C26-CoA-dependent ceramide synthesis of Saccharomyces cerevisiae is operated by Lag1p and Lac1p
C26-CoA-dependent ceramide synthesis of Saccharomyces cerevisiae is operated by Lag1p and Lac1p
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DOI：
10.1093/emboj/20.11.2655
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发表时间：
2001-06-01
期刊：
影响因子：
11.4
通讯作者：
Conzelmann, A
中科院分区：
文献类型：
--
作者：
Guillas, I;Kirchman, PA;Conzelmann, A
Lag1p和Lac1p是两种高度同源的内质网膜蛋白。当这两个基因被删除，细胞不能运输糖基磷脂酰肌醇（GPI）锚定蛋白质从ER到高尔基体在正常的速度。在这里，我们表明，微粒体或洗涤剂提取物从lag1三角洲lac1三角洲双突变体缺乏活性转移C26脂肪酸从C26辅酶A到二氢鞘氨醇或植物鞘氨醇。因此，在完整的细胞中，正常的神经酰胺和肌醇磷酸神经酰胺急剧减少。lag1 Δ lacl Δ细胞通过增加C26脂肪酸的量来补偿正常鞘脂的缺乏，C26脂肪酸被并入甘油磷脂中。它们还含有比野生型多20至25倍的游离长链碱基，并积累非常大量的异常极性神经酰胺，它们产生少量异常的轻度耐碱性肌醇磷脂。在lag 1 Delta lac1 Delta双突变体中，GPI锚定蛋白的脂质重塑受到严重损害，因为只有很少且大多数异常的神经酰胺被掺入GPI锚中。Lag1p和Lac1p参与神经酰胺的合成可以解释它们在决定寿命方面的作用。
Lag1p and Lac1p are two highly homologous membrane proteins of the endoplasmic reticulum (ER). When both genes are deleted, cells cannot transport glycosylphosphatidylinositol (GPI)-anchored proteins from the ER to the Golgi at a normal rate. Here we show that microsomes or detergent extracts from lag1 Delta lac1 Delta double mutants lack an activity transferring C26 fatty acids from C26-coenzyme A onto dihgdrosphingosine or phytosphingosine. As a consequence, in intact cells, the normal ceramides and inositolphosphorylceramides are drastically reduced. lag1 Delta lacl Delta cells compensate for the lack of normal sphingolipids by making increased amounts of C26 fatty acids, which become incorporated into glycerophospholipids. They also contain 20- to 25-fold more free long chain bases than wild type and accumulate very large amounts of abnormally polar ceramides, They make small amounts of abnormal mild base-resistant inositolphospholipids. The lipid remodelling of GPI-anchored proteins is severely compromised in lag1 Delta lac1 Delta double mutants since only few and mostly abnormal ceramides are incorporated into the GPI anchors. The participation of Lag1p and Lac1p in ceramide synthesis may explain their role in determining longevity.