Structure activity and molecular modeling analyses of ribose- and base-modified uridine 5′-triphosphate analogues at the human P2Y 2 and P2Y4 receptors

Article abstract of DOI:10.1016/j.bcp.2005.11.010

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 P2Y₂ and P2Y₄ receptors. UTP analogues with substitutions in the 2′-position of the ribose moiety retained capacity to activate both P2Y₂ and P2Y₄ 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 P2Y₄ receptor. 4-Thio substitution of the uracil base resulted in a UTP analogue with increased potency relative to UTP for activation of both the P2Y₂ and P2Y₄ 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 P2Y₂ receptor than P2Y₄ receptor. 6-Aza-UTP was a P2Y₂ receptor agonist that exhibited no activity at the P2Y₄ receptor. Stereoisomers of UTPαS and 2′-deoxy-UTPαS were more potent at the P2Y ₂ than P2Y₄ 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 P2Y₂ and P2Y₄ receptor binding pockets with the most prominent dissimilarities of the two receptors located in the second transmembrane domain (V90 in the P2Y₂ receptor and I92 in the P2Y₄ receptor) and the second extracellular loop (T182 in the P2Y₂ receptor and L184 in the P2Y₄ receptor). In summary, this work reveals substitutions in UTP that differentially affect agonist activity at P2Y₂ versus P2Y₄ receptors and in combination with molecular modeling studies should lead to chemical synthesis of new receptor subtype-selective drugs.