Martens C L, Jardieu P, Trounstine M L, Stuart S G, Ishizaka K, Moore K W
Proc Natl Acad Sci U S A. 1987 Feb;84(3):809-13. doi: 10.1073/pnas.84.3.809.
We have investigated expression of an IgE-binding factor (IgE-BF) cDNA in both COS-7 monkey kidney cells and Chinese hamster ovary cells. Transient expression of the IgE-BF clone in either cell type yielded IgE-BF, which potentiated an in vitro IgE response and had an affinity for lentil lectin. In contrast, when the transient expression experiments were carried out in the presence of tunicamycin, the factors no longer bound to lentil lectin. Moreover, IgE-BF expressed under these conditions suppressed an in vitro IgE response. IgE-BF lacking affinity for lentil lectin and suppressing the IgE response also resulted from transient expression of the IgE-BF gene in the presence of glycosylation inhibiting factor, a phospholipase inhibitory protein. Thus, IgE-BF that either potentiate or suppress the IgE response can be expressed from a single cloned gene; the difference in biological activities appears to be determined principally by the type of glycosylation of the common polypeptide chain. Previous work showed that IgE-BF bears an antigenic determinant recognized by the anti-Ia monoclonal antibody OX3. IgE-BF produced in the presence of tunicamycin, and IgE-BF expressed from a mutant cDNA lacking one of two carbohydrate-attachment sites, lacked the OX3 determinant. Thus, the OX3 determinant on IgE-BF appears to be associated with a site of N-linked glycosylation.
我们研究了IgE结合因子（IgE-BF）cDNA在COS-7猴肾细胞和中国仓鼠卵巢细胞中的表达。IgE-BF克隆在这两种细胞类型中的瞬时表达均产生了IgE-BF，其增强了体外IgE反应并对扁豆凝集素具有亲和力。相反，当在衣霉素存在下进行瞬时表达实验时，这些因子不再与扁豆凝集素结合。此外，在这些条件下表达的IgE-BF抑制了体外IgE反应。在糖基化抑制因子（一种磷脂酶抑制蛋白）存在下，IgE-BF基因的瞬时表达也导致了对扁豆凝集素缺乏亲和力且抑制IgE反应的IgE-BF产生。因此，增强或抑制IgE反应的IgE-BF均可从单个克隆基因表达；生物活性的差异似乎主要由共同多肽链的糖基化类型决定。先前的研究表明，IgE-BF带有抗Ia单克隆抗体OX3识别的抗原决定簇。在衣霉素存在下产生的IgE-BF，以及从缺少两个碳水化合物连接位点之一的突变cDNA表达的IgE-BF，均缺乏OX3决定簇。因此，IgE-BF上的OX3决定簇似乎与N-连接糖基化位点相关。
