Fig. 5. Localization of wild-type claudin-14 and 4S mutant. Wild-type claudin-14 colocalizes with ZO-1 to the tight junction, whereas the palmitoylation-deficient mutant 4S is found both at the tight junction and in large intracellular aggregates. Stable cell lines were induced or not for 4 days and processed for immunofluorescent analysis of tight-junction proteins. Neither wild-type nor mutant claudin-14 is detectable in uninduced Tet-off MDCK cells (WT and 4S, uninduced); ZO-1 immunofluorescence (left) is concentrated at the apical junctional complex, whereas endogenous claudin-4 (right) is found both at the cell membrane and in some intracellular puncta. Wild-type claudin-14 localizes mostly to tight junctions with ZO-1 (WT, induced) but does mediate some intracellular accumulation of both ZO-1 (left) and claudin-4 (right). The 4S mutant is found both at the tight junction and in large intracellular aggregates (4S, induced), where it colocalizes with ZO-1 and claudin-4. Scale bar, 10 µm.