scholarly journals Roles of Autocrine TGF-β Receptor and Smad Signaling in Adipocyte Differentiation

2000 ◽  
Vol 149 (3) ◽  
pp. 667-682 ◽  
Author(s):  
Lisa Choy ◽  
Jeremy Skillington ◽  
Rik Derynck
Keyword(s):  
Adipocyte Differentiation ◽  
Inhibitory Effect ◽  
Dominant Negative ◽  
Mrna Levels ◽  
Induced Responses ◽  
Type Ii ◽  
Negative Regulators ◽  
Dominant Negative Interference ◽  
Β Receptor

TGF-β inhibits adipocyte differentiation, yet is expressed by adipocytes. The function of TGF-β in adipogenesis, and its mechanism of action, is unknown. To address the role of TGF-β signaling in adipocyte differentiation, we characterized the expression of the TGF-β receptors, and the Smads which transmit or inhibit TGF-β signals, during adipogenesis in 3T3-F442A cells. We found that the cell-surface availability of TGF-β receptors strongly decreased as adipogenesis proceeds. Whereas mRNA levels for Smads 2, 3, and 4 were unchanged during differentiation, mRNA levels for Smads 6 and 7, which are known to inhibit TGF-β responses, decreased severely. Dominant negative interference with TGF-β receptor signaling, by stably expressing a truncated type II TGF-β receptor, enhanced differentiation and decreased growth. Stable overexpression of Smad2 or Smad3 inhibited differentiation and dominant negative inhibition of Smad3 function, but not Smad2 function, enhanced adipogenesis. Increased Smad6 and Smad7 levels blocked differentiation and enhanced TGF-β–induced responses. The inhibitory effect of Smad7 on adipocyte differentiation and its cooperation with TGF-β was associated with the C-domain of Smad7. Our results indicate that endogenous TGF-β signaling regulates the rate of adipogenesis, and that Smad2 and Smad3 have distinct functions in this endogenous control of differentiation. Smad6 and Smad7 act as negative regulators of adipogenesis and, even though known to inhibit TGF-β responses, enhance the effects of TGF-β on these cells.

Reactive oxygen species modulate HIF-1 mediated PAI-1 expression: involvement of the GTPase Rac1

2003 ◽  
Vol 89 (05) ◽  
pp. 926-935 ◽  
Author(s):  
Utta Berchner-Pfannschmidt ◽  
Christoph Wotzlaw ◽  
Robbert Cool ◽  
Joachim Fandrey ◽  
Helmut Acker ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Reactive Oxygen ◽  
Plasminogen Activator Inhibitor ◽  
Dominant Negative ◽  
Mrna Levels ◽  
Ros Production ◽  
Oxygen Species ◽  
Plasminogen Activator Inhibitor 1 ◽  
Pai 1

SummaryThe hypoxia-inducible transcription factor HIF-1 mediates upregulation of plasminogen activator inhibitor-1 (PAI-1) expression under hypoxia. Reactive oxygen species (ROS) have also been implicated in PAI-1 gene expression. However, the role of ROS in HIF-1-mediated regulation of PAI-1 is not clear. We therefore investigated the role of the GTPase Rac1 which modulates ROS production in the pathway leading to HIF-1 and PAI-1 induction.Overexpression of constitutively activated (RacG12V) or dominant-negative (RacT17N) Rac1 increased or decreased, respectively, ROS production. In RacG12V-expressing cells, PAI-1 mRNA levels as well as HIF-1α nuclear presence were reduced under normoxia and hypoxia whereas expression of RacT17N resulted in opposite effects. Treatment with the antioxidant pyrrolidinedithiocarbamate or coexpression of the redox factor-1 restored HIF-1 and PAI-1 promoter activity in RacG12V-cells. In contrast, NFκB activation was enhanced in RacG12V-cells, but abolished by RacT17N. Thus, these findings suggest a mechanism explaining modified fibrinolysis and tissue remodeling in an oxidized environment.

scholarly journals Cyclin G2 Regulates Adipogenesis through PPARγ Coactivation

Endocrinology ◽  
2010 ◽  
Vol 151 (11) ◽  
pp. 5247-5254 ◽  
Author(s):  
Victor Aguilar ◽  
Jean-Sébastien Annicotte ◽  
Xavier Escote ◽  
Joan Vendrell ◽  
Dominique Langin ◽  
...  
Keyword(s):  
Adipocyte Differentiation ◽  
Luciferase Reporter ◽  
Peroxisome Proliferator ◽  
Mrna Levels ◽  
Cell Cycle Regulators ◽  
Luciferase Reporter Gene ◽  
Peroxisome Proliferator Activated Receptor ◽  
Cyclin G2 ◽  
Regulatory Effects

