TY - JOUR T1 - Mutational Analysis of the Conserved Asp<sup>2.50</sup> and ERY Motif Reveals Signaling Bias of the Urotensin II Receptor JF - Molecular Pharmacology JO - Mol Pharmacol SP - 552 LP - 561 DO - 10.1124/mol.108.045054 VL - 74 IS - 3 AU - Christophe D. Proulx AU - Brian J. Holleran AU - Antony A. Boucard AU - Emanuel Escher AU - Gaétan Guillemette AU - Richard Leduc Y1 - 2008/09/01 UR - http://molpharm.aspetjournals.org/content/74/3/552.abstract N2 - Class A (rhodopsin-like) G protein-coupled receptors possess conserved residues and motifs that are important for their specific activity. In the present study, we examined the role of residue Asp972.50 as well as residues Glu1473.49, Arg1483.50, and Tyr1493.51 of the ERY motif on the functionality of the urotensin II receptor (UT). Mutations D972.50A, R1483.50A, and R1483.50H abolished the ability of UT to activate phospholipase C, whereas mutations E1473.49A and Y1493.51A reduced the ability to activate PLC by 50%. None of the mutants exhibited constitutive activity. However, R1483.50A and R1483.50H promoted ERK1/2 activation, which was abolished by 4-(3-chloroanilino)-6,7-dimethoxyquinazoline (AG1478), an inhibitor of epidermal growth factor receptor (EGFR) tyrosine kinase activity. Both these mutants were capable of directly activating EGFR, which confirmed that they activated the mitogen-activated protein kinase (MAPK) pathway by a Gαq/11-independent transactivation of EGFR. The D972.50A, R1483.50A, and R1483.50H mutants did not readily internalize and did not promote translocation or colocalize with β-arrestin2-GFP. Finally, the agonist-induced internalization of the E1473.49A mutant receptor was significantly increased compared with wild-type receptor. This study highlights the major contribution of the conserved Asp2.50 residue to the functionality of the UT receptor. The Arg residue in the ERY motif of UT is an important structural element in signaling crossroads that determine whether Gαq/11-dependent and -independent events can occur. ER -