Identification of molecules involved in inactivation of mast cells.

我们使用逆转录病毒介导的信号序列捕获方法SST-REX从培养的骨髓来源的小鼠肥大细胞中寻找分泌蛋白和膜蛋白。从这个筛选，我们确定了一种新的膜蛋白窝藏与抑制性NK受体的同源性。该蛋白质在细胞外Domein中具有单个免疫球蛋白样结构域，在细胞内结构域中具有三个或四个ITIM抑制基序，并被命名为LMIR 1，其代表Jeukocyte-associated mono IG receptor-1。从数据库搜索中，我们还鉴定了类似于LMIR 1的LMIR-2-6，并分离了这些蛋白质的全长cDNA。LMIR 1和3在胞内结构域中具有ITIM基序，并且在连接后，它们诱导磷酸酶SHP 1、SHP 2和SHIP的磷酸化，从而诱导抑制信号。另一方面，LMIR 2、4、5和6具有短的胞内结构域，并通过跨膜结构域与活化受体包括DAP 10、DAP 12和FcRg结合。我们已经开发了针对LMIR-1-6的单克隆抗体。为了阐明这些分子的生理作用，特别是在肥大细胞活化的控制中，我们现在正试图鉴定LMIR 1和3的配体，并产生LMIRI-3的敲除小鼠。

We searched for secreted and membrane proteins from cultured bone marrow-derived mouse mast cells using retrovirus-mediated signal sequence trap method SST-REX. From this screening, we identified a novel membrane protein harboring a homology with inhibitory NK receptors. This protein harbors a single immunoglobulin like domain in the extracellular domein and three or four ITIM inhibitory motifs in the intracellular domain, and was designated as LMIRl that stands for Jeukocyte-associated mono Ig receptor-l. From the data base search, we also identified LMIR-2-6 that resemble LMIR1, and isolated full-length cDNAs for these proteins. LMIRl and 3 harbors ITIM motifs in the intracellular domain, and upon ligation, they induced phosphorylation of phosphatases SHP1, SHP2, and SHIP, thereby inducing inhibitory signals. On the other hand, LMIR2, 4, 5, and 6 have short intracellular domain, and associate with activating receptors including DAP10, DAP12 and FcRg through the transmembrane domains. We have developed monoclonal antibodies against LMIR-1-6. To clarify the physiological roles of these molecules especially in the control of mast cell activation, we are now trying to identify the ligands for LMIR1 and 3, and to generate the knockout mice for LMIRI-3.