Alternative antigen receptor (TCR) signaling in T cells derived from ZAP-70-deficient patients expressing high levels of Syk |
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Authors: | Noraz N Schwarz K Steinberg M Dardalhon V Rebouissou C Hipskind R Friedrich W Yssel H Bacon K Taylor N |
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Affiliation: | Institut de Génétique Moléculaire de Montpellier, CNRS UMR 5535, 1919 Route de Mende, 34293 Montpellier, Cedex 5, France. noraz@igm.cnrs-mop.fr |
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Abstract: | ZAP-70-deficient patients present with nonfunctional CD4+ T cells in the periphery. We find that a subset of primary ZAP-70-deficient T cells, expressing high levels of the related protein-tyrosine kinase Syk, can proliferate in vitro. These cells (denoted herein as Syk(hi)/ZAP-70(-) T cells) provide a unique model in which the contribution of Syk to TCR-mediated responses can be explored in a nontransformed background. Importantly, CD3-induced responses, such as tyrosine phosphorylation of cellular substrates (LAT, SLP76, and PLC-gamma1), as well as calcium mobilization, which are defective in T cells expressing neither ZAP-70 nor Syk, are observed in Syk(hi)/ZAP-70(-) T cells. However, Syk(hi)/ZAP-70(-) T cells differ from control T cells with respect to the T cell antigen receptor (TCR)-mediated activation of the MAPK cascades: extracellular signal-regulated kinase activity and recruitment of the JNK and p38 stress-related MAPK pathways are diminished. This distinct phenotype of Syk(hi)/ZAP-70(-) T cells is associated with a profound decrease in CD3-mediated interleukin 2 secretion and proliferation relative to control T cells. Thus, ZAP-70 and Syk appear to play distinct roles in transducing a TCR-mediated signal. |
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