Host Pah1p phosphatidate phosphatase limits viral replication by regulating phospholipid synthesis.
Host Pah1p phosphatidate phosphatase limits viral replication by regulating phospholipid synthesis.
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DOI：
10.1371/journal.ppat.1006988
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发表时间：
2018-04
期刊：
影响因子：
6.7
通讯作者：
Wang X
中科院分区：
文献类型：
--
作者：
Zhang Z;He G;Han GS;Zhang J;Catanzaro N;Diaz A;Wu Z;Carman GM;Xie L;Wang X
正链RNA病毒[（+）RNA病毒]的复制发生在膜结合病毒复制复合物（VRC）中。VRC的形成需要病毒介导的细胞脂质合成操纵。在这里，我们报告显着增强雀麦花叶病毒（BMV）的复制和大大改善的细胞生长在酵母细胞缺乏PAH 1（pah1Δ），唯一的酵母直系同源的人脂蛋白基因。PAH 1编码Pah1p（磷脂酸磷酸水解酶），其将磷脂酸（PA）转化为二酰基甘油，随后用于合成储存脂质三酰基甘油。Pah1p失活导致脂质组成改变，包括高水平的PA、总磷脂、麦角甾醇酯和游离脂肪酸，以及核膜扩张。在pah1Δ细胞中，BMV复制蛋白1a和双链RNA定位于延伸的核膜，形成的VRC数量显著增加，BMV基因组复制比野生型细胞增加2倍。在另一种既缺乏PAH 1又缺乏DGK1（编码将二酰甘油转化为PA的二酰甘油激酶）的酵母突变体中，其具有正常的核膜，但保持与pah1 Δ细胞相似的脂质组成变化，BMV复制与pah1Δ细胞一样有效，表明脂质组成的改变是BMV复制增强的原因。我们进一步表明，总磷脂水平的增加起着重要的作用，因为增强BMV复制需要积极合成的磷脂酰胆碱，主要的膜磷脂。此外，过表达的磷脂酰胆碱合成基因（CHO2）促进BMV复制。相反，PAH1或植物PAH1直系同源物的过表达抑制了酵母或本氏烟草植物中的BMV复制。BMV与宿主竞争有限的资源，抑制宿主的生长，在pah1Δ细胞中这种抑制作用明显减轻。我们的工作表明，Pah1p促进储存脂质的合成，从而抑制磷脂的合成，这反过来又限制了病毒感染过程中的病毒复制和细胞生长。磷脂酸（PA）在脂质代谢中起着至关重要的作用，因为它是主要膜组分磷脂和储存脂质三酰甘油（TAG）的共同前体。磷脂酸磷酸酶（PAP）参与通过二酰基甘油将PA转化为TAG，并在非活性生长阶段期间指导从用于细胞生长的膜合成到脂质储存的脂质通量。PAP在真核生物中结构和功能保守，从酵母中的Pah1p到哺乳动物中的脂蛋白。PAP的失活实质上影响脂质组成并引起人类疾病，如脂肪营养不良和胰岛素抗性，而PAP的过表达导致肥胖。我们发现，病毒与宿主细胞竞争有限的脂质，从而抑制宿主生长。在酵母细胞与非活性PAP，总磷脂，甾醇酯，游离脂肪酸积累到高水平的TAG为代价。改变的脂质组成在病毒复制期间显著促进细胞生长。然而，这同时增强了雀麦花叶病毒（BMV）的基因组复制，BMV是一种研究正链RNA病毒的良好模型。这些结果表明，PAP通过限制磷脂合成来限制病毒复制，而磷脂合成是病毒复制所必需的。我们的数据加强了病毒可能利用PAP或其他营养稳态被破坏的概念。
Replication of positive-strand RNA viruses [(+)RNA viruses] takes place in membrane-bound viral replication complexes (VRCs). Formation of VRCs requires virus-mediated manipulation of cellular lipid synthesis. Here, we report significantly enhanced brome mosaic virus (BMV) replication and much improved cell growth in yeast cells lacking PAH1 (pah1Δ), the sole yeast ortholog of human LIPIN genes. PAH1 encodes Pah1p (phosphatidic acid phosphohydrolase), which converts phosphatidate (PA) to diacylglycerol that is subsequently used for the synthesis of the storage lipid triacylglycerol. Inactivation of Pah1p leads to altered lipid composition, including high levels of PA, total phospholipids, ergosterol ester, and free fatty acids, as well as expansion of the nuclear membrane. In pah1Δ cells, BMV replication protein 1a and double-stranded RNA localized to the extended nuclear membrane, there was a significant increase in the number of VRCs formed, and BMV genomic replication increased by 2-fold compared to wild-type cells. In another yeast mutant that lacks both PAH1 and DGK1 (encodes diacylglycerol kinase converting diacylglycerol to PA), which has a normal nuclear membrane but maintains similar lipid compositional changes as in pah1Δ cells, BMV replicated as efficiently as in pah1Δ cells, suggesting that the altered lipid composition was responsible for the enhanced BMV replication. We further showed that increased levels of total phospholipids play an important role because the enhanced BMV replication required active synthesis of phosphatidylcholine, the major membrane phospholipid. Moreover, overexpression of a phosphatidylcholine synthesis gene (CHO2) promoted BMV replication. Conversely, overexpression of PAH1 or plant PAH1 orthologs inhibited BMV replication in yeast or Nicotiana benthamiana plants. Competing with its host for limited resources, BMV inhibited host growth, which was markedly alleviated in pah1Δ cells. Our work suggests that Pah1p promotes storage lipid synthesis and thus represses phospholipid synthesis, which in turn restricts both viral replication and cell growth during viral infection. Phosphatidate (PA) plays crucial roles in lipid metabolism because it is the shared precursor for major membrane component phospholipids and for storage lipid triacylglycerols (TAGs). Phosphatidate phosphatase (PAP) is involved in converting PA to TAG via diacylglycerol and directs the lipid flux from membrane synthesis for cell growth to lipid storage during inactive growth stages. PAP is structurally and functionally conserved among eukaryotes, from Pah1p in yeast to lipins in mammals. Inactivation of PAP substantially affects lipid composition and causes human diseases, such as lipodystrophy and insulin resistance, whereas overexpression of PAP leads to obesity. We show that viruses compete with host cells for limited lipids, inhibiting host growth as a consequence. In yeast cells with inactive PAP, total phospholipids, sterol esters, and free fatty acids accumulated to high levels at the expense of TAG. Altered lipid composition substantially promotes cell growth during viral replication. However, this simultaneously enhances genomic replication of brome mosaic virus (BMV), a well-studied model for examining positive-strand RNA viruses. These results suggest that PAP restricts virus replication by limiting phospholipid synthesis, which is required for viral replication. Our data strengthen the notion that viruses may take advantage of disrupted PAP or other nutrient homeostasis for infection.
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