AKT Signaling and Oxidative Stress Regulation of Erythropoiesis

描述（由申请人提供）：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红细胞生成的临床病症的立即响应是必需的。成熟的红系祖细胞和早期成红细胞（红系前体细胞）是高度增殖的，而增殖在后期急剧下降。阐明调节红系细胞分化和成熟的分子途径对于设计针对许多红系疾病的靶向治疗至关重要，所述红系疾病包括红白血病、地中海贫血和真性红细胞增多症。由促红细胞生成素（Epo）与其受体促红细胞生成素受体（EpoR）结合产生的信号由JAK 2酪氨酸激酶介导，并且对于正常红系细胞发育是必需的。虽然EpoR信号在红细胞存活和细胞分裂的调节中的功能已经被广泛表征，但是EpoR信号对红细胞分化和成熟的转录程序的影响还不太清楚。特别是，不太了解的分子机制，协调红系前体细胞分裂，细胞周期退出，分化和成熟。来自我们实验室的证据表明，AKT丝氨酸苏氨酸蛋白激酶介导的EpoR信号下游的红系细胞分裂和成熟的调节中的重要功能。我们已经确定AKT对加塔-1和FoxO 3转录因子和mTOR激酶的调节对于红系细胞分裂和成熟的协调至关重要。此外，我们的研究支持了AKT靶点FoxO 3对生理活性氧（ROS）的调节在红系细胞成熟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，包括地中海贫血性红细胞生成。因此，我们提出了一种模型，其中AKT下游的信号，特别是FoxO 3，mTOR和加塔-1协调红系前体细胞分裂和成熟，这种协调至少部分由ROS介导。为了研究该模型的有效性，我们提出了以下目的：目的1：研究FoxO 3在应激红细胞生成中的作用;目的2：阐明野生型和FoxO 3敲除小鼠红系细胞增殖的分子机制;研究加塔-1的AKT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功能。这些研究的结果将为红系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，我们探讨了AKT信号通路和氧化应激在红系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生成产生重要影响。

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.