G protein- and β-arrestin Signaling Profiles of Endothelin Derivatives at the Type A Endothelin Receptor

Endothelin-1 (ET-1) is a potent vasoconstrictor in the cardiovascular system, an effect mediated through the type A endothelin receptor (ETAR), a G protein-coupled receptor (GPCR). Antagonists of the ETAR have shown promising

Our findings are consistent with vasoconstriction being mediated by G proteins with a lack of significant desensitization by β-arrestins at the ETAR. These findings suggest that G protein- and β-arrestin-biased ETAR agonists could have distinct physiologic effects from balanced agonists, although the endothelin peptide scaffold does not appear suitable for designing such ligands.

A panel of endothelin derivatives were tested in assays of G protein signaling and β-arrestin 2 recruitment at the ETAR. We then tested the effects of ET-1 on the vasopressor response in wild-type and β-arrestin 1 and 2 KO mice.

We found the endothelins activated a wide range of G proteins at the ETAR, but none of the endothelin derivatives demonstrated significant biased agonism. Endothelin derivatives did display structure-activity relationships with regards to their degrees of agonism. β-arrestin 1 and 2 knockout mice did not display any differences to wild-type mice in the acute pressor response to ET-1, and β-arrestin 2 knockout mice did not display any blood pressure differences to wild-type mice in the chronic responses to ET-1. Conclusions: Our findings are consistent with vasoconstriction being mediated by G proteins with a lack of significant desensitization by β-arrestins at the ETAR. These findings suggest that G protein- and β-arrestin-biased ETAR agonists could have distinct physiologic effects from balanced agonists, although the endothelin peptide scaffold does not appear suitable for designing such ligands.