Abstract
Soluble guanylyl cyclase (sGC) plays an important role in cardiovascular function and catalyzes formation of cGMP. sGC is activated by nitric oxide and allosteric stimulators and activators. However, despite its therapeutic relevance, the regulatory mechanisms of sGC are still incompletely understood. A major reason for this situation is that no crystal structures of active sGC have been resolved so far. An important step towards this goal is the identification of high-affinity ligands that stabilize a sGC conformation resembling the active, "fully closed" state. Therefore, we examined inhibition of rat sGC α1β1 by 38 purine and pyrimidine nucleotides with 2,4,6,-trinitrophenyl- and (N-methyl)anthraniloyl substitutions at the ribosyl moiety and compared the data with those for the structurally related membranous ACs (mACs) 1, 2 and 5 and the purified mAC catalytic subunits VC1:IIC2. 2',3'-O-(2,4,6-Trinitrophenyl)-guanosine 5'-triphosphate (TNP-GTP) was the most potent sGC α1β1 inhibitor (Ki, 10.7 nM), followed by 2'-O-(N-methylanthraniloyl)-3'-deoxy-adenosine 5'-triphosphate (2'-MANT-3'-dATP) (Ki, 16.7 nM). Docking studies on a sGCαcat/sGCβcat model derived from the inactive heterodimeric crystal structure of the catalytic domains point to similar interactions of MANT- and TNP-nucleotides with sGC α1β1 and mAC VC1:IIC2. Reasonable binding modes of 2'-MANT-3'-dATP and bis-(M)ANT-nucleotides at sGC α1β1 require a 3'-endo ribosyl conformation (vs. 3'-exo in 3'-MANT-2'-dATP). Overall, inhibitory potencies of nucleotides at sGC α1β1 vs. mACs 1, 2 and 5 correlated poorly. Collectively, we identified highly potent sGC α1β1 inhibitors that may be useful for future crystallographic and fluorescence spectroscopy studies. Moreover, it may become possible to develop mAC inhibitors with selectivity relative to sGC.
- The American Society for Pharmacology and Experimental Therapeutics