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    Role of SMAD and Non-SMAD Signals in the Development of Th17 and Regulatory T Cells
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    Abstract:
    Whereas TGF-beta is essential for the development of peripherally induced Foxp3(+) regulatory T cells (iTreg cells) and Th17 cells, the intracellular signaling mechanism by which TGF-beta regulates development of both cell subsets is less understood. In this study, we report that neither Smad2 nor Smad3 gene deficiency abrogates TGF-beta-dependent iTreg induction by a deacetylase inhibitor trichostatin A in vivo, although the loss of the Smad2 or Smad3 gene partially reduces iTreg induction in vitro. Similarly, SMAD2 and SMAD3 have a redundant role in development of Th17 in vitro and in experimental autoimmune encephalomyelitis. In addition, ERK and/or JNK pathways were shown to be involved in regulating iTreg cells, whereas the p38 pathway predominately modulated Th17 and experimental autoimmune encephalomyelitis induction. Therefore, selective targeting of these intracellular TGF-beta signaling pathways during iTreg and Th17 cell development might lead to the development of therapies in treating autoimmune and other chronic inflammatory diseases.
    TGF-beta and activin induce the phosphorylation and activation of Smad2 and Smad3, but how these proteins stimulate gene transcription is poorly understood. We report that TGF-beta receptor phosphorylation of Smad3 promotes its interaction with the paralogous coactivators CBP and p300, whereas CBP/p300 binding to nonphosphorylated Smad3 or its oligomerization partner Smad4 is negatively regulated by Smad-intramolecular interactions. Furthermore, p300 and TGF-beta receptor-phosphorylated Smad3 synergistically augment transcriptional activation. Thus, CBP/p300 are important components of activin/TGF-beta signaling and may mediate the antioncogenic functions of Smad2 and Smad4.
    Smad2 Protein
    R-SMAD
    ACVR2B
    Activin receptor
    Transcription
    Citations (503)
    To investigate the role of Th17/Treg unbalance in the pathogenesis of experimental autoimmune encephalomyelitis (EAE).EAE was modeled in mice and the number of regulatory T cells (Tregs) in spleen of EAE mice was detected by flow cytometry. The expressions of Foxp3 and RoR-γt mRNA in the spleen of EAE mice and IL-17 mRNA in the brain of EAE mice were evaluated by real-time quantitative PCR and the levels of IL-6, TGF-β and IL-17 in the serum of EAE mice were examined by ELISA.Compared with control group, the number of CD4(+)CD25(+) Foxp3(+) Tregs and the expression of Foxp3 mRNA in the spleen of EAE mice dramatically decreased in the early and peak stage of EAE (P<0.05), but increased in chronic stage of EAE (P<0.05); the RoR-γt mRNA expression from mouse spleen at the early stage of EAE was significant raised (P<0.05), but was not significantly different at the peak and chronic stage of EAE from that in control group (P>0.05). The levels of IL-6 and TGF-β in the serum of EAE group dramatically increased compared with control group (P<0.05). With the development of EAE, the level of IL-6 gradually decreased, and there was no statistical difference in the chronic stage of EAE compared with control group (P>0.05). However, the level of TGF-β was higher than that in control group in the chronic stage of EAE (P<0.05). Compared with those in control group, the concentration of IL-17A and the expression of IL-17 mRNA dramatically increased in different stages of EAE group, especially in peak stage (P<0.05).Th17/Treg unbalance may be involved in the pathogenesis of EAE.
    Pathogenesis
    Encephalomyelitis
    Regulatory T cell
    Citations (5)
    To explore the roles of Smad 2/3 in transforming growth factor-beta(1) (TGF-beta(1)) signaling by human dental pulp cells.Laser scanning confocal microscope was used to observe translocation of Smad 2/3 from plasma into nucleus in cultured dental pulp cells at early stage of TGF-beta(1) treatment, and changes of Smad 2/3 protein expression at later stage were evaluated by Western blot analyses.The expression of Smad 2/3 (fluorescence intensity) kept decreasing in cytoplasm but increasing in nucleus within 2 h after TGF-beta(1) treatment, forming a trend that Smad 2/3 translocated into nucleus from cytoplasma. The total amount of Smad 2 protein remained unchanged before and after TGF-beta(1) treatment, but the expression level of Smad 3 decreased markedly after 24 h treatment and kept dropping by 48 h.The results suggest that the Smad 2/3 may be the downstream signal transducers of TGF-beta(1) in human dental pulp cells and Smad 2/3 may mediate TGF-beta(1) signaling by translocation early in TGF-beta(1) treatment, while down-regulation of Smad 3 expression by TGF-beta(1) at later stage is involved in negative modulation of TGF-beta(1) signaling.
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