Calpain II colocalizes with detergent-insoluble rafts on human and Jurkat T-cells |
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Authors: | Morford Lorri A Forrest Kathy Logan Barbara Overstreet L Kevin Goebel Jens Brooks William H Roszman Thomas L |
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Institution: | Department of Microbiology and Immunology, University of Kentucky, Lexington, KY 40536-0298, USA. |
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Abstract: | Calpain, a calcium-dependent cysteine protease, is known to associate with the T-cell plasma membrane and subsequently cleave a number of cytoskeletal-associated proteins. In this study, we report the novel observation that calpain II, but not calpain I, associates with membrane lipid rafts on human peripheral blood T-cells and Jurkat cells. Raft-associated calpain activity is enhanced with exogenous calcium and inhibited with calpeptin, a specific inhibitor of calpain activity. In addition, we demonstrate that calpain cleaves the cytoskeletal-associated protein, talin, during the first 30-min after cell stimulation. We propose that lipid raft associated-calpain II could function in early TCR signaling to facilitate immune synapse formation through cytoskeletal remodeling mechanisms. Hence, we demonstrate that the positioning of calpain II within T-cell lipid rafts strategically places it in close proximity to known calpain substrates that are cleaved during Ag-specific T-cell signaling and immune synapse formation. |
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Keywords: | Human T lymphocyte Jurkat Cellular activation Signal transduction Calpain II Lipid rafts |
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