Huang Huei-Mei, Chiou Huei-Yu, Chang Ju-Ling
Graduate Institute of Cell and Molecular Biology, Taipei Medical University, Taipei, Taiwan.
J Cell Biochem. 2006 Jul 1;98(4):789-97. doi: 10.1002/jcb.20713.
Activin A, a member of the transforming growth factor (TGF)-beta superfamily, is involved in the regulation of erythroid differentiation. Previous studies have shown that activin A inhibited the colony-forming activity of mouse Friend erythroleukemia cells, however, the mechanism remains unknown. First, we show herein that activin A induced the expression and activated the promoters of alpha-globin and zeta-globin in K562 cells, confirming that activin A induces erythroid differentiation in K562 cells. The p38 mitogen activated protein kinase (MAPK) inhibitor, SB203580, inhibited and the extracellular signal regulated kinase (ERK) inhibitor, PD98059, enhanced the expression and promoter activities of alpha-globin and zeta-globin by activin A, indicating that p38 MAPK and ERK are crucial for activin A-induced erythroid genes expression. Second, SB203580 inhibited the inhibitory effect of activin A on the colony-forming activity of K562 cells using the methylcellulose colony assay, indicating that activin A inhibits K562 colony formation by activating p38 MAPK. In addition, mitogenic cytokines SCF, IL-3, and GM-CSF induced colony formation of K562 cells that could be inhibited by PD98059 or enhanced by SB203580, respectively, indicating that these mitogenic cytokines induce K562 colony formation by activating ERK and inactivating p38 MAPK. Furthermore, activin A reduced the induction effect of these mitogenic cytokines on K562 colony formation in a dose-dependent manner. The inhibition of p38 MAPK reverted the inhibitory effect of activin A on mitogenic cytokine-mediated K562 colony formation. We conclude that activin A can regulate the same pathway via p38 MAPK to coordinate cell proliferation and differentiation of K562 cells.
激活素A是转化生长因子（TGF）-β超家族的成员之一，参与红系分化的调控。先前的研究表明，激活素A可抑制小鼠弗氏红白血病细胞的集落形成活性，但其机制尚不清楚。首先，我们在此表明，激活素A可诱导K562细胞中α-珠蛋白和ζ-珠蛋白的表达并激活其启动子，证实激活素A可诱导K562细胞发生红系分化。p38丝裂原活化蛋白激酶（MAPK）抑制剂SB203580可抑制激活素A诱导的α-珠蛋白和ζ-珠蛋白的表达及启动子活性，而细胞外信号调节激酶（ERK）抑制剂PD98059则可增强激活素A诱导的α-珠蛋白和ζ-珠蛋白的表达及启动子活性，这表明p38 MAPK和ERK对激活素A诱导的红系基因表达至关重要。其次，使用甲基纤维素集落试验，SB203580可抑制激活素A对K562细胞集落形成活性的抑制作用，这表明激活素A通过激活p38 MAPK来抑制K562细胞的集落形成。此外，促有丝分裂细胞因子SCF、IL-3和GM-CSF可诱导K562细胞形成集落，而PD98059可分别抑制其形成，SB203580则可增强其形成，这表明这些促有丝分裂细胞因子通过激活ERK和使p38 MAPK失活来诱导K562细胞形成集落。此外，激活素A可呈剂量依赖性地降低这些促有丝分裂细胞因子对K562细胞集落形成的诱导作用。抑制p38 MAPK可逆转激活素A对促有丝分裂细胞因子介导的K562细胞集落形成的抑制作用。我们得出结论，激活素A可通过p38 MAPK调节相同的信号通路，以协调K562细胞的增殖和分化。
