German Cancer Research Center (DKFZ), Innate Immunity, Heidelberg, Germany.
Blood. 2011 Jul 28;118(4):936-45. doi: 10.1182/blood-2010-11-317016. Epub 2011 Jun 9.
The triggering receptor expressed on myeloid cells 1 (TREM-1) has been implicated in the production of proinflammatory cytokines and chemokines during bacterial infection and sepsis. For downstream signal transduction, TREM-1 is coupled to the ITAM-containing adaptor DAP12. Here, we demonstrate that Bruton tyrosine kinase (Btk), a member of the Tec kinases, becomes phosphorylated upon TREM-1 triggering. In U937-derived cell lines, in which expression of Btk was diminished by shRNA-mediated knockdown, phosphorylation of Erk1/2 and PLCγ1 and Ca²⁺ mobilization were reduced after TREM-1 stimulation. Importantly, TREM-1-induced production of the pro-inflammatory cytokines, TNF-α and IL-8, and up-regulation of activation/differentiation cell surface markers were impaired in Btk knockdown cells. Similar results were obtained upon TREM-1 stimulation of BMDCs of Btk(-/-) mice. The analysis of cells containing Btk mutants revealed that intact membrane localization and a functional kinase domain were required for TREM-1-mediated signaling. Finally, after TREM-1 engagement, TNF-α production by PBMCs was reduced in the majority of patients suffering from X-linked agammaglobulinemia (XLA), a rare hereditary disease caused by mutations in the BTK gene. In conclusion, our data identify Btk as a positive regulator in the ITAM-mediated TREM-1/DAP12 pathway and suggest its implication in inflammatory processes.
髓样细胞表达的触发受体 1（TREM-1）已被牵涉到细菌感染和脓毒症期间促炎细胞因子和趋化因子的产生。对于下游信号转导，TREM-1 与含有 ITAM 的衔接蛋白 DAP12 偶联。在这里，我们证明 Bruton 酪氨酸激酶（Btk），一种 Tec 激酶家族的成员，在 TREM-1 触发后发生磷酸化。在 U937 衍生的细胞系中，通过 shRNA 介导的敲低降低了 Btk 的表达，在 TREM-1 刺激后，Erk1/2 和 PLCγ1 的磷酸化以及 Ca²⁺动员减少。重要的是，在 Btk 敲低细胞中，TREM-1 诱导的促炎细胞因子 TNF-α 和 IL-8 的产生以及激活/分化细胞表面标志物的上调受损。在 Btk（-/-）小鼠的 BMDC 中进行 TREM-1 刺激时也获得了相似的结果。对含有 Btk 突变体的细胞的分析表明，完整的膜定位和功能激酶结构域是 TREM-1 介导的信号所必需的。最后，在 TREM-1 结合后，大多数患有 X 连锁无丙种球蛋白血症（XLA）的患者的 PBMCs 中 TNF-α 的产生减少，XLA 是一种由 BTK 基因突变引起的罕见遗传性疾病。总之，我们的数据将 Btk 鉴定为 ITAM 介导的 TREM-1/DAP12 途径中的正调节剂，并提示其在炎症过程中的作用。
