SHAPE CHANGES OF GIANT LIPOSOMES INDUCED BY AN ASYMMETRIC TRANSMEMBRANE DISTRIBUTION OF PHOSPHOLIPIDS
SHAPE CHANGES OF GIANT LIPOSOMES INDUCED BY AN ASYMMETRIC TRANSMEMBRANE DISTRIBUTION OF PHOSPHOLIPIDS
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DOI：
10.1016/s0006-3495(92)81841-6
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发表时间：
1992-02-01
影响因子：
3.4
通讯作者：
DEVAUX, PF
中科院分区：
文献类型：
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作者：
FARGE, E;DEVAUX, PF
在固定温度下，通过光学显微镜研究了磷脂跨膜再分布对非球形松弛囊泡形状的影响。在第一系列实验中，跨膜pH梯度施加在卵磷脂酰胆碱（EPC）-卵磷脂酰甘油（EPG）（100：1）巨囊泡上。Δ-pH诱导EPG的不对称分布。同时，盘状囊泡转变为管状或一系列相连的小囊泡。从盘状到两个连接的囊泡的形状变化所需的磷脂转移的分数是总磷脂的0.1%的顺序。额外的脂质再分布伴随着一系列的形状变化。在第二系列实验中，将溶血磷脂酰胆碱（L-PC）添加到巨大EPC囊泡的外部小叶中或从外部小叶中减去。添加L-PC诱导从盘状到两个囊泡状态的变化，而没有进一步的演变，这表明脂质转移和脂质添加是不等价的。L-PC从外叶消耗产生的口细胞样囊泡。只要有可能，我们就通过微量吸管测定法测量弹性面积压缩模量K来确定发生形状变化的巨囊泡是单层还是多层（Kwok和Evans，1981）。最外部双层的磷脂修饰引发的形状转换确实受到其他底层膜的存在的影响，这些膜起到了与被动细胞骨架层相当的作用。看来在真实的细胞中，质膜的内陷或细胞器的出芽可能是由磷脂从一个小叶转移到另一个小叶引起的，例如，由真核细胞膜中存在的氨基磷脂移位酶引起的。
The influence of a phospholipid transmembrane redistribution on the shape of nonspherical flaccid vesicles was investigated at a fixed temperature by optical microscopy. In a first series of experiments, a transmembrane pH gradient was imposed on egg phosphatidylcholine (EPC)-egg phosphatidylglycerol (EPG) (100:1) giant vesicles. The DELTA-pH induced an asymmetric distribution of EPG. Simultaneously, discoid vesicles were transformed into tubular or a series of connected small vesicles. The fraction of phospholipid transfer necessary for a shape change from discoid to two connected vesicles was of the order of 0.1% of the total phospholipids. Additional lipid redistribution was accompanied by a sequence of shape changes. In a second series of experiments, lyso phosphatidylcholine (L-PC) was added to, or subtracted from, the external leaflet of giant EPC vesicles. The addition of L-PC induced a change from discoid to a two-vesicle state without further evolution, suggesting that lipid transfer and lipid addition are not equivalent. L-PC depletion from the outer leaflet generated stomatocyte-like vesicles. Whenever possible, we have determined whether the giant vesicles undergoing shape changes were unilamellar or multilamellar by measuring the elastic area compressibility modulus, K, by the micropipette assay (Kwok and Evans, 1981). Shape transformations triggered by phospholipid modification of the most external bilayer were indeed influenced by the presence of other underlying membranes that played a role comparable to that of a passive cytoskeleton layer. It appears that in real cells, invaginations of the plasma membrane or budding of organelles could be triggered by a phospholipid transfer from one leaflet to the other caused, for instance, by the aminophospholipid translocase which is present in eukaryotic membranes.