Helical arrangement of filaments in microvillar actin bundles
Helical arrangement of filaments in microvillar actin bundles
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DOI：
10.1016/j.jsb.2011.10.012
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发表时间：
2012-02-01
影响因子：
3
通讯作者：
Nakamura, Kei-ichiro
中科院分区：
文献类型：
--
作者：
Ohta, Keisuke;Higashi, Ryuhei;Nakamura, Kei-ichiro
用电子断层扫描（ET）技术对在体大鼠小肠上皮细胞微绒毛束中的肌动蛋白丝阵列进行了重新评价。高压冷冻固定和树脂包埋刷状缘的半薄横截面（300 nm厚）的常规电子显微镜观察显示微绒毛中心的旋转图案而不是六边形排列的点，这强烈表明束由非平行的细丝阵列组成。一种深度补偿方法的ET开发估计的肌动蛋白束的实际结构。在图像采集过程中通过光束照射的样本收缩率估计为63%，我们在重建中恢复了原始厚度。深度补偿断层图像显示了束内的单个肌动蛋白丝，并且它表明肌动蛋白丝并不完全平行于彼此：相反，它们以近似120度/μ m的节距顺时针盘绕。此外，肌动蛋白丝的晶格偶尔重新排列在束内。由于微绒毛束与膜机械地相互作用，并且被认为被膜的微弱张力压缩，因此我们使用洗涤剂去除包裹膜以消除机械相互作用。裸露的纤维束不再显示出旋转的图案，这表明纤维束已经释放了它的盘绕特性。这些研究结果表明，束具有刚性，但弹性的性质和动态的转变，在其结构中所造成的膜和束之间的机械相互作用的变化。(C)2011 Elsevier Inc. All rights reserved.
Actin filament arrays in in vivo microvillar bundles of rat intestinal enterocyte were re-evaluated using electron tomography (ET). Conventional electron microscope observation of semi-thin cross sections (300 nm thick) of high-pressure freeze fixed and resin embedded brush border has shown a whirling pattern in the center of the microvilli instead of hexagonally arranged dots, which strongly suggests that the bundle consists of a non-parallel array of filaments. A depth compensation method for the ET was developed to estimate the actual structure of the actin bundle. Specimen shrinkage by beam irradiation during image acquisition was estimated to be 63%, and we restored the original thickness in the reconstruction. The depth compensated tomogram displayed the individual actin filaments within the bundles and it indicated that the actin filaments do not lie exactly parallel to each other: instead, they are twisted in a clockwise coil with a pitch of similar to 120 degrees/mu m. Furthermore, the lattice of actin filaments was occasionally re-arranged within the bundle. As the microvillar bundle mechanically interacts with the membrane and is thought to be compressed by the membrane's faint tensile force, we removed the shrouding membrane using detergents to eliminate the mechanical interaction. The bared bundles no longer showed the whirling pattern, suggesting that the bundle had released its coiled property. These findings indicate that the bundle has not rigid but elastic properties and a dynamic transformation in its structure caused by a change in the mechanical interaction between the membrane and the bundle. (C) 2011 Elsevier Inc. All rights reserved.