This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Auger-Messier, M. Articles by Guillemette, G. Search for Related Content PubMed PubMed Citation Articles by Auger-Messier, M. Articles by Guillemette, G.

The Constitutively Active N111G-AT₁ Receptor for Angiotensin II Maintains a High Affinity Conformation Despite Being Uncoupled from Its Cognate G Protein G_q/11

Department of Pharmacology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Quebec, Canada J1H 5N4

Address all correspondence and requests for reprints to: Gaetan Guillemette, Ph.D., Department of Pharmacology, Faculty of Medicine, Université de Sherbrooke, 3001, 12th Avenue North, Sherbrooke, Quebec, Canada J1H 5N4. E-mail: Gaetan.Guillemette{at}USherbrooke.ca.

Asn111, localized in the third transmembrane domain of the AT₁ receptor for angiotensin II, plays a critical role in stabilizing the inactive conformation of the receptor. We evaluated the functional and G protein-coupling properties of mutant AT₁ receptors in which Asn111 was substituted with smaller (Ala or Gly) or larger residues (Gln or Trp). All four mutants were expressed at high levels in COS-7 cells and, except for N111W-AT₁, recognized ¹²⁵I-Ang II with high affinities comparable to that of the wild-type AT₁ receptor. In phospholipase C assays, the four mutants encompassed the entire spectrum of functional states, ranging from constitutive activity (without agonist) for N111A-AT₁ and N111G-AT₁ to a significant loss of activity (upon maximal stimulation) for N111Q-AT₁ and a major loss of activity for N111W-AT₁. In Ca²⁺ mobilization studies, N111W-AT₁ produced a weak Ca²⁺ transient and, unexpectedly, N111G-AT₁ also produced a Ca²⁺ transient that was much weaker than that of the wild-type AT₁. The agonist binding affinity of N111W-AT₁ was not modified in the presence of GTP S, suggesting that this receptor is not basally coupled to a G protein. GTP S did not modify the high agonist-binding affinity of N111G-AT₁ but abolished the coimmunoprecipitation of G_q/11 with this constitutively active mutant receptor. These results are a direct demonstration that the N111G-AT₁ receptor maintains a high affinity conformation despite being uncoupled from the G protein G_q/11.

This article has been cited by other articles:

				L. Oliveira, C. M. Costa-Neto, C. R. Nakaie, S. Schreier, S. I. Shimuta, and A. C. M. Paiva The Angiotensin II AT1 Receptor Structure-Activity Correlations in the Light of Rhodopsin Structure Physiol Rev, April 1, 2007; 87(2): 565 - 592. [Abstract] [Full Text] [PDF]

				A. M. Allen, J. K. Dosanjh, M. Erac, S. Dassanayake, R. D. Hannan, and W. G. Thomas Expression of Constitutively Active Angiotensin Receptors in the Rostral Ventrolateral Medulla Increases Blood Pressure Hypertension, June 1, 2006; 47(6): 1054 - 1061. [Abstract] [Full Text] [PDF]

				S. Billet, S. Bardin, R. Tacine, E. Clauser, and S. Conchon The AT1A receptor "gain-of-function" mutant N111S/{Delta}329 is both constitutively active and hyperreactive to angiotensin II Am J Physiol Endocrinol Metab, May 1, 2006; 290(5): E840 - E848. [Abstract] [Full Text] [PDF]

				M. Auger-Messier, G. Arguin, B. Chaloux, R. Leduc, E. Escher, and G. Guillemette Down-Regulation of Inositol 1,4,5-Trisphosphate Receptor in Cells Stably Expressing the Constitutively Active Angiotensin II N111G-AT1 Receptor Mol. Endocrinol., December 1, 2004; 18(12): 2967 - 2980. [Abstract] [Full Text] [PDF]