Polymorphic deletion of three intracellular acidic residues of the alpha 2B-adrenergic receptor decreases G protein-coupled receptor kinase-mediated phosphorylation and desensitization.
A polymorphic variant of the human alpha(2B)-adrenergic receptor (alpha(2B)AR), which consists of a deletion of three glutamic acids (residues 301-303) in the third intracellular loop was found to be common in Caucasians (31%) and to a lesser extent in African-Americans (12%). The consequences of this deletion were assessed by expressing wild-type and the Del301-303 receptors in Chinese hamster ovary and COS cells. Ligand binding was not affected, although a small decrease in coupling efficiency to the inhibition of adenylyl cyclase was observed with the mutant. The deletion occurs within a stretch of acidic residues that is thought to establish the milieu for agonist-promoted phosphorylation and desensitization of the receptor by G protein-coupled receptor kinases (GRKs). Agonist-promoted phosphorylation studies carried out in cells coexpressing the alpha(2B)ARs and GRK2 revealed that the Del301-303 receptor displayed approximately 56% of wild-type phosphorylation. Furthermore, the depressed phosphorylation imposed by the deletion was found to result in a complete loss of short term agonist-promoted receptor desensitization. Thus the major phenotype of the Del301-303 alpha(2B)AR is one of impaired phosphorylation and desensitization by GRKs, and thus the polymorphisms renders the receptor incapable of modulation by this key mechanism of dynamic regulation.
Small
K M
KM
Department of Medicine, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA.
Brown
K M
KM
Forbes
S L
SL
Liggett
S B
SB
D000262:Adenylyl Cyclases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D019556:COS Cells; D006224:Cricetinae; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D015536:Down-Regulation; D005787:Gene Frequency; D008969:Molecular Sequence Data; D009638:Norepinephrine / Q000494:pharmacology; D010766:Phosphorylation; D011110:Polymorphism, Genetic; D018341:Receptors, Adrenergic, alpha-2 / Q000235:genetics* / Q000378:metabolism*; D017384:Sequence Deletion; D014162:Transfection; D051552:beta-Adrenergic Receptor Kinases
C547771:ADRA2B protein, human; D018341:Receptors, Adrenergic, alpha-2; D017868:Cyclic AMP-Dependent Protein Kinases; D051552:beta-Adrenergic Receptor Kinases; D000262:Adenylyl Cyclases; D009638:Norepinephrine