Cathepsin S Cannibalism of Cathepsin K as a Mechanism to Reduce Type I Collagen Degradation

• Type of Material: Article
• Authors: Manu Platt, Emory University; Zachary T. Barry, Emory University
• Language: English
• Date: 2012-08-10
• Publisher: American Society for Biochemistry and Molecular Biology
• Publication Version: Final Published Version
• Copyright Statement: © 2012 by The American Society for Biochemistry and Molecular Biology, Inc.
• Final Published Version (URL): http://dx.doi.org/10.1074/jbc.M111.332684
• Title of Journal or Parent Work: Journal of Biological Chemistry
• ISSN: 0021-9258
• Volume: 287
• Issue: 33
• Start Page: 27723
• End Page: 27730
• Grant/Funding Information: This work was also supported by the Georgia Cancer Coalition, Georgia Institute of Technology startup funds, and the National Science Foundation through Science and Technology Center Emergent Behaviors of Integrated Cellular Systems (EBICS) Grant CBET-0939511.; This work was supported, in whole or in part, by National Institutes of Health New Innovator Grant 1DP2OD007433-01 and by Award DP2OD007433 from the Office of the Director, National Institutes of Health.
• Keywords: HUMAN ATHEROSCLEROSIS; PROTEINASES; INHIBITION; Life Sciences & Biomedicine; DEFICIENT MICE; SPLEEN; CYSTEINE PROTEASES; SHEAR-STRESS; Science & Technology; EXPRESSION; ENDOTHELIAL-CELLS; Biochemistry & Molecular Biology; PROGRESSION
• Research Categories: Chemistry, Biochemistry; Biology, Molecular

Abstract

Cathepsins S and K are potent mammalian proteases secreted into the extracellular space and have been implicated in elastin and collagen degradation in diseases such as atherosclerosis and osteoporosis. Studies of individual cathepsins hydrolyzing elastin or collagen have provided insight into their binding and kinetics, but cooperative or synergistic activity between cathepsinsKand S is less described. Using fluorogenic substrate assays, Western blotting, cathepsin zymography, and computational analyses, we uncovered cathepsin cannibalism, a novel mechanism by which cathepsins degrade each other as well as the substrate, with cathepsin S predominantly degrading cathepsin K. As a consequence of these proteolytic interactions, a reduction in total hydrolysis of elastin and type I collagen was measured compared with computationally predicted values derived from individual cathepsin assays. Furthermore, type I collagen was preserved from hydrolysis when a 10-fold ratio of cathepsin S cannibalized the highly collagenolytic cathepsin K, preventing its activity. Elastin was not preserved due to strong elastinolytic ability of both enzymes. Together, these results provide new insight into the combined proteolytic activities of cathepsins toward substrates and each other and present kinetic models to consider for more accurate predictions and descriptions of these systems.