Wang Wenqing, Arreola Martin, Mathews Thomas, DeVilbiss Andrew, Zhao Zhiyu, Martin-Sandoval Misty, Mohammed Abdulvasey, Benegiamo Giorgia, Awani Avni, Goeminne Ludger, Dever Daniel, Nakauchi Yusuke, Porteus Matthew H, Pavel-Dinu Mara, Al-Herz Waleed, Auwerx Johan, Morrison Sean J, Weinacht Katja G
Department of Pediatrics, Stanford University School of Medicine, Stanford, CA.
Children's Medical Center Research Institute, The University of Texas Southwestern, Dallas, TX.
Blood. 2024 Dec 26;144(26):2718-2734. doi: 10.1182/blood.2024024123.
Cellular metabolism is highly dynamic during hematopoiesis, yet the regulatory networks that maintain metabolic homeostasis during differentiation are incompletely understood. Herein, we have studied the grave immunodeficiency syndrome reticular dysgenesis caused by loss of mitochondrial adenylate kinase 2 (AK2) function. By coupling single-cell transcriptomics in samples from patients with reticular dysgenesis with a CRISPR model of this disorder in primary human hematopoietic stem cells, we found that the consequences of AK2 deficiency for the hematopoietic system are contingent on the effective engagement of metabolic checkpoints. In hematopoietic stem and progenitor cells, including early granulocyte precursors, AK2 deficiency reduced mechanistic target of rapamycin (mTOR) signaling and anabolic pathway activation. This conserved nutrient homeostasis and maintained cell survival and proliferation. In contrast, during late-stage granulopoiesis, metabolic checkpoints were ineffective, leading to a paradoxical upregulation of mTOR activity and energy-consuming anabolic pathways such as ribonucleoprotein synthesis in AK2-deficient cells. This caused nucleotide imbalance, including highly elevated adenosine monophosphate and inosine monophosphate levels, the depletion of essential substrates such as NAD+ and aspartate, and ultimately resulted in proliferation arrest and demise of the granulocyte lineage. Our findings suggest that even severe metabolic defects can be tolerated with the help of metabolic checkpoints but that the failure of such checkpoints in differentiated cells results in a catastrophic loss of homeostasis.
细胞代谢在造血过程中高度动态变化，但在分化过程中维持代谢稳态的调控网络尚未完全明了。在此，我们研究了由线粒体腺苷酸激酶2（AK2）功能丧失引起的严重免疫缺陷综合征——网状发育不全。通过将网状发育不全患者样本中的单细胞转录组学与原代人类造血干细胞中该疾病的CRISPR模型相结合，我们发现AK2缺乏对造血系统的影响取决于代谢检查点的有效参与。在造血干细胞和祖细胞中，包括早期粒细胞前体，AK2缺乏会降低雷帕霉素机制靶点（mTOR）信号传导和合成代谢途径的激活。这维持了营养稳态并保持了细胞存活和增殖。相反，在粒细胞生成后期，代谢检查点无效，导致AK2缺乏细胞中mTOR活性和耗能合成代谢途径（如核糖核蛋白合成）出现反常上调。这导致核苷酸失衡，包括单磷酸腺苷和单磷酸次黄嘌呤水平大幅升高，NAD +和天冬氨酸等必需底物耗竭，最终导致粒细胞谱系的增殖停滞和死亡。我们的研究结果表明，即使存在严重的代谢缺陷，借助代谢检查点也可以耐受，但分化细胞中此类检查点的失效会导致灾难性的稳态丧失。
