Surface tension induced by sphingomyelin to ceramide conversion in lipid membranes
Surface tension induced by sphingomyelin to ceramide conversion in lipid membranes
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DOI：
10.1016/j.bbamem.2007.01.001
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发表时间：
2007-03-01
影响因子：
3.4
通讯作者：
Devaux, Philippe F.
中科院分区：
文献类型：
--
作者：
Lopez-Montero, Ivan;Velez, Marisela;Devaux, Philippe F.
我们利用巨型单层囊泡（GUVs）研究了鞘磷脂（SM）对神经酰胺酶转化对脂质双分子层的影响。鞘磷脂酶被添加到含有不同比例SM的guv中。原位不对称SM转化为神经酰胺减少了单叶面积。在没有平衡的所有脂质之间的两个小叶，一个不匹配的两个单层之间产生。这种不匹配产生的张力足以在相对较低的SM百分比（约5% mol）下触发膜缺陷的形成和总囊泡的崩溃。用原子力显微镜观察了支撑层中纳米级缺陷的形成。在两种情况下可以防止囊泡破裂：(a)含有l(d)和l(o)结构域的guv和(b)含有5%溶血磷脂酰胆碱的guv。在这两种情况下，足够的神经酰胺的积累（初始SM浓度为10%）允许形成富含神经酰胺的区域。两个不对称单层膜之间的耦合和新形成的神经酰胺产生的冷凝效应产生了张力，这可能是神经酰胺形成诱导细胞凋亡后期细胞膜修饰的机制的基础。(c) 2007 Elsevier B.V.版权所有
We have investigated the effect of sphingomyelin (SM) to ceramide enzymatic conversion on lipid bilayers using Giant Unilamellar Vesicles (GUVs). Sphingomyelinase was added externally to GUVs containing various proportions of SM. In situ asymmetrical SM conversion to ceramide reduced the area of one leaflet. In the absence of equilibration of all the lipids between the two leaflets, a mismatch between the two monolayers was generated. The tension generated by this mismatch was sufficient to trigger the formation of membrane defects and total vesicle collapse at relatively low percentage of SM (approximate to 5% mol). The formation of nanometric size defects was visualised by AFM in supported bilayers. Vesicle rupture was prevented in two circumstances: (a) in GUVs containing a mixture of l(d) and l(o) domains and (b) in GUVs containing 5% lysophosphatidylcholine. In both cases, the accumulation of enough ceramide (at initial SM concentration of 10%) allowed the formation of ceramide-rich domains. The coupling between the two asymmetrical monolayers and the condensing effect produced by the newly formed ceramide generated a tension that could underlie the mechanism through which ceramide formation induces membrane modifications observed during the late stages of apoptosis. (c) 2007 Elsevier B.V. All rights reserved.