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. (1st December 2016) - Sharifat, Narges
Abstract: 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.