title: Calpain II-dependent solubilization of a nuclear protein kinase at micromolar calcium concentrations.
abstract: Incubation of isolated, Triton X-100 washed rat liver nuclei with purified bovine myocardial calpain II resulted in solubilization of a histone H1 kinase activity. The release of kinase from nuclei could be prevented by including the calpain inhibitors leupeptin or calpastatin in the incubation. Titration with Ca2+/EGTA buffers indicated that the calpain-dependent release of the kinase was half-maximal at approximately 3 microM Ca2+. In contrast, calpain II required at least 50 microM Ca2+ to produce detectable proteolysis of soluble or membrane-associated substrates. These results suggest that the cell nucleus is a site of calpain II activation and function.
authors.affiliation: Department of Pharmacology and Therapeutics, Medical College of Ohio, Toledo 43699.
authors.forename: R L
authors.initials: RL
authors.lastname: Mellgren
authors.forename: C B
authors.initials: CB
authors.lastname: Rozanov
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002154:Calpain / Q000494:pharmacology*; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology*; D006868:Hydrolysis; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D009687:Nuclear Proteins / Q000032:analysis*; D009994:Osmolar Concentration; D011494:Protein Kinases / Q000032:analysis*; D051381:Rats; D012995:Solubility; D013049:Spectrin / Q000032:analysis
chemical_list: D009687:Nuclear Proteins; D013049:Spectrin; D011494:Protein Kinases; D002154:Calpain; D002118:Calcium