The identification of a new role for LEKTI in the skin: The use of protein 'bait' arrays to detect defective trafficking of dermcidin in the skin of patients with Netherton syndrome

Abstract

Lympho-Epithelial Kazal-Type-related Inhibitor (LEKTI) has been demonstrated to be an inhibitor of various kallikreins and is thought to play a role in the regulation of skin desquamation. In order to identify and investigate the potential of LEKTI to interact with other proteins, a method was developed using immobilised proteins onto arrays and nanoUPLC/MALDI-TOF MS. Using various domains of LEKTI, we demonstrated that these domains bound a number of kallikreins (5, 13 and 14) to varied extents on the array surface. Inhibitory assays confirmed that binding on the protein array surface corresponded directly to levels of inhibition. The method was then tested using skin epidermal extracts. All forms of rLEKTI with the exception of rLEKTI 12-15, demonstrated the binding of several potential candidate proteins. Surprisingly, the major binding partners of LEKTI were found to be the antimicrobial peptide dermcidin and the serine protease cathepsin G and no kallikreins. Using confocal microscopy and Netherton syndrome skin sections, we confirmed the co-localisation of LEKTI with dermcidin and demonstrated altered trafficking of dermcidin in these patients. This potential new role for LEKTI as a multifunctional protein in the protection and transport of proteins in the epidermis and its role in disease are discussed.