The E3 ubiquitin ligase LNX1p80 promotes the removal of claudins from tight junctions in MDCK cells.
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.
Takahashi
Senye
S
Department of Cell Biology, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan.
Iwamoto
Noriko
N
Sasaki
Hiroyuki
H
Ohashi
Masato
M
Oda
Yukako
Y
Tsukita
Shoichiro
S
Furuse
Mikio
M
D000818:Animals; D002460:Cell Line; D062445:Claudin-1; D004285:Dogs; D015536:Down-Regulation; D004705:Endocytosis; D004847:Epithelial Cells / Q000166:cytology / Q000201:enzymology* / Q000648:ultrastructure; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D019108:Tight Junctions / Q000378:metabolism* / Q000648:ultrastructure; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000378:metabolism*; D054875:Ubiquitination
C568108:CLDN1 protein, human; D062445:Claudin-1; C568113:Cldn1 protein, mouse; D008565:Membrane Proteins; C111865:Lnx1 protein, mouse; D044767:Ubiquitin-Protein Ligases