Selective Inhibition of the Collagenase Activity of Cathepsin K

Abstract

Cathepsin K, the main bone degrading protease, and chondroitin 4-sulfate (C4-S) form a complex with enhanced collagenase activity. In this report, we demonstrate the specific inhibition of the collagenase activity of cathepsin K by negatively charged polymers without affecting the overall proteolytic activity of the protease. Three different mechanisms to interfere with cathepsin-catalyzed collagen degradation are discussed: 1) inhibition of the formation of the cathepsin K/C4-S complex, 2) inhibition of the attachment of C4-S to collagen, and 3) masking of the collagenase cleavage sites in collagen. By targeting these interaction sites, collagen degradation can be modulated while the non-collagenolytic activities of cathepsin K remain intact. The main inhibitory effect on collagen degradation is due to the impeding effect on the active cathepsin K/C4-S complex. Essential structural elements in the inhibitor molecules are negative charges which compete with the sulfate groups of C4-S in the cathepsin K/C4-S complex. The inhibitory effect can be controlled by length and charge of the polymers. Longer negatively charged polymers (e.g. polyglutamates, oligonucleotides) tend to inhibit all three mechanisms, whereas shorter ones preferentially affect the cathepsin K/C4-S complex.An imbalance between bone formation and resorption can cause various bone diseases such as osteoporosis, certain forms of arthritis, and Paget disease. Type I collagen represents an essential part (90%) of the organic bone mass (1). It has been shown that cathepsin K, a cysteine protease predominantly expressed in osteoclasts (2-4), is an efficient collagenase that cleaves type I collagen at multiple sites in its helical domain (5, 6). Based on the physiological role of cathepsin K in bone resorption, cathepsin K inhibitors are being developed for the treatment of osteoporosis (7). Those inhibitors may also serve as drugs for rheumatoid arthritis (8). Presently, conventional cathepsin K inhibitors target the active site, thus causing a complete inhibition of enzymatic activity. An active site inhibition is associated with the loss of other physiological functions of cathepsin K activity which may result in undesirable side effects. Ablation of the matrix-degrading function in tandem with preservation of its non-collagenolytic protease activity would be greatly advantageous and will be addressed in this report.Collagen consists of three intertwining ␣-chains of ϳ1000 residues each (9). The three-dimensional structures of triplehelical collagen and cathepsin K suggest that the active cleft of cathepsin K does not provide sufficient space to accommodate intact triple-helical collagen. The entrance to the catalytic site of cathepsin K is only 5 Å wide (10), while triple-helical collagen has a diameter of 15 Å. This leads to the assumption that prior to hydrolysis by cathepsin K, the triple-helical collagen has to be unwound to expose its single chains. It was recently demonstrated that bone-and cartilage-resident glycosaminoglycans such as chondr...

Excessive activity of cathepsin K is associated with cartilage defects in a zebrafish model of mucolipidosis II

“…Because cathepsin K is a very potent collagenase with the ability to cleave triple-helical collagens at multiple sites (Kafienah et al, 1998; Lecaille et al, 2003; Selent et al, 2007), it is likely that this activity is needed during discrete developmental time points to assist in the degradation and turnover of collagens, which are continually replaced and remodeled during embryonic development (Goldring et al, 2006). Our results indicate that multiple cell types, including craniofacial chondrocytes, express and/or secrete cathepsin K in the early stages of development in zebrafish embryos.…”

Structural basis of collagen fiber degradation by cathepsin K

“…The purification of GAGs followed the procedure previously described in ref. 39. Details about the enzymatic assays are detailed in SI Materials and Methods.…”

Current aspects of the role of glycosaminoglycans of the extracellular matrix in the development of generalized periodontitis and the course of repair processes

“…The enzymes of beta-glucuronidase, hyaluronidase, beta-N-acetylhexosaminidase and chondroitin sulfatase are actively involved in the cleavage of acid GAGs and glycoproteins of the intercellular substance, periodontal cell membranes, and thus cause the destruction of circular ligament and periodontal tissues in general (McCulloch, 1994;Shyrobokov et al 2003) [29,37]. The degradation of the components of extracellular matrix and the destruction of the [36,40]. У по-єднанні з набряком тканини (сГАГ зв'язують багато води), ці фактори сприяють локалі-зації запалення, перешкоджають його пе-реходу на навколишні тканини, формують своєрідний бар'єр на шляху поширення ін-фекційного процесу (Taylor and Gallo, 2006) [44].…”

“…The infl ammation phase includes swelling of the tissue, extravasation of blood cells and, as a consequence, formation of a blood clot. It is at this instant of the primary damage to the tissue in the extracellular matrix that sGAGs, fi bronectin, cross-linked forms of fi brin, vitronectin, thrombospondin and infl ammatory mediators begin to be determined in a free form (Selent and Kaleta, 2007;Sugahara and Kitagawa, 2002) [36,40]. Combined with tissue swelling (sGAGs bind much water), these factors contribute to the localization of infl ammation, impede its transition to surrounding tissues, and form a peculiar barrier on the way of the infectious process extension (Taylor and Gallo, 2006) [44].…”