PT  - JOURNAL ARTICLE
AU  - Mhaouty-Kodja, Sakina
AU  - Barak, Larry S.
AU  - Scheer, Alexander
AU  - Abuin, Liliane
AU  - Diviani, Dario
AU  - Caron, Marc G.
AU  - Cotecchia, Susanna
TI  - Constitutively Active <em>Alpha</em>-1b Adrenergic Receptor Mutants Display Different Phosphorylation and Internalization Features
AID  - 10.1124/mol.55.2.339
DP  - 1999 Feb 01
TA  - Molecular Pharmacology
PG  - 339--347
VI  - 55
IP  - 2
4099  - http://molpharm.aspetjournals.org/content/55/2/339.short
4100  - http://molpharm.aspetjournals.org/content/55/2/339.full
SO  - Mol Pharmacol1999 Feb 01; 55
AB  - We compared the phosphorylation and internalization properties of constitutively active alpha-1b adrenergic receptor (AR) mutants carrying mutations in two distant receptor domains, i.e., at A293 in the distal part of the third intracellular loop and at D142 of the DRY motif lying at the end of the third transmembrane domain. For the A293E and A293I mutants the levels of agonist-independent phosphorylation were 150% and 50% higher than those of the wild-type alpha-1b AR, respectively. On the other hand, for the constitutively active D142A and D142T mutants, the basal levels of phosphorylation were similar to those of the wild-typealpha-1b AR and did not appear to be further stimulated by epinephrine. Overexpression of the guanyl nucleotide binding regulatory protein-coupled receptor kinase GRK2 further increases the basal phosphorylation of the A293E mutant, but not that of D142A mutant. Both the wild-type alpha-1b AR and the A293E mutant could undergo β-arrestin-mediated internalization. The epinephrine-induced internalization of the constitutively active A293E mutant was significantly higher than that of the wild-typealpha-1b AR. In contrast, the D142A mutant was impaired in its ability to interact with β-arrestin and to undergo agonist-induced internalization. Interestingly, a double mutant A293E/D142A retained very high constitutive activity and regulatory properties of both the A293E and D142A receptors. These findings demonstrate that two constitutively activating mutations occurring in distant receptor domains of the alpha-1b AR have divergent effects on the regulatory properties of the receptor.