We reported previously that bisphosphate derivatives of adenosine are antagonists of the P2Y1 receptor and that modification of the ribose in these analogues is tolerated in the P2Y1 receptor binding pharmacophore.
Here we delineate the pharmacological activity of one such non-nucleotide molecule, 2-chloro N6-methyl-(N)-methanocarba-2′-deoxyadenosine-3′,5′-bisphosphate (MRS2279), in which the ribose is replaced by a cyclopentane ring constrained in the (N)-conformation by a cyclopropane moiety.
MRS2279 antagonized 2MeSADP-stimulated inositol phosphate formation in turkey erythrocyte membranes with competitive kinetics (pKB=7.75). High affinity competitive antagonism by MRS2279 was also observed at the human P2Y1 receptor (pKB=8.10) stably expressed in 1321N1 human astrocytoma cells. Antagonism was specific for the P2Y1 receptor since MRS2279 had no effect on activation of the human P2Y2, P2Y4, P2Y6, or P2Y11 receptors by their cognate agonists.
MRS2279 also did not block the capacity of ADP to act through the Gi/adenylyl cyclase linked P2Y receptor of platelets to inhibit cyclic AMP accumulation.
In contrast, the P2Y1 receptor is known to be obligatory in the process of ADP-induced platelet aggregation, and MRS2279 competitively inhibited ADP-promoted platelet aggregation with an apparent affnity (pKB=8.05) similar to that observed at the human P2Y1 receptor heterologously expressed in 1321N1 cells.
Taken together these results illustrate selective high affinity antagonism of the P2Y1 receptor by a non-nucleotide molecule that should prove useful for pharmacological delineation of this receptor in various tissues.
British Journal of Pharmacology (2002) 135, 2004–2010; doi:10.1038/sj.bjp.0704673