Shape changes and vesicle fission of giant unilamellar vesicles of liquid-ordered phase membrane induced by lysophosphatidylcholine.
Shape changes and vesicle fission of giant unilamellar vesicles of liquid-ordered phase membrane induced by lysophosphatidylcholine.
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DOI：
10.1021/la049481g
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发表时间：
2004-09
期刊：
影响因子：
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通讯作者：
Tomoki Tanaka;R. Sano;Y. Yamashita;M. Yamazaki
中科院分区：
文献类型：
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作者：
Tomoki Tanaka;R. Sano;Y. Yamashita;M. Yamazaki
脂膜的液态相是介于液晶相和凝胶相之间的中间相，在生物学和生物物理方面都引起了人们的广泛关注。位于生物膜L0期的木筏在哺乳动物细胞的信号转导等细胞功能中发挥着重要作用。在本报告中，我们制备了LO相脂膜的巨大单层囊泡(GUV)，并用相差显微镜和荧光显微镜研究了其物理性质。在20-37℃，当胆固醇含量为30%时，成功地形成了二棕榈酰磷脂酰胆碱(DPPC)/胆固醇膜和鞘磷脂(SM)/胆固醇膜。DPPC/胆固醇和SM/胆固醇膜的直径在50℃到28℃之间没有变化，支持这些膜处于LO相。为了阐明具有长碳氢链的物质与低相膜的相互作用，我们研究了低浓度(小于临界胶束浓度)溶血磷脂酰胆碱(Lyso-PC)与DPPC/胆固醇GUV和SM/胆固醇GUV在LO相中的相互作用。我们发现，Lyso-PC诱导了这些GUV在水中超过其阈值浓度的几次形状变化和囊泡分裂。对这些形状变化的分析表明，LYSO-PC可以从水溶液中分配到GUV的L0相中的外部单分子膜中。随着Llyso-PC链长的减小，Llyso-PC在水中诱导形状改变和囊泡分裂的阈值浓度大大增加。热力学分析结果表明，当膜中Lyso-PC的阈值浓度达到一定值时，膜会发生形状变化和囊泡分裂。这些对低相膜GUVS的新发现表明，具有长碳氢链的物质，如Lyso-PC，可以进入低相膜，也可以进入细胞膜中的浮筏。我们还提出了Llyso-PC诱导GUV囊泡分裂的机制。
Liquid-ordered phase (lo phase) of lipid membranes has properties that are intermediate between those of liquid-crystalline phase and those of gel phase and has attracted much attention in both biological and biophysical aspects. Rafts in the lo phase in biomembranes play important roles in cell function of mammalian cells such as signal transduction. In this report, we have prepared giant unilamellar vesicles (GUVs) of lipid membranes in the lo phase and investigated their physical properties using phase-contrast microscopy and fluorescence microscopy. GUVs of dipalmitoyl-phosphatidylcholine (DPPC)/cholesterol membranes and also GUVs of sphingomyelin (SM)/cholesterol membranes in the lo phase in water were formed at 20-37 degrees C successfully, when these membranes contained >/=30 mol % cholesterol. The diameters of GUVs of DPPC/cholesterol and SM/cholesterol membranes did not change from 50 to 28 degrees C, supporting that the membranes of these GUVs were in the lo phase. To elucidate the interaction of a substance with a long hydrocarbon chain with the lo phase membrane, we investigated the interaction of low concentrations (less than critical micelle concentration) of lysophosphatidylcholine (lyso-PC) with DPPC/cholesterol GUVs and SM/cholesterol GUVs in the lo phase. We found that lyso-PC induced several shape changes and vesicle fission of these GUVs above their threshold concentrations in water. The analysis of these shape changes indicates that lyso-PC can be partitioned into the external monolayer in the lo phase of the GUV from the aqueous solution. Threshold concentrations of lyso-PC in water to induce the shape changes and vesicle fission increased greatly with a decrease in chain length of lyso-PC. Thermodynamic analysis of this result indicates that shape changes and vesicle fission occur at threshold concentrations of lyso-PC in the membrane. These new findings on GUVs of the lo phase membranes indicate that substances with a long hydrocarbon chain such as lyso-PC can enter into the lo phase membrane and also the raft in the cell membrane. We have also proposed a mechanism for the lyso-PC-induced vesicle fission of GUVs.