Department of Molecular and Cellular Biology, University of Connecticut, Storrs, Connecticut, USA.
Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; Mitochondrial Phospholipid Research Center, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
J Biol Chem. 2024 Oct;300(10):107746. doi: 10.1016/j.jbc.2024.107746. Epub 2024 Sep 3.
Mitochondria are central to cellular metabolism; hence, their dysfunction contributes to a wide array of human diseases. Cardiolipin, the signature phospholipid of the mitochondrion, affects proper cristae morphology, bioenergetic functions, and metabolic reactions carried out in mitochondrial membranes. To match tissue-specific metabolic demands, cardiolipin typically undergoes an acyl tail remodeling process with the final step carried out by the phospholipid-lysophospholipid transacylase tafazzin. Mutations in tafazzin are the primary cause of Barth syndrome. Here, we investigated how defects in cardiolipin biosynthesis and remodeling impacts metabolic flux through the TCA cycle and associated yeast pathways. Nuclear magnetic resonance was used to monitor in real-time the metabolic fate of C-pyruvate in isolated mitochondria from three isogenic yeast strains. We compared mitochondria from a WT strain to mitochondria from a Δtaz1 strain that lacks tafazzin and contains lower amounts of unremodeled cardiolipin and mitochondria from a Δcrd1 strain that lacks cardiolipin synthase and cannot synthesize cardiolipin. We found that the C-label from the pyruvate substrate was distributed through twelve metabolites. Several of the metabolites were specific to yeast pathways including branched chain amino acids and fusel alcohol synthesis. While most metabolites showed similar kinetics among the different strains, mevalonate concentrations were significantly increased in Δtaz1 mitochondria. Additionally, the kinetic profiles of α-ketoglutarate, as well as NAD and NADH measured in separate experiments, displayed significantly lower concentrations for Δtaz1 and Δcrd1 mitochondria at most time points. Taken together, the results show how cardiolipin remodeling influences pyruvate metabolism, tricarboxylic acid cycle flux, and the levels of mitochondrial nucleotides.
线粒体是细胞代谢的核心；因此，它们的功能障碍导致了广泛的人类疾病。心磷脂是线粒体的标志性磷脂，影响嵴的形态、生物能量功能和线粒体膜中的代谢反应。为了匹配组织特异性的代谢需求，心磷脂通常会经历酰基尾重塑过程，最后一步由磷脂-溶血磷脂酰基转移酶 tafazzin 完成。tafazzin 的突变是 Barth 综合征的主要原因。在这里，我们研究了心磷脂生物合成和重塑缺陷如何影响 TCA 循环和相关酵母途径的代谢通量。核磁共振用于实时监测来自三种同基因酵母菌株的分离线粒体中 C-丙酮酸的代谢命运。我们将 WT 菌株的线粒体与缺乏 tafazzin 且含有未重塑心磷脂的 Δtaz1 菌株的线粒体以及缺乏心磷脂合酶且不能合成心磷脂的 Δcrd1 菌株的线粒体进行了比较。我们发现，来自丙酮酸底物的 C 标记分布在十二个代谢物中。一些代谢物是酵母途径特有的，包括支链氨基酸和杂醇合成。虽然大多数代谢物在不同菌株之间表现出相似的动力学，但 Δtaz1 线粒体中的甲羟戊酸浓度显著增加。此外，在单独的实验中测量的 α-酮戊二酸和 NAD 和 NADH 的动力学曲线在大多数时间点上，Δtaz1 和 Δcrd1 线粒体的浓度明显较低。综上所述，这些结果表明心磷脂重塑如何影响丙酮酸代谢、三羧酸循环通量和线粒体核苷酸水平。
