Figure 7

Expression of cathepsin B-eGFP and cathepsin B-C29A-eGFP chimeras in thyroid carcinoma cells. Single channel fluorescence (A-F) and corresponding phase contrast micrographs (insets) taken with the confocal laser scanning microscope of KTC-1 (A and D), HTh7 (B and E) and HTh74 cells (C and F) after transfection with plasmids coding for eGFP-tagged active (A-C) and inactive cathepsin B (D-F) as indicated. The localization of the eGFP-tagged cathepsin B was vesicular in KTC-1 and HTh74 cells (A and C, arrows), whereas it was retained in the Golgi of HTh7 cells (B). In contrast, the eGFP-tagged active site mutant counter-part of cathepin B was localized within reticular structures, the Golgi apparatus and a few vesicles (arrows) of KTC-1 (D) and HTh7 cells (E), while it was mainly localized to vesicles of HTh74 cells (F), indicating that the inactive mutant form of cathepsin B is transport-competent in principle. N denotes nuclei. Scale bars represent 10 µm.