Fig. 3. Localization of syntaxins 2 and 4 in RPE-J cells. Polarized monolayers of RPE-J cells were cultured on Transwell filters, and syntaxin localizations were analyzed by double-label confocal immunofluorescence microscopy. Panels A-C and D-F, respectively, represent the same fields of xy confocal sections. Small panels underneath are xz confocal sections. A shows immunostaining for syntaxin 2, B for the tight junction protein ZO-1 and C the color-merged image. D shows immunostaining for syntaxin 4, E for the basolateral plasma membrane protein EMMPRIN and F the color-merged image. Note that syntaxin 2 and ZO-1 colocalize throughout most of the areas of cell-cell contact. However, the localization of ZO-1 at the tight junctions is more uniform. There are areas of intense syntaxin 2 staining, whereas others are nearly devoid of it. Syntaxin 4 and EMMPRIN both colocalize in a relatively uniform fashion at the areas of cell-cell contact. Bars, 5 µm.