Identification and inhibitory properties of a novel Ca(2+)/calmodulin antagonist.
نویسندگان
چکیده
We developed a high-throughput yeast-based assay to screen for chemical inhibitors of Ca(2+)/calmodulin-dependent kinase pathways. After screening two small libraries, we identified the novel antagonist 125-C9, a substituted ethyleneamine. In vitro kinase assays confirmed that 125-C9 inhibited several calmodulin-dependent kinases (CaMKs) competitively with Ca(2+)/calmodulin (Ca(2+)/CaM). This suggested that 125-C9 acted as an antagonist for Ca(2+)/CaM rather than for CaMKs. We confirmed this hypothesis by showing that 125-C9 binds directly to Ca(2+)/CaM using isothermal titration calorimetry. We further characterized binding of 125-C9 to Ca(2+)/CaM and compared its properties with those of two well-studied CaM antagonists: trifluoperazine (TFP) and W-13. Isothermal titration calorimetry revealed that binding of 125-C9 to CaM is absolutely Ca(2+)-dependent, likely occurs with a stoichiometry of five 125-C9 molecules to one CaM molecule, and involves an exchange of two protons at pH 7.0. Binding of 125-C9 is driven overall by entropy and appears to be competitive with TFP and W-13, which is consistent with occupation of similar binding sites. To test the effects of 125-C9 in living cells, we evaluated mitogen-stimulated re-entry of quiescent cells into proliferation and found similar, although slightly better, levels of inhibition by 125-C9 than by TFP and W-13. Our results not only define a novel Ca(2+)/CaM inhibitor but also reveal that chemically unique CaM antagonists can bind CaM by distinct mechanisms but similarly inhibit cellular actions of CaM.
منابع مشابه
ANTICALMODULIN DRUGS DUE TO THE NET EFFECTS CANNOT ANTAGONIZE DIBUTYRYL-CAMP-MEDIATED SUPPRESSION OF DE NOVO SYNTHESIZED LIPID SECRETION IN BOTH CULTURED MCARDLE CELLS AND RAT HEPATOCYTES
The effects and interaction between cAMP-analogue dibutyryl-cAMP and calmodulin antagonists were investigated on de novo synthesis and secretion of lipids in cultures of hepatoma McArdle-RH7777 cells and normal rat hepatocytes. Dibutyryl cAMP caused a significant decrease in the secretion of de novo synthesized triacyl [3H] glycerol in both cultures of McArdle cells and rat hepatocytes. The ...
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متن کاملANTICALMODULIN DRUGS DUE TO THE NET EFFECTS CANNOT ANTAGONIZE DIBUTYRYL-CAMP-MEDIATED SUPPRESSION OF DE NOVO SYNTHESIZED LIPID SECRETION IN BOTH CULTURED MCARDLE CELLS AND RAT HEPATOCYTES
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ورودعنوان ژورنال:
- Biochemistry
دوره 49 19 شماره
صفحات -
تاریخ انتشار 2010