UDP Is a Competitive Antagonist at the Human P2Y₁₄Receptor

Abstract

G protein-coupled P2Y receptors (P2Y-R) are activated by adenine and uracil nucleotides. The P2Y 14 receptor (P2Y 14 -R) is activated by at least four naturally occurring UDP sugars, with UDPglucose (UDP-Glc) being the most potent agonist. With the goal of identifying a competitive antagonist for the P2Y 14 -R, UDP was examined for antagonist activity in COS-7 cells transiently expressing the human P2Y 14 -R and a chimeric G␣ 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 (pK B ϭ 7.28). Uridine 5Ј-O-thiodiphosphate also antagonized the human P2Y 14 -R (hP2Y 14 -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 hP2Y 14 -R, UDP was a potent agonist (EC 50 ϭ 0.35 M) at the rat P2Y 14 -R. These results identify the first competitive antagonist of the P2Y 14 -R and demonstrate pharmacological differences between receptor orthologs.

The nucleotide sugar UDP-glucose mobilizes long-term repopulating primitive hematopoietic cells

“…It was previously shown that UDP antagonizes the action of UDP-Glc (44). We therefore evaluated the effects of UDP on UDPGlc-mediated HSPCs migration.…”

UDP-Sugars as Extracellular Signaling Molecules: Cellular and Physiologic Consequences of P2Y14 Receptor Activation

“…UDP-N-acetylglucosamine, and all these molecules exhibited potencies in the 0.1-1.0 mM range of concentrations. One potential caveat from this and additional early studies was that they were accomplished using overexpressed G-protein a-subunits, either with Ga 16 , which mediates coupling of essentially all GPCR to phospholipase C-b isozymes, or with the engineered protein, Ga q/i , which selectively couples G i -linked GPCR to activation of phospholipase C-b (Chambers et al, 2000;Freeman et al, 2001;Lazarowski et al, 2003;Fricks et al, 2008). Nonetheless, results from work studying the agonist selectivity of the P2Y 14 R in cell systems in which it coupled through native G i heterotrimers to promote inhibition of adenylyl cyclase confirmed the nucleotide sugar selectivity established by Chambers and coworkers; that is, UDP-glucose is the most potent agonist, but the activities of other nucleotide sugars are within an order of magnitude .…”

Discovery of Novel P2Y14 Agonist and Antagonist Using Conventional and Nonconventional Methods

“…Fricks et al 7 demonstrated that udp behaves as a competitive antagonist of human but a full agonist of rat p2yr14. our data illustrating that udp behaves as a full agonist of chimpanzee and mouse p2y14 are consistent with Fricks' rat p2y14 data; however, we have been unable to demonstrate udpmediated antagonism of human p2y14.…”

“…3,5,6,7,11 cellular dielectric impedance measurements can generate unique response profiles that are characteristic of the specific G-protein coupling of the activated receptor. 10 We have used this technology to illustrate that udp-Glc, ump, and udp stimulation of HeK cells expressing p2y14 and Gα qi5 resulted in the expected characteristic early, small, and rapid decrease followed by an increase in Ziec, typical of activation of Gα q -coupled receptors ( Fig.…”

“…other sugar nucleotides such as adp-glucose, naturally occurring nucleotides (ump, udp, and utp), and nucleosides (uridine) were unable to activate p2y14. in 2008, Fricks et al 7 reported that udp was a competitive antagonist of human p2y14 but a potent agonist of the rat receptor, and recently, carter et al 5 illustrated that udp was a potent agonist of human p2y14.…”