P2-pyrimidinergic receptors and their ligands.

Pyrimidine nucleotides, including UTP, UDP and UDP-glucose, are important signaling molecules which activate G protein-coupled membrane receptors of the P2Y family. Four distinct pyrimidine nucleotide-sensitive P2Y receptor subtypes have been cloned, P2Y(2), P2Y(4), P2Y(6) and P2Y(14). Pharmacological experiments indicate that further subtypes may exist. P2Y(2) and P2Y(4) receptors are activated by UTP (the P2Y(2) and the rat, but not the human P2Y(4) receptor are also activated by ATP), the P2Y(6) receptor is activated by UDP, and the P2Y(14) receptor by UDP-glucose. Derivatives and analogs of the physiological nucleotides UTP, UDP and ATP have been synthesized and evaluated in order to obtain enzymatically stable, subtype-selective agonists. P2Y(2) agonists are currently in clinical development for cystic fibrosis and dry eye syndrome. Selective antagonists for pyrimidinergic P2Y receptors are still lacking.