全反式维甲酸诱导NB4细胞分化过程中IL-3受体系统表达变化

IL-3受体（IL-3R）是异源二聚体膜受体,由相应的α亚基（IL-3Rα,GM-CSFRα,IL-5Rα）和β共同亚基（hβc）组成,α亚基能够特异性与相应的配体结合,β共同亚基通过与相应α亚基组成高亲和力的受体,传递细胞信号,调节造血祖细胞的增殖与分化。为研究IL-3受体系统（IL-3Rα,GM-CSFRα和hβc）在髓系分化中的作用,采用实时定量RT-PCR检测全反式维甲酸（ATRA）诱导急性早幼粒细胞白血病（APL）细胞株NB4细胞分化过程IL-3Rα,GM-CSFRα和hβc的表达变化,同时应用DNA序列分析检测IL-3Rα,GM-CSFRα和hβc mRNA序列变化。结果显示：全反式维甲酸处理NB4细胞后,细胞发生分化,同时细胞增殖受抑制。ATRA作用24小时NB4细胞IL-3Rα mRNA表达水平显著下调,但随着细胞分化,其表达水平又逐渐恢复;而GM-CSFRα mRNA和hβc的mRNA表达水平则随着细胞分化逐渐上调。DNA序列分析表明,NB4细胞分化前后IL-3Rα和GM-CSFRα的mRNA序列没有变化,而NB4细胞分化前hβc的mRNA序列以截短突变为主,NB4细胞分化后hβc的mRNA序列以野生型为主。结论：NB4细胞存在IL-3受体异常表达,表现为高表达IL-3Rα和hβc的胞内区截短突变,两者在NB4细胞的过度增殖与分化受阻的过程起重要作用。

Expression Change of IL-3 Receptor System in All-trans Retinoic Acid Induced Differentiation of NB4 Cells

Interleukin-3 receptor （IL-3R） is a heterodimeric membrane receptor. The α subunit is essential for ligand binding and confers ligand specificity to the receptor.The common beta chain（βc ）subunit,which is shared by the gra-nulocyte macrophage-colony stimulating factor（GM-CSF）,IL-3 and IL-5 receptors,is required for high-affinity ligand binding and signal transduction,mediating growth and survival of hematopoietic progenitor cells and the production and activation of mature hematopoietic cells. In order to investigate the role of IL-3 receptor system（IL-3Rα,GM-CSFRα and hβc）in myeloid differentiation,the expression level of IL-3 receptor system gene in all-trans retinoic acid（ATRA）-induced NB4 cell differentiation was detected by quantitative real time RT-PCR. At the same time,DNA sequence change was analyzed by cDNA sequencing. The results showed that the expression level of IL-3Rα mRNA was obviously down-regulated in NB4 cells treated with ATRA for 24 hours,but during differentiation of ATRA induced NB4 cells,the expression level of IL-3Rα mRNA was gradually restored,while the expression levels of GM-CSFRα mRNA and hβc mRNA were gradually up-regulated. The sequence of IL-3Rα and GM-CSFRα gene did not change before and after NB4 cells differentiation,but the sequence of hβc gene changed when NB4 cells were treated with ATRA,the expression of hβc mRNA sequence before NB4 cell differentiation taken truncated mutation as dominant,as regards expression of hβc mRNA sequence after NB4 cell differentiation,the truncated mutation of hβc mRNA had restored to wild type. It is concluded that the IL-3 receptor abnormality exists in NB4 cells,over expression of IL-3Rα and truncated mutation of hβc may be involved in proliferation and differentiation block in NB4 cells.