Inhibition of calmodulin function by CV-159, a novel dihydropyridine compound

1,4-Dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridine-dicarboxylic acid methyl 6-(5-phenyl-3-pyrazolyloxy)hexyl ester (CV-159), a new compound synthesized from dihydropyridine, was examined for its effect on calmodulin (CaM) function. The concentration of CV-159 producing 50% inhibition of Ca2+/CaM activated myosin light chain kinase (MLC kinase) was 6.2 microM. The apparent Ki value of CV-159 was 0.8 microM for MLC kinase. On the other hand, the concentration of CV-159 producing 50% inhibition of Ca2+/CaM activated cyclic nucleotide phosphodiesterase (Ca2+-PDE) was 0.55 microM. CaM antagonized competitively the CV-159-induced inhibition of activation of both MLC kinase and Ca2+-PDE. Interaction of CV-159 with CaM was also demonstrated by fluorescence studies using dansyl-CaM (5-dimethylaminonaphthalene-1-sulfonylated CaM). CV-159 produced a decrease in fluorescence intensity of dansyl-CaM, in a Ca2+-dependent fashion, and the concentration of this drug producing 50% inhibition of dansyl-CaM fluorescence was 1.2 microM. However, the concentration of nicardipine producing 50% inhibition of MLC kinase exceeded 100 microM. CaM did not antagonize the nicardipine-induced inhibition of Ca2+-PDE. These results suggest that the action of CV-159 is unique in that it inhibits both Ca2+-PDE and MLC kinase, through interaction with calmodulin. CV-159 seems to be a different class of drug from known dihydropyridine compounds.