Cathepsin

Cathepsin (from Greek καθεψειν = digest) refers to a group of endoproteases that are found, for example, in lysosomes of eosinophilic and neutrophilic granulocytes and in osteoclasts. Cathepsins cause a hydrolytic degradation of the extracellular matrix and the basement membrane. Cathepsins are involved in the degradation of cell organelles or collagen-containing bone matrix. Together with two other serine proteases, elastase and hepsin, cathepsin G is found in neutrophil polymorphonuclear leukocytes. These contain specialized sof. azurophilic granules. The expression of cathepsin G is observed in acute and chronic myeloid leukemia.

Cathepsin G is inhibited by the serine protease inhibitor LEKTI (lympho-epithelial Kazal-type inhibitor) which is expressed in the stratum corneum, the stratum granulosum and in the skin appendages. Its reduced epidermal expression (see Netherton syndrome) leads to an increased activity of proteolytic enzymes. The consequence is a defective desmosomal cohesion with a reduction of the skin barrier function.

Cathepsins are probably also involved in angiogenesis in wound healing and invasive tumor growth. They have been shown to be an unfavourable prognosis marker for various tumours (e.g. pancreatic carcinoma).

Cathepsin B is upregulated in the lesional areas of cornification disorders such as keratolytic winter erythema.

A mutation of the gene for cathepsin C (chromosome 11) leads to Papillon-Lefèvre syndrome with palmo-plantar hyperkeratosis, severe periodontitis and consecutive tooth loss. Other mutations in the CTSB gene are associated with a form of chronic pancreatitis.

Antibodies against the protein cathepsin G are found in systemic vasculitides, inflammatory rheumatic diseases or autoimmune diseases such as systemic lupus erythematosus, Sjögren's syndrome or Felty syndrome); further in autoimmune hepatitis and chronic inflammatory bowel diseases. In indirect immunofluorescence on granulocytes, perinuclear (pANCA) or an atypical fluorescence pattern (xANCA) is found.

cathepsin: Greek root "καθεψειν" = digest

1. Hammer C et al (2013) Generalized erythema, scaling and hair anomaly. Dermatologist 64: 516-518
2. Kato A et al (2003) Association of SPINK5 gene polymorphisms with atopic dermatitis in the Japanese population. Br J Dermatol 148: 665-669
3. Mitsudo K et al (2003) Inhibition of serine proteinases plasmin, trypsin, subtilisin A, cathepsin G, and elastase by LEKTI: a kinetic analysis. Biochemistry 42: 3874-3881