Signal Transduction of Paired Inhibitory Receptors of NK Cells and Macrophages

髓样细胞上表达的触发受体（TREM）在多种先天性免疫细胞上表达，包括单核细胞、巨噬细胞、树突状细胞（DC）、嗜中性粒细胞和破骨细胞。 这些受体通过与信号链DAP 12结合将信号传递到其宿主细胞。 DAP 12信号传导依赖于其胞质尾内基于免疫受体酪氨酸的激活基序（ITAM）的存在。 在刺激DAP 12偶联受体后，DAP 12被磷酸化并募集对下游信号传播至关重要的蛋白质。 最近的研究表明，TREM家族的成员通过DAP 12可以向单核细胞和巨噬细胞传递激活或抑制信号。 然而，骨髓细胞内DAP 12信号传导的生物化学性质在很大程度上未被表征，TREM基因簇的整体免疫学作用也是如此。 因此，我们已经采取了一个双向的方法来了解TREM集群的免疫生物学。我们理解TREM在先天免疫和癌症调节中的作用的第二种方法是解剖骨髓细胞中的DAP 12信号通路。 我们的研究已经在巨噬细胞和单核细胞中确定了一个变化的、发育调节的信号盒。 单核细胞表达两种关键的细胞内衔接子蛋白，T细胞活化接头（LAT）和B细胞活化接头（LAB，也称为非T细胞衔接子，NTAL）。 我们发现，在体外从单核细胞成熟DC或巨噬细胞的过程中，LAT的水平下降，而LAB的水平增加。我们以前的工作已经证明了LAB调节巨噬细胞中炎症细胞因子产生的能力。 最近，我们已经证明，树突状细胞（DC）信号通过LAB。 多个DC lignad的筛选表明真菌颗粒酵母聚糖（Zy）可以引起稳健的LAB磷酸化，而TLR刺激不能。 分级和转染研究表明，LAB磷酸化是由真菌衍生的甘露糖信号通过DC细胞表面上的Dectin-1引起的。 有趣的是，我们发现缺乏LAB的DC由于核β连环蛋白水平的增加而产生较低水平的炎性细胞因子。 因此，T细胞的反应减少，在LAB空小鼠和这些小鼠更容易受到真菌infection.In除了我们的信号转导研究在先天免疫系统的髓腔中，我们研究的作用TREM在炎症与癌症相关。 我们发现肿瘤相关的骨髓源性抑制细胞表达TREM 1，并且携带4 T1乳腺癌的小鼠血液中可溶性TREM 1水平升高。 此外，我们发现TREM 2在肿瘤相关巨噬细胞上的高表达，并且我们已经开始评估TREM 2可能在炎症相关结肠癌中发挥的作用。

The Triggering Receptors Expressed on Myeloid Cells (TREM) are expressed on a variety of innate immune cells including monocytes, macrophages, dendritic cells (DC), neutrophils, and osteoclasts. These receptors deliver signals to their host cells via association with the signaling chain, DAP12. DAP12 signaling is dependent on the presence of an immunoreceptor tyrosine-based activation motif (ITAM) within its cytoplasmic tail. Upon stimulation of a DAP12-coupled receptor, DAP12 is phosphorylated and recruits proteins critical to the propagation of downstream signals. Recent work has demonstrated that members of the TREM family, via DAP12, can deliver either activation or inhibitory signals to monocytes and macrophages. However, the biochemical nature of DAP12 signaling within myeloid cells is largely uncharacterized as is the overall immunological role of the TREM gene cluster. Thus, we have taken a bipartite approach to understand the immunobiology of the TREM cluster. Our second approach to understanding the role of TREM in regulation of innate immunity and cancer is dissection of the DAP12 signaling pathway in myeloid cells. Our studies have identified a shifting, developmentally regulated signaling cassette in macrophages and monocytes. Monocytes express two key intracellular adaptor proteins, the Linker for Activation of T cells (LAT) and the Linker for Activation of B cells (LAB, also known as the Non-T cell Adaptor, NTAL). We find that during maturation of DC or macrophages from monocytes in vitro, the levels of LAT fall whereas the levels of LAB increase. Our previous work had demonstrated the ability of LAB to regulate inflammatory cytokine production in macrophages. More recently, we have demonstrated that dendritic cells (DC) signal via LAB. A screen of multiple DC lignads suggested that the fungal particle zymosan (Zy) could elicit robust LAB phosphorylation whereas TLR stimulation does not. Fractionation and transfection studies demonstrated that LAB phosphorylation was caused by fungal-derived mannons signaling via Dectin-1 on the DC cell surface. Interestingly, we found that DC lacking LAB produced lower levels of inflammatory cytokine due to increased levels of nuclear beta catenin. Accordingly, T cell responses are reduced in LAB null mice and these mice are more susceptible to fungal infection.In addition to our signaling studies in the myeloid compartment of the innate immune system we study the role of the TREM in the inflammation associated with cancer. We find that tumor associated myeloid-derived suppressor cells express TREM1 and that mice harboring 4T1 breast cancers have elevated levels of soluble (s)TREM1 in their blood. In addition, we find high expression of TREM2 on tumor associated macrophages and we have begun to assess the role that TREM2 may play in inflammation associated cancer of the colon.