Abstract
Transforming growth factor-β (TGF-β), a potent inducer of collagen synthesis, is implicated in pathological fibrosis. Peroxisome proliferator-activated receptor-γ (PPAR-γ) is a nuclear hormone receptor that regulates adipogenesis and numerous other biological processes. Here, we demonstrate that collagen gene expression was markedly elevated in mouse embryonic fibroblasts (MEFs) lacking PPAR-γ compared to heterozygous control MEFs. Treatment with the PPAR-γ ligand 15d-PGJ2 failed to down-regulate collagen gene expression in PPAR-γ null MEFs, whereas reconstitution of these cells with ectopic PPAR-γ resulted in their normalization. Compared to control MEFs, PPAR-γ null MEFs displayed elevated levels of the Type I TGF-β receptor (TβRI), and secreted more TGF-β1 into the media. Furthermore, PPAR-γ null MEFs showed constitutive phosphorylation of cellular Smad2 and Smad3, even in the absence of exogenous TGF-β, which was abrogated by the ALK5 inhibitor SB431542. Constitutive Smad2/3 phosphorylation in PPAR-γ null MEFs was associated with Smad3 binding to its cognate DNA recognition sequences, and interaction with coactivator p300 previously implicated in TGF-β responses. Taken together, these results indicate that loss of PPAR-γ in MEFs is associated with upregulation of collagen synthesis, and activation of intracellular Smad signal transduction, due, at least in part, to autocrine TGF-β stimulation.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 231-236 |
| Number of pages | 6 |
| Journal | Biochemical and Biophysical Research Communications |
| Volume | 374 |
| Issue number | 2 |
| DOIs | |
| State | Published - Sep 19 2008 |
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Keywords
- Collagen
- Fibrosis
- PPAR-γ
- Smad
- TGF-β
- TbRI
- p300
ASJC Scopus subject areas
- Biochemistry
- Biophysics
- Molecular Biology
Cite this
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Constitutive Smad signaling and Smad-dependent collagen gene expression in mouse embryonic fibroblasts lacking peroxisome proliferator-activated receptor-γ. / Ghosh, Asish K; Wei, Jun; Wu, Minghua; Varga, John.
In: Biochemical and Biophysical Research Communications, Vol. 374, No. 2, 19.09.2008, p. 231-236.Research output: Contribution to journal › Article
TY - JOUR
T1 - Constitutive Smad signaling and Smad-dependent collagen gene expression in mouse embryonic fibroblasts lacking peroxisome proliferator-activated receptor-γ
AU - Ghosh, Asish K
AU - Wei, Jun
AU - Wu, Minghua
AU - Varga, John
PY - 2008/9/19
Y1 - 2008/9/19
N2 - Transforming growth factor-β (TGF-β), a potent inducer of collagen synthesis, is implicated in pathological fibrosis. Peroxisome proliferator-activated receptor-γ (PPAR-γ) is a nuclear hormone receptor that regulates adipogenesis and numerous other biological processes. Here, we demonstrate that collagen gene expression was markedly elevated in mouse embryonic fibroblasts (MEFs) lacking PPAR-γ compared to heterozygous control MEFs. Treatment with the PPAR-γ ligand 15d-PGJ2 failed to down-regulate collagen gene expression in PPAR-γ null MEFs, whereas reconstitution of these cells with ectopic PPAR-γ resulted in their normalization. Compared to control MEFs, PPAR-γ null MEFs displayed elevated levels of the Type I TGF-β receptor (TβRI), and secreted more TGF-β1 into the media. Furthermore, PPAR-γ null MEFs showed constitutive phosphorylation of cellular Smad2 and Smad3, even in the absence of exogenous TGF-β, which was abrogated by the ALK5 inhibitor SB431542. Constitutive Smad2/3 phosphorylation in PPAR-γ null MEFs was associated with Smad3 binding to its cognate DNA recognition sequences, and interaction with coactivator p300 previously implicated in TGF-β responses. Taken together, these results indicate that loss of PPAR-γ in MEFs is associated with upregulation of collagen synthesis, and activation of intracellular Smad signal transduction, due, at least in part, to autocrine TGF-β stimulation.
AB - Transforming growth factor-β (TGF-β), a potent inducer of collagen synthesis, is implicated in pathological fibrosis. Peroxisome proliferator-activated receptor-γ (PPAR-γ) is a nuclear hormone receptor that regulates adipogenesis and numerous other biological processes. Here, we demonstrate that collagen gene expression was markedly elevated in mouse embryonic fibroblasts (MEFs) lacking PPAR-γ compared to heterozygous control MEFs. Treatment with the PPAR-γ ligand 15d-PGJ2 failed to down-regulate collagen gene expression in PPAR-γ null MEFs, whereas reconstitution of these cells with ectopic PPAR-γ resulted in their normalization. Compared to control MEFs, PPAR-γ null MEFs displayed elevated levels of the Type I TGF-β receptor (TβRI), and secreted more TGF-β1 into the media. Furthermore, PPAR-γ null MEFs showed constitutive phosphorylation of cellular Smad2 and Smad3, even in the absence of exogenous TGF-β, which was abrogated by the ALK5 inhibitor SB431542. Constitutive Smad2/3 phosphorylation in PPAR-γ null MEFs was associated with Smad3 binding to its cognate DNA recognition sequences, and interaction with coactivator p300 previously implicated in TGF-β responses. Taken together, these results indicate that loss of PPAR-γ in MEFs is associated with upregulation of collagen synthesis, and activation of intracellular Smad signal transduction, due, at least in part, to autocrine TGF-β stimulation.
KW - Collagen
KW - Fibrosis
KW - PPAR-γ
KW - Smad
KW - TGF-β
KW - TbRI
KW - p300
UR - http://www.scopus.com/inward/record.url?scp=48349108129&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=48349108129&partnerID=8YFLogxK
U2 - 10.1016/j.bbrc.2008.07.014
DO - 10.1016/j.bbrc.2008.07.014
M3 - Article
VL - 374
SP - 231
EP - 236
JO - Biochemical and Biophysical Research Communications
JF - Biochemical and Biophysical Research Communications
SN - 0006-291X
IS - 2
ER -