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