This Article Full Text Full Text (PDF) All Versions of this Article: 20/8/1924    most recent Author Manuscript (PDF) Purchase Article View Shopping Cart 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 Yee, D. K. Articles by Fluharty, S. J. Search for Related Content PubMed PubMed Citation Articles by Yee, D. K. Articles by Fluharty, S. J.

Identification of Structural Determinants for G Protein-Independent Activation of Mitogen-Activated Protein Kinases in the Seventh Transmembrane Domain of the Angiotensin II Type 1 Receptor

Department of Animal Biology (D.K.Y., A.S., L.L., S.J.F.) and the Institute of Neurological Sciences (S.J.F.), University of Pennsylvania, Philadelphia, Pennsylvania 19104-6046

Address all correspondence and requests for reprints to: Daniel K. Yee, Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, 222E, Philadelphia, Pennsylvania 19104-6046. E-mail: dkyee{at}vet.upenn.edu.

Although the intrareceptor mechanisms whereby the angiotensin II (AngII) type 1 receptor activates phospholipase C (PLC) have been extensively investigated, analogous studies of signaling through mitogen-activated protein kinases (MAPK) have been lacking. We investigated MAPK activation and traditional G_q/PLC signaling in transfected cells using AngII and the signaling selective agonist [Sar¹,Ile⁴,Ile⁸] AngII (SII). SII stimulated MAPK without inositol trisphosphate (IP₃) production and thereby stabilizes an activated receptor state linked to G protein-independent MAPK signaling. Using receptor mutagenesis, we focused on the seventh transmembrane domain and identified three key residues—Tyr²⁹², Phe²⁹³, and Thr²⁸⁷. At least three distinct activated states were revealed: 1) an AngII-stabilized state linked to G_q/PLC signaling, 2) an AngII-stabilized state connected to G protein-independent MAPK activation, and 3) a SII-stabilized state associated with G protein-independent MAPK signaling. The mutant Y292F failed to exhibit AngII-induced IP₃ turnover yet remained capable of AngII-induced MAPK activation. SII failed to stimulate MAPK in Y292F-transfected cells. Thus, Tyr²⁹² is a key epitope for activated states 1 and 3 but not required for activated state 2. Although the F293L mutant retained normal AngII responses, it also showed an IP₃ response to SII, indicating that Phe²⁹³ may be involved in constraining the receptor to its inactive state. Mutations of Thr²⁸⁷ abolished all SII-induced signaling without affecting any AngII responses. Thr²⁸⁷ therefore represents a key residue for a SII-stabilized activated state. Taken together, the data identified a novel structural requirement (Thr²⁸⁷) for the SII-stabilized activated state and redefined the mechanistic roles for Tyr²⁹² and Phe²⁹³.

This article has been cited by other articles:

				S. M. DeWire, J. Kim, E. J. Whalen, S. Ahn, M. Chen, and R. J. Lefkowitz {beta}-Arrestin-mediated Signaling Regulates Protein Synthesis J. Biol. Chem., April 18, 2008; 283(16): 10611 - 10620. [Abstract] [Full Text] [PDF]

				M. Kang, K. Y. Chung, and J. W. Walker G-Protein Coupled Receptor Signaling in Myocardium: Not for the Faint of Heart Physiology, June 1, 2007; 22(3): 174 - 184. [Abstract] [Full Text] [PDF]

				D. Daniels, D. K. Yee, and S. J. Fluharty Hydromineral Neuroendocrinology: Angiotensin II receptor signalling Exp Physiol, May 1, 2007; 92(3): 523 - 527. [Abstract] [Full Text] [PDF]