National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Ann N Y Acad Sci. 2012 Jun;1257:103-7. doi: 10.1111/j.1749-6632.2012.06535.x.
Treatment of epithelial and endothelial cells with proinflammatory cytokines can stimulate tight junction protein endocytosis, with associated loss of physiologic barrier function. In some instances, the endocytic scaffolding protein, caveolin-1, has been implicated in the cytokine-dependent retrieval of the tight junction proteins occludin and claudins. How caveolin-1 interacts with these proteins, however, remains undefined. Using co-immunoprecipitation assays, we found that caveolin-1 separately interacts with claudin-2 and occludin, but not with ZO-1, ZO-2, or claudin-4. Further, we found that the interactions of caveolin-1 with claudin-2 and occludin were not disrupted by cholesterol removal, suggesting that they were not dependent on co-localization to cholesterol-rich lipid rafts. Co-immunoprecipitation of caveolin-1 with chimeras between claudin-2 and -4 indicated that the C-terminal cytoplasmic domain of claudin-2 is required for association with caveolin-1; similar analysis showed that the ZO-1 binding region of occludin is not required for its interaction with caveolin-1. The finding that caveolin-1 interacts with claudin-2 and occludin, but not with claudin-4 or ZO-1, suggests a potential mechanism for selective retrieval of tight junction components.
用促炎细胞因子处理上皮细胞和内皮细胞可以刺激紧密连接蛋白内吞，从而导致生理屏障功能丧失。在某些情况下，网格蛋白相关蛋白-1（caveolin-1）已被牵连到细胞因子依赖的紧密连接蛋白闭合蛋白和封闭蛋白的回收中。然而，caveolin-1 如何与这些蛋白相互作用仍未确定。通过共免疫沉淀实验，我们发现 caveolin-1 分别与 claudin-2 和 occludin 相互作用，但与 ZO-1、ZO-2 或 claudin-4 不相互作用。此外，我们发现 caveolin-1 与 claudin-2 和 occludin 的相互作用不受胆固醇去除的干扰，这表明它们不依赖于与富含胆固醇的脂筏的共定位。caveolin-1 与 claudin-2 和 -4 嵌合体的共免疫沉淀表明，claudin-2 的 C 端细胞质结构域是与 caveolin-1 结合所必需的；类似的分析表明，occludin 的 ZO-1 结合区不是其与 caveolin-1 相互作用所必需的。caveolin-1 与 claudin-2 和 occludin 相互作用，而与 claudin-4 或 ZO-1 不相互作用的发现，为选择性回收紧密连接成分提供了一种潜在的机制。
