Keratin cytoskeletal proteins are crucial for the maintenance of skin integrity. Mutations in genes coding for K5 and K14 cause the human skin disorder epidermolysis bullosa simplex (EBS) leading to substantial alterations in keratin assembly and collapse of keratin filaments into cytoplasmic protein aggregates. The phenotypic consequences of K5 and K14 mutations comprise fragility of basal keratinocytes and skin blistering upon mild mechanical trauma. Treatment of EBS is only supportive and consists primarily of wound care and avoidance of mechanical stress. Besides symptomatic care, no efficient therapeutic treatment is available for EBS. 
In the present study, we used patient-derived keratinocytes carrying the most frequent K14.R125C mutation as a reproducible EBS model to understand EBS pathomechanisms and to develop a therapy approach aimed to restore a functional keratin network. Numerous post-translational modifications (PTMs) such as phosphorylation have been reported to occur on keratins, which affect the organization of keratin networks. Whether keratin mutations affect the occurrence of PTMs and thereby keratin aggregation in EBS is yet unknown. We find that the K14.R125C mutation alters keratin PTMs in distinct ways and suggest that disease mutations and altered PTMs aggravate keratin aggregation. We reason that chemical compounds affecting the interplay of mutations and PTMs enable the reformation of a keratin cytoskeleton from aggregates are potential candidates for combating EBS. To that end, we performed an image-based, high-throughput screen with K14.R125C keratinocytes, making use of ~5.000 bioactive, repurposed compounds. As readout, a reduction in the number of keratin aggregates/cell was employed. Results from the screen and their significance for keratin regulation and EBS therapy approaches will be presented at the meeting.

A compound-based therapy approach for Epidermolysis Bullosa Simplex