Metabolic regulation of hematopoietic stem cell function

描述(申请人提供)：能量代谢如何协调造血干细胞(HSC)的维持和谱系分化在很大程度上仍不清楚。干细胞生境中的低氧微环境限制了HSCs中线粒体的有氧代谢(呼吸/氧化磷酸化)，这通过减少线粒体呼吸的副产物活性氧物种(ROS)的产生来保护这个重要的细胞库免受氧化损伤。然而，调节HSC代谢活动的细胞内在机制还不是很清楚。此外，能量代谢如何与其他调节网络协调协调HSC分化还没有被表征。缺乏这样的知识阻碍了对与线粒体功能障碍和代谢状况相关的血液疾病发病机制的理解。PTPMT1是一种进化上保守的PTEN样磷脂酰肌醇磷酸(PIP)磷酸酶，定位于线粒体内膜，离子通道和转运体对线粒体离子动态平衡和代谢具有重要作用。我们的初步研究表明，在小鼠中靶向破坏PTPMT1会导致植入后胚胎死亡。从可诱导基因敲除(PTPMT1fl/fl/Mx1-Cre+)小鼠的成年骨髓(BM)细胞中缺失PTPMT1会损害髓系和淋巴样细胞的发育。此外，造血细胞特异性基因敲除(PTPMT1fl/fl/Vav1-Cre+)小鼠的出生后造血完全被阻断。这些小鼠在出生后3-6天内会死于全血细胞减少症。值得注意的是，在PTPMT1fl/fl/Mx1-Cre+小鼠和PTPMT1fl/fl/Vav1-Cre+新生儿中，骨髓中的HSC分别增加了~30倍和~10倍。初步的机制研究表明，PTPMT1缺失细胞的细胞呼吸减少，而糖酵解增加。这项应用的目的是扩展这些研究，以进一步确定线粒体磷酸酶PTPMT1在HSCs中的作用和信号机制。我们假设PTPMT1通过调节线粒体代谢来协调HSC的动态平衡和谱系承诺。我们计划通过以下两个目标来验证我们的假设并实现此应用的目标。(I)明确PTPMT1在造血中的作用。(Ii)确定PTPMT1调节HSC功能的机制。这项拟议的工作具有创新性，因为它探索了精细控制的线粒体代谢对HSC维持和谱系分化的意义。这些工作的结合有望对造血细胞发育的生物能量调控产生新的见解。此外，收集的信息将有助于更好地了解由线粒体功能障碍和代谢状况引起的血液疾病的病理生理学。 公共卫生相关性：提出的项目试图了解新发现的基于线粒体的磷酸酶PTPMT1在血细胞发育中的作用和信号机制。预计拟议的研究将对造血干细胞功能的代谢调节产生概念性的见解。此外，收集的信息将有助于更好地了解与线粒体功能障碍和代谢状况相关的血液疾病的病理生理学。

DESCRIPTION (provided by applicant): It remains largely unknown how energy metabolism coordinates hematopoietic stem cell (HSC) maintenance and lineage differentiation. The hypoxic microenvironment in stem cell niches limits mitochondrial aerobic metabolism (respiration/oxidative phosphorylation) in HSCs, which preserves this essential cell reservoir from oxidative damage by attenuating the production of reactive oxygen species (ROS), a byproduct of mitochondrial respiration. However, cell intrinsic mechanisms regulating HSC metabolic activities are poorly defined. Furthermore, how energy metabolism orchestrates HSC differentiation in concert with other regulatory networks has not been characterized. Lack of such knowledge impedes the understanding of the pathogenesis of blood diseases associated with mitochondrial dysfunction and metabolic conditions. PTPMT1, an evolutionarily conserved PTEN-like phosphatidylinositol phosphate (PIP) phosphatase, is localized to the mitochondrial inner membrane where ion channels and transporters, important for mitochondrial ion homeostasis and thus metabolism, reside. Our preliminary studies have shown that targeted disruption of PTPMT1 in mice results in post-implantation embryonic lethality. Deletion of PTPMT1 from adult bone marrow (BM) cells of inducible knockout (PTPMT1fl/fl/Mx1-Cre+) mice impairs myeloid and lymphoid cell development. Moreover, postnatal hematopoiesis in hematopoietic cell-specific knockout (PTPMT1fl/fl/Vav1-Cre+) mice is completely blocked. These mice succumb to pancytopenia within 3-6 days of birth. Strikingly, HSCs in the BM are increased by ~30-fold and ~10-fold in PTPMT1fl/fl/Mx1-Cre+ mice and PTPMT1fl/fl/Vav1-Cre+ neonates, respectively. Preliminary mechanistic studies show that cellular respiration of PTPMT1-depleted cells is decreased while glycolysis is enhanced. The objective of this application is to extend these studies to further determine the role and signaling mechanism of mitochondrial phosphatase PTPMT1 in HSCs. We hypothesize that PTPMT1 coordinates HSC homeostasis and lineage commitment by modulating mitochondrial metabolism. We plan to test our hypothesis and accomplish the objective of this application by pursuing the following two aims. (i) To define the role of PTPMT1 in hematopoiesis. (ii) To determine the mechanisms by which PTPMT1 modulates HSC function. The proposed work is innovative, because it explores the significance of finely controlled mitochondrial metabolism for HSC maintenance and lineage differentiation. The combination of the work proposed is collectively expected to yield novel insights into the bioenergetic regulation of hematopoietic cell development. In addition, the information gathered will lead to a better understanding of the pathophysiology of blood disorders resulting from mitochondrial dysfunction and metabolic conditions. PUBLIC HEALTH RELEVANCE: The project proposed seeks to understand the role and signaling mechanisms of the newly identified mitochondria-based phosphatase PTPMT1 in blood cell development. It is anticipated that the proposed studies will yield conceptual insights into metabolic modulation of hematopoietic stem cell function. Also, the information gathered will lead to a better understanding of the pathophysiology of blood diseases associated with mitochondrial dysfunction and metabolic conditions.