Fig. 8. Half-lives of wild-type claudin-14 and 4S mutant. Tet-off MDCK cells stably transfected with wild-type claudin-14 or the 4S mutant were induced to express the transgenes for 4 days. At day 4, doxycyline was added to repress transgene induction and cells were collected at the indicated times and processed for immunoblot analysis. The amount of starting protein was normalized to 100% so as to be able better to compare half-lifes. Open circles, wild-type claudin-14; filled circles, 4S mutant. Points are the means and ranges of duplicate samples. There was no difference in protein half-life in this experiment or in a replicate experiment performed on different clones expressing the same proteins; calculated half-lifes of both proteins were close to 6 hours.