Transforming growth factor β-mediated site-specific Smad linker region phosphorylation in vascular endothelial cells
Objectives Transforming growth factor (TGF)-β regulates the function of vascular endothelial cells and may be involved in endothelial dysfunction. The canonical TGF-β pathway involves TGF-β receptor-mediated carboxy-terminal phosphorylation of Smad2; however, TGF-β signalling also activates numer...
| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Wiley
2014
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| Subjects: | |
| Online Access: | http://irep.iium.edu.my/55283/ http://irep.iium.edu.my/55283/ http://irep.iium.edu.my/55283/ http://irep.iium.edu.my/55283/1/5.%20Kamato-2014-Transforming%20growth%20factor%20%CE%B2-media.pdf |
| Summary: | Objectives Transforming growth factor (TGF)-β regulates the function of vascular
endothelial cells and may be involved in endothelial dysfunction. The canonical
TGF-β pathway involves TGF-β receptor-mediated carboxy-terminal
phosphorylation of Smad2; however, TGF-β signalling also activates numerous
serine/threonine kinases that phosphorylate Smad2 in its linker region. The
expression of phosphorylated Smad linker proteins were determined following
TGF-β stimulation in the absence and presence of different serine/threonine
kinase inhibitors in vascular endothelial cells.
Methods Proteins were quantified by Western blotting using specific antibodies
to individual phosphorylated Smad2 linker region residues.
Key findings TGF-β mediated the phosphorylation of all four Smad2 linker
region residues of interest. Erk and Jnk specifically phosphorylate Ser245 while all
mitogen-activated protein kinases phosphorylate Ser250 and Ser255. Thr220 and
Ser245 are phosphorylated by phosphoinositide 3 kinase (PI3K), while Ser255 was
phosphorylated by the PI3K/Akt pathway. CDK and GSK-3 were shown to phosphorylate
Thr220 and Ser245. TGF-β also mediated plasminogen activator
inhibitor-1 gene expression that was attenuated by p38 and CDK inhibitors.
Conclusions TGF-β-mediated phosphorylation of individual serine/threonine
sites in the linker region of Smad2 occurs in a highly specific manner by kinases.
These phosphorylations provide an opportunity to further understand
a therapeutically targeted and very specific signalling pathway in vascular
endothelial cells. |
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