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p38 mitogen-activated protein kinase is required for TGFbeta-mediated fibroblastic transdifferentiation and cell
Andrei V Bakin1, Cammie Rinehart, Anne K Tomlinson
1Department of Medicine, Vanderbilt University School of Medicine, 777 Preston Research Building, Nashville, TN 37232, USA.
Abstract:
Transforming growth factor beta (TGFbeta) contributes to tumor progression by inducing an epithelial to mesenchymal transdifferentiation (EMT) and cell migration. We found that TGFbeta-induced EMT was blocked by inhibiting activation of p38 mitogen-activated protein kinase (MAPK) with H-7, a protein kinase C inhibitor, and with SB202190, a direct inhibitor of p38MAPK. Inhibition of the p38MAPK pathway affected TGFbeta-mediated phosphorylation of ATF2, but did not inhibit phosphorylation of Smad2. SB202190 impaired TGFbeta-mediated changes in cell shape and reorganization of the actin cytoskeleton. Forced expression of dominant-negative (DN) MAPK kinase 3 (MKK3) inhibited TGFbeta-mediated activation of p38MAPK and EMT. Expression of DN-p38alpha impaired TGFbeta-induced EMT. Inhibition of p38MAPK blocked TGFbeta-induced migration of non-tumor and tumor mammary epithelial cells. TGFbeta induced activation of the p38MAPK pathway within 15 minutes. Expression of TGFbeta type II (TbetaRII) and type I (TbetaRI/Alk5) kinase-inactive receptors blocked EMT and activation of p38MAPK, whereas expression of constitutively active Alk5-T204D resulted in EMT and phosphorylation of MKK3/6 and p38MAPK. Finally, dominant-negative Rac1N17 blocked TGFbeta-induced activation of the p38MAPK pathway and EMT, suggesting that Rac1 mediates activation of the p38MAPK pathway. These studies suggest that the p38MAPK pathway is required for TGFbeta-mediated EMT and cell migration.
Insights
Transforming growth factor beta (TGFbeta) drives tumor progression via epithelial to mesenchymal transdifferentiation (EMT) and cell migration. Inhibiting the p38 mitogen-activated protein kinase (MAPK) pathway blocks these TGFbeta-induced effects, highlighting its crucial role.
Area of Science:
- Cell Biology
- Molecular Biology
- Cancer Research
Background:
- Transforming growth factor beta (TGFbeta) is a key regulator of tumor progression.
- TGFbeta induces epithelial to mesenchymal transdifferentiation (EMT) and cell migration, processes critical for metastasis.
- The precise molecular pathways mediating TGFbeta's effects on EMT and migration are under investigation.
Purpose of the Study:
- To investigate the role of the p38 mitogen-activated protein kinase (MAPK) pathway in TGFbeta-induced EMT and cell migration.
- To identify key signaling molecules upstream and downstream of p38MAPK involved in these processes.
- To explore the potential of targeting the p38MAPK pathway for therapeutic intervention in cancer.
Main Methods:
- Utilized pharmacological inhibitors (H-7, SB202190) to block p38MAPK activation.
- Employed dominant-negative constructs (DN-MKK3, DN-p38alpha, Rac1N17) to dissect pathway components.
- Assessed TGFbeta-mediated changes in cell morphology, actin cytoskeleton, and cell migration.
- Investigated the role of TGFbeta receptors (TbetaRII, TbetaRI/Alk5) in pathway activation.
Main Results:
- Inhibition of p38MAPK activation blocked TGFbeta-induced EMT, cell shape changes, and actin reorganization.
- p38MAPK inhibition affected ATF2 phosphorylation but not Smad2 phosphorylation.
- Dominant-negative MKK3 and p38alpha impaired TGFbeta-induced EMT.
- TGFbeta rapidly activated the p38MAPK pathway.
- Expression of dominant-negative Rac1N17 blocked TGFbeta-induced p38MAPK activation and EMT.
- Kinase-inactive TGFbeta receptors blocked EMT and p38MAPK activation, while constitutively active Alk5 induced EMT and pathway activation.
Conclusions:
- The p38MAPK pathway is essential for TGFbeta-mediated EMT and cell migration.
- Rac1 acts upstream of p38MAPK in mediating TGFbeta signaling.
- These findings identify the p38MAPK pathway as a critical mediator of TGFbeta's pro-tumorigenic effects.