Cathepsin S: therapeutic, diagnostic, and prognostic potential

Cathepsin S is a member of the cysteine Cathepsin protease family. It is a lysosomal protease which can promote degradation of damaged or unwanted proteins in the endo-lysosomal pathway. Additionally, it has more specific roles such as MHC class II antigen presentation, where it is important in the degradation of the invariant chain. Unsurprisingly, mis-regulation has implicated Cathepsin S in a variety of pathological processes including arthritis, Cancer, and Cardiovascular Disease, where it becomes secreted and can act on extracellular substrates. In comparison to many other cysteine Cathepsin family members, Cathepsin S has uniquely restricted tissue expression and is more stable at a neutral pH, which supports its involvement and importance in localised disease microenvironments. In this review, we examine the known involvement of Cathepsin S in disease, particularly with respect to recent work indicating its role in mediating pain, diabetes, and cystic fibrosis. We provide an overview of current literature with regards Cathepsin S as a therapeutic target, as well as its role and potential as a predictive diagnostic and/or prognostic marker in these diseases.