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Molecular and Cellular Biology, August 2004, p. 6957-6966, Vol. 24, No. 16
0270-7306/04/$08.00+0 DOI: 10.1128/MCB.24.16.6957-6966.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
Activation
Division of Immunology, Department of Translational Medical Sciences,1 Division of Medical Virology, Department of Molecular Microbiology and Immunology, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8523,2 Laboratory for Immunochaperones, RIKEN Research Center for Allergy and Immunology, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan3
Received 15 January 2004/ Returned for modification 24 February 2004/ Accepted 18 May 2004
In anergic T cells, T-cell receptor (TCR)-mediated responses are functionally inactivated by negative regulatory signals whose mechanisms are poorly understood. Here, we show that CD4+ T cells anergized in vivo by superantigen Mls-1a express a scaffolding protein, transforming growth factor ß-activated protein kinase 1-binding protein 1 (TAB1), that negatively regulates TCR signaling through the activation of mitogen-activated protein kinase p38
. TAB1 was not expressed in naive and activated CD4+ T cells. Inhibition of p38 activity in anergic T cells by a chemical inhibitor resulted in the recovery of interleukin 2 (IL-2) and the inhibition of IL-10 secretion. T-cell hybridoma 2B4 cells transduced with TAB1-containing retrovirus (TAB1-2B4 cells) showed activated p38
, inhibited extracellular signal-regulated kinase (ERK) activity, culminating in reduced IL-2 levels and increased IL-10 production. The use of a p38 inhibitor or cotransfection of a dominant-negative form of p38 in TAB1-2B4 cells resulted in the recovery of ERK activity and IL-2 production. These results imply that TAB1-mediated activation of p38
in anergic T cells regulates the maintenance of T-cell unresponsiveness both by inhibiting IL-2 production and by promoting IL-10 production.
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