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

(1)紧密连接（TJ）及其粘附分子claudins负责简单上皮的屏障功能，但TJ在哺乳动物复层上皮（包括表皮）的屏障功能中并不重要。在这项研究中，我们产生了claudin-1缺陷小鼠，发现这些动物在出生后一天内死亡，皮肤起皱。脱水测定以及经表皮水分损失测量显示，在这些小鼠中，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用抗闭合蛋白mAb（一种TJ特异性标记物）仔细检查，鉴定了颗粒层中的连续TJ，其中紧密连接蛋白-1和-4被浓缩。在claudin-1缺陷的小鼠中，claudin-1似乎只是从这些TJ中去除， 关于我们 din（以及claudin-4）阳性TJ。有趣的是，在野生型表皮中，这些闭合蛋白阳性TJ有效地防止皮下注射的示踪剂（10600道尔顿）向皮肤表面扩散，而在闭合蛋白-1缺陷型表皮中，示踪剂似乎穿过这些TJ。这些发现提供了第一个证据，即连续的基于密蛋白的TJ发生在表皮中，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）是线性聚合物，是质膜内典型的蛋白质聚合物，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，并且当在小鼠L成纤维细胞中外源表达时，它们显示出在细胞-细胞边界处重建TJ链。在这项研究中，我们表明，GFP（绿色荧光蛋白）融合蛋白与claudin-1也可以重建TJ链在L成纤维细胞，使我们能够直接观察活细胞中的个别TJ链。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