The role of PTEN phosphorylation remodeling in hematopoietic stem cell regulation

PTEN磷酸化重塑在造血干细胞调控中的作用

• 批准号: 8197839
• 负责人: Jiwang Zhang
• 金额: $ 37万
• 依托单位: LOYOLA UNIVERSITY CHICAGO
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-03-15 至 2014-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8197839
• 关键词: Acute; Acute leukemia; Adhesions; Affect; Back; Binding; Biological Process; Blast Cell; Blood Cells; Bone Marrow; Cell Cycle; Cell Line; Cell Proliferation; Cell physiology; Cells; Clinical; Contact Inhibition; Defect; Dominant-Negative Mutation; Ectopic Expression; Engraftment; Event; Goals; Growth; Hematopoietic; Hematopoietic Neoplasms; Hematopoietic stem cells; Homeostasis; In Vitro; Knock-out; Knockout Mice; Lipids; Longevity; Lymphoblastic Leukemia; MAP Kinase Gene; MAPK14 gene; Maintenance; Mediating; Molecular Conformation; Mus; Mutation; Myelogenous; Myeloproliferative disease; Nature; Null Lymphocytes; Outcome; PTEN gene; Patients; Peripheral; Phenotype; Phosphoric Monoester Hydrolases; Phosphorylation; Protein phosphatase; Proteins; Regulation; Role; SB 203580; Sampling; Signal Transduction; Stem cell transplant; Stem cells; Tail; Testing; Transplantation; Tumor Suppressor Proteins; Wild Type Mouse; cell behavior; cell motility; exhaustion; hematopoietic tissue; improved; inhibitor/antagonist; insight; leukemia; leukemogenesis; migration; mutant; progenitor; protein protein interaction; public health relevance; reconstitution; self-renewal; stem cell niche; vector

DESCRIPTION (provided by applicant): Our goal is to define the roles of Pten phosphorylation remodeling in hematopoietic stem cell (HSC) regulation. Pten, a tumor suppressor, has both lipid and protein phosphatase activities that inhibit PI3K/Akt and Fak-MAPK signaling respectively. It regulates many aspects of cell behavior, including proliferation, survival, adhesion and migration.1-4 The phosphatase activities of Pten are regulated by its c-terminal tail phosphorylation.5, 6 In addition, Pten many also have some phosphatase-independent functions. Many of Pten's biological functions are dependent upon protein-protein interactions which are mediated by its PDZ-motif.7 Knockout of Pten in mouse hematopoietic tissues results in abnormal activation of PI3K/Akt and Src signaling, which leads to uncontrolled HSC activation (G0 to G1 transition) and mobilization, followed by HSC decline. These mice develop myeloproliferative disorder (MPD) followed by acute myeloid/T lymphoid leukemia. Although Pten mutations are not commonly found in hematopoietic malignancies, including leukemia, p-Pten (the phosphorylated form of Pten) levels are increased in the abnormal blasts of most leukemic patients' bone marrow samples. Phosphorylation of Pten's c-terminal tail (ser380, thr382, and thr383) leads to a conformation change which may result in the blocking of its ability to bind to other partner proteins, the reduction of Pten phosphatase activity, and/or the alteration of the lifespan of the Pten protein. Our recent studies have suggested that the phosphorylation of Pten's c-terminal tail may not affect its lipid phosphatase activity but significantly compromises its protein phosphatase activity. The non-phosphorylated form of Pten (non-p-Pten) inhibits Src/Fak/p38 activity, thus repressing cell migration/invasiveness and inducing cell:cell contact inhibition of growth. p-Pten might have a dominant-negative function which induces cell-contact-related Src/Fak/p38 activation. We found that non-p-Pten is expressed in HSCs, while p- Pten levels are increased when HSCs enter the cell cycle; both of these events correspond to increased p- Src, p-Fak and p-p38 levels. Transduced over-expression of non-p-Pten preserves HSCs in a bone marrow niche-dependent manner, whereas transduced over-expression of p-Pten induces HSC/progenitors (HSC/Ps, from wild-type mice which have endogenous Pten expression) to differentiate to myeloid precursors. We propose that non-p-Pten maintains HSC quiescence and self-renewal ability through inducing cell:cell (HSCs and niche cells) contact-induced inhibition of growth by inhibiting Src/Fak/p38 signaling activities, whereas Pten's c-terminal phosphorylation alters its ability to bind to its partners and compromises its protein phosphatase activity. p-Pten promotes opposite functions to these through inducing cell:cell contact-related Src/Fak/p38 signaling. These studies will provide insights into how quiescent HSCs become activated and expand in number, and how we might be able to induce activated HSCs to revert back into quiescence in order to enhance their engraftment ability. This should greatly help our ability to expand HSCs in vitro and hence improve the outcome of clinical stem cell transplantation. It might be also help us to understand the nature of Pten c-terminal phosphorylation in leukemogenesis. PUBLIC HEALTH RELEVANCE: This proposed study will provide insights into how quiescent hematopoietic stem cell be induced cell cycle entry and proliferation, and how stem cell function is regulated by PTEN c-terminal phosphorylation. The predicted outcome will greatly help our ability to expand hematopoietic stem cells in vitro and hence improve the outcome of clinical stem cell transplantation.

