RT Journal Article
SR Electronic
T1 Side-Chain Substitutions within Angiotensin II Reveal Different Requirements for Signaling, Internalization, and Phosphorylation of Type 1A Angiotensin Receptors
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 768
OP 777
DO 10.1124/mol.61.4.768
VO 61
IS 4
A1 Alice C. Holloway
A1 Hongwei Qian
A1 Luisa Pipolo
A1 James Ziogas
A1 Shin-ichiro Miura
A1 Sadashiva Karnik
A1 Bridget R. Southwell
A1 Michael J. Lew
A1 Walter G. Thomas
YR 2002
UL http://molpharm.aspetjournals.org/content/61/4/768.abstract
AB Binding of the peptide hormone angiotensin II (AngII) to the type 1 (AT1A) receptor and the subsequent activation of phospholipase C-mediated signaling, involves specific determinants within the AngII peptide sequence. In contrast, the contribution of such determinants to AT1A receptor internalization, phosphorylation and activation of mitogen-activated protein kinase (MAPK) signaling is not known. In this study, the internalization of an enhanced green fluorescent protein-tagged AT1A receptor (AT1A-EGFP), in response to AngII and a series of substituted analogs, was visualized and quantified using confocal microscopy. AngII-stimulation resulted in a rapid, concentration-dependent internalization of the chimeric receptor, which was prevented by pretreatment with the nonpeptide AT1receptor antagonist EXP3174. Remarkably, AT1A receptor internalization was unaffected by substitution of AngII side chains, including single and double substitutions of Tyr4 and Phe8 that abolish phospholipase C signaling through the receptor. AngII-induced receptor phosphorylation was significantly inhibited by several substitutions at Phe8 as well as alanine replacement of Asp1. The activation of MAPK was only significantly inhibited by substitutions at position eight in the peptide and specific substitutions did not equally inhibit inositol phosphate production, receptor phosphorylation and MAPK activation. These results indicate that separate, yet overlapping, contacts made between the AngII peptide and the AT1A receptor select/induce distinct receptor conformations that preferentially affect particular receptor outcomes. The requirements for AT1A receptor internalization seem to be less stringent than receptor activation and signaling, suggesting an inherent bias toward receptor deactivation.