Figure 5.

Effect of GM-CSF on claudin-5 ubiquitination. (a) MG132 inhibits the GM-CSF-induced decrease in claudin-5 protein expression. HBMEC monolayers were incubated with MG132 and GM-CSF for 6, 12, or 24 h. (b) GM-CSF increases the claudin-5 ubiquitination level. A myc-taged-claudin-5 plasmid was transfected into HEK293T cells. GM-CSF or GM-CSF/MG132 was added to the supernatant 24 h after transfection. Immunoprecipitation with claudin-5 antibody was performed, and ubiquitin and myc expression were detected via western blotting (arrows). (c) The claudin-5 polyubiquitination levels in myc-claudin-5 and flag-ubiquitin co-transfected HEK293T cells (arrows).