Phosphatidylinositol 4,5-Bisphosphate Alters the Number of Attachment Sites between Ezrin and Actin Filaments A COLLOIDAL PROBE STUDY*
Phosphatidylinositol 4,5-Bisphosphate Alters the Number of Attachment Sites between Ezrin and Actin Filaments A COLLOIDAL PROBE STUDY*
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DOI：
10.1074/jbc.m113.530659
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发表时间：
2014-04-04
影响因子：
4.8
通讯作者：
Steinem, Claudia
中科院分区：
文献类型：
--
作者：
Braunger, Julia A.;Brueckner, Bastian R.;Steinem, Claudia
背景：Ezrin可以在质膜和细胞骨架之间建立动态连接。结果如下：埃兹蛋白和F-肌动蛋白之间的单个键强度很小，但磷脂酰肌醇4，5-二磷酸（PIP 2）显著改变了附着位点的数量。结论：PIP 2通过激活ezrin建立了多种弱的ezrin/F-actin相互作用。重要性：质膜张力由ezrin/F-actin相互作用维持。质膜和肌动蛋白细胞骨架之间的直接连接由ezrin蛋白控制，该蛋白是ezrin-radixin-moesin蛋白家族的成员。为了作为膜-细胞骨架连接体发挥作用，ezrin需要在涉及ezrin与磷脂酰肌醇4，5-二磷酸（PIP 2）结合和保守的苏氨酸残基磷酸化的过程中被激活。在这里，我们使用胶体探针显微镜定量分析ezrin和F-肌动蛋白作为这些激活因子的功能之间的相互作用。我们表明，测得的个人之间的ezrin和F-肌动蛋白的解结合力是独立的激活参数，在约50皮牛顿的范围内。然而，在PIP 2的存在下，累积粘附能大大增加，表明埃兹蛋白和F-肌动蛋白之间形成了大量的键。相比之下，磷酸化状态，所代表的磷酸化模拟突变体的ezrin，只发挥了很小的作用，在激活过程中。这些结果与体内实验一致，表明PIP 2浓度的增加将更多的埃兹蛋白募集到极化细胞的顶端质膜，并显著增加膜张力，该膜张力用作质膜和F-肌动蛋白网络之间粘附位点的量度。
Background: Ezrin can establish a dynamic linkage between plasma membrane and cytoskeleton. Results: The individual bond strength between ezrin and F-actin is small, but the number of attachment sites is significantly altered by phosphatidylinositol 4,5-bisphosphate (PIP2). Conclusion: PIP2 activates ezrin to establish multiple weak ezrin/F-actin interactions. Significance: Plasma membrane tension is maintained by ezrin/F-actin interactions.Direct linkage between the plasma membrane and the actin cytoskeleton is controlled by the protein ezrin, a member of the ezrin-radixin-moesin protein family. To function as a membrane-cytoskeleton linker, ezrin needs to be activated in a process that involves binding of ezrin to phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphorylation of a conserved threonine residue. Here, we used colloidal probe microscopy to quantitatively analyze the interaction between ezrin and F-actin as a function of these activating factors. We show that the measured individual unbinding forces between ezrin and F-actin are independent of the activating parameters, in the range of approximately 50 piconewtons. However, the cumulative adhesion energy greatly increases in the presence of PIP2 demonstrating that a larger number of bonds between ezrin and F-actin has formed. In contrast, the phosphorylation state, represented by phosphor-mimetic mutants of ezrin, only plays a minor role in the activation process. These results are in line with in vivo experiments demonstrating that an increase in PIP2 concentration recruits more ezrin to the apical plasma membrane of polarized cells and significantly increases the membrane tension serving as a measure of the adhesion sites between the plasma membrane and the F-actin network.