Identification and biophysical characterization of a very-long-chain-fatty-acid-substituted phosphatidylinositol in yeast subcellular membranes
Identification and biophysical characterization of a very-long-chain-fatty-acid-substituted phosphatidylinositol in yeast subcellular membranes
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DOI：
10.1042/bj20040320
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发表时间：
2004-08-01
影响因子：
4.1
通讯作者：
Epand, RM
中科院分区：
文献类型：
--
作者：
Schneiter, R;Brügger, B;Epand, RM
对酵母乙酰辅酶a羧化酶acc1(ts)/mtr7（脂肪酸合成限速酶）条件突变体的形态学分析表明，C-26 VLCFAs（长链脂肪酸）的合成对维持核膜的结构和功能至关重要。为了更详细地描述这种依赖C-26的途径，我们现在检查了在需要C-26的途径中被阻断的细胞。在酵母中，神经酰胺合成和GPI（糖基磷脂酰肌醇）锚定的重塑是将C-26纳入脂质的两条途径。在神经酰胺合成或GPI锚点合成中受阻的条件突变体不会表现出acc1（ts）中观察到的核膜的特征性改变，这表明acc1（ts）突变细胞中另一种含c -26脂质的合成可能受到影响。分离核膜的脂质分析显示存在一种新的c -26取代PI（磷脂酰肌醇）。这个C-26-PI大约占。占所有PI物种的1%，并且存在于核和质膜中。值得注意的是，这种C-26-PI是唯一在野生型酵母中可食用的含c -26的甘油磷脂，并且c -26取代对甘油主链的sn - 1位置具有高度特异性。为了表征这种脂质的生物物理性质，对其进行了化学合成。与含有正常长链脂肪酸（C-16或C-18）的pi相比，C-26-PI大大减少了由1,2-二烯二酰基- n-甘油-3-磷酸乙醇胺（DEPE）组成的脂质体的双层到六方相变。因此，这种脂质的生物物理性质与稳定高弯曲膜结构域的可能作用一致。
Morphological analysis of a conditional yeast mutant in acetylCoA carboxylase acc1(ts)/mtr7, the rate-limiting enzyme of fatty acid synthesis, suggested that the synthesis of C-26 VLCFAs (very-long-chain fatty acids) is important for maintaining the structure and function of the nuclear membrane. To characterize this C-26-dependent pathway in more detail, we have now examined cells that are blocked in pathways that require C-26. In yeast, ceramide synthesis and remodelling of GPI (glycosylphosphatidylinositol)-anchors are two pathways that incorporate C-26 into lipids. Conditional mutants blocked in either ceramide synthesis or the synthesis of GPI anchors do not display the characteristic alterations of the nuclear envelope observed in acc1(ts), indicating that the synthesis of another C-26-containing lipid may be affected in acc1(ts) mutant cells. Lipid analysis of isolated nuclear membranes revealed the presence of a novel C-26-substituted PI (phosphatidylinositol). This C-26-PI accounts for approx. 1 % of all the PI species, and is present in both the nuclear and the plasma membrane. Remarkably, this C-26-PI is the only C-26-containing glycerophospholipid that is delectable in wild-type yeast, and the C-26-substitution is highly specific for the sn - 1 position of the glycerol backbone. To characterize the biophysical properties of this lipid, it was chemically synthesized. In contrast to PIs with normal long-chain fatty acids (C-16 or C-18), the C-26-PI greatly reduced the bilayer to hexagonal phase transition of liposomes composed of 1,2-dielaidoyl-sn-glycero-3-phosphoethanolamine (DEPE). The biophysical properties of this lipid are thus consistent with a possible role in stabilizing highly curved membrane domains.