Cholera toxin B-subunit prevents activation and proliferation of human CD4+ T cells by activation of a neutral sphingomyelinase in lipid rafts |
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Authors: | Rouquette-Jazdanian Alexandre K Foussat Arnaud Lamy Laurence Pelassy Claudette Lagadec Patricia Breittmayer Jean-Philippe Aussel Claude |
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Institution: | Institut National de la Santé et de la Recherche Médicale (INSERM) Unit 576, IFR 50, H?pital de l'Archet I, Nice Cedex 3, France. |
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Abstract: | The inhibition of human CD4+ T lymphocyte activation and proliferation by cholera toxin B-subunit (CTB) is a well-established phenomenon; nevertheless, the exact mechanism remained unclear. In the present study, we propose an explanation for the rCTB-induced inhibition of CD4+ T lymphocytes. rCTB specifically binds to GM1, a raft marker, and strongly modifies the lipid composition of rafts. First, rCTB inhibits sphingomyelin synthesis; second, it enhances phosphatidylcholine synthesis; and third, it activates a raft-resident neutral sphingomyelinase resembling to neutral sphingomyelinase type 1, thus generating a transient ceramide production. We demonstrated that these ceramides inhibit protein kinase Calpha phosphorylation and its translocation into the modified lipid rafts. Furthermore, we show that rCTB-induced ceramide production activate NF-kappaB. Combined all together: raft modification in terms of lipids, ceramide production, protein kinase Calpha inhibition, and NF-kappaB activation lead to CD4+ T cell inhibition. |
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