Rouven Brückner Bastian, Pietuch Anna, Nehls Stefan, Rother Jan, Janshoff Andreas
Institute of Physical Chemistry, University of Goettingen, Tammannstr. 6, 37077 Goettingen.
Sci Rep. 2015 Oct 5;5:14700. doi: 10.1038/srep14700.
Plasma membrane tension is responsible for a variety of cellular functions such as motility, cell division, and endocytosis. Since membrane tension is dominated by the attachment of the actin cortex to the inner leaflet of the plasma membrane, we investigated the importance of ezrin, a major cross-linker of the membrane-cytoskeleton interface, for cellular mechanics of confluent MDCK II cells. For this purpose, we carried out ezrin depletion experiments and also enhanced the number of active ezrin molecules at the interface. Mechanical properties were assessed by force indentation experiments followed by membrane tether extraction. PIP2 micelles were injected into individual living cells to reinforce the linkage between plasma membrane and actin-cortex, while weakening of this connection was reached by ezrin siRNA and administration of the inhibitors neomycin and NSC 668394, respectively. We observed substantial stiffening of cells and an increase in membrane tension after addition of PIP2 micelles. In contrast, reduction of active ezrin led to a decrease of membrane tension accompanied by loss of excess surface area, increase in cortical tension, remodelling of actin cytoskeleton, and reduction of cell height. The data confirm the importance of the ezrin-mediated connection between plasma membrane and cortex for cellular mechanics and cell morphology.
质膜张力负责多种细胞功能，如运动性、细胞分裂和内吞作用。由于膜张力主要由肌动蛋白皮质与质膜内小叶的附着所主导，我们研究了埃兹蛋白（膜 - 细胞骨架界面的主要交联蛋白）对汇合的MDCK II细胞细胞力学的重要性。为此，我们进行了埃兹蛋白缺失实验，并增加了界面处活性埃兹蛋白分子的数量。通过力压痕实验和随后的膜系链提取来评估力学性能。将磷脂酰肌醇 - 4,5 - 二磷酸（PIP2）微团注入单个活细胞以加强质膜与肌动蛋白皮质之间的连接，而分别通过埃兹蛋白小干扰RNA（siRNA）以及施用抑制剂新霉素和NSC 668394来削弱这种连接。我们观察到添加PIP2微团后细胞显著变硬且膜张力增加。相反，活性埃兹蛋白的减少导致膜张力降低，同时伴随着多余表面积的丧失、皮质张力增加、肌动蛋白细胞骨架重塑以及细胞高度降低。这些数据证实了埃兹蛋白介导的质膜与皮质之间的连接对细胞力学和细胞形态的重要性。
