Cathepsin G Inhibitor I

IC50: 53 nM

Cathepsin G (EC 3.4.21.20, chymotrypsin-like proteinase, neutral proteinase) is an enzymatic protein belonging to the peptidase or protease families. In humans, it is coded by the CTSG gene. Cathepsin G Inhibitor I is a potent, selective, reversible, competitive, non-peptide inhibitor of cathepsin G.

In vitro: Cathepsin G Inhibitor I shows reversible, competitive inhibition with IC50 and Ki values of 53 ± 12 (N = 10) and 63 ± 14 nM (N = 5), respectively. Another attribute of Cathepsin G Inhibitor I relates to its selectivity vs other serine proteases. It weakly inhibits chymotrypsin (Ki = 1.5 ± 0.2 μM), and poorly inhibits (<50% inhibition at 100 μM) thrombin, factor Xa, factor IXa, plasmin, trypsin, tryptase, proteinase 3, and human leukocyte elastase [1].

In vivo: Cathepsin G Inhibitor I is currently in in-vitro investigation and no animal in vivo study is ongoing [1].

Clinical trial: Cathepsin G Inhibitor I is currently in the preclinical development and no clinical trial is ongoing.

Reference:
[1] Greco MN, Hawkins MJ, Powell ET, Almond HR Jr, Corcoran TW, de Garavilla L, Kauffman JA, Recacha R, Chattopadhyay D, Andrade-Gordon P, Maryanoff BE.  Nonpeptide inhibitors of cathepsin G: optimization of a novel beta-ketophosphonic acid lead by structure-based drug design. J Am Chem Soc. 2002;124(15):3810-1.

Using a Caesalpinia echinata Lam. protease inhibitor as a tool for studying the roles of neutrophil elastase, cathepsin G and proteinase 3 in pulmonary edema.[Pubmed:24140156]

Phytochemistry. 2013 Dec;96:235-43.

Acute lung injury (ALI) is characterized by neutrophil infiltration and the release of proteases, mainly elastase (NE), cathepsin G (Cat G) and proteinase 3 (PR3), which can be controlled by specific endogenous inhibitors. However, inhibitors of these proteases have been isolated from different sources, including plants. For this study, CeEI, or Caesalpinia echinata elastase inhibitor, was purified from C. echinata (Brazil-wood) seeds after acetone fractionation, followed by ion exchange and reversed phase chromatographic steps. Characterization with SDS-PAGE, stability assays, amino acid sequencing and alignment with other protein sequences confirmed that CeEI is a member of the soybean Kunitz trypsin inhibitor family. Like other members of this family, CeEI is a 20 kDa monomeric protein; it is stable within a large pH and temperature range, with four cysteine residues forming two disulfide bridges, conserved amino acid residues and leucine-isoleucine residues in the reactive site. CeEI was able to inhibit NE and Cat G at a nanomolar range (with K(i)s of 1.9 and 3.6 nM, respectively) and inhibited PR3 within a micromolar range (K(i) 3.7 muM), leading to hydrolysis of specific synthetic substrates. In a lung edema model, CeEI reduced the lung weight and pulmonary artery pressure until 180 min after the injection of zymosan-activated polymorphonuclear neutrophils. In experiments performed in the presence of a Cat G and PR3, but not an NE inhibitor, lung edema was reduced only until 150 min and pulmonary artery pressure was similar to that of the control. These results confirm that NE action is crucial to edema establishment and progression. Additionally, CeEI appears to be a useful tool for studying the physiology of pulmonary edema and provides a template for molecular engineering and drug design for ALI therapy.

Design of Potent and Selective Cathepsin G Inhibitors Based on the Sunflower Trypsin Inhibitor-1 Scaffold.[Pubmed:28045523]

J Med Chem. 2017 Jan 26;60(2):658-667.

Neutrophils are directly responsible for destroying invading pathogens via reactive oxygen species, antimicrobial peptides, and neutrophil serine proteases (NSPs). Imbalance between NSP activity and endogenous protease inhibitors is associated with chronic inflammatory disorders, and engineered inhibitors of NSPs are a potential therapeutic pathway. In this study we characterized the extended substrate specificity (P4-P1) of the NSP cathepsin G using a peptide substrate library. Substituting preferred cathepsin G substrate sequences into sunflower trypsin inhibitor-1 (SFTI-1) produced a potent cathepsin G inhibitor (Ki = 0.89 nM). Cathepsin G's P2' preference was determined by screening against a P2' diverse SFTI-based library, and the most preferred residue at P2' was combined in SFTI-1 with a preferred substrate sequence (P4-P2) and a nonproteinogenic P1 residue (4-guanidyl-l-phenylalanine) to produce a potent (Ki = 1.6 nM) and the most selective (>/=360-fold) engineered cathepsin G inhibitor reported to date. This compound is a promising lead for further development of cathepsin G inhibitors targeting chronic inflammatory disorders.

DNA structures decorated with cathepsin G/secretory leukocyte proteinase inhibitor stimulate IFNI production by plasmacytoid dendritic cells.[Pubmed:23885335]

Am J Clin Exp Immunol. 2013 Jun 15;2(2):186-94. Print 2013.

Plasmacytoid dendritic cells (pDCs) and neutrophils are detected in psoriatic skin lesions and implicated in the pathogenesis of psoriasis. pDCs specialize in the production of type I interferon (IFNI), a cytokine that plays an important role in chronic autoimmune-like inflammation, including psoriasis. Here, we demonstrate that IFNI production in pDCs is stimulated by DNA structures containing the neutrophil serine protease cathepsin G (CatG) and the secretory leukocyte protease inhibitor (SLPI), which is a controlling inhibitor of serine proteases. We also demonstrate the presence of neutrophil-derived DNA structures containing CatG and SLPI in lesional skin samples from psoriasis patients. These findings suggest a previously unappreciated role for CatG in psoriasis by linking CatG and its inhibitor SLPI to the IFNI-dependent regulation of immune responses by pDCs in psoriatic skin.

Determination of cathepsin G in endometrial tissue using a surface plasmon resonance imaging biosensor with tailored phosphonic inhibitor.[Pubmed:25218550]

Eur J Obstet Gynecol Reprod Biol. 2014 Nov;182:38-42.

OBJECTIVE: Cathepsin G is a serine peptidase whose physiological role is mainly associated with an early immune response, anti-microbial activity as well as platelet activation or hydrolysis of coagulation factors. In addition, since the activity of cathepsin G has been associated with the development of various pathological disorders, the measurement of its activity in patient samples is of high interest. Unfortunately, the usefulness of common immunological methods is limited, since they cannot distinguish between catalytically active and inactive protease. STUDY DESIGN: Here we present the application of recently developed Surface Plasmon Resonance-based biosensor for the detection of active cathepsin G in human endometrium samples. The key element of the system is based on the irreversible binding of cathepsin G to its specific phosphonic-type inhibitor immobilized on the surface of the gold chip. The concentration of cathepsin G was measured in tissue samples from the group of patients with endometriosis as well as in the control group. RESULTS: The level of cathepsin G ascertained in endometrium tissue samples was over twice as high for the group of patients suffering from endometriosis as compared to the control group, with the median values of 0.5 pmol/mg and 0.2 pmol/mg, respectively. CONCLUSION: The SPR sensor armed with a specific irreversible phosphonic inhibitor represents a highly useful tool for the determination of catalytically active cathepsin G concentration in endometrial tissue.