Elastase 2 is expressed in human and mouse epidermis and impairs skin barrier function in Netherton syndrome through filaggrin and lipid misprocessing
Chrystelle Bonnart, … , Bernard Monsarrat, Alain Hovnanian
Chrystelle Bonnart, … , Bernard Monsarrat, Alain Hovnanian
Published February 22, 2010
Citation Information: J Clin Invest. 2010;120(3):871-882. https://doi.org/10.1172/JCI41440.
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Research Article Dermatology

Elastase 2 is expressed in human and mouse epidermis and impairs skin barrier function in Netherton syndrome through filaggrin and lipid misprocessing

Abstract

The human epidermis serves 2 crucial barrier functions: it protects against water loss and prevents penetration of infectious agents and allergens. The physiology of the epidermis is maintained by a balance of protease and antiprotease activities, as illustrated by the rare genetic skin disease Netherton syndrome (NS), in which impaired inhibition of serine proteases causes severe skin erythema and scaling. Here, utilizing mass spectrometry, we have identified elastase 2 (ELA2), which we believe to be a new epidermal protease that is specifically expressed in the most differentiated layer of living human and mouse epidermis. ELA2 localized to keratohyalin granules, where it was found to directly participate in (pro-)filaggrin processing. Consistent with the observation that ELA2 was hyperactive in skin from NS patients, transgenic mice overexpressing ELA2 in the granular layer of the epidermis displayed abnormal (pro-)filaggrin processing and impaired lipid lamellae structure, which are both observed in NS patients. These anomalies led to dehydration, implicating ELA2 in the skin barrier defect seen in NS patients. Thus, our work identifies ELA2 as a major new epidermal protease involved in essential pathways for skin barrier function. These results highlight the importance of the control of epidermal protease activity in skin homeostasis and designate ELA2 as a major protease driving the pathogenesis of NS.

Authors

Chrystelle Bonnart, Céline Deraison, Matthieu Lacroix, Yoshikazu Uchida, Céline Besson, Aurélie Robin, Anaïs Briot, Marie Gonthier, Laurence Lamant, Pierre Dubus, Bernard Monsarrat, Alain Hovnanian

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Figure 1

Identification and characterization of ELA2, a new epidermal protease.

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Identification and characterization of ELA2, a new epidermal protease. (...
(A) Sequence of murine Ela2 precursor. The peptides identified by mass spectrometry are shown in bold red, corresponding to 8% sequence coverage. The score of each peptide is indicated. (B) RT-PCR analysis showing ELA2 mRNA expression in murine and human epidermis, but not in dermis. RT-PCR experiments performed from cultured cells with human ELA2 (UTR) primers, showing ELA2 mRNA expression in differentiated human keratinocytes, but not in undifferentiated keratinocytes nor fibroblasts. As a control, the hypoxanthine phosphoribosyl transferase (HPRT) gene was amplified in all samples. Lanes were run on the same gel but were noncontiguous (white lines). (C) Expression of ELA2 by immunohistochemistry on WT and Spink5–/– (KO) mouse skin as well as human healthy and NS skin sections. ELA2 is detected in the granular layer in each sample. The asterisk indicates the loss of ELA2 signal in an area where the granular layer is absent. BL, basal layer; SP, spinous layer. Scale bar: 75 μm. (D) In situ zymography analysis of normal and LEKTI-deficient mouse and human skins. Elastolytic activity is mainly found in the granular layer as well as in the SC of normal and LEKTI-deficient epidermis. The signal intensity is strongly increased and extended to the outermost layers of the spinous layer in LEKTI-deficient epidermis. Activity intensity is indicated in a pseudo-color gradient ranging from 0 (dark) to 255 (white). The dotted line represents the basal membrane of the epidermis. Scale bar: 50 μm.