Fasbender Frank, Claus Maren, Wingert Sabine, Sandusky Mina, Watzl Carsten
Leibniz Research Centre for Working Environment and Human Factors, IfADo, TU-Dortmund, Dortmund, Germany.
Front Immunol. 2017 Jul 7;8:789. doi: 10.3389/fimmu.2017.00789. eCollection 2017.
In a synthetic biology approach using Schneider (S2) cells, we show that SLP-76 is directly phosphorylated at tyrosines Y113 and Y128 by SYK in the presence of ITAM-containing adapters such as CD3ζ, DAP12, or FcεRγ. This phosphorylation was dependent on at least one functional ITAM and a functional SH2 domain within SYK. Inhibition of Src-kinases by inhibitors PP1 and PP2 did not reduce SLP-76 phosphorylation in S2 cells, suggesting an ITAM and SYK dependent, but Src-kinase independent signaling pathway. This direct ITAM/SYK/SLP-76 signaling pathway therefore differs from previously described ITAM signaling. However, the SYK-family kinase ZAP70 required the additional co-expression of the Src-family kinases Fyn or Lck to efficiently phosphorylate SLP-76 in S2 cells. This difference in Src-family kinase dependency of SYK versus ZAP70-mediated ITAM-based signaling was further demonstrated in human lymphocytes. ITAM signaling in ZAP70-expressing T cells was dependent on the activity of Src-family kinases. In contrast, Src-family kinases were partially dispensable for ITAM signaling in SYK-expressing B cells or in natural killer cells, which express SYK and ZAP70. This demonstrates that SYK can signal using a Src-kinase independent ITAM-based signaling pathway, which may be involved in calibrating the threshold for lymphocyte activation.
在一项使用施耐德（S2）细胞的合成生物学方法中，我们发现，在含有免疫受体酪氨酸激活基序（ITAM）的衔接蛋白（如CD3ζ、DAP12或FcεRγ）存在的情况下，脾酪氨酸激酶（SYK）可直接将SLP - 76的酪氨酸Y113和Y128磷酸化。这种磷酸化依赖于SYK内至少一个功能性ITAM和一个功能性Src同源2（SH2）结构域。抑制剂PP1和PP2对Src激酶的抑制并未降低S2细胞中SLP - 76的磷酸化，这表明存在一条依赖ITAM和SYK，但不依赖Src激酶的信号通路。因此，这条直接的ITAM/SYK/SLP - 76信号通路不同于先前描述的ITAM信号通路。然而，SYK家族激酶ζ链相关蛋白激酶70（ZAP70）在S2细胞中有效磷酸化SLP - 76需要额外共表达Src家族激酶Fyn或Lck。SYK与ZAP70介导的基于ITAM的信号传导在Src家族激酶依赖性上的这种差异在人淋巴细胞中得到了进一步证实。在表达ZAP70的T细胞中，基于ITAM的信号传导依赖于Src家族激酶的活性。相反，Src家族激酶对于在表达SYK的B细胞或表达SYK和ZAP70的自然杀伤细胞中的基于ITAM的信号传导部分是可有可无的。这表明SYK可以使用一条不依赖Src激酶的基于ITAM的信号通路进行信号传导，这可能参与校准淋巴细胞激活的阈值。
