In vitro inhibition of Ca2+/calmodulin-dependent kinase II activity by melatonin

Biochim Biophys Acta. 1996 Jun 4;1290(2):191-6. doi: 10.1016/0304-4165(96)00025-6.


Recent evidence suggests that a melatonin (MEL) mechanism of action may be through modulation of Ca2+-activated calmodulin (CaM). MEL binds to CaM with a high affinity, and has been shown to act as a CaM antagonist. Among the CaM-dependent enzymes, Ca2+/Calmodulin-dependent protein kinase II (CaM-kinase II) is a particularly abundant enzyme in the nervous system. In the brain it phosphorylates a broad spectrum of substrates, thus modulating important neuronal functions. We describe the MEL effect on CaM-kinase II activity in vitro. CaM-kinase II was purified from rat brain by column chromatography, and identified by Western immunoblotting. CaM-kinase II activity was assessed in the presence of Ca2+/CaM by the kinase's ability to phosphorylate the synthetic substrate syntide-2 and by enzyme autophosphorylation. MEL inhibited CaM-kinase II activity, and enzyme autophosphorylation. Inhibition of the enzyme by 10(-9) M MEL was nearly of 30%. Trifluoperazine (10 microM), W7 (10 microM), and compound 48/80 (30 micrograms/ml), inhibited CaM-kinase II activity by 40%, 42%, and 93%, respectively. Both EGTA (5 mM) and MEL (10(-5) M) abolished autophosphorylation. The effect of MEL on CaM-kinase II activity was specific, since neither serotonin, N-acetylserotonin, nor 6-hydroxymelatonin inhibited its activity. Our results support the hypothesis that MEL acts as a CaM antagonist and cellular functions may be rhythmically regulated by MEL modulation of CaM-dependent protein phosphorylation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain / enzymology
  • Calcium / metabolism
  • Calcium-Calmodulin-Dependent Protein Kinases / antagonists & inhibitors*
  • Calmodulin / antagonists & inhibitors
  • Enzyme Inhibitors / pharmacology
  • Male
  • Melatonin / pharmacology*
  • Phosphorylation
  • Rats


  • Calmodulin
  • Enzyme Inhibitors
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Melatonin
  • Calcium