Shao L, Frigon N L, Young A L, Yu A L, Mathews L S, Vaughan J, Vale W, Yu J
Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, CA 92037.
Blood. 1992 Feb 1;79(3):773-81.
The regulatory control of human erythropoiesis through a purified protein, activin A, was examined. Previous studies using mixed populations of bone marrow cells suggested that activin A has an indirect effect on cellular proliferation and DNA synthesis of erythroid progenitors through the mediation of accessory cells. In present studies, the cultures of purified erythroid progenitors were used to examine the effect of activin A on globin gene expression. Human erythroid burst-forming units (BFU-E) were partially purified from peripheral blood, and after 8 days of culture the cells generated consisted mainly of erythroid colony-forming units (CFU-E). It was found that the subsequent 7-day cultures of these purified progenitors yielded similar numbers and size distributions of erythroid colonies, regardless of the presence of activin A in the cultures. In addition, these erythroid progenitor cells were responsive, in terms of stimulation of DNA synthesis, to the addition of erythropoietin, but not to treatment by activin A. Therefore, once the erythroid progenitors are depleted of accessory cells, activin A has little effect on both the proliferation and the DNA synthesis of these progenitors. However, when these purified erythroid progenitors were cultured in the presence of activin A, the levels of all alpha, beta, and epsilon globin transcripts and hemoglobins were significantly increased. In addition, disuccinimidyl suberate was found to chemically cross-link 125I-activin A to cell surface binding proteins (45 to 54 Kd) in both purified erythroid progenitors and K562 cells. The labeling of these binding proteins was specifically inhibited by the presence of unlabeled activin A, but not transforming growth factor-beta. These results suggest that, in addition to its indirect effect on DNA synthesis and cellular proliferation of erythroid progenitors, activin A directly affects the levels of globin mRNAs and hemoglobins in developing human erythroid cells through its specific surface binding receptor(s).
研究了通过纯化蛋白激活素A对人类红细胞生成的调控作用。以往使用骨髓细胞混合群体的研究表明，激活素A通过辅助细胞的介导对红系祖细胞的细胞增殖和DNA合成有间接影响。在本研究中，使用纯化的红系祖细胞培养物来检测激活素A对珠蛋白基因表达的影响。从外周血中部分纯化人红系爆式集落形成单位（BFU-E），培养8天后产生的细胞主要由红系集落形成单位（CFU-E）组成。结果发现，这些纯化祖细胞随后7天的培养产生的红系集落数量和大小分布相似，无论培养物中是否存在激活素A。此外，这些红系祖细胞在DNA合成刺激方面对促红细胞生成素的添加有反应，但对激活素A的处理无反应。因此，一旦红系祖细胞去除辅助细胞，激活素A对这些祖细胞的增殖和DNA合成几乎没有影响。然而，当这些纯化的红系祖细胞在激活素A存在的情况下培养时，所有α、β和ε珠蛋白转录本及血红蛋白的水平均显著增加。此外，发现辛二酸双琥珀酰亚胺酯可将125I-激活素A化学交联至纯化红系祖细胞和K562细胞中的细胞表面结合蛋白（45至54 Kd）。未标记的激活素A的存在可特异性抑制这些结合蛋白的标记，但转化生长因子-β则无此作用。这些结果表明，激活素A除了对红系祖细胞的DNA合成和细胞增殖有间接影响外，还通过其特异性表面结合受体直接影响发育中的人类红细胞中珠蛋白mRNA和血红蛋白的水平。
