Shivers R R, Bowman P D, Martin K
Tissue Cell. 1985;17(3):417-40. doi: 10.1016/0040-8166(85)90059-x.
The structure and function of intercellular tight (occluding) junctions, which constitute the anatomical basis for highly regulated interfaces between tissue compartments such as the blood-testis and blood-brain barriers, are well known. Details of the synthesis and assembly of tight junctions, however, have been difficult to determine primarily because no model for study of these processes has been recognized. Primary cultures of brain capillary endothelial cells are proposed as a model in which events of the synthesis and assembly of tight junctions can be examined by monitoring morphological features of each step in freeze-fracture replicas of the endothelial cell plasma membrane. Examination of replicas of non-confluent monolayers of endothelial cells reveals the following intramembrane structures proposed as 'markers' for the sequential events of synthesis and assembly of zonulae occludentes: development of surface contours consisting of elongate terraces and furrows (valleys) orientated parallel to the axis of cytoplasmic extensions of spreading endothelial cells, appearance of small circular PF face depressions (or volcano-like protrusions on the EF face) that represent cytoplasmic vesicle-plasma membrane fusion sites, which are positioned in linear arrays along the contour furrows, appearance of 13-15 nm intramembrane particles at the perimeter of the vesicle fusion sites, and alignment of these intramembrane particles into the long, parallel, anastomosed strands characteristic of mature tight junctions. These structural features of brain endothelial cells in monolayer culture constitute the morphological expression of: reshaping the cell surface to align future junction-containing regions with those of adjacent cells, delivery and insertion of newly synthesized junctional intramembrane particles into regions of the plasma membrane where tight junctions will form, and aggregation and alignment of tight junction intramembrane particles into the complex interconnected strands of mature zonulae occludentes. The distribution of filipin-sterol complex-free regions on the PF intramembrane fracture face of junction-forming endothelial plasmalemmae corresponds precisely to the furrows, aligned vesicle fusion sites and anastomosed strands of tight junctional elements.(ABSTRACT TRUNCATED AT 400 WORDS)
细胞间紧密（封闭）连接的结构与功能是众所周知的，它构成了组织隔室（如血睾屏障和血脑屏障）之间高度调节界面的解剖学基础。然而，紧密连接的合成与组装细节一直难以确定，主要是因为尚未找到用于研究这些过程的模型。脑毛细血管内皮细胞的原代培养被提议作为一种模型，在其中可以通过监测内皮细胞质膜冷冻断裂复制品中每个步骤的形态特征来研究紧密连接的合成与组装事件。对非汇合内皮细胞单层复制品的检查揭示了以下膜内结构，这些结构被提议作为紧密连接合成与组装顺序事件的“标记”：由平行于铺展内皮细胞细胞质延伸轴排列的细长平台和沟槽（谷）组成的表面轮廓的形成；代表细胞质囊泡 - 质膜融合位点的小圆形PF面凹陷（或EF面上类似火山的突起）的出现，这些位点沿着轮廓沟槽呈线性排列；在囊泡融合位点周边出现13 - 15纳米的膜内颗粒；以及这些膜内颗粒排列成成熟紧密连接特有的长、平行、吻合的链状结构。单层培养的脑内皮细胞的这些结构特征构成了以下形态学表现：重塑细胞表面，使未来含连接区域与相邻细胞的区域对齐；将新合成的连接膜内颗粒递送至并插入质膜中形成紧密连接的区域；以及将紧密连接膜内颗粒聚集并排列成成熟紧密连接的复杂相互连接的链状结构。在形成连接的内皮细胞质膜的PF膜内断裂面上，无菲啶 - 甾醇复合物区域的分布与紧密连接元件的沟槽、对齐的囊泡融合位点和吻合的链状结构精确对应。（摘要截短于400字）
