AKT Signaling and Oxidative Stress Regulation of Erythropoiesis

描述(申请人提供)：红系细胞分裂和成熟的紧密协调对于红系细胞的日常生产和对需要应激性红系生成的临床条件的即时反应是必需的。成熟的红系祖细胞和早期的红系祖细胞(红系前体)高度增殖，而后期增殖急剧下降。阐明调节红系细胞分化和成熟的分子途径对于设计针对包括红白血病、地中海贫血S和真性红细胞增多症在内的多种红系疾病的靶向治疗至关重要。促红细胞生成素(EPO)与其受体促红细胞生成素受体(EPOR)结合产生的信号是由JAK2酪氨酸激酶介导的，对正常的红细胞发育是必不可少的。虽然EPOR信号在调节红系细胞存活和细胞分裂中的作用已经被广泛研究，但EPOR信号对红系细胞分化和成熟的转录程序的影响还不是很清楚。特别是，对协调红系前体细胞分裂、细胞周期退出以及分化和成熟的分子机制知之甚少。我们实验室的证据表明，AKT丝氨酸苏氨酸蛋白激酶在EPOR信号下游调节红系细胞分裂和成熟过程中发挥重要作用。我们发现AKT对GATA-1和FOXO_3转录因子和mTOR激酶的调节是协调红系细胞分裂和成熟的关键。此外，我们的研究支持AKT靶标FOXO_3对生理活性氧物种(ROS)的调节在红细胞成熟过程中起重要作用的观点。ROS被认为在许多红系疾病中起关键作用，包括在地中海贫血红细胞生成中。因此，我们提出了一个模型，在该模型中，AKT下游的信号，特别是FOXO_3、mTOR和GATA-1协调红系前体细胞的分裂和成熟，这种协调至少部分是由ROS介导的。目的1：探讨FOXO_3在应激性红细胞生成反应中的作用；目的2：阐明野生型和FOXO_3基因缺失小鼠红系细胞增殖的分子机制；AKT对GATA-1的调控机制。在这些实验中，我们将评估ROS的贡献和mTOR的作用。最后，我们将研究FOXO_3在地中海贫血中的潜在作用。这些研究的结果将提供有关红系细胞分裂和成熟调节机制的关键信息，并应有助于阐明红细胞生成的基本方面。公共卫生相关性：在这项建议中，我们研究了AKT信号通路和氧化应激在调节红系细胞形成中的作用。这些研究将对我们理解不同类型贫血的机制以及如何增加红细胞生成产生关键影响。

DESCRIPTION (provided by applicant): A tight coordination of erythroid cell division and maturation is required for daily production of erythroid cells and for immediate response to clinical conditions in which stress erythropoiesis is in demand. Mature erythroid progenitors and early erythroblasts (erythroid precursors) are highly proliferative, while proliferation decreases sharply in later stages. Elucidating molecular pathways that regulate erythroid cell differentiation and maturation is critical for devising targeted treatments for a number of erythroid disorders including erythroleukemias, thalassemia s, and polycythemia vera. Signals generated from Erythropoietin (Epo) binding to its receptor erythropoietin receptor (EpoR) are mediated by JAK2 tyrosine kinase and are essential for normal erythroid cell development. Although the function of EpoR signaling in the regulation of erythroid survival and cell division has been characterized extensively, the impact of EpoR signaling on the transcriptional program of erythroid cell differentiation and maturation is less well understood. Particularly, not much is known about molecular mechanisms that coordinate erythroid precursor cell division, cell cycle exit, and differentiation and maturation. Evidence from our laboratory suggests that AKT serine threonine protein kinase mediates significant functions in the regulation of erythroid cell division and maturation downstream of EpoR signaling. We have identified AKT regulation of GATA-1 and FoxO3 transcription factors and mTOR kinase as critical for coordination of erythroid cell division and maturation. In addition our studies support the notion that regulation of physiological reactive oxygen species (ROS) by AKT target FoxO3 plays a significant role in erythroid cell maturation. ROS is thought to play a critical role in many erythroid disorders including in ¿-thalassemic erythropoiesis. Thus we propose a model in which signals downstream of AKT, specifically FoxO3, mTOR and GATA-1 coordinate erythroid precursor cell division and maturation and that this coordination is mediated at least in part by ROS. To investigate the validity of this model we propose the following aims: Aim 1: To investigate the role of FoxO3 in response to stress erythropoiesis; Aim 2: To elucidate the molecular mechanisms of erythroid cell proliferation in wild type and FoxO3 null mice; To investigate the mechanisms of AKT regulation of GATA-1. In these experiments we will evaluate the contribution of ROS and the role of mTOR. Finally we will examine the potential function of FoxO3 in ¿- thalassemia. Results from these studies will provide critical information on mechanisms of regulation of erythroid cell division and maturation, and should shed light on fundamental aspects of erythropoiesis. PUBLIC HEALTH RELEVANCE: In this proposal we investigate the function of AKT signaling pathway and oxidative stress in the regulation of erythroid cell formation. These studies will have a critical impact on our understanding of mechanisms of different types of anemias and how to increase red blood cell production.