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

M Sumi, K Kiuchi, T Ishikawa, A Ishii… - Biochemical and …, 1991 - Elsevier
M Sumi, K Kiuchi, T Ishikawa, A Ishii, M Hagiwara, T Nagatsu, H Hidaka
Biochemical and biophysical research communications, 1991Elsevier
We reported that one of the isoquinolinesulfonamide derivatives, KN-62, is a potent and
specific inhibitor of Ca 2+ 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 …
We reported that one of the isoquinolinesulfonamide derivatives, KN-62, is a potent and specific inhibitor of Ca 2+ 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 μM but this compound had no significant effects on the catalytic activity of cAMP-dependent protein kinase, Ca 2+ phospholipid dependent protein kinase, myosin light chain kinase and Ca 2+-phosphodiesterase. KN-93 also inhibited the auto-phosphorylation of both the α-and β-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.
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