Fig. 3. Heterologous expression of CB-EGFP and its lysosomal localization in CHO cells. Single channel fluorescence (lower panels, middle and right), merged (A,B) and phase contrast micrographs (lower panels, left) of CHO cells transiently expressing CB-EGFP (green in A,B) were taken with a confocal LSM after immunolabeling with antibodies specific for heterologously expressed rat cathepsin B (A, red) and after pulse-chase loading of lysosomes with Lyso Tracker (B, red). Yellow signals are indicative of colocalization. N, nuclei. Bars, 20 µm.