Transforming growth factor β-mediated site-specific Smad linker region phosphorylation in vascular endothelial cells. (14th October 2014)

• Record Type: Journal Article
• Authors: Kamato, Danielle; Rostam, Muhamad Ashraf; Piva, Terence J; Babaahmadi Rezaei, Hossein; Getachew, Robel; Thach, Lyna; Bernard, Rebekah; Zheng, Wenhua; Little, Peter J; Osman, Narin
• Is Part Of: Journal of pharmacy and pharmacology. Volume 66:Number 12(2014:Dec.)
• Page Start: 1722
• Page End: 1733
• Publication Date: 2014-10-14
• Subjects: cell signalling -- serine/threonine kinase -- Smad linker region -- Smads -- transforming growth factor-β; Pharmacy -- Periodicals; Pharmacology -- Periodicals; 615.1
• DOI: 10.1111/jphp.12298
• Languages: English
• ISSNs: 0022-3573

Abstract

Abstract: 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.