The role of Pleckstrin-2 as a functional node in myeloid proliferation

项目总结 骨髓增生性肿瘤(MPN)是一组骨髓疾病，表现为髓系细胞过多。 发生血栓形成和演变为急性髓系白血病的风险增加的生产。V617F JAK2基因突变是引起MPNS的主要原因之一。这种突变的发现导致了 JAK抑制剂治疗MPN的研究进展。然而，JAK抑制剂并不能治愈。此外，MPN 使用JAK抑制剂治疗的患者通常会出现耐药性和严重的副作用，原因是 JAK2在正常造血中不可或缺的作用。我们一直在研究治疗MPN的新方法， 尤其关注JAK2途径的下游效应器。我们最近发表的研究资助了 目前的R01揭示了JAK2-STAT5途径的新靶点Pleckstrin-2(Plek2)的缺失， 改善JAK2V617F诱导的骨髓增殖表型，更重要的是逆转血管 JAK2V617F MPN小鼠模型的闭塞和致死性。鉴于Plek2在MPN中的重要性 发病机制，我们已经确定了Plek2小分子抑制剂的先导化合物，用于硅基高分子药物 吞吐量筛选和基于细胞的分析。我们新的未发表的初步数据进一步揭示了Plek2 与几个PI3K效应器结合，Plek2的缺失会降低Akt的激活。初步的活体证据也 证明Plek2在PI3K-Akt通路中是关键的，因为Plek2基因敲除改善了PI3K-Akt通路 并显著延长Pten造血特异性基因敲除小鼠的存活时间。这些 这些发现导致我们假设Plek2作为连接JAK2-STAT和PI3K-的中央枢纽- AKT途径和促进骨髓增殖。为了检验这一假说并研究其机制 Plek2的功能，我们将使用1)体外生化和分子研究来确定Plek2是如何增强 PI3K-Akt信号转导，2)Pten造血特异性基因敲除小鼠模型揭示Plek2的功能 在体内，以及3)临床前MPN模型和MPN患者样本，建立Plek2抑制剂的疗效。 该项目的成功完成将使人们对Plek2在糖尿病发病机制中的作用有新的见解。 并为将Plek2抑制剂作为单一药物或联合使用的临床试验奠定了基础 治疗MPN的其他化合物。

PROJECT SUMMARY Myeloproliferative neoplasms (MPNs) are a group of bone marrow diseases that show excessive myeloid cell production with an increased risk of developing thrombosis and evolving to acute myeloid leukemia. V617F driver mutation of JAK2 is one of the leading causes of MPNs. The discovery of this mutation led to the development of JAK inhibitors to treat MPNs. However, JAK inhibitors are not curative. In addition, MPN patients treated with JAK inhibitor often develop drug resistance and severe side effects due to the indispensable roles of JAK2 in normal hematopoiesis. We have been studying new approaches to treat MPNs, especially focusing on the downstream effectors of the JAK2 pathway. Our recently published studies funded by the current R01 revealed that loss of Pleckstrin-2 (Plek2), a novel target of the JAK2-STAT5 pathway, ameliorated JAK2V617F-induced myeloproliferative phenotypes, and more importantly reverted vascular occlusions and lethality of the JAK2V617F MPN mouse model. Given the significance of Plek2 in MPN pathogenesis, we have identified lead compounds of Plek2 small molecule inhibitors using in silico-based high- throughput screenings and cell-based assays. Our novel unpublished preliminary data further reveal that Plek2 binds to several PI3K effectors and loss of Plek2 reduces Akt activation. Preliminary in vivo evidence also demonstrates that Plek2 is critical for the PI3K-Akt pathway in that Plek2 knockout ameliorated myeloproliferation and significantly extended the survival of Pten hematopoietic specific knockout mice. These findings lead us to hypothesize that Plek2 functions as a central hub to connect the JAK2-STAT and the PI3K- Akt pathways and promote myeloproliferation. To test this hypothesis and investigate the mechanism of function of Plek2, we will use 1) in vitro biochemical and molecular studies to determine how Plek2 enhances the PI3K-Akt signaling, 2) Pten hematopoietic specific knockout mouse model to reveal the functions of Plek2 in vivo, and 3) pre-clinical MPN models and MPN patient samples to establish the efficacy of Plek2 inhibitors. Successful completion of this project will lead to novel insights into the role of Plek2 in the pathogenesis of MPNs and lay the foundation for clinical trials using Plek2 inhibitors as single agents or in combination with other compounds to treat MPNs.