Abstract

The P2Y₁₄ receptor was initially identified as a G protein-coupled receptor activated by UDP-glucose and other nucleotide sugars. We have developed several cell lines that stably express the human P2Y₁₄ receptor, allowing facile examination of its coupling to native G_i family G proteins and their associated downstream signaling pathways (J Pharmacol Exp Ther 330:162–168, 2009). In the current study, we examined P2Y₁₄ receptor-dependent inhibition of cyclic AMP accumulation in human embryonic kidney (HEK) 293, C6 glioma, and Chinese hamster ovary (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, 33, 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, 132, and 72 nM) observed for UDP-glucose. UDP and UDP-glucose also stimulated extracellular signal-regulated kinase (ERK) 1/2 phosphorylation in P2Y₁₄ receptor-expressing HEK293 cells but not in wild-type HEK293 cells. A series of analogs 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 analogs 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.