Up-regulation, Enhanced Maturation, and Secretion of Cathepsin E in Mouse Macrophages Treated with Interferon-γ or Lipopolysaccharide

Cathepsin E is an intracellular aspartic proteinase that is predominantly localized in the endosomal compartments of antigen presenting cells including macrophages. Here, we have investigated the expression of cathepsin E in mouse macrophages treated with interferon (IFN)-γ, lipopolysaccharide (LPS), interleukin (IL)-10, and IL-4. The mRNA levels of cathepsin E in macrophages stimulated with IFN-γ and LPS were increased, but conversely, that with IL-10 was decreased. However, upon stimulation with IFN-γ or LPS, the activity levels of cathepsin E in the activated cells were markedly decreased, but those in the culture media were increased. Immunoblot analysis revealed that procathepsin E in the cells was largely converted to the mature form in the cells upon stimulation with IFN-γ. In addition, the extracellular enzyme was reacted with antibodies to mature cathepsin E but not with antibodies for procathepsin E. By contrast, when macrophages were treated with IL-4, cathepsin E production was significantly decreased in both the cell and the medium. These results indicate that, upon stimulation with IFN-γ and LPS, cathepsin E is up-regulated in macrophages, which is accompanied by the enhanced maturation and secretion of the enzyme. Conversely, cathepsin E is down-regulated by treatment with IL-4 and IL-10.