Devos R, Plaetinck G, Van der Heyden J, Cornelis S, Vandekerckhove J, Fiers W, Tavernier J
Roche Research Gent, Belgium.
EMBO J. 1991 Aug;10(8):2133-7. doi: 10.1002/j.1460-2075.1991.tb07747.x.
The mouse interleukin-5 receptor (mIL-5R) consists of two components one of which, the mIL-5R alpha-chain, binds mIL-5 with low affinity. Recently we demonstrated that monoclonal antibodies (Mabs) recognizing the second mIL-5R beta-chain, immunoprecipitate a p130-140 protein doublet which corresponds to the mIL-3R and the mIL-3R-like protein, the latter chain for which so far no ligand has been identified. In this study we show that a high affinity mIL-5R can be reconstituted on COS1 cells by co-expression of the mIL-5R alpha-chain with the mIL-3R-like protein (beta-chain). Cross-linking of 125I-labeled mIL-5 to the COS1 cells co-transfected with both cDNAs revealed the same pattern as in B13 cells, i.e. two proteins of 60 and 130 kd which correspond to the low affinity mIL-5R alpha-chain and the mIL-3R-like protein, respectively. The dissociation rate of mIL-5 from this reconstituted high affinity site was lower than that of the low affinity site, whereas the association rate was unchanged. Nonetheless, the apparent dissociation constant (Kd) for this reconstituted receptor was still 10-fold higher than the Kd observed for B13 cells. Although the mIL-3R is greater than 90% homologous to the mIL-3R-like protein, no increase in affinity for mIL-5 was detected on COS1 cells co-transfected with the cDNAs for the mIL-5R alpha-chain and the mIL-3R protein.
小鼠白细胞介素-5受体（mIL-5R）由两个亚基组成，其中之一，即mIL-5Rα链，以低亲和力结合mIL-5。最近我们证明，识别第二条mIL-5Rβ链的单克隆抗体（Mabs）免疫沉淀出一个p130 - 140蛋白双峰，其对应于mIL-3R和mIL-3R样蛋白，到目前为止尚未鉴定出后者链的配体。在本研究中，我们表明通过mIL-5Rα链与mIL-3R样蛋白（β链）的共表达，可以在COS1细胞上重建高亲和力mIL-5R。将125I标记的mIL-5与同时转染了两种cDNA的COS1细胞进行交联，结果显示出与B13细胞相同的模式，即两种分别为60和130 kd的蛋白，它们分别对应于低亲和力mIL-5Rα链和mIL-3R样蛋白。mIL-5从这个重建的高亲和力位点的解离速率低于低亲和力位点，而结合速率不变。尽管如此，这个重建受体的表观解离常数（Kd）仍然比在B13细胞中观察到的Kd高10倍。虽然mIL-3R与mIL-3R样蛋白的同源性大于90%，但在用mIL-5Rα链和mIL-3R蛋白的cDNA共转染的COS1细胞上，未检测到对mIL-5的亲和力增加。
