Article: article from journal or magazin.
Degradation of ZAP-70 following antigenic stimulation in human T lymphocytes: role of calpain proteolytic pathway.
Journal of Immunology
T cell activation by the specific Ag results in dramatic changes of the T cell phenotype that include a rapid and profound down-regulation and degradation of triggered TCRs. In this work, we investigated the fate of the TCR-associated ZAP-70 kinase in Ag-stimulated T cells. T cells stimulated by peptide-pulsed APCs undergo an Ag dose-dependent decrease of the total cellular content of ZAP-70, as detected by FACS analysis and confocal microscopy on fixed and permeabilized T cell-APC conjugates and by Western blot on total cell lysates. The time course of ZAP-70 consumption overlaps with that of zeta-chain degradation, indicating that ZAP-70 is degraded in parallel with TCR internalization and degradation. Pharmacological activation of protein kinase C (PKC) does not induce ZAP-70 degradation, which, on the contrary, requires activation of protein tyrosine kinases. Two lines of evidence indicate that the Ca2+-dependent cysteine protease calpain plays a major role in initiating ZAP-70 degradation: 1) treatment of T cells with cell-permeating inhibitors of calpain markedly reduces ZAP-70 degradation; 2) ZAP-70 is cleaved in vitro by calpain. Our results show that, in the course of T cell-APC cognate interaction, ZAP-70 is rapidly degraded via a calpain-dependent mechanism.
Antigen-Presenting Cells/immunology, Antigen-Presenting Cells/metabolism, Antigens/immunology, Calpain/metabolism, Calpain/physiology, Cell Line, Transformed, Clone Cells, Down-Regulation/immunology, Humans, Hydrolysis, Lymphocyte Activation/drug effects, Membrane Proteins/antagonists & inhibitors, Membrane Proteins/metabolism, Protein-Tyrosine Kinases/antagonists & inhibitors, Protein-Tyrosine Kinases/metabolism, Receptors, Antigen, T-Cell/antagonists & inhibitors, Receptors, Antigen, T-Cell/metabolism, T-Lymphocytes/enzymology, T-Lymphocytes/immunology, Tetradecanoylphorbol Acetate/pharmacology, ZAP-70 Protein-Tyrosine Kinase
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