Endothelin-1 (ET-1) stimulates carboxy terminal Smad2 phosphorylation in vascular endothelial cells by a mechanism dependent on ET receptors and de novo protein synthesis.
OBJECTIVE
G protein-coupled receptor (GPCR) agonists through their receptors can transactivate protein tyrosine kinase receptors such as epidermal growth factor receptor and serine/threonine kinase receptors most notably transforming growth factor (TGF)-β receptor (TβRI). This signalling mechanism represents a major expansion in the cellular outcomes attributable to GPCR signalling. This study addressed the role and mechanisms involved in GPCR agonist, endothelin-1 (ET-1)-mediated transactivation of the TβRI in bovine aortic endothelial cells (BAECs).


METHOD
The in-vitro model used BAECs. Signalling intermediate phospho-Smad2 in the carboxy terminal was detected and quantified by Western blotting.


KEY FINDING
ET-1 treatment of BAECs resulted in a time and concentration-dependent increase in pSmad2C. Peak phosphorylation was evident with 100 nm treatment of ET-1 at 4-6 h. TβRI antagonist, SB431542 inhibited ET-1-mediated pSmad2C. In the presence of bosentan, a mixed ETA and ETB receptor antagonist ET-1-mediated pSmad2C levels were inhibited. The ET-mediated pSmad2C was blocked by the protein synthesis inhibitor, cycloheximide.


CONCLUSION
In BAECs, ET-1 via the ETB receptor is involved in transactivation of the TβRI. The transactivation-dependent response is dependent upon de novo protein synthesis.
['Sharifat|Narges|N|', 'Mohammad Zadeh|Ghorban|G|', 'Ghaffari|Mohammad-Ali|MA|', 'Dayati|Parisa|P|', 'Kamato|Danielle|D|', 'Little|Peter J|PJ|', 'Babaahmadi-Rezaei|Hossein|H|']
D000818:Animals D001549:Benzamides D000077300:Bosentan D002417:Cattle D003513:Cycloheximide D004149:Dioxoles D042783:Endothelial Cells D065128:Endothelin Receptor Antagonists D019332:Endothelin-1 D004730:Endothelium, Vascular D004791:Enzyme Inhibitors D010766:Phosphorylation D014176:Protein Biosynthesis D011500:Protein Synthesis Inhibitors D044023:Receptor, Endothelin B D018125:Receptors, Transforming Growth Factor beta D015398:Signal Transduction D051899:Smad2 Protein D013449:Sulfonamides D016212:Transforming Growth Factor beta
endothelin-1 transactivation atherosclerosis phosphorylated Smad2 transforming growth factor-β