Profiling cysteine protease activity in atopic dermatitis

Recent findings have highlighted the importance of many proteases in maintaining epidermal barrier function. Increased expression of proteases is known to contribute to the pathophysiology of atopic dermatitis (AD). Proteases such as cathepsins X, B, S, and legumain are important in biological functions, such as inflammation, antigen presentation, apoptosis, and degradation of the extracellular matrix. Protease expression does not always correlate with proteolytic activity. While several studies have measured the total expression of these enzymes in AD, their activity has not been carefully assessed. The aim of this study is to characterise the levels of protease activity in AD. Participants with AD (n = 7) and controls (n = 10) have been identified at the Dermatology Outpatient Clinic, RMH. The activity of cysteine proteases were elucidated using activity-based probes (ABPs), which are novel biochemical tools used to measure the activity of specific proteases. Activity of cathepsins X, B, and S were analysed with BMV109, and legumain with LE28. ABP binding was detected by in-gel fluorescence, and total expression was assessed by subsequent western blotting. Preliminary results suggest that the proteolytic activity of cathepsin X (p = 0.02) and cathepsin B (p = 0.004) is significantly increased in skin affected by AD as compared to control. Cathepsin S and legumain also trended towards an increase, however, were not statistically different (p = 0.07 and 0.12, respectively). Our preliminary data suggest that the activity of cathepsins X and B might have utility as a biomarker to aid in the diagnosis of AD.

Miss Sonet Chap

Royal Brisbane and Womens Hospital

Dr Sonet Chap is currently doing her medical internship at the Royal Brisbane and Women's Hospital after graduating with a Doctor of Medicine from the University of Melbourne in 2016. Her interest in Dermatology developed during her research as part of her medical degree. In 2016, she undertook research at the Department of Dermatology, Royal Melbourne Hospital and laboratory-based work at the Drug Discovery Biology Laboratory, Monash Institute Pharmaceutical Sciences.