Klapholz Benjamin, Herbert Samantha L, Wellmann Jutta, Johnson Robert, Parsons Maddy, Brown Nicholas H
The Gurdon Institute and Department of Physiology, Development and Neuroscience, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK.
Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK.
Curr Biol. 2015 Mar 30;25(7):847-57. doi: 10.1016/j.cub.2015.01.043. Epub 2015 Mar 5.
Cell-matrix adhesion is essential for building animals, promoting tissue cohesion, and enabling cells to migrate and resist mechanical force. Talin is an intracellular protein that is critical for linking integrin extracellular-matrix receptors to the actin cytoskeleton. A key question raised by structure-function studies is whether talin, which is critical for all integrin-mediated adhesion, acts in the same way in every context. We show that distinct combinations of talin domains are required for each of three different integrin functions during Drosophila development. The partial function of some mutant talins requires vinculin, indicating that recruitment of vinculin allows talin to duplicate its own activities. The different requirements are best explained by alternative mechanisms of talin function, with talin using one or both of its integrin-binding sites. We confirmed these alternatives by showing that the proximity between the second integrin-binding site and integrins differs, suggesting that talin adopts different orientations relative to integrins. Finally, we show that vinculin and actomyosin activity help change talin's orientation. These findings demonstrate that the mechanism of talin function differs in each developmental context examined. The different arrangements of the talin molecule relative to integrins suggest that talin is able to sense different force vectors, either parallel or perpendicular to the membrane. This provides a paradigm for proteins whose apparent uniform function is in fact achieved by a variety of distinct mechanisms involving different molecular architectures.
细胞与基质的黏附对于构建动物体、促进组织黏附以及使细胞能够迁移和抵抗机械力至关重要。踝蛋白是一种细胞内蛋白质，对于将整合素细胞外基质受体与肌动蛋白细胞骨架连接起来至关重要。结构-功能研究提出的一个关键问题是，对于所有整合素介导的黏附都至关重要的踝蛋白，在每种情况下是否都以相同的方式发挥作用。我们表明，在果蝇发育过程中，三种不同的整合素功能各自需要不同组合的踝蛋白结构域。一些突变踝蛋白的部分功能需要纽蛋白，这表明纽蛋白的募集使踝蛋白能够复制其自身的活性。不同的需求最好用踝蛋白功能的替代机制来解释，即踝蛋白使用其一个或两个整合素结合位点。我们通过表明第二个整合素结合位点与整合素之间的距离不同，证实了这些替代机制，这表明踝蛋白相对于整合素采取了不同的取向。最后，我们表明纽蛋白和肌动球蛋白活性有助于改变踝蛋白的取向。这些发现表明，在所研究的每个发育背景下，踝蛋白的功能机制都不同。踝蛋白分子相对于整合素的不同排列表明，踝蛋白能够感知平行或垂直于膜的不同力向量。这为一类蛋白质提供了一个范例，这类蛋白质表面上统一的功能实际上是通过涉及不同分子结构的多种不同机制实现的。
