Signaling pathways regulated by GSK3 in hematopoietic stem cell

主要研究者/项目负责人（末、首、中）：黄健 造血干细胞中GSK 3调控的信号通路 摘要 造血干细胞（HSC）具有两个明显的特征：自我更新和分化为造血干细胞的能力。 成熟的血细胞调控HSC自我更新和分化的信号通路不完善 明白糖原合成酶激酶-3（GSK 3），一种经典Wnt信号传导的负调节因子， 通过Jak/Stat和PI 3信号传导的造血生长因子信号传导途径的下游靶点 激酶/Akt依赖性途径，已经涉及HSC活性的调节。规范Wnt信号传导 已被牵连在HSC自我更新，但这一途径的作用仍然存在争议。近日 PTEN-PI 3 K-mTOR通路在HSC的维持中起重要作用。我们 假设GSK 3是HSC内Wnt和PI 3 K下游的关键效应子，其调节 HSC人口。为了支持这一假设，我们的初步数据显示：1）锂和其他 选择性GSK 3抑制剂显著增加小鼠中HSC的数量，2）RNAi介导的HSC耗竭， 小鼠HSC中的Gsk 3最初在骨髓移植中扩增HSC群体，但长期抑制 的GSK 3消耗HSC。3)通过抑制GSK 3来扩增HSC是通过β-连环蛋白介导的， HSC的消耗主要依赖于mTOR信号传导。这些观察结果支持了 GSK 3是造血的重要调节因子在本建议中，我们将扩展我们的研究，探讨 GSK 3磷酸化在HSC中的功能作用。我们还将讨论Gsk 3a的同种型特异性功能 相对于小鼠中具有新构建的条件性敲除的造血细胞中的Gsk 3b。非细胞- GSK 3抑制对HSC的自主作用也将通过GSK 3的条件性敲除来探索， 成骨细胞龛。此外，我们将测试是否调节GSK 3和mTOR的活性可以扩大 离体培养中的HSC。体外培养HSC自我更新新调控因子的功能筛选 将执行。本项目的总体目标是检查Wnt和 PTEN-PI 3 K-mTOR信号传导在对GSK 3抑制的应答中的作用，并确定GSK 3在PTEN-PI 3 K-mTOR信号传导中的作用。 调节造血系统内的这些通路。从这些研究中学到的知识 将为HSC自我更新和分化的调控机制提供新的见解 并且可以改善造血障碍的治疗。 1

Principal Investigator/Program Director (Last, First, Middle): Huang, Jian Signaling pathways regulated by GSK3 in hematopoietic stem cells Abstract Hematopoietic stem cells (HSCs) possess two distinct features: the ability to self-renew and to differentiate into mature blood cells. The signaling pathways that regulate HSC self-renewal and differentiation are not well understood. Glycogen synthase kinase-3 (GSK3), a negative regulator of canonical Wnt signaling and a downstream target of hematopoietic growth factor signaling pathways that signal through Jak/Stat and PI3 kinase/Akt dependent pathways, has been implicated in the regulation of HSC activity. Canonical Wnt signaling has been implicated in HSC self-renewal, but the role of this pathway remains controversial. Recently, the PTEN-PI3K-mTOR pathway has been demonstrated to play an essential role in HSC maintenance. Our hypothesis is that GSK3 is a critical effector downstream of Wnt and PI3K within HSCs that regulates the HSC population. In support of this hypothesis, our preliminary data show that: 1) lithium and other selective GSK3 inhibitors significantly increase the number of HSCs in mice, 2) RNAi mediated depletion of Gsk3 in murine HSCs initially expands the HSC population in bone marrow transplants, but long-term inhibition of GSK3 exhausts HSC. 3) The expansion of HSCs by inhibition of GSK3 is mediated through �-catenin while the depletion of HSCs is largely dependent on mTOR signaling. These observations support the hypothesis that GSK3 is an important regulator of hematopoiesis. In this proposal, we will extend our study to explore the functional role of GSK3 phosphorylation in HSCs. We will also address the isoform specific functions of Gsk3a vs Gsk3b in hematopoietic cells with newly constructed conditional knockouts in mice. The non cell- autonomous effect of GSK3 inhibition on HSCs will also be explored with the conditional knockout of Gsk3 in the osteoblast niche. Furthermore, we will test whether modulating the activity of GSK3 and mTOR can expand HSCs in ex vivo culture. A functional screen to identify new regulators of HSCs self-renewal in ex vivo culture will be carried out. The overall goal of this project is to examine the respective contributions of Wnt and PTEN-PI3K-mTOR signaling in the response to GSK3 inhibition and to define the role of GSK3 in regulating these pathways within the hematopoietic system. The knowledge learned from these studies will provide new insights into the mechanisms of the regulation of HSC self-renewal and differentiation and may improve the therapy of hematopoietic disorders. 1