Mechanics of Biomimetic Liposomes Encapsulating an Actin Shell.
Mechanics of Biomimetic Liposomes Encapsulating an Actin Shell.
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DOI：
10.1016/j.bpj.2015.10.050
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发表时间：
2015-12-15
影响因子：
3.4
通讯作者：
Sykes C
中科院分区：
文献类型：
--
作者：
Guevorkian K;Manzi J;Pontani LL;Brochard-Wyart F;Sykes C
细胞形状的变化是由细胞膜下面的一层薄的、动态的、皮质的细胞骨架保证的。这种薄的皮质结构如何影响整个细胞的机械特性还没有完全了解。在这里，我们研究的力学脂质体或巨大的单层囊泡，当一个仿生肌动蛋白皮质生长在内层的脂质膜通过肌动蛋白成核促进因子。使用流体动力学管拉技术，我们表明，管动力学明显受到锚定到脂质双层的肌动蛋白壳的存在下。与裸膜相比，在肌动蛋白壳存在下，相同的力拉动短得多的管。然而，在这两种情况下，我们观察到管挤出的动力学具有粘弹性材料的两个明显特征：快速弹性伸长，随后是恒定速率的较慢伸长阶段。我们解释的初始弹性制度的膜张力增加，由于进入管的脂质损失。在相当的拉力下，皮质脂质体的管长度明显较短，导致弹簧常数较高。肌动蛋白壳的存在似乎限制了脂质的流动性，正如在细胞中的畜栏效应中所观察到的那样。裸脂质体的粘性状态对应于恒定膜张力下内部液体的泄漏。肌动蛋白壳的存在导致更大的摩擦系数。当从片状表面拉出管时，膜张力局部增加，导致脂质的马兰戈尼流。作为结论，肌动蛋白壳的存在是通过其改变膜力学的作用来揭示的。
Cell-shape changes are insured by a thin, dynamic, cortical layer of cytoskeleton underneath the plasma membrane. How this thin cortical structure impacts the mechanical properties of the whole cell is not fully understood. Here, we study the mechanics of liposomes or giant unilamellar vesicles, when a biomimetic actin cortex is grown at the inner layer of the lipid membrane via actin-nucleation-promoting factors. Using a hydrodynamic tube-pulling technique, we show that tube dynamics is clearly affected by the presence of an actin shell anchored to the lipid bilayer. The same force pulls much shorter tubes in the presence of the actin shell compared to bare membranes. However, in both cases, we observe that the dynamics of tube extrusion has two distinct features characteristic of viscoelastic materials: rapid elastic elongation, followed by a slower elongation phase at a constant rate. We interpret the initial elastic regime by an increase of membrane tension due to the loss of lipids into the tube. Tube length is considerably shorter for cortex liposomes at comparable pulling forces, resulting in a higher spring constant. The presence of the actin shell seems to restrict lipid mobility, as is observed in the corral effect in cells. The viscous regime for bare liposomes corresponds to a leakout of the internal liquid at constant membrane tension. The presence of the actin shell leads to a larger friction coefficient. As the tube is pulled from a patchy surface, membrane tension increases locally, leading to a Marangoni flow of lipids. As a conclusion, the presence of an actin shell is revealed by its action that alters membrane mechanics.