RT Journal Article
SR Electronic
T1 Molecular Mechanism for Agonist-Promoted α<sub>2A</sub>-Adrenoceptor Activation by Norepinephrine and Epinephrine
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 1343
OP 1354
DO 10.1124/mol.59.5.1343
VO 59
IS 5
A1 Tommi Nyrönen
A1 Marjo Pihlavisto
A1 Juha M. Peltonen
A1 Anna-Marja Hoffrén
A1 Minna Varis
A1 Tiina Salminen
A1 Siegfried Wurster
A1 Anne Marjamäki
A1 Liisa Kanerva
A1 Erja Katainen
A1 Leif Laaksonen
A1 Juha-Matti Savola
A1 Mika Scheinin
A1 Mark S. Johnson
YR 2001
UL http://molpharm.aspetjournals.org/content/59/5/1343.abstract
AB We present a mechanism for agonist-promoted α2A-adrenergic receptor (α2A-AR) activation based on structural, pharmacological, and theoretical evidence of the interactions between phenethylamine ligands and α2A-AR. In this study, we have: 1) isolated enantiomerically pure phenethylamines that differ both in their chirality about the β-carbon, and in the presence/absence of one or more hydroxyl groups: the β-OH and the catecholic meta- andpara-OH groups; 2) used [3H]UK-14,304 [5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine; agonist] and [3H]RX821002 [2-(2-methoxy-1,4-benzodioxan-2-yl)-2-imidazoline; antagonist] competition binding assays to determine binding affinities of these ligands to the high- and low-affinity forms of α2A-AR; 3) tested the ability of the ligands to promote receptor activation by measuring agonist-induced stimulation of [35S]GTPγS binding in isolated cell membranes; and 4) used automated docking methods and our α2A-AR model to predict the binding modes of the ligands inside the α2A-AR binding site. The ligand molecules are sequentially missing different functional groups, and we have correlated the structural features of the ligands and ligand-receptor interactions with experimental ligand binding and receptor activation data. Based on the analysis, we show that structural rearrangements in transmembrane helix (TM) 5 could take place upon binding and subsequent activation of α2A-AR by phenethylamine agonists. We suggest that the following residues are important in phenethylamine interactions with α2A-AR: Asp113 (D3.32), Val114 (V3.33), and Thr118 (T3.37) in TM3; Ser200 (S5.42), Cys201 (C5.43), and Ser204 (S5.46) in TM5; Phe391 (F6.52) and Tyr394 (Y6.55) in TM6; and Phe411 (F7.38) and Phe412 (F7.39) in TM7.