PT  - JOURNAL ARTICLE
AU  - Perez, D M
AU  - Hwa, J
AU  - Gaivin, R
AU  - Mathur, M
AU  - Brown, F
AU  - Graham, R M
TI  - Constitutive activation of a single effector pathway: evidence for multiple activation states of a G protein-coupled receptor.
DP  - 1996 Jan 01
TA  - Molecular Pharmacology
PG  - 112--122
VI  - 49
IP  - 1
4099  - http://molpharm.aspetjournals.org/content/49/1/112.short
4100  - http://molpharm.aspetjournals.org/content/49/1/112.full
SO  - Mol Pharmacol1996 Jan 01; 49
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.