Cornish A L, Freeman S, Forbes G, Ni J, Zhang M, Cepeda M, Gentz R, Augustus M, Carter K C, Crocker P R
The Wellcome Trust Building, Department of Biochemistry, University of Dundee, Dundee, Scotland, UK; the Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK; and Human Genome Sciences Inc, Rockville, MD, USA.
Blood. 1998 Sep 15;92(6):2123-32.
We describe the characterization of siglec-5 (sialic acid-binding Ig-like lectin-5), a novel transmembrane member of the immunoglobulin superfamily, highly related to the myeloid antigen, CD33. A full-length cDNA encoding siglec-5 was isolated from a human activated monocyte cDNA library. Sequencing predicted that siglec-5 contains four extracellular immunoglobulin-like domains, the N-terminal two of which are 57% identical to the corresponding region of CD33. The cytoplasmic tail is also related to that of CD33, containing two tyrosine residues embodied in immunoreceptor tyrosine-based inhibitory motif-like motifs. The siglec-5 gene was shown to map to chromosome 19q13.41-43, closely linked to the CD33 gene. When siglec-5 was expressed on COS cells or as a recombinant protein fused to the Fc region of human IgG1, it was able to mediate sialic acid-dependent binding to human erythrocytes and soluble glycoconjugates, suggesting that it may be involved in cell-cell interactions. By using specific antibodies, siglec-5 was found to have an expression pattern distinct from that of CD33, being present at relatively high levels on neutrophils but absent from leukemic cell lines representing early stages of myelomonocytic differentiation. Western blot analysis of neutrophil lysates indicated that siglec-5 exists as a disulfide-linked dimer of approximately 140 kD.
我们描述了唾液酸结合免疫球蛋白样凝集素5（siglec-5）的特征，它是免疫球蛋白超家族的一个新型跨膜成员，与髓系抗原CD33高度相关。从人活化单核细胞cDNA文库中分离出编码siglec-5的全长cDNA。测序预测siglec-5含有四个细胞外免疫球蛋白样结构域，其中N端的两个结构域与CD33的相应区域有57%的同源性。其胞质尾部也与CD33的胞质尾部相关，含有两个基于免疫受体酪氨酸的抑制基序样基序中的酪氨酸残基。siglec-5基因定位于19号染色体q13.41-43，与CD33基因紧密连锁。当siglec-5在COS细胞上表达或作为与人IgG1的Fc区融合的重组蛋白表达时，它能够介导唾液酸依赖性与人红细胞和可溶性糖缀合物的结合，这表明它可能参与细胞间相互作用。通过使用特异性抗体，发现siglec-5具有与CD33不同的表达模式，在中性粒细胞上相对高水平存在，但在代表髓单核细胞分化早期阶段的白血病细胞系中不存在。中性粒细胞裂解物的蛋白质印迹分析表明，siglec-5以约140 kD的二硫键连接二聚体形式存在。
