# Remodeling of the cell membrane-associated protein pool affects adhesive membrane properties in filaggrin insufficient keratinocytes and impacts distinct cellular and organellar functions

## TL;DR

This study shows that reduced filaggrin in skin cells changes membrane properties, affecting cell adhesion and communication, which may contribute to atopic dermatitis.

## Contribution

The study reveals novel membrane remodeling effects of filaggrin insufficiency on keratinocyte adhesion and extracellular vesicle function.

## Key findings

- Filaggrin insufficiency alters membrane refractive index and protein composition in keratinocytes.
- Anti-adhesive proteins associate with extracellular vesicles, reducing their uptake by dendritic cells.
- Increased keratinocyte adhesiveness and faster wound healing are observed in filaggrin-deficient cells.

## Abstract

Atopic dermatitis (AD) is a highly prevalent inflammatory skin disease, affecting up to 30% of children at some point in their life and frequently persisting into adulthood. Insufficiency in the late epidermal protein filaggrin is frequently observed in the lesional skin of patients, with direct and indirect impact on the skin barrier quality and function. We hypothesized that filaggrin reduction influences intracellular, surface, and derived extracellular membranes of keratinocytes with multiple impacts on the cell function.

Using filaggrin knockdown keratinocytes generated by shRNA interference (shFLG), we determined that the physical characteristics of the cellular membranes (reported by refractive index) are changed on a filaggrin insufficiency background. Using proteomics, protein binding modeling, and functional assays, we established that filaggrin insufficiency in keratinocytes results in changes in both organelles comprised of internal cellular membranes (i.e., small extracellular vesicles, sEVs) and the plasma membrane. We detected increased association of anti-adhesive proteins (tenascin-C and matrilin-2) with sEVs, resulting in a reduction of the fibronectin-1-mediated sEV uptake by dendritic cell subsets. At the same time, dysregulation of the tight junction and cell adhesion molecules at the level of the cell increased keratinocyte adhesiveness to reconstituted basement membrane substratum as well as faster gap closure in the wound healing assay. We also independently confirmed the findings on sEV uptake and wound healing in filaggrin knockout N/TERT-2G keratinocytes, which more closely resemble primary cells.

We conclude that the alterations in different membrane compartments in filaggrin insufficiency are reflected in changes in keratinocyte functions of relevance to AD pathology, and strategies to target those could open up new therapeutic approaches.

The online version contains supplementary material available at 10.1186/s12915-025-02499-y.