Cathepsins L and S are not required for activation of dipeptidyl peptidase I (cathepsin C) in mice.

Department of Medicine and Cardiovascular Research Institute, University of California, San Francisco, CA 94143-0111, USA.
Biological Chemistry (Impact Factor: 2.69). 09/2006; 387(8):1143-6. DOI: 10.1515/BC.2006.141
Source: PubMed

ABSTRACT The cysteine protease dipeptidyl peptidase I (DPPI) activates granule-associated immune-cell serine proteases. The in vivo activator of DPPI itself is unknown; however, cathepsins L and S are candidates because they activate pro-DPPI in vitro. In this study, we tested whether cathepsins L and S activate pro-DPPI in vivo by characterizing DPPI activity and processing in cells lacking cathepsins L and S. DPPI activity, and the relative size and amounts of DPPI heavy and light chains, were identical in mast cells from wild-type and cathepsin L/S double-null mice. Furthermore, the activity of DPPI-dependent chymase was preserved in tissues of cathepsin L/S double-null mice. These results show that neither cathepsin L nor S is required for activation of DPPI and suggest that one or more additional proteases is responsible.

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