ADP- and ATP-mimetics derived from 2'(3')-C-methyladenosine as human P2Y1 and P2Y2 receptor ligands

Nucleotides and their hydrolytic products act through specific nucleotide receptors which are divided in: ionotropic P2X and metabotropic P2Y receptors coupled to G proteins. The P2Y receptor family consists of at least eight human subtypes (P2Y1,2,4,6,11-14), that are activated by either or both adenine and uracil nucleotides [1]. Activation of P2Y receptors generally results in the stimulation of phospholipase C (PLC), which generates inositol phosphates and diacylglycerol from phosphatidyl inositol(4,5)bisphosphate, leading to the rise in intracellular calcium and activation of protein kinase C. According to a dendrogram relating sequence homology, the P2Y1, P2Y2, P2Y4, P2Y6, and P2Y11 receptors form a cluster of preferentially Gq-coupled receptors, and the P2Y12, P2Y13, and P2Y14 form a cluster of preferentially Gi-coupled receptors. The P2Y1 and P2Y2 receptors are expressed in most human tissues, including brain, heart, placenta, lungs, liver, skeletal muscle, kidneys, pancreas and variuos blood cells. P2Y1 receptor is activated by ADP, while P2Y2 is activated equipotently by both ATP and UTP. Several ADP and ATP analogues have been investigated to explore structure-activity relationships for P2Y1 and P2Y2 receptors. It was reported that constraining the riboselike ring as methanocarba analogues of ADP and ATP, the Northern (N, 2'-exo) conformation was associated with increased agonist potency at recombinant human P2Y1 and P2Y2 receptors, while the Southern (S, 2'-endo) conformer was less potent. A similar conformational preference of the ribose moiety in binding to uridine nucleotide-activated hP2Y2 receptor was detected with the methanocarba analogues of UTP [2]. In order to further investigate the influence of conformation of ribose-modified ADP and ATP analogues on affinity and efficacy at hP2Y1 and hP2Y2 receptors, we have synthesized the 2'- and 3'-C-methyl derivatives of ADP and ATP. These nucleotides were evaluated for their capacity to promote hP2Y1 and hP2Y2 receptor-mediated activation of phospholipase C at recombinant human receptors expressed in astrocytoma cells. The results of the functional assay will be discussed. [1] Abbracchio MP et al. International Union of Pharmacology LVIII: Update on the P2Y G Protein-Coupled Nucleotide Receptors: From Molecular Mechanisms and Pathophysiology to Therapy. Pharmacol Rev. 2006, 58: 281-341. [2] Kim, H. S.; Ravi, R. G.; Marquez, V. E.; Maddileti, S.; Wihlborg, A.-K.; Erlinge, D.; Malmsjö, M.; Boyer, J. L.; Harden, K.; Jacobson, K. A. Methanocarba Modification of Uracil and Adenine Nucleotides: High Potency of Northern Ring Conformation at P2Y1, P2Y2, P2Y4 and P2Y11 but not P2Y6 Receptors. J. Med. Chem. 2002, 45: 208-18.