RT Journal Article
SR Electronic
T1 Constitutive activation of a single effector pathway: evidence for multiple activation states of a G protein-coupled receptor.
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 112
OP 122
VO 49
IS 1
A1 Perez, D M
A1 Hwa, J
A1 Gaivin, R
A1 Mathur, M
A1 Brown, F
A1 Graham, R M
YR 1996
UL http://molpharm.aspetjournals.org/content/49/1/112.abstract
AB A cysteine-to-phenylalanine mutation in the third transmembrane domain of the alpha 1B-adrenergic receptor constitutively activates the receptor, resulting in G protein coupling in the absence of agonist and activation of only a single effector pathway (phospholipase C but not phospholipase A2). This mutant receptor displays a higher affinity for the catecholamines, norepinephrine, and epinephrine, as well as for other phenethylamines, but not for imidazolines, a class of structurally distinct alpha agonists. Dose-response studies demonstrate a higher potency and intrinsic activity of phenethylamines for polyphosphoinositide turnover but not for arachidonic acid release. Imidazolines have wild-type potencies and intrinsic activities for both pathways. These data indicate that a single receptor subtype forms multiple conformations (i.e., exhibits induced conformational pleiotropy) for G protein interactions (high affinity states) that are specific for a particular G protein/effector pathway and that multiple binding sites exist for agonists, which promote or induce these specific interactions. Pharmacological diversity may, thus, be achieved through a single receptor by the development of compounds that induce a single activated conformer. This has major ramifications for the eventual development of signaling-specific therapeutics.