AKT Signaling and Oxidative Stress Regulation of Erythropoiesis

描述（由申请人提供）：需要红细胞分裂和成熟的紧密协调，用于红细胞的日常生产和对需要应激性红细胞生成的临床条件的即时反应。成熟的红系祖细胞和早期的红母细胞（红系前体）具有高度的增殖能力，而在后期增殖能力急剧下降。阐明调节红细胞分化和成熟的分子途径对于设计针对许多红细胞疾病（包括红细胞白血病、地中海贫血和真性红细胞增多症）的靶向治疗至关重要。促红细胞生成素（Epo）结合其受体EpoR产生的信号是由JAK2酪氨酸激酶介导的，是正常红细胞发育所必需的。虽然EpoR信号在红细胞存活和细胞分裂调控中的作用已被广泛研究，但EpoR信号对红细胞分化和成熟转录程序的影响尚不清楚。特别是，对协调红细胞前体细胞分裂、细胞周期退出、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信号下游的红细胞分裂和成熟调节中起重要作用。我们已经发现AKT调控GATA-1和FoxO3转录因子和mTOR激酶对红细胞分裂和成熟的协调至关重要。此外，我们的研究支持AKT靶点FoxO3调控生理性活性氧（ROS）在红细胞成熟中起重要作用的观点。ROS被认为在包括地中海贫血性红细胞生成在内的许多红细胞疾病中起关键作用。因此，我们提出了AKT下游信号，特别是FoxO3， mTOR和GATA-1协调红细胞前体细胞分裂和成熟的模型，并且这种协调至少部分由ROS介导。为了验证该模型的有效性，我们提出以下目标：目的1：研究FoxO3在应激性红细胞生成中的作用；目的2：探讨野生型和FoxO3缺失小鼠红细胞增殖的分子机制；探讨AKT调控GATA-1的机制。在这些实验中，我们将评估活性氧的贡献和mTOR的作用。最后，我们将研究FoxO3在地中海贫血中的潜在功能。这些研究的结果将为红细胞分裂和成熟的调控机制提供重要信息，并应阐明红细胞生成的基本方面。公共卫生相关性：在本研究中，我们研究AKT信号通路和氧化应激在红细胞形成调控中的作用。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的产生产生关键影响。

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.