title: DNA accelerates the inhibition of human cathepsin V by serpins.
abstract: A balance between proteolytic activity and protease inhibition is crucial to the appropriate function 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 cofactors fine tuning serpin activity in the extracellular milieu 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 cathepsin V and human cathepsin 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 50-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 occlusion of the active site rather than the substrate-like behavior 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.
authors.affiliation: Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Poh Chee
authors.initials: PC
authors.lastname: Ong
authors.forename: Sheena
authors.initials: S
authors.lastname: McGowan
authors.forename: Mary C
authors.initials: MC
authors.lastname: Pearce
authors.forename: James A
authors.initials: JA
authors.lastname: Irving
authors.forename: Wan-Ting
authors.initials: WT
authors.lastname: Kan
authors.forename: Sergei A
authors.initials: SA
authors.lastname: Grigoryev
authors.forename: Boris
authors.initials: B
authors.lastname: Turk
authors.forename: Gary A
authors.initials: GA
authors.lastname: Silverman
authors.forename: Klaudia
authors.initials: K
authors.lastname: Brix
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Bottomley
authors.forename: James C
authors.initials: JC
authors.lastname: Whisstock
authors.forename: Robert N
authors.initials: RN
authors.lastname: Pike
mesh_terms: D000951:Antigens, Neoplasm / Q000737:chemistry* / Q000378:metabolism; D056668:Cathepsin L; D002403:Cathepsins / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000378:metabolism; D003067:Coenzymes / Q000737:chemistry* / Q000378:metabolism; D055312:Cystatin A; D015891:Cystatins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000378:metabolism; D004247:DNA / Q000737:chemistry*; D006801:Humans; D011485:Protein Binding / Q000502:physiology; D011487:Protein Conformation; D015843:Serpins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D000951:Antigens, Neoplasm; D003067:Coenzymes; D055312:Cystatin A; D015891:Cystatins; D015843:Serpins; C051072:squamous cell carcinoma-related antigen; C026407:CSTA protein, human; D004247:DNA; D002403:Cathepsins; D003546:Cysteine Endopeptidases; C534281:CTSL protein, human; D056668:Cathepsin L; C117627:CTSV protein, human