The regulation of protein synthesis in stem cells

干细胞中蛋白质合成的调控

• 批准号: 8997792
• 负责人: SEAN J MORRISON
• 金额: $ 6.77万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-02-25 至 2016-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8997792
• 关键词: 1-Phosphatidylinositol 3-Kinase; Address; Adult; Area; Attenuated; Biological Assay; Biology; Cell Count; Cell Cycle; Cell Maintenance; Cell Size; Cell physiology; Cells; Data; Defect; Dependence; Disease; Health; Hematopoiesis; Hematopoietic; Hematopoietic System; Hematopoietic stem cells; Hemorrhage; Housing; Individual; Learning; Left; Life; Maintenance; Measures; Mus; Natural regeneration; PTEN gene; Paper; Population; Protein Biosynthesis; Regulation; Relative (related person); Ribosomal Proteins; Role; Signal Pathway; Signal Transduction; Sirolimus; Stem cells; Techniques; Testing; Translations; Tumor Suppressor Proteins; Work; human FRAP1 protein; in vivo; leukemogenesis; polypeptide; progenitor; response; self-renewal; stem cell population

DESCRIPTION (provided by applicant): To sustain hematopoiesis, hematopoietic stem cells (HSCs) must persist throughout life, constantly regenerating hematopoietic cells lost to normal turnover, bleeding, and disease. Much has been learned over the past ten years regarding the mechanisms that regulate HSC maintenance. This work has demonstrated that several aspects of cellular physiology are regulated differently in HSCs as compared to other hematopoietic cells. This raises the fundamental question of whether all aspects of cellular physiology are regulated differently in stem cells as compared to restricted progenitors, or whether certain aspects of cellular physiology are "house-keeping" functions that are regulated similarly in stem cells and restricted progenitors. Unfortunately, many aspects of cellular physiology are technically difficult to study with existing techniques in small numbers of stem cells and therefore have not yet been addressed, leaving large areas of biology unexplored. One such aspect of cellular physiology is the regulation of protein synthesis. There are almost no data on the regulation of translation in any somatic stem cell population, partly because assays have not yet been developed to study translation in small numbers of cells in vivo. We have recently developed an assay that makes it possible to study the rate at which polypeptides are synthesized by individual cells in vivo. Using this assay we have determined that HSCs have significantly lower rates of protein synthesis than other hematopoietic cells even when we control for differences in cell cycle distribution. Our preliminary functional data suggest that HS maintenance depends upon highly regulated rates of protein synthesis. This discovery may explain previously observed defects in HSC self-renewal that were not understood at a mechanistic level. For example, we have demonstrated previously that deletion of the PTEN tumor suppressor in adult hematopoietic cells increases PI3-kinase pathway signaling in HSCs, leading to leukemogenesis and HSC depletion. Although the depletion of PTEN deficient HSCs is known to depend upon a tumor suppressor response induced by mTORC1 and mTORC2 signaling, it is unknown how elevated mTOR signaling increases tumor suppressor expression. In this application, we propose to extend our preliminary data to test whether PTEN is required in adult HSCs to maintain an unusually low level of protein synthesis and whether increased protein synthesis after PTEN deletion induces the tumor suppressor response that depletes HSCs. This work has the potential to yield new techniques to study protein synthesis in rare cell populations in vivo and to open new areas of inquiry related to the role of regulated protein synthesis in hematopoiesis and stem cell function. Defects in the regulation of protein synthesis could potentially contribute to diverse and poorly understood diseases of the hematopoietic system.

描述（由申请人提供）：为了维持造血，造血干细胞（HSC）必须终生存在，不断再生因正常周转、出血和疾病而丢失的造血细胞。在过去的十年里，已经了解了很多关于调节HSC维持的机制。这项工作表明，与其他造血细胞相比，HSC中细胞生理学的几个方面受到不同的调节。这就提出了一个基本问题，即与限制性祖细胞相比，干细胞中细胞生理学的所有方面是否都受到不同的调节，或者细胞生理学的某些方面是否是在干细胞和限制性祖细胞中受到类似调节的“管家”功能。不幸的是，细胞生理学的许多方面在技术上很难用现有技术在少量干细胞中进行研究，因此尚未得到解决，留下了大量的生物学领域未被探索。细胞生理学的一个这样的方面是蛋白质合成的调节。几乎没有关于任何体干细胞群体中翻译调控的数据，部分原因是尚未开发出在体内研究少量细胞翻译的测定方法。我们最近开发了一种测定法，使得有可能研究多肽在体内由单个细胞合成的速率。使用该测定，我们已经确定，即使当我们控制细胞周期分布的差异时，HSC也具有比其他造血细胞显著更低的蛋白质合成速率。我们的初步功能数据表明，HS的维护依赖于高度调节的蛋白质合成速率。这一发现可以解释以前观察到的HSC自我更新的缺陷，在机械水平上没有理解。例如，我们先前已经证明，在成人造血细胞中缺失PTEN肿瘤抑制因子会增加HSC中的PI 3-激酶途径信号传导，导致白血病发生和HSC耗竭。尽管已知PTEN缺陷型HSC的消耗依赖于mTORC 1和mTORC 2信号传导诱导的肿瘤抑制应答，但尚不清楚升高的mTOR信号传导如何增加肿瘤抑制表达。在本申请中，我们建议扩展我们的初步数据，以测试是否需要在成人HSC中维持异常低水平的蛋白质合成，以及是否增加蛋白质合成后，PTEN缺失诱导肿瘤抑制反应，耗尽HSC。这项工作有可能产生新的技术来研究体内稀有细胞群中的蛋白质合成，并开辟与造血和干细胞功能中调节蛋白质合成的作用有关的新的研究领域。蛋白质合成调节的缺陷可能会导致多种且人们知之甚少的造血系统疾病。