Centre of Excellence in Medical Biotechnology (CEMB), Faculty of Medical Science, Naresuan University, Phitsanulok 65000, Thailand.
Cell Commun Signal. 2014 Mar 26;12:21. doi: 10.1186/1478-811X-12-21.
Signalling by the T cell antigen receptor (TCR) results in the activation of T lymphocytes. Nck1 and Nck2 are two highly related adaptor proteins downstream of the TCR that each contains three SH3 and one SH2 domains. Their individual functions and the roles of their SH3 domains in human T cells remain mostly unknown.
Using specific shRNA we down-regulated the expression of Nck1 or Nck2 to approximately 10% each in Jurkat T cells. We found that down-regulation of Nck1 impaired TCR-induced phosphorylation of the kinases Erk and MEK, activation of the AP-1 and NFAT transcription factors and subsequently, IL-2 and CD69 expression. In sharp contrast, down-regulation of Nck2 hardly impacts these activation read-outs. Thus, in contrast to Nck2, Nck1 is a positive regulator for TCR-induced stimulation of the Erk pathway. Mutation of the third SH3 domain of Nck1 showed that this domain was required for this activity. Further, TCR-induced NFAT activity was reduced in both Nck1 and Nck2 knock-down cells, showing that both isoforms are involved in NFAT activation. Lastly, we show that neither Nck isoform is upstream of p38 phosphorylation or Ca2+influx.
In conclusion, Nck1 and Nck2 have non-redundant roles in human T cell activation in contrast to murine T cells.
T 细胞抗原受体 (TCR) 的信号转导导致 T 淋巴细胞的激活。Nck1 和 Nck2 是 TCR 下游的两种高度相关的衔接蛋白，它们各自包含三个 SH3 和一个 SH2 结构域。它们的单独功能及其 SH3 结构域在人类 T 细胞中的作用在很大程度上仍然未知。
使用特异性 shRNA，我们将 Jurkat T 细胞中 Nck1 或 Nck2 的表达下调至约 10%。我们发现，下调 Nck1 会损害 TCR 诱导的激酶 Erk 和 MEK 的磷酸化、AP-1 和 NFAT 转录因子的激活以及随后的 IL-2 和 CD69 的表达。相比之下，下调 Nck2 几乎不会影响这些激活的检测结果。因此，与 Nck2 相比，Nck1 是 TCR 诱导的 Erk 通路刺激的正调节剂。Nck1 的第三个 SH3 结构域的突变表明该结构域是这种活性所必需的。此外，TCR 诱导的 NFAT 活性在 Nck1 和 Nck2 敲低细胞中均降低，表明两种同工型均参与 NFAT 激活。最后，我们表明，Nck 两种同工型都不在 p38 磷酸化或 Ca2+内流的上游。
总之，Nck1 和 Nck2 在人类 T 细胞激活中具有非冗余作用，与鼠类 T 细胞不同。
