title: 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.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, Unité 520, Institut Curie, Institut Pasteur, Paris, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Dumont
authors.forename: Nicolas
authors.initials: N
authors.lastname: Blanchard
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Di Bartolo
authors.forename: Nathalie
authors.initials: N
authors.lastname: Lezot
authors.forename: Evelyne
authors.initials: E
authors.lastname: Dufour
authors.forename: Sébastien
authors.initials: S
authors.lastname: Jauliac
authors.forename: Claire
authors.initials: C
authors.lastname: Hivroz
mesh_terms: D015536:Down-Regulation; D006801:Humans; D007153:Immunologic Deficiency Syndromes / Q000201:enzymology / Q000276:immunology; D066298:In Vitro Techniques; D019169:Jurkat Cells; D007700:Kinetics; D008213:Lymphocyte Activation; D008565:Membrane Proteins / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000172:deficiency* / Q000378:metabolism*; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D051746:ZAP-70 Protein-Tyrosine Kinase
chemical_list: D008565:Membrane Proteins; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D011948:Receptors, Antigen, T-Cell; C054979:antigen T cell receptor, zeta chain; D011505:Protein-Tyrosine Kinases; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human