title: Critical hydrogen bond formation for activation of the angiotensin II type 1 receptor.
abstract: G protein-coupled receptors contain selectively important residues that play central roles in the conformational changes that occur during receptor activation. Asparagine 111 (N111(3.35)) is such a residue within the angiotensin II type 1 (AT(1)) receptor. Substitution of N111(3.35) for glycine leads to a constitutively active receptor, whereas substitution for tryptophan leads to an inactivable receptor. Here, we analyzed the AT(1) receptor and two mutants (N111G and N111W) by molecular dynamics simulations, which revealed a novel molecular switch involving the strictly conserved residue D74(2.50). Indeed, D74(2.50) forms a stable hydrogen bond (H-bond) with the residue in position 111(3.35) in the wild-type and the inactivable receptor. However, in the constitutively active mutant N111G-AT(1) receptor, residue D74 is reoriented to form a new H-bond with another strictly conserved residue, N46(1.50). When expressed in HEK293 cells, the mutant N46G-AT(1) receptor was poorly activable, although it retained a high binding affinity. Interestingly, the mutant N46G/N111G-AT(1) receptor was also inactivable. Molecular dynamics simulations also revealed the presence of a cluster of hydrophobic residues from transmembrane domains 2, 3, and 7 that appears to stabilize the inactive form of the receptor. Whereas this hydrophobic cluster and the H-bond between D74(2.50) and W111(3.35) are more stable in the inactivable N111W-AT(1) receptor, the mutant N111W/F77A-AT(1) receptor, designed to weaken the hydrophobic core, showed significant agonist-induced signaling. These results support the potential for the formation of an H-bond between residues D74(2.50) and N46(1.50) in the activation of the AT(1) receptor.
authors.affiliation: Department of Pharmacology, Faculty of Medicine and Health Sciences, Institut de Pharmacologie de Sherbrooke, Université de Sherbrooke, Sherbrooke, Quecec J1H 5N4, Canada.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Cabana
authors.forename: Brian
authors.initials: B
authors.lastname: Holleran
authors.forename: Marie-Ève
authors.initials: MÈ
authors.lastname: Beaulieu
authors.forename: Richard
authors.initials: R
authors.lastname: Leduc
authors.forename: Emanuel
authors.initials: E
authors.lastname: Escher
authors.forename: Gaétan
authors.initials: G
authors.lastname: Guillemette
authors.forename: Pierre
authors.initials: P
authors.lastname: Lavigne
mesh_terms: D003198:Computer Simulation; D017124:Conserved Sequence; D004305:Dose-Response Relationship, Drug; D057809:HEK293 Cells; D006801:Humans; D006860:Hydrogen Bonding; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D044140:Receptor, Angiotensin, Type 1 / Q000737:chemistry* / Q000378:metabolism; D019718:Receptors, CXCR4 / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled; D017473:Receptors, Opioid, kappa / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: C527276:CXCR4 protein, human; D044140:Receptor, Angiotensin, Type 1; D019718:Receptors, CXCR4; D043562:Receptors, G-Protein-Coupled; D017473:Receptors, Opioid, kappa