Formation of Cell-like liposome encapsulated cytoskeletons.

为了研究细胞骨架是否能决定细胞的形状，我们构建了含有微管或微丝亚基蛋白的脂质体。脂质体是单层或多层的脂质双层囊泡。通过提高温度，包被的微管蛋白或g -肌动蛋白分别聚合成微管或肌动蛋白丝（f -肌动蛋白）。当被包裹的微管蛋白聚合形成微管时，脂质体转变成柠檬形状。然后，两个管状膜突起从柠檬形脂质体的两侧发育，突起变长。这两个凸出的部分都是直的、坚硬的、直径均匀的，并在一条直线上对齐。最后，脂质体转化为偶极体状脂质体，其中心有一个球体和两个直管。当被包裹的肌动蛋白聚合成肌动蛋白丝时，脂质体转变成具有几何对称性的圆盘状或哑铃状。在脂质体中聚合的肌动蛋白丝自发地沿着脂质体的外围排列成束。微管或肌动蛋白丝的伸长引起脂质体的形态变化，说明细胞骨架自身的自组装过程可以产生足以使膜变形的机械力。微管和肌动蛋白丝的刚性有很大的不同。当它们自组装时，它们彼此之间会产生不同程度的机械力。这些特征可能导致脂质体形状的差异。

To study whether the cytoskeleton can determine the shape of cells, we constructed the liposome which contained subunit proteins of microtubules or microfilaments. Liposome are single or multi-layred vesicles of lipid bilayr.By raising the temperature, the encapsulated tubulin or G-actin was polymerized to microtubules or actin filaments (F-actin), respectively. As the encapsulated tubulin polymerized forming microtubules, the liposome transformed into a lemon shape. Two tubular membrane projections then developed from both sides of the lemon-shaped liposome and the projections grew longer. Both of the projections were straight, rigid, uniform in diameter and aligned on a line. Finally, the liposome transformed into a dipolar-shaped liposome, which had a central sphere and two straight tubes.When the encapsulated actin polymerized into actin filaments, the liposome transformed into a disk or dumbbell shape which has geometrical symmetry. The actin filaments polymerized in the liposome spontaneously aligned along the periphery of the liposome to form bundles. Elongation of microtubules or actin filaments caused morphological changes of the liposomes, indicating that the self-assembly process of the cytoskeletons itself can generate the mechanical force strong enough to deform membranes. Microtubule and actin filament are quite different in their rigidity. They may generate mechanical force in different amount with each other, when they self-assemble. These characteristics mighy cause the difference in the liposome shape.