Hirokawa N, Heuser J E
J Cell Biol. 1981 Nov;91(2 Pt 1):399-409. doi: 10.1083/jcb.91.2.399.
The cytoskeleton that supports microvilli in intestinal epithelial cells was visualized by the quick-freeze, deep-etch, rotary-replication technique (Heuser and Salpeter. 1979. J. Cell Biol. 82: 150). Before quick freezing, cells were exposed to detergents or broken open physically to clear away the granular material in their cytoplasm that would otherwise obscure the view. After such extraction, cells still displayed a characteristic organization of cytoskeletal filaments in their interiors. Platinum replicas of these cytoskeletons had sufficient resolution to allow us to identify the filament types present, and to determine their characteristic patterns of interaction. The most important new finding was that the apical "terminal web" in these cells, which supports the microvilli via their core bundles of actin filaments, does not itself contain very much actin but instead is comprised largely of narrow strands that interconnect adjacent actin bundles with one another and with the underlying base of intermediate filaments. These strands are slightly thinner than actin, do not display actin's 53A periodicity, and do not decorate with myosin subfragment S1. On the contrary, two lines of evidence suggested that these strands, could include myosin molecules. First, other investigators have shown that myosin is present in the terminal web (Mooseker et al. 1978. J. Cell Biol. 79: 444-453), yet we could find no thick filaments in this area. Second, we found that the strands were removed completely in the process of decorating the core filament bundles with the myosin subfragment S1, suggesting that they had been competitively displaced by exogenous myosin. We conclude that myosin may play a structural role in these cells, via its cross-linking distribution, in addition to whatever role it plays in microvillar motility.
通过快速冷冻、深度蚀刻、旋转复制技术（休泽尔和萨尔彼得，1979年，《细胞生物学杂志》82卷：150页）观察到了肠道上皮细胞中支撑微绒毛的细胞骨架。在快速冷冻之前，细胞先用去污剂处理或通过物理方法破碎，以清除细胞质中的颗粒物质，否则这些物质会遮挡视野。经过这样的提取后，细胞内部仍显示出细胞骨架丝的特征性组织。这些细胞骨架的铂复制品具有足够的分辨率，使我们能够识别存在的丝类型，并确定它们的特征性相互作用模式。最重要的新发现是，这些细胞中的顶端“终末网”通过肌动蛋白丝的核心束支撑微绒毛，但其本身并不含有太多肌动蛋白，而是主要由窄链组成，这些窄链将相邻的肌动蛋白束相互连接，并与下方的中间丝基部相连。这些链比肌动蛋白略细，不显示肌动蛋白的53埃周期性，也不能用肌球蛋白亚片段S1进行标记。相反，有两条证据表明这些链可能包含肌球蛋白分子。第一，其他研究人员已经表明肌球蛋白存在于终末网中（穆斯克等人，1978年，《细胞生物学杂志》79卷：444 - 453页），然而我们在这个区域没有发现粗丝。第二，我们发现在用肌球蛋白亚片段S1标记核心丝束的过程中，这些链被完全去除，这表明它们被外源性肌球蛋白竞争性取代。我们得出结论，肌球蛋白除了在微绒毛运动中发挥作用外，还可能通过其交联分布在这些细胞中发挥结构作用。
