Fig. 5

USP40 stabilizes Claudin1 by promoting its de-ubiquitination. A Stable USP40 knockdown MHCC97H cells and negative control (NC) cells were treated by MG132 (10 μM) for 8 h, and then Claudin1 expression was tested by western blotting. B CHX assay was conducted to detect the half-life of Claudin1 in USP40 knockdown and NC cells. Each group was treated by CHX (100 µg/mL) for a specified time. Next, proteins were collected and then Claudin1 expression was tested by western blotting. C MHCC97H cells stably overexpressed USP40 and NC cells were treated by MG132 (10 μM) for 8 h, and then Claudin1 expression was tested by western blotting. D CHX assay was conducted to detect the half-life of Claudin1 in USP40 overexpressed and NC cells. E–F Quantitative evaluation of the half-life of the Claudin1 protein. G Effect of USP40 silencing on Claudin1 ubiquitination. Lysates from MHCC97H cells were immunoprecipitated using Claudin1 antibody and Claudin1 polyubiquitination was examined using western blotting. H Effect of USP40 overexpression on Claudin1 ubiquitination in MHCC97H cells. Data were displayed with typical pictures of three independent experiments. *P < 0.05