Syk介导ROS信号传导在红细胞末期发育中的机制研究

Accounting for 83% of the total cell number in the body, red blood cells (RBCs) are responsible for the transportation of oxygen to every tissue. Diminished RBC number causes anemia that affects one third of the world population, resulting in an enormous economic burden. Learning the rules for manipulating RBC production will enable scalable generation of these therapeutically important cell types for treating disease and for transfusion. During the differentiation and maturation of RBCs from erythroid progenitors, reactive oxidative species (ROS) are produced because of iron metabolism that is important for hemoglobin synthesis. Yet, it remains unclear how ROS contribute towards erythroid terminal development. We recently discovered Spleen Tyrosine Kinase (Syk), a protein kinase, as a key component of the signaling cascades activated by ROS in mouse B cells, embryonic fibroblasts and chicken DT40 cells. To examine the role of Syk-mediated ROS signaling in erythroid development, we generated mice bearing either whole-body or erythroid-specific deletion of Syk. Syk knockout led to significantly decreased RBC numbers in embryonic and adult mice. Consistent with our mouse models, blockade of Syk function with a chemical inhibitor (R406) increased apoptosis of erythroid progenitors. Interestingly, Syk inhibition resulted in a decrease in cellular ROS production. Taken together, our preliminary data indicate that Syk is critical for the terminal erythropoiesis. Thus, we hypothesize that during erythroid development, the activation of Syk by ROS leads to the expression of the cell surface receptor TfR, which in turn, controls ROS levels. In this proposal, we will investigate the mechanistic underpinning of Syk as an important regulator for erythropoiesis under normal and stress conditions. Specifically, we will examine: (i) the cell autonomous feedback loop between Syk and ROS; (ii) how Syk contributes towards stress-induced erythropoiesis; (iii) the control of RBC lifespan by Syk; and (iv) how Syk regulates ROS production. Our findings will provide new insights into the role of Syk and ROS in erythropoiesis. Establishing Syk as an important regulator of ROS production and cell survival may allow for the development of therapeutic modalities that modulate Syk activity in anemia, as well as for the large-scale ex vivo production of RBCs for blood transfusion.

红细胞发育中伴随的血红素生成产生大量的活性氧（ROS）。 ROS促使红细胞前体凋亡，而红细胞通过FOXO3等信号途径拮抗活性氧。近来发现，除了细胞毒性，ROS还促进红细胞发育和增殖。但具体机制不清。我们研究证明在小鼠胚胎上皮细胞，B细胞和鸡DT40细胞中，活性氧通过脾酪氨酸激酶（Syk）激活下游信号途径。我们的前期实验证明，Syk全身敲除和红系专一敲除小鼠均出现贫血现象；而抑制Syk的活性降低红细胞前体的体外扩增和分化，影响血红素的生产，降低ROS产生。因此我们预计ROS通过SYK激活ROS反馈途径，并控制红细胞扩增和分化。为此，我们将利用Syk全身敲除和红系专一敲除小鼠研究Syk对红细胞末期体内发育，应激红细胞扩增和红细胞自主发育的影响。我们还将探寻Syk调节细胞ROS产生的信号途径。我们的结果将揭示在红细胞发育中，Syk介导ROS的反馈机制，并有助于贫血治疗和红细胞体外大量生产。

在终末红细胞生成中，红细胞生成素 (EPO) 激活几种激酶，包括脾胰蛋白酶激酶 (SYK)，以启动红细胞增殖，随后细胞周期退出和去核并成为网织红细胞。但是，SYK 在终末红细胞生成中的功能仍不清楚。在这里，我们证明了 SYK，一种在 EPO 模拟和活性 JAK2 和 LYN 的存在下被激活的早期激酶，在细胞周期退出中起着至关重要的作用。 SYK 的缺失导致小鼠胚胎出现严重贫血，成年小鼠出现慢性贫血，并伴有脾脏肿大的髓外红细胞生成。 SYK 缺乏会干扰体内胎儿肝脏中的红细胞生成缺陷和成人骨髓中的红细胞生成，并损害离体红细胞祖细胞的终末发育。 SYK 敲除导致不正确的细胞周期退出，并在体内和 MEL 细胞中增强 E2F 信号通路。总之，我们的研究揭示了 SYK 在 EPO 信号通路中调节终末红细胞生成过程中细胞周期退出的重要作用。我们的结果提供了关于细胞外信号如何控制终末分化细胞中细胞周期退出的机械见解。