Fig. 5. Trafficking of CB-EGFP in FRTL-5 cells. Single channel fluorescence (lower panels, middle and right, and inset in D), merged (A-D) and phase contrast micrographs (lower panels, left) of FRTL-5 cells transiently expressing CB-EGFP were taken with a confocal LSM after immunolabeling with antibodies against the ER-resident protein PDI (A, red), the Golgi mannosidase II (B, red), the endogenous lysosomal cysteine protease cathepsin B (D, red) and after pulse-chase loading of lysosomes with Lyso Tracker (C, red). For reference, the inset in D shows non-transfected FRTL-5 cells after immunolabeling of cathepsin B. Yellow signals are indicative of colocalization. Arrowheads point to ER-cisternae; stars mark the positions of the Golgi and arrows indicate lysosomes. N, nuclei. Bars, 40 µm.