Cell cycle regulators such as cyclins, cyclin-dependent kinases, or retinoblastoma protein play important roles in the differentiation of adipocytes. In the present paper, we investigated the role of cyclin G2 as a positive regulator of adipogenesis. Cyclin G2 is an unconventional cyclin which expression is up-regulated during growth inhibition or apoptosis. Using the 3T3-F442A cell line, we observed an up-regulation of cyclin G2 expression at protein and mRNA levels throughout the process of cell differentiation, with a further induction of adipogenesis when the protein is transiently overexpressed. We show here that the positive regulatory effects of cyclin G2 in adipocyte differentiation are mediated by direct binding of cyclin G2 to peroxisome proliferator-activated receptor γ (PPARγ), the key regulator of adipocyte differentiation. The role of cyclin G2 as a novel PPARγ coactivator was further demonstrated by chromatin immunoprecipitation assays, which showed that the protein is present in the PPARγ-responsive element of the promoter of aP2, which is a PPARγ target gene. Luciferase reporter gene assays, showed that cyclin G2 positively regulates the transcriptional activity of PPARγ. The role of cyclin G2 in adipogenesis is further underscored by its increased expression in mice fed a high-fat diet. Taken together, our results demonstrate a novel role for cyclin G2 in the regulation of adipogenesis.

Inhibitory effect of green tea (−)-epigallocatechin gallate on resistin gene expression in 3T3-L1 adipocytes depends on the ERK pathway

2006 ◽  
Vol 290 (2) ◽  
pp. E273-E281 ◽  
Author(s):  
Hang-Seng Liu ◽  
Yen-Hang Chen ◽  
Pei-Fang Hung ◽  
Yung-Hsi Kao
Keyword(s):  
Green Tea ◽  
Adipocyte Differentiation ◽  
Epigallocatechin Gallate ◽  
Inhibitory Effect ◽  
Mrna Levels ◽  
Erk Pathway ◽  
Extracellular Signal ◽  
Basal Half ◽  
The Stability ◽  
New Protein

Resistin (Rstn) is known as an adipocyte-specific secretory hormone that can cause insulin resistance and decrease adipocyte differentiation. By contrast, green tea catechins, especially (−)-epigallocatechin gallate (EGCG), have been reported as body weight and diabetes chemopreventatives. Whether EGCG regulates production of Rstn is unknown. Using 3T3-L1 adipocytes, we found that EGCG at 20 and 100 μM suppressed Rstn mRNA levels by ∼35 and 50%, respectively, after 3 h. The basal half-life of Rstn mRNA induced by actinomycin D was >12 h but shifted to 3 h in the presence of EGCG. This suggests that EGCG regulates the stability of Rstn mRNA. Treatment with cycloheximide did not prevent EGCG-suppressed Rstn mRNA levels, which suggests that the effect of EGCG does not require new protein synthesis. Intracellular Rstn protein significantly decreased in the presence of 100 μM EGCG 3 h after treatment, whereas the release of the Rstn protein did not significantly change. This suggests that EGCG may modulate the distribution of Rstn protein between the intracellular and extracellular compartments. EGCG did not affect the amounts of extracellular signal-related kinase-1/2 (ERK1/2), phospho-JNK, phospho-p38, and phospho-Akt proteins but reduced the amounts of phospho-ERK1/2 proteins. Overexpression with MEK1 blocked EGCG-inhibited Rstn mRNA expression. These data suggest that EGCG downregulates Rstn expression via a pathway that is dependent on the ERK pathway.

scholarly journals Overexpression of microRNA-21 is associated with elevated pro-inflammatory cytokines in dominant-negative TGF-β receptor type II mouse

2013 ◽  
Vol 41 ◽  
pp. 111-119 ◽  
Author(s):  
Yugo Ando ◽  
Guo-Xiang Yang ◽  
Thomas P. Kenny ◽  
Kazuhito Kawata ◽  
Weici Zhang ◽  
...  
Keyword(s):  
Inflammatory Cytokines ◽  
Dominant Negative ◽  
Receptor Type ◽  
Type Ii ◽  
Β Receptor ◽  
Pro Inflammatory Cytokines

Leukemia inhibitory factor regulates glucocorticoid receptor expression in the hypothalamic-pituitary-adrenal axis

2005 ◽  
Vol 289 (5) ◽  
pp. E857-E863 ◽  
Author(s):  
Anastasia Kariagina ◽  
Svetlana Zonis ◽  
Mahta Afkhami ◽  
Dmitry Romanenko ◽  
Vera Chesnokova
Keyword(s):  
Glucocorticoid Receptor ◽  
Hpa Axis ◽  
Leukemia Inhibitory Factor ◽  
Dominant Negative ◽  
Receptor Expression ◽  
Inhibitory Factor ◽  
Mrna Levels ◽  
Hypothalamic Pituitary Adrenal ◽  
Protein Levels

Leukemia inhibitory factor (LIF) is a pleiotropic cytokine belonging to the gp130 family. LIF is induced peripherally and within the brain during inflammatory or chronic autoimmune diseases and is a potent stimulator of the hypothalamic-pituitary-adrenal (HPA) axis. Here we investigated the role of LIF in mediating glucocorticoid receptor (GR) expression in the HPA axis. LIF treatment (3 μg/mouse, ip) markedly decreased GR mRNA levels in murine hypothalamus (5-fold, P < 0.01) and pituitary (1.7-fold, P < 0.01) and downregulated GR protein levels. LIF decreased GR expression in murine corticotroph cell line AtT20 within 2 h, and this effect was sustained for 8 h after treatment. LIF-induced GR mRNA reduction was abrogated in AtT20 cells overexpressing dominant-negative mutants of STAT3, indicating that intact JAK-STAT signaling is required to mediate LIF effects on GR expression. Conversely, mice with LIF deficiency exhibited increased GR mRNA levels in the hypothalamus and pituitary (3.5- and 3.5-fold, respectively; P < 0.01 for both) and increased GR protein expression when compared with wild-type littermates. The suppressive effects of dexamethasone on GR were more pronounced in LIF-null animals. These data suggest that LIF maintains the HPA axis activation by decreasing GR expression and raise the possibility that LIF might contribute to the development of central glucocorticoid resistance during inflammation.

