Abstract
G protein-coupled P2Y receptors (P2Y-R) are activated by adenine and uracil nucleotides. The P2Y14 receptor (P2Y14-R) is activated by at least four naturally occurring UDP sugars, with UDP-glucose (UDP-Glc) being the most potent agonist. With the goal of identifying a competitive antagonist for the P2Y14-R, UDP was examined for antagonist activity in COS-7 cells transiently expressing the human P2Y14-R and a chimeric Gα protein that couples Gi-coupled receptors to stimulation of phosphoinositide hydrolysis. UDP antagonized the agonist action of UDP-Glc, and Schild analysis confirmed that the antagonism was competitive (pKB = 7.28). Uridine 5′-O-thiodiphosphate also antagonized the human P2Y14-R (hP2Y14-R) with an apparent affinity similar to that of UDP. In contrast, no antagonist activity was observed with ADP, CDP, or GDP, and other uracil analogs also failed to exhibit antagonist activity. The antagonist activity of UDP was not observed at other hP2Y-R. In contrast to its antagonist action at the hP2Y14-R, UDP was a potent agonist (EC50 = 0.35 μM) at the rat P2Y14-R. These results identify the first competitive antagonist of the P2Y14-R and demonstrate pharmacological differences between receptor orthologs.
Footnotes
-
This work was supported by National Institutes of Health Grants GM38213, P01-HL034322, and the National Institutes of Health Intramural Research Program of National Institute of Diabetes and Digestive and Kidney Diseases.
-
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
-
doi:10.1124/jpet.108.136309.
-
ABBREVIATIONS: P2Y-R, P2Y receptor; GPCR, G protein-coupled receptor; hP2Y14-R, human P2Y14-R; UDP-Glc, UDP glucose; P2Y14-R, P2Y14 receptor; UP3U, diuridine 5′,5′-triphosphate; UP4U, diuridine 5′,5′-tetraphosphate; UDPβS, uridine 5′-O-thiodiphosphate; ENPP1, ecto-nucleotide pyrophosphatase/phosphodiesterase-1; DMEM, Dulbecco's modified Eagle's medium; rP2Y14-R, rat homolog of the P2Y14-R.
- Received January 7, 2008.
- Accepted January 29, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|