人重组IL-3受体α链片段的表达及其对TF-1细胞的刺激活性

Expression of human interleukin 3 receptor α chain receptor extracellular fragments in E.coli and analysis of their stimulating effect on TF 1 cells

ＩＬ－３是一种造血生长因子，通过其受体α和β两条链向细胞内传递信号。为研究ＩＬ－３，ＩＬ－３Ｒα，β三者之间的相互作用模式，利用大肠杆菌系统表达了４种ＩＬ－３Ｒα胞外片段：ＩＬ－３Ｒ－Ｐ（氨基酸１～３０７），ＩＬ－３Ｒ－２（１～２６３），ｎＩＬ－３Ｒ－２（１～７５），ｃＩＬ－３Ｒ（１０５～２６３）。活性研究发现，除ｎＩＬ－３Ｒ－２外，其余３个片段对ＩＬ－３依赖性细胞株ＴＦ－１有不同程度的刺激活性，并且ＦＩＴＣ标记的ＩＬ－３Ｒ－Ｐ可与ＴＦ－１细胞结合，βｃ真核表达质粒转染ＣＴＬＬ细胞后，ＦＩＴＣ标记的ＩＬ－３Ｒ－Ｐ可与之结合。实验结果提示ＩＬ－３Ｒα链存在潜在的β链结合位点，一旦暴露可以激活β链传递信号。

Interleukin 3 is a hematopoietic growth factor that transduces signals through its receptor composed of α and β chains.To reveal the mode of the interactions among the IL 3,IL 3Rα and β chains,four different segments of IL 3Rα extracellular part were expressed in E.coli :IL 3R P(amino acids 1 307),IL 3R 2(1 263),nIL 3R 2(1 75),and cIL 3R 2(105 263).Bioassay showed that except nIL 3R 2 all of the fragments had some degree of stimulating effects on IL 3 dependent TF 1 cell line.FITC labelled IL 3R P could bind to TF 1 cells and CTLL 2 cells transfected with βc expressing plasmid pcDI βc.It implicated that IL 3Rα had some latent binding sites,once exposed,they could switch on βc to induce signal cascade.IL 3Rα cytoplasmic domain might not take great part in cellular growth signal.