Manifold active-state conformations in GPCRs: Agonist-activated constitutively active mutant AT1 receptor preferentially couples to Gq compared to the wild-type AT1 receptor

The angiotensin II type I (AT1) receptor mediates regulation of blood pressure and water-electrolyte balance by Ang II. Substitution of Gly for Asn111 of the AT1 receptor constitutively activates the receptor leading to Gq-coupled IP3 production independent of Ang II binding. The Ang II-activated conformation of the AT1N111G receptor was proposed to be similar to that of the wild-type AT1 receptor, although, various aspects of the Ang II-induced conformation of this constitutively active mutant receptor have not been systematically studied. Here, we provide evidence that the conformation of the active state of the wild-type and the constitutively active AT1 receptors are different. Upon Ang II binding an activated conformation of the wild-type AT1 receptor activates G protein and recruits β-arrestin. In contrast, the agonist-bound AT1N111G mutant receptor preferentially couples to Gq and is inadequate in β-arrestin recruitment.