| Abstract | Transforming growth factor-beta (TGF-beta) is a cytokine implicated in wound healing and in the pathogenesis of pulmonary fibrosis. TGF-beta stimulates myofibroblast differentiation characterized by expression of contractile smooth muscle (SM)-specific proteins such as SM-alpha-actin. In the present study, we examined the role of serum response factor (SRF) in the mechanism of TGF-beta-induced pulmonary myofibroblast differentiation of human lung fibroblasts (HLF). TGF-beta stimulated SM-alpha-actin expression in HLF, which paralleled with a profound induction of SRF expression and activity. Inhibition of SRF by the pharmacologic SRF inhibitor (CCG-1423), or via adenovirus-mediated transduction of SRF short hairpin RNA (shSRF), blocked the expression of both SRF and SM-alpha-actin in response to TGF-beta without affecting Smad-mediated signaling of TGF-beta. However, forced expression of SRF on its own did not promote SM-alpha-actin expression, whereas expression of the constitutively transactivated SRF fusion protein (SRF-VP16) was sufficient to induce SM-alpha-actin expression, suggesting that both expression and transactivation of SRF are important. Activation of protein kinase A (PKA) by forskolin or iloprost resulted in a significant inhibition of SM-alpha-actin expression induced by TGF-beta, and this was associated with inhibition of both SRF expression and activity, but not of Smad-mediated gene transcription. In summary, this is the first direct demonstration that TGF-beta-induced pulmonary myofibroblast differentiation is mediated by SRF, and that inhibition of myofibroblast differentiation by PKA occurs through down-regulation of SRF expression levels and SRF activity, independent of Smad signaling. |
| Authors | Nathan Sandbo, Steven Kregel, Sebastien Taurin, Sangeeta Bhorade, Nickolai O Dulin
(Affiliation: Section of Pulmonary and Critical Care Medicine, University of Chicago, 5841 S. Maryland Ave., MC 6076, Chicago, IL 60618, USA. nsandbo at medicine.bsd.uchicago.edu)
|
| Journal | American journal of respiratory cell and molecular biology
(Am J Respir Cell Mol Biol)
Vol. 41
Issue 3
Pg. 332-8
(Sep 2009)
ISSN: 1535-4989 [Electronic] United States |
| PMID | 19151320
(Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
|
| Chemical References |
- Actins
- RNA, Small Interfering
- Serum Response Factor
- Smad Proteins
- Transforming Growth Factor beta
- Cyclic AMP
- Cyclic AMP-Dependent Protein Kinases
|
| Topics |
- Actins
(genetics, metabolism)
- Animals
- Cell Differentiation
(drug effects, physiology)
- Cells, Cultured
- Cyclic AMP
(metabolism)
- Cyclic AMP-Dependent Protein Kinases
(metabolism)
- Fibroblasts
(cytology, drug effects, physiology)
- Gene Knockdown Techniques
- Humans
- Lung
(cytology)
- RNA, Small Interfering
(genetics, metabolism)
- Serum Response Factor
(metabolism)
- Smad Proteins
(genetics, metabolism)
- Transforming Growth Factor beta
(metabolism, pharmacology)
|
