Vysochan Anna, Sengupta Arjun, Weljie Aalim M, Alwine James C, Yu Yongjun
Department of Cancer Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104.
Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104.
Proc Natl Acad Sci U S A. 2017 Feb 21;114(8):E1528-E1535. doi: 10.1073/pnas.1614268114. Epub 2017 Feb 6.
Recent studies have shown that human cytomegalovirus (HCMV) can induce a robust increase in lipid synthesis which is critical for the success of infection. In mammalian cells the central precursor for lipid biosynthesis, cytosolic acetyl CoA (Ac-CoA), is produced by ATP-citrate lyase (ACLY) from mitochondria-derived citrate or by acetyl-CoA synthetase short-chain family member 2 (ACSS2) from acetate. It has been reported that ACLY is the primary enzyme involved in making cytosolic Ac-CoA in cells with abundant nutrients. However, using CRISPR/Cas9 technology, we have shown that ACLY is not essential for HCMV growth and virally induced lipogenesis. Instead, we found that in HCMV-infected cells glucose carbon can be used for lipid synthesis by both ACLY and ACSS2 reactions. Further, the ACSS2 reaction can compensate for the loss of ACLY. However, in ACSS2-KO human fibroblasts both HCMV-induced lipogenesis from glucose and viral growth were sharply reduced. This reduction suggests that glucose-derived acetate is being used to synthesize cytosolic Ac-CoA by ACSS2. Previous studies have not established a mechanism for the production of acetate directly from glucose metabolism. Here we show that HCMV-infected cells produce more glucose-derived pyruvate, which can be converted to acetate through a nonenzymatic mechanism.
最近的研究表明，人类巨细胞病毒（HCMV）可诱导脂质合成显著增加，这对感染的成功至关重要。在哺乳动物细胞中，脂质生物合成的核心前体——胞质乙酰辅酶A（Ac-CoA），由线粒体衍生的柠檬酸通过ATP-柠檬酸裂解酶（ACLY）产生，或由乙酸通过乙酰辅酶A合成酶短链家族成员2（ACSS2）产生。据报道，在营养丰富的细胞中，ACLY是参与生成胞质Ac-CoA的主要酶。然而，利用CRISPR/Cas9技术，我们发现ACLY对HCMV生长和病毒诱导的脂肪生成并非必不可少。相反，我们发现，在HCMV感染的细胞中，葡萄糖碳可通过ACLY和ACSS2反应用于脂质合成。此外，ACSS2反应可补偿ACLY的缺失。然而，在ACSS2基因敲除的人成纤维细胞中，HCMV诱导的葡萄糖脂肪生成和病毒生长均大幅降低。这种降低表明，葡萄糖衍生的乙酸正被ACSS2用于合成胞质Ac-CoA。先前的研究尚未确立直接从葡萄糖代谢产生乙酸的机制。在此我们表明，HCMV感染的细胞会产生更多葡萄糖衍生的丙酮酸，其可通过非酶机制转化为乙酸。
