A Neoceptor Approach to Unraveling Microscopic Interactions between the Human A2A Adenosine Receptor and Its Agonists

Summary Strategically mutated neoceptors, e.g., with anionic residues in TMs 3 and 7 intended for pairing with positively charged amine-modified nucleosides, were derived from the antiinflammatory A 2A adenosine receptor (AR). Adenosine derivatives functionalized at the 5′, 2, and N 6 positions were synthesized. The T88D mutation selectively enhanced the binding of the chain-length-optimized 5′-(2-aminoethyl)uronamide but not 5′-(2-hydroxyethyl)uronamide, suggesting a critical role of the positively charged amine. Combination of this modification with the N 6 -(2-methylbenzyl) group enhanced affinity at the Q89D- and N181D- but not the T88D-A 2A AR. Amino groups placed near the 2- or N 6 -position only slightly affected the binding to mutant receptors. The 5′-hydrazide MRS3412 was 670- and 161-fold enhanced, in binding and functionally, respectively, at the Q89D-A 2A AR compared to the wild-type. Thus, we identified and modeled pairs of A 2A AR-derived neoceptor-neoligand, which are pharmacologically orthogonal with respect to the native species.