Langbein Lutz, Grund Christine, Kuhn Caecilia, Praetzel Silke, Kartenbeck Jürgen, Brandner Johanna M, Moll Ingrid, Franke Werner W
Division of Cell Biology, German Cancer Research Center, Heidelberg.
Eur J Cell Biol. 2002 Aug;81(8):419-35. doi: 10.1078/0171-9335-00270.
The occurrence of extended tight junction (TJ) structures, including zonulae occludentes (ZO), and the spatial arrangement of TJ proteins in stratified mammalian epithelia has long been controversially discussed. Therefore, we have systematically examined the localization of TJ proteins in diverse stratified epithelial tissues (e.g., epidermis, heel pad, snout, gingiva, tongue, esophagus, exocervix, vagina, urothelium, cornea) of various species (human, bovine, rodents) as well as in human cell culture lines derived from stratified epithelia, by electron microscopy as well as by immunocytochemistry at both the light and the electron microscopic level, using antibodies to TJ proteins such as occludin, claudins 1 and 4, protein ZO-1, cingulin and symplekin. We have found an unexpected diversity of TJ-related structures of which only those showing colocalization with the most restricted transmembrane TJ marker protein, occludin, are presented here. While in epidermis and urothelium occludin is restricted to the uppermost living cell layer, TJ-related junctions are abundant in the upper third or even in the majority of the suprabasal cell layers in other stratified epithelia. Interfollicular epidermis contains, in the stratum granulosum, extended, probably continuous ZO-like structures which can also be traced at least through the Henle cell layer of hair follicles. Similar apical ZO-like structures have been seen in the upper living cell layers of all other stratified epithelia and cell cultures examined, but in most of them we have noticed, in addition, junctional regions showing relatively broad, ribbon-like membrane contacts which in cross-section often appear pentalaminar, with an electron-dense middle lamella ("lamellated TJs", coniunctiones laminosae). In suprabasal layers of several stratified epithelia we have further observed TJ protein-containing junctions of variable sizes which are characterized by a 10-30-nm dense lamina interposed between the two membranes ("sandwich junctions"; iuncturae structae). Moreover, we have often observed variously sized regions in which the intermembrane distance is rather regularly bridged by short rod-like elements ("cross-bridged cell walls"; parietes transtillati), often in close vicinity of TJ-related structures or desmosomes. The significance of these structures and their possible biological importance are discussed.
包括紧密连接小带（ZO）在内的扩展紧密连接（TJ）结构在分层哺乳动物上皮中的出现以及TJ蛋白的空间排列长期以来一直存在争议。因此，我们通过电子显微镜以及光镜和电镜水平的免疫细胞化学方法，使用针对TJ蛋白（如闭合蛋白、紧密连接蛋白1和4、ZO-1蛋白、cingulin和symplekin）的抗体，系统地研究了TJ蛋白在各种物种（人类、牛、啮齿动物）的不同分层上皮组织（如表皮、足跟垫、口鼻部、牙龈、舌头、食道、子宫颈外口、阴道、尿路上皮、角膜）以及源自分层上皮的人类细胞系中的定位。我们发现了与TJ相关结构的意外多样性，这里仅展示那些与最具限制性的跨膜TJ标记蛋白闭合蛋白共定位的结构。在表皮和尿路上皮中，闭合蛋白局限于最上层的活细胞层，而在其他分层上皮中，与TJ相关的连接在上三分之一甚至大部分基底上层细胞层中丰富存在。毛囊间表皮在颗粒层中含有延伸的、可能连续的ZO样结构，这些结构至少可以通过毛囊的亨勒细胞层追踪到。在所有其他检查的分层上皮和细胞培养物的上层活细胞层中都观察到了类似的顶端ZO样结构，但在大多数情况下，我们还注意到连接区域呈现相对宽阔的、带状的膜接触，在横截面中通常呈五板层状，中间有电子致密的中层（“层状TJ”，lamellated TJs）。在几种分层上皮的基底上层中，我们进一步观察到大小可变的含TJ蛋白的连接，其特征是在两个膜之间插入一个10 - 30纳米厚的致密层（“三明治连接”；iuncturae structae）。此外，我们经常观察到大小各异的区域，其中膜间距离通过短杆状元件相当规则地桥接（“交叉桥接细胞壁”；parietes transtillati），这些区域通常靠近与TJ相关的结构或桥粒。讨论了这些结构的意义及其可能的生物学重要性。