描述（由申请人提供）：我们的目标是确定 Pten 磷酸化重塑在造血干细胞 (HSC) 调节中的作用。 Pten 是一种肿瘤抑制因子，具有脂质和蛋白磷酸酶活性，分别抑制 PI3K/Akt 和 Fak-MAPK 信号传导。它调节细胞行为的许多方面，包括增殖、存活、粘附和迁移。1-4 Pten 的磷酸酶活性受其 C 末端尾部磷酸化的调节。5, 6 此外，Pten 许多还具有一些不依赖于磷酸酶的功能。 Pten 的许多生物学功能依赖于由其 PDZ 基序介导的蛋白质-蛋白质相互作用。7 小鼠造血组织中 Pten 的敲除会导致 PI3K/Akt 和 Src 信号传导异常激活，从而导致不受控制的 HSC 激活（G0 至G1 过渡）和动员，随后是 HSC 下降。这些小鼠先发展为骨髓增生性疾病 (MPD)，然后发展为急性髓系/T 淋巴白血病。尽管 Pten 突变在包括白血病在内的造血系统恶性肿瘤中并不常见，但在大多数白血病患者骨髓样本的异常母细胞中，p-Pten（Pten 的磷酸化形式）水平升高。 Pten 的 C 末端尾部（ser380、thr382 和 thr383）的磷酸化会导致构象变化，从而可能导致其与其他伙伴蛋白结合的能力受阻、Pten 磷酸酶活性降低和/或Pten 蛋白的寿命。我们最近的研究表明，Pten C 末端尾部的磷酸化可能不会影响其脂质磷酸酶活性，但会显着损害其蛋白磷酸酶活性。 Pten 的非磷酸化形式（非 p-Pten）抑制 Src/Fak/p38 活性，从而抑制细胞迁移/侵袭并诱导细胞与细胞接触抑制生长。 p-Pten 可能具有显性失活功能，可诱导细胞接触相关的 Src/Fak/p38 激活。我们发现非p-Pten在HSC中表达，而当HSC进入细胞周期时p-Pten水平升高；这两个事件都与 p-Src、p-Fak 和 p-p38 水平升高相对应。非 p-Pten 的转导过表达以骨髓生态位依赖性方式保留 HSC，而 p-Pten 的转导过表达则诱导 HSC/祖细胞（HSC/P，来自具有内源性 Pten 表达的野生型小鼠）分化为骨髓前体细胞。 我们认为非 p-Pten 通过抑制 Src/Fak/p38 信号传导活性来诱导细胞：细胞（HSC 和生态位细胞）接触诱导的生长抑制，从而维持 HSC 静止和自我更新能力，而 Pten 的 C 末端磷酸化改变它与其伴侣结合并损害其蛋白磷酸酶活性的能力。 p-Pten 通过诱导细胞：细胞接触相关的 Src/Fak/p38 信号传导来促进与这些相反的功能。 这些研究将深入了解静止的造血干细胞如何被激活并数量增加，以及我们如何能够诱导激活的造血干细胞恢复静止状态以增强其植入能力。这将极大地帮助我们在体外扩增造血干细胞，从而改善临床干细胞移植的结果。这也可能有助于我们了解 Pten C 末端磷酸化在白血病发生中的本质。 公共健康相关性：这项拟议的研究将深入了解如何诱导静止造血干细胞进入细胞周期和增殖，以及如何通过 PTEN c 末端磷酸化来调节干细胞功能。预测的结果将极大地帮助我们体外扩增造血干细胞，从而改善临床干细胞移植的结果。