activin receptors ActRIIA and ActRIIB was demonstrated by RT-PCR. Expression of betaA mRNA increased 2-fold across the gestational range examined. Activin subunits and receptors were localised by immunohistochemistry. The betaA subunit was expressed by oogonia, and the betaB subunit and activin receptors were expressed by both oogonia and somatic cells. BetaA expression was increased in larger oogonia at later gestations, but was low in oocytes within newly formed primordial follicles. Treatment of ovary fragments with activin A in vitro increased both the number of oogonia present and oogonial proliferation, as detected by bromodeoxyuridine (BrdU) incorporation. These data indicate that activin may be involved in the autocrine and paracrine regulation of germ cell proliferation in the human ovary during the crucial period of development leading up to primordial follicle formation.     

miR‐124 interacts with the Notch1 signalling pathway and has therapeutic potential against gastric cancer

Aberrant Notch signalling plays an important role in cancer progression. However, little is known about the interaction between miRNA and the Notch signalling pathway and its role in gastric cancer (GC). In this study, we found that miR‐124 was down‐regulated in GC compared with adjacent normal tissue. Forced expression of miR‐124 inhibited GC cell growth, migration and invasion, and induced cell cycle arrest. miR‐124 negatively regulated Notch1 signalling by targeting JAG1. miR‐124 levels were also shown to be inversely correlated with JAG1 expression in GC. Furthermore, we found that the overexpression of the intracellular domain of Notch1 repressed miR‐124 expression, promoted GC cell growth, migration and invasion. Conversely, blocking Notch1 using a γ‐secretase inhibitor up‐regulated miR‐124 expression, inhibited GC cell growth, migration and invasion. In conclusion, our data demonstrates a regulatory feedback loop between miR‐124 and Notch1 signalling in GC cells, suggesting that the miR‐124/Notch axis may be a potential therapeutic target against GC.     

Activin promotes differentiation of cultured mouse trophoblast stem cells towards a labyrinth cell fate

Prolonged maintenance of trophoblast stem (TS) cells requires fibroblast growth factor (FGF) 4 and embryonic fibroblast feeder cells or feeder cell-conditioned medium. Previous studies have shown that TGF-β and Activin are sufficient to replace embryonic fibroblast-conditioned medium. Nodal, a member of the TGF-β superfamily, is also known to be important in vivo for the maintenance of TS cells in the developing placenta. Our current studies indicate that TS cells do not express the Nodal co-receptor, Cripto, and do not respond directly to active Nodal in culture. Conversely, Activin subunits and their receptors are expressed in the placenta and TS cell cultures, with Activin predominantly expressed by trophoblast giant cells (TGCs). Differentiation of TS cells in the presence of TGC-conditioned medium or exogenous Activin results in a reduction in the expression of TGC markers. In line with TGC-produced Activin representing the active component in TGC-conditioned medium, this differentiation-inhibiting effect can be reversed by the addition of follistatin. Additional experiments in which TS cells were differentiated in the presence or absence of exogenous Activin or TGF-β show that Activin but not TGF-β results in the maintenance of expression of TS cell markers, prolongs the expression of syncytiotrophoblast markers, and significantly delays the expression of spongiotrophoblast and TGC markers. These results suggest that Activin rather than TGF-β (or Nodal) acts directly on TS cells influencing both TS cell maintenance and cell fate, depending on whether the cells are also exposed to FGF4.     

Regulation of human erythropoiesis by activin A,BMP2, and BMP4, members of the TGFbeta family

Activin A, BMP2, and BMP4, members of the TGFbeta family, have been implicated in the regulation of hematopoiesis. Here we explore and compare, for the first time in human primary cells, the role of activin A, BMP2, and BMP4 during erythropoiesis. Using in vitro erythroid differentiation of CD34(+) primary cells, we obtained the main stages of early erythropoiesis, characterized at the molecular, biochemical, and functional levels. Our results indicate that BMP2 acts on early erythroid cells and activin A on a more differentiated population. We report an insight into the mechanism of commitment of erythropoiesis by activin A and BMP2 involving two key events, increase in EPO-R and decrease in GATA2 expression. Simultaneous addition of activin A with BMP molecules suggests that BMP2 and BMP4 differently affect activin A induction of erythropoiesis. Follistatin and FLRG proteins downmodulate the effects of activin A and BMP2 on erythroid maturation.