T Cell Signalling Laboratory, Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
T Cell Signalling Laboratory, Sir William Dunn School of Pathology, University of Oxford, Oxford, UK.
EMBO J. 2015 Feb 3;34(3):393-409. doi: 10.15252/embj.201387725. Epub 2014 Dec 22.
THEMIS is critical for conventional T-cell development, but its precise molecular function remains elusive. Here, we show that THEMIS constitutively associates with the phosphatases SHP1 and SHP2. This complex requires the adapter GRB2, which bridges SHP to THEMIS in a Tyr-phosphorylation-independent fashion. Rather, SHP1 and THEMIS engage with the N-SH3 and C-SH3 domains of GRB2, respectively, a configuration that allows GRB2-SH2 to recruit the complex onto LAT. Consistent with THEMIS-mediated recruitment of SHP to the TCR signalosome, THEMIS knock-down increased TCR-induced CD3-ζ phosphorylation, Erk activation and CD69 expression, but not LCK phosphorylation. This generalized TCR signalling increase led to augmented apoptosis, a phenotype mirrored by SHP1 knock-down. Remarkably, a KI mutation of LCK Ser59, previously suggested to be key in ERK-mediated resistance towards SHP1 negative feedback, did not affect TCR signalling nor ligand discrimination in vivo. Thus, the THEMIS:SHP complex dampens early TCR signalling by a previously unknown molecular mechanism that favours T-cell survival. We discuss possible implications of this mechanism in modulating TCR output signals towards conventional T-cell development and differentiation.
THEMIS 对常规 T 细胞发育至关重要，但它的确切分子功能仍难以捉摸。在这里，我们表明 THEMIS 与磷酸酶 SHP1 和 SHP2 持续相关。这种复合物需要衔接蛋白 GRB2，GRB2 以非 Tyr 磷酸化依赖的方式将 SHP 桥接到 THEMIS 上。相反，SHP1 和 THEMIS 分别与 GRB2 的 N-SH3 和 C-SH3 结构域结合，这种构象允许 GRB2-SH2 将复合物募集到 LAT 上。与 THEMIS 介导的 SHP 向 TCR 信号转导体的募集一致，THEMIS 敲低增加了 TCR 诱导的 CD3-ζ 磷酸化、Erk 激活和 CD69 表达，但不增加 LCK 磷酸化。这种普遍的 TCR 信号增加导致细胞凋亡增加，这一表型与 SHP1 敲低相匹配。值得注意的是，先前认为在 ERK 介导的对 SHP1 负反馈的抗性中关键的 LCK Ser59 的 KI 突变，既不影响体内的 TCR 信号，也不影响配体识别。因此，THEMIS：SHP 复合物通过以前未知的有利于 T 细胞存活的分子机制来抑制早期 TCR 信号。我们讨论了这种机制在调节 TCR 输出信号以促进常规 T 细胞发育和分化方面的可能影响。