Induction of mucin gene expression in human colonic cell lines by PMA is dependent on PKC-ε

1999 ◽  
Vol 277 (5) ◽  
pp. G1041-G1047 ◽  
Author(s):  
D.-H. Hong ◽  
G. Petrovics ◽  
W. B. Anderson ◽  
J. Forstner ◽  
G. Forstner
Keyword(s):  
Gene Expression ◽  
Cell Lines ◽  
Dominant Negative ◽  
Mrna Levels ◽  
Wild Type ◽  
Mucin Gene ◽  
Time Period ◽  
Mucin Expression ◽  
Mucin Genes

Treatment of HT-29 cells with phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C (PKC), induces MUC2 expression. To investigate the role of PKC in regulating mucin genes in intestinal cells, we examined the regulation of MUC1, MUC2, MUC5AC, MUC5B, and MUC6 expression in two human mucin-producing colonic cell lines, T84 and HT29/A1. T84 and HT29/A1 cells (at 80–90% confluency) were exposed to 100 nM PMA for 0, 3, and 6 h. Twofold or greater increases in mRNA levels for MUC2 and MUC5AC were observed in both cell lines during this time period, whereas the levels of MUC1, MUC5B, and MUC6 mRNAs were only marginally affected. These results indicated that PKC differentially regulates mucin gene expression and that it may be responsible for altered mucin expression. Our previous results suggested that the Ca2+-independent PKC-ε isoform appeared to mediate PMA-regulated mucin exocytosis in these cell lines. To determine if PKC-ε was also involved in MUC2/MUC5AC gene induction, HT29/A1 cells were stably transfected with either a wild-type PKC-ε or a dominant-negative ATP-binding mutant of PKC-ε (PKC-ε K437R). Overexpression of the dominant-negative PKC-ε K437R blocked induction of both mucin genes, whereas PMA-induced mucin gene expression was not prevented by overexpression of wild-type PKC-ε. PMA-dependent MUC2 mucin secretion was also blocked in cells overexpressing the dominant-negative PKC-ε K437R. On the basis of these observations, PKC-ε appears to mediate the expression of two major gastrointestinal mucins in response to PMA as well as PMA-regulated mucin exocytosis.

scholarly journals Erythropoietin's inhibiting impact on hepcidin expression occurs indirectly

2015 ◽  
Vol 308 (4) ◽  
pp. R330-R335 ◽  
Author(s):  
Elena Gammella ◽  
Victor Diaz ◽  
Stefania Recalcati ◽  
Paolo Buratti ◽  
Michele Samaja ◽  
...  
Keyword(s):  
Direct Interaction ◽  
Inhibitory Effect ◽  
Mrna Levels ◽  
Liver Iron ◽  
Hepcidin Expression ◽  
Direct Binding ◽  
High Doses ◽  
Hepcidin Mrna ◽  
Great Inhibition

Under conditions of accelerated erythropoiesis, elevated erythropoietin (Epo) levels are associated with inhibition of hepcidin synthesis, a response that ultimately increases iron availability to meet the enhanced iron needs of erythropoietic cells. In the search for erythroid regulators of hepcidin, many candidates have been proposed, including Epo itself. We aimed to test whether direct interaction between Epo and the liver is required to regulate hepcidin. We found that prolonged administration of high doses of Epo in mice leads to great inhibition of liver hepcidin mRNA levels, and concomitant induction of the hepcidin inhibitor erythroferrone (ERFE). Epo treatment also resulted in liver iron mobilization, mediated by increased ferroportin activity and accompanied by reduced ferritin levels and increased TfR1 expression. The same inhibitory effect was observed in mice that do not express the homodimeric Epo receptor (EpoR) in liver cells because EpoR expression is restricted to erythroid cells. Similarly, liver signaling pathways involved in hepcidin regulation were not influenced by the presence or absence of hepatic EpoR. Moreover, Epo analogs, possibly interacting with the postulated heterodimeric β common EpoR, did not affect hepcidin expression. These findings were supported by the lack of inhibition on hepcidin found in hepatoma cells exposed to various concentrations of Epo for different periods of times. Our results demonstrate that hepcidin suppression does not require the direct binding of Epo to its liver receptors and rather suggest that the role of Epo is to stimulate the synthesis of the erythroid regulator ERFE in erythroblasts, which ultimately downregulates hepcidin.

Sign in / Sign up

Export Citation Format

Share Document