The claudin family : Its involvement in interecellular sealing and epithelial polarity

(1)紧密连接(TJ)及其黏附分子Claudins负责简单上皮的屏障功能，但TJ尚未被认为在哺乳动物包括表皮在内的复层上皮的屏障功能中起重要作用。在这项研究中，我们产生了claudin-1缺陷的小鼠，并发现这些动物在出生后一天内死亡，皮肤出现皱纹。脱水试验和经皮失水测量表明，这些小鼠的表皮屏障受到严重影响，尽管角质形成细胞的分层组织似乎是正常的。这些意想不到的发现促使我们重新检查野生型小鼠表皮中的TJ。通过免疫荧光显微镜和抗闭塞蛋白单抗(一种Tj特异性标记)的近距离观察，发现颗粒层中有连续的TJ，其中集中了claudin-1和-4。在Claudin-1缺陷小鼠中，Claudin-1似乎只是从这些TJ中移除，留下了occlu…更多的DIN(和claudin-4)阳性的TJ。有趣的是，在野生型表皮中，这些阻滞素阳性的TJ有效地阻止了皮下注射的示踪剂(~600道尔顿)向皮肤表面的扩散，而在Claudin-1缺乏的表皮中，示踪剂似乎穿过这些TJ。这些发现首次证明，连续的基于Claudin的TJ存在于表皮中，并且这些TJ对于哺乳动物皮肤的屏障功能是至关重要的。(2)紧密连接(TJ)支架是线形聚合物，典型的质膜内的蛋白质聚合物，其物理化学性质仍然难以捉摸。最近，Claudins被确定为TJ链的主要成分，并在小鼠L成纤维细胞中外源表达时，在细胞-细胞边界重建TJ链。在本研究中，我们发现绿色荧光蛋白与Claudin-1的融合蛋白也可以在L成纤维细胞中重建TJ链，使我们能够直接在活细胞中观察到单个TJ链。较少

(1) The tight junction (TJ) and its adhesion molecules, claudins, are responsible for the barrier function of simple epithelia, but TJs have not been thought to play an important role in the barrier function of mammalian stratified epithelia including the epidermis. In this study, we generated claudin-1-deficient mice and found that the animals died within one day of birth with wrinkled skin. Dehydration assay as well as transepidermal water loss measurements revealed that in these mice the epidermal barrier was severely affected, although the layered organization of keratinocytes appeared to be normal. These unexpected findings prompted us to re-examine TJs in the epidermis of wild-type mice. Close inspection by immunofluorescence microscopy with an anti-occludin mAb, a Tjspecific marker, identified continuous TJs in the stratum granulosum, where claudin-1 and -4 were concentrated. In claudin-1-deficient mice, claudin-1 appeared to have simply been removed from these TJs leaving occlu … More din(and also claudin-4)-positive TJs. Interestingly, in the wild-type epidermis, these occludin-positive TJs efficiently prevented the diffusion of subcutaneously-injected tracer (〜600 dalton) toward the skin surface, whereas in the claudin-1-deficient epidermis, the tracer appeared to pass through these TJs. These findings provide the first evidence that continuous claudin-based TJs occur in the epidermis, and that these TJs are crusial for the barrier function of the mammalian skin.(2) The tight junction (TJ) stand is linear polymer, typical of proteinaceous polymers within plasma membranes, the physicochemical nature of which remains elusive. Recently, claudins were identified as major constituents of TJ strands, and they were shown to reconstitute TJ strands at cell-cell borders when exogenously expressed in mouse L fibroblasts. In this study, we show that the GFP (green fluorescent protein) fusion protein with claudin-1 can also reconstitute TJ strands in L fibroblasts, allowing us to directly observe individual TJ strands in live cells. Less