Faculty Collaboration Database

Sites in the third intracellular loop of the alpha 2A-adrenergic receptor confer short term agonist-promoted desensitization. Evidence for a receptor kinase-mediated mechanism. J Biol Chem 1992 Mar 05;267(7):4740-6

Date

03/05/1992

Pubmed ID

1311318

Scopus ID

2-s2.0-0026756371 (requires institutional sign-in at Scopus site)   127 Citations

Abstract

To investigate the mechanisms of agonist-promoted desensitization of the alpha 2-adrenergic receptor (alpha 2AR), the human alpha 2AAR and a mutated form of the receptor were expressed in CHW cells. After cells were exposed to epinephrine for 30 min, the ability of the wild type alpha 2AAR to mediate inhibition of forskolin-stimulated adenylyl cyclase was depressed by approximately 78%. To assess the role of receptor phosphorylation during desensitization, cells were incubated with 32Pi, exposed to agonist, and alpha 2AAR purified by immunoprecipitation with a fusion protein antibody. Agonist-promoted desensitization was found to be accompanied by phosphorylation of the alpha 2AAR in vivo. The beta-adrenergic receptor kinase (beta ARK) is known to phosphorylate purified alpha 2AAR in vitro. We found that heparin, a beta ARK inhibitor, ablated short term agonist-induced desensitization of alpha 2AAR, while such desensitization was unaffected by inhibition of protein kinase A. To further assess the role of beta ARK, we constructed a mutated alpha 2AAR which has a portion of the third intracellular loop containing 9 serines and threonines (potential phosphorylation sites) deleted. This mutated alpha 2AAR failed to undergo short term agonist-induced desensitization. Agonist promoted in vivo phosphorylation of this mutated receptor was reduced by 90%, consistent with the notion that receptor phosphorylation at sites in the third intracellular loop plays a critical role in alpha 2AAR desensitization. After 24 h of agonist exposure, an even more profound desensitization of alpha 2AAR occurred, which was not accompanied by a decrease in receptor expression. Rather, long term agonist-induced desensitization was found to be due in part to a decrease in the amount of cellular Gi, which was not dependent on receptor third loop phosphorylation sites.

Author List

Liggett SB, Ostrowski J, Chesnut LC, Kurose H, Raymond JR, Caron MG, Lefkowitz RJ

Author

John R. Raymond MD President, CEO, Professor in the President department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Adenosine Diphosphate Ribose
Adenylate Cyclase Toxin
Adenylyl Cyclase Inhibitors
Adenylyl Cyclases
Amino Acid Sequence
Animals
Blotting, Western
Colforsin
Cricetinae
Cricetulus
Cyclic AMP-Dependent Protein Kinases
Electrophoresis, Polyacrylamide Gel
Epinephrine
Fibroblasts
GTP-Binding Proteins
Humans
Molecular Sequence Data
Phosphorylation
Protein Conformation
Protein Kinase Inhibitors
Protein Kinases
Radioligand Assay
Receptors, Adrenergic, alpha
Transfection
Virulence Factors, Bordetella
beta-Adrenergic Receptor Kinases