Evidence that filaggrin is a component of cornified cell envelopes in human plantar epidermis.
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ABSTRACT:
SUBMITTER: Simon M
PROVIDER: S-EPMC1217460 | biostudies-other | 1996 Jul
REPOSITORIES: biostudies-other
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Project description:Filaggrin-2 (FLG2), a member of the S100-fused type protein family, is a 250 kDa protein mainly expressed in differentiated keratinocytes of the epidermis (Wu et al., 2009; Hsu et al., 2011). Its expression is reduced in atopic dermatitis (Pellerin et al., 2013), and heterozygous non-sense mutations of its gene are associated with a more persistent form of the disease in Afro-American populations (Margolis et al., 2014). Homozygous mutations of its gene are responsible for a rare skin disease called peeling skin syndrome type A (Bolling et al., 2018; Mohamad et al., 2018). However, the exact role of FLG2, a multi-domain protein, is not well known. Its COOH-tail exhibits anti-microbial activity (Hansmann et al., 2015), whereas its B domain is suspected to be involved in the hydration of the upper part of the epidermis, the cornified layer. Here, on the basis of immunological, global proteomics and in vitro enzymatic analysis we demonstrated that its amino-terminal domain is cross-linked to the cornified envelope, a pericellular resistant structure that replaces the plasma membrane during the last step of keratinocyte differentiation. In addition, depletion of FLG2 in reconstructed 3D human epidermis induced a marked fragility of cornified envelopes. These data suggest that FLG2 is important for proper mechanical strength of the cornified layer. They may explain the epidermal fragility observed in peeling skin syndrome type A patients.
2019-02-25 | PXD011833 | Pride
Project description:Atopic dermatitis is a chronic inflammatory skin disease with defects in the epidermal barrier. In a cohort of African-American children, a FLG2 nonsense mutation has been associated with the disease. In the epidermis of European patients, the expression of filaggrin-2, the filaggrin-related protein encoded by FLG2, is decreased. To describe the function of filaggrin-2 and evaluate the impact of its deficiency, its expression was downregulated using lentivirus-mediated shRNA interference in a three-dimensional reconstructed human epidermis (RHE) model. This resulted in parakeratosis and a compact stratum corneum, presence of abnormal vesicles inside the corneocytes, increased pH and reduced amounts of free amino acids at the RHE surface, leading to increased sensitivity to UVB radiations. The expression of differentiation markers was slightly modified. However, we observed reduced proteolytic processing of corneodesmosin, hornerin and filaggrin in parallel with reduced amounts of caspase-14 and bleomycin hydrolase. Our data demonstrated that filaggrin-2 is important for a proper cornification and a functional stratum corneum. Its downregulation in atopic patients may be involved in the disease-associated epidermis impairment.
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Project description:A substrate of transglutaminase, specific to the epidermis, was identified, by fluorescent and radioactive labelling with the lysine analogues dansylcadaverine and [14C]putrescine respectively, in newborn-rat epidermal homogenates and whole-skin organ cultures. The labelled analogues were preferentially incorporated into the stratum-corneum protein filaggrin in a Ca2+-dependent manner in both 'in vitro' systems. When filaggrin was labelled in vivo with [3H]histidine and then incubated with rat epidermal preparations, the label was rendered SDS/thiol-insoluble. Incorporation of [3H]filaggrin into the insoluble envelope fraction was Ca2+-dependent and inhibited by EDTA and exogenous amines. Antisera to newborn-rat filaggrin cross-reacted with purified newborn-rat cell envelopes, and this reaction was blocked by adsorbing the antiserum with purified filaggrin. Quantification of the 'envelope-bound' filaggrin showed it to be a significant component, accounting for approx. 10% of the cell-envelope protein.
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Project description: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.
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