Differential Inhibition of Various Adenylyl Cyclase Isoforms and Soluble Guanylyl Cyclase by 2′,3′-O-(2,4,6-Trinitrophenyl)-Substituted Nucleoside 5′-Triphosphates

Adenylyl cyclases (ACs) catalyze the conversion of ATP into the second messenger cAMP and play a key role in signal transduction. In a recent study ( Mol Pharmacol 70: 878–886, 2006), we reported that 2′,3′- O -(2,4,6-trinitrophenyl)-substituted nucleoside 5′-triphosphates (TNP-NTPs) are potent inhibitors ( K i values in the 10 nM range) of the purified catalytic subunits VC1 and IIC2 of membranous AC (mAC). The crystal structure of VC1:IIC2 in complex with TNP-ATP revealed that the nucleotide binds to the catalytic site with the TNP-group projecting into a hydrophobic pocket. The aims of this study were to analyze the interaction of TNP-nucleotides with VC1:IIC2 by fluorescence spectroscopy and to analyze inhibition of mAC isoforms, soluble AC (sAC), soluble guanylyl cyclase (sGC), and G-proteins by TNP-nucleotides. Interaction of VC1:IIC2 with TNP-NDPs and TNP-NTPs resulted in large fluorescence increases that were differentially reduced by a water-soluble forskolin analog. TNP-ATP turned out to be the most potent inhibitor for ACV ( K i , 3.7 nM) and sGC ( K i , 7.3 nM). TNP-UTP was identified as the most potent inhibitor for ACI ( K i , 7.1 nM) and ACII ( K i , 24 nM). TNP-NTPs inhibited sAC and GTP hydrolysis by G s - and G i -proteins only with low potencies. Molecular modeling revealed that TNP-GTP and TNP-ATP interact very similarly, but not identically, with VC1:IIC2. Collectively, our data show that TNP-nucleotides are useful fluorescent probes to monitor conformational changes in VC1:IIC2 and that TNP-NTPs are a promising starting point to develop isoform-selective AC and sGC inhibitors. TNP-ATP is the most potent sGC inhibitor known so far.