Abstract
The P2Y14 receptor was initially identified as a G protein-coupled receptor activated by UDP-glucose and other nucleotide-sugars. We recently developed several cell lines that stably express the human P2Y14 receptor, allowing facile examination of its coupling to native Gi family G proteins and their associated downstream signaling pathways (Fricks et al., J. Pharmacol. Exp. Ther., 2009). Here we examined P2Y14 receptor-dependent inhibition of cyclic AMP accumulation in HEK293, C6 glioma, and CHO cells stably expressing this receptor. Not only was the human P2Y14 receptor activated by UDP-glucose, but it also was activated by UDP. The apparent efficacies of UDP and UDP-glucose were similar, and the EC50 values (74 nM, 33 nM, and 29 nM) for UDP-dependent activation of the P2Y14 receptor in HEK293, CHO and C6 glioma cells, respectively, were similar to the EC50 values (323 nM, 132 nM, and 72 nM) observed for UDP-glucose. UDP and UDP-glucose also stimulated ERK1/2 phosphorylation in P2Y14 receptor-expressing HEK293 cells but not in wild-type HEK293 cells. A series of analogues of UDP were potent P2Y14 receptor agonists, but the naturally occurring nucleoside diphosphates, CDP, GDP, and ADP exhibited agonist potencies over 100-fold less than that observed with UDP. Two UDP analogues were identified that selectively activate the P2Y14 receptor over the UDP-activated P2Y6 receptor, and these molecules stimulated phosphorylation of ERK1/2 in differentiated human HL-60 promyeloleukemia cells, which natively express the P2Y14 receptor, but had no effect in wild-type HL-60 cells, which do not express the receptor. We conclude that UDP is an important cognate agonist of the human P2Y14 receptor.
Footnotes
- Received June 12, 2009.
- Revision received August 28, 2009.
- Accepted September 16, 2009.
- The American Society for Pharmacology and Experimental Therapeutics