De novo sphingolipid synthesis is essential for viability, but not for transport of glycosylphosphatidylinositol-anchored proteins, in African trypanosomes
De novo sphingolipid synthesis is essential for viability, but not for transport of glycosylphosphatidylinositol-anchored proteins, in African trypanosomes
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DOI：
10.1128/ec.00283-06
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发表时间：
2007-03-01
期刊：
影响因子：
--
通讯作者：
Bangs, James D.
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文献类型：
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作者：
Sutterwala, Shaheen S.;Creswell, Caleb H.;Bangs, James D.
在酵母中，糖基磷脂酰肌醇(GPI)锚定的膜蛋白需要重新合成鞘磷脂才能离开内质网。使用药理学的方法，我们通过分析GPI锚定的货物在以非洲锥体和HeLa细胞为代表的广泛差异的真核系统中的运输来检验这种现象的普遍性。Myriocin阻断了鞘磷脂合成的第一步(丝氨酸+棕榈酸酯-GT；3-酮二氢鞘氨醇)，抑制了培养的血液寄生虫的生长，外源3-酮二氢鞘氨醇挽救了生长。Myriocin还阻止[H-3]丝氨酸进入耐碱的鞘磷脂。生化分析表明，放射性标记的脂类不是鞘磷脂或肌醇磷酸化神经酰胺，这表明血流锥虫合成了新的鞘磷脂。用myriocin抑制神经鞘糖脂的合成对锥虫的一般分泌转运和依赖于GPI的转运都没有不良影响，在HeLa细胞中也得到了类似的结果。在与霉菌素长期孵育后，血流锥虫对内吞作用有轻微影响。这些结果表明，神经鞘脂的从头合成不是真核细胞分泌运输的一般要求。然而，与密切相关的大利什曼原虫不同，从头合成鞘脂对于血流阶段的非洲锥虫的生存是必不可少的。
De novo sphingolipid synthesis is required for the exit of glycosylphosphatidylinositol (GPI)-anchored membrane proteins from the endoplasmic reticulum in yeast. Using a pharmacological approach, we test the generality of this phenomenon by analyzing the transport of GPI-anchored cargo in widely divergent eukaryotic systems represented by African trypanosomes and HeLa cells. Myriocin, which blocks the first step of sphingolipid synthesis (serine + palmitate -> 3-ketodihydrosphingosine), inhibited the growth of cultured bloodstream parasites, and growth was rescued with exogenous 3-ketodihydrosphingosine. Myriocin also blocked metabolic incorporation of [H-3] serine into base-resistant sphingolipids. Biochemical analyses indicate that the radiolabeled lipids are not sphingomyelin or inositol phosphorylceramide, suggesting that bloodstream trypanosomes synthesize novel sphingolipids. Inhibition of de novo sphingolipid synthesis with myriocin had no adverse effect on either general secretory trafficking or GPI-dependent trafficking in trypanosomes, and similar results were obtained with HeLa cells. A mild effect on endocytosis was seen for bloodstream trypanosomes after prolonged incubation with myriocin. These results indicate that de novo synthesis of sphingolipids is not a general requirement for secretory trafficking in eukaryotic cells. However, in contrast to the closely related kinetoplastid Leishmania major, de novo sphingolipid synthesis is essential for the viability of bloodstream-stage African trypanosomes.