title: Proteolytic activation cascade of the Netherton syndrome-defective protein, LEKTI, in the epidermis: implications for skin homeostasis.
abstract: Lympho-epithelial Kazal-type-related inhibitor (LEKTI) is the defective protein of the ichthyosiform condition Netherton syndrome (NS). Strongly expressed in the most differentiated epidermal layers, LEKTI is a serine protease inhibitor synthesized as three different high-molecular-weight precursors, which are rapidly processed into shorter fragments and secreted extracellularly. LEKTI polypeptides interact with several proteases to regulate skin barrier homeostasis as well as inflammatory and/or immunoallergic responses. Here, by combining antibody mapping, N-terminal sequencing, and site-specific mutagenesis, we defined the amino-acid sequence of most of the LEKTI polypeptides physiologically generated in human epidermis. We also identified three processing intermediates not described so far. Hence, a proteolytic cascade model for LEKTI activation is proposed. We then pinpointed the most effective fragments against the desquamation-related kallikreins (KLKs) and we proved that LEKTI is involved in stratum corneum shedding as some of its polypeptides inhibit the KLK-mediated proteolysis of desmoglein-1. Finally, we quantified the individual LEKTI fragments in the uppermost epidermis, showing that the ratios between LEKTI polypeptides and active KLK5 are compatible with a fine-tuned inhibition. These findings are relevant both to the understanding of skin homeostasis regulation and to the design of novel therapeutic strategies for NS.
authors.affiliation: Laboratory of Molecular and Cell Biology, Istituto Dermopatico dell'Immacolata IDI-IRCCS, Rome, Italy. p.fortugno@idi.it
authors.forename: Paola
authors.initials: P
authors.lastname: Fortugno
authors.forename: Alberto
authors.initials: A
authors.lastname: Bresciani
authors.forename: Chantal
authors.initials: C
authors.lastname: Paolini
authors.forename: Chiara
authors.initials: C
authors.lastname: Pazzagli
authors.forename: May
authors.initials: M
authors.lastname: El Hachem
authors.forename: Marina
authors.initials: M
authors.lastname: D'Alessio
authors.forename: Giovanna
authors.initials: G
authors.lastname: Zambruno
mesh_terms: D000595:Amino Acid Sequence; D001706:Biopsy; D016022:Case-Control Studies; D002478:Cells, Cultured; D051183:Desmoglein 1 / Q000378:metabolism; D004817:Epidermis / Q000378:metabolism* / Q000473:pathology; D057809:HEK293 Cells; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D007610:Kallikreins / Q000378:metabolism; D056770:Netherton Syndrome / Q000378:metabolism*; D053491:Proteinase Inhibitory Proteins, Secretory / Q000378:metabolism*; D059748:Proteolysis; D000074163:Serine Peptidase Inhibitor Kazal-Type 5; D012867:Skin / Q000378:metabolism* / Q000473:pathology; D014162:Transfection
chemical_list: D051183:Desmoglein 1; D053491:Proteinase Inhibitory Proteins, Secretory; C120650:SPINK5 protein, human; D000074163:Serine Peptidase Inhibitor Kazal-Type 5; D007610:Kallikreins