The terminal web. A reevaluation of its structure and function.
The terminal web. A reevaluation of its structure and function.
复制标题
终端网。重新评估其结构和功能。
DOI：
10.1083/jcb.81.1.67
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发表时间：
1979-04
影响因子：
7.8
通讯作者：
Staehelin, L A
中科院分区：
文献类型：
--
作者：
Hull, B E;Staehelin, L A
小肠和大肠上皮细胞的顶端细胞质已通过冷冻蚀刻技术以及切片材料的常规和高压电子显微镜进行了检查，以便更好地了解末端网络区域的精细结构组织。在小肠中，末端网表现出明显的分层，这是由不同组的细丝与连接复合体的三个成员的结合引起的。该网络的各个细丝与紧密连接的密封元件、核心微丝束的表面以及微绒毛间质膜密切相关。末端网的这个区域是顶端区。粘附区表现为一条由两种不同直径的交织细丝组成的带，在中间连接处延伸穿过细胞质。在末端网的该区域内，单独的60-70A肌动蛋白样丝从核心微丝束分离以彼此相互作用并与来自粘附小带的类似直径的丝相互作用。 100 A张力丝也有助于粘附区，可能稳定肌动蛋白样丝的方向。粘附区下方的基底区由紧密交织的张力丝束组成，这些张力丝固定在点桥粒上并相互连接。在大肠内，细胞质微丝形成较松散且分层不太清晰的网络，但仍保留与小肠中相同的基本组织。跨膜连接体似乎起源于点桥粒的细胞质斑块内，穿过质膜，并在细胞间隙中以交错结构相遇；因此，这些接头可以介导相邻细胞的张力丝束的细胞骨架网络之间的实际机械耦合。这种细胞质丝和细胞间连接的集成系统赋予顶端细胞质上皮正常功能所需的灵活性和稳定性。
The apical cytoplasm of epithelial cells of the small and large intestines has been examined by freeze-etch techniques as well as conventional and high voltage electron microscopy of sectioned material to gain a better understanding of the fine structural organization of the terminal web region. In the small intestine the terminal web exhibits a distinct stratification caused by the association of different sets of filaments with the three members of the junctional complex. Individual filaments of this network are closely associated with the sealing elements of the tight junctions, the surface of the core microfilament bundles, and the intermicrovillar plasma membrane. This region of the terminal web is the apical zone. The adherens zone appears as a band of interwoven filaments of two different diameters extending across the cytoplasm at the level of the intermediate junction. Within this region of the terminal web, individual 60-70 A actin-like filaments separate from the bundles of core microfilaments to interact with one another and with filaments of similar diameter from the zonula adherens. 100 A tonofilaments also contribute to the adherens zone, presumably stabilizing the orientation of the actin-like filaments. The basal zone which underlies the adherens zone consists of closely interwoven bundles of tonofilaments that are anchored to and interconnect the spot desmosomes. Within the large intestine the cytoplasmic microfilaments form a looser and less clearly stratified network which nevertheless retains the same basic organization found in the small intestine. Transmembrane linkers appear to originate within the cytoplasmic plaques of the spot desmosomes, pass through the plasma membranes, and meet in a staggered configuration in the intercellular space; these linkers may thus mediate the actual mechanical coupling between the cytoskeletal networks of tonofilament bundles of adjacent cells. This integrated system of cytoplasmic filaments and intercellular junctions endows the apical cytoplasm with both the flexibility and the stability necessary for the normal functioning of the epithelium.