A balance between proteolytic activity and protease inhibition is crucial to the correct functioning of many biological processes. There is mounting evidence for the presence of both papain-like cysteine proteases and serpins with a corresponding inhibitory activity in the nucleus. Well-characterized examples of co-factors fine-tuning serpin activity in the extracellular millieu are known, but such modulation has not been studied for protease-serpin interactions within the cell. Accordingly, we present an investigation into the effect of a DNA-rich environment on the interaction between model serpins (MENT and SCCA-1), cysteine proteases (human cathepsins V and L) and cystatin A. DNA was indeed found to accelerate the rate at which MENT inhibited cathepsin V, a human orthologue of mammalian cathepsin L, up to 60-fold, but unexpectedly this effect was primarily effected via the protease, and secondarily by the recruitment of the DNA as a template onto which cathepsin V and MENT are bound. Notably, the protease-mediated effect was found to correspond both with an altered substrate turnover, and a conformational change within the protease. Consistent with this, cystatin inhibition, which relies on the occlusion of the active site rather than substrate-like behaviour of serpins, was unaltered by DNA. This represents the first example of modulation of serpin inhibition of cysteine proteases by a co-factor and reveals a mechanism for differential regulation of cathepsin proteolytic activity in a DNA-rich environment.
|Pages (from-to)||36980 - 36986|
|Number of pages||7|
|Journal||Journal of Biological Chemistry|
|Publication status||Published - 2007|