title: Molecular basis for subtype-specific desensitization of inhibitory adenosine receptors. Analysis of a chimeric A1-A3 adenosine receptor.
abstract: The differing effects of short-term agonist exposure on the two inhibitory adenosine receptor (AR) subtypes have been examined using Chinese hamster ovary cells stably expressing the hemagglutinin epitope-tagged human A1AR and rat A3AR. Under conditions in which exposure of transfected cells to 5 microM (-)-(R)-N6-(phenylisopropyl)adenosine resulted in the functional desensitization and phosphorylation of the A3AR, neither property was exhibited by the A1AR. However, a stably expressed chimeric A1-A3AR, termed A1CT3AR, in which the C-terminal domain of the A1AR distal to its predicted palmitoylation site was replaced by the corresponding region of the A3AR, was able to undergo functional desensitization and agonist-stimulated phosphorylation in a manner similar to that exhibited by the A3AR. Moreover, purified G-protein-coupled receptor kinases 2, 3, and 5 were each capable of enhancing the agonist-dependent phosphorylation of the A3AR and A1CT3AR in vitro. Taken together, these data demonstrate that the C-terminal domain of the A3AR distal to its predicted palmitoylation site is responsible for this receptor's ability to undergo a rapid agonist-dependent desensitization and are consistent with a model in which phosphorylation of the A3AR within this domain by one or more G-protein-coupled receptor kinases initiates the desensitization process.
authors.affiliation: Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: T M
authors.initials: TM
authors.lastname: Palmer
authors.forename: J L
authors.initials: JL
authors.lastname: Benovic
authors.forename: G L
authors.initials: GL
authors.lastname: Stiles
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D006224:Cricetinae; D000939:Epitopes; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry; D010748:Phosphopeptides / Q000737:chemistry; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D058906:Purinergic P1 Receptor Agonists; D011869:Radioligand Assay; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D018047:Receptors, Purinergic P1 / Q000737:chemistry / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000819:agonists / Q000737:chemistry / Q000378:metabolism; D016324:Sequence Tagged Sites; D014162:Transfection
chemical_list: D000939:Epitopes; D010169:Palmitic Acids; D010446:Peptide Fragments; D010748:Phosphopeptides; D058906:Purinergic P1 Receptor Agonists; D018047:Receptors, Purinergic P1; D011993:Recombinant Fusion Proteins; D005576:Colforsin; D019308:Palmitic Acid; D000255:Adenosine Triphosphate; D020794:Receptor Protein-Tyrosine Kinases; D019204:GTP-Binding Proteins; D000241:Adenosine