Cc. Calkins et al., DIFFERENTIAL LOCALIZATION OF CYSTEINE PROTEASE INHIBITORS AND A TARGET CYSTEINE PROTEASE, CATHEPSIN-B, BY IMMUNO-CONFOCAL MICROSCOPY, The Journal of histochemistry and cytochemistry, 46(6), 1998, pp. 745-751
The cystatin superfamily of cysteine protease inhibitors and target cy
steine proteases such as cathepsin B have been implicated in malignant
progression. The respective cellular/extracellular localization of cy
statins and cysteine proteases in tumors may be critical in regulating
activity of the enzymes. Confocal microscopy has enabled us to demons
trate the differential localization of cystatins and cathepsin B in an
embryonic liver cell line and an invasive hepatoma cell line. In both
, stefins A and B were distributed diffusely throughout the cytoplasm,
whereas cystatin C was distributed in juxtanuclear vesicles. Stefin A
and cystatin C, but not stefin B, were present on the cell surface. C
ystatin C was found on the top surfaces of both cell lines, whereas st
efin A was found only on the top surface of the embryonic liver cells.
Cathepsin B staining was concentrated in perinuclear vesicles in the
embryonic liver cells. In the hepatoma cells, staining for cathepsin B
was also present in vesicles adjacent to the cell membrane and on loc
alized regions of the bottom surface, Such a disparate distribution of
cathepsin B and its endogenous inhibitors may facilitate proteolysis
by the hepatoma cells and thereby contribute to their invasive phenoty
pe.