脂肪酸延长酶缺陷对酵母细胞脂质代谢及油酸胁迫响应的影响

Study on the Response of Fatty Acid Elongase Defects to Lipid Metabolism and Oleic Acid Stress in Saccharomyces cerevisiae

生物医学证据表明,过量的油脂特别是脂肪酸(fatty acids,FA)在非脂肪组织累积会引起脂代谢障碍,引起细胞功能紊乱或坏死。脂肪酸延长酶家族参与脂肪酸代谢,具有真核生物的高度保守性,且与膜脂的代谢密切相关。但脂肪酸延长酶与细胞脂毒效应的关系并不清楚。该文利用模式生物酿酒酵母在脂类代谢研究中性状易于表征、遗传操作便利的优势,通过对比脂肪酸延长酶缺陷型elo1Δ、elo2Δ和elo3Δ与野生型酵母(wild-type,WT)对不同脂肪酸胁迫的响应,发现极长链脂肪酸延长酶基因ELO2和ELO3缺陷后对油酸(oleic acid,OLA)高度敏感;细胞脂滴及中性脂质的代谢对维持细胞脂类平衡起关键作用。研究结果显示,长链脂肪酸的合成缺陷或油酸处理均促进细胞脂滴的形成,同时显著提高细胞中性油脂(TAG)和甾醇酯(SE)合成;采用气相色谱–质谱联用技术分析脂肪酸组成,结果显示,ELO3缺陷,C_(26)脂肪酸基本检测不到,而C_(20)与C_(22)脂肪酸会累积;ELO2缺失后,C_(26)脂肪酸的含量也明显降低。而油酸的处理会增加BY4741胞内总的极长链脂肪酸的比例;elo2Δ和elo3Δ的不饱和脂肪酸与饱和脂肪酸的比例增大;相反,过表达脂肪酸延长酶基因,与野生型菌株相比能显著降低细胞油酸的含量。模式生物脂肪酸延长酶对细胞脂质代谢及油酸胁迫响应的研究,为医学脂代谢障碍及细胞脂毒效应研究提供了基础数据。

Biomedical evidence shows that excessive fat, especially fatty acids（FA） accumulation in non-adipose tissues can cause lipid metabolism disorder, leading to cellular dysfunction or necrosis. The fatty acid elongase family participates in fatty acid metabolism, which is highly conserved in eukaryotes in fatty acid metabolism and is closely related to the metabolism of membrane lipids. However, the relationship between fatty acid elongases and cellular lipotoxic effect is unclear. In this study, Saccharomyces cerevisiae was used as our cellular model due to the advantages of easy characterization and convenient genetic manipulation in lipid metabolism. By comparing the response of fatty acid elongase-deficient elo1Δ, elo2Δ and elo3Δ with that of wild-type yeast to different fatty acids, we found that long-chain fatty acid elongases ELO2 and ELO3 defects were highly sensitive to oleic acid. Cell lipid droplets and neutral lipid metabolism played a key role in maintaining cellular lipid homeostasis. Our results showed that the synthesis defects of long chain fatty acids or oleic acid could promote formation of cell lipid droplets, and significantly enhanced the synthesis of the cellular neutral lipids（TAG） and cholesterol ester（SE）. The fatty acid composition were analyzed by gas chromatography-mass spectrometry（GC-MS）. C_（26） fatty acids were barely detected, while C_（20） and C_（22） fatty acids accumulated in elo3Δ strain. The content of C_（26） fatty acid was also decreased significantly in elo2Δ strain. However, the treatment of oleic acid increased the proportion of the total very long-chain fatty acid in the BY4741 cells, and the ratios of unsaturated fatty acids to saturated fatty acids were increased in elo2Δ and elo3Δ strains. On the contrary, the overexpression of long-chain fatty acid elongase genes could significantly reduce the content of oleic acid compared to the wild-type strain. Based on the study of the responses of fatty acid elongase defects to lipid metabolism and oleic acid stress in the model cells of Saccharomyces cerevisiae, it provides basic data for the investigation of lipid metabolism disorder and lipotoxicity effect in medicine.