Format

Send to

Choose Destination
Arthritis Rheum. 1984 May;27(5):509-15.

Extracellular presence of the lysosomal proteinase cathepsin B in rheumatoid synovium and its activity at neutral pH.

Abstract

The presence of the lysosomal proteinases cathepsin B and cathepsin D at extracellular sites in rheumatoid synovium was demonstrated using the antibody capture technique. Unlike cathepsin D, the cysteine proteinase cathepsin B was commonly detected only at the edges of the synovial explants. Radioimmunoassay and enzyme activity assay of these proteinases demonstrated that both were released from rheumatoid synovial cells in comparable amounts. Since lysosomal cathepsin B is unstable and denatured at physiologic pH and the antibody used only recognizes inactivated enzyme, we believe the selective detection of cathepsin B at the edge of the synovium may be due to the proteinase maintaining a native conformation within the explant, where the pH may be low enough to permit this. By use of a fluorescent substrate in a sensitive, continuous enzyme assay, cathepsin B was shown to express significant activity at neutral and alkaline pH before being inactivated. This and earlier work from this laboratory indicate that cathepsin B secreted by rheumatoid synovial cells may possess extracellular activity in vivo and be involved in the degradation of connective tissue macromolecules.

PMID:
6721883
[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Wiley
Loading ...
Support Center