The E3 ubiquitin ligase LNX1p80 promotes the removal of claudins from tight junctions in MDCK cells
The E3 ubiquitin ligase LNX1p80 promotes the removal of claudins from tight junctions in MDCK cells
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DOI：
10.1242/jcs.040055
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发表时间：
2009-04-01
影响因子：
4
通讯作者：
Furuse, Mikio
中科院分区：
文献类型：
--
作者：
Takahashi, Senye;Iwamoto, Noriko;Furuse, Mikio
即使上皮细胞在细胞片层内分裂和移动，紧密连接（TJ）的结构连续性也始终保持不变。该过程与通过协调内化和产生基于紧密连接蛋白的TJ链的TJ的动态重塑相关，但是TJ的调节周转背后的分子机制在很大程度上仍然未知。在这项研究中，我们确定了Numb蛋白X1（LNX 1 p80）的E3泛素连接酶配体的p80亚型作为与claudin-1结合的蛋白质。有趣的是，当LNX 1 p80在MDCK细胞中过表达时，TJ中的密封蛋白浓度显著降低，并且不仅TJ链的数量减少，而且去污剂不溶性密封蛋白的量也减少。我们还发现LNX 1 p80促进了claudins的多聚泛素化。这种泛素化依赖于其环指结构域，并且不受泛素的Lys 48介导，其用于蛋白酶体的蛋白质降解。此外，LNX 1 p80通常与含有晚期内体和溶酶体标记物的囊泡结构中的密封蛋白共定位。这些发现表明LNX 1 p80参与了claudins的泛素化、内吞和溶酶体降解，并且TJ的周转受泛素化的调节。
The structural continuity of tight junctions (TJs) is consistently maintained even when epithelial cells divide and move within the cellular sheet. This process is associated with dynamic remodeling of TJs by coordinated internalization and generation of claudin- based TJ strands, but the molecular mechanism behind the regulated turnover of TJs remains largely unknown. In this study, we identified the p80 isoform of the E3 ubiquitin ligase ligand of Numb-protein X1 (LNX1p80) as a protein binding to claudin-1. Interestingly, the concentration of claudins in TJs was remarkably reduced when LNX1p80 was overexpressed in MDCK cells, and there was a reduction not only in the number of TJ strands but also in the amount of detergent-insoluble claudins. We also found that LNX1p80 promoted polyubiquitylation of claudins. This ubiquitylation is dependent on its RING-finger domain and is not mediated by Lys48 of ubiquitin, which is used for protein degradation by the proteasome. Furthermore, LNX1p80 was often colocalized with claudins in vesicular structures containing markers for late endosomes and lysosomes. These findings suggest that LNX1p80 is involved in the ubiquitylation, endocytosis and lysosomal degradation of claudins, and that the turnover of TJs is regulated by ubiquitylation.