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。具体而言，该应用程序将测试支链氨基酸/脂肪酸（BCAA/FA）氧化在控制HSC功能中起关键作用的假设。HSC的定义是它们自我更新和产生多系血细胞的能力。在成年人中，HSC群体驻留在缺氧的骨髓微环境中，并保持相对静止。HSC如何保持静止，但可以快速重新编程自身以在代谢上为随后的分化和动员做好准备以维持稳态是完全未知的。虽然已有一些研究开始探讨代谢与HSC功能之间的关系，但大多数研究集中在糖酵解和能量稳态，而不是脂质和氨基酸催化剂对HSC功能的贡献。我们之前已经证明，在小鼠中条件性敲除（KO）Cited 2 [CBP/p300相互作用的反式激活因子与富含谷氨酸（E）和天冬氨酸（D）的尾2]导致HSC凋亡增加、静止期丧失和循环增加，从而导致造血重建能力严重受损。我们最近使用从WT和Cited 2 KO小鼠分离的LT-HSC进行的全球代谢组学分析确定了支链氨基酸/脂肪酸（BCAA/FA）代谢是WT和Cited 2 KO HSC之间的主要代谢差异之一。最近，一个以前未知的早幼粒细胞白血病（PML）-过氧化物酶体增殖物激活受体δ（PPARδ）-脂肪酸氧化（FAO）途径被证明是至关重要的维持HSC和控制细胞不对称分裂。有趣的是，其他人已经表明Cited 2与控制脂质代谢的核受体的PPAR家族相互作用。此外，Cited 2通过调节PGC-1α（PPAR γ coactivator-1α）的作用在糖尿病的发生中发挥作用，有望成为II型糖尿病治疗的新靶点。由于Cited 2与PPAR的分子和生物学联系以及Cited 2和PML敲除小鼠（FAO）的重叠表型，该多PI应用旨在通过两个子目标来测试Cited 2在控制HSC功能中充当调节支链氨基酸和脂肪酸代谢的功能节点的假设：1：鉴定影响Cited 2基因敲除小鼠HSC功能的支链氨基酸和脂肪酸代谢中间产物。2：确定Cited 2如何调节HSC中BCAA/FA氧化的机制。目前的申请代表了Yang博士和Hoppel博士之间的一项重点协同新合作，以研究Cited 2在HSC中BCAA/FA氧化中的作用，这是造血中一个未充分探索的研究领域。这一发现可能为控制HSC细胞命运提供新的手段，并具有未来的治疗意义。因此，这项研究“紧紧围绕并致力于验证新的概念和方法，这些概念和方法有望为发现开辟新的途径”，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.