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 (Tβ RI ). 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 Tβ RI in bovine aortic endothelial cells ( BAEC s). Method The in‐vitro model used BAEC s. Signalling intermediate phospho‐Smad2 in the carboxy terminal was detected and quantified by Western blotting. Key finding ET‐1 treatment of BAEC s resulted in a time and concentration‐dependent increase in pS mad2C. Peak phosphorylation was evident with 100 n m treatment of ET ‐1 at 4–6 h. Tβ RI antagonist, SB 431542 inhibited ET ‐1‐mediated pS mad2C. In the presence of bosentan, a mixed ET A and ET B receptor antagonist ET ‐1‐mediated pS mad2C levels were inhibited. The ET ‐mediated pS mad2C was blocked by the protein synthesis inhibitor, cycloheximide. Conclusion In BAECs, ET‐1 via the ETB receptor is involved in transactivation of the Tβ RI . The transactivation‐dependent response is dependent upon de novo protein synthesis.