The roles of pleckstrin-2 as a functional node in erythropoiesis

 描述(申请人提供)：过去几十年的研究揭示了促红细胞生成素(EPO)和RAC GTP酶信号通路中的许多关键因素，这些信号通路对各种红细胞相关疾病的发展至关重要。然而，许多其他红系疾病的发病机制仍不清楚，如先天性红细胞生成性贫血、Fanconi贫血、铁粒母细胞贫血、老年人原因不明的贫血、β-地中海贫血的无效红细胞生成以及骨髓增生异常综合征。这些疾病通常在细胞分化、存活和肌动蛋白动力学方面表现出无法解释的缺陷，模仿 EPO和/或RAC GTP酶途径。然而，到目前为止，在这些疾病中还没有关于EPO或RAC GTP酶途径的直接缺陷的报道。该领域的一个悬而未决的问题是，是否有任何蛋白质或途径连接EPO和RAC GTP酶途径来调节终末红细胞生成，这可能参与上述疾病的发病机制。在这项工作中，我们发现pleckstrin-2(Plek2)通过与cofilin的相互作用在终末红细胞生成的不同阶段发挥关键作用。我们的初步数据和其他研究小组的报告表明，plek2与EPO和Rac GTP酶途径密切相关，调节红系细胞的分化、存活和肌动蛋白动态，形成一个红细胞生成的全球调控网络。在这个项目中，我们将利用我们成熟的小鼠胎儿红细胞培养系统和各种小鼠模型，在体外和体内确定plek2作为一个功能节点在红细胞生成中的作用。在目的1中，我们将通过建立大细胞性贫血和胎儿性贫血的plek2基因敲除小鼠模型，研究在稳态和应激条件下，plek2在体内红细胞生成中的作用。也将使用Hbbth1/Th1小鼠作为plek2的直接红细胞疾病模型来测试plek2在β-地中海贫血发病机制中的作用。在目标2中，我们将确定EPO信号通路转录或翻译后修饰调控plek2的机制。在目标3中，我们将确定在终末红细胞生成的不同阶段，plek2-cofilin和Rac GTP酶途径相互需要的程度。这些独立但相互关联的目标的成功实现将揭示plek2在调节红细胞生成中的细胞分化、存活和肌动蛋白动力学中的核心作用，这可能为病因不明的红细胞相关疾病的发病机制和治疗提供新的见解。

 DESCRIPTION (provided by applicant): Research in the past few decades has revealed many key factors in erythropoietin (Epo) and Rac GTPase signaling pathways that are important for the development of various red blood cell related diseases. However, the pathogenesis of many other erythroid disorders, such as congenital dyserythropoietic anemias, Fanconi anemia, sideroblastic anemia, unexplained anemia of the elderly, ineffective erythropoiesis in beta-thalassemia, and myelodysplastic syndromes, remain unclear. These diseases often show unexplained defects in cell differentiation, survival, and actin dynamics that mimic disruptions of Epo and/or Rac GTPase pathways. However, no direct defects in Epo or Rac GTPase pathways have been reported to date in these diseases. An open question in the field is whether there are any proteins or pathways that link Epo and Rac GTPase pathways to regulate terminal erythropoiesis, which could be involved in the pathogenesis of aforementioned diseases. In this effort, we discovered that pleckstrin-2 (plek2) plays a critical role in different stages of terminl erythropoiesis through the interaction with cofilin. Our preliminary data and reports from other groups indicated that plek2 is closely interrelated with Epo and Rac GTPase pathways to regulate erythroid cell differentiation, survival and actin dynamics to form a global regulatory network in erythropoiesis. In this project, we will determine the roles of plek2 as a functional node in erythropoiesis in vitro and in vivo using our well-established mouse fetal erythroblast culture system and various mouse models. In Aim 1, we will use plek2 knockout mouse model, which showed macrocytic anemia and fetal anemia, to determine the functions of plek2 in erythropoiesis in vivo under steady state and stress conditions. The role of plek2 in the pathogenesis of beta-thalassemia will also be tested using Hbbth1/th1 mice as a direct red cell disease model for plek2. In Aim 2, we will determine the mechanisms by which plek2 is regulated by Epo signaling pathways transcriptionally or through post-translational modifications. In Aim 3, we will determine the extent to which plek2-cofilin and Rac GTPase pathways are reciprocally required in different stages of terminal erythropoiesis. Successful accomplishment of these independent but interconnected aims will reveal a central role of plek2 in regulating cell differentiation, survival and actin dynamics in erythropoiesis, which could provide novel insights into the pathogenesis and therapeutic management of red cell related diseases with unclear etiology.