Gebe J A, Llewellyn M, Hoggatt H, Aruffo A
The Bristol-Myers Squibb, Pharmaceutical Research Institute, Princeton, NJ 08543-4000, USA.
Immunology. 2000 Jan;99(1):78-86. doi: 10.1046/j.1365-2567.2000.00903.x.
Several group B scavenger receptor cysteine-rich (SRCR) proteins have been shown to function as modulators in the immune response. Recently, we reported the cloning of a new member of this family, human Spalpha (hSpalpha). Herein we report the cloning and characterization of the mouse homologue of hSpalpha. Like its human counterpart, mouse Spalpha (mSpalpha), is a secreted protein containing three SRCR domains. Most lymphoid tissues express RNA transcripts encoding mSpalpha. Characterization of a genomic clone encoding the mature mSpalpha protein showed that each of the SRCR domains of mSpalpha is encoded by a single exon. Comparison of the sequence of mSPalpha with those of other published proteins indicates that it is the same as the recently reported protein named AIM (apoptosis inhibitor expressed by macrophages). Cell-binding studies with a mSpalpha immunoglobulin (mSpalpha-Rgamma) fusion protein indicated that mSpalpha is capable of binding to spleen-derived CD19+ B cells and minimally to peritoneal cavity-derived CD19+ B cells but not to peripheral blood-derived B cells. Spleen-derived CD3+ T cells also bound mSpalpha-Rgamma; however, no binding was observed to either peripheral blood mononuclear cells or peritoneal cavity-derived CD3+ T cells. The mSpalpha-Rgamma fusion protein was also shown to bind to the mouse cell lines WEHI3 (monocytic) and EL-4 (thymoma, T cell). The cloning of cDNA and genomic clones encoding mSpalpha and the identification of cells expressing a putative mSpalpha receptor(s) should facilitate in vivo studies designed to investigate the function of Spalpha in the immune compartment.
几种B族富含半胱氨酸的清道夫受体（SRCR）蛋白已被证明在免疫反应中起调节作用。最近，我们报道了该家族一个新成员——人Spalpha（hSpalpha）的克隆。在此，我们报道hSpalpha小鼠同源物的克隆与特性。与人类对应物相似，小鼠Spalpha（mSpalpha）是一种含有三个SRCR结构域的分泌蛋白。大多数淋巴组织表达编码mSpalpha的RNA转录本。对编码成熟mSpalpha蛋白的基因组克隆的特性分析表明，mSpalpha的每个SRCR结构域都由一个外显子编码。mSPalpha与其他已发表蛋白序列的比较表明，它与最近报道的名为AIM（巨噬细胞表达的凋亡抑制剂）的蛋白相同。用mSpalpha免疫球蛋白（mSpalpha-Rgamma）融合蛋白进行的细胞结合研究表明，mSpalpha能够结合脾脏来源的CD19+B细胞，对腹腔来源的CD19+B细胞结合最少，但不结合外周血来源的B细胞。脾脏来源的CD3+T细胞也能结合mSpalpha-Rgamma；然而，未观察到其与外周血单个核细胞或腹腔来源的CD3+T细胞结合。mSpalpha-Rgamma融合蛋白也被证明能结合小鼠细胞系WEHI3（单核细胞系）和EL-4（胸腺瘤，T细胞系）。编码mSpalpha的cDNA和基因组克隆的克隆以及表达假定的mSpalpha受体的细胞的鉴定，应有助于开展旨在研究Spalpha在免疫区室中功能的体内研究。
