Roles of phosphatidylethanolamine and of its several biosynthetic pathways in Saccharomyces cerevisiae
Roles of phosphatidylethanolamine and of its several biosynthetic pathways in Saccharomyces cerevisiae
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DOI：
10.1091/mbc.12.4.997
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发表时间：
2001-04-01
影响因子：
3.3
通讯作者：
Daum, G
中科院分区：
文献类型：
--
作者：
Birner, R;Bürgermeister, M;Daum, G
三种不同的途径导致磷脂酰乙醇胺（PtdEtn）在酵母中的合成，其中之一是定位于线粒体内膜。为了研究这些途径中的每一个的贡献，我们构建了一系列缺失突变体，其中途径的不同组合被阻断。对它们的生长表型的分析表明，最低水平的PtdEtn对生长是必不可少的。在可发酵碳源如葡萄糖上，鞘脂催化剂提供的内源性乙醇胺磷酸盐足以允许通过胞苷二磷酸（CDP）-乙醇胺途径合成必需量的PtdEtn。然而，在不可发酵的碳源上，生长需要更高水平的PtdEtn，并且通过CDP-乙醇胺途径和线粒体外磷脂酰丝氨酸脱羧酶2产生的PtdEtn的量不足以维持生长，除非通过用乙醇胺补充生长培养基来增强前一途径的作用。因此，在缺乏这种补充的情况下，线粒体磷脂酰丝氨酸脱羧酶1产生PtdEtn变得至关重要。在psd 1三角洲菌株或cho 1三角洲菌株（磷脂酰丝氨酸合成缺陷），其中含有减少量的PtdEtn，在不可发酵的碳源上的生长速率与线粒体中PtdEtn的含量相关，这表明PtdEtn进入这个细胞器的进口成为生长限制。虽然形态学和生化分析显示PtdEtn耗尽线粒体没有明显的缺陷，突变体表现出增强的呼吸缺陷细胞的形成。糖基磷脂酰肌醇锚定蛋白的合成也受损PtdEtn耗尽的细胞，表现为Gas 1 p的成熟延迟。另一方面，羧肽酶Y和转化酶以野生型动力学进行加工。因此，PtdEtn消耗一般不影响蛋白质分泌，表明高水平的非双层形成脂质如PtdEtn对于体内膜囊泡融合过程不是必需的。
Three different pathways lead to the synthesis of phosphatidylethanolamine (PtdEtn) in yeast, one of which is localized to the inner mitochondrial membrane. To study the contribution of each of these pathways, we constructed a series of deletion mutants in which different combinations of the pathways are blocked. Analysis of their growth phenotypes revealed that a minimal level of PtdEtn is essential for growth. On fermentable carbon sources such as glucose, endogenous ethanolaminephosphate provided by sphingolipid catabolism is sufficient to allow synthesis of the essential amount of PtdEtn through the cytidyldiphosphate (CDP)-ethanolamine pathway. On nonfermentable carbon sources, however, a higher level of PtdEtn is required for growth, and the amounts of PtdEtn produced through the CDP-ethanolamine pathway and by extramitochondrial phosphatidylserine decarboxylase 2 are not sufficient to maintain growth unless the action of the former pathway is enhanced by supplementing the growth medium with ethanolamine. Thus, in the absence of such supplementation, production of PtdEtn by mitochondrial phosphatidylserine decarboxylase 1 becomes essential. In psd1 Delta strains or cho1 Delta strains (defective in phosphatidylserine synthesis), which contain decreased amounts of PtdEtn, the growth rate on nonfermentable carbon sources correlates with the content of PtdEtn in mitochondria, suggesting that import of PtdEtn into this organelle becomes growth limiting. Although morphological and biochemical analysis revealed no obvious defects of PtdEtn-depleted mitochondria, the mutants exhibited an enhanced formation of respiration-deficient cells. Synthesis of glycosylphosphatidylinositol-anchored proteins is also impaired in PtdEtn-depleted cells, as demonstrated by delayed maturation of Gas1p. Carboxypeptidase Y and invertase, on the other hand, were processed with wild-type kinetics. Thus, PtdEtn depletion does not affect protein secretion in general, suggesting that high levels of nonbilayer-forming lipids such as PtdEtn are not essential for membrane vesicle fusion processes in vivo.