Germ-line elimination of electric charge on pre-T-cell receptor (TCR) impairs autonomous signaling for β-selection and TCR repertoire formation
Germ-line elimination of electric charge on pre-T-cell receptor (TCR) impairs autonomous signaling for β-selection and TCR repertoire formation
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DOI：
10.1073/pnas.1011228107
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发表时间：
2010-11-16
影响因子：
11.1
通讯作者：
Yamasaki, Sho
中科院分区：
文献类型：
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作者：
Ishikawa, Eri;Miyake, Yasunobu;Yamasaki, Sho
前T细胞受体（pre-T-cell receptor，TCR）是T细胞发育的关键因子，但其配体尚未确定。我们最近提出了一个模型，即前TCR复合物通过前TCR α链的相互作用自发地寡聚化。为了研究这种体内配体非依赖性信号传导的机制，我们建立了表达缺乏带电氨基酸的前TCRa突变体（（DRRR 117）-R-22-R-24-R-102 to A（22）A（24）A（102）A（11）7;4A）的敲入小鼠。在恒定前TCR α（pT α（4A/4A））小鼠中，CD 4（+）CD 8（+）胸腺细胞数量显著减少，而CD 4（-）CD 8（-）胸腺细胞未受影响。双阴性3（DN 3）细胞和γ δ T细胞的百分比在pT α（4A/4A）胸腺中增加，表明β选择在pT α（4A/4A）小鼠中受损。前TCR介导的酪氨酸磷酸化和克隆扩增成双阳性胸腺细胞也有缺陷的敲入小鼠。前TCR在pT α（4A/4A）细胞表面上的表达水平高于野生型，表明pT α中的带电残基对于前TCR的自主参与和随后的内化至关重要。在pT α（4A/4A）小鼠中，前TCR介导的TCR β基因的等位基因排斥也被抑制，从而在pT α（4A/4A）T细胞上表达双TCR β。此外，成熟T细胞的TCR β链可变区（V β）库在pT α（4A/4A）小鼠中显著改变。这些结果表明，pT α的带电残基对于β选择、等位基因排斥和TCR β库形成至关重要。
The pre-T-cell receptor (TCR) is crucial for the early T-cell development, but the ligand for pre-TCR remains unidentified. We recently proposed a model that pre-TCR complexes oligomerize spontaneously through interactions of the pre-TCR alpha chain. To investigate the mechanism underlying this ligand-independent signaling in vivo, we established knock-in mice that express a pre-TCRa mutant lacking charged amino acids ((DRRR117)-R-22-R-24-R-102 to A(22)A(24)A(102)A(11)7;4A). CD4(+)CD8(+) thymocyte number was significantly reduced in invariant pre-TCRa (pT alpha(4A/4A)) mice, whereas CD4(-)CD8(-) thymocytes were unaffected. The percentages of double-negative 3 (DN3) cells and gamma delta T cells were increased in the pT alpha(4A/4A) thymus, indicating that beta-selection is impaired in pT alpha(4A/4A) mice. Pre-TCR-mediated tyrosine phosphorylation and clonal expansion into double-positive thymocytes were also defective in the knock-in mice. Pre-TCR was expressed at higher levels on pT alpha(4A/4A) cell surfaces than on those of the wild type, suggesting that the charged residues in pT alpha are critical for autonomous engagement and subsequent internalization of pre-TCR. Pre-TCR-mediated allelic exclusion of the TCR beta gene was also inhibited in pT alpha(4A/4A) mice, and thereby, dual TCR beta s were expressed on pT alpha(4A/4A) T cells. Furthermore, the TCR beta chain variable region (V beta) repertoire of mature T cells was significantly altered in pT alpha(4A/4A) mice. These results suggest that charged residues of pT alpha are critical for beta-selection, allelic exclusion, and TCR beta repertoire formation.