A Comparison in the Use of the Crystallographic Structure of the Human A1 or the A2A Adenosine Receptors as a Template for the Construction of a Homology Model of the A3 Subtype

In the last decades, the field of therapeutic application in targeting the human A(3) adenosine receptor has represented a rapidly growing area of research in adenosine field. Both agonists and antagonists have been described to have a potential application in the treatment of several diseases, including, for example, glaucoma, cancer, and autoimmune inflammations. To date, the most severe factor limiting the accuracy of the structure-based molecular modeling approaches is the fact that the three-dimensional human A(3) structure has not yet been solved. However, the crystallographic structures of either human A(1) or A(2A) subtypes are available as potential templates for the construction of its homology model. In this study, we have compared the propensity of both models to accommodate a series of known potent and selective human A(3) agonists and antagonists. As described, on the basis of the results obtained from this preliminary study, it is possible to affirm that the human A(3) receptor model based on the crystallographic structure of the A(1) subtype can represent a valid alternative to the one conventionally used today, based on the available A(2A) structures.