Differential mechanisms of translocation of protein kinase C to plasma membranes in activated human neutrophils |
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| Authors: | S Pontremoli E Melloni M Michetti F Salamino B Sparatore O Sacco B L Horecker |
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| Affiliation: | 1. Institute of Biological Chemistry, University of Genoa, Genoa, Italy;2. Cornell University Medical College Graduate School of Medical Sciences, New York, New York 10021 USA;1. Embryology and Reproductive Technology Lab, School of Veterinary Medicine, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil;2. Food Animal Veterinary Practitioner, Santana do Livramento, RS, Brazil;3. Research Group “Fisiopatologia e Biotécnicas da Reprodução Animal” (FiBRA), Large Ruminant Sector, Department of Animal Medicine, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil;1. Instituto Nacional de Innovación Agraria, Estación Experimental Agraria Canaán, Laboratorio de Biotecnología Reproductiva, Ayacucho, Peru;2. Universidad Nacional de San Cristóbal de Huamanga, Facultad de Ciencias Biológicas, Laboratorio de Biotecnología, Ayacucho, Peru;3. Universidad Científica del Sur, Carrera de Medicina Veterinaria y Zootecnica, Lima, Peru |
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| Abstract: | Three classes of activators of human neutrophils that induce the intracellular translocation of protein kinase C from the cytosol to the particulate fraction were compared for their effects on the properties of the particulate (membrane-bound) enzyme. In cells stimulated with 10 ng/ml of phorbol-12-myristate-13-acetate (PMA) the particulate enzyme is almost fully active in the absence of added Ca2+ or phospholipids and this activity is not released by the Ca2+-chelator EDTA. In contrast, binding of protein kinase C to the particulate fraction in cells treated with the chemotactic factor f-Met-Leu-Phe (fMLF) or with the ionophore A-23187 plus Ca2+ is observed only when the cells are lysed in the presence of 1 mM Ca2+. With these stimuli the particulate enzyme retains a nearly absolute requirement for Ca2+ and phospholipids. Thus only the full intercalation of protein kinase C caused by PMA, which is resistant to removal by chelators stabilizes an active form of protein kinase C in the neutrophil membrane. In confirmation of this conclusion, in isolated plasma membranes loaded with partially purified protein kinase C by incubation with 5 microM Ca2+ further incubation with PMA, but not with fMLF, caused a significant fraction of the bound PKC to become resistant to removal by chelators, and to be nearly fully active in the absence of added activators. |
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