Structure activity and molecular modeling analyses of ribose- and base-modified uridine 5′-triphosphate analogues at the human P2Y2 and P2Y4 receptors

With the long-term goal of developing receptor subtype-selective high affinity agonists for the uracil nucleotide-activated P2Y receptors we have carried-out a series of structure activity and molecular modeling studies of the human P2Y(2) and P2Y(4) receptors. UTP analogues with substitutions in the T-position of the ribose moiety retained capacity to activate both P2Y(2) and P2Y(4) receptors. Certain of these analogues were equieffective for activation of both receptors whereas 2'-amino-2'-deoxy-UTP exhibited higher potency for the P2Y(2) receptor and 2'-azido-UTP exhibited higher potency for the P2Y(4) receptor. 4-Thio substitution of the uracil base resulted in a UTP analogue with increased potency relative to UTP for activation of both the P2Y(2) and P2Y(4) receptors. In contrast, 2-thio substitution and halo- or alkyl substitution in the 5-position of the uracil base resulted in molecules that were 3-30-fold more potent at the P2Y(2) receptor than P2Y(4) receptor. 6-Aza-UTP was a P2Y(2) receptor agonist that exhibited no activity at the P2Y(4) receptor. Stereoisomers of UTP alpha S and 2'-deoxy-UTP alpha S were more potent at the P2Y(2) than P2Y(4) receptor, and the R-configuration was favored at both receptors. Molecular docking studies revealed that the binding mode of UTP is similar for both the P2Y(2) and P2Y(4) receptor binding pockets with the most prominent dissimilarities of the two receptors located in the second transmembrane domain (V90 in the P2Y(2) receptor and 192 in the P2Y(4) receptor) and the second extracellular loop (T182 in the P2Y(2) receptor and L184 in the P2Y(4) receptor). In summary, this work reveals substitutions in UTP that differentially affect agonist activity at P2Y(2) versus P2Y(4) receptors and in combination with molecular modeling studies should lead to chemical synthesis of new receptor subtype-selective drugs. (c) 2005 Elsevier Inc. All rights reserved.