Department of Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, New York, 10029.
Am J Hematol. 2014 Oct;89(10):954-63. doi: 10.1002/ajh.23786. Epub 2014 Jul 22.
Ineffective erythropoiesis is observed in many erythroid disorders including β-thalassemia and anemia of chronic disease in which increased production of erythroblasts that fail to mature exacerbate the underlying anemias. As loss of the transcription factor FOXO3 results in erythroblast abnormalities similar to the ones observed in ineffective erythropoiesis, we investigated the underlying mechanisms of the defective Foxo3(-/-) erythroblast cell cycle and maturation. Here we show that loss of Foxo3 results in overactivation of the JAK2/AKT/mTOR signaling pathway in primary bone marrow erythroblasts partly mediated by redox modulation. We further show that hyperactivation of mTOR signaling interferes with cell cycle progression in Foxo3 mutant erythroblasts. Importantly, inhibition of mTOR signaling, in vivo or in vitro enhances significantly Foxo3 mutant erythroid cell maturation. Similarly, in vivo inhibition of mTOR remarkably improves erythroid cell maturation and anemia in a model of β-thalassemia. Finally we show that FOXO3 and mTOR are likely part of a larger metabolic network in erythroblasts as together they control the expression of an array of metabolic genes some of which are implicated in erythroid disorders. These combined findings indicate that a metabolism-mediated regulatory network centered by FOXO3 and mTOR control the balanced production and maturation of erythroid cells. They also highlight physiological interactions between these proteins in regulating erythroblast energy. Our results indicate that alteration in the function of this network might be implicated in the pathogenesis of ineffective erythropoiesis.
无效造血在许多红细胞疾病中都有观察到,包括β-地中海贫血和慢性病性贫血,其中红细胞生成增加但未能成熟,从而加重了基础贫血。由于转录因子 FOXO3 的缺失会导致红细胞前体细胞出现类似于无效造血中观察到的异常,因此我们研究了 Foxo3(-/-) 红细胞前体细胞周期和成熟缺陷的潜在机制。在这里,我们发现 Foxo3 的缺失导致了原发性骨髓红细胞中 JAK2/AKT/mTOR 信号通路的过度激活,部分是由氧化还原调节介导的。我们进一步表明,mTOR 信号的过度激活会干扰 Foxo3 突变红细胞前体细胞的细胞周期进程。重要的是,体内或体外抑制 mTOR 信号显著增强 Foxo3 突变红细胞的成熟。同样,在β-地中海贫血模型中,体内抑制 mTOR 可显著改善红细胞成熟和贫血。最后,我们发现 FOXO3 和 mTOR 可能是红细胞中更大代谢网络的一部分,因为它们共同控制着一系列代谢基因的表达,其中一些基因与红细胞疾病有关。这些综合发现表明,以 FOXO3 和 mTOR 为中心的代谢调节网络控制着红细胞的平衡生成和成熟。它们还突出了这些蛋白质在调节红细胞能量方面的生理相互作用。我们的研究结果表明,该网络功能的改变可能与无效造血的发病机制有关。