Pro-nucleotide Inhibitors of Adenylyl Cyclases in Intact Cells

Abstract

9-Substituted adenine derivatives with protected phosphoryl groups were synthesized and tested as inhibitors of adenylyl cyclase in isolated enzyme and intact cell systems. Protected 3′-phosphoryl derivatives of 2′,5′-dideoxyadenosine (2′,5′-dd-Ado) and β-L-2′,5′-dd-Ado, protected 5′-phosphoryl derivatives of β-L-2′,3′-dd-Ado, and protected phosphoryl derivatives of two 9-(2-phosphonomethoxy-acyl)-adenines were synthesized. Protection was afforded by two cyclosaligenyl- or three S-acyl-2-thioethyl-substituents. These pro-nucleotides were tested for their capacity to block forskolin-induced increases in [3H]cAMP in OB1771 and F442A preadipocytes and human macrophages prelabeled with [3H]adenine. A striking selectivity for 2′,5′-dd-Ado-3′-phosphoryl derivatives was observed. Cyclosaligenyl-derivatives (IC50 ∼2 μM) were much less potent than S-acyl-2-thioethyl-derivatives. Best studied of these was 2′,5′-dd-Ado-3′-O-bis(S-pivaloyl-2-thioethyl)-phosphate, which blocked [3H]cAMP formation in preadipocytes (IC50 ∼30 nM) and suppressed opening of cAMP-dependent Cl- channels in cardiac myocytes (IC50 ∼800 Nm). None of the pro-nucleotides inhibited adenylyl cyclase per se, whether isolated from rat brain or OB1771 cells. These compounds exhibit the hallmarks of prodrugs. Data suggest they are taken up, are deprotected, and are converted to a potent inhibitory form to inhibit adenylyl cyclase, but only by intact cells. The availability and characteristics of these prodrugs should make them useful for blocking cAMP-mediated pathways in intact cell systems, in biochemical, pharmacological, and potentially therapeutic contexts.