Chemical probe and C-terminomics profiling point to cathepsin B as a dipeptidyl carboxypeptidase in macrophage cells
- An irreversible acyloxymethyl ketone inhibitor was used in mouse macrophage cells to probe cathepsin B activity, and it also shifted activity of related cysteine cathepsins and altered cathepsin S maturation.
- Global protein levels and N-terminal processing changed little, whereas C-terminal profiling showed cleavages clustered a few residues from native C-termini, supporting a dipeptidyl carboxypeptidase role.
- A BODIPY-labelled version of the inhibitor selectively tags active cathepsin B in lysates and live cells, showing mainly lysosomal localization.
💡 Points Based on the abstract
An AOMK that also shifts other cysteine cathepsins is a reminder that this warhead class is not cathepsin B-specific, so the phenotypes are hard to pin on CatB alone. A matched non-covalent or selective inhibitor, or CatB-knockout cells run through the same C-terminomics workflow, would be the clean control. The BODIPY probe is more useful if its S2/S1' selectivity is profiled against CatL and CatS.