Jeon Miji, Schmitt Danielle L, Kyoung Minjoung, An Songon
Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC); 1000 Hilltop Circle, Baltimore, Maryland 21250, United States.
Program in Oncology, Marlene and Stewart Greenebaum Comprehensive Cancer Center, University of Maryland, Baltimore, Maryland 21201, United States.
ACS Bio Med Chem Au. 2023 Aug 8;3(5):461-470. doi: 10.1021/acsbiomedchemau.3c00037. eCollection 2023 Oct 18.
Enzymes in glucose metabolism have been subjected to numerous studies, revealing the importance of their biological roles during the cell cycle. However, due to the lack of viable experimental strategies for measuring enzymatic activities particularly in living human cells, it has been challenging to address whether their enzymatic activities and thus anticipated glucose flux are directly associated with cell cycle progression. It has remained largely elusive how human cells regulate glucose metabolism at a subcellular level to meet the metabolic demands during the cell cycle. Meanwhile, we have characterized that rate-determining enzymes in glucose metabolism are spatially organized into three different sizes of multienzyme metabolic assemblies, termed glucosomes, to regulate the glucose flux between energy metabolism and building block biosynthesis. In this work, we first determined using cell synchronization and flow cytometric techniques that enhanced green fluorescent protein-tagged phosphofructokinase is adequate as an intracellular biomarker to evaluate the state of glucose metabolism during the cell cycle. We then applied fluorescence single-cell imaging strategies and discovered that the percentage of Hs578T cells showing small-sized glucosomes is drastically changed during the cell cycle, whereas the percentage of cells with medium-sized glucosomes is significantly elevated only in the G1 phase, but the percentage of cells showing large-sized glucosomes is barely or minimally altered along the cell cycle. Should we consider our previous localization-function studies that showed assembly size-dependent metabolic roles of glucosomes, this work strongly suggests that glucosome sizes are modulated during the cell cycle to regulate glucose flux between glycolysis and building block biosynthesis. Therefore, we propose the size-specific modulation of glucosomes as a behind-the-scenes mechanism that may explain functional association of glucose metabolism with the cell cycle and, thereby, their metabolic significance in human cell biology.
葡萄糖代谢中的酶已经过大量研究，揭示了它们在细胞周期中生物学作用的重要性。然而，由于缺乏可行的实验策略来测量酶活性，尤其是在活的人类细胞中，因此难以确定它们的酶活性以及预期的葡萄糖通量是否与细胞周期进程直接相关。人类细胞如何在亚细胞水平调节葡萄糖代谢以满足细胞周期中的代谢需求，在很大程度上仍然不清楚。与此同时，我们已经确定，葡萄糖代谢中的限速酶在空间上组织成三种不同大小的多酶代谢组装体，称为糖体，以调节能量代谢和生物合成原料之间的葡萄糖通量。在这项工作中，我们首先使用细胞同步和流式细胞术技术确定，增强型绿色荧光蛋白标记的磷酸果糖激酶足以作为细胞内生物标志物来评估细胞周期中葡萄糖代谢的状态。然后，我们应用荧光单细胞成像策略，发现显示小尺寸糖体的Hs578T细胞百分比在细胞周期中发生了剧烈变化，而具有中等尺寸糖体的细胞百分比仅在G1期显著升高，但显示大尺寸糖体的细胞百分比在整个细胞周期中几乎没有或仅有微小变化。考虑到我们之前的定位功能研究表明糖体的组装大小依赖性代谢作用，这项工作有力地表明，糖体大小在细胞周期中受到调节，以调节糖酵解和生物合成原料之间的葡萄糖通量。因此，我们提出糖体的大小特异性调节是一种幕后机制，可能解释葡萄糖代谢与细胞周期的功能关联，从而解释它们在人类细胞生物学中的代谢意义。
