The newly synthesized selective Ca2+/calmodulin dependent protein kinase II inhibitor KN-93 reduces dopamine contents in PC12h cells

Biochem Biophys Res Commun. 1991 Dec 31;181(3):968-75. doi: 10.1016/0006-291x(91)92031-e.


We reported that one of the isoquinolinesulfonamide derivatives, KN-62, is a potent and specific inhibitor of Ca2+/calmodulin-dependent protein kinase II (CaMKII) (Tokumitsu, H., Chijiwa, T., Hagiwara, M., Mizutani, A., Terasawa, M. and Hidaka, H. (1990) J. Biol. Chem. 265, 4315-4320). We have now investigated the inhibitory property of a newly synthesized methoxybenzenesulfonamide, KN-93, on CaMKII activity in situ and in vitro. KN-93 elicited potent inhibitory effects on CaMKII phosphorylating activity with an inhibition constant of 0.37 microM but this compound had no significant effects on the catalytic activity of cAMP-dependent protein kinase, Ca2+/phospholipid dependent protein kinase, myosin light chain kinase and Ca(2+)-phosphodiesterase. KN-93 also inhibited the autophosphorylation of both the alpha- and beta-subunits of CaMKII. Kinetic analysis indicated that KN-93 inhibits CaMKII, in a competitive fashion against calmodulin. To evaluate the regulatory role of CaMKII on catecholamine metabolism, we examined the effect of KN-93 on dopamine (DA) levels in PC12h cells. The DA levels decreased in the presence of KN-93. Further, the tyrosine hydroxylase (TH) phosphorylation induced by KCl or acetylcholine was significantly suppressed by KN-93 in PC12h cells while events induced by forskolin or 8-Br-cAMP were not affected. These results suggest that KN-93 inhibits DA formation by modulating the reaction rate of TH to reduce the Ca(2+)-mediated phosphorylation levels of the TH molecule.

MeSH terms

  • Animals
  • Benzylamines / pharmacology*
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Cattle
  • Chickens
  • Dopamine / metabolism*
  • Kinetics
  • Muscle, Smooth / enzymology
  • Myocardium / enzymology
  • PC12 Cells
  • Phosphorylation
  • Prosencephalon / enzymology
  • Protein Kinase Inhibitors*
  • Protein Kinases / isolation & purification
  • Rabbits
  • Rats
  • Sulfonamides / pharmacology*


  • Benzylamines
  • Protein Kinase Inhibitors
  • Sulfonamides
  • KN 93
  • Protein Kinases
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Dopamine