Fatty acid/branched-chain amino acid metabolism in hematopoietic stem cells

描述（由申请人提供）：本提案的长期目标是鉴定和表征影响造血干细胞（hsc）代谢和功能的分子和途径。具体来说，该应用程序将验证支链氨基酸/脂肪酸（BCAA/FA）氧化在控制HSC功能中起关键作用的假设。造血干细胞的定义是其自我更新和产生多系血细胞的能力。在成人中，HSC存在于缺氧的骨髓微环境中，并保持相对静止。造血干细胞是如何保持静止状态，但却能迅速重新编程，为随后的分化和动员做好代谢准备，以维持体内平衡的，这是完全未知的。虽然已经有一些研究开始探讨代谢与HSC功能的关系，但大多数研究都集中在糖酵解和能量稳态方面，而不是脂质和氨基酸分解代谢对HSC功能的贡献。我们之前的研究表明，小鼠条件敲除Cited2 [CBP/p300-与谷氨酸(E)和天冬氨酸(D)-富尾2相互作用的反激活因子]会导致HSC凋亡增加、静止丧失和循环增加，从而导致造血重建能力严重受损。我们最近对从WT和Cited2 KO小鼠中分离的lt - hsc进行了全球代谢组学分析，发现支链氨基酸/脂肪酸（BCAA/FA）代谢是WT和Cited2 KO hsc之间的主要代谢差异之一。最近，一种以前未知的早幼粒细胞白血病(PML)-周期酶体增殖体活化受体δ (PPARδ)-脂肪酸氧化（FAO）途径被证明对维持hsc和控制不对称细胞分裂至关重要。有趣的是，其他研究表明Cited2与控制脂质代谢的PPAR核受体家族相互作用。此外，Cited2通过调控PGC-1α （PPAR γ共激活因子-1α）的作用，在糖异生中发挥作用，可能成为II型糖尿病的新治疗靶点。由于Cited2与PPAR的分子和生物学联系以及Cited2和PML敲除小鼠（FAO）的重叠表型，本多pi申请旨在通过两个子目标来验证Cited2作为调节支链氨基酸和脂肪酸代谢的功能节点以控制HSC功能的假设：1：鉴定影响Cited2敲除小鼠HSC功能的支链氨基酸和脂肪酸代谢中的中间体。2：确定Cited2如何调节造血干细胞中BCAA/FA氧化的机制。当前的应用程序代表了博士之间的集中协同新合作。Yang和Hoppel研究了Cited2在造血干细胞BCAA/FA氧化中的作用，这是一个尚未开发的造血研究领域。这些发现可能为控制HSC细胞命运提供新的方法，并具有未来的治疗意义。因此，这项研究“密切关注和指导验证有望开辟新发现途径的新概念和方法”，并符合NIDDK SHINE-II计划的使命。

DESCRIPTION (provided by applicant): The long-term goal of this proposal is to identify and characterize molecules and pathways that impact the metabolism and function of hematopoietic stem cells (HSCs). Specifically, the application will test the hypothesis that branched-chain amino acid/fatty acid (BCAA/FA) oxidation plays a critical role in controlling HSC functions. HSCs are defined by their ability to self-renew and to give rise to multi-lineages of blood cells. n adults, the HSC population resides in the hypoxic bone marrow microenvironment and remains relatively quiescent. How HSCs remain quiescent, but can rapidly reprogram themselves to be metabolically ready for subsequent differentiation and mobilization to maintain homeostasis is totally unknown. Although several studies have begun to investigate the relationship between metabolism and HSC function, most of the studies focused on glycolysis and energy homeostasis but not the contribution of lipid and amino acid catabolism on HSC functions. We have previously shown that conditional knockout (KO) of Cited2 [CBP/p300-interacting transactivators with glutamic acid (E) and aspartic acid (D)-rich tail 2] in the mouse results in increased HSC apoptosis, loss of quiescence and increased cycling, thus leading to severely impaired hematopoietic reconstitution capacity. Our recent global metabolomics analysis using LT-HSCs isolated from WT and Cited2 KO mice identified branched-chain amino acid/fatty acid (BCAA/FA) metabolism as one of the major metabolic differences between WT and Cited2 KO HSCs. Recently, a previously unknown promyelocytic leukemia (PML)-perioxisome proliferator-activated receptor δ (PPARδ)-fatty acid oxidation (FAO) pathway was shown to be crucial for the maintenance of HSCs and the control of asymmetric cell division. Interestingly, others have shown that Cited2 interacts with PPAR family of nuclear receptors that control lipid metabolism. In addition, Cited2 plays a role in gluconeogenesis through its regulation of PGC-1α (PPAR gamma coactivator-1α)actions and could be a novel therapeutic target for type II diabetes. Because of the molecular and biological link of Cited2 to PPAR and overlapping phenotypes of Cited2 and PML knockout mice (FAO), this multi-PI application intends to test the hypothesis that Cited2 acts as a functional node to modulate branched-chain amino acid and fatty acid metabolism in controlling HSC functions by two subaims: 1: To identify intermediates within the branched-chain amino acid and fatty acid metabolism that impact the function of HSCs from Cited2 knockout mice. 2: To determine mechanistically how Cited2 modulates the BCAA/FA oxidation in HSCs. The current application represents a focused synergistic new collaboration between Drs. Yang and Hoppel to investigate the role of Cited2 in BCAA/FA oxidation in HSCs, an under-explored research area in hematopoiesis. The findings may provide new means of controlling HSC cell fate with future therapeutic implications. The study therefore is "tightly focused and directed at validating novel concepts and approaches that promise to open up new pathways for discovery" and fits the mission of the SHINE-II program at NIDDK.