CLAUDINS AND OCCLUDIN : COMPARISON WITH CONNEXIN

在紧密连接（TJ）中，TJ链与相邻细胞的TJ链横向相连，形成成对的链，以消除细胞外间隙。紧密连接蛋白-1和-2，完整的膜蛋白的TJ，重组配对的TJ链转染到L成纤维细胞时。Claudins包括一个多基因家族和两个以上的不同的claudins在单细胞中共表达，提出的问题是否heteroseneous claudins形成异聚TJ链和是否claudins之间的相互作用的每对链之间的heterophilic方式。为了回答这些问题，我们将claudin-1、claudin-2和claudin-3中的两种共转染到L细胞中，并检测它们在细胞-细胞边界处的共浓度作为精细的网络。Immunoreplica电子显微镜证实，不同的claudins共同纳入个别TJ链。接下来，将单独表达claudin-1、claudin-2或claudin-3的两个L转染子共培养，并且我们发现claudin-3-链与claudin-1和claudin-2链横向缔合以形成成对链，而claudin-1链不与claudin-2链相互作用。我们的结论是，不同种类的claudins可以相互作用的TJ链内和之间，除了在某些组合。这种紧密连接蛋白的组装模式可以增加TJ链结构和功能的多样性。

In tight junctions (TJs), TJ strands are associated laterally with those of adjacent cells to form paired strands to eliminate the extracellular space. Claudin-1 and-2, integral membrane proteins of TJs, reconstitute paired TJ strands when transfected into L fibroblasts. Claudins comprise a multigene family and more than two distinct claudins are co-exrressed in single cells, raising the questions of whether heteroseneous claudins form heteromeric TJ strands and whether claudins interact between each of the paired strands in a heterophilic manner. To answer these questions, we co-transfected two of claudin-1, -2 and -3 into L cells, and detected their coconcentration at cell-cell borders as elaborate networks. Immunoreplica electron microscopy confirmed that distinct claudins were co-incorporated into individual TJ strands. Next, two L transfectants singly expressing claudin-1, -2 or -3 were cocultured, and we found that claudin-3-strands laterally associated with claudin-1 and claudin-2 stranas to form paired strands, whereas claudin-1 strands did not interact with claudin-2 strands. We concluded that distinct species of claudins can interact within and between TJ strands except in some combinations. This mode of assembly of claudins could increase the diversity of the structure and functions of TJ strands.