Whitney G, Wang S, Chang H, Cheng K Y, Lu P, Zhou X D, Yang W P, McKinnon M, Longphre M
Inflammation and Pulmonary Drug Discovery Department, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, NJ 08543-4000, USA.
Eur J Biochem. 2001 Dec;268(23):6083-96. doi: 10.1046/j.0014-2956.2001.02543.x.
The siglecs (sialic acid-binding Ig-like lectins) are a distinct subset of the Ig superfamily with adhesion-molecule-like structure. We describe here a novel member of the siglec protein family that shares a similar structure including five Ig-like domains, a transmembrane domain, and a cytoplasmic tail containing two ITIM-signaling motifs. Siglec-10 was identified through database mining of an asthmatic eosinophil EST library. Using the Stanford G3 radiation hybrid panel we were able to localize the genomic sequence of siglec-10 within the cluster of genes on chromosome 19q13.3-4 that encode other siglec family members. We have demonstrated that siglec-10 is an immune system-restricted membrane-bound protein that is highly expressed in peripheral blood leukocytes as demonstrated by Northern, RT-PCR and flow cytometry. Binding assays determined that the extracellular domain of siglec-10 was capable of binding to peripheral blood leukocytes. The cytoplasmic tail of siglec-10 contains four tyrosines, two of which are embedded in ITIM-signaling motifs (Y597 and Y667) and are likely involved in intracellular signaling. The ability of tyrosine kinases to phosphorylate the cytoplasmic tyrosines was evaluated by kinase assay using wild-type siglec-10 cytoplasmic domain and Y-->F mutants. The majority of the phosphorylation could be attributed to Y597 andY667. Further experiments with cell extracts suggest that SHP-1 interacts with Y667 and SHP-2 interacts with Y667 in addition to another tyrosine. This is very similar to CD33, which also binds the phosphatases SHP-1 and SHP-2, therefore siglec-10, as CD33, may be characterized as an inhibitory receptor.
唾液酸结合免疫球蛋白样凝集素（Siglecs）是免疫球蛋白超家族中具有黏附分子样结构的一个独特亚群。我们在此描述了Siglec蛋白家族的一个新成员，它具有相似的结构，包括五个免疫球蛋白样结构域、一个跨膜结构域和一个含有两个免疫受体酪氨酸抑制基序（ITIM）信号基序的胞质尾。通过对哮喘嗜酸性粒细胞EST文库进行数据库挖掘鉴定出了Siglec-10。利用斯坦福G3辐射杂种细胞板，我们能够将Siglec-10的基因组序列定位到19号染色体q13.3 - 4上编码其他Siglec家族成员的基因簇内。我们已经证明Siglec-10是一种免疫系统限制性膜结合蛋白，通过Northern印迹、逆转录聚合酶链反应（RT-PCR）和流式细胞术证明其在外周血白细胞中高度表达。结合试验确定Siglec-10的胞外结构域能够与外周血白细胞结合。Siglec-10的胞质尾含有四个酪氨酸，其中两个（Y597和Y667）嵌入ITIM信号基序中，可能参与细胞内信号传导。通过使用野生型Siglec-10胞质结构域和Y→F突变体进行激酶测定，评估了酪氨酸激酶磷酸化胞质酪氨酸的能力。大部分磷酸化可归因于Y597和Y667。对细胞提取物进行的进一步实验表明，除了另一个酪氨酸外，蛋白酪氨酸磷酸酶-1（SHP-1）与Y667相互作用，蛋白酪氨酸磷酸酶-2（SHP-2）与Y667相互作用。这与CD33非常相似，CD33也结合磷酸酶SHP-1和SHP-2，因此Siglec-10与CD33一样，可能被表征为一种抑制性受体。
