Signal Transduction of Paired Inhibitory Receptors of NK

该项目涉及对一组迅速出现的免疫受体的研究。最近在老鼠和人类身上都发现了许多抑制性免疫受体家族。有趣的是，在这些受体的每个抑制家族中，都有一些蛋白质失去了抑制结构域。相反，这些受体在其跨膜结构域中获得了一个带正电荷的酸，这表明它们可能与信号转导链相互作用，传递积极的信号。在这个项目中，我们研究了免疫细胞功能的正负调节因子的信号转导和生物化学。通过对阳性受体的研究，我们和其他人证明了其中一些受体与新的信号转导链DAP12的关联。从那时起，我们一直在研究DAP12信号转导通路的生化特征。这项工作包括展示参与DAP12早期信号传递的激酶，描述所涉及的接头，以及研究这些通路的调节。此外，对于DAP12，我们正在开始DAP10的研究，这是一条已知与NK细胞和单核细胞内的受体相关的第二链，位于19号染色体上DAP12的130bp处。DAP10包含一个不同于DAP12的基于酪氨酸的基序。这个基序(Y*xNM)提示与磷脂酰肌醇3激酶(PI3K)和接头Grb2相互作用。我们现在正准备剖析DAP10的信号转导机制，以期全面了解这些链在NK细胞、单核细胞和树突状细胞中的作用。我们对成对受体系统的研究现在主要转移到对髓样细胞上表达的触发受体(TREM)的研究上。最近发现TREM-1参与了导致感染性休克的信号放大。据报道，TREM-2参与了树突状细胞的成熟。我们最近描述了TREM样转录本-1，一个可能存在于TREM簇中的抑制性受体。逆转录聚合酶链式反应(RT-PCR)显示TLT-1在多种髓系细胞中均有表达，但Northern印迹显示TLT-1仅在血小板和骨髓中大量表达。免疫组织化学和免疫荧光研究表明，骨髓TLT-1完全来源于巨核细胞。这一发现使TLT-1成为在外周血血小板上描述的第二个抑制性受体(另一个是PECAM-1)，也是唯一一个仅在血小板和巨核细胞中表达的抑制性受体。TLT-1在巨核细胞和血小板中的亚细胞定位和调节表明，TLT-1被巨核细胞预先包装到血小板α颗粒中，以便在血小板脱颗粒后快速表面表达。这些发现提示TLT-1可能参与了α颗粒和/或

This project involves the study of a rapidly emerging group of immune receptors. Many families of inhibitory immune receptors have recently been identified in both mice and humans. Interestingly, within each of these inhibitory families of receptors, there are proteins that have lost the inhibitory domains. Instead these receptors have gained a positively charged acid within their transmembrane domain, suggesting that they may interact with signal transduction chains and transmit positive signals. In this project, we study the signal transduction and biochemistry of both the positive and negative regulators of immune cell function. Through the study of the positive receptors, we and others demonstrated the association of some of these receptors with the novel signal transduction chain DAP12. Since then we have been characterizing the biochemistry of the DAP12 signal transduction pathway. This work has included demonstration of the kinases involved in the early signaling of DAP12, delineation of the adaptors involved, and study of the regulation of these pathways. In addition, to DAP12, we are beginning the study of DAP10, a second chain known to associate with receptors within NK cells and monocytes that is located just 130 bp from DAP12 on Chromosome 19. DAP10 contains a tyrosine based motif unique from that of DAP12. This motif (Y*xNM) suggests interaction with both the phosphatidylinositol 3 kinase (PI3K) and the adaptor Grb2. We are now preparing to dissect the signaling of DAP10 in an effort to fully understand the role of these chains within NK cells, monocytes and dendritic cells. Our studies of paired receptor systems has now largely shifted to the study of the Triggering Receptors Expressed on Myeloid cells (TREM). TREM-1 has recently been shown to be involved in the amplification of signals leading to septic shock. TREM-2 has been reported to be involved in the maturation of dendritic cells. We recently described TREM Like Transcript-1, a putative inhibitory receptor within the TREM cluster. TLT-1 transcripts have been found in various myeloid cells by RT-PCR, however, northern blotting demonstrates abundant TLT-1 expression only in platelets and bone marrow. Immunohistochemical and immunofluorescence studies show that bone marrow TLT-1 is derived exclusively from megakaryocytes. This finding makes TLT-1 only the second inhibitory receptor described on peripheral blood platelets (the other being PECAM-1), and the only inhibitory receptor expressed exclusively in platelets and megakaryocytes. The subcellular localization and regulation of TLT-1 in megakaryocytes and platelets suggests that TLT-1 is prepackaged into the platelet alpha granules by megakaryocytes for rapid surface expression after platelet degranulation. These findings suggest TLT-1 may be involved in the production and release of alpha granules and/or the