title: Calpain II colocalizes with detergent-insoluble rafts on human and Jurkat T-cells.
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.
authors.affiliation: Department of Microbiology and Immunology, University of Kentucky, Lexington, KY 40536-0298, USA.
authors.forename: Lorri A
authors.initials: LA
authors.lastname: Morford
authors.forename: Kathy
authors.initials: K
authors.lastname: Forrest
authors.forename: Barbara
authors.initials: B
authors.lastname: Logan
authors.forename: L Kevin
authors.initials: LK
authors.lastname: Overstreet
authors.forename: Jens
authors.initials: J
authors.lastname: Goebel
authors.forename: William H
authors.initials: WH
authors.lastname: Brooks
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Roszman
mesh_terms: D002154:Calpain / Q000378:metabolism*; D003902:Detergents; D006801:Humans; D019169:Jurkat Cells; D008563:Membrane Lipids / Q000378:metabolism*; D013601:T-Lymphocytes / Q000201:enzymology* / Q000378:metabolism
chemical_list: D003902:Detergents; D008563:Membrane Lipids; D002154:Calpain