Liu Yunchao, Wang Aiping, Qiao Songlin, Zhang Gaiping, Xi Jun, You Leiming, Tian Xiaohui, Li Qiaomu, Zhang Lina, Guo Junqing
Key Laboratory of Animal Immunology of the Ministry of Agriculture, Henan Provincial Key Laboratory of Animal Immunology, Henan Academy of Agricultural Sciences, Zhengzhou 450002, China.
Vet Immunol Immunopathol. 2010 Feb 15;133(2-4):243-9. doi: 10.1016/j.vetimm.2009.07.020. Epub 2009 Aug 8.
Immunoglobulin G (IgG) Fc receptors (FcgammaRs) bind to immune complexes through interactions with the Fc region of IgG to initiate or inhibit the defense mechanism of the leukocytes on which they are expressed. In this study, we describe the cloning, sequencing and characterization of ovine FcgammaRII. By screening a translated expression sequence tag (EST) database with the protein sequence of bovine IgG Fc receptor II, we identified a putative ovine homologue. Using rapid amplification of cDNA ends (RACE), we isolated the cDNA encoding ovine FcgammaRII from peripheral blood leucocyte RNA. The ovine FcgammaRII cDNA contains an 894bp open-reading frame, encoding a 297 amino acid transmembrane glycoprotein composed of two immunoglobulin-like extracellular domains, a transmembrane region and a cytoplasmic tail with an immunoreceptor tyrosine-based inhibitory motif (ITIM). The glycoprotein encoded by the cloned cDNA was then expressed on the surface of COS-7 cells and immunoglobulin-binding assays show that it binds ovine IgG1, but not IgG2. Identification of the ovine FcgammaRII will aid in the understanding of the molecular basis of IgG-FcgammaR interaction.
免疫球蛋白G（IgG）Fc受体（FcγRs）通过与IgG的Fc区域相互作用来结合免疫复合物，从而启动或抑制其表达所在白细胞的防御机制。在本研究中，我们描述了绵羊FcγRII的克隆、测序及特性分析。通过用牛IgG Fc受体II的蛋白质序列筛选翻译后的表达序列标签（EST）数据库，我们鉴定出一个推定的绵羊同源物。利用cDNA末端快速扩增（RACE）技术，我们从外周血白细胞RNA中分离出编码绵羊FcγRII的cDNA。绵羊FcγRII cDNA包含一个894bp的开放阅读框，编码一个由两个免疫球蛋白样细胞外结构域、一个跨膜区域和一个带有基于免疫受体酪氨酸的抑制基序（ITIM）的细胞质尾巴组成的297个氨基酸的跨膜糖蛋白。然后，克隆cDNA编码的糖蛋白在COS-7细胞表面表达，免疫球蛋白结合试验表明它能结合绵羊IgG1，但不能结合IgG2。绵羊FcγRII的鉴定将有助于理解IgG-FcγR相互作用的分子基础。
