Immunocytochemical localization of cathepsins B and H in rat liver

Light and electron microscopic localization of cathepsins B and H in rat liver was investigated by immunoenzyme and protein A-gold techniques. For light microscopy (LM), semi-thin sections of the Epon-embedded material were stained by the immunoenzyme technique after removal of epoxy resin. For electron microscopy (EM), ultra-thin sections of the Lowicryl K4M-embedded material were stained by the protein A-gold technique. By LM, reaction deposits for cathepsins B and H were present in the cytoplasmic granules of parenchymal cells and endothelial cells, and Kupffer cells. The sinus-lining cells and the parenchymal cells showed the similar staining intensity. By EM, gold particles were present exclusively in lysosomes of all the cell types cited above. The same results were obtained from quantitative analysis. In addition, Golgi complexes themselves were mostly negative but some small vesicles on the trans side of them were labeled for these proteinases. The results indicate that cathepsins B and H are present in the lysosomes of rat liver and that these enzymes seem to be transported by small vesicles from endoplasmic reticulum to lysosomes via tubuloreticular network of the trans Golgi region.

Effects of 8-bromoadenosine 3':5'-cyclic monophosphate on proteolytic enzymes, adhesiveness and lung-colonizing ability of cloned low-metastatic Lewis lung carcinoma cells

Treatment of cloned low-metastatic Lewis lung carcinoma cells (P-29) with dimethylsulfoxide or butyric acid resulted in enhancement of their lung-colonizing ability. This was accompanied with increases in cathepsin B activity, the production of plasminogen activator, and adhesiveness, mainly heterotypic adhesion (adhesion to monolayers of endothelial cells) of dimethylsulfoxide-treated cells and homotypic aggregation of butyric acid-treated cells. Treatment of P-29 cells with 8-bromoadenosine 3':5'-cyclic monophosphate (8-bromo-cyclic AMP) also resulted in increases in cathepsin B activity and the production of plasminogen activator. However, it did not enhance either heterotypic adhesion or homotypic aggregation of the cells. The lung-colonizing ability of 8-bromo-cyclic AMP-treated P-29 cells was examined after their intravenous injection into male C57BL/6 mice. It was found that these cells did not have enhanced lung-colonizing ability. These results suggest that high activities of proteolytic enzymes such as cathepsin B and plasminogen activator in tumor cells are not sufficient alone for completing the metastatic process, but that other properties of tumor cells such as adhesiveness are also necessary.

Nucleotide and predicted amino acid sequences of cloned human and mouse preprocathepsin B cDNAs

Cathepsin B is a lysosomal thiol proteinase that may have additional extralysosomal functions. To further our investigations on the structure, mode of biosynthesis, and intracellular sorting of this enzyme, we have determined the complete coding sequences for human and mouse preprocathepsin B by using cDNA clones isolated from human hepatoma and kidney phage libraries. The nucleotide sequences predict that the primary structure of preprocathepsin B contains 339 amino acids organized as follows: a 17-residue NH2-terminal prepeptide sequence followed by a 62-residue propeptide region, 254 residues in mature (single chain) cathepsin B, and a 6-residue extension at the COOH terminus. A comparison of procathepsin B sequences from three species (human, mouse, and rat) reveals that the homology between the propeptides is relatively conserved with a minimum of 68% sequence identity. In particular, two conserved sequences in the propeptide that may be functionally significant include a potential glycosylation site and the presence of a single cysteine at position 59. Comparative analysis of the three sequences also suggests that processing of procathepsin B is a multistep process, during which enzymatically active intermediate forms may be generated. The availability of the cDNA clones will facilitate the identification of possible active or inactive intermediate processive forms as well as studies on the transcriptional regulation of the cathepsin B gene.

Significance of lysosomal proteases; cathepsins B and H in maxillary mucosa and nasal polyp with non-atopic chronic inflammation

Tissue extracts from maxillary mucosa (MM) and nasal polyp (NP) with non-atopic chronic inflammation were applied to DEAE-Sepharose, and hydrolytic activity of lysosomal proteases (cathepsins B and H) was measured by the fluorometric assay. Hydrolytic activity of cathepsins B and H in MM, of which cathepsin B was a major one, was about 3.5 times as high as that in NP. Protein composition resembled in both extracts except for several apparent protein bands with high molecular weight observed in NP. These results suggest that in MM with chronic inflammation, mucosal destruction induced by excess lysosomal granuloproteases overwhelming protease inhibitors would occur, being much related to the formation of its irreversible lesion.

Monoclonal antibodies to rabbit liver cathepsin B

Three stable hybridoma cell lines (AF8, BC11, CE2) have been produced that secrete antibodies specific for cathepsin B. These have been characterized by ELISA, SDS-PAGE immunostaining, immunoprecipitation and immunofluorescent staining. CE2 immunoprecipitated native cathepsin B with retention of enzymic activity, but failed to cross-react with the alkali-denatured enzyme. BC11 bound only to the denatured form of cathepsin B and AF8 cross-reacted with both native and denatured cathepsin B. However, unlike CE2-immunoprecipitated enzyme, activity could be detected only after dissociation of the antigen-AF8 antibody complex. No cross reaction was found with any lysosomal protein including the cysteine proteinases, cathepsins H and L.