Dumont Céline, Blanchard Nicolas, Di Bartolo Vincenzo, Lezot Nathalie, Dufour Evelyne, Jauliac Sébastien, Hivroz Claire
Institut National de la Santé et de la Recherche Médicale, Unité 520, Institut Curie, Institut Pasteur, Paris, France.
J Immunol. 2002 Aug 15;169(4):1705-12. doi: 10.4049/jimmunol.169.4.1705.
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.
TCR与MHC/肽复合物结合后下调被认为对T细胞活化至关重要，因为它允许受体的连续触发以及受刺激细胞的脱敏。我们研究了两名ZAP-70免疫缺陷患者T细胞中的CD3/TCR下调和ζ链降解。我们发现，在TCR高占据率时，无论T细胞是否表达ZAP-70，CD3/TCR的下调情况相当。然而，如果TCR占据率低，我们发现ZAP-70阴性T细胞中CD3/TCR的下调程度低于ZAP-70阳性T细胞。我们研究了P116（一个ZAP-70阴性的Jurkat细胞衍生克隆）以及转染了编码野生型或激酶失活形式ZAP-70基因的P116细胞中的CD3/TCR下调情况。在高占据率时，TCR的下调不需要ZAP-70，而在低TCR占据率时，在没有ZAP-70以及表达ZAP-70激酶失活突变体的细胞中，下调明显减少。因此，仅ZAP-70的存在不足以实现下调；该分子的激酶活性也是必需的。在ZAP-70缺陷患者的T细胞、P116细胞以及表达ZAP-70激酶失活形式的P116细胞中，TCR触发诱导的ζ链降解也严重受损。在低和高TCR占据率水平均观察到这种TCR诱导的ζ链降解缺陷。我们的结果确定ZAP-70（一种已知对T细胞活化至关重要的酪氨酸激酶）是TCR下调和ζ链降解的关键参与者。
