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TCR/CD3 down-modulation and zeta degradation are regulated by ZAP-70.

Abstract : TCR down-modulation following binding to MHC/peptide complexes is considered to be instrumental for T cell activation because it allows serial triggering of receptors and the desensitization of stimulated cells. We studied CD3/TCR down-modulation and zeta degradation in T cells from two ZAP-70-immunodeficient patients. We show that, at high occupancy of the TCR, down-modulation of the CD3/TCR is comparable whether T cells express or do not express ZAP-70. However, if TCR occupancy was low, we found that CD3/TCR was down-regulated to a lesser extent in ZAP-70-negative than in ZAP-70-positive T cells. We studied CD3/TCR down-modulation in P116 (a ZAP-70-negative Jurkat cell-derived clone) and in P116 transfected with genes encoding the wild-type or a kinase-dead form of ZAP-70. Down-modulation of the TCR at high occupancy did not require ZAP-70, whereas at low TCR occupancy down-modulation was markedly reduced in the absence of ZAP-70 and in cells expressing a dead kinase mutant of ZAP-70. Thus, the presence of ZAP-70 alone is not sufficient for down-modulation; the kinase activity of this molecule is also required. The degradation of zeta induced by TCR triggering is also severely impaired in T cells from ZAP-70-deficient patients, P116 cells, and P116 cells expressing a kinase-dead form of ZAP-70. This defect in TCR-induced zeta degradation is observed at low and high levels of TCR occupancy. Our results identify ZAP-70, a tyrosine kinase known to be crucial for T cell activation, as a key player in TCR down-modulation and zeta degradation.
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Submitted on : Sunday, May 28, 2006 - 6:50:20 PM
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Céline Dumont, Nicolas Blanchard, Vincenzo Di Bartolo, Nathalie Lezot, Evelyne Dufour, et al.. TCR/CD3 down-modulation and zeta degradation are regulated by ZAP-70.. Journal of Immunology, Publisher : Baltimore : Williams & Wilkins, c1950-. Latest Publisher : Bethesda, MD : American Association of Immunologists, 2002, 169, pp.1705-12. ⟨10.4049/jimmunol.169.4.1705⟩. ⟨inserm-00000024⟩

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