Basic Protein in Brain Myelin Is Phosphorylated by Endogenous Phospholipid-Sensitive Ca2+-Dependent Protein Kinase |
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Authors: | R. Scott Turner,C.-H. Jen Chou&dagger ,Robert F. Kibler&dagger ,J. F. Kuo |
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Affiliation: | Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia, U.S.A.;Department of Neurology, Emory University School of Medicine, Atlanta, Georgia, U.S.A. |
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Abstract: | Abstract: Phosphorylation of myelin basic protein (MBP) in rat or rabbit brain myelin was markedly stimulated by Ca2+, and this reaction was not essentially augmented by exogenous phosphatidylserine or calmodulin or both. Solubilization of myelin with 0.4% Triton X-100 plus 4 m M EGTA, with or without further fractionation, showed that Ca2+-dependent phosphorylation of MBP required phosphatidylserine, but not calmodulin. DEAE-cellulose chromatography of solubilized myelin revealed a pronounced peak of protein kinase activity stimulated by a combination of Ca2+ and phosphatidylserine; a protein kinase stimulated by Ca2+ plus calmodulin was not detected. These findings clearly indicate an involvement of phospholipid-sensitive Ca2+-dependent protein kinase in phosphorylation of brain MBP, although a possible role for the calmodulin-sensitive species of Ca2+-dependent protein kinase in this reaction could not be excluded or established. Phosphorylation of MBP in solubilized rat myelin catalyzed by the phospholipid-sensitive enzyme was inhibited by adriamycin, palmitoylcarnitine, trifluoperazine, melittin, polymyxin B, and N -(6-aminohexyl)-5-chloro-l-naphthalenesulfonamide (W–7). |
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Keywords: | Myelin Ca2+ Phosphatidylserine Calmodulin Basic protein phosphorylation |
